Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Freshwater Harmful Algal Blooms: Causes,
July 8, 2020
Challenges, and Policy Considerations
Laura Gatz
Scientific research indicates that in recent years, the frequency and geographic
Analyst in Environmental
distribution of harmful algal blooms (HABs) have been increasing nationally and
Policy
globally. Because the impacts of HABs can be severe and widespread—often with

interstate implications—these issues have been a perennial interest for Congress. While
algal communities are natural components of healthy aquatic ecosystems, under certain

conditions (e.g., increased temperatures and nutrient concentrations), algae may grow excessively, or “bloom,”
and produce toxins that can harm human health, animals, aquatic ecosystems, and the economy.
In 2014, a cyanobacterial HAB in Lake Erie affected the drinking water for more than 500,000 people in Toledo,
Ohio. In 2016, a massive HAB in Florida’s Lake Okeechobee negatively impacted tourism and aquatic life. HABs
have been recorded in every state and have become a concern nationwide.
Many types of algae can cause HABs in freshwater systems. The most frequent and severe blooms involve the
proliferation of cyanobacteria. Some cyanobacteria species can produce toxins—cyanotoxins—that can cause
mild to severe health effects in humans and kill aquatic life and other animals.
HABs can also contribute to deteriorating water quality and ecosystem health. As masses of cyanobacteria or
other algae die and decompose, they consume oxygen, sometimes forming “dead zones” where life cannot
survive. These areas can kill fish and organisms, such as crabs and clams, and have detrimental economic effects.
Scientists widely consider nutrient enrichment to be a key cause of HAB formation. While nutrients are essential
to plants and natural parts of aquatic ecosystems, excessive amounts can overstimulate algal growth. Sources
include point sources (e.g., municipal wastewater discharges) and nonpoint sources (e.g., fertilizer runoff from
agricultural and urban areas).
Congress, federal agencies, and states have taken steps to address HABs and nutrients that contribute to their
occurrence. The Harmful Algal Bloom and Hypoxia Research and Control Act of 1998 (HABHRCA), as
amended, established an interagency task force, required the task force to prepare reports and plans addressing
marine and freshwater HABs, and authorized funding for research, education, monitoring activities, etc.
In June 2019, the Environmental Protection Agency (EPA) used its authority under the Clean Water Act (CWA) to
publish final water quality criteria for two algal toxins in waters used for recreational purposes. States may
consider such criteria when developing water quality standards—measures that describe the desired condition or
level of protection of a water body and what is needed for protection. Alternatively, they may use these values as
the basis of swimming advisories for public notification purposes at recreational waters.
Further, EPA has emphasized the need to reduce nutrient pollution from all sources to reduce public health and
environmental impacts associated with HABs. The CWA does not authorize EPA to regulate all sources. It
authorizes EPA to regulate point (direct) sources of nutrients but does not authorize EPA to regulate nonpoint
(diffuse) sources of nutrient pollution.
Some states have developed guidelines for algal toxins, primarily for use in guiding swimming advisories. Also,
states have listed waters as impaired, or not meeting water quality standards, for algal blooms or algal toxins.
Some of these states have begun to develop Total Maximum Daily Loads (TMDLs)—essentially pollution
budgets—to address them. Most states have identified nutrient-related pollution as a priority to be addressed by
their TMDLs and/or alternative restoration plans. States rely heavily on financial assistance from EPA in
implementing these plans and, more broadly, in addressing nonpoint source pollution that leads to degraded water
Congressional Research Service


Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

quality and HAB formation. Congress has long provided financial assistance through EPA for regional, state, and
local programs through CWA Sections 106 and 319 grants, geographic programs (such as the Chesapeake Bay and
Great Lakes), and other sources. The President’s FY2021 budget request proposes to either eliminate or
significantly reduce funding for most of these programs.
Congress continues to show interest in addressing HABs. This interest has largely focused on funding research to
close research gaps identified by scientists and decisionmakers and to coordinate the efforts of federal agencies
and their partners to study and address HABs.

Congressional Research Service

link to page 5 link to page 6 link to page 6 link to page 7 link to page 10 link to page 12 link to page 13 link to page 13 link to page 18 link to page 21 link to page 21 link to page 25 link to page 27 link to page 30 link to page 31 link to page 33 link to page 6 link to page 13 link to page 13 link to page 9 link to page 9 link to page 11 link to page 15 link to page 19 link to page 20 link to page 21 link to page 21 link to page 25 link to page 29 link to page 29 link to page 29 link to page 34 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Contents
Introduction ..................................................................................................................................... 1
Background ..................................................................................................................................... 2
What Are Harmful Algal Blooms? ............................................................................................ 2
HAB Types and Impacts ..................................................................................................... 3
Factors Contributing to HAB Formation ............................................................................ 6
Incidence and Trends ................................................................................................................. 8
Efforts to Address Harmful Algal Blooms ...................................................................................... 9
Enacted Legislation ................................................................................................................... 9
Federal Agency Efforts............................................................................................................ 14
Regulatory Efforts and Guidelines .......................................................................................... 17
HABs, Cyanobacteria, and Cyanotoxins........................................................................... 17
Nutrient Management ....................................................................................................... 21
Federal Funding ...................................................................................................................... 23
Research Gaps ............................................................................................................................... 26
Legislation in the 116th Congress .................................................................................................. 27
Conclusion ..................................................................................................................................... 29

Figures
Figure 1. Aerial View of a July 2016 Harmful Algal Bloom in Lake Okeechobee, Florida........... 2
Figure 2. Generalized Distribution of Selected Freshwater Harmful Algal Blooms
(HABs) in the United States ......................................................................................................... 9

Tables
Table 1. Selected Freshwater Harmful Algal Bloom (HAB) Taxa and Toxins and Their
Effects ........................................................................................................................................... 5
Table 2. Anthropogenic Sources of Nutrients in Water ................................................................... 7
Table 3. Selected Freshwater Harmful Algal Bloom (HAB)-Related Acts .................................... 11
Table 4. Interagency Task Force on Harmful Algal Blooms (HABs) and Hypoxia ...................... 15
Table 5. EPA Efforts to Coordinate Freshwater HAB-Related Activities...................................... 16
Table 6. Summary of EPA, WHO, and State Guidelines for Cyanotoxins in Recreational
Waters ......................................................................................................................................... 17
Table 7. State Algal Bloom and Algal Toxin Impaired Waters Listings and TMDLs ................... 21
Table 8. FY2016-FY2020 Enacted Appropriations and FY2021 Requested for Selected
EPA Grants and Programs That Include Assistance to Address Nonpoint Source
Pollution ..................................................................................................................................... 25


Contacts
Author Information ........................................................................................................................ 30

Congressional Research Service

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Introduction
Scientific research indicates that in recent years, the frequency and geographic distribution of
harmful algal blooms (HABs) have been increasing nationally and globally.1 HABs can be
detrimental to human health, animals, aquatic ecosystems, and local economies. For example:
 In 2014, a major HAB in Lake Erie caused the City of Toledo, Ohio, to issue a
“do not drink” order for tap water that left more than 500,000 people without
drinking water for two days and had an estimated impact of $65 million in lost
benefits.2
 In the summer of 2016, a massive HAB in Lake Okeechobee—Florida’s largest
freshwater lake—resulted in beach closures, losses to the tourism industry, and
negative impacts on marine life.
 According to the U.S. Environmental Protection Agency (EPA), between June 2
and August 1, 2017, states reported at least 281 notices for freshwater HABs,
including cautions, warnings, public health advisories, and public health
warnings.3
 In 2018, the City of Salem, Oregon, issued a drinking water advisory for
vulnerable populations following the detection of algal toxins in the drinking
water supply.4
Congress, many federal agencies, states, localities, and other partners have taken and continue to
take steps to address the rising trend in HABs and their impacts. However, there are many gaps in
current scientific understanding of HABs among the research and management communities and
considerable debate as to how best to address the issue from a regulatory standpoint. This report
explores these issues as they pertain to HABs in freshwater systems. Specifically, it addresses the
conditions and activities that contribute to the occurrence of freshwater HABs; steps that
Congress, federal agencies—particularly EPA—and their partners are taking to address and
mitigate their occurrence; and the current knowledge gaps on this issue. This report is focused on
freshwater HABs, not marine or coastal HABs or issues associated with HABs in drinking water

1 NOAA, State of the Science Fact Sheet—Harmful Algal Blooms, September 2016, http://nrc.noaa.gov/
CouncilProducts/ScienceFactSheets.aspx; U.S. Environmental Protection Agency, “Causes of CyanoHABs,”
https://www.epa.gov/cyanohabs/causes-cyanohabs; U.S. National Office for Harmful Algal Blooms at Woods Hole
Oceanographic Institution, “Recent Trends: National Changes,” https://hab.whoi.edu/maps/regions-us-distribution/
regions-us-recent-trends/. C. B. Lopez et al., Scientific Assessment of Freshwater Harmful Algal Blooms, Interagency
Working Group on Harmful Algal Blooms, Hypoxia, and Human Health of the Joint Subcommittee on Ocean Science
and Technology, 2008.
2 M. Bingham et al., Economic Benefits of Reducing Harmful Algal Blooms in Lake Erie, Environmental Consulting
and Technology, submitted to the International Joint Commission, October 2015.
3 EPA, Recommended Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for
Microcystins and Cylindrospermopsin, EPA 822-R-19-001, May 2019, https://www.epa.gov/sites/production/files/
2019-05/documents/hh-rec-criteria-habs-document-2019.pdf.
4 City of Salem, Oregon, “Salem Continues Drinking Water System Improvements in 2020,” press release, April 23,
2020, https://www.cityofsalem.net/Pages/salem-continues-drinking-water-system-improvements-in-2020.aspx. The
Oregon Health Authority defined vulnerable populations to include infants (particularly those formula-fed), children
younger than six years, people with pre-existing liver conditions, people receiving dialysis treatment, and pregnant
women and nursing mothers.
Congressional Research Service
1

link to page 6
Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

supplies.5 However, some of the discussion is applicable to marine HABs, as many issues and
efforts to address them are cross-cutting.
Background
What Are Harmful Algal Blooms?
Algal communities are naturally occurring components of healthy aquatic ecosystems, such as
lakes, rivers, and estuaries. However, under certain environmental conditions, such as increased
temperatures and nutrient concentrations (e.g., nitrogen and phosphorus), colonies of algae can
grow excessively, or “bloom,” and produce toxins that pose a threat to human and aquatic
ecosystem health and potentially cause economic damage. These HABs sometimes produce
discolorations in the water that can appear as scums, paint-like slicks, clotted mats, or foam that
may vary in color (i.e., light to dark green, yellow, red, or brown). Even when visible signs of a
bloom are absent, however, algal toxins may still cause harmful effects.6 Figure 1 shows an aerial
view of a HAB that produced visible green scums in Lake Okeechobee, Florida, in July 2016.
Figure 1. Aerial View of a July 2016 Harmful Algal Bloom in
Lake Okeechobee, Florida

Source: U.S. Geological Survey, https://www.usgs.gov/news/science-harmful-algae-blooms.

5 For a discussion of algal toxins in drinking water, see, Algal Toxins in Drinking Water: EPA Health Advisories, by
Mary Tiemann.
6 Lopez et al., Scientific Assessment of Freshwater Harmful Algal Blooms.
Congressional Research Service
2

link to page 9 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

HAB Types and Impacts
While many types of algae can cause HABs in bodies of freshwater, cyanobacteria (sometimes
referred to as blue-green algae) typically cause the most frequent and severe blooms.7
Cyanobacterial HABs pose a threat to human and aquatic ecosystem health and can kill pets,
livestock, and wildlife. Some species of cyanobacteria produce toxins, called cyanotoxins, which
can cause hepatic (liver-related), neurologic, respiratory, dermatologic, and other symptoms.8
These may be acute or chronic, mild or severe, and in some cases may be fatal. Humans may be
exposed to cyanotoxins by consuming tainted drinking water, fish, or shellfish; swimming or
recreating in waters with certain concentrations of cyanotoxins present; or inhaling aerosolized
toxins.9 The cyanotoxins associated with these HABs can contaminate fish, interfere with a
variety of recreational activities, and cause other economic and environmental damages.
There are many types of cyanotoxins, which may have multiple variants with a wide range of
toxicities.10 The most commonly occurring and most studied cyanotoxin is microcystin.11
Although cyanobacterial HABs are considered to be the most prevalent and toxic types of HABs,
blooms of “golden algae” (Prymnesium parvum) are likely the most problematic of
noncyanobacterial freshwater HAB taxa (i.e., group of related organisms classified as a unit).12
Golden algal HABs have caused large fish kills worldwide, including millions of fish in Texas.
Most of the major fish kills have occurred since 2000. Golden algae thrive in brackish water, such
as the rivers and reservoirs found in areas of Texas, Oklahoma, and Wyoming. The toxins
produced by golden algae target gill-breathing organisms, such as fish, clams, and mussels.
According to information from two states that experience golden algal blooms, there is currently
no evidence that golden algal toxins pose a direct threat to humans, other mammals, or birds.13
Effects of cyanobacterial HABs and golden algae HABs are detailed in Table 1.
In addition to the effects of algal toxins on human and animal health, HABs can also contribute to
deteriorating water quality and ecosystem health. An overabundance of cyanobacteria or other
algae can block out sunlight and clog fish gills. In addition, as the algae die and decompose, they
consume oxygen, leaving waterways in a hypoxic (or low oxygen) state, sometimes forming
“dead zones”—areas where life cannot survive due to lack of oxygen. Low oxygen areas can
suffocate and kill fish and bottom-dwelling organisms such as crabs and clams. According to
EPA, over 166 dead zones have been documented nationwide, including in waterbodies such as

7 J. L. Graham et al., Cyanobacterial Harmful Algal Blooms and U.S. Geological Survey Science Capabilities, U.S.
Geological Survey, 2016.
8 Centers for Disease Control and Prevention, “Harmful Algal Bloom (HAB)-Associated Illness,” https://www.cdc.gov/
habs/illness-symptoms-freshwater.html.
9 Graham et al., Cyanobacterial Harmful Algal Blooms.
10 Graham et al., Cyanobacterial Harmful Algal Blooms.
11 Graham et al., Cyanobacterial Harmful Algal Blooms; and Keith A. Loftin et al., “Cyanotoxins in Inland Lakes of the
United States: Occurrence and Potential Recreational Health Risks in the EPA National Lakes Assessment 2007,”
Harmful Algae, vol. 56 (2016), pp. 77-90. Other common cyanotoxins that can have adverse environmental health
effects include anatoxins, cylindrospermopsins, and saxitoxins.
12 National Office for Harmful Algal Blooms at Woods Hole Oceanographic Institution, “Golden Algae, Prymnesium
Parvum
,” https://hab.whoi.edu/impacts/impacts-golden-algae/.
13 Texas Parks and Wildlife, Texas Commission on Environmental Quality, and U.S. Fish and Wildlife Service,
“Golden Alga Facts,” http://www.tceq.texas.gov/assets/public/comm_exec/pubs/gi/gi-378.pdf; Arizona Game and Fish
Department, “Golden Alga Information,” https://www.azgfd.com/fishing/golden-alga/.
Congressional Research Service
3

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

the Chesapeake Bay and the Gulf of Mexico.14 Significant economic losses have occurred as a
result of hypoxia.15

14 EPA, “Nutrient Pollution, The Effects: Environment,” https://www.epa.gov/nutrientpollution/effects-environment.
15 White House, Executive Office of the President, National Science and Technology Council, Committee on
Environment and Natural Resources, An Assessment of Coastal Hypoxia and Eutrophication in U.S. Waters, November
2003, https://www.whitehouse.gov/ostp/nstc/.
Congressional Research Service
4


Table 1. Selected Freshwater Harmful Algal Bloom (HAB) Taxa and Toxins and Their Effects
Human Health
Animal Health
Environmental
Affected Areas
HAB Taxa
Toxins
Effects
Effects
Effects
Economic Effects
in U.S.
Cyanobacteria
Microcystins,
Liver and kidney
Pet, farm animal, and
Water discoloration,
Loss of tourism,
Great Lakes and
cylindrospermopsin,
toxicity,
wildlife mortality; fish
foul odors
contamination of
many inland water
anatoxin-a, saxitoxins neurotoxicity,
kil s
drinking water
bodies
paralysis,
requiring additional
gastrointestinal
expensive water
effects, dermatitis,
treatment or
respiratory il ness
alternate water
sources, taste
problems in farmed
and wild-caught fish
(making them
inedible)
Haptophytes (e.g.,
Prymnesins,
No apparent adverse
Kil s fish and other
Water discoloration,
Loss of fishing
Alabama, Alaska,
Prymnesium parvum,
ichthyotoxins (i.e.,
effects
gil -breathing
foam formation
income, clean-up
Colorado, Florida,
or “golden algae”)
fish toxin)
organisms, such as
costs
Georgia, Nebraska,
clams and mussels
New Mexico, North
Carolina, Oklahoma,
Pennsylvania, South
Carolina, Texas, and
Wyoming
Source: Adapted from National Science and Technology Council, Subcommittee on Ocean Science and Technology, Harmful Algal Blooms and Hypoxia Comprehensive
Research Plan and Action Strategy: An Interagency Report
, Interagency Working Group on the Harmful Algal Bloom and Hypoxia Research and Control Act, February 11,
2016, p. 49.
Notes: Table includes information only on Freshwater HAB taxa and toxins discussed in this report. For a complete list of freshwater and marine HABs, toxins, and
their effects, see the source above, Appendix 1, pp. 49-52.
CRS-5

link to page 11 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Factors Contributing to HAB Formation
Many factors may influence the occurrence and prevalence of HABs in freshwater, including
nutrient concentrations, water temperature, availability of light, pH, and water circulation.
Nutrient enrichment is widely recognized as one of the key causes of HAB formation.16 Nutrients,
such as nitrogen and phosphorus, are essential to plant growth and natural parts of aquatic
ecosystems. However, when high levels of nutrients enter a body of water, they stimulate plant
and algal growth, which can lead to depletion of dissolved oxygen (as explained above), reduced
transparency (i.e., turbidity), changes to the biological community (e.g., loss of sportfish, such as
bass), and degradation of the aesthetic appeal of the water (i.e., from odor and scums). This
process is called eutrophication.17
While some sources of nutrients in water bodies are natural, many anthropogenic activities
contribute nutrients to waterbodies from a number of point and nonpoint sources. Point sources
include municipal and industrial wastewater discharges and concentrated animal feeding
operations (CAFOs).18 Nonpoint sources include urban stormwater runoff, failing septic systems,
atmospheric deposition of nitrogen from fossil fuel emissions, runoff from fertilized cropland,
and manure runoff from cropland, pastures, and animal feeding operations. See Table 2 for more
information on these sources.
Studies also indicate that increased temperatures and changes in frequency and intensity of
rainfall associated with climate change may also favor HAB formation.19 HABs generally
proliferate in warmer waters. In addition, some studies have found that swings between flooding
and drought may enhance HAB formation. For example, if intense rainfall is followed by a
drought, the nutrients washed into receiving water bodies may remain in them longer, increasing
the potential for HABs.20

16 Graham et al., Cyanobacterial Harmful Algal Blooms; and Lopez et al., Scientific Assessment of Freshwater Harmful
Algal Blooms
.
17 EPA, “Preventing Eutrophication: Scientific Support for Dual Nutrient Criteria,” February 2015,
https://www.epa.gov/sites/production/files/documents/nandpfactsheet.pdf.
18 CAFOs are point sources, as defined by CWA Section 502(14). CAFOs are agricultural operations where animals are
kept and raised in confined situations that meet criteria established in EPA’s CAFO regulation (40 C.F.R. 122.23).
These criteria include specific numbers of confined animals and designation as a significant contributor of pollutants.
19 H. W. Paerl and J. Huisman, “Climate Change: A Catalyst for Global Expansion of Harmful Cyanobacterial
Blooms,” Environmental Microbiology Reports, vol. 1, no. 1 (February 2009), pp. 27-37; National Science and
Technology Council, Subcommittee on Ocean Science and Technology, Harmful Algal Blooms and Hypoxia
Comprehensive Research Plan and Action Strategy: An Interagency Report
, Interagency Working Group on the
Harmful Algal Bloom and Hypoxia Research and Control Act, February 11, 2016; Jerry M. Melillo et al., Climate
Change Impacts in the United States: The Third National Climate Assessment
, U.S. Global Change Research Program,
October 2014, pp. 79, 198, 216.
20 Paerl and Huisman, “Climate Change,” pp. 27-37.
Congressional Research Service
6

link to page 11 link to page 11 link to page 11 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Table 2. Anthropogenic Sources of Nutrients in Water
Source
Source Type
Details
Municipal wastewater
Point
Municipal wastewater treatment plants process wastewater from
discharges
homes and businesses. The wastewater contains nitrogen and
phosphorus from human waste, food, and phosphate-containing soaps
and detergents. Some wastewater treatment plants have upgraded
their systems and are able to remove more nitrogen and phosphorus
than others.
Industrial wastewater
Point
Industrial wastewater treatment plants process wastewater from a
discharges
variety of manufacturing or industrial activities. According to EPA,
certain types of industrial waste tend to possess higher quantities of
nutrients, such as those from processors of food, beverages, livestock,
and agricultural products.
Concentrated animal
Pointa
CAFOs are animal feeding operations (see entry below) that meet
feeding operations
numeric thresholds for the number of animals they contain and/or
(CAFOs)
meet certain pol ution discharge criteria.b Manure discharge can
contribute nitrogen and phosphorus to waterways.
Animal feeding
Nonpoint
AFOs are facilities in which livestock or poultry are kept and raised in
operations (AFO)
confinement that meet certain conditions. Manure runoff and
wastewater from AFOs can contribute nitrogen and phosphorus to
waterways.c
Agricultural runoff
Nonpoint
Excess fertilizer applied to crops and fields, animal manure, and soil
erosion can all contribute to increased nitrogen and phosphorus
entering water bodies during rainfal events.
Urban stormwater
Nonpoint
During rainfall or snowmelt events, water carries nitrogen and
runoff
phosphorus across paved surfaces and buildings and into local water
bodies or storm drains. Fertilizers, yard and pet waste, and phosphate-
containing soaps and detergents can contribute to higher nutrient
concentrations in stormwater.
Failing septic systems
Nonpoint
If septic systems are improperly managed, elevated nitrogen and
phosphorus levels can be released into local water bodies or
groundwater. Common causes of failure include aging, inappropriate
design, overloading the system, and poor maintenance.
Fossil fuels
Nonpoint
Combustion of fossil fuels by electric power generation, industry,
transportation, and agriculture release nitrogen oxides into the
atmosphere. Nitrogen oxides are deposited back onto land and can be
washed into nearby waters during rainfall events.
Sources: EPA “Nutrient Pol ution: Sources and Solutions,” https://www.epa.gov/nutrientpol ution/sources-and-
solutions; EPA, Office of Water, A Compilation of Cost Data Associated with the Impacts and Control of Nutrient
Pollution
, EPA 820-F-15-096, May 2015, pp. IV-23.
Notes:
a. Under CWA Section 502(14), CAFOs are point sources. However, the definition of point sources
specifically excludes agricultural stormwater discharges. Therefore, agricultural stormwater discharges from
CAFOs are nonpoint sources.
b. For EPA’s regulatory definitions of Large CAFOs, Medium CAFOs, and Small CAFOs, see 40 C.F.R. Section
122.23.
c. The conditions for an AFO include (1) animals are confined or maintained for a total of 45 days or more in
any 12-month period, and (2) crops are not sustained in the normal growing season over any portion of the
lot or facility. See 40 C.F.R. Section 122.23.
Congressional Research Service
7

link to page 13 link to page 21 link to page 5 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Incidence and Trends
Scientists largely agree that the frequency and distribution of HABs, the economic losses from
them, the types of resources affected, and the number of toxins and toxic species have all
increased in recent years.21 Some scientists note that factors such as better detection methods and
increased reporting have contributed to the upward trend. HABs, including cyanobacterial HABs,
have been recorded in the waters of all 50 states, with some HABs crossing state lines.22 Figure 2
shows the generalized distribution of selected freshwater HAB events (cyanobacterial HABs and
golden algal HABs) that took place between 2006 and 2015 across the United States.
The findings of EPA’s most recent national assessment of lakes23 are consistent with other reports
of the rising trend in HABs. In EPA’s 2012 National Lake Assessment, EPA concluded that there
was little change from its 2007 survey of lakes, with two exceptions—trends in algal toxin and
nutrient measures.24 In 2012, EPA and its partners detected microcystin in 39% of lakes, a 9.5%
increase from 2007.25 EPA noted, however, that for both studies, the concentrations of
microcystin remained low and rarely exceeded the levels of concern established by the World
Health Organization (WHO) for recreational uses (see “Regulatory Efforts and Guidelines”). EPA
also found an 8.3% increase in the percentage of lakes in the “most disturbed condition” category
when analyzing the density of cyanobacterial cells (i.e., an indicator of risk for exposure to algal
toxins because the cells may produce toxins).26 Finally, EPA found an overall increase in the
median concentration of phosphorus across all lakes27 and a “dramatic” decline (18.2%) in the
percentage of lakes with low nutrients and high oxygen levels.28 These findings are important
because in many lakes, phosphorus is considered the limiting nutrient, meaning that the available
quantity of this nutrient controls the pace of algal production. It also means that even small
increases in phosphorus can lead to very rapid increases in algal growth.29 More broadly, the
study found that nutrient pollution is a widespread problem across the country. Approximately
35% of lakes have excessive levels of total nitrogen, and 40% of lakes have excessive levels of
total phosphorus.30

21 See footnote 1.
22 National Office for Harmful Algal Blooms at Woods Hole Oceanographic Institution, “Distribution of HABs in the
U.S.,” https://hab.whoi.edu/maps/regions-us-distribution/.
23 EPA, National Lakes Assessment 2012: A Collaborative Survey of Lakes in the United States, EPA 841-R-16-113,
December 2016, https://nationallakesassessment.epa.gov/. Every five years, EPA and its partners sample more than
1,000 lakes to inform the agency’s National Lakes Assessment, a statistically based assessment of the biological,
chemical, physical, and recreational condition of the nation’s lakes.
24 EPA, National Lakes Assessment 2012, pp. 1-2.
25 EPA, National Lakes Assessment 2012, pp. 1, 18.
26 EPA, National Lakes Assessment 2012, p. 28. Note that according to the assessment, 15% of lakes are in the most
disturbed condition using cyanobacteria cell counts as an indicator of risk for exposure to algal toxins.
27 EPA, National Lakes Assessment 2012, pp. 2, 13. The median concentration of phosphorus increased from 20 µg/L
in 2007 to 37 µg/L in 2012.
28 EPA, National Lakes Assessment 2012, pp. 2, 13. In 2012, EPA found 18.2% fewer oligotrophic lakes (i.e., lakes
with low nutrients and high oxygen levels) than in 2007.
29 EPA, National Lakes Assessment 2012, p. 12.
30 The terms total nitrogen and total phosphorus include all forms of the nutrient in the sample. For example, total
phosphorus
includes a measurement of orthophosphate, condensed phosphate, and organic phosphate.
Congressional Research Service
8


Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Figure 2. Generalized Distribution of Selected Freshwater Harmful Algal Blooms
(HABs) in the United States

Sources: Graphic adapted from a National Office of Harmful Algal Blooms at Woods Hole Oceanographic
Institution map of HABs that occurred between 2006 and 2015 (available at http://whoi.edu/redtide/regions/us-
distribution) and an EPA adaptation of the map that reflects input from HAB experts with broad experience in
HAB events and reports to the U.S. National Office for Harmful Algal Blooms (see EPA, Recommended Human
Health Recreational Ambient Water Quality Criteria or Swimming Advisories for Microcystins and Cylindrospermopsin
,
EPA 822-R-19-001, May 2019, p. 39). Note that the Woods Hole Oceanographic Institution Harmful Algae
website (https://hab.whoi.edu/maps/regions-us-distribution/) states that all 50 states are impacted by
cyanobacterial HABs and at least 23 states are impacted by golden algal HABs.
Notes: Each state that has experienced one or more cyanobacterial HABs or golden algal HABs is indicated
with a single dot. Larger green ovals mark areas where more widespread cyanobacterial HAB problems
occurred.
Efforts to Address Harmful Algal Blooms
Enacted Legislation
Congress has recognized the increasing frequency of HABs and has passed legislation in an effort
to address public health, economic, and environmental consequences of HABs. In 1998, Congress
passed the Harmful Algal Bloom and Hypoxia Research and Control Act (HABHRCA), which
established an Interagency Task Force on Harmful Algal Blooms and Hypoxia.31 It required the
task force to prepare reports assessing HABs and hypoxia with a focus on coastal waters and
authorized funding for HAB and hypoxia-related research, education, and monitoring activities.

31 P.L. 105-383.
Congressional Research Service
9

link to page 15 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

The Department of Commerce’s National Oceanic and Atmospheric Administration (NOAA)
chaired the task force. In 2004, Congress reauthorized HABHRCA and expanded it to include
assessments of HABs in freshwater.32 In 2014, Congress again reauthorized HABHRCA and
established a national HAB and Hypoxia Program to be maintained by NOAA through the task
force.33 It identified NOAA and EPA as the lead federal agencies for marine and freshwater
aspects of the program, respectively, and required additional reports and a comprehensive
research plan and action strategy.
Congress most recently amended and reauthorized appropriations for HABHRCA in January
2019 through the Harmful Algal Bloom and Hypoxia Research and Control Amendments Act of
2017, included within the National Integrated Drought Information System Reauthorization Act
of 2018 (P.L. 115-423, §9). The HABHRCA amendments require the task force to submit a
scientific assessment of HABs in U.S. coastal and freshwater systems once every five years to
Congress, require NOAA to develop and maintain a public website that provides information on
HAB and Hypoxia Program activities, and authorize NOAA or EPA to determine that a hypoxia
or HAB event is an event of national significance (for marine and freshwater systems,
respectively). If an event is designated, the legislation authorizes NOAA or EPA to make funds
available to the affected state or locality to assess and mitigate the detrimental environmental,
economic, subsistence use, and public health effects of the event.34 NOAA and EPA separately
published notices of intent to develop a policy for determining HAB and hypoxia events of
national significance in the Federal Register in July and September 2019, respectively.35
In 2015, in response to public safety concerns arising from the Toledo, Ohio, HAB event,
Congress passed legislation addressing algal toxins in drinking water. The Drinking Water
Protection Act amended the Safe Drinking Water Act to require EPA to develop a strategic plan to
assess and manage the risks associated with algal toxins in public drinking water supplies.36
The following year, Congress included a provision in the Water Infrastructure Improvements for
the Nation (WIIN) Act that required EPA to designate a Harmful Algal Bloom Coordinator to
coordinate projects and activities under the Great Lakes Restoration Initiative involving HABs in
the Great Lakes.37 Table 3 provides a list and description of selected HAB-specific legislation
enacted since 1998 that pertains to freshwater HABs.38

32 P.L. 108-456.
33 P.L. 113-124.
34 P.L. 115-423, §9(g).
35 NOAA, “Notice of Intent to Develop a Policy for Determining Harmful Algal Bloom (HAB) and Hypoxia Events of
National Significance in Marine or Coastal Waters; Opportunity to Provide Information,” 84 Federal Register 35854,
July 25, 2019; EPA, “Notice of Intent to Develop a Policy on the Determination of a Harmful Algal Bloom (HAB) and
Hypoxia as an Event of National Significance in Freshwater Systems,” 84 Federal Register 48610, September 16,
2019.
36 P.L. 114-45.
37 P.L. 114-322.
38 Congress has also passed legislation authorizing appropriations for grant programs and research that includes HABs
as a focus area, but these laws are not included in the table. For example, Congress has reauthorized the National Sea
Grant College Program to provide funds for competitive grants for university research on HABs (P.L. 105-160, P.L.
107-299, and P.L. 110-394) and has amended the CWA’s National Estuary Program to authorize the Administrator to
provide competitive grants to certain recipients to address urgent and challenging issues, including HABs (P.L. 114-
162).
Congressional Research Service
10

link to page 16 link to page 16 link to page 16 link to page 16 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Table 3. Selected Freshwater Harmful Algal Bloom (HAB)-Related Acts
Law
Description
Harmful Algal Bloom

Established an Interagency Task Force of Harmful Algal Blooms and Hypoxia,
and Hypoxia Research
chaired by the Department of Commerce, to consist of representatives from nine
and Control Act
federal agencies, the Office of Science and Technology Policy, the Council on
(HABHRCA), 1998 (P.L.
Environmental Quality, and “such other Federal agencies as the President considers
105-383)
appropriate”

Required the task force to prepare reports assessing HABs and hypoxia, with a
focus on coastal waters

Authorized funding for research, education, and monitoring activities related to
HABs and hypoxia: $15,000,000 for FY1999; $18,250,000 for FY2000; and
$19,000,000 for FY2001
Harmful Algal Bloom

Retained the Interagency Task Force (which the President could have
and Hypoxia
disestablished under the 1998 act)
Amendments Act of

2004 (P.L. 108-456)

Expanded the focus of the act to include assessments of HABs in freshwater

Mandated five reports, one of which was to assess current knowledge about HABs
in freshwater, including a research plan for coordinating federal efforts to better
understand freshwater HABs

Required the task force to complete a scientific assessment of HABs at least once
every five years—an assessment that shall examine marine and freshwater blooms
after the initial assessment was complete

Reauthorized funding for research, education, and monitoring activities:
$23,500,000 for FY2005; $24,500,000 for FY2006; $25,000,000 for FY2007; and
$25,500,000 for FY2008a
Harmful Algal Bloom

Established a National HAB and Hypoxia program to be maintained and enhanced
and Hypoxia Research
by the National Oceanic and Atmospheric Administration (NOAA)b through the
and Control
interagency task force
Amendments Act of

2014 (P.L. 113-124)

Identified NOAAb as the lead federal agency with primary responsibility for
administering the program and directed EPA to lead the freshwater aspects of the
program

Added the Centers for Disease Control and Prevention as a member of the
interagency task force

Required the interagency task force to develop a comprehensive research plan and
action strategy to address marine and freshwater HABs and hypoxia

Required regional reports, including a progress report on Northern Gulf of Mexico
hypoxia and an integrated assessment of and plan to address hypoxia and HABs in
the Great Lakes

Reauthorized funding to implement the program and research plan and action
strategy: $20,500,000 for each of FY2014-FY2018
Harmful Algal Bloom

Requires the interagency task force to complete, and submit to Congress, a
and Hypoxia Research
scientific assessment of HABs in U.S. coastal waters and freshwater systems once
and Control
every five years
Amendments Act of

2017 (P.L. 115-423)

Added the Army Corps of Engineers as a member of the interagency task force
c

Requires NOAA to develop and maintain a publicly accessible website that
provides information on the HAB and Hypoxia Program activities

Added an objective for peer-reviewed, merit-based, competitive grant funding to
include accelerating the use of effective methods of intervention and mitigation to
reduce the frequency, severity, and impacts of HABs and hypoxia events

Added a section that allows NOAA or EPA to determine that a hypoxia or HAB
event is an event of national significance, which then authorizes NOAA or EPA to
make sums available to the affected state or locality for the purposes of assessing
Congressional Research Service
11

link to page 16 link to page 16 link to page 16 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Law
Description
and mitigating the detrimental environmental, economic, subsistence use, and
public health effects of the event (additionally outlines federal share requirements
and authorizes the acceptance of donations)

Reauthorized funding to implement the HAB and Hypoxia program: $20,500,000
for each of FY2019-FY2023
Drinking Water

Amended the Safe Drinking Water Act to require EPA to develop—and submit to
Protection Act (P.L.
Congress—a strategic plan to assess and manage the risks associated with algal
114-45)
toxins in public drinking water suppliesd

Required EPA to include in the plan steps and schedules for EPA to
(1) assess health risks of algal toxins in drinking water,
(2) publish a list of toxins likely to pose risks and summarize their health effects,
(3) determine whether to issue health advisories for listed toxins,
(4) publish guidance on feasible methods to identify and measure the algal toxins in
water,
(5) recommend feasible treatment and source water protection options, and
(6) provide technical assistance to states and water systems.

Required the Government Accountability Office to report to Congress on federal
funds expended for each of FY2010-FY2014 to examine toxin-producing
cyanobacteria and algae or address public health concerns related to harmful algal
bloomse
Water Infrastructure

One of the act’s provisions directed the EPA Administrator to designate a Harmful
Improvements for the
Algal Bloom Coordinator to coordinate—with federal partners, Great Lakes
Nation (WIIN) Act (P.L.
states, Indian tribes, and other nonfederal stakeholders—projects and activities
114-322)
under the Great Lakes Restoration Initiative involving HABs in the Great Lakesf
Source: CRS.
Notes: This table does not include enacted legislation that authorizes appropriations for grant programs that
include HABs as one of several focus areas.
a. The reauthorization expired in 2008, however, the Consolidated Appropriations Act of 2008 (P.L. 110-161)
provided authorizations of $30,000,000 for each of FY2008-FY2010.
b. The act specifies that the Under Secretary of the Department of Commerce shall have this role. The Under
Secretary of Commerce for Oceans and Atmosphere is the administrator of NOAA.
c. The Harmful Algal Bloom and Hypoxia Research and Control Amendments Act of 2017 was enacted as P.L.
115-423 on January 7, 2019.
d. EPA, Algal Toxin Risk Assessment and Management Strategic Plan for Drinking Water: Strategy Submitted
to Congress to Meet the Requirements of P.L. 114-45, 810R04003, November 2015.
e. U.S. Government Accountability Office, Environmental Protection: Information on Federal Agencies’ Expenditures
and Coordination Related to Harmful Algae, GAO-17-119, October 2016.
f.
According to EPA, the administrator designated the Great Lakes National Program Office Director as the
Harmful Algal Bloom Coordinator.
In addition to HAB-specific legislation, the Clean Water Act (CWA) authorizes EPA to address
water quality concerns associated with HABs.39 The act establishes a system, under Section 303,
for states to adopt ambient water quality standards consisting of the designated use or uses of a
water body (e.g., recreational, public water supply, or aquatic life) and the water quality criteria
that are necessary to protect the use or uses.40 States then use their water quality standards to

39 Clean Water Act, as amended (33 U.S.C. §1251 et seq.).
40 33 U.S.C. §1313.
Congressional Research Service
12

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

determine which waters must be cleaned up, how much effluent may be discharged, and what is
needed for protection.
Section 304(a) requires the EPA Administrator to publish and, from time to time, revise water
quality criteria that accurately reflect the latest scientific knowledge on the kind and extent of all
identifiable effects on human health and the environment that might be expected from the
presence of pollutants.41 These criteria constitute guidance that states use in adopting their water
quality standards. As recognized by Section 510 of the CWA,42 states may develop water quality
standards that are more stringent than required by EPA regulations. EPA’s water quality standards
regulations43 require that in developing water quality standards, states must adopt water quality
criteria that protect the designated use. States are to establish numerical criteria—based on (1)
EPA’s recommended criteria, (2) EPA’s criteria modified to reflect site-specific conditions, or (3)
other scientifically defensible methods—and establish narrative criteria or criteria based on
biomonitoring methods where numerical criteria cannot be established or to supplement
numerical criteria.
Section 303(d) of the CWA requires states to identify waters that are impaired by pollution, even
after application of pollution controls.44 For those waters, states must establish a Total Maximum
Daily Load (TMDL) of pollutants to ensure that water quality standards can be attained. A TMDL
is a quantitative assessment of pollution sources and pollutant reductions needed to restore and
protect U.S. waters; it is also a planning process for attaining water quality standards. TMDLs
may address all pollution sources, including point sources, such as municipal sewage treatment or
industrial plant discharges, and nonpoint sources such as urban runoff and agricultural runoff.
Also, Section 118 of the CWA provides that the United States should seek to attain the goals
embodied in the Great Lakes Water Quality Agreement of 1978, as amended by the Water Quality
Agreement of 1987 and any other agreements and amendments.45 It tasks EPA to take the lead in
the effort to meet the agreement’s goals, working with other federal agencies, states, and
localities. As seen in the text box, the most recent amendment includes a HAB-related goal.

41 33 U.S.C. §1314.
42 33 U.S.C. §1370.
43 40 C.F.R. §131.
44 33 U.S.C. §1313.
45 33 U.S.C. §1269. In 1987 amendments to the CWA (P.L. 100-4) Congress affirmed the goals of the amended Great
Lakes Water Quality Agreement of 1978.
Congressional Research Service
13

link to page 19 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Great Lakes Water Quality Agreement
The Great Lakes Water Quality Agreement, which was first signed in 1972, is a commitment between the United
States and Canada to restore and protect the waters of the Great Lakes.46 It was amended most recently in 2012
to better identify and manage current environmental issues and prevent emerging environmental issues from
affecting the waters of the Great Lakes while upholding and modernizing commitments made in previous
agreements. One of the nine objectives of the 2012 agreement is that the waters of the Great Lakes should “be
free from nutrients that directly or indirectly enter the water as a result of human activity, in amounts that
promote growth of algae and cyanobacteria that interfere with aquatic ecosystem health, or human use of the
ecosystem.” Although previous agreements had also included efforts to reduce nutrients and prevent excessive
algal growth, the 2012 amendments were the first to specifically include cyanobacteria.
Federal Agency Efforts
Many federal agencies are involved in carrying out various HAB-related activities, including
conducting HAB research, monitoring algal toxins and water quality, forecasting HABs,
supporting projects to improve water quality, and facilitating community outreach efforts. Some
in Congress, however, have expressed concern about the activities and expenditures of various
agencies and potential redundancies. In the Drinking Water Protection Act (P.L. 114-45), enacted
August 7, 2015, Congress directed the Government Accountability Office (GAO) to inventory
funds expended by federal agencies to examine toxin-producing cyanobacteria and algae or
address public health concerns related to harmful algal blooms. GAO was to recommend ways to
improve interagency coordination and reduce duplication of efforts. According to the 2016 GAO
report that responded to the mandate, 17 agencies conducted research, monitoring, response, or
other HAB-related activities between FY2013 and FY2015.47 The GAO report provides detailed
information on federal agencies’ key HAB-related activities, expenditures, and specific statutory
authorities, and, thus, this report will not discuss these in detail.48 Rather, this section identifies
the federal agencies involved in a key interagency effort and highlights actions EPA specifically is
taking in its role as the leader of freshwater HAB issues.
As previously mentioned, HABHRCA established an interagency task force that is charged with
 promoting a national strategy to help communities understand, predict, control,
and mitigate freshwater and marine HAB and hypoxia events;
 enhancing, coordinating, and assessing the activities of existing HABs and
hypoxia programs; and
 providing for development of a comprehensive research plan and action strategy.
Table 4 provides a list of the federal agencies and organizations specifically required in
HABHRCA to participate on the task force. The reauthorization of HABHRCA in 2014
reconstituted the task force as the Interagency Working Group on the Harmful Algal Bloom and
Hypoxia Research and Control Act (IWG-HABHRCA), responsible for maintaining a national
HAB/hypoxia program. NOAA and EPA share primary responsibility under HABHRCA for

46 Great Lakes Water Quality Agreement, U.S.-Canada, as amended, September 7, 2012.
47 GAO, Environmental Protection: Information on Federal Agencies’ Expenditures and Coordination Related to
Harmful Algae
, GAO-17-119, October 2016, p. 5. Note that GAO identified 17 agencies that have conducted research,
monitoring, or other HAB-related activities in FY2013-FY2015. However, the report focuses on 12 federal agencies
whose data was sufficiently reliable for the purposes of the report.
48 In addition, Members of Congress have requested a follow-on study from GAO regarding HABs. See House Science,
Space, and Technology Committee, “Bipartisan, Bicameral Group of Members Request GAO Study on Harmful Algal
Blooms,” press release, April 29, 2020, https://science.house.gov/news/press-releases/bipartisan-bicameral-group-of-
members-request-gao-study-on-harmful-algal-blooms.
Congressional Research Service
14

link to page 19 link to page 19 link to page 21 link to page 20 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

administering the national HAB and hypoxia program, with NOAA leading marine aspects of the
program and EPA in charge of freshwater aspects.
Table 4. Interagency Task Force on Harmful Algal Blooms (HABs) and Hypoxia
Representatives Specifically Named in HABHRCA
Agency
Department of Commerce, National Oceanic and Atmospheric Administration (NOAA)a
Environmental Protection Agency (EPA)a
Department of Agriculture
Department of the Interior
Department of the Navy
Department of Health and Human Services
National Science Foundation
National Aeronautics and Space Administration
Food and Drug Administration
Office of Science and Technology Policy
Council on Environmental Quality
Centers for Disease Control and Prevention
Army Corps of Engineers
Source: CRS.
Notes: NOAA and EPA serve as co-chairs of the interagency task force. HABHRCA states that the task force
shall also include “such other Federal agencies as the President considers appropriate.”
a. NOAA and EPA serve as co-chairs on the task force.
In its role under HABHRCA and the CWA, EPA’s efforts to address HABs include coordinating
the efforts of multiple entities, developing regulations and guidelines to protect water quality (see
“Regulatory Efforts and Guidelines” section), conducting research, providing financial assistance
through grants and other agreements, and educating the public.49 In its coordination role, EPA
leads, chairs, or co-chairs several working groups or task forces, including the IWG-HABHRCA,
the Inland HAB Discussion Group, the Great Lakes Interagency Task Force, and the Mississippi
River/Gulf of Mexico Watershed Nutrient Task Force (Hypoxia Task Force). See Table 5 for a
description of these efforts.
EPA has also conducted internal research on HABs and their toxins focused on water quality
(including how different factors such as nutrients, light, temperature, etc., affect HAB occurrence
and toxicity), human and ecological health effects, monitoring and analytical methods research,
and drinking water treatment research.50 The agency also provides research grants, such as those
provided through the Science to Achieve Results (STAR) program, focused on topic areas

49 Education efforts include communication and outreach, such as newsletters and videos, to increase public awareness
regarding the adverse effects of nutrient pollution and HABs.
50 GAO, Environmental Protection: Information on Federal Agencies’ Expenditures and Coordination Related to
Harmful Algae
, GAO-17-119, October 2016.
Congressional Research Service
15

link to page 20 link to page 20 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

including the prediction, prevention, control, and mitigation of freshwater HABs and the fate and
effects from less-common emerging HABs.51
EPA also provides financial assistance to states, tribes, and others to address water pollution,
including nonpoint source pollution. Examples of such assistance include nonpoint source
implementation grants under CWA Section 319, capitalization grants under the Clean Water State
Revolving Fund, and grants under CWA Section 106, which are provided to states, interstate
agencies, and tribes to administer programs that prevent, reduce, and eliminate water pollution.
Table 5. EPA Efforts to Coordinate Freshwater HAB-Related Activities
Coordination Effort
Description
Interagency Working Group on the Created after the HABHRCA amendments of 2014, this interagency
Harmful Algal Bloom and Hypoxia
working group is the primary, government-wide mechanism through which
Research and Control Act (IWG-
federal agencies coordinate their HAB-related activities and report on
HABHRCA)
specific topics to Congress, such as research plans and action strategies for
addressing HABs and hypoxia. The group meets twice a month and is co-
chaired by the NOAA and EPA.
Inland HAB Discussion Group
Led by EPA, the U.S. Geological Survey, and the Centers for Disease
Control and Prevention to share information among federal, state, local,
and industry stakeholders through free webinars, this informal discussion
group was created out of an expressed need by federal researchers and
state agencies to bridge a communication gap with respect to inland HAB
research, monitoring, human and ecological health risk assessment,
education, and outreach.
Great Lakes Interagency Task
Chaired by EPA, this task force consists of 11 Cabinet and other federal
Force
agency heads to coordinate the restoration of the Great Lakes. Created by
a May 18, 2004, executive order,a the task force, among other things,
coordinates the development of consistent federal policies, strategies,
projects, and priorities pertaining to the restoration and protection of the
Great Lakes. According to EPA officials, since 2009, the task force has
overseen the implementation of the Great Lakes Restoration Initiative
(GLRI),b a federally led effort to carry out programs and projects for Great
Lakes protection and restoration. In particular, the task force has overseen
the development of comprehensive, multiyear action plans that identify
goals, objectives, measurable ecological targets, and specific actions for four
GLRI focus areas. One of these focus areas is reducing nutrient runoff that
contributes to harmful/nuisance algal blooms.
Mississippi River/Gulf of Mexico
Through this EPA-led task force, federal agencies coordinate with 12 states
Watershed Nutrient Task Force
and a national tribal representative to address hypoxia in the Mississippi
(Hypoxia Task Force)
River and the northern Gulf of Mexico.
Source: Excerpted from U.S. Government Accountability Office, Environmental Protection: Information on Federal
Agencies’ Expenditures and Coordination Related to Harmful Algae
, GAO-17-119, October 2016, p. 23.
Notes:
a. Executive Order 13340, “Establishment of Great Lakes Interagency Task Force and Promotion of a Regional
Col aboration of National Significance for the Great Lakes,” 69 Federal Register 29043-29045, May 18, 2004.
b. The 114th Congress codified the GLRI in P.L. 114-322, Section 5005. As noted, this provision directed the
EPA Administrator to designate a coordinator for GLRI HAB activities.

51 EPA “Freshwater Harmful Algal Blooms,” Funding Opportunity Announcement Number EPA-G2017-STAR-A1,
Office of Research and Development, October 28, 2016.
Congressional Research Service
16

link to page 21 link to page 21 link to page 22 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Regulatory Efforts and Guidelines
EPA and states have also taken steps to address HABs and nutrient loads that contribute to their
proliferation through regulatory efforts and guidelines. This section focuses on regulatory efforts
and guidelines related to EPA’s authorities under the CWA and specifically excludes efforts under
the Safe Drinking Water Act.
HABs, Cyanobacteria, and Cyanotoxins
EPA, WHO, and many states have developed guidelines for cyanotoxins in recreational waters.52
These guidelines are summarized in Table 6 and discussed below.
Table 6. Summary of EPA, WHO, and State Guidelines for Cyanotoxins in
Recreational Waters
Organization
Microcystin
Cylindrospermopsin
Action
EPA
8 µg/L
15 µg/L
Swimming advisory triggered if value is
exceeded for one day
EPA recommends that when more than
three excursions (an exceedance during a
10-day assessment period) occur within a
recreational season and that pattern
reoccurs in more than one year, it is an
indication the water quality is or is
becoming degraded such that the water
body no longer supports a recreational
designated use
WHOa
Low < 10 µg/L
No guideline
Low: Post on-site risk advisory signs;
Moderate = 10-20
inform relevant authorities
µg/L
Moderate: Watch for scums or conditions
High = 20-2,000 µg/L
conducive to scums; discourage swimming
and further investigate hazard; post on-
Very High > 2,000
site risk advisory signs; inform relevant
authorities
High: Immediate action to control contact
with scums; possible prohibition of
swimming and other water contact
activities; public health fol ow-up
investigation; inform public and relevant
authorities
Statesb
0.8 µg/L-20 µg/L
1 µg/L-10 µg/L
Variety of actions, including issuing
advisories, closing beaches, and increasing
sampling
Sources: CRS analysis from the fol owing sources: EPA, “Recommended Human Health Recreational Ambient
Water Quality Criteria or Swimming Advisories for Microcystins and Cylindrospermopsin,” May 2019; and
WHO, “Guidelines for Safe Recreational Water Environments: Volume 1,” Coastal and Fresh Waters, 2003.
Notes:
a. Low, moderate, high, and very high refer to the probability of adverse health effects. No additional actions
were specifically listed for the “very high” probability category.

52 EPA has also developed recommended levels for drinking water for microcystin and cylindrospermopsin through
health advisories. See CRS In Focus IF10269, Algal Toxins in Drinking Water: EPA Health Advisories, by Mary
Tiemann.
Congressional Research Service
17

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

b. Among the 24 states that have quantitative guidelines for cyanotoxins, these values represent the range of
the lowest recreational water guideline or action levels that trigger or recommend a health protective
action. For additional information on state guidelines and action levels, see table source 1, pp. 23-25 for a
list of the lowest recreational water guideline or action level for each state and Appendix B for a more
complete list of state guidelines, action levels, and recommended actions.
EPA Guidelines
In December 2016, EPA issued draft recreational water quality criteria or swimming advisories
for microcystins and cylindrospermopsin for public comment.53 According to EPA, these criteria
reflected the concentrations of two cyanotoxins that would be protective of human health in
recreational waters used for swimming or other activities: 4 µg/L for microcystin and 8 µg/L for
cylindrospermopsin.54 EPA suggested that states could consider using the proposed values when
determining whether to post swimming advisories in recreational waters and could consider using
the same values when adopting new or revised water quality standards.
Many entities—including states, representatives of publicly owned treatment works,55 agricultural
organizations, and environmental groups—provided comments on the draft criteria:56
 Some commenters, including states, were supportive of the criteria for purposes
of informing swimming advisory decisions but did not support the use of the
criteria for developing water quality standards, noting, among other concerns,
that cyanotoxins are not a pollutant discharged into waterways but rather result
from other pollutants (nutrients) entering waterways and other factors.
Environmental groups generally supported EPA’s criteria for use in both
swimming advisories and development of water quality standards.
 Commenters’ opinions varied regarding the proposed concentrations of
microcystin and cylindrospermopsin in the draft criteria. Some states felt the
levels were appropriate, environmental groups felt they should be more stringent,
and other states suggested they are overly protective, particularly when compared
to the WHO guideline for microcystin.
Many commenters—particularly states, publicly owned treatment works, and agricultural
groups—expressed a number of implementation concerns. One key concern raised was that these
criteria, if used for water quality standards, would improperly regulate response organisms rather
than a discharged pollutant. Some argued that algal toxins are not a pollutant that CWA permittees
discharge. Rather, the discharge of other pollutants, such as excess nutrients, may lead to HAB
formation. In its draft criteria document, EPA explained that it does not anticipate states using the

53 As discussed above, CWA Section 304(a) directs EPA to develop and publish and, from time to time, revise criteria
for water quality that accurately reflect the latest scientific knowledge. EPA, “Request for Scientific Views: Draft
Human Health Recreational Ambient Water Quality Criteria and/or Swimming Advisories for Microcystins and
Cylindrospermopsin,” 81 Federal Register 91929-91931, December 19, 2016. Note this comment period was extended.
See EPA, “Extension of Public Comment Period: Draft Human Health Recreational Ambient Water Quality Criteria
and/or Swimming Advisories for Microcystins and Cylindrospermopsin,” 82 Federal Register 10766-10767, February
15, 2017.
54 EPA, Draft Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for Microcystins
and Cylindrospermopsin
, EPA 822-P-16-002, December 2016, https://www.epa.gov/wqc/draft-human-health-
recreational-ambient-water-quality-criteria-andor-swimming-advisories.
55 The National Association of Clean Water Agencies, which represents the interests of publicly owned treatment
works (i.e., municipal wastewater treatment facilities), provided comments on behalf of its members.
56 Comments discussed in this section are available in Docket ID No. EPA-HQ-OW-2016-0715, available at
https://www.regulations.gov/docket?D=EPA-HQ-OW-2016-0715.
Congressional Research Service
18

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

criteria alone for permitting purposes, recognizing that cyanobacteria and their toxins are not
typically present in permitted discharges. EPA goes on to say the following:
Permits are more likely to be written to address point source discharges of the causal
pollutants, such as nutrients, on a waterbody-specific or watershed basis, where the permit
writer has determined there is a reasonable potential for the causal pollutants in the
discharge to cause or contribute to an exceedance of the cyanotoxin standards.57
In this regard, some commenters expressed concern that it is not known precisely what level of
nutrients will result in a bloom, nor is it understood what factors will trigger the release of toxins.
Several commenters suggested that EPA explore these issues further before moving forward with
water quality criteria for purposes other than guiding advisory levels for swimming.
Many commenters also expressed implementation concerns regarding monitoring and sampling.
According to the Association of Clean Water Administrators58 many states do not currently have
mechanisms in place to adequately sample for the levels of the toxins specified by EPA, or they
lack adequate lab capacity to process increased samples. Some states, publicly owned treatment
works, and agricultural groups also commented that the variability of HABs within a body of
water and over even short spans of time can make sampling and analysis complicated,
particularly when using the data to determine if a water body is impaired. The commenters urged
EPA to address these issues in detail before moving forward with the criteria.
In June 2019, EPA announced the final recommended recreational water quality criteria or
swimming advisories for microcystins and cylindrospermopsin.59 EPA’s recommended
concentrations in recreational waters to protect human health while swimming or participating in
primary contact recreational activities on the water are 8 µg/L for microcystin and 15 µg/L for
cylindrospermopsin. In the Federal Register notice announcing the release of the criteria, EPA
noted that, in response to public comments, the agency did not apply a relative source
contribution term in deriving the final criteria.60 Additionally, EPA stated that the primary factor
for the change in recommended values was an updated ingestion rate, which reflected a study
published in 2017.61
WHO Guidelines
In 2003, WHO proposed guideline values for protection from adverse health outcomes associated
with cyanobacteria blooms in fresh water used for recreational purposes.62 The guidelines are
defined at three levels: low, moderate, and high probability of adverse health effects. WHO
concluded that a single guideline value was not appropriate because “it is necessary to
differentiate between the chiefly irritative symptoms caused by unknown cyanobacterial

57 EPA, Draft Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for Microcystins
and Cylindrospermopsin
.
58 The Association of Clean Water Administrators is a nonpartisan, national organization of state, interstate, and
territorial water program managers who implement CWA programs.
59 EPA, “Recommended Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for
Microcystins and Cylindrospermopsin,” 84 Federal Register 26413, June 6, 2019.
60 In calculating water quality criteria, EPA uses a relative source contribution to allow a percentage of the exposure to
a contaminant to include other potential sources. For the recreational water quality criteria for microcystin and
cylindrospermopsin, EPA assumed that all cyanotoxins exposure is from incidental exposure of water while recreating
and therefore did not apply a relative source contribution.
61 EPA, “Recommended Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for
Microcystins and Cylindrospermopsin,” 84 Federal Register 26413, June 6, 2019.
62 WHO, Guidelines for Safe Recreational Water Environments: Volume 1, Coastal and Fresh Waters, 2003.
Congressional Research Service
19

link to page 21 link to page 21 link to page 25 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

substances and the potentially more severe hazard of exposure to high concentrations of known
cyanotoxins, particularly microcystins.Table 6 shows the WHO guideline levels for
microcystin.63
State Guidelines
According to EPA, approximately 35 states had implemented cyanobacterial HAB guidelines for
recreational waterways as of March 2018.64 Some of these states use qualitative guidelines only
(i.e., visual inspection for blooms rather than quantitative detection methods) or quantitative
guidelines for cyanobacterial cell density rather than guidelines for the specific cyanotoxins.
Of the 35 states that had implemented cyanobacterial HAB guidelines, 24 had established
numeric guidelines for microcystin or cylindrospermopsin. The levels and associated actions vary
considerably among states (see Table 6). California has adopted the strictest concentrations for
both cyanotoxins (0.8 µg/L for microcystin and 1 µg/L for cylindrospermopsin). Several states
have adopted the WHO value of 20 µg/L for microcystin. Ten states have adopted quantitative
guidelines for cylindrospermopsin.
Some states have also added waters affected by algal blooms and algal toxins to their impaired
water lists (i.e., Section 303(d) lists) for algal blooms and algal toxins. According to data from
EPA’s Assessment and Total Maximum Daily Load Tracking and Implementation System, 30
states have listed waters as impaired for algal blooms, and three states—California, Iowa, and
New Hampshire—have listed waters as impaired for algal toxins (see Table 7). California and
Iowa have listed six and one of their waters, respectively, as impaired for algal toxins but have
not yet developed TMDLs. New Hampshire has listed 80 of its waters as impaired for algal toxins
and has developed 17 TMDLs.65 The New Hampshire TMDLs use nutrients, namely phosphorus,
as a surrogate for cyanobacteria (as well as for some other nutrient-associated parameters such as
chlorophyll A and dissolved oxygen in some cases).66 They establish a total phosphorus loading
target that, if met, is expected to achieve state water quality criteria and thresholds for
cyanobacteria (as well as for other nutrient associated parameters, such as chlorophyll A, for
some of the TMDLs).

63 WHO also established guidance values for cyanobacteria and chlorophyll-a.
64 EPA, Recommended Human Health Recreational Ambient Water Quality Criteria or Swimming Advisories for
Microcystins and Cylindrospermopsin
, EPA 822-R-19-001, May 2019, pp. 22-25, https://www.epa.gov/wqc/
recommended-human-health-recreational-ambient-water-quality-criteria-or-swimming-advisories.
65 According to information provided in a TMDL for Phillips Pond in Sandown, NH, lakes were listed as impaired for
swimming if surface blooms or “scums” of cyanobacteria were present—even if present only along a downwind shore.
New Hampshire Department of Environmental Services, Final Total Maximum Daily Load for Phosphorus for Phillips
Pond, Sandown, NH
, September 2018, p. 1-1, https://www.des.nh.gov/organization/commissioner/pip/publications/
documents/r-wd-18-11.pdf.
66 New Hampshire Department of Environmental Services, Final Total Maximum Daily Load for Phosphorus for
Phillips Pond, Sandown, NH
. See also New Hampshire Department of Environmental Services, Total Maximum Daily
Load for Hunkins Pond, Sanbornton, NH
, January 2011, p. 1-1, https://www.des.nh.gov/organization/divisions/water/
wmb/tmdl/documents/hunkins-pond.pdf.
Congressional Research Service
20

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Table 7. State Algal Bloom and Algal Toxin Impaired Waters Listings and TMDLs
Number of Waters
Number of Waters
Cause of Impairment
Number of States
Listed as Impaired
with TMDLs
Algal Bloom
30
1,495
445
Algal Toxin
3
87
17
Source: EPA data from the Assessment and Total Maximum Daily Load Tracking and Implementation System as
of August 30, 2019.
Note: These data reflect the most recent assessed waters and impaired waters reports provided to EPA by each
of the states, ranging from 2012 to 2018.
Nutrient Management
Scientists and policymakers widely recognize the need to reduce nutrient inputs to aquatic
systems to limit eutrophication and proliferation of HABs. According to EPA, nitrogen and
phosphorus pollution is one of the most serious and pervasive water quality problems in the
United States.67 While EPA and states have worked to address nutrient pollution for over a
decade, many observers believe more progress is needed to reduce the threat to water quality and
public health. EPA has acknowledged that without greater progress, “the successes to date will
likely be outpaced by the rapidly increasing population and the resulting increase in the rate and
impact of nitrogen and phosphorus pollution.”68
According to EPA, as of 2016, 45 states identified nutrient-related pollution as a priority to be
addressed by TMDLs and/or alternative restoration plans in setting long-term priorities for their
CWA Section 303(d) programs.69 As of May 2016, more than 8,600 nutrient-related TMDLs had
been established, primarily by states, to guide nutrient reduction efforts in more than 5,800
waterbodies.70
In 2016, EPA issued a memorandum with a renewed call to states and stakeholders to intensify
their efforts, in collaboration with EPA, to reduce nutrient pollution.71 The memorandum
emphasized EPA’s support for state planning or implementation of watershed-based, multi-
stakeholder projects to reduce the impacts to public health from nitrogen and phosphorus
pollution contributing to HABs. EPA listed and described key elements of its plans for working
with partners and stakeholders over the next several years, including prioritizing watersheds and
setting load reduction goals, developing numeric nutrient criteria, reducing point sources of

67 EPA, Office of Water, FY2016-2017 National Water Program Guidance, EPA 420-R-15-008, April 2015,
https://www.epa.gov/sites/production/files/2015-04/documents/2016-2017_nwpg_final.pdf.
68 EPA, Office of Water, Actions to Help States Address Barriers to Numeric Nutrient Criteria Implementation, EPA
820-F-13-011, August 2013, https://www.epa.gov/nutrient-policy-data/actions-help-states-address-barriers-numeric-
nutrient-criteria-implementation.
69 Joel Beauvais, Deputy Assistant Administrator, EPA, memorandum to State Environmental Commissioners, State
Water Directors, “Renewed Call to Action to Reduce Nutrient Pollution and Support for Incremental Actions to Protect
Water Quality and Public Health,” September 22, 2016, https://www.epa.gov/nutrient-policy-data/renewed-call-action-
reduce-nutrient-pollution-and-support-incremental-actions.
70 Beauvais, “Renewed Call to Action to Reduce Nutrient Pollution.” EPA has approved approximately 74,000 TMDLs
in total since 1995 to address impairments from many different pollutant types. See https://ofmpub.epa.gov/waters10/
attains_nation_cy.control#tmdls_by_state.
71 Beauvais, “Renewed Call to Action to Reduce Nutrient Pollution.”
Congressional Research Service
21

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

nutrient pollution, reducing nutrient loads from nonpoint sources, and providing financial and
technical assistance.
For almost two decades, EPA has expressed support for developing numeric criteria for nutrients.
In a memorandum issued in 2011, EPA stated that “it has long been EPA’s position that numeric
criteria targeted at different categories of water bodies and informed by scientific understanding
of the relationship between nutrient loadings and water quality impairment are ultimately
necessary for effective state programs.”72 To this end, EPA has provided 30 states with technical
assistance for numeric nutrient criteria development through its Nutrient Scientific Technical
Exchange Partnership and Support Program.73 As of 2020, 23 states had adopted numeric criteria
into their water quality standards for nitrogen and/or phosphorus for at least one of their water
bodies.74 In 2013, EPA outlined barriers to numeric nutrient criteria implementation and actions to
help states address them.75 The barriers included, among other things, an inability to reduce
nonpoint source loads of nitrogen and phosphorus and problems implementing water-quality-
based limits.
On May 22, 2020, EPA announced the release of the Draft Ambient Water Quality Criteria
Recommendations for Lakes and Reservoirs of the Conterminous United States: Information
Supporting the Development of Numeric Nutrient Criteria
for public comment.76 According to
EPA, the draft criteria recommendations are part of the agency’s efforts to support states and
authorized tribes in developing and adopting numeric nutrient criteria. When finalized, the draft
criteria recommendations will replace EPA’s previously recommended ambient nutrient criteria
for lakes and reservoirs.77
EPA has also emphasized the need to focus on reducing nutrients from all sources—both point
and nonpoint sources.78 Under the CWA, EPA has authority to regulate discharges from point
sources.79 However, the CWA does not authorize EPA to regulate nonpoint sources. EPA can
influence activities of nonpoint sources only through use of grants and funding—such as CWA
Section 319, which addresses nonpoint source pollution through state-run nonpoint pollution
management programs—and related grants and technical assistance.80 Through such programs,
for example, states may ask farmers or ranchers to use alternative methods in their operations to
prevent fertilizers from reaching streams and may provide funds to help them install on-farm

72 Nancy K. Stoner, Acting Assistant Administrator, EPA, memorandum to Regional Administrators, Regions 1-10,
“Working in Partnership with States to Address Phosphorus and Nitrogen Pollution through Use of a Framework for
State Nutrient Reductions,” March 16, 2011, https://www.epa.gov/nutrient-policy-data/working-partnership-states-
address-phosphorus-and-nitrogen-pollution-through.
73 Beauvais, “Renewed Call to Action to Reduce Nutrient Pollution.”
74 EPA, “State Progress Toward Developing Numeric Nutrient Water Quality Criteria for Nitrogen and Phosphorus,”
https://www.epa.gov/nutrient-policy-data/state-progress-toward-developing-numeric-nutrient-water-quality-criteria.
One state (Hawaii) and three territories have adopted numeric criteria for nitrogen and phosphorus for all applicable
water types (lakes/reservoirs, rivers/streams, estuaries).
75 EPA, Actions to Help States Address Barriers.
76 EPA, “Draft Ambient Water Quality Criteria Recommendations for Lakes and Reservoirs of the Conterminous
United States: Information Supporting the Development of Numeric Nutrient Criteria,” 85 Federal Register 31184,
May 22, 2020.
77 EPA last published recommended numeric nutrient criteria for lakes and reservoirs for 12 out of 14 ecoregions from
2000 to 2001.
78 Beauvais, “Renewed Call to Action to Reduce Nutrient Pollution.”
79 CWA §402; 33 U.S.C. §1342.
80 While the 319 program is voluntary at the federal level, states may include regulatory components in their 319
programs.
Congressional Research Service
22

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

pollution management systems or practices. In its document addressing barriers to numeric
nutrient criteria, EPA proposed actions to address them, including continuing to collaborate with
the U.S. Department of Agriculture to leverage resources for conservation practices81 and to better
quantify the environmental results of best management practices and other efforts, continuing to
implement the Section 319 grant program, and addressing the challenges of manure management
by working with large animal growers and poultry integrators to develop sustainability
agreements and practices that reduce nutrient pollution.82
Some observers argue that the voluntary nature of controlling nonpoint sources is a key challenge
in developing and implementing TMDLs, a primary tool that states are employing to address
nutrient pollution. Farming and forestry groups have long been concerned about how their
activities might be addressed in TMDLs and whether they might be subject to CWA regulation of
some sort, even though the act does not provide EPA with regulatory authority over nonpoint
sources. Municipalities and industries contend that regulating only point sources imposes
disproportionate requirements on their operations, especially in waters that are impaired both by
point and nonpoint sources.
Federal Funding
Congress has authorized the use of funds under several CWA Sections for nutrient control
programs and activities. The President’s FY2021 budget request for EPA acknowledges that
HABs, “which can be caused by nutrient pollution, remain a widespread water quality challenge
across the country despite decades of effort to achieve reductions.”83 The FY2021 budget request
states that, while the President’s budget broadly continues the policy direction of prior years, it
proposes to provide funding to a focused set of emerging national and global environmental
challenges—one of which is reducing nutrients and HABs.84 The FY2021 budget request
proposes an additional $22.4 million to address and reduce HABs. This request includes $15
million to establish a new competitive grant program to target prevention and response actions for
HABs that pose significant health or economic risks.85 It also includes $2.9 million “to support
the advancement of a more comprehensive approach to addressing harmful algal blooms,
enhancing market mechanisms, and coordinating surveillance pilots, including through

81 A number of U.S. Department of Agriculture agencies provide support through education, outreach, and research,
while federal funds are provided through conservation programs to help agricultural producers adopt best management
practices for nutrient reduction. Examples of such programs include the Environmental Quality Incentives Program and
the Conservation Stewardship Program. For more information see CRS Report R43919, Nutrients in Agricultural
Production: A Water Quality Overview
, by Megan Stubbs.
82 EPA, Actions to Help States Address Barriers.
83 EPA, Fiscal Year 2021 Justification of Appropriation Estimates for the Committee on Appropriations, EPA-190-S-
20-001, February 2020, p. 602, https://www.epa.gov/sites/production/files/2020-02/documents/fy-2021-congressional-
justification-all-tabs.pdf.
84 EPA, Fiscal Year 2021 Justification, pp. iii-iv.
85 EPA, Fiscal Year 2021 Justification, pp. 602-603. EPA cites the CWA and HABHRCA 2017 as the statutory
authority for the new grant program. According to EPA, “funded projects should further the implementation of HAB-
specific state nutrient reduction strategies and programs and should include one or more of the following strategic
outputs and outcomes: prioritization of high impact watersheds; goal setting to support targeting and tracking of
implementation efforts; identification and adoption of state-level actions and programs to better prevent and respond to
HABs; deployment of staff to plan, prioritize, engage partners and stakeholders in priority watersheds, and manage
progress tracking mechanisms; assessment of progress; and reporting and communicating of state progress to the
public. State workplans also could support other priority actions identified in a harmful algal bloom strategy or
program, including developing or implementing a trading program; modeling and monitoring harmful algal blooms;
and watershed planning support.”
Congressional Research Service
23

link to page 29 link to page 29 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Interagency Agreements with other federal partners to better predict HABs.”86 It also includes
$1.2 million “to provide data standards and geo-referencing expertise for EPA’s research,
predictive modeling and monitoring tools and analyses, and policy approaches to target and
reduce nutrient pollution that causes HABs and impacts water quality across the country.”87
However, the President’s FY2021 budget request for EPA proposes that funding for most of the
programs EPA has long relied on to address nonpoint source pollution be eliminated or
significantly reduced (see Table 8).88 These programs include the CWA Section 106 and Section
319 grant programs and the Clean Water State Revolving Fund (CWSRF) Program,89 as well as
Section 604(b) planning grants,90 Wetland Program Development grants, and grants targeted
toward specific geographic locations, such as the Chesapeake Bay, Great Lakes, and other water
bodies. The President’s FY2018-FY2020 budget requests similarly proposed that funding for
most of these programs be eliminated or significantly reduced, but Congress maintained and/or
increased the funding for these programs in each of these fiscal years. Although the FY2021
budget request for EPA includes an increase of $22.4 million to address and reduce HABs, it is
unclear how the proposed reductions to other programs that address nonpoint source pollution
would support the agency’s goals to reduce nutrient pollution, and ultimately reduce the
occurrence and frequency of HABs.91
Table 8 presents a comparison of the President’s FY2021 budget request with the FY2016-
FY2020 enacted appropriations for selected grants and programs referenced above that include
funding support for addressing nonpoint source pollution. These grants and programs are funded
within the EPA State and Tribal Assistance Grants and the Environmental Programs and
Management appropriations accounts.


86 EPA, Fiscal Year 2021 Justification, p. 21.
87 EPA, Fiscal Year 2021 Justification, p. 61.
88 EPA, Fiscal Year 2021 Justification, pp. 643, 805, 810-811. EPA has provided financial assistance to states for
nutrient control projects and activities through CWA Section 106 and Section 319 grant programs and the Clean Water
State Revolving Fund (CWSRF) Program, as well as Section 604(b) planning grants, Wetland Program Development
grants, and grants targeted toward specific geographic locations, such as the Chesapeake Bay, Great Lakes, and other
water bodies. See, for example, memorandum issued by the Office of Water, Beauvais, “Renewed Call to Action to
Reduce Nutrient Pollution,” 2016.
89 The proportion of funds provided to nonpoint source pollution projects through the CWSRF program has been
relatively minor compared to the amount provided to publicly owned treatment works for infrastructure projects. As
reported by EPA, most of the cumulative assistance provided through the CWSRF, through 2019, was provided to
publicly owned treatment works. Roughly 4% was provided to nonpoint source and other projects, such as agricultural
best management practices, silviculture, estuary assistance, and land conservation. EPA, Clean Water SRF Program
Information National Summary
, National Information Management System Report, March 17, 2020, pp. 24, 28,
https://www.epa.gov/sites/production/files/2020-03/documents/us19r.pdf.
90 CWA Section 604(b) requires states to reserve a small portion of each its CWSRF allotment each fiscal year—1%
for most states—to carry out planning under CWA Sections 205(j) and 303(e). States generally use Section 604(b)
grants to fund regional comprehensive water quality management planning activities to improve local water quality.
91 EPA, Fiscal Year 2021 Justification, p. 706. One of EPA’s goals, newly identified in the FY2021 budget request, is
to decrease the square mileage of watersheds with surface waters not meeting water quality standards because of
nutrients.
Congressional Research Service
24

link to page 30 link to page 30 link to page 30 link to page 30 link to page 30 link to page 30 link to page 30 link to page 30 link to page 30 link to page 30 Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

Table 8. FY2016-FY2020 Enacted Appropriations and FY2021 Requested
for Selected EPA Grants and Programs That Include Assistance to
Address Nonpoint Source Pollution
(Dollars in Millions)
FY2021
EPA Appropriations Acct.
FY2016
FY2017
FY2018
FY2019
FY2020
Budget
and Grants/Programs
Enacteda
Enacteda
Enacteda
Enacteda Enacteda
Request
State and Tribal Assistance Grants Account
Infrastructure Assistance





Clean Water State Revolving
$1,393.9
$1,393.9 $1,693.9c
$1,394.0
$1,638.8
$1,119.8
Fund Programb
Categorical Grants





CWA Section 106 Grants
$230.8
$230.8
$230.8
$230.8
$223.3
$153.7
CWA Section 319 Grants
$164.9
$170.9
$170.9
$170.9
$172.3
$0.0
Wetland Program
$14.7
$14.7
$14.7
$14.7
$14.2
$9.8
Development Grants
Nutrient and Harmful Algal





$15.0
Blooms Reduction Grantsd
Environmental Programs and Management Account
Geographic Programse

Chesapeake Bay Program
$73.0
$73.0
$73.0
$73.0
$85.0
$7.3
Great Lakes Restoration
$300.0
$300.0
$300.0
$300.0
$320.0
$320.0
Program
Gulf of Mexico Program
$4.5
$8.5
$12.5
$14.5
$17.6
$0.0
Lake Champlain
$4.4
$4.4
$8.4
$11.0
$13.4
$0.0
Long Island Sound
$3.9
$8.0
$12.0
$14.0
$21.0
$0.0
Puget Sound Program
$28.0
$28.0
$28.0
$28.0
$33.0
$0.0
South Florida Program
$1.7
$1.7
$1.7
$3.2
$4.8
$3.2
San Francisco Bay
$4.8
$4.8
$4.8
$4.8
$5.9
$0.0
Lake Pontchartrain
$0.9
$0.9
$0.9
$0.9
$1.4
$0.0
Southern New England
$5.0
$5.0
$5.0
$5.0
$5.4
$0.0
Estuaries
Columbia River Basinf



$1.0
$1.2
$0.0
Other Geographic Activities
$1.4
$1.4
$1.4
$1.4
$1.5
$0.0
Sources: FY2016 enacted amounts are as reported in the “Explanatory Statement” accompanying the
Consolidated Appropriations Act, 2017 (P.L. 115-31), as published in the Congressional Record, vol. 163, no. 76-
Book II (May 3, 2017), https://www.gpo.gov/fdsys/pkg/CREC-2017-05-03/pdf/CREC-2017-05-03-bk2.pdf. Under
Division G, see the funding tables beginning p. H3922 and p. H3926.
FY2017 enacted amounts are as reported in the “Explanatory Statement” accompanying the (P.L. 115-141), as
published in the Congressional Record, vol. 164, no. 50-Book II (March 22, 2018), https://www.congress.gov/crec/
2018/03/22/CREC-2018-03-22-bk2.pdf. Under Division G, see the funding tables beginning p. H2667 and p.
H2671.
Congressional Research Service
25

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

FY2018 enacted amounts are as reported in the “Explanatory Statement” accompanying the Consolidated
Appropriations Act, 2019 (P.L. 116-6), as published in H.Rept. 116-9. See the funding tables beginning on p. 795
and p. 800.
FY2019 and FY2020 enacted amounts are as reported in the “Explanatory Statement” accompanying the
Consolidated Appropriations Act, 2020 (P.L. 116-94), as published in the Congressional Record, vol. 165, no. 204-
Book III, available at https://www.govinfo.gov/content/pkg/CREC-2019-12-17/pdf/CREC-2019-12-17-house-
bk3.pdf. Under Division D, see the funding tables on pp. H11335, H11339, and H11341.
FY2021 requested amounts are as reported in EPA’s Fiscal Year 2021 Justification of Appropriation Estimates for the
Committee on Appropriations
, EPA-190-S-20-001, February 2020, pp. 643, 805, 810-811, https://www.epa.gov/sites/
production/files/2020-02/documents/fy-2021-congressional-justification-all-tabs.pdf.
Notes: Most of these grants provide financial assistance that supports and addresses many water quality
improvement projects and other activities in addition to nonpoint source pol ution.
a. Amounts presented in the table do not reflect account specific rescissions for relevant fiscal years.
b. The proportion of funds provided to nonpoint source pol ution projects through the CWSRF is relatively
minor compared to the amount provided to publicly owned treatment works for infrastructure projects. As
reported by EPA, roughly 4% of the cumulative assistance provided through the CWSRF as of 2019 was
provided to nonpoint source and other projects, such as agricultural best management practices,
silviculture, estuary assistance, and land conservation.
c. The FY2018 enacted amount for the Clean Water State Revolving Fund Program includes an additional
$300 mil ion provided under Title IV of P.L. 115-141.
d. EPA proposes to establish the Nutrient and Harmful Algal Blooms Reductions Grant Program in the
President’s FY2021 budget request for EPA.
e. Although some of the geographic programs’ water bodies are estuarine in nature (outside the scope of this
report), their watersheds include freshwater sources. Funding may therefore support efforts to reduce
nonpoint source pol ution contributions to the freshwater sources.
f.
In 2016, Congress authorized the Columbia River Basin program in the Water Infrastructure Improvements
for the Nation Act (P.L. 114-322), but did not include an authorization of appropriations for the program. In
2018, Congress amended the CWA to add an authorization of appropriations for the program in America’s
Water Infrastructure Act (P.L. 115-270).
Research Gaps
In addition to the challenges of reducing nutrient pollution contributing to HABs, scientists
widely recognize key research gaps that hinder the ability to prevent, predict, minimize, and
suppress HABs. In reauthorizing HABHRCA in 2014, as discussed above, Congress directed
NOAA—through the IWG-HABHRCA—to prepare a comprehensive research plan and action
strategy to address marine and freshwater harmful algal blooms and hypoxia. The February 2016
task force report92 includes a discussion of the key challenges in HAB and hypoxia management
and discusses the many gaps in the research and management communities’ knowledge of HAB
and hypoxia events. Federal agencies—including the U.S. Geological Survey,93 EPA,94 and

92 National Science and Technology Council, Subcommittee on Ocean Science and Technology, Harmful Algal Blooms
and Hypoxia Comprehensive Research Plan and Action Strategy
.
93 Graham et al., Cyanobacterial Harmful Algal Blooms.
94 Lesley V. D’Anglada, EPA, “Editorial on the Special Issue ‘Harmful Algal Blooms (HABs) and Public Health:
Progress and Current Challenges,’” Toxins, vol. 7 (October 2015), pp. 4437-4441. Also, EPA’s solicitation for grant
proposals regarding HABs lists specific research gaps the applications should address. EPA “Freshwater Harmful Algal
Blooms,” Funding Opportunity Announcement Number EPA-G2017-STAR-A1, Office of Research and Development,
October 28, 2016.
Congressional Research Service
26

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

NOAA95—and research efforts sponsored by these agencies cite similar gaps and areas needing
continuing research. The following text box summarizes some of these key research areas.
HAB Research Gaps

Ability to predict the timing, species composition, and toxicity of HABs (including the environmental triggers
for toxicity)

More information on the influence that excess nutrients and other factors (e.g., climate) play in the
occurrence and distribution of HABs

Need to strengthen and integrate new and existing monitoring programs (i.e., expand river, stream, and
watershed monitoring of nutrients and toxins, coupled with increased modeling information)

Need to develop standardized and validated detection and analysis methods for algal toxins

Need for more effective methods for suppressing, mitigating, or control ing HABs

Need to understand less-common HAB species that produce toxins

Better understanding of the human health effects of HAB exposure

Better understanding of the environmental, economic, and social impacts of HABs

Improvements in public outreach and communication strategies and tools
Legislation in the 116th Congress
Congressional interest in freshwater HABs has largely focused on funding further research,
improving monitoring of HABs, and coordinating the efforts of federal agencies and their
partners to study and address HABs. Some of the bills Members have introduced in recent years
have focused specifically on marine HABs or on freshwater HABs, and some have addressed
both. HAB-related bills introduced in the 116th Congress that focus on freshwater HABs or HABs
generally include the following:
 H.R. 335 and S. 10, identical bills titled the “South Florida Clean Coastal Waters
Act of 2019,” would require the IWG-HABHRCA to prepare an integrated
assessment and a plan for HABs and hypoxia in south Florida, similar to what the
working group has completed at a national level and for the Great Lakes region.
 H.R. 414, the “Protecting Local Communities from Harmful Algal Blooms Act,”
would amend the Robert T. Stafford Disaster Relief and Emergency Assistance
Act96 to include algal blooms in the definition of major disaster.
 H.R. 729, the “Coastal and Great Lakes Communities Enhancement Act,” which
passed the House in December 2019, includes a number of HAB-related
provisions. For example, the bill would authorize the director of the U.S.
Geological Survey to conduct monitoring, assessment, science, and research, in
support of the binational fisheries within the Great Lakes Basin. The bill provides
a number of focus areas for these efforts, including HAB development research.
The bill would also reauthorize appropriations for the National Sea Grant College
program, and would provide an additional authorization of appropriations for
competitive grants for several specific research areas, including the biology
prevention, and forecasting of HABs. The bill would also would include projects

95 NOAA, State of the Science Fact Sheet—Harmful Algal Blooms, April 2019, https://nrc.noaa.gov/sites/nrc/
Documents/SoS%20Fact%20Sheets/SoS_Fact_Sheet_HAB_FINAL_apr2019.pdf?ver=2019-05-01-171513-573.
96 42 U.S.C. §5121 et seq.
Congressional Research Service
27

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

to address HABs under the proposed Climate Change Adaptation Preparedness
and Response Program.
 H.R. 1243 and S. 523, companion bills titled the “Climate Change Health
Protection and Promotion Act of 2019,” would direct the Secretary of Health and
Human Services to develop a national strategic plan and program to prepare for
and respond to the public health effects of climate change. The bill states that the
plan shall include an assessment of the health system capacity of the United
States to address climate change including developing, improving, integrating,
and maintaining surveillance systems and monitoring capacity to respond to
health-related impacts of climate change, including on HABs (among other
topics).
 H.R. 2405 and S. 910 (H.Rept. 116-323), companion bills titled the “National
Sea Grant College Program Amendments Act of 2019,” would reauthorize and
amend the National Sea Grant College Program Act, which would continue to
make funds available for HAB research through competitive grants.
 H.Amdt. 284—included in the House-passed version of the Labor, Health and
Human Services, Education, Defense, State, Foreign Operations, and Energy and
Water Development Appropriations Act, 2020 (H.R. 2740)—would direct the
National Institutes of Health to designate $6.25 million to research the long-term
effects of red tide and other HABs on human health.
 H.R. 3297, the “Harmful Algal Bloom Essential Forecasting Act,” would amend
HABHRCA to clarify that during a lapse in appropriations, certain services
relating to the HAB Operational Forecasting System are excepted services under
the Anti-Deficiency Act.
 H.R. 3324, the “Prioritizing Revised Operations to Eliminate Cyanobacteria
Toxins in Florida Act,” would, among other things, require the Army Corps of
Engineers to modify operations of projects in central and south Florida to ensure
that “public health” overlays all authorized project purposes. The bill defines
public health to include managing Lake Okeechobee and the central and southern
Florida system in a way that minimizes HABs and prevents discharges containing
cyanobacteria and their toxins into the St. Lucie and Caloosahatchee watersheds,
among other goals.
 H.R. 3548, the “Bolstering Long-Term Understanding and Exploration of the
Great Lakes, Oceans, Bays, and Estuaries Act,” and S. 933, the “Bolstering
Long-Term Understanding and Exploration of the Great Lakes, Oceans, Bays,
and Estuaries Act” or the “BLUE GLOBE Act,” would establish Ocean
Innovation Prizes to “catalyze the rapid development and deployment of data
collection and monitoring technology related to the Great Lakes, oceans, bays,
estuaries, and coasts” in at least one of several specified areas. One of the
specified areas is water quality monitoring, including improved detection and
prediction of HABs and pollution.
 H.R. 5548, the “Fishery Failures: Urgently Needed Disaster Declarations Act,”
would identify HABs as a natural cause that may qualify for fishery resource
disaster aid.
 S. 914, the “Coordinated Ocean Observations and Research Act of 2019,” would
reauthorize the Integrated Coastal and Ocean Observation System Act of 2009.
Specific to HABs, the bill would add, as a purpose of the system, a focus on
monitoring and modeling “changes in the oceans and Great Lakes, including with
Congressional Research Service
28

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations

respect to chemistry, harmful algal blooms, hypoxia, water levels, and other
phenomena.” The bill also includes HAB-related provisions that pertain more
specifically to marine ecosystems.
 S. 2209, the “Commercial Fishing and Aquaculture Protection Act of 2019,”
would authorize the Secretary of Commerce to provide compensation to eligible
commercial fisherman and farm-raised fish producers that have incurred eligible
losses due to eligible loss conditions. Such conditions, as defined in the bill,
would include HABs.
Conclusion
Recent HAB events highlight the public health, economic, and environmental consequences that
communities in the United States may continue to experience, perhaps on a more frequent basis.
EPA, NOAA, and other federal agencies are working together to conduct important HAB-related
research in an effort to close the gaps in the scientific and management community’s
understanding of how best to prevent, predict, minimize, and suppress HABs. EPA, states, and
their partners are working to identify and restore waterbodies that are affected by HABs and the
excess nutrients that contribute to their formation. Congress has passed legislation to help drive
and fund research efforts and improve collaboration among the many federal agencies involved in
HAB-related activities. Moving forward, Congress may be interested in oversight of the
Administration’s efforts to implement HABHRCA and other HAB-related authorities. While
Congress, federal agencies, and states are taking steps to address HABs, many observers assert
that further action is needed to make progress that outpaces the growing consequences of nutrient
pollution.
Most observers agree that further research is needed to understand the most appropriate way to
predict, minimize, and suppress HAB outbreaks, including whether and how to regulate algal
toxins. These advocates assert that Congress should ensure that adequate funding is available for
such research. To control HABs, some advocate for regulation of nonpoint source pollution,
arguing that point sources are disproportionately regulated and that nonpoint sources are the
larger contributors to nutrient pollution. Instead of regulation, some argue that EPA and other
federal agencies should continue to focus on collaborative, voluntary watershed-level efforts to
address nonpoint source pollution that contributes to HAB formation and that Congress should
ensure that financial assistance for these efforts continues.
Controlling nonpoint sources of excess nutrients that contribute to HAB formation is challenging.
Nutrient pollution is diffuse and pervasive and often attributable to many sources and activities
rather than a single cause. Yet, scientists generally agree that the current trends in increasing
numbers of overenriched waters and HAB events cannot be corrected without addressing
nonpoint source nutrient pollution in a significant way and that controlling point sources alone is
not enough. Given the consequences of HABs and the difficulty in controlling nonpoint sources
of the nutrients that contribute to their formation, challenges and issues associated with HABs are
likely to remain of interest to Congress.

Congressional Research Service
29

Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations


Author Information

Laura Gatz

Analyst in Environmental Policy



Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan
shared staff to congressional committees and Members of Congress. It operates solely at the behest of and
under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other
than public understanding of information that has been provided by CRS to Members of Congress in
connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not
subject to copyright protection in the United States. Any CRS Report may be reproduced and distributed in
its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or
material from a third party, you may need to obtain the permission of the copyright holder if you wish to
copy or otherwise use copyrighted material.

Congressional Research Service
R44871 · VERSION 10 · UPDATED
30