	Introduction

Scientific research indicates that in recent years, the frequency and geographic distribution of harmful algal blooms (HABs) have been increasing nationally and globally. HABs can be detrimental to human health, animals, aquatic ecosystems, and local economies. 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. 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. 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. Some species of cyanobacteria produce toxins, called cyanotoxins, which can cause hepatic (liver-related), neurologic, respiratory, dermatologic, and other symptoms. In addition to the effects of algal toxins on human and animal health, HABs can also contribute to deteriorating water quality and ecosystem health. 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. Nutrient enrichment is widely recognized as one of the key causes of HAB formation. Nutrients, such as nitrogen and phosphorus, are essential to plant growth and natural parts of aquatic ecosystems. HABs, including cyanobacterial HABs, have been recorded in the waters of all 50 states, with some HABs crossing state lines. 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. 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. In addition to HAB-specific legislation, the Clean Water Act (CWA) authorizes EPA to address water quality concerns associated with HABs. 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. 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. Environmental groups generally supported EPA's criteria for use in both swimming advisories and development of water quality standards. 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 EPA, 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. EPA has also emphasized the need to focus on reducing nutrients from all sources—both point and nonpoint sources. Under the CWA, EPA has authority to regulate discharges from point sources. However, the CWA does not authorize EPA to regulate nonpoint sources. Federal Financial Assistance

Recognizing that a critical role for EPA in addressing nutrient pollution is supporting watershed-based efforts at the state and local level, in its 2016 memorandum, the agency stated that the Office of Water would continue to provide financial assistance to states 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. The President's FY2019 budget request for EPA proposes that funding for these programs, with the exception of the CWSRF, be eliminated or significantly reduced (see Table 8 ). Legislation in the 115th Congress

Congressional interest in HABs has largely focused on funding further research and coordinating the efforts of federal agencies and their partners to study and address HABs. Controlling nonpoint sources of excess nutrients that contribute to HAB formation is challenging.
Scientific research indicates that in recent years, the frequency and geographic distribution of harmful algal blooms (HABs) have been increasing nationally and 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 December 2016, the Environmental Protection Agency (EPA) used its authority under the Clean Water Act (CWA) to propose water quality criteria for two algal toxins in waters used for recreational purposes. States use 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.
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 quality and HAB formation. Congress has long provided financial assistance through EPA for regional, state, and local programs through CWA Sections 106 and 319 planning grants, geographic programs (such as the Chesapeake Bay and Great Lakes), and other sources. The President's FY2019 budget request for most of these programs is either eliminated or significantly reduced.
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.