Applied Ecosystem Services, LLC

The EPA, and many state regulators, consider aquatic life to be the highest designated beneficial use of water. Closely related to this water quality standard is “fishable and swimmable”. The latter is easier to define and to assess attainment: if fish are present all water quality variables suit their needs; when there are no human parasites or known toxic chemicals water quality is swimmable. The aquatic life water quality standard is not as easy to define and measure.

The EPA requires states to protect designated beneficial uses of water such as municipal water supplies; protection of fish, shellfish, and wildlife; and recreational, agricultural, industrial, and navigational purposes. States are required to examine the suitability of a water body for designated uses based on physical, chemical, and biological characteristics as well as its geographical setting, scenic qualities, and economic considerations. EPA’s highest designated use is “fishable/swimmable”. All designated uses are to be assessed to determine whether they do, or can, attain suitable quality.

Dissolved metals such as copper, cadmium, and zinc can be toxic to aquatic life, particularly fish. The current tool used to estimate site-specific water quality criteria for a metal is the biotic ligand model (BLM). The BLM intends to quantify how water chemistry affects speciation and biological availability of metals in aquatic ecosystems. This is important because bioavailability and bioreactivity of metals control their potential for acute or chronic harm. A BLM incorporates aquatic chemistry, fish physiology, and ecotoxicology but not ecology.