The States and Tribes are responsible for designating their lakes for specific uses, but EPA requests that the States and Tribes rate how well their lakes support six standard uses so that EPA can summarize the State and Tribal data. Many States and Tribes did not rate fish consumption use support because they have not codified fish consumption as a use in their standards. Some of these States consider fishing use as a component of aquatic life use - lakes that provide a healthy habitat for fish support fishing activities even though anglers may not be able to eat their catch in these States. EPA encourages the States to designate fish consumption as a separate use in their waterbodies to promote consistency in future reporting. In some cases, a State may recognize that water quality does not fully support a designated use, but the State may not have adequate data to document that a specific pollutant or stressor is responsible for the impairment.
Sources are even more difficult to identify than pollutants and stressors.
EPA ranks the pollutants and processes by the extent of their impacts on aquatic life and human activities rather than actual pollutant loads in lakes. This approach targets the pollutants and processes causing the most harm to aquatic life and public use of our waters rather than the most abundant pollutants in our lakes, reservoirs, and ponds. When temperature and light conditions are favorable, excessive nutrients stimulate population explosions of undesirable algae and aquatic weeds. The algae sink to the lake bottom after they die, where bacteria consume the available dissolved oxygen as the bacteria decompose the algae. Fish kills and foul odors may result if dissolved oxygen is depleted.