According to a recently released national study by the U.S. Geological Survey, elevated concentrations of nitrogen and phosphorus have remained the same or increased in many streams and aquifers across the nation since the early 1990s.
In a statement, USGS Associate Director for Water Matthew Larsen said, “Despite major Federal, State and local efforts and expenditures to control sources and movement of nutrients within our Nation’s watersheds, national-scale progress was not evident in this assessment, which is based on thousands of measurements and hundreds of studies across the country from the 1990′s and early 2000′s.”
On the USGS website, the study is described as a “comprehensive national analysis of nutrients in streams and groundwater from 1992 through 2004.”
From a press release detailing the findings:
USGS findings show that widespread concentrations of nitrogen and phosphorus remain two to ten times greater than levels recommended by the EPA to protect aquatic life. Most often, these elevated levels were found in agricultural and urban streams. These findings show that continued reductions in nutrient sources and implementation of land-management strategies for reducing nutrient delivery to streams are needed to meet EPA recommended levels in most regions.
Nutrients occur naturally in water and are needed for plant growth and productive aquatic ecosystems; however, in high concentrations nutrients often result in the growth of large amounts of algae and other nuisance plants in streams, lakes and estuaries. The decay of these plants and algae can cause areas of low dissolved oxygen, known as hypoxic, or “dead,” zones that stress or kill aquatic life. Some forms of algae release toxins that can result in health concerns.
Nitrogen and phosphorus are two well-known culprits behind widespread algal blooms, fish kills and a bizarre foam in the lower St. Johns River basin. The EPA’s numeric nutrient standard criteria, which are still being developed, would establish rules to govern Florida waterbodies like the St. Johns.
The USGS study’s fact sheet seems to support the implementation of a set of stricter criteria to govern waterbodies like the unhealthy St. Johns: “The wide range in biological response to nutrient concentrations supports the need for a regional approach to nutrient criteria and for consideration of local factors related to stream habitat and flow characteristics in the development of these criteria.”