Peace and Myakka River Water Quality Summary 2002 - Southwest ...

ased on a fundamentally different sampling design that was scheduled to begin during2001.1.2 WATER QUALITY MANAGEMENT ISSUESThe Peace and Myakka River basins lie in a naturally fertile area that contains extensivephosphate-bearing geological deposits (the Bone Valley formation of the Hawthorngroup) and experiences abundant seasonal rainfall and a humid subtropical climate.Phosphate is an important nutrient supporting the growth of terrestrial and aquaticorganisms, and many lakes and streams that drain the Bone Valley region are“eutrophic” (exhibit high rates of biological productivity) as a result of naturally elevatedphosphate inputs (Odum 1953, Canfield and Hoyer 1988). These naturally eutrophicwaterbodies have the potential to become hypereutrophic — exhibiting undesirably highlevels of biological productivity — if human activities cause nutrient loads to increase toexcessive levels. Several historically-eutrophic lakes located in the headwaters regionof the Peace River basin (e.g., Lake Parker, Lake Hancock, Banana Lake) appear tohave shifted to hypereutrophic productivity levels in recent decades as a result ofadditional, manmade nutrient loads.Eutrophication is a process in which increasing nutrient loads cause changes in thewater chemistry and ecological structure of surface water bodies (Day et al. 1989).These changes, which are currently affecting many Florida waters, often include:• increasing rates of biological production, and increasing biomass of algae orrooted aquatic plants;• increasing deposition of unutilized organic material to the sediment zone (withassociated increases in sediment oxygen demand);• reduced water clarity, due to increased algal densities and resuspension ofunconsolidated bottom sediments; and• shifts in the composition of plant and animal communities, with increasingabundance of species more highly adapted to nutrient-enriched conditionsIn addition to ecological and esthetic impacts, excessive nutrient loads can also affecthuman uses of surface waters by increasing the frequency of nuisance algal blooms,causing taste and odor problems in potable water sources and contributing to oxygenrelatedstress or mortality in economically important fish and shellfish species.From a regulatory perspective the Federal Water Pollution Control Act (“Clean WaterAct”), as amended, provides the underlying legal framework for water qualitymanagement throughout the United States. The Clean Water Act requires that thechemical, physical and biological integrity of the Nation’s waters be maintained at levelsthat provide “fishable and swimmable” conditions for all citizens. Regulations developedby the U.S. EPA and other agencies to implement the Act have therefore focused on2