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

In Florida, the presence of elevated specific conductance levels in fresh surface watersoften indicate that substantial discharges of groundwater — usually from theIntermediate or Floridan aquifers — are occurring at locations upstream of the samplingpoint. Agricultural and industrial operations are the most common sources of suchgroundwater discharges.Un-Ionized AmmoniaThe un-ionized form of ammonia is highly toxic to fish and other aquatic organisms. Inwater, ionized (NH 4 + ) and un-ionized (NH 3 ) ammonia exist in a dynamic chemicalequilibrium, with the un-ionized form becoming increasingly common at highertemperature and pH levels.The Florida water quality standard for un-ionized ammonia is 0.02 mg NH 3 /L. Levelsexceeding the standard were observed at two stations during water years 1998 – 2001:• Saddle Creek at Structure P-11 (in water years 2000 and 2001)• Horse Creek near Myakka Head (2000).Levels of un-ionized ammonia that were relatively high (>0.01 mg NH 3 /L) but did notexceed the water quality standard were also observed at several other stations,including:• Peace River at Zolfo Springs (2000, 2001)• Shell Creek near Punta Gorda (2001)• Myakka River at Myakka City (1999)• Big Slough Canal near Myakka City (1999)• Big Slough Canal near North Port (1999)The ammonia nitrogen found in rivers and streams can come from a variety of naturaland manmade sources. Exceedances of the un-ionized ammonia water qualitystandard are often associated with discharges from anthropogenic activities, includingfeedlots and other concentrated animal feeding operations, sewage treatment systems,and industrial facilities that make or use ammonia-based chemical products.Dissolved OxygenDissolved oxygen (DO) is a critical water quality parameter, due to the importance ofDO to the metabolic processes of all multi-celled aquatic organisms.DO concentrations fluctuate as a result of a number of natural and man-made factors.Important natural factors include seasonal and daily temperature cycles (because thesolubility of oxygen in water is higher at lower water temperatures), photosynthesis(because photosynthesizing organisms release DO into the water column, increasing itsavailability) and respiration/decomposition processes (which consume oxygen and thuscause DO concentrations in the water column to decline).vi