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

• 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 anthropogenic activities, such as feedlots and otherconcentrated animal feeding operations, sewage treatment systems and industrialfacilities 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 are affected by a number of natural and man-made factors.Important natural factors include daily and seasonal 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 cause DO concentrationsin the water column to decline).The primary manmade influences include the discharge of nutrients and organic wastesinto waterbodies, which can lead to increased eutrophication, higher rates ofphotosynthesis, respiration and decomposition, and larger daily and seasonalfluctuations in DO concentrations.The Florida standard for DO in fresh surface waters is 5 mgL/. Concentrations below 4mg/L are known to be stressful for most fish and many shellfish species.Concentrations below 2 mg/L are highly stressful and potentially lethal.During water years 1998 through 2001, DO concentrations below the 5 mg/L standardwere observed at least once at each station. Many of these instances were probablyassociated with natural factors, such as elevated water temperature. At severalstations, however, low DO levels were a frequent occurrence, observed on 25% or moreof the sampling dates. And for some stations the median annual DO concentration (thevalue measured on at least half the sampling dates in a given year) was less than the 5mg/L standard. The latter group of stations included:• Peace Creek Canal near Wahneta (water years 1998, 1999, 2000, and 2001)• Saddle Creek at Structure P-11 (1999, 2001)• Peace River at Bartow (1998, 1999, 2000, 2001)• Shell Creek near Punta Gorda (1998)• Deer Prairie Slough near North Port (2000, 2001)• Big Slough Canal near North Port (2001).The frequent periods of low DO availability occurring at these stations presumably hadnegative impacts on local populations of fish and other aquatic organisms.13