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

Median color values for Florida rivers and estuaries, as reported by Friedemann andHand (1989) based on a survey of several thousand records retrieved from the U.S.EPA STORET database, are 70.0 and 20.0 pcu, respectively. Values observed in thetidal reaches of the Peace and Myakka river systems during water years 1994-2000(Appendix B) were substantially higher than these statewide medians.Near-Surface TSSConcentrations of total suspended solids (TSS) reflect levels of organic and inorganicparticulate matter present in the water column. High levels of TSS can impact thequality of aquatic habitats by reducing water clarity and light penetration, thus affectingthe growth of algae and rooted aquatic plants. Areas of high TSS deposition andresuspension are often sub-optimal habitats for many aquatic organisms, due to foulingand smothering effects and reductions in dissolved oxygen availability that can occur asa result of elevated sediment oxygen demand.Annual median near-surface TSS values in the tidal Peace and Myakka river samplesranged between 3 and 36 mg/L, with the higher values occurring at the moredownstream stations (Appendix B). Median values for Florida rivers and estuariesreported by Friedemann and Hand (1989) are 7.0 and 17.5 mg/L, respectively. With theexception of relatively high values observed at several stations during the 2000 wateryear, TSS concentrations at the tidal Peace and Myakka River monitoring sites do notappear to be elevated with respect to other Florida water bodies.Near-Surface TurbidityTurbidity is an expression of the optical property that causes light to be scattered andabsorbed rather than transmitted in straight lines through a water sample. It is primarilycaused by suspended matter (e.g., clay, silt, and finely-divided organic and inorganicmaterials), soluble colored organic compounds, and plankton and other microscopicorganisms (APHA 1989).Annual median values measured at the tidal Peace-Myakka monitoring stations duringwater years 1994 - 2000 ranged between 1.7 and 7.3 NTU, with the highest valuesoccurring at the most upstream stations on both rivers (Appendix B).Turbidity measurements can be affected by high levels of water color, apparently due tolight absorption by the dissolved substances that are also responsible for color (APHA1989). Because the tidal Peace and Myakka are highly colored river systems,comparisons of turbidity measurements from these areas with measurements fromother rivers, with different color characteristics, should be done with caution.53