by seasonal fires. However, as 



regional drainage operations amplify 

 natural drought extremes, these 

 communities are beginning to suffer 

 from fires as well (Hofstetter 1973, 

 Hilsenbeck et al. 1979). 



In Chapter 5 (surface hydrology 

 and water quality) it was pointed 

 out that the Everglades marshes 

 empirically act as traps for sedi- 

 ments, nutrients, heavy metals, and 

 pesticides (Waller and Earle 1975). 

 Unfortunately the flux of these 

 materials through the soils, vege- 

 tation, and biota is relatively 

 unstudied. Exceptions to this are 

 Steward (1974) on sawgrass physiol- 

 ogy, and Kolipinski and Higer (1969) 

 on pesticide residues in selected 

 Everglades biota. 



Steward (1974), working north 

 of the study area, estimated that 

 the nutrient requirements of saw- 

 grass are low primarily because 

 tissue levels are low when compared 

 to other species of Everglades 

 macrophytes. Another line of rea- 

 soning suggests that the highly 

 organic soils effectively bind nu- 

 trients and render them unavailable 

 for uptake. No seasonal patterns of 

 nutrient and inorganic ion concen- 

 trations in soils were reported. 

 Standing crops and plant density of 

 immature stands showed little sea- 

 sonal variation. Nutrients in marsh 

 waters were generally in adequate 

 supply averaging 3%, 10%, and 8% of 

 nitrogen, phosphorous, and potassium 

 respectively. 



With regard to tissue concen- 

 trations of nutrients and inorganic 

 ions in mature stands, little sea- 

 sonality was evident. A possible 

 exception to this was nitrogen, 

 which was notably higher from Decem- 

 ber through April. In fire recovery 

 stands initial growth was more rapid 

 than in immature stands but leveled 



off with age. Tissue concentrations 

 of nitrogen, phosphorus, magnesium, 

 potassium, copper, and manganese 

 were initially high in rapidly grow- 

 ing plants but decreased over time. 

 Calcium and iron showed the reverse 

 trend. Steward attributed the rela- 

 tive success of sawgrass in the 

 Everglades to a combination of its 

 low nutrient requirements and the 

 lack of direct grazing. 



Distributions of persistent 

 pesticides in fish and wildlife 

 often provide a stark confirmation 

 of invisible energy and material 

 flow pathways. Kolipinski and Higer 

 (1969) report that despite extremely 

 low levels in ambient waters in the 

 Everglades, the algal mats, macro- 

 scopic plants, and organic detrital 

 pool concentrate DDT congeners to 

 the microgram per kilogram level 

 (trace - 200 ug/mg). At the level 

 of primary carnivore, the mosquito 

 fish ( Gambusia affinis ) exhibited 

 concentrations as high as 700 ug/kg. 

 In the eggshells of the Everglades 

 Kite ( Rostyrhamus sociabilis plum - 

 beus ) , which feeds exclusively upon 

 the apple snail ( Pomacea paludosa ), 

 concentrations of 1500 ug/kg were 

 reported. The apple snail feeds on 

 periphyton and detritus; the mos- 

 quito fish on insects and other 

 small detritovores. Unfortunately, 

 this work is more than 10 years old 

 and DDT is no longer in use. No 

 recent research results are readily 

 available with which to compare this 

 data, nor are data available on 

 pesticides currently being used in 

 the area. 



6.22 INVERTEBRATES 



Outside of a few key species, 

 ecological data on terrestrial and 

 freshwater wetland invertebrates in 

 the lower Everglades is scarce. 

 Several aquatic crustaceans have 

 received some attention, notably the 



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