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Esrom, Denmark, of 6,000 - 12,000/m2. Brinkhurst and Cook (1974) found that <br />densities of the three most common tubificids in the more polluted areas of Toronto <br />Harbour ranged from 51,000 - 197,000/m2. Similarly, oligochaete densities in non- <br />polluted lotic systems tend to be lower than those where pollution is reported. <br />Gryzbkowska and Witczak (1990) report oligochaete densities in the lower Grabia River. <br />Poland, ranging from 110 - 900/m2 and Palmer (1990) reports densities from 5,000 - <br />15,000/m2 in Goose Creek. Densities from polluted lotic systems can approach <br />200,000/m2 (Koehn and Frank 1980). <br />In our study, mean oligochate densities in the seasonally inundated wetland <br />(37,991/m2) and river backwater (95,687/m2) compare to the polluted systems described <br />above. Mean densities from the ephemeral side channel (7,762/m2) and river channel <br />(7,304/m2) are comparable to non-polluted systems. In general, oligochaete densities in <br />our study were higher in the habitats that were the most lentic like (the seasonally <br />inundated wetland and river backwater habitat types). <br />Ceratopo onidae <br />The study of ceratopogonids has mainly centered around adults because they have <br />been found to transmit viral diseases to livestock (Davies and Walker 1974). Larvae are <br />sometimes quantified in investigations of the benthos but are usually listed under "other <br />Diptera" and we have found density estimates to be scarce. They inhabit a variety of <br />habitats including tree holes, leafpacks, and pitcher plants but are usually most numerous <br />in shallow areas of streams, lakes, and ponds (Bowen 1983). The aquatic forms are <br />mostly predaceous (Merrit and Cummins 1984) but several species are known to consume <br />15