Benthic Macroinvertebrates of a Hydrilla Infested Central Florida Lake

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Abstract
Benthic macroinvertebrates and physicochemical parameters were monitored simultaneously with hydrilla (H. verticillata Royle) biomass in a central Florida lake. Of the 54 taxa of benthic macroinvertebrates collected, 27 were Chironomidae. Chironomids and oligochaetes numerically dominated the benthos, comprising 82% of the individuals collected. The greatest numbers of taxa and individuals were found during the winter when hydrilla biomass was low. Hydrilla biomass ranged from 0.382 kg/m2-FW [fresh weight] in April, 1977 to 2.275 kg/m2-FW in Oct., 1977. Low numbers of macroinvertebrate taxa and individuals were collected from bottom sediments during summer and fall. Dissolved O2 concentrations at the bottom were approximately 2.0 ppm during summer and fall and possibly limited benthic organisms. The annual means for the Shannon and Simpson indices for the benthos were 1.92 and 0.35, respectively.