Benthic macroinvertebrates and physicochemical parameters were monitored simultaneously with hydrilla in a central Florida lake. Changes in the benthos were described in relation to plant growth. Twenty-seven of the 54 taxa of benthic macroinvertebrates collected were members of the Family Chironomidae. Chironomids and oligochaetes numerically dominated the benthos, comprising of 82% of the individual collected. The greatest numbers of species and individuals were found during the winter when hydrilla biomass was low. Hydrilla biomass ranged from 0.385 kg/m2 in April, 1977 to 2.275 kg/m2 in October, 1977. Low numbers of species and individuals were collected from bottom sediments during summer and fall. Dissolved oxygen 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 0.36, respectively.

Zooplankton abundance, hydrilla biomass, and physicochemical parameters were sampled for one year in a small central Florida lake. Annually, rotifers comprised most of the species collected and were the most abundant zooplankton group. Hydrilla biomass was lowest during winter and spring while orthophosphate and phtoplankton concentrations were highest. Zooplankton densities were highest when hydrilla biomass was low. Small-bodied limnetic herbivores comprised most of the zooplankton during the spring. Zooplanton abundances were lowest during summer and fall and may have been either directly or indirectly related to the hydrilla growth. Factors, such as lower phytoplankton and dissolved oxygen concentrations, possible increased predation by fish, and substances that may have been secreted by the hydrilla may have had a negative effect on the lake's zooplankton density. Littoral zooplankton species were frequently collected from the lake when hydrilla biomass was high. Species diversity (─æ) was lowest during winter and spring and ranged from 1.69 to 2.11; species diversity peaked during the summer reaching 3.04.