Response of zooplankton to the reduction and elimination of submerged vegetation by grass carp and herbicide in four Florida lakes

Abstract

Zooplankton populations were monitored monthly for a three year period in four Florida lakes. bach lake received an aquatic vegetation control program using grass carp (Ctenophar.~mgodon idella Val.) and herbicide, either alone or in combination. All aquatic vegetation was eliminated in the three lakes with grass carp; it was severely reduced and exhibited qualitative shifts in the lake treated with herbicide alone. Total number of recorded zooplankton species was reduced in each subsequent year as vegetation was eliminated, but mean density 1-I increased greatly. The overall trend in all lakes was toward increasing numbers of small filter-feeding herbivores, with a shift from copepod and copepod-cladoceran dominated to rotifer and small cladoceran dominated systems. It is suggested that these changes reflect primary plankton response to fluctuations in habitat, food base, and planktivore pressure resulting from gradual macrophyte alteration. Changes observed indicate apparent increases in eutrophy.

Shifts Across Trophic Levels as Early Warning Signals of Copper Sulfate Impacts in Plankton Communities

“…This inverse relationship of rotifera and copedoda under perturbation has been found in other studies. For instance Richard et al (1985) observed how under herbicide treatment there were shifts from copedoda and copedoda-cladoceran dominated communities to rotifera and small cladoceran dominated communities. A similar relationship was found by Gagneten & Paggi (2009), under heavy metals treatments (Pb and Cu) rotifera increased while copedoda and cladocera decreased.…”

A Study on Zooplankton of a Grass Carp Nursing Pond

“…Richard et al (1985) reported that the effect of grass carp indirectly on zooplankton would most likely be through the reduction of nutrient-absorbing competition from macrophytes and associated periphytic…”

Importance of Grass Carp (Ctenopharyngodon idella) for Controlling of Aquatic Vegetation

“…Finally, the zooplankton communities shifted from copepod and copepod-cladoceran-dominated communities to rotifer and small cladocerans. Changes in zooplankton abundance and community structure were due to an increase in phytoplankton and shifts in planktivore predation on zooplankton by fish after macrophyte removal [30].…”

“…The rate of aquatic plants elimination determines the magnitude of impact [30,34]. These changes in water quality are often followed by algal blooms [35] which in most lakes signal a shift to an alternative stable state [36].…”