Studies on the zooplankton community of Belews Lake, North Carolina, with a discussion of the role of cyclopoid copepods in transmission of the fish tapeworm, Bothriocephalus acheilognathi

Artificial perturbations provided an opportunity to examine a variety of aspects of zooplankton community biology in Belews Lake, North Carolina. Selenium poisoning caused the elimination of most fish species, including all piscivores. Piscivore removal permitted the proliferation of planktivorous fish, which, in turn, impacted on zooplankton community structure. Though zooplankton diversity was similar between 1974-75 and 1984-86, shifts in dominance from large to small species occurred within the crustacean component of the zooplankton. Large cladocerans were severely reduced in abundance, but no local extinctions were observed. No discernable effects of thermal effluent on zooplankton community structure were seen. Zooplankton diversity and species composition in the thermally-altered discharge arm were similar to those in the ambient area of the lake both in 1974-75 and 1984-86.;The cladocerans Bosmina longirostris and Pseudosida bidentata and the copepods Mesocyclops edax and Tropocyclops prasinus exhibited distinct patterns of vertical migration. All migrants except T. prasinus altered their daytime distributions into deeper waters after the hypolimnion was artifically lowered due to hypolimnetic aeration. Predator avoidance can not account for these alterations in migration, and these results provide the first empirical support for metabolic or demographic models of vertical migration.;All cyclopoid copepods in Belews Lake were experimentally found to serve as intermediate hosts for the fish tapeworm Bothriocephalus acheilognathi. These copepods include the planktonic Diacyclops thomasi, M. edas and T. prasinus, and the benthic Eucyclops agilis and Paracyclops fimbriatus poppei. Abundance of B. acheilognathi in the fall during 1984-86 was significantly less than in autumn as observed in previous studies, and this is attributed to shifts in cyclopoid copepod composition within the zooplankton. Whereas D. thomasi was previously present during both spring and fall periods of parasite recruitment by the fish hosts, in 1984-86 only the small T. prasinus was present in the fall. This change in community composition is most likely due to increased size-selective predation by expanding populations of planktivorous fish.