Seasonal Variation and Habitat Distribution of Benthic Crustacea in Lake Mývatn in 1973

Abstract

Benthic crustaceans in 2 basins of Lake Myvatn [Iceland] showed similar species composition, but abundance and frequency differed. Herbivorous cyclopoids, Paracyclops fimbriatus (Fischer) and Eucyclops serrulatus (Fischer) peaked in June and July-Aug., respectively. Cladocerans peaked in July-Aug. Carnivorous Cyclops cf. abyssorum Sars had peaks in May, June and Sept. Megacyclops viridis (Jurine) peaked in July-Aug. By repeated siphoning from mud, species were divided into epi- and infauna. Eurycercus lamellatus Mull. and Acroperus harpae Baird belonged to 1st category and Macrothrix hirsuticornis Norman and Brady to the 2nd. Comparatively large epifauna species (E. lamellatus and A. harpae) were much more common in the south than in the north basin, possibly because of more fish predation in the north basin. The small Alona rectangula Sars was epifaunal in the north basin in contrast to its infaunal habit in the south basin. The infaunal M. hirsuticornis was dominant in the north but scarce in the south basin, possibly due to competition with chironomids. An abrupt decline in the cladoceran abundance did not coincide with an increase in invertebrate predators, but could possibly be related to an increase in fry of the numerous stickle-back population. C. cf. abyssorum behaved more as a benthic than a planktic species in the north basin, but in the south basin the difference was less clear.