Zoobenthos in the Littoral and Profundal Zones of Four Faroese Lakes Botndjór í strandaøkinum og profundala økinum í f˝ra føroyskum vøtnum

Density and species composition of macroinvertebrates in the littoral and profundal zones of the four Faroese lakes Leynavatn, Eystara Mjaavatn, Saksunarvatn and Toftavatn were studied in early August 2000. Mean density of macroinvertebrates on rocky substrate in the littoral zone ranged between 11,272 and 37,239 ind m-2, and mean density in the profundal ranged between 30,199 and 175,387 ind m-2. For both habitats, the lowest densities were recorded in Leynavatn, the most oligotrophic, largest and deepest of the four lakes. Relative density contribution of invertebrate groups in the littoral zone was similar among the lakes, cladocerans being the most abundant group, followed by chironomid larvae, copepods and finally oligochaetes. In the profundal, density contribution of invertebrate groups differed considerably among the lakes, with ostracods outnumbering other taxa in Leynavatn and Eystara Mjaavatn, oligochaetes dominating in Saksunarvatn and chironomid larvae in Toftavatn. For both the littoral zone and the profundal, there was a considerable difference among the lakes in density proportions of cladoceran species. Total densities in both habitats of all the lakes were within the range recorded in Icelandic lakes, but there were some distinct