The distribution and abundance of benthic cyclopoid copepods in Esthwaite Water,Cumbria

The spatial and temporal distribution of the benthic cyclopoid copepods, Acanthocyclops viridis, Acanthocyclops bicuspidatus, Eucyclops agilis, Paracyclops fimbriatus and Macrocyclops albidus in a small eutrophic lake Esthwaite Water, Cumbria was investigated in 1982 and 1983. The behavioural and physiological mechanisms by which these organisms cope with the conditions of hypoxia and anoxia prevalent during seasonal stratification of the lake waters was considered. During stratification all of these species, with the exception of resting stage A. bicuspidatus, disappeared from the profundal zone and were limited to the shallower margins of the lake. None of these copepod species entered the plankton and established planktonic populations, none appeared capable of sustained anaerobic respiration, although all can withstand some degree of hypoxia, and only A. bicuspidatus appeared capable of entering resting stages. The data suggest that in eutrophic lakes species normally found in the profundus deal with anoxia by lateral migration to shallow waters where oxygen is available.