Ecology of Zooplankton of the Cape Thompson Area Alaska

Abstract

In a survey of the physicochemical characteristics, primary productivity and occurrence of zooplankton in fresh and brackish waters of Cape Thompson, Alaska, between June 28, 1960 and August 7, 1961, 14 species of Cladocera and 38 species of Copepoda (13 Calanoida, 11 Cyclopoida and 14 Harpacticoida) were distinguished in collections from 10 lakes, 8 lagoons and 111 pools. Seventy-three percent of all species were monocyclic; 13 per cent dicyclic; 9 per cent tricyclic; and 4 per cent tetracyclic. The maximum of primary production was correlated with maximal numbers of zooplankton, maximal number of eggs per ovigerous female in the Cladocera, and maximal occurrence of copepodids. Many Copedoda produced eggs in late fall and early winter when primary production was low. Autumnal production of eggs by these species may be possible because of storage of energy as lipids during the period of high environmental energy, and use of the stored energy at the end of the developmental period to form eggs. Analysis of community structure among zooplankton showed: 10 species with affinities and 7 interrelated recurrent groups occurred in the lakes; 3 species with affinities and 1 recurrent group occurred in the lagoons; 4 species with affinities and 3 interrelated recurrent groups occurred in the coastal pools; and no species with affinities occurred in the inland pools. One cladoceran, one cyclopoid and one or two calanoid copepods of different genera formed the major recurrent groups. The relationships between recurrent groups were the result of species within those related groups having similar distribution and overlapping developmental cycles. Closely allied species occupied different aquatic habitats, but when congeneric species co-occurred, there were differences in size and life cycles.