Large numbers of invertebrates were collected from the lower layer of seasonal ice in the nearshore Beaufort Sea, off the northern coast of Alaska in spring 1980. Over 90 % of the individuals found belonged to meiofaunal taxa. Although density within the ice was low compared to that typically found in sediments, it was comparable to the highest previous estimate from sea ice. Densities were lowest in samples taken in April and reached a maximum of around 50 000 individuals m-2 in June. Nematodes were numerically dominant, but copepods and turbellanans were also abundant. Population structures of the 2 most numerous copepod species were examined and found to differ greatly.Cyclopina gracilis appeared to reproduce continuously during the study; both adults and young copepodites were always present. The population of Harpacticus sp. initially consisted only of juveniles; the growth of a single cohort was observed. Harpacticus sp. mated in the ice, but gravid females did not appear during the sampling period. Although the ephemeral seasonal sea ice habitat would seem to be very different from typical habitats of benthic copepods, these 2 species did not appear to possess any special strategies for living there.
The ice meiofaunal assemblage in shallow Stefansson Sound off the northern coast of Alaska included Polychaeta, Nematoda. Rotifera and Crustacea. The crustaceans conlprised calanoid copepods, nauplii, 2 species of harpacticoids (Halectinosoma neglecturn and Pseudobradya sp.) shared with the benthos and a cyclopoid copepod (Cycloplna gracilis), probably a benthic epiphytic form.Much of the ice meiofaunal assemblage was dominated by larvae and juveniles. The ice taxa were sparse in numbers (100-1,000 tlmes less than the sediments) and depauperate in specles (e.g. 2 species of harpacticoids versus 28 in the sediments). The ice meiofauna appears to b e derived from both sediments and water column. We hypothesize that during sprlng the undersurface of nearshore sea ice acts as a substrate for benthic recruitment and for nourishment of a highly selected fauna. However, the meiofauna is too sparse to be significant in the food web or energy budget in the protected nearshore Beaufort Sea.
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