Reproductive strategies of benthic invertebrates in the Kara Sea (Russian Arctic): adaptation of reproduction modes to cold water

Abstract

Many benthic invertebrates in the boreo-Atlantic region reproduce via pelagic larvae. Past investigations in polar areas suggested a greater predominance of species lacking a pelagic phase. In this study, the reproduction strategies of the main 88 species of the Kara Sea were investi- gated. Field observations were supplemented by literature studies (reproduction period and strategy, biogeographical affiliation). Larvae of 44 meroplanktonic species were identified, but adult forms of only 23 of these species are known from the region. For the other 21 larval types, adults were not pre- sent in the Kara Sea but have previously been recorded in the adjacent Barents Sea. Larval transport processes are thus potentially important for the import of species into the region. High numbers of species of temperate origin were common, and had a strong influence on the overall reproduction patterns of the region. The southern Kara Sea was mainly dominated by 2 groups: highly mobile crus- taceans, which are obligate non-pelagic developers, and non-motile organisms with primarily pelagic reproduction modes. We propose that reproduction patterns are strongly influenced by the highly variable environmental conditions of the Kara Sea which, via ice-scouring and the high input of freshwater from the 2 adjacent rivers, regularly lead to a local depletion of the benthic species. The input of warm freshwater from the rivers enhances the survival of species with a boreal bio- geographical distribution, which additionally contributes to the high number of species with pelagic development that were found. Overall, the reproduction modes of benthic invertebrates in the Kara Sea are thus strongly governed by the local environmental conditions characteristic of the region.