Abstract

Allogromiids sensu lato, including the orders Allogromiida and Astrorhizida, are a commonly ignored group of marine benthos. Allogromiid standing crop was examined in 121 sediment samples from the Barents and Kara seas. In 44 of these samples, foraminiferal biomass was determined by calculation of cytoplasmic volume. Foraminiferal standing crop is dominated by small allogromiids in two types of stressed marginal environments—river-influenced shallows and glacially fed fjords. Allogromiid frequency also increases in oligotrophic depressions of the open shelf. Large astrorhizids such as Rhabdammina abyssorum, Pelosina variabilis and Hyperammina subnodosa, being common on fine-grained sediments which dominate the shelf, constitute biomasses of ca 3 mg/10cm3, exceeding by an order of magnitude the biomass of all other foraminifera combined. Foraminiferal biomass values are comparable to those of macrofauna in shelf depressions distant from land, thus suggesting that, at least in food-deficient areas, the allogromiid foraminifera are a key group in benthic energy flux.

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