MEPS 211:225-234 (2001)  -  doi:10.3354/meps211225

ABSTRACT: Gut-evacuation rate (R), and daily ration (DR) were studied in the bathyal mysid Boreomysis arctica, a dominant species from the suprabenthic assemblage of the Catalan Sea, during a ca 72 h day-night sampling cycle (Cruise BT1 of March 1994) at depths from 638 to 1256 m. Although the density of B. arctica was higher during daytime in the water column between 0.1 and1.5 m above the sea floor, no significant changes in day-night density were recorded. Feeding peaks were detected during 2 consecutive days in the morning (between 09:59 and 11:58 h), while during the evening and night (between 16:09 and 01:28 h), feeding intensity decreased. The R obtained from field data (R_max) was 0.114 h^-1, whereas the R obtained from experimentally starved specimens collected during Cruise BBC1 of March 1998 varied between 0.141 h^-1 (3 specimens) and 0.345 h^-1 (1 specimen). The DR calculated with Elliott and Persson model ranged from 13.51 to 15.05% dry wt for R of 0.114 h^-1 and R 0.141 h^-1, respectively. The DR obtained for B. arctica was higher than the range of DR reported for megafaunal deep-sea decapod crustaceans in the same area (between 0.260 and 4.820% dry wt), but fell within the DR range reported for pelagic zooplankton (euphausiids, hyperiids, calanoids). Adopting 0.6 g C m^-2 as the mean annual organic carbon consumption of the sediment community from the neigbouring Lacaze-Duthier canyon (north Catalan Sea), B. arctica would consume ca 3.4% of organic carbon annually. Therefore, the trophic impact of this bathyal species is low compared to its numerical dominance in bathyal assemblages, and is often lower than that reported for mesopelagic species.

KEY WORDS: Daily ration · Food consumption · Suprabenthos · Gut-evacuation rates · Deep-sea communities