Benthic activity in sediments of the northwestern Adriatic Sea: sediment oxygen consumption, macro- and meiofauna dynamics

Benthic activity was examined at three stations (18 m water depth) in the n orthwestern Adriatic Sea. Carbon mineralisation rates, as based on sediment oxygen consumption rates, ranged from 54 to 89 g C m(-2) y(-1). The relati vely high carbon mineralisation rates, large macrofaunal biomass (9 to 16 g C m(-2)) and macrofaunal production (11 to 19 g C m(-2) y(-1)) provide evi dence of high organic-matter input and intense benthic-pelagic coupling. Th is is further supported by the high dominance of the suspension-feeding biv alve Corbula gibba, which accounts for 52 to 63% of the total annual macrof aunal biomass production. Although the infaunal distribution of total macro fauna showed a sharp decline in densities and biomass with depth into the s ediment, different patterns within the dominant taxa were observed. Whilst the bivalve Corbula gibba and the amphipod Ampelisca sp. were restricted to the surface layer, other species such as the dominant bivalve Mysella sp. and the gastropod Hyala sp. were not confined to a specific depth level and the majority of the populations occurred deeper than 5 cm into the sedimen t. Bioturbation, based on the occurrence of macrofauna, extended to at leas t 20 cm. Nematodes and foraminifera together formed 80 to 90% of the meiofa unal community in the upper 5 cm of the sediment. Annual mean densities ran ged from 3.40 to 6.07 x 10(6) ind. m(-2). Maximum abundance of meiofauna wa s not encountered at the station where maximum macrofaunal activity was rec orded, and this could reflect the negative effect of biological interaction on meiofaunal densities in areas that have a high food supply. (C) 1998 El sevier Science B.V. All rights reserved.