On the ecology of a North Adriatic benthic community: Distribution,standing crop and composition of the macrobenthos

The boundaries as well as the macro-epibenthic biomass distribution and composition of a North Adriatic benthic community, dominated by the brittle star Ophiothrix quinquemaculata (D.Ch.), the sponges Reniera ssp., and the ascidians Microcosmus ssp. were determined. Transects totalling more than 80 km (i.e., a recorded area of approximately 150 000 m²) were taken by means of a combined TV- and photocamera sled. The observations, TV-recordings, and photos, together with 392 diver-collected quantitative samples were evaluated. The biomass values were used to establish isobenths. Within the community, the mean biomass, measured as wet weight, amounted to 370 (±73) g/m² with maxima of more than 1000 g/m². 64% of the biomass was due to the designating group Ophiothrix-Reniera-Micrcosmus, 87.5% were represented by filter- and suspension-feeding species alone. The mean biomass in the peripheral areas was evaluated at 166 (±62) g/m². Biomass distribution and composition is examined, and the ecological function and meaning of the observed patterns is discussed.This investigation was carried out within the frame of a joint programme between the Lehrkanzel für Meeresbiologie, University of Vienna, and the Marine Biological Station, Portoroz, University of Ljubljana.