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Echinoderm biodiversity, distribution and abundance on continental shelf in the Adriatic Sea as a base for monitoring and forecasting of possible anthropogenic disturbance in the benthic ecosystem

Up to the present date, 101 species of echinoderms have been recorded in the Adriatic Sea: 2 species of crinoids, 36 species of holothurians, 23 species of sea stars, 22 species of brittle stars and 18 species of sea urchins. Complex investigations of echinoderm fauna in the Adriatic Sea have been performed mainly in the area along eastern Adriatic coast and islands. The data on distribution of echinoderms in the open waters of the Adriatic Sea are very scarce. This study presents the first extensive investigation of echinoderm distribution in the area of soft bottoms in the open part of the northern and middle Adriatic Sea. The investigated area is ground of intensive trawling and disturbance. Investigation was performed during 11 cruises of “ Pipeta” expedition from 1985 to 1994 on sediment bottoms of the northern and middle Adriatic Sea. A total of 518 bottom trawl hauls were performed at 56 permanent stations along ten transects over different sediment types, “ relict” sand, clayey “ relict” sand, sand-silt-clay, clayey silt and silty clay, silty sand and sandy silt, at depths of 10 to 430 m. Samples were continuously collected by a commercial trawler, using the standard Italian bottom trawl during day and night. In the researched area 34 species from the phylum Echinodermata were found: 9 species from class Holothuroidea ; 12 species from class Asteroidea ; 4 species from class Ophiuroidea and 9 species from class Echinoidea. The most diverse echinoderm fauna was found in the open part of the middle Adriatic Sea on the clayey “ relict” sand at depths from 90 to 130 m and the least diverse on clayey silt and silty clay at depths from 120 to 230 m in the western part of the open middle Adriatic. The greatest abundance and biomass of the echinoderms was recorded at depths from 25 to 100 m. Distribution and abundance of each species on the researched stations and the distribution in relation to the bottom type and depth were calculated. Changes in abundance of the species at each station were analysed for the whole period of investigation. The results of the study are good base for comparison of communities’ state in the case of possible changes and could be used in forecasting the changes in marine communities due to the anthropogenic influence.

distribution; echinoderms; monitoring; benthic ecosystem; eastern Adriatic

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