Baseline studies on meiofauna in the Baltic Sea before bottom-trawl fisheries exclusion I: comparison of communities in the Fehmarn Belt (western Baltic Sea), with special reference to the Harpacticoida (Crustacea, Copepoda)

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The meiobenthic communities of a protected area and a reference area in the Fehmarn Belt (Baltic Sea, Germany) were compared, with both study areas currently permitting bottom-trawl fisheries. Meiobenthic data were recorded at the major taxon level. Additionally, the Copepoda Harpacticoida were further examined at the species level. This data collection will serve as a baseline for future assessments, after the planned exclusion of bottom-trawl fisheries in the protected area in 2024 to identify potential impacts on meiofaunal communities. In assessing the meiobenthic data in relation to trawling impact, a trawling index derived from multibeam data for the Fehmarn Belt was employed and developed in the early stage of the project. A comparison of major taxonomic levels did not reveal significant differences between the protected and reference areas in terms of taxa composition, abundance values or diversity. However, analysis of the Harpacticoida community at the species level showed that the compared areas differ significantly in species composition and abundance but not in diversity. These differences in the distribution of harpacticoid species indicate a small-scale heterogeneity of different (a)biotic factors. The initial correlation analyses between trawling intensity and both the main taxonomic levels and the Harpacticoida community did not reveal statistically significant results. This finding is attributable to the small number of samples all recovered in a trawling-affected area. Nevertheless, a higher variance in total abundance between replicates was observed with increasing trawling intensity.