Inshore and offshore diversity of epibenthos dredged in the North Sea |
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| Institution: | 1. University of South Carolina, Department of Civil and Environ. Engineering, 300 Main Street, B122A, Columbia, SC 29208, USA;2. University of South Carolina, Department of Civil and Environ. Engineering, 300 Main Street, C206, Columbia, SC 29208, USA;3. University of South Carolina, Department of Civil and Environ. Engineering, 300 Main Street, C210, Columbia, SC 29208, USA |
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| Abstract: | Large epibenthos (>1 cm.) was dredged in the German Wadden Sea and in adjacent offshore areas at 10 to 30 m depth in Helgoland Bight. There were apparent differences in species composition and relative abundances between the 2 regions. The hypothesis of increasing species richness in offshore direction and of increased individual numbers inshore was tested. Neither proposition was found to be generally true.Regional species number was higher offshore (85) than inshore (73). However, a direct comparison of 11 + 11 localities and of 66 + 66 dredge hauls revealed no significant differences. Ratios of species richness for localities versus regions and for hauls versus localities differed significantly, indicating a higher regional heterogeneity offshore and a higher habitat heterogeneity inshore. Thus, causes for an overall similar diversity were found on different spatial dimensions.Few species were encountered on bottoms subject to the riverine waters of Elbe and Weser. Many decapod crustaceans attained stronger populations inshore, while ophiuroids completely dominated the epibenthos offshore and caused higher individual numbers there. Historical sources suggest that the epibenthos was richer in the past than it is now. |
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