The hyperbenthos of the Southern North Sea: spatial and temporal analysis of communities and fish postlarvae
Trombetti, A. (2005). The hyperbenthos of the Southern North Sea: spatial and temporal analysis of communities and fish postlarvae. MSc Thesis. Universiteit Gent; MARELAC: Gent. 46 pp.
The Hyperbenthos is a taxonomic heterogeneous group of small animals living in the first meter above the seafloor. Research in the last decade suggested their importance in the marine ecosystems as an important player in the local food web. This study is a re-examination of three researches made by Mees et al. (1993), Beyst et al. (2001) and Dewicke et al. (2002), analysing the community structure and the temporal pattern of the Hyperbenthic assemblage in the Belgian continental shelf, surf beach zones and the Westerschelde estuary.The expansion the hyperbenthic assemblage was always linked to the major occurrence of the merohyperbenthic animals. Except for the Belgian continental sand banks, an increasing number ofspecies was observed in spring and summer. The low similarity values detected in the Coastal Banks, Eastern surf zone and Westerschelde could be a consequence of an over scaling of the sampling areas, suggesting a reduction of the analysis in the sub-areas. The density of all the Hyperbenthos increased from spring to early autumn, with maximum values reaching around 10000 individuals per m2. The Westerschelde Polyhaline zone shows conspicuous low density than the other areas (always less than 500 individual per 100 m2) followed by the Eastern beaches that show a weak peaks in July with 2000 individual per 100 m2. The density of the fish community followed the same temporal pattern as the one observed in the entire hyperbenthic assemblage. The high density of fish eggs were reported in the Zeeland Banks (about 7000 fish eggs per 100 m in May) while in the Coastal and Flemish Banks were reported the highest density of Pleuronectes flesus (276 individual per 100 m2) and Solea solea (200 individual per 100 m2). These observations emphasizes the importance of these areas in terms of food availability, shelter and growth. The highest density of Clupeidae sp. found in the western surf beach may indicate the utilization of this zone as nursery. These results reveal the importance of these aforementioned areas and further researches are therefore suggested to expand our knowledge and consequently improve management practices. The lower presence of fish reported along theWesterschelde may be related to the restriction of the sampling to the middle of estuary channel, which is characterized by a lower presence of fish in comparison to the adjacent salt marshes.
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