|Study of the meiobenthos in the Southern Bight of the North Sea and its use in ecological monitoring|
Cheng, G. (1987). Study of the meiobenthos in the Southern Bight of the North Sea and its use in ecological monitoring. MSc Thesis. Rijksuniversiteit Gent, Zoologisch Instituut: Gent. 172 pp.
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VLIZ: Non-open access 123405
|Document type: Dissertation|
Biodiversity; Community composition; Environmental monitoring; Meiobenthos; Copepoda [WoRMS]; Nematoda [WoRMS]; ANE, Netherlands, Westerschelde [Marine Regions]; ANE, North Sea, Southern Bight [Marine Regions]; Marine
The meiobenthic communities of six stations in the Southern Bight of the North Sea are described and their possible use for ecological monitoring in pollution case studies is examined. The six stations were sampled in Spring 1985. Two stations are located along the Belgian coast, one of those (st 701) is located in an area influenced by the polluted Westerschelde waters; it is characterized by a muddy sediment. The other coastal station (st 110) is situated along the west coast and the sediment consists of clean, medium sand. Two off-shore stations are situated on the Kwintebank (st 751 and 7531, one off-shore station (st 800) is situated in the deeper open sea region while the fourth off-shore station (st 435) is located in a dumping area of industrial waste products of unknown origin (unknown to us). The four off-shore stations consist of clean fine to medium sand. The density of the meiobenthos is not significantly different between the six stations and varies between 400 and 2400 ind./10 cm². Thirteen meiobenthic taxa are found; from these, only Nematoda, Harpacticoida, Turbellaria, Polychaeta and Hydrozoa are recorded in all the stations. The structural parameters (density, diversity and biomass) of the nematode and copepod communities were examined in more detail. The comparison of the stations based on the species composition of the nematode and copepod communities were carried out by means of qualitative and quantitative similarity indices, Twinspan-classification and DCA-ordination. 189 nematode species and 71 copepod species were recorded for the six stations. For the nematodes as well as for the copepods, four station-groups can be separated each of which is strongly correlated with the sediment composition. Only minor differences are found according to the different classification techniques. Group I consists of st 701 and is characterized by a very low diversity of the nematode as well as of the copepod community. Group I1 consists of st 110 and is characterized by nematode and copepod communities with a low diversity, but nevertheless with a higher number of species than in st 701. Group III consists of st 753 and 435 which have very diverse nematode and copepod communities. Group IV consists of st 751 and 800; both stations have a very high diversity for both taxa, except the nematodes for st 751. The four off-shore stations are not very different, from each other in sediment composition; only st 800 has a considerable amount of gravel, in comparison with the other stations. The nematode community of the polluted station 701 is examined more in detail from five different sampling periods in 1985 - 1986. No real seasonal fluctuation could be detected; diversity is always very low in this station. The five dominant species are present in all samples, but with changing, not constant numbers. Biomass of the nematode community is correlated with its density. Six methods have been applied to detect pollution effects in the natural state of the meiobenthic communities of the six stations. (1). Taxon diversity of the meiofaunal community is a good indicator of environmental stress. The lowest number of taxa are found in st 701 and st 435 (7 and 6 respectively). (2). The ratio of nematode to copepod abundances shows also differences between stations 701 and 435 and the other four stations, but for this parameter, the distinction between st 701 and st 435 is more clear; st 701 has a ratio of 30 while st 435 has a ratio of about 10. Ratios varying between 1 and 2.5 are recorded for the other stations. (3) . Density and biomass of the nematode communities seem not to be affected by pollution; copepods seem to be more sensitive to environmental stress, because lowest densities for them are found in st 701 and st 435. (4) . The diversity of both nematode and copepod communities is significantly lower in st 701; for st 435, only the copepods are characterized by a very low diversity, while nematodes have diversities comparable with the other four stations. (5). k-dominance curves, which show the intrinsic pattern of community diversity, indicate different results for the two taxa. Station 753, 800 and 435 have comparable diversity patterns for the nematodes; station 751 follows the same pattern as the other three, except for the very high dominance of one species. Station 110 has an intermediate position while st 701 is characterised by the co-dominance of 5 species. A similar pattern is found for the copepods, except for the curve of st 751 which is almost identical with the curve of st 800. (6). The trophic diversity index of the nematode community shows a similar pattern as the k-dominance curves and distinguishes only very clearly st 701 from the other stations. It can be concluded that the presence and density of most meiobenthic taxa (except nematodes) are influenced by sediment type and pollution in station 701 (from the Westerschelde estuary) and 435 (from dumping activities).
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