Gheskiere, T.

Vanaverbeke, J.

Vincx, M.

Open Marine Archive

Meiobenthos and nematode community diversity patterns on isolated 
sandbank systems from the Belgian Continental Shelf 
Vanaverbeke J., T. Gheskiere, and M. Vincx 
Ghent University, Biology Department, Marine Biology Section 
K.L. Ledeganckstraat 35, B-9000 Gent, Belgium 
1 E-mail : ian.vanaverbeke@rug.ac.be 
The Belgian Continental Shelf is characterised by the presence of four isolated subtidal sandbank systems 
(the Coastal Banks, the Flemish Banks, the Hinder Banks and the Zeeland Banks), which increase greatly 
the habitat heterogeneity of the area. These sandbanks form a geologically unique area and they are 
important for both marine and seabird life since they act as internationally important resting and foraging 
areas for various seabird species, feeding on small pelagic fish and macrobenthos. The rich marine and 
bird life makes them suitable areas for designation as marine protected areas as already recognised in 
other areas (e.g. the Baltic Sea). Surprisingly, the benthos of the sandbanks systems is poorly investigated. 
Therefore, all sandbanks belonging to the Flemish Banks, Hinder Banks and Zeeland Banks were visited 
during spring and fall of 1997 and 1998. Samples for meiobenthos were taken on all sandbanks and for 
each sandbank system, the nematodes from one sandbank (two sandbanks for the Hinder Bank system) 
were identified to species level. 
O n  the meiobenthic taxon level, no distinction between the meiobenthos from different sandbanks could 
be made. Stations originating from one sandbank system or a single sandbank are distributed among 
different groups when multivariate analyses were performed, reflecting sedimentological diversity on a 
sandbank rather than geographical position. Meiobenthic taxon diversity and density was h~ghest in 
sediments with a median grain size of 300-40Upm, while coarser sediments showed a similar diversity in 
lower densities. Both density and diversity was lower when median grains size dropped below 300pm. 
When nematode communities were considered, a very different picture emerged. The community 
composition from four sandbanks, representing three sandbank systems showed major differences. Every 
sandbank represented one group in multivariate analysis. Moreover, the Kwintebank community was 
separated in three groups. Here, a channel station was separated from the sandbank itself, the latter 
group being subdivided in the northern area, where sand extraction occurs regularly and the less 
influenced southern part. This clear geographical separation of the communities suggests the sandbanks 
to be isolated 'islands' from the point of view of the nematode communities. This can be explained by 
water movements around the sandbanks, preventing exchange of species between the sandbanks and 
sandbank systems. 
Generally it can be put forward that sandbanks are clearly different from the surrounding channels, both 
in terms of densities and diversity. The study of nematode communities clearly revealed the geographical 
! differences between the sandbanks, therefore it is suggested that nematodes should be identified to 
species level in order to clarify possible differences between sandbanks or sandbank systems. 


Meiobenthos and nematode community diversity patterns on isolated sandbank systems from the Belgian Continental Shelf

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