Dewicke, A.

Mees, J.

Dewicke, Ann

Mees, Jan

Ghent University Academic Bibliography

The hyperbenthic fauna of the Belgian continental shelf: spatial variability in community structure

Open Marine Archive

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THE HYPERBENTHIC FAUNA OF THE 
BELGIAN CONTINENTAL SHELF: 
SPATIAL VARIABILITY 
IN COMMUNITY STRUCTURE
Vlaams Instituut voor dB Zee
Flanders Marine Institute
Ann DEWICKE and Jan MEES
7 2 8 0
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The hyperbenthos o f  the Belgian coastal waters, the W esterschelde estuary and part 
f  the Dutch delta was sampled within a 2-week period at 4 1 locations in the summ er o f  
993 (figure l). At each location sampling was done at tw o depth strata, covering all major 
andbanks in the area, and the gullies separating them. Sampling depth ranged from 6 to
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K eyw ords: hyperbenthos, com m unity structure, N o rth  Sea
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F ig u re  2: The hyperbenthic sledge (modified sledge described by Sorbe J .-C ., 1983)
The samples were taken with a hyperbenthic sledge (figure 2) equipped with four 
nets (1 mm and 0.5 mm mesh size), covering tw o lower strata ° f  ■the watercolumn. 0 •
m eter and 0.5 to  1 meter above the bottom. Trawling (5 minutes at 1.5 knots, approx. 2 
m eter per trawl) was always done during daylight and against the tide. The sledge wa 
equipped with an automatic opening-closing device, an odom eter and a current m eter n 
addition, sediment and w ater samples were taken at each station for grain fract.on analysis 
and pigment analysis.
In the laboratory all animals were identified, if  possible to  species level, counted and 
measured. Density was calculated and biomasses w ere derived from ash-free-dry-weight 
regressions. Density and biomass data were subjected to  multivariate statistical an^ * -  » 
classification (clustering based on the Bray-Curtis similarity 
Sorting), an ordination (Canonical Correspondance Analysis) and a hybnd technique ( 
way Indicator Species Analysis).
A total o f  135 species w ere recorded in the hyperbenthic fauna o f the Belgian 
continental shelf. The most abundant faunistic taxa include M ysidacea 
Brachyura (20 species), Amphipoda (33 species) and C andea (14 species). Chaetognat a, 
Pisces, Anomura, Polychaeta, Isopoda, Copepoda and Cum acea were caught to a lesser 
extent T he hyperbenthos o f  the Belgian coastal area can be divided into 6 geographical^ 
defined communities (figure 3), characterised by their species com pos.t.on diversity 
density and biomass. In the eastern part o f  the W esterschelde, a typical brackish water 
community was found ( W ) .  Two communities w ere found onshore: onshore east is 
located on the east coast (from Oostende to  Zeebrugge) including the manne part of
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Figure 3: Geographical location o f the hyperbenthic communities on the Belgian continental shell
8000
6000
4000
2000
> 32000 N /100m‘.
w s onshore w est onshore east mid bkp mid vd oflshore
□  M ysidacca B  A m phipoda □  Caridea ®  P isces B  Chaetognatha H  Brachyura ■  C opepoda
13 A nnelida W C um acea ■  A nom ura  @ M ollusca ^  Thalassim dea ■  others__________________
Figure 4: Average density and taxonomic composition o f the hyperbenthic communities
W esterschelde; on the west coast (from Oostende to De Panne) the
w est’ was found. ’Mid bkp' and 'mid vd' are the two transition communities between
onshore and more offshore area. The 'offshore' community occurs tow ards the open sea.
The community structure changes sharply along a gradient perpendicular to the 
coastline- highest densities and biomasses w ere recorded onshore (figure 4). The onshore 
communities (and the 'ws' community) w ere characterised by a low diversity and^consisi 
mainly o f  Mysidacea. Diversity increased offshore and the species com position o f  the hyp 
benthic fauna is changed: more faunistic groups became almost equally represented, 
especially the Brachyura being dominant.
A c k n o w le d g e m e n ts
This research was partly supported by the GOA 92/98-08 project from the University o f Gent (Flemish 
Advancement o f Scientific-Technological research in Industry (1WT).
R e fe re n c e s
Sorbe, J.-C. (1983). Description d'un traîneau destiné à l'échantillonage quantitatif étagé de la faune 
suprabenthigue néritique. Ann. Inst. Océanogr. 59'. 117-126.
University o f  Gent, M arine Biology Section, Institute o f  Zoology 
K.L. Ledeganckstraat 35, B-9000 Gent, Belgium  
E-mail: Ann.Dewicke@ rug.ac.be /  Jan.M ees@ rug.ac.be
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The hyperbenthic fauna of the Belgian continental shelf: spatial variability in community structure

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