REVISITED: the soft-bottom benthic communities of the
Belgian Part of the North Sea
Naomi T. Breine1, Annelies De Backer1, Tom Moens2, Gert Van Hoey1 and Kris Hostens1
1
Institute for Agricultural and Fisheries Research (ILVO), Aquatic Environment and Quality, Bio-environmental Research, Ankerstraat 1, 8400 Oostende, Belgium
2 Marine Biology section, Faculty of Science, Biology Department, University of Ghent, Krijgslaan 281 (S8), 9000 Gent, Belgium
WHY IS A REVISION NEEDED?
- A proper characterization of the communities is required to comply with the Marine Strategy Framework Directive (MSFD). This to describe the
initial status of the benthic ecosystem, and to assess environmental status in the future.
- Although four benthic communities have previously been described (Van Hoey et al., 2004, Degraer et al., 2008), 10 more years of data is now available, and
especially the spatial coverage (mainly offshore) has broadened.
ALSO
- To investigate the functional characteristics of each habitat (another requirement for MSFD), data on functional traits of the benthic species
have been collected.
Magelona – Ensis directus
Previously regarded as a transitional community, it is now a new
distinct community, with moderate diversity (12 species / 0.1 m²) and
high densities (2511 ind. / m²). Also characterized by high abundance
of Ensis directus.
Characteristic species,
contributing to 50% of within
community similarity
Coastal
Offshore
Nephtys cirrosa
Community with second lowest species
richness (9 species / 0.1 m²) and lowest
density (380 ind. / m²).
Macoma balthica
Remains the community with lowest
species richness (7 species / 0.1 m²) and
low density (580 ind. / m²).
Hesionura elongata
Abra alba
Former Ophelia borealis community. Now with
higher species diversity (14 species / 0.1 m²) and
higher densities than previously registered
(780 ind ./ m²).
Remains the community with highest
species richness (26 species / 0.1 m²) and
highest density (5763 ind. / m²).
MDS 2D stress: 0.22
Structural characteristics
Functional trait: feeding mode
Subsurface Deposit
Parasite
Offshore
40
35
Mean nr of species S
7000
30
Mean density N
6000
25
5000
20
STDV
4000
15
3000
10
2000
10
5
1000
0
0
0
30
20
Macoma balthica
Abra alba
Magelona-Ensis
directus
Nephtys cirrosa Hesionura elongata
Macoma
balthica
Abra alba
Magelona-Ensis Nephtys cirrosa
directus
Hesionura
elongata
N (ind. / m²)
Coastal
50
%
Surface Deposit
Predator
S (ind. / 0.1 m²)
60
Suspension
Scavenger/Opportunist
 Probably due to higher sampling effort in the
offshore area and higher identification power
for typical interstitial species occurring in the
coarse, permeable sands.
This ongoing study reveals that the benthic ecosystem we thought to know quite well, still has some unexpected secrets. A new benthic community
Magelona-Ensis directus was found, and the former Ophelia borealis community is now considered to be a more species rich community named Hesionura
elongata. Preliminary results on functional traits indicate variation within traits between communities, but the most obvious differences are seen between
the coastal and the offshore communities. We intend to add sedimentological data and elaborate the functional trait analysis to further characterize the
communities both physical and functional.
Many thanks to all students and scientist that sorted and identified macrobenthos in the lab at Ugent or ILVO over the last 30 years
References & attribution
Degraer, S., Verfaillie, E., Willems, W., Adriaens, E., Vincx, M., & Van Lancker, V. (2008). Habitat suitability modelling as a mapping tool for macrobenthic communities: an example from the Belgian part of the North Sea. Continental Shelf Research, 28(3):369-379.
Van Hoey, G., Degraer, S., & Vincx, M. (2004). Macrobenthic community structure of soft-bottom sediments at the Belgian Continental Shelf. Estuarine, Coastal and Shelf Science, 59(4):599-613.
Spio image : © BIO Photography Group, Biodiversity Institute of Ontario
All other biota images © Hans Hillewaert
Contact: naomi.breine@ilvo.vlaanderen.be