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Soft-sediment macrobenthos around offshore wind turbines in the Belgian part of the North Sea reveals a clear shift in species composition

Delphine Coates UGent, Jan Vanaverbeke UGent, Marijn Rabaut UGent and Magda Vincx UGent (2011) Offshore wind farms in the Belgian part of the North Sea : selected findings from the baseline and targeted monitoring. p.47-63
abstract
Two offshore wind farms became operational in the Belgian part of the North Sea during 2009 and 2010 on respectively the Thorntonbank (C-Power) and the Bligh Bank (Belwind). During the past five years, a monitoring programme has been carried out to determine the baseline situation on the soft-sediment macrobenthos in these areas, together with any primary impacts that could have arisen during and after construction. During the first and second years after implementation of the turbines no large-scale impacts were detected on the macrobenthos (Reubens et al, 2009; Coates et al, 2010). A targeted sampling strategy was carried out during 2010 to detect any smaller scale impacts around the fifth gravity based foundation on the Thorntonbank. Macrobenthic communities can be highly dependent of sedimentological characteristics such as median grain size and organic matter content (Pearson & Rosenberg, 1978; Wilhelmsson & Malm, 2008). The increased epifaunal communities colonizing the hard substrates (turbines) produce organic enriched sediments, possibly modifying the soft-sediment macrobenthic communities (Kerckhof et al, 2010). The construction of offshore wind turbines could also produce shifts in the macrobenthic communities due to changing hydrography (Hiscock et al, 2002; Wilhelmsson & Malm, 2008; Zucco et al, 2006). Sediment samples were taken along four gradients alongside turbine D5, two parallel (Southwest and Northeast) and two perpendicular (Southeast and Northwest) to the main tidal currents. Samples at one and seven metres from the scour protection system (boulders) were taken by divers, while samples further away from the boulders (15, 25, 50, 100 and 200m) were collected using a Van Veen grab. Unfortunately, due to logistic problems (bad weather, availability of sampling vessels...) important samples were missing to reveal an accurate comparison of the biotic and abiotic data. Nevertheless, the following important trends were observed: firstly, a lower median grain size and higher macrobenthic densities were detected in closer vicinity to the turbine. Secondly, a difference in gradients was observed with high chlorophyll a concentrations and a lower median grain size together with high densities for Lanice conchilega and Spiophanes bombyx along the Southwest and Northeast gradients. The Southeast and Northwest gradients were mainly dominated by the tube building amphipod Monocorophium ascherusicum. These species are known for stabilising soft substrates and therefore provide a clear indication of a shifting macrobenthic community. At this moment, the macrobenthic community around the turbines on the Thorntonbank is very dynamic and could change rapidly as the system has probably not reached its balance. This study illustrates the importance of a small-scale monitoring strategy together with an in depth research on the morphology of the seabed, to determine the effects of wind turbines on the soft-sediment macrobenthos.
Please use this url to cite or link to this publication:
author
organization
year
type
bookChapter
publication status
published
subject
keyword
monitoring, macrobenthos, Offshore wind farms, soft substrates
book title
Offshore wind farms in the Belgian part of the North Sea : selected findings from the baseline and targeted monitoring
editor
Steven Degraer UGent, Robin Brabant and Bob Rumes UGent
pages
47 - 63
publisher
Royal Belgian Institute of Natural Sciences. Management Unit of the North Sea Mathematical Models
place of publication
Brussels, Belgium
language
English
UGent publication?
yes
classification
B2
copyright statement
I have transferred the copyright for this publication to the publisher
id
2918335
handle
http://hdl.handle.net/1854/LU-2918335
alternative location
http://www.mumm.ac.be/Downloads/monwin_report_2011_final.pdf
date created
2012-06-25 14:46:38
date last changed
2012-07-31 09:58:40
@incollection{2918335,
  abstract     = {Two offshore wind farms became operational in the Belgian part of the North Sea during 2009 and 2010 on respectively the Thorntonbank (C-Power) and the Bligh Bank (Belwind). During the past five years, a monitoring programme has been carried out to determine the baseline situation on the soft-sediment macrobenthos in these areas, together with any primary impacts that could have arisen during and after construction. During the first and second years after implementation of the turbines no large-scale impacts were detected on the macrobenthos (Reubens et al, 2009; Coates et al, 2010). A targeted sampling strategy was carried out during 2010 to detect any smaller scale impacts around the fifth gravity based foundation on the Thorntonbank. Macrobenthic communities can be highly dependent of sedimentological characteristics such as median grain size and organic matter content (Pearson \& Rosenberg, 1978; Wilhelmsson \& Malm, 2008). The increased epifaunal communities colonizing the hard substrates (turbines) produce organic enriched sediments, possibly modifying the soft-sediment macrobenthic communities (Kerckhof et al, 2010). The construction of offshore wind turbines could also produce shifts in the macrobenthic communities due to changing hydrography (Hiscock et al, 2002; Wilhelmsson \& Malm, 2008; Zucco et al, 2006). Sediment samples were taken along four gradients alongside turbine D5, two parallel (Southwest and Northeast) and two perpendicular (Southeast and Northwest) to the main tidal currents. Samples at one and seven metres from the scour protection system (boulders) were taken by divers, while samples further away from the boulders (15, 25, 50, 100 and 200m) were collected using a Van Veen grab. Unfortunately, due to logistic problems (bad weather, availability of sampling vessels...) important samples were missing to reveal an accurate comparison of the biotic and abiotic data. Nevertheless, the following important trends were observed: firstly, a lower median grain size and higher macrobenthic densities were detected in closer vicinity to the turbine. Secondly, a difference in gradients was observed with high chlorophyll a concentrations and a lower median grain size together with high densities for Lanice conchilega and Spiophanes bombyx along the Southwest and Northeast gradients. The Southeast and Northwest gradients were mainly dominated by the tube building amphipod Monocorophium ascherusicum. These species are known for stabilising soft substrates and therefore provide a clear indication of a shifting macrobenthic community. At this moment, the macrobenthic community around the turbines on the Thorntonbank is very dynamic and could change rapidly as the system has probably not reached its balance. This study illustrates the importance of a small-scale monitoring strategy together with an in depth research on the morphology of the seabed, to determine the effects of wind turbines on the soft-sediment macrobenthos.},
  author       = {Coates, Delphine and Vanaverbeke, Jan and Rabaut, Marijn and Vincx, Magda},
  booktitle    = {Offshore wind farms in the Belgian part of the North Sea : selected findings from the baseline and targeted monitoring},
  editor       = {Degraer, Steven and Brabant, Robin and Rumes, Bob},
  keyword      = {monitoring,macrobenthos,Offshore wind farms,soft substrates},
  language     = {eng},
  pages        = {47--63},
  publisher    = {Royal Belgian Institute of Natural Sciences. Management Unit of the North Sea Mathematical Models},
  title        = {Soft-sediment macrobenthos around offshore wind turbines in the Belgian part of the North Sea reveals a clear shift in species composition},
  url          = {http://www.mumm.ac.be/Downloads/monwin\_report\_2011\_final.pdf},
  year         = {2011},
}

Chicago
Coates, Delphine, Jan Vanaverbeke, Marijn Rabaut, and Magda Vincx. 2011. “Soft-sediment Macrobenthos Around Offshore Wind Turbines in the Belgian Part of the North Sea Reveals a Clear Shift in Species Composition.” In Offshore Wind Farms in the Belgian Part of the North Sea : Selected Findings from the Baseline and Targeted Monitoring, ed. Steven Degraer, Robin Brabant, and Bob Rumes, 47–63. Brussels, Belgium: Royal Belgian Institute of Natural Sciences. Management Unit of the North Sea Mathematical Models.
APA
Coates, D., Vanaverbeke, J., Rabaut, M., & Vincx, M. (2011). Soft-sediment macrobenthos around offshore wind turbines in the Belgian part of the North Sea reveals a clear shift in species composition. In S. Degraer, R. Brabant, & B. Rumes (Eds.), Offshore wind farms in the Belgian part of the North Sea : selected findings from the baseline and targeted monitoring (pp. 47–63). Brussels, Belgium: Royal Belgian Institute of Natural Sciences. Management Unit of the North Sea Mathematical Models.
Vancouver
1.
Coates D, Vanaverbeke J, Rabaut M, Vincx M. Soft-sediment macrobenthos around offshore wind turbines in the Belgian part of the North Sea reveals a clear shift in species composition. In: Degraer S, Brabant R, Rumes B, editors. Offshore wind farms in the Belgian part of the North Sea : selected findings from the baseline and targeted monitoring. Brussels, Belgium: Royal Belgian Institute of Natural Sciences. Management Unit of the North Sea Mathematical Models; 2011. p. 47–63.
MLA
Coates, Delphine, Jan Vanaverbeke, Marijn Rabaut, et al. “Soft-sediment Macrobenthos Around Offshore Wind Turbines in the Belgian Part of the North Sea Reveals a Clear Shift in Species Composition.” Offshore Wind Farms in the Belgian Part of the North Sea : Selected Findings from the Baseline and Targeted Monitoring. Ed. Steven Degraer, Robin Brabant, & Bob Rumes. Brussels, Belgium: Royal Belgian Institute of Natural Sciences. Management Unit of the North Sea Mathematical Models, 2011. 47–63. Print.