Guerin, Andrew James
Marine Communities of North Sea Offshore Platforms, and the Use of Stable Isotopes to Explore Artificial Reef Food Webs.
University of Southampton, School of Ocean and Earth Science,
Stable isotope methods offer a powerful means of investigating trophic
interactions, allowing assessment of the relative importance of multiple nutrient
sources to biological assemblages, as well as estimation of the trophic positions of
consumers. Differences in the isotope ratios of consumers between habitats can
thus indicate differences in the structures of food webs, or the contributions of
different food sources to those food webs.
Isotope methods were used to compare the food web of an artificial reef located
off the south coast of England with that of a nearby natural reef system, revealing a
similarly complex food web, with similar trophic structure, and similar inputs from
the available food sources. Isotope methods should be incorporated into more
artificial reef studies, where they have been seldom applied.
Offshore oil and gas platforms in the North Sea are artificial reefs, hosting
substantial assemblages of sessile invertebrates and other associated fauna, and
attracting large numbers of fish and motile invertebrates. Structural survey footage
provided by the oil and gas industry allowed the investigation of the marine life
associated with several of these structures, of varied ages and in various locations
in the North Sea.
At least thirty?six taxa of motile invertebrates and fish were observed in association
with the structures, most of which were present on all platforms surveyed. While
most reef?associated fish were observed around the base of the larger platforms,
many thousands of fish were also observed in the water column around these
structures at other depths. A small number of sessile taxa dominated the fouling
assemblages, in places achieving total coverage of the available surfaces. Fouling
composition changed with depth, but this pattern was not identical on all
platforms. Platform age and location both affected the fouling assemblages
present, but these two factors did not fully explain all the variation.
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