Sampling epifauna, a necessity for a better assessment of benthic ecosystem functioning: An example of the epibenthic aggregated species Ophiothrix fragilis from the Bay of Seine

S. Lozach; Jean-Claude Dauvin; Y. Méar; A. Murat; Dominique Davoult; A. Migné

doi:10.1016/j.marpolbul.2011.09.012

Journal articles

Sampling epifauna, a necessity for a better assessment of benthic ecosystem functioning: An example of the epibenthic aggregated species Ophiothrix fragilis from the Bay of Seine

S. Lozach ^{1, 2} Jean-Claude Dauvin ¹ Y. Méar ³ A. Murat ³ Dominique Davoult ⁴ A. Migné ⁴

1 M2C - Morphodynamique Continentale et Côtière

2 LOG - Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187

3 INTECHMER - Institut national des sciences et techniques de la mer

4 AD2M - Adaptation et diversité en milieu marin

Abstract : Sampling the sea bottom surface remains difﬁcult because of the surface hydraulic shock due to water ﬂowing through the gear (i.e., the bow wave effect) and the loss of epifauna organisms due to the gear's closing mechanism. Slow-moving mobile epifauna, such as the ophiuroid Ophiothrix fragilis, form highdensity patches in the English Channel, not only on pebbles like in the Dover Strait or offshore Brittany but also on gravel in the Bay of Seine (>5000 ind m 2 ). Such populations form high biomasses and control the water transfer from the water column to the sediment. Estimating their real density and biomass is essential for the assessment of benthic ecosystem functioning using trophic web modelling. In this paper, we present and discuss the patch patterns and sampling efﬁciency of the different methods for collecting in the dense beds of O. fragilis in the Bay of Seine. The large Hamon grab (0.25 m 2 ) highly under-estimated the ophiuroid density, while the Smith McIntyre appeared adequate among the tested sampling grabs. Nowadays, diving sampling, underwater photography and videos with remote operated vehicle appear to be the recommended alternatives to estimate the real density of such dense slow-moving mobile epifauna.

Keywords : Ophiothrix fragilis Epifauna Benthic sampling English Channel Grabs Video

Document type :

Journal articles

Domain :

Sciences of the Universe [physics] / Continental interfaces, environment

Environmental Sciences / Global Changes

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Sampling epifauna, a necessity for a better assessment of benthic ecosystem functioning: An example of the epibenthic aggregated species Ophiothrix fragilis from the Bay of Seine

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Sampling epifauna, a necessity for a better assessment of benthic ecosystem functioning: An example of the epibenthic aggregated species Ophiothrix fragilis from the Bay of Seine

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