Can low sea urchin densities control macro-epiphytic biomass in a north-east Atlantic maerl bed ecosystem (Bay of Brest, Brittany, France)?

The distribution, abundance and feeding behaviour of sea urchins (Paracentrotus lividus, Psammechinus miliaris, Sphaerechinus granularis) and the macro-algal biomass were assessed in two maerl beds within a north-east Atlantic coastal ecosystem (Bay of Brest, Brittany, France). To study the possible...

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Bibliographic Details
Published in:Journal of the Marine Biological Association of the United Kingdom 2002-10, Vol.82 (5), p.867-876
Main Authors: Guillou, Monique, Grall, Jacques, Connan, Solène
Format: Article
Language:English
Subjects:
Algae
Animal and plant ecology
Animal, plant and microbial ecology
Anthropogenic factors
Applied ecology
Aquatic plants
Biological and medical sciences
Biomass
Coastal ecosystems
Conservation, protection and management of environment and wildlife
Ecosystems
Environmental changes
Environmental degradation: ecosystems survey and restoration
Feeding behavior
Fresh water ecosystems
Fundamental and applied biological sciences. Psychology
Hypotheses
Marine
Outlets
Paracentrotus lividus
Plankton
Psammechinus miliaris
Research Article
Salinity
Sewage
Sphaerechinus granularis
Synecology
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Summary:The distribution, abundance and feeding behaviour of sea urchins (Paracentrotus lividus, Psammechinus miliaris, Sphaerechinus granularis) and the macro-algal biomass were assessed in two maerl beds within a north-east Atlantic coastal ecosystem (Bay of Brest, Brittany, France). To study the possible control of herbivorous sea urchins on the macrophytic algae, one maerl bed under the influence of urban sewage (northern site) was compared to one less influenced by urban and industrial outlets (southern site). Macrophytic biomass in the northern site was estimated as 40-fold higher than in the southern site where sea urchins were, on average, 38-times more numerous. Preliminary results support the hypothesis that grazing of sea urchin, even in low densities, can be a factor regulating the macrophytic biomass on maerl beds except in too nutrient enriched environments. So in the northern basin of the Bay, data pointed out the role of anthropogenic impacts on macrophytic biomass increase which was concomitant with the progressive disappearance of sensitive herbivorous species like sea urchins, both processes result in change in the ecosystem.
ISSN:0025-3154
1469-7769
DOI:10.1017/S0025315402006276