Interactions between aggregations and environmental factors explain spatio-temporal patterns of the brittle-star Ophiothrix fragilis in the eastern Bay of Seine

• Published in: Estuarine, coastal and shelf science Vol. 131; pp. 171 - 181
• Main Authors: Dauvin, Jean-Claude, Méar, Yann, Murat, Anne, Poizot, Emmanuel, Lozach, Sophie, Beryouni, Khadija
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 10.10.2013; Elsevier
• Subjects: Agglomeration; Animal and plant ecology; Animal, plant and microbial ecology; Bay of Seine; Biological and medical sciences; Brackish water ecosystems; Brittleness; Coastal; Continental interfaces, environment; dense aggregations; English Channel; Environmental Sciences; Estuarine environments; Floods; Fundamental and applied biological sciences. Psychology; Global Changes; Heterogeneity; Ophiothrix fragilis; Sciences of the Universe; Sediments; Seines; spatial changes; Synecology; temporal changes; English Channel; Atlantic Ocean; North Atlantic; ANE, Europe, English Channel; ANE, France, Haute-Normandie, Le Havre, Le Havre Harbour; ANE, France, Normandie, Seine Bay; ANE, France, Haute-Normandie, Seine Estuary; Ophiothrix fragilis; English Channel; temporal changes; Bay of Seine; spatial changes; dense aggregations; Aggregation; Brackish water environment; Interaction; Environmental factor; Bay; Time variation; Ophiothrix fragilis dense aggregations Bay of Seine English Channel temporal changes spatial changes
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2013.07.005

There is a paucity of studies showing long-term changes in the population dynamics of dominant benthic epifaunal species, especially echinoderms, in relation to biological and environmental factors. In the English Channel, the brittle-star Ophiothrix fragilis is a common epifaunal species, mainly found in strong tidal currents characterised by benthic habitats with pebbles. However, in the Bay of Seine, O. fragilis lives on gravel and coarse sandy sediments; more locally, it occurs where there are unexpected amounts of fine particles for such high hydrodynamic areas. This species forms dense aggregations, supporting large populations up to 7450 ind m−2. This paper analyses the long-term spatio-temporal changes of O. fragilis aggregations over the last 25 years in the eastern part of the Bay of Seine through observations obtained from several scientific programmes from 1986 to 2010. This area is characterised as a tidal environment affected by the Seine estuary and is subject to potential sediment supply from the dumping site of the Le Havre harbour dredging operations. During all surveys, there was a similar pattern: persistent patches with high abundances of O. fragilis and sites without O. fragilis, showing that there was a high heterogeneity of the spatial population pattern. Interactions between environmental conditions and ophiurid aggregations (e.g., storm waves, Seine floods and patches) are suggested to explain these patterns. •This study shows the spatio-temporal patterns of the Ophiothrix fragilis in the Bay of Seine.•We examine the abundance changes during 25 years.•We observe the spatio-stability of abundance patches.•Storm waves and Seine floods appear important to explain these patterns.