Variabilité temporelle de la diversité des peuplements de sédiments fins de la baie de Morlaix
Dauvin, J.-C.; Carbon, J. (2001). Variabilité temporelle de la diversité des peuplements de sédiments fins de la baie de Morlaix. Océanis (Paris) 1999(25): 343-375
In: Océanis (Paris). Institut Océanographique: Paris. ISSN 0182-0745, meer
Two infralittoral fine sediment communities from the Bay of Morlaix (western English Channel) were sampled regularly from 1977 to 1996. A database was created on ACCESS which manages all the data available: sampling date, list of the species collected, abundance of the species for each sample, environmental parameters. lt concerns 137 dates from the fine sand Abra alba - Hyalinoecia bilineata community at the Pierre-Noire site and 97 dates for the muddy fine sand Abra alba - Melinna palmata community at the Rivière-de-Morlaix site for a total of 2340 Smith Mcintyre samples (0.1 m²). A total of 432 species was identified at the Pierre-Noire site and a total of 326 species was identified at the Rivière-de-Morlaix site. Both sites were strongly polluted by hydrocarbons from the Amoco Cadiz in 1978 with a major impact at the Pierre Noire site (disappearance of the dominant arnphipod Ampelisca populations) but only limited impact at the Rivière-de-Morlaix site. Based on these two long series of benthic samples with the same sampling and laboratory methods along the 20 years of the survey, the changes in diversity of both communities were analysed using several techniques: diversity indices, changes of the number of species and abundance, Rank-Frequency Diagram. Several scales of temporal changes were analysed: variation during the same set of 10 grabs, seasonal variation, and long-term trend. The relationship between sampling effort and cost of the data acquisition necessary for optimal sample size and replication is also discussed.
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