Network analysis of the planktonic food web during the spring bloom in a semi-enclosed lagoon (Arcachon, SW France)

• Published in: Acta Oecologica
• Main Authors: Tortajada, Sébastien, Niquil, Nathalie, Blanchet, Hugues, Grami, Boutheina, Montanie, Hélène, David, Valerie, Glé, Corine, Saint-Béa, Blanche, Galen A, Johnson, Marquis, Elise, del Amo, Yolanda, Dubois, Sophie, Vincent, Dorothée, Dupuy, Christine, Jude, Florence, Hartmann, Hans J., Sautour, Benoit
• Other Authors: Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Nord )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Northeast Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-00807552; https://doi.org/10.1016/j.actao.2012.02.002

International audience The structure and functioning of the food web in Arcachon Bay (Bay of Biscay, Northeast Atlantic Ocean) was analyzed during the spring bloom period to evaluate the sensitivity of this ecologically and economically important ecosystem perturbation. Differences in the timing of the peaks in phytoplankton and zooplankton populations occur due to a mismatch between primary production and grazing. Using an inverse approach based on in situ experimental data, an ecological network analysis was carried out to characterize emergent properties of the food web and to estimate carbon flows. The data set was composed of rate measurements for net primary production, import and export of dissolved organic carbon, and grazing of heterotrophic nanoflagellates and ciliates by metazoan micro- and mesozooplankton. Ecological network analysis indices were calculated on the estimated fluxes and compared to values from plankton models built with exactly the same method. The largest activities in the resulting model came from the nano- and microphytoplankton. The detritivory/herbivory ratio, the recycling rates and the relative redundancy of the system were very low compared to other planktonic systems, even in similar periods of bloom. These values indicate a transitional system with poor resilience that exports a large quantity of carbon either to the benthos where it is consumed by non-planktonic consumers such as oysters, or else to systems outside of the bay (outwelling).