A box-model of carrying capacity of the Thau lagoon in the context of ecological status regulations and sustainable shellfish cultures

• Published in: Ecological Modelling
• Main Authors: Pete, Romain, Guyondet, Thomas, Bec, Beatrice, Derolez, Valerie, Cesmat, Ludovic, Lagarde, Franck, Pouvreau, Stéphane, Fiandrino, Annie, Richard, Marion
• Other Authors: MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Fisheries and Oceans Canada (DFO), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: ACL; reproduction; temperature; pacific oyster; aquaculture; environment; variability; oyster crassostrea-gigas; eutrophication; impact; Shellfish farming; Carrying capacity; Coupled biogeochemical-deb model; Ecological indicators; mediterranean lagoon; Nitrogen and phosphorus inputs; Phytoplankton depletion; Stakeholder implication; Water frame directive; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Pacific; Crassostrea gigas; Pacific oyster
• Online Access: https://hal.science/hal-03010383; https://hal.science/hal-03010383/document; https://hal.science/hal-03010383/file/S0304380020301216.pdf; https://doi.org/10.1016/j.ecolmodel.2020.109049

WOS:000529795300004 The decrease of microbial and nutrient inputs from the watershed has long dominated lagoon ecosystem management objectives. Phytoplankton biomass and abundance have drastically decreased for more than a decade and Zostera meadow have gradually recovered, expressing lagoon ecosystem restoration such as Thau lagoon. Do the progressive achievement of the good ecological status of the Thau lagoon possibly threatens the shellfish industry in terms of production and oyster quality, by reducing the carrying capacity? To provide answers about the right balance to be achieved between conservation and exploitation, a new numerical tool was developed to help in decision-making. We hereby propose to incorporate a Dynamic Energy Budget type shellfish production model to an existing lagoon ecosystem box-model. The influence of different scenarios of nutrient inputs (related to projections of population growth or improvement of treatment plants) and shellfish stocks were tested on oyster performances (production, oyster condition index), carrying capacity of the lagoon and ecological status indices used within the EU Water Framework Directive. Model outputs demonstrated that shellfish production was mainly controlled by nutrient inputs, which depend on hydro-meteorological variability, and specifically by phosphorus and N:P ratios of nutrient inputs. Scenarios tested, however, demonstrated smaller differences of oyster production in comparison to inter-annual variability. The overall ecological status of the lagoon remained in a "good" status with acceptable lagoon-scale phytoplankton depletion, regardless of scenarios, setting the carrying capacity of this ecosystem to be sustainable.