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

Type Article
Date 2020-06
Language English
Author(s) Pete Romain1, Guyondet Thomas2, Bec Beatrice1, Derolez ValerieORCID1, Cesmat Ludovic3, Lagarde FranckORCID1, Pouvreau StephaneORCID4, Fiandrino Annie1, Richard Marion1
Affiliation(s) 1 : Marine Biodiversity, Exploitation and Conservation (MARBEC). Univ Montpellier, CNRS, Ifremer, IRD, CC093, Place Eugène Bataillon, 34095, Montpellier Cedex 5, Montpellier & Sète, France
2 : Department of Fisheries and Oceans, Gulf Fisheries Center, P.O. Box 5030, Science Branch, Moncton, NB E1C 9B6 , Canada
3 : Syndicat Mixte du Bassin de Thau, 328, Quai des Moulins-34200 SETE, France
4 : Ifremer, Laboratoire des Sciences de l'Environnement Marin (LEMAR), 29840 Argenton-en-Landunvez, France
Source Ecological Modelling (0304-3800) (Elsevier BV), 2020-06 , Vol. 426 , P. 109049 (17p.)
DOI 10.1016/j.ecolmodel.2020.109049
WOS© Times Cited 13
Keyword(s) Shellfish farming, Carrying capacity, Stakeholder implication, Nitrogen and phosphorus inputs, Water frame directive, Ecological indicators, Phytoplankton depletion, Coupled biogeochemical-deb model

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.

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Pete Romain, Guyondet Thomas, Bec Beatrice, Derolez Valerie, Cesmat Ludovic, Lagarde Franck, Pouvreau Stephane, Fiandrino Annie, Richard Marion (2020). A box-model of carrying capacity of the Thau lagoon in the context of ecological status regulations and sustainable shellfish cultures. Ecological Modelling, 426, 109049 (17p.). Publisher's official version : https://doi.org/10.1016/j.ecolmodel.2020.109049 , Open Access version : https://archimer.ifremer.fr/doc/00622/73395/