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Marine Ecology Progress Series

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MEPS 641:79-100 (2020)  -  DOI:

Impact of oysters as top predators on microbial food web dynamics: a modelling approach with parameter optimisation

R. Caillibotte1,*, Y. Leredde1, F. Vidussi2, C. Ulses3, P. Marsaleix3, C. Estournel3, B. Mostajir2

1Laboratoire Géosciences Montpellier (GM), UMR 5243, CNRS/Université de Montpellier/Université des Antilles, 34090 Montpellier, France
2Center of Marine Biodiversity, Exploitation and Conservation (MARBEC), UMR 9190, CNRS/Université de Montpellier/IRD/IFREMER, 34095 Montpellier, France
3Laboratoire d’Aérologie (LA), UMR 5560, Université de Toulouse/CNRS/Université Paul Sabatier, 31400 Toulouse, France
*Corresponding author:

ABSTRACT: Aquaculture is becoming a relevant and productive source of seafood, and production is expected to double in the near future. However, bivalve activities can significantly impact coastal ecosystem functioning. To study the direct and indirect impacts of oysters on the microbial food web, a 0D biogeochemical modelling approach was adopted. The model was adjusted by parameter optimisation, assimilating data from several mesocosm observations of concentrations of nitrate, phosphate, silicate, dissolved organic carbon, chlorophyll, and bacterial biomass. The optimisation method provided a set of optimal parameters to fit the experimental observations of ‘control’ (i.e. natural water without oysters) and ‘oyster’ (i.e. natural water with oysters) mesocosms. The modelling results showed good accordance with the experimental observations, suggesting that the oysters directly reduced phytoplankton community biomass, thus constraining the ecosystem to a more heterotrophic state. Oysters also reduced competition between bacteria and phytoplankton for nutrient uptake, favouring higher bacterial biomass than in the control experiment. Additionally, the presence of oysters strongly increased large micro-zooplankton biomass (50-200 µm; mainly ciliates and large flagellates). This was a consequence of bacterivory by small zooplankton (5-50 µm; mostly flagellates and small ciliates), providing a trophic link between bacteria and larger zooplankton. In conclusion, parameter optimisation showed good capacity to manage experimental data in order to build a more realistic model. Such models, in connection with future developments in aquaculture and global change scenarios, could be a promising tool for exploited ecosystem management and testing different environmental scenarios.

KEY WORDS: Oysters · Microbial food web · Biogeochemical modelling · Parameter optimisation · Bacteria · Phytoplankton · Zooplankton · Mesocosm

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Cite this article as: Caillibotte R, Leredde Y, Vidussi F, Ulses C, Marsaleix P, Estournel C, Mostajir B (2020) Impact of oysters as top predators on microbial food web dynamics: a modelling approach with parameter optimisation. Mar Ecol Prog Ser 641:79-100.

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