Phytoplankton versus macrophyte contribution to primary production and biogeochemical cycles of a coastal mesotidal system. A modelling approach

Type Article
Date 2015-11
Language English
Author(s) Plus MartinORCID1, Auby IsabelleORCID2, Maurer Daniele2, Trut Gilles2, Del Amo Y.3, Dumas Franck4, Thouvenin Benedicte4
Affiliation(s) 1 : IFREMER, DYNECO PELAGOS, F-29280 Plouzane, France.
2 : IFREMER, LER AR, F-33120 Arcachon, France.
3 : Univ Bordeaux, UMR EPOC, F-33615 Pessac, France.
4 : IFREMER, DYNECO PHYSED, F-29280 Plouzane, France.
Source Estuarine Coastal And Shelf Science (0272-7714) (Academic Press Ltd- Elsevier Science Ltd), 2015-11 , Vol. 165 , P. 52-60
DOI 10.1016/j.ecss.2015.09.003
WOS© Times Cited 11
Keyword(s) Primary production, Macrophyte, Phytoplankton, Biogeochemical cycle, Physical-ecological coupled model, Arcachon bay
Abstract This study presents an assessment of the contributions of various primary producers to the global annual production and N/P cycles of a coastal system, namely the Arcachon Bay, by means of a numerical model. This 3D model fully couples hydrodynamic with ecological processes and simulates nitrogen, silicon and phosphorus cycles as well as phytoplankton, macroalgae and seagrasses. Total annual production rates for the different components were calculated for different years (2005, 2007 and 2009) during a time period of drastic reduction in seagrass beds since 2005. The total demand of nitrogen and phosphorus was also calculated and discussed with regards to the riverine inputs. Moreover, this study presents the first estimation of particulate organic carbon export to the adjacent open ocean.

The calculated annual net production for the Arcachon Bay (except microphytobenthos, not included in the model) ranges between 22,850 and 35,300 tons of carbon. The main producers are seagrasses in all the years considered with a contribution ranging from 56% to 81% of global production. According to our model, the -30% reduction in seagrass bed surface between 2005 and 2007, led to an approximate 55% reduction in seagrass production, while during the same period of time, macroalgae and phytoplankton enhanced their productions by about +83% and +46% respectively. Nonetheless, the phytoplankton production remains about eightfold higher than the macroalgae production. Our results also highlight the importance of remineralisation inside the Bay, since riverine inputs only fulfill at maximum 73% nitrogen and 13% phosphorus demands during the years 2005, 2007 and 2009. Calculated advection allowed a rough estimate of the organic matter export: about 10% of the total production in the bay was exported, originating mainly from the seagrass compartment, since most of the labile organic matter was remineralised inside the bay.
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Plus Martin, Auby Isabelle, Maurer Daniele, Trut Gilles, Del Amo Y., Dumas Franck, Thouvenin Benedicte (2015). Phytoplankton versus macrophyte contribution to primary production and biogeochemical cycles of a coastal mesotidal system. A modelling approach. Estuarine Coastal And Shelf Science, 165, 52-60. Publisher's official version : , Open Access version :