Tidal cycle control of biogeochemical and ecological properties of a macrotidal ecosystem

Type Article
Date 2017-08
Language English
Author(s) Cadier Mathilde1, Gorgues Thomas2, Lhelguen Stephane1, Sourisseau Marc3, Memery Laurent1
Affiliation(s) 1 : IFREMER, CNRS, Lab Sci Environm Marin, UMR,IRD,UBO 6539, Plouzane, France.
2 : IFREMER, Ctr Brest, Lab Oceanog Phys & Spatiale, CNRS,IRD,UMR,UBO 6523, Plouzane, France.
3 : IFREMER, Ctr Brest, Dept Dynam Environm Cotier PELAGOS, Plouzane, France.
Source Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2017-08 , Vol. 44 , N. 16 , P. 8453-8462
DOI 10.1002/2017GL074173
WOS© Times Cited 11
Keyword(s) macrotidal ecosystem, spring, neap tidal cycle, semidiurnal cycle, phytoplankton communities, diversity, competition

In some regions, tidal energy can be a key factor in the generation of variability in physical and biogeochemical properties throughout the water column. We use a numerical model resolving tidal cycles and simulating diversity in phytoplankton to assess the impact of tidal mixing on vertical stability and phytoplankton community (total biomass and diversity) in a macrotidal sea (Iroise Sea, France). Two different time scales have been considered: semi-diurnal and spring/neap tidal cycles. Our results show that the latter is the one primarily influencing the phytoplankton growth conditions by modifying the vertical stratification. During spring tide, the growth is rather light-limited whereas neap tide conditions lead to vertical stabilization and better light conditions in the shallow surface layer. The transition from high to low tidal mixing conditions is thus associated with a total phytoplankton biomass increase (caused by the rapid development of fast-growing diatoms) and reduced phytoplankton diversity.

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