Control of phytoplankton production by physical forcing in a strongly tidal, well-mixed estuary

X. Desmit (1) , J. P. Vanderborght (1) , P. Regnier (2) , R. Wollast (1)

1 Laboratory of Chemical Oceanography and Water Geochemistry and Department of Water Pollution Control
2 Biogeochemical System Dynamics

A model for phytoplanktonic production in turbid, macro-tidal estuaries is proposed. It is based on the description of light-dependent algal growth, phytoplankton respiration and mortality. The model is forced by solar irradiance, mixing depth and light penetration. The extinction coefficient is directly related to the dynamics of suspended particulate matter. Model results show that the description of phytoplankton growth must operate at a time resolution sufficiently high to describe the interference between solarly and tidally driven physical forcing functions. It also demonstrates that in tidal and turbid estuaries, the short-term variation of the euphotic depth to mixing depth ratio has to be resolved for production estimates and that net positive phytoplankton production can be achieved in areas of high turbidity. The model is used to explain the typical phytoplankton decay observed along the longitudinal gradient of salinity in turbid estuaries, using the Western Scheldt as an example.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

X. Desmit, J. P. Vanderborght, P. Regnier, R. Wollast. Control of phytoplankton production by physical forcing in a strongly tidal, well-mixed estuary. Biogeosciences Discussions, 2005, 2 (1), pp.37-75. ⟨hal-00297723⟩