Abstract
AbstractMicrophytobenthos (MPB) resuspension is a key mechanism in the transfer of organic matter from productive intertidal mudflats to terrestrial and marine systems. In this study, we infer on the contribution of physical and biological factors involved in the MPB resuspension. We use a physical‐biological coupled model forced by realistic meteorological and hydrodynamical forcings to simulate chronic (without any concomitant sediment resuspension) and massive (driven by bed failure) resuspension over a year. The model simulates mud surface temperature, MPB growth, and grazing by the gastropod Peringia ulvae. The model suggests that MPB resuspension is the highest in spring tides and at the flood beginning due to high current velocity and low water heights that promote waves‐sea bottom interactions. The seasonal export of MPB biomass is the highest in spring, up to threefold higher than in summer when the export is the lowest. The simulated seasonal dynamics of MPB resuspension results from the MPB biomass concentration in the sediment, physical disturbances, and the bioturbation activity by P. ulvae. Annually, 43% of the simulated MPB primary production is resuspended. The MPB resuspension (60.8 g C·m−2·yr−1) exceeds the loss by P. ulvae grazing (41.1 g C·m−2·yr−1). The model suggests that chronic and massive resuspension events are important in the synoptic to seasonal MPB dynamics in temperate intertidal mudflats. Accounting for such processes in the carbon budget assessment in the land‐ocean interface could bring new insights to our understanding of the role played by MPB in the coastal carbon cycle.
Highlights
Tidal flats play a key role in the structure and functioning of coastal areas (Healy et al, 2002; Millenium Ecosystem Assessment, 2005)
Our study aims to simulate with a numerical model the biologically mediated chronic and physically driven episodic massive resuspension of microalgae on an intertidal mudflat for year 2012
The model reasonably simulates the seasonal pattern of MPB resuspension and gives some insights to our understanding of the contribution of the physical and biological mechanisms controlling the MPB export from the sediment to the water column:
Summary
Tidal flats play a key role in the structure and functioning of coastal areas (Healy et al, 2002; Millenium Ecosystem Assessment, 2005). The MPB photosynthetic rate is driven by mud surface temperature (MST) and solar irradiance (Barranguet et al, 1998; Cartaxana et al, 2013; 2015; Perkins et al, 2010; Vieira et al, 2013). At optimal levels, they drive a high MPB primary production (PP) up to 1.9 g C m−2 day−1 (Underwood & Kromkamp, 1999). In addition to the direct export to benthic food webs through grazing (Herman et al, 2000; Jardine et al, 2015; Kang et al, 2006; Lucas et al, 2001), MPB sustain pelagic suspensive and filter feeders, such as herbivorous fishes and zooplankton, as well as wild or farmed shellfishes (Krumme et al, 2008; Leroux, 1956; Newell et al, 1989; Paulmier, 1972; Perissinotto et al, 2003)
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