The effects of short-term increases in turbidity on sandflat microphytobenthic productivity and nutrient fluxes

Abstract Turbidity is a major limiting factor of benthic primary production and nutrient uptake on estuarine intertidal sandflats. Estuaries exhibit a wide range of suspended sediment concentrations (SSCs), however, few studies have quantified the effects of increasing SSC on ecosystem functioning. Here, we report on an in situ experiment examining the effects of short-term increases in SSC on intertidal sandflat benthic primary production and nutrient fluxes. Fine sediments ( 2 ) at concentrations ranging from 16 to 157 mg L − 1 and kept in suspension for a 4–5 h incubation period. In addition to solute fluxes we also measured sediment chlorophyll- a content and physical properties as covariables. In sunlit chambers, we observed a three-fold reduction in net primary production (NPP) with increasing SSC (NPP, R 2  = 0.36, p = 0.01) and stronger reductions when NPP was standardised by sediment chlorophyll- a content (i.e., photosynthetic efficiency, NPP chl- a , R 2  = 0.62, p  4 + , R 2  = 0.44, p  4 + efflux was solely correlated to SSC. The results of this study imply that increased exposure to SSC associated with the tidal exchange of sediments from far-field sources may severely impair benthic primary productivity and increase the flux of inorganic nutrients from benthic to pelagic systems.

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