The Effect of Resuspension on Primary Production

Abstract

In a physically-forced environment, the rate of net areal production may be driven by resuspension of benthic algae and sediment. Short-term (hourly) shifts in the number of photosynthetic organisms and in the attenuation of light may be greater than variation between days. The effect of resuspension on net areal production can be described by a simple model derived from that developed by Tailing (New Phytologist 56:133–149, 1957). The model is based on four dimensionless parameters: relative changes in suspended chlorophyll (Chl’) and the diffuse attenuation coefficient (k’); the ratio of total incident light to that saturating photosynthesis (Io/Ik); and the relative photosynthetic capacities of benthic and suspended algae (BP/SP). Chl’ and k’ are not dependent; their relationship depends on the relative suspensibility of benthic algae and sediment. Where benthic algae are more easily suspended than the sediment, resuspension enhances net areal production. Otherwise, the decrease in light penetration as sediment is suspended outweighs the effect of the increase in the number of potential primary producers and production drops. The sensitivity of net areal production to resuspension is highest when Io/Ik and BP/SP are high and is lowest when Io/Ik and BPSP are low. The relationships described by the model are compared to experimental data of fluxes of chlorophyll, attenuation, incident light, and the photosynthesis-irradiance parameters of suspended and benthic algae.