A chlorophyll budget of the sediment-water interface and the effect of stabilizing biofilms on particle fluxes

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Abstract
We constructed a budget of chlorophyll flux (mostly benthic diatoms) for the sediment-water interface of an intertidal sandflat in Nova Scotia. The terms included deposition, resuspension, burial, primary production, and consumption (community respiration). In addition to field experiments, laboratory flume experiments were used to assess the effects of stabilizing diatom films on resuspension. Advective terms in the field were measured by following the dynamics of chlorophyll in pans of pre-combusted sand placed in the intertidal zone. Production and consumption were based on in situ oxygen flux in light and dark cores. During a single high tide in both the fall and spring, deposition was greater than resuspension. Burial was highly variable being on average 27 % of deposition. Comparing sources of input, production was 5–14 % of deposition. Comparing losses of chlorophyll, respiration was −2 · h−1 in both fall and spring experiments. Erosion of cores in a laboratory flume showed that diatom films could inhibit resuspension by 33–100 %. Incorporating these factors into the chlorophyll budget increased net flux to the sediment by 1–2 orders of magnitude. Enhanced fluxes observed in the natural sediment, 1.03 and 0 mg Chl · m−2 · h−1 in fall and spring respectively, could easily be explained by extracellular diatom films which inhibited resuspension. The stabilization of sediment by diatoms has a major effect on the potential food sources of benthic animals by regulating advective fluxes.