Variability in the benthic Mn flux in coastal marine ecosystems resulting from temperature and primary production1

The flux of Mn2+ from estuarine sediments contained in large cylinders was studied over a 14‐month period by periodically capping the entire 2.5‐m2 sediment surface with a benthic chamber. The seasonal magnitude in the Mn2+ flux could be described by an exponential function of the temperature. However, the flux at a given temperature varied by a factor of 6–10. During summer (June–September), Mn flux was strongly correlated not to temperature but to the average primary productivity during the month preceding the flux determination. Significant correlations between Mn flux and primary productivity were also obtained for discrete 15‐day intervals up to 68 days before the flux measurement. Postflux correlations were not significant except for a 2‐week interval immediately following the measurement when annual data were considered. The results suggest that the input of new organic matter to the sediments exerts a major control over the production of Mn2+ in anoxic sediments and that temperature relationships alone do not predict the magnitude nor variability in benthic Mn flux.