Short Term Changes of Benthic Fluxes During Clam Harvesting in a Coastal Lagoon (Sacca Di Goro, Po River Delta))

In this paper the relationships between the Manila clam (Ruditapes philippinarum) farming and benthic fluxes in the eutrophic Sacca di Goro lagoon (Po River Delta, Italy) are studied considering (1) the analysis of spatial patterns of sedimentary organic matter, acid volatile sulphide (AVS), chromium reducible sulphur (CRS) and labile amorphous iron in a grid of nine stations; (2) an assessment of the short-term oxygen consumption caused by sediment resuspension in oxygen-rich water; (3) a mesocosm experiment for evaluating the potential effects of sediment dredging on benthic fluxes of oxygen, soluble reactive phosphorus (SRP), ammonium, nitrate and dissolved reactive silica (DRSi). Our data suggest that in the farming area benthic fluxes of oxygen, ammonium and silica are driven mainly by clam respiration, whilst harvesting causes only transient modification of benthic fluxes. Therefore, we expect that clam metabolism is responsible for a persistent impact at the lagoon scale, whilst harvesting activities induce local and acute effects.