Relationships between suspended and sediment organic matter in a semi-enclosed marine system: the Stagnone di Marsala Sound (Western Sicily)

To gather information on the interactions between the sediment and suspended organic matter pools in the Stagnone di Marsala, water and sediment samples were collected, on a monthly basis, at 11 stations. Water temperature and salinity showed a clear seasonality whilst particulate and sediment organic matter did not show any clear seasonal pattern. Relative abundances of suspended and sediment organic matter, on the other hand, appeared to be site-dependent and controlled mainly by the dynamic balance between resuspension and sedimentation. High quantities of both suspended and sediment total organic matter were present, while very low algal biomasses (in terms of chlorophyll-a concentrations) were observed both in the suspended and sediment pools thus showing the oligotrophy of the site. The contribution of phytoplankton and microphytobenthos to the total organic content of suspended and sediment matter was negligible. The low food availability of organic matter in the Stagnone di Marsala Sound may explain the low abundance of suspension-feeding molluscs, which are substituted by limnovore and detritivore species.