The main aim of this case study was to determine the quality and composition of suspended organic matter in near-bottom fluxes at a mooring station (Odas Tonne) 20 km north-north-west of the Odra river mouth from June to December 1997. Salinity data and high concentrations of suspended matter near the bottom showed that the material entering the Pomeranian Bay from the Odra flood was recognisable for about three weeks. Vertical sediment fluxes, however, were low ~ 40 g m-2 d-1 compared to those measured later in the year ~ 60 g m-2 d-1.
On the other hand, average molar CNP ratios in sediment trap material decreased from June to December 1997. These results may have been a combined effect of dilution and material transport in a layer close to the sediment surface. Fluff layers sampled at Odas Tonne in August 1997 contained a very high proportion of branched fatty acids of bacterial origin, indicating high rates of bacterial degradation. Long-chain fatty acids indicated an origin from higher terrestrial plants. The saturated fatty acid content was high in the surface sediment and the traps, increasing towards the top trap.
The percentage composition of fatty acids indicated that the lowest trap was fed mainly by material from the underlying sediment. Low salinities, variability in molar ratios for major elements, higher than usual bacterial activities and detection of fatty acids characteristic of land plants during the June-August deployment show a relationship with the Odra flood of summer 1997.