Characterization and dynamics of particulate organic matter in a restored river floodplain system

Connections between rivers and their adjacent floodplains influence the quality and quantity of organic matter and productivity within the water column. Changing patterns lead to alternating sources of particulate organic matter (POM). In many temperate rivers, anthropogenic influence on riverine wetlands has been exerted by damming. The River Danube downstream of Vienna still represents a floodplain-system with relatively pristine hydrological-exchange patterns, where different floodplain segments exhibit gradients of connectivity according to river distance and inflow areas. Particulate organic matter dynamics are mainly controlled by the river and follow changes in autochthonous and allochthonous sources of POM. Elemental composition and stable-isotope signatures can be used as a tool to investigate compositional quality and POM. Mean δ13C signatures and C:N ratios of autochthonous POM were significantly lower than for riverine POM. Further proof for the applicability of this method was found in significant relationships between δ13C values and C:N ratios. Similar trends were found between C:N ratios and δ15N signatures, particulate organic carbon (POC):Chl-α and δ15N , and POC:Chl-α and C:N ratios. Based on these findings, conclusions about the biological relevance of POM are drawn and the importance of floodplains for ecosystem productivity is emphasized. (author)