Biogeochemistry of the MAximum TURbidity Zone of Estuaries (MATURE): some conclusions

In this paper, we give a short overview of the activities and main results of the MAximum TURbidity Zone of Estuaries (MATURE) project. Three estuaries (Elbe, Schelde and Gironde) have been sampled intensively during a joint 1-week campaign in both 1993 and 1994. We introduce the publicly available database, and compare trends and patterns in suspended matter, nutrients and organic matter in the three estuaries. Despite the large differences in suspended particulate matter concentrations between the estuaries, some general relationships can be deduced. Organic matter dynamics is shown to be determined by sorption onto the particulate matter. This in turn induces a predictable change in bacterial degradability. Floc size, determined by an in situ camera, is a function of organic content, suspended matter concentration and (in a highly non-linear way) salinity. Higher trophic levels in the biological system are negatively affected by the dilution of their food with indigestible particles.