Contribution of the macrobenthic compartment to the oxygen budget of a large regulated river: the Mosel

Abstract

The contribution of the benthic compartment to the oxygen budget of three sectors of the river Mosel (France, Luxembourg, Germany) was evaluated, in terms of benthos respiration, filtration rate and sediment oxygen demand. Bottom substrates and benthic invertebrate communities were investigated using benthic dredges during six field campaigns from summer 1994 to summer 1996. Bivalvia (Corbicula fluminalis, Dreissena polymorpha, Anodonta cygnea, Unio pictorum), Prosobranchia (Viviparus viviparus), Crustacea (Gammaridae) and Diptera (Chironomidae) were the prevailing taxa of the benthic community, both in density and biomass. An original method based on multivariate analyses and a clustering approach was developed to describe the habitat mosaic in terms of substrate-type frequencies. The biomass of each taxon was recalculated for each substrate-type. The dissolved oxygen uptake and the filtration rate of the prevailing taxa of the benthic community were modelled using results of laboratory experiments. Both effects of water temperature and trophic level conditions were taken into account. Evaluations showed that benthic compartment respiration processes may have reach up to 25% of the total amount of dissolved oxygen per day, in the river Mosel. Furthermore, the macrobenthic compartment may have a great impact on phytoplankton communities, and then on primary production, by filtration activity. Indeed, the water volume daily filtered by filter-feeder macroinvertebrates potentially ranged from 26.9 to 83.8% of the total volume of a sector, in summer conditions. Consequently, respiration and filtration activities of the benthic compartment appear to be two important biological processes of the dissolved oxygen budget of a large regulated river.