ECOLOGY OF BENTHIC AND INTERSTITIAL OSTRACODS OF THE RHONE RIVER, FRANCE

The ecology of ostracods in the Rhone River was studied in the main channel of 3 sections. Twenty-four species were collected during 2 sampling periods (summer and winter). At a regional scale, diversity and density of ostracods in benthic and interstitial habitats varied markedly among the 3 sites. In the 2 sectors upstream of Lyon, ostracods represented only small proportions of the invertebrate assemblages, whereas they were a dominant group in the downstream site. These differences are linked to the eutrophication of the river and to the water exchanges between benthic and interstitial habitats. Their microdistributions were not linked to physicochemical characteristics of the sediment or the interstitial water, but seemed to be determined by geomorphological and hydrological characteristics of the sampling stations.