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1. Benthic communities inhabiting river-lake interfaces are confronted with temporal variation in the import of river-borne material to the associated littoral zone. The primary objective of this study was to evaluate the exposure to river-borne benthic particulate matter as a force shaping the meiofauna of the river-lake interface. 2. In a 2 · 2 factorial design, combinations of strongly and weakly river-influenced communities (near or far from the river mouth) with and without river-borne benthic particulate matter enrichment were studied in laboratory microcosms to assess the response of the heterotrophic meiobenthos to river-borne matter. 3. Nematodes dominated both habitat types and were the only meiofaunal taxon that responded to the enrichment. 4. A strong interactive effect between experimental enrichment and location of site was observed. Whereas nematodes from the littoral habitat close to the river mouth responded to the enrichment only marginally, nematodes from the remote site were strongly affected in the presence of river-borne particulate matter. 5. In the non-enriched samples of the remote site, the number of nematodes increased greatly over time. Among nematode feeding types, deposit feeders dominated over chewers at the beginning of the experiment but both types were equally abundant at the end. In the presence of river-borne matter the increase of chewers ceased and a shift in feeding type composition did not occur. 6. It was shown that for river-lake interface meiofaunal assemblages in relative proximity, the same taxon might respond differently if exposed to an external pressure, e.g. riverborne components. These components may have a stronger influence on taxa with longer life cycles.

Six sites within the littoral habitat of Lake Constance in Germany were studied from February 1999 to January 2000 in order to determine the influence of the inflowing River Schussen on local nematode assemblages. The sites were selected to represent a gradient of river influence within the broader river mouth area. The area as a whole was found to be rich in nematode diversity, with 106 nematode species identified. The nematode communities recorded ranged in density from 121 to 165 individuals/10 cm 2 and in biomass from 108 to 503 µg wet weight/10 cm 2 . They were also shown to vary in terms of feeding ecology, with significant differences in the proportions of feeding types occurring among site. Deposit feeders were most abundant, followed by chewers, although the latter dominated in terms of biomass. Epistrate feeders were less common and suction feeders rare. The occurrence of epistrate feeders was linked to the concentration of algal pigment, whereas records of deposit feeders and chewers correlated with bacterial density and organic carbon content. The characters of the different nematode communities in the vicinity of the river mouth were found to reflect the transitional nature of the study area.

The littoral nematode community adjacent to a river mouth (River Schussen) on Lake Constance (Germany) was studied from February 1999 to January 2000 in order to determine the influence of stress resulting from fluctuations in river discharge on local nematode assemblages. Additionally, the influence of wind as a second important stress factor was considered. Six sample sites were chosen, reflecting a gradient of river influence within the broader river mouth area. Nematode communities, varying in a mean range from 121 to 165 ind/10 cm 2 , were found to differ significantly in terms of abundance, feeding type composition and species diversity. Deposit feeders were most abundant at all sites followed by chewers. Deposit feeders were affected mainly by wind events, while species diversity and the occurrence of chewers were influenced mainly by river discharge. The impact of both these stress factors was modified by a third variable, water level. Moderate and high levels of combined habitat stress led to significant changes in community structure. Under conditions of calm weather and low discharge, reduced species diversity and an increased predominance of deposit feeders were observed. In most cases, species diversity was found to be higher under moderate stress conditions, an observation that offers support for Connel's Intermediate Disturbance Hypothesis.