Macrozoobenthos abundance and community composition in three lower Rhine floodplain lakes with varying inundation regimes

Abstract

AbstractThe relative importance of lake inundation regime, littoral substrate and season for macrozoobenthos abundance and community composition was studied in three Lower Rhine floodplain lakes situated along a flood duration gradient. In each lake the macrozoobenthos density, biomass and community composition were determined monthly over one year in two contrasting littoral substrates (sandy‐mineral sediments and clayey‐organic sediments). The influence of the lake inundation regime on the macrozoobenthos abundance was tested against those of littoral substrate and season with a three‐way analysis of variance (ANOVA). Between‐lake variation in macrozoobenthos abundance was clear for Bivalvia, Ephemeroptera, Heteroptera and Trichoptera. Bivalvia (Pisidium sp.) were most abundant in the frequently flooded lake, Heteroptera [Micronecta sp., Sigarafalleni (Fieber), S. striata (L.)] in the rarely flooded lake and Trichoptera [Mystacides longicornis (L.), M. nigra (L.)] and Ephemeroptera [Caenis horaria (L.), C. luctuosa Burmeister] in the isolated, non‐flooded lake, suggesting an impact of inundation regime on the abundance of these dominant taxa in Lower Rhine floodplain lakes. In each lake the annual average abundance of macrozoobenthos was dominated by Gastropoda [Bithynia tentaculata (L.), Potamopyrgus antipodarum (Gray), Valvata piscinalis (Müller)].Between‐lake variations in the relative densities of macrozoobenthos functional feeding groups suggests an impact of the inundation regime on the macrozoobenthos communities via the availability of nutritional resources. Relative densities of filter‐feeders (e.g. Pisidium sp.) were highest in the frequently flooded lake with its high phytoplankton biomass and poorly developed vegetation. Shredders (e.g. Mystacides sp.) were most numerous in the non‐flooded lake with its well developed aquatic vegetation and low phytoplankton biomass.Within‐lake variations in macrozoobenthos abundance could be attributed to littorai substrate and season. The importance of substrate on macrozoobenthos abundance was most clear for Oligochaeta and Trichoptera. The importance of season on macrozoobenthos abundance was clear for the total macrozoobenthos and for all taxonomic groups, except Oligochaeta. Correlations between the total macrozoobenthos abundance and seasonally fluctuating parameters, i.e. flood pulse duration, water level, water temperature and vegetational coverage in the lakes, suggest that hydrological parameters were most important in the frequently flooded lake, whereas vegetational coverage and water temperature were most important in the isolated, non‐flooded lake.