The nematodes of the Thames estuary: Assemblage structure and biodiversity, with a test of Attrillʹs linear model

Although many studies of Nematoda have been undertaken in estuarine systems, there are relatively few studies which have analysed the distribution of fauna across the entire salinity range from marine to freshwater conditions. The Thames estuary has a long history of anthropogenic impact and recovery, since it was described as ‘‘azoic’’ in the 1950s, which has been monitored primarily through studies of water quality and fish stocks, with less emphasis on macroinfauna and very little information on meiofaunal organisms. This study aimed to describe the nematode fauna at eight stations along the estuary from marine to freshwater conditions in order to assess patterns of density, diversity and species assemblage structure. Nematode density and diversity were generally lower in the middle reaches of the estuary, associated with the region of greatest salinity range, a pattern which was found to be in agreement with Attrill’s [2002. A testable linear model for diversity trends in estuaries. Journal of Animal Ecology 71, 262–269] linear model. Multivariate analysis confirmed that each station supported a distinct nematode fauna, which could be used to identify five zones along the estuary related to salinity regime. Although alpha diversity at each station was relatively low, species turnover along the estuary resulted in relatively high gamma diversity (153 spp.) similar to that found in a number of European estuaries. The results of this study did not suggest that the nematode fauna was under significant stress from the lower levels of pollution currently found in the system. The potential routes for the recovery and recolonization of the estuary since it most polluted days are discussed.