The impact of encroachment and bankside development on the habitat complexity and supralittoral invertebrate communities of the Thames Estuary foreshore

1. The Thames Estuary has a long history of human habitation and industrial development, which has resulted in dramatic losses of foreshore habitat; those fragments of fringing habitats that remain are also under threat from potential encroachment onto the foreshore. This paper describes a survey that set out to document the structural complexity and invertebrate communities of 21 supralittoral sites along a 65 km section of the Thames foreshore, and to assess their conservation value. This is the first extensive survey of supralittoral habitats in an urbanized estuary. 2. Invertebrates were sampled from the supralittoral at each site and the habitat types and their structural complexity (including numbers of plant species) at each site were also documented. The relationships between habitat complexity and invertebrate communities were investigated by linear correlation and multivariate analyses. 3. There were significant positive correlations between the number of supralittoral invertebrate species, habitat complexity (measured as the number of complex habitats present) and the number of plant species at each site. 4. The community composition of supralittoral invertebrates was also related to habitat complexity, although this trend was only evident for species data aggregated to higher taxonomic groups, suggesting that chance may play a key role in the colonization of these fragmented habitats. 5. Based on species recorded, the conservation value of supralittoral sites was low; most taxa were widespread eurytopics and only one supralittoral site (Syon Park) contained a threatened species, the snail Perforatella rubiginosa. Copyright (C) 1999 John Wiley & Sons, Ltd.