Productivity • Invertebrates • Birds
Fish • Amphibians • Mammals

Invertebrates

Saltmarshes are not normally recognised for their rich and varied invertebrate fauna. They present difficult environments for colonisation by invertebrates due to the changes in salinity and humidity caused by periodic tidal immersion. However, far from being restricted in the diversity of invertebrates, saltmarshes are likely to have both a diverse and abundant fauna. The fauna is a mixture of marine, freshwater and terrestrial species which are adapted in various ways to the environment. Marine species tend to occur lower down the marsh and often burrow to avoid desiccation. Terrestrial and freshwater species occur mostly in the upper marsh and in transition zones, and have adapted to, or avoid, immersion in saline water.

Doody (1992) reports that, in Britain, terrestrial invertebrates inhabiting saltmarshes number some 293 resident species, of which 148 are found exclusively in saltmarshes. Marine species that occur in and under the marsh surface are varied and abundant, ranging in size from the smallest mud-dwelling mollusc to quite large burrowing crabs. In the higher and drier areas of the mudflat/saltmarsh interface the marine invertebrate fauna is largely limited to detrivores, such as the amphipod Corophium and the gastropod Hydrobia. Such studies as exist also suggest that, where it survives, the upper sections of marsh may be very diverse.

Differences in the distribution of species have been observed in relation to the plant communities. The presence of individual species is often closely associated with the type of vegetation that occurs.