Summary
A series of recruitment experiments using Artificial Substrate Units were deployed in the nearshore waters of Casey Station, (66o17’S, 110o32’E) to investigate spatial and temporal variation in the community structure of small motile invertebrates. The ASUs were each made of three nylon mesh pot scourers and were deployed using weighted trays. The standard deployment period was 12 months at a depth of 14 metres. Short term recruitment patterns were investigated during the austral summers of 2002 and 2003. The experiments were conducted to determine the efficacy of ASUs as a sampling protocol for environmental monitoring at Casey Station. Although employed elsewhere, this is the first time this technique has been used to sample benthic macrofaunal communities in Antarctic continental marine waters. In this study, ASUs were deployed at sites chosen to compare contaminated and pristine locations as well as to assess small scale variation within sites. To date 78 taxa have been identified from the ASUs. The assemblage is dominated by peracaridean crustaceans (isopods, amphipods and tanaids), polychaetes and gastropods. Crustacea are the most diverse group with 35 species and gastropods are the most abundant group. Species that are often numerically dominant in the samples are Skenella paludionoides (Gastropoda), Antarctogeneia macrodactyla (Gammaridea), Spirobis sp. (Polychaeta), Cymodocella tubicauda (Isopoda) and Nototanais dimorphus (Tanaidea). The assemblages demonstrated high levels of natural variation, with significant differences between sites. Multivariate analyses show strong grouping in nMDS plots clearly separating contaminated and pristine locations. Benthic marine invertebrate communities have been used to monitor environmental health in many locations throughout the world. These studies reveal the sensitivity of marine invertebrates to both natural and anthropogenic changes to their habitats. They also demonstrate that studies which focus on dynamic processes such as recruitment can be particularly sensitive to anthropogenic disturbance. Although characteristics of the numerical structure of the community, such as low diversity, may be indicative of stress, specific baseline information is necessary as the foundation for any effective monitoring protocol. ASUs provide a standardised, easily replicated method for sampling marine benthic invertebrate communities. The ability to deploy ASUs at chosen locations makes them a valuable tool in experiments addressing specific ecological questions. By employing passive recruitment as a sampling method, this technique has the potential to be sensitive to the affects of contaminants on the processes of establishment in Antarctic benthic communities.