Patterns of higher taxon colonisation and development in sessile marine benthic assemblages at Casey Station, Antarctica, and their use in environmental monitoring

Colonisation and development of sessile epibiotic assemblages on tiles was studied at Casey Station, East Antarctica, using a mix of higher taxon classifications (family to phylum). Tiles were deployed for 1 and 3 yr at 3 control and 2 impacted locations. Assemblages on upper and lower surfaces of tiles were very different, with little colonisation of upper surfaces (0 to 11 % after 3 yr) and extensive colonisation of lower surfaces (60 to 91 % after 3 yr), which is greater than previously reported from Antarctica. Hypotheses were tested relating to spatial variation, depth, human impacts (a sewage outfall and a waste disposal site) and period of deployment. Differences between control locations were only apparent after 3 yr, but there were significant differences between control and impacted locations after 1 yr. There were differences between assemblages at 7 to 10 m and 19 to 22 m. Assemblages were initially dominated by spirorbid polychaetes and bryozoans, but by 3 yr there was significant sponge cover at some locations. Both impacted locations had significantly greater cover on upper surfaces than controls. The waste disposal site had the least cover on lower surfaces, with almost no sponge and less bryozoans than controls. The outfall had the greatest cover on the lower surfaces, the greatest cover of spirorbids and sponges but the least cover of bryozoans. Higher taxa assemblage patterns of colonisation on settlement panels are potentially useful as a medium-to long-term monitoring tool for sheltered Antarctic nearshore waters.