490 J. Phycol. 39, 490–503 (2003) EFFECTS OF METAL AND PETROLEUM HYDROCARBON CONTAMINATION ON BENTHIC DIATOM COMMUNITIES NEAR CASEY STATION, ANTARCTICA: AN EXPERIMENTAL APPROACH 1 Laura Cunningham Institute of Antarctic and Southern Ocean Studies, University of Tasmania, Box 252-77 Hobart, Australia, 7001 Jonathan S. Stark, Ian Snape Human Impacts Program, Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia Andrew McMinn 2 Institute of Antarctic and Southern Ocean Studies, University of Tasmania, Box 252-77 Hobart, Australia, 7001 and Martin J. Riddle Human Impacts Program, Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia The effects of metals and petroleum hydrocar- bons on benthic marine diatom communities were assessed using a manipulative field experiment at Casey Station, Antarctica. Uncontaminated, metal contaminated, and petroleum hydrocarbon contami- nated sediments were deployed for 11 weeks during the 1999 austral summer. The treatments were de- ployed at three different locations: Brown Bay, which has elevated levels of anthropogenic contami- nants, and two uncontaminated reference locations, O’Brien Bay and Sparkes Bay, the latter of which has naturally occurring high concentrations of some heavy metals. At each location, significant differ- ences between the composition of diatom communi- ties recruiting to control and petroleum hydrocarbon contaminated treatments were observed. Navicula di- recta (Smith) Ralfs occurred at lower abundances in the petroleum hydrocarbon contaminated treatments than in the control treatments. In contrast, Navicula cancellata Donkin occurred at higher relative abun- dances in both contaminated treatments relative to the control treatment. Interactions between treat- ment and location were also observed for several species, including Navicula glaciei Van Heurck. Sig- nificant differences in the overall community com- position of diatom communities between control and metal contaminated treatments and metal con- taminated and petroleum hydrocarbon contami- nated treatments were only observed within Brown Bay. The location of deployment also had a signifi- cant influence on the composition of diatom com- munities. Brown Bay had higher abundances of Ach- nanthes brevipes Agardh but lower abundances of Navicula aff. cincta (Ehrenberg) Van Heurck than ei- ther reference locations. This experiment demon- strated that benthic diatom communities are sensi- tive to sediment contamination and would be suitable for future monitoring work within this and other ar- eas of Antarctica. Key index words: benthic diatoms; community com- position; metal contamination; petroleum hydrocar- bons; Casey Station; Antarctica Abbreviation: SAB, special Antarctic blend diesel fuel Antarctica is widely regarded as the last remaining wilderness; however, the integrity of this environment is threatened by human activities. Increases in chemi- cal contaminants have been recorded in the marine environments around many of the permanent re- search stations (Lenihan et al. 1990). Detailed infor- mation on the extent of such contamination is avail- able for only a few sites, including McMurdo Station (Kennicutt et al. 1995, Crockett 1997) and Casey Sta- tion (Snape et al. 2001; Stark et al. in press). Informa- tion on the biological effects of such contamination is also limited to a few studies, most of which have exam- ined the effects on faunal communities (Lenihan and Oliver 1995, Stark 2000). The benthic microflora of Antarctic regions con- sists almost entirely of diatoms (Gilbert 1991). Dia- toms have been shown to have narrow tolerance ranges for many environmental variables and respond rapidly to environmental change, making them ideal bioindicators (Reid et al. 1995). Contaminants can af- fect the growth rate and species composition of dia- tom communities, with subsequent implications for organisms higher in the food chain (Stronkhurst et al. 1994). Recent studies (Snape et al. 2001, Scouller et al. 2000, Stark et al. in press) have demonstrated higher concentrations of some metals and petroleum hydro- carbons in sediments collected from bays adjacent to 1 Received 18 December 2001. Accepted 4 March 2003. 2 Author for correspondence: e-mail andrew.mcminn@utas.edu.au.