Ann. N.Y. Acad. Sci. ISSN 0077-8923 ANNALS OF THE NEW YORK ACADEMY OF SCIENCES Issue: The Year in Ecology and Conservation Biology Anthropogenic impacts on marine ecosystems in Antarctica Richard B. Aronson, 1 Sven Thatje, 2 James B. McClintock, 3 and Kevin A. Hughes 4 1 Department of Biological Sciences, Florida Institute of Technology, Melbourne, Florida. 2 School of Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, United Kingdom. 3 Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama. 4 British Antarctic Survey, Natural Environment Research Council, Cambridge, United Kingdom Address for correspondence: Richard B. Aronson, Department of Biological Sciences, Florida Institute of Technology, 150 West University Boulevard, Melbourne, Florida 32901. raronson@fit.edu Antarctica is the most isolated continent on Earth, but it has not escaped the negative impacts of human activity. The unique marine ecosystems of Antarctica and their endemic faunas are affected on local and regional scales by overharvesting, pollution, and the introduction of alien species. Global climate change is also having deleterious impacts: rising sea temperatures and ocean acidification already threaten benthic and pelagic food webs. The Antarctic Treaty System can address local- to regional-scale impacts, but it does not have purview over the global problems that impinge on Antarctica, such as emissions of greenhouse gases. Failure to address human impacts simultaneously at all scales will lead to the degradation of Antarctic marine ecosystems and the homogenization of their composition, structure, and processes with marine ecosystems elsewhere. Keywords: Antarctic Treaty; Antarctica; biodiversity; biological invasion; biotic homogenization; conservation; global warming Introduction Although terrestrial impacts in Antarctica have been recognized for decades, 1–3 the marine systems were assumed to be protected from human influ- ences by two attributes: the physical barrier to wa- ter exchange created by the Antarctic Circumpolar Current (ACC; Fig. 1) and the related physiologi- cal barrier created by cold sea temperatures at high southern latitudes. The ACC, one of the most pow- erful ocean currents on Earth, has physically isolated the Southern Ocean (SO) from adjacent seas for mil- lions of years. The oceanographic frontal system of the ACC, especially the Polar Front (known as the Antarctic Convergence in the more traditional lit- erature), also protects the SO physiologically from life thriving in warmer, Subantarctic waters. The steep drop in temperature across the Polar Front is a major physiological barrier to colonization by any organism insufficiently adapted to polar tempera- tures. For example, the absence from Antarctic wa- ters of reptant decapod crustaceans (benthic, walk- ing decapods, including brachyuran crabs, astacid lobsters, and anomuran king crabs) is a direct result of their physiological intolerance of cold sea tem- peratures. 4,5 A recent review of the geography of human im- pacts on marine ecosystems described the waters surrounding Antarctica as being among the least affected in the World Ocean. 6 This ranking is no cause for celebration considering the multifarious crises facing marine ecosystems worldwide; not do- ing as poorly as others that are in terrible shape is hardly tantamount to having a clean bill of health. Furthermore, the assessments of the polar regions were limited by gaps in scientific information and did not include projections of future impacts. 6 The marine ecosystems of Antarctica face imme- diate impacts on local to regional scales that include overfishing, pollution, and the introduction of alien species. They are also vulnerable to longer-term impacts from global climate change, specifically doi: 10.1111/j.1749-6632.2010.05926.x 82 Ann. N.Y. Acad. Sci. 1223 (2011) 82–107 c  2011 New York Academy of Sciences.