Persistent Organic Pollutants(POPs) as Tracers of Environmental Change and Antarctic Seabird Ecology

Antarctic seabirds including Adelie penguins (Pygoscelis adeliae), south polar skuas (Catharacta maccormicki), southern giant petrels (Macronectes gigantus) are high trophic level predators that accumulate persistent organic pollutants (POPs) present in the food webs in which they forage. Little is known about the levels of POPs in some Antarctic organisms (e.g. southern giant petrels), as well as the long-term trends of POPs in the Antarctic ecosystem. Samples from all three seabird species were collected post mortem, including eggs, from the Western Antarctic Peninsula (WAP) and in the Ross Sea throughout the austral summer breeding seasons of 2004--2006. The samples were analyzed for C and N stable isotopes and POPs including organochlorine pesticides, polychlorinated biphenyls (PCBs), and brominated diphenyl ethers (BDEs). The objectives of this study were to: (1) evaluate the long-term trends of POP residues in Adelie penguins, (2) compare POP levels within livers of the three seabird species based on migratory patterns and trophic level using stable isotope analysis of delta15N and delta13C, and (3) demonstrate POPs can be used as tracers of Antarctic seabird ecology. POPs in Antarctic biota were first evaluated using Adelie penguin tissues and a long-term analysis including data from the current study showed SigmaDDT has not declined in WAP penguins for more than 30 years. Indeed, the presence of p,p\u27-DDT in these birds indicates that there is a current source of DDT to the WAP marine food web, and both measurements and calculations suggest that this source of DDT is related to climate driven environmental change in the region. A more broad analysis including all three seabird species showed SigmaPCBs, SigmaDDTs, Sigmachlordanes and mirex are 3--100 times higher in migratory seabird livers than the endemic penguins, while hexachlorobenzene (HCB) exhibits no difference in concentration between the three seabird species. Model predictions compared to measured output of delta13C and delta13N indicate a stronger correlation between delta13C and less volatile POP concentrations demonstrating the heavy influence of winter migration on the contaminant loads of seabirds that breed in Antarctica. Finally, discrepancies in POP ratios between migratory and endemic seabird eggs and fat in combination with stable isotope signatures gave insight into seabird evolutionary breeding strategies. For example, the relative abundance of SigmaPCBs was highest in south polar skua eggs and endogenous lipid input into skua eggs was estimated at \u3e79% by examining discrepancies in contaminant ratios. The combined stable isotope and contaminant data indicate that south polar skuas and southern giant petrels employee different combinations of income and capital breeding strategies

Antarctic Ecosystem Research following Ice Shelf Collapse and Iceberg Calving Events

The calving of A-68, the 5,800 km2 iceberg that separated from the Larsen C Ice Shelf in July 2017, presents a unique and time-sensitive research opportunity. This event and other ice-shelf losses (e.g., from Larsen A and B, Wilkins, Wordie) are harbingers of warming effects along the Antarctic Peninsula in particular, and ultimately around all of Antarctica. The scientific momentum and public interest created by this most recent event led to an NSF funded workshop in November 2017. A consortium of US and international researchers with a diversity of expertise in Antarctic glaciological, geological, biological, and ecological sciences shared and reviewed the latest research, identified important research priorities and knowlegde gaps, and outlined strategic plans for the research community to advance understanding of the continent-wide changes that Antarctic ice shelves and surrounding ecosystems will experience in response to warming. The workshop has leveraged an opportunity to synergize efforts in investigating Antarctic ecosystems under the direct and indirect effects of ice-shelf collapse, and climatic warming in general. Here we present a review on the known and unknown ecosystem processes that will occur in the wake of massive, abrupt ice-shelf break-off and how they will affect ice-associated, pelagic, hard-bottom and soft-sediment substrates. We also present a view on future research approaches to address gaps in our knowledge and advance our understanding of the widespread effects of ice-shelf break-off and collapse

Antarctic ecosystem responses following ice‐shelf collapse and iceberg calving: Science review and future research

The calving of A‐68, the 5,800‐km², 1‐trillion‐ton iceberg shed from the Larsen C Ice Shelf in July 2017, is one of over 10 significant ice‐shelf loss events in the past few decades resulting from rapid warming around the Antarctic Peninsula. The rapid thinning, retreat, and collapse of ice shelves along the Antarctic Peninsula are harbingers of warming effects around the entire continent. Ice shelves cover more than 1.5 million km² and fringe 75% of Antarctica's coastline, delineating the primary connections between the Antarctic continent, the continental ice, and the Southern Ocean. Changes in Antarctic ice shelves bring dramatic and large‐scale modifications to Southern Ocean ecosystems and continental ice movements, with global‐scale implications. The thinning and rate of future ice‐shelf demise is notoriously unpredictable, but models suggest increased shelf‐melt and calving will become more common. To date, little is known about sub‐ice‐shelf ecosystems, and our understanding of ecosystem change following collapse and calving is predominantly based on responsive science once collapses have occurred. In this review, we outline what is known about (a) ice‐shelf melt, volume loss, retreat, and calving, (b) ice‐shelf‐associated ecosystems through sub‐ice, sediment‐core, and pre‐collapse and post‐collapse studies, and (c) ecological responses in pelagic, sympagic, and benthic ecosystems. We then discuss major knowledge gaps and how science might address these gaps