Intellectual Merit: Pleuragramma antarcticum, the Antarctic silverfish, play a key role in the trophic pyramid of the Antarctic coastal ecosystem, acting as food for larger fishes, flying and non-flying seabirds, pinnipeds, and whales. In turn, they are predators on coastal euphausiids, including both Euphausia superba and crystallorophias. Historically, Pleuragramma have been an important food source for Adélie Penguins of the Western Antarctic Peninsula (WAP), but during the last decade Pleuragramma have disappeared from the Adélie diet. We suggest that Pleuragramma?s absence from the diets of top predators is linked to the declining sea ice canopy, which serves as a nursery for eggs and larvae during the austral spring. The research will investigate four hydrographic regimes over the WAP continental shelf with the following features: (1) persistent gyral flows that act to retain locally spawned larvae, (2) spring sea ice that has declined in recent years (3) the prevalence of adult silverfish, and (4) the presence of breeding Adélie penguins whose diets vary in the proportions of silverfish consumed. The research will evaluate the importance of local reproduction versus larval advection, and the extent to which populations in the subregions of study are genetically distinct, via analysis of population structure, otolith microchemistry and molecular genetics of fish. The Pleuragramma data will be compared with penguin diet samples taken synoptically.
Broader Impacts: The proposed research brings together an international group of scientists with highly complimentary suites of skills to address the fate of Pleuragramma on the WAP shelf. Graduate students will use the data acquired as part of their Ph.D research, and will receive cross-training in ornithological field techniques, molecular genetic methods and otolith isotope chemistry. The PIs will work actively with the St. Petersburg Times to produce a blog in real time with pictures and text, which will be used to interact with local schools while we are at sea and after our return. The investigators also will collaborate with the COSEE center at USF and at local schools and museums to disseminate results to the K-12 community throughout the region.
Pelagic fishes and invertebrates were sampled with 32 midwater trawls at nine sites along the Western Antarctic Peninsula (WAP) in the austral fall (March – April) of 2010. Study sites were located within four hydrographic regions running from north to south : a northern region near Joinville Island in Region I, near Anvers Island and Palmer Station in Region II, within Marguerite Bay and the Marguerite Trough in Region III, and a southern region near Charcot Island in Region IV. A total of 62 species were captured and cluster analysis identified distinct multispecies groups characteristic of each of the four regions. Unlike most coastal regions of the Antarctic, e.g. McMurdo Sound, the regional groups found along the Antarctic peninsula comprise a mix of open-ocean and Antarctic coastal species. In other areas of the Antarctic, the very cold coastal waters exclude oceanic fishes. The Antarctic silverfish, an important player in the Antarctic coastal system, was captured in the northernmost and southernmost regions of the peninsula but was completely absent near Palmer Station, a site where it was formerly abundant. It is believed that regional warming is ultimately responsible for the mid-peninsula population collapse and direct mechanisms of its cause are currently being examined.
