Browsing by Subject "Antarctica"

High-resolution bio-logging tools were used to examine the fine-scale foraging behaviors of humpback whales (Megaptera novaeangliae) in the coastal waters of the Western Antarctic Peninsula during the austral autumn of 2009 and 2010. Discrete feeding events (i.e., lunges) were inferred from the biologging records of thirteen whales, including a mother and her calf. In general, humpback whales exhibited efficient foraging behaviors that allowed them to maximize energetic gains and minimize energetic costs as predicted by optimal foraging theory. They fed at a continuous and high rate in the upper portion of the water column (< 100 m) from approximately dusk to dawn when their prey (Antarctic krill, Euphausia superba) were most vulnerable and less costly to acquire (i.e., near the surface). When forced to dive to greater depths, they adjusted their behaviors (e.g., descent and ascent rates) so that they could maximize their foraging durations and increase their lunging rates. In addition, humpbacks appeared to accept short term (i.e., dive by dive) costs associated with depleted oxygen stores in favor of maximizing long term (i.e., daily) energetic gains. Such efficient behaviors are particularly beneficial for mother-calf pairs who have additional energetic costs associated with foraging, such as lactation (mother), growth (calf), and maintaining proximity. In addition, because the physiology of humpback whales is poorly understood yet critically important for predicting their behaviors in response to fluctuations in their environmental conditions, foraging behaviors inferred from the bio-logging records were used to estimate their metabolic rates, oxygen storage capacities, and oxygen replenishment rates under the framework of optimal foraging theory. This research suggests that the current techniques used to estimate humpback whale oxygen stores is appropriate but that the estimation of metabolic rates of humpbacks while foraging and while traveling need to be addressed further. This work aims to increase the current understanding of humpback whale foraging behaviors along the Western Antarctic Peninsula so that appropriate measures can be taken to aid in their recovery and in the sustainability of the Antarctic marine ecosystem.

Ice shelf coverage in Antarctica is declining due to recent global warming. The northern part of Larsen Ice Shelf, the Larsen A in the Weddell Sea, has been decreasing since the 19th century and in 2000 finally disappeared. Ice shelf coverage decrease should dramatically enhance biological productivity in surface water and organic matter flux to the seafloor. This dissertation examines sources of organic matter to sediments, indicators of labile organic matter flux increase due to the ice-shelf collapse, and potential subsequent impacts of changing ocean productivity on the sedimentary microbial community in the sediment cores taken across a 170-year chronoseries of ice-shelf loss, five-transect stations. Characterizing lipid biomarkers, phytoplankton (rather than terrestrially derived organic material) was identified as the major source of organic matter in the sediments, as previously found in other nearshore Antarctic regions. The predominance of C16, C18, and C20 fatty acids, 24-methylenecholesterol, sitosterol, and 13C-enriched sea-ice diatom biomarker (C25:2 HBIs) indicate the importance of organic matter inputs from sea-ice diatom communities that become more dominant as the prevalence of sea ice coverage once the ice shelf disappears. Bacterial and Archaeal lipids were second and third largest lipid sources. These lipids could be sourced from the water column and in situ production as well as former ice shelf and ice-rafted debris. Using the vertical lipid distributions, diagenetic models were applied to estimate the pelagic lipid flux before and after the ice shelf collapse. The results suggest that the rapid increase in flux due to the ice shelf disintegration, but further characterization of degradation rates need to be undertaken to increase confidence in the magnitude of this increased flux. Lipid flux increase may induce a shift in the microbial community structure in the sediments. Multivariate analyses identified that the organic matter content and δ13CTOC values, relative abundances of labile and recalcitrant lipid biomarkers, and concentrations of nitrogen species are important factors that correlate with downcore and cross-shelf microbial community composition. Enriched organic matter content (electron donor) may influence the microbial community through the decreased availability of electron acceptors in the sediments. The quality of the organic matter may also influence the microbial community: microbes that use recalcitrant organic matter shift to phytodetritus degraders as more-labile organic matter is delivered to the seabed following ice-shelf collapse. These results will offer a new perspective on the potential impacts of the ice-shelf disintegration to the subseafloor environment. Further investigations are needed to quantify the flux increase and microbial degradation rates of organic matter to expand the knowledge on influences of glacier melt on biogeochemical cycle.

In recent decades, habitat degradation and loss, transboundary pollution, resource overexploitation, and a rapidly changing climate have contributed to significant declines in global marine biodiversity. This global environmental crisis has inspired international environmental regimes, such as the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR), to manage human activity and ensure the long-term persistence of biodiversity by establishing large-scale networks of marine protected areas (MPAs). Conservation scientists have developed systematic methods for identifying where it is most efficient to establish MPAs, but the design and implementation of effective MPAs has been hindered by limited resources, conflict over altered access to natural resources, and insufficient spatial data. Prior research has shown that incorporating social, economic, and political considerations into the design, negotiation, and establishment of MPAs can help to overcome these challenges and more effectively achieve conservation objectives. Here, I contribute to the field of conservation planning in three ways. First, I use collaborative governance theory as a framework for analyzing the CCAMLR and identifying the key factors that lead to successful agreements to designate MPAs in the Southern Ocean. Second, I build a methodological framework that operationalizes conservation opportunity theory and enables the collection of spatially referenced social, economic, and political data. Third, I use forecasting techniques to predict the likelihood that various geographic areas along the Western Antarctic Peninsula are successfully designated and suggest how these methods can inform conservation planning. My work suggests that theories and methods from other fields have the potential to improve conservation planning efforts by structuring the integration of novel spatial data, highlighting barriers to progress, identifying structural or procedural gaps in international environmental regimes, and more broadly informing conservation decision-making. Strengthening these planning approaches is increasingly critical to the success of international conservation efforts focused on protecting biodiversity and the ecological integrity and function of the global environment.