Penguins and seals transport limiting nutrients between offshore pelagic and coastal regions of Antarctica under changing sea ice

Large animals such as sea birds and marine mammals can transport limiting nutrients between different regions of the ocean, thereby stimulating and enhancing productivity. In Antarctica this process is influenced by formation and breakup of sea ice and its influence on the feeding behaviour of predators and their prey. We used analyses of bioactive metals (for example, Fe, Co, Mn), macronutrients (for example, N) and stable isotopes (δ13C and δ15N) in the excreta of Adélie (Pygoscelis adeliae) and emperor penguins (Aptenodytes forsteri) as well as Weddell seals (Leptonychotes weddellii) from multiple sites, among multiple years (2012–2014) to resolve how changes in sea ice dynamics, as indicated by MODIS satellite images, were coincident with prey switching and likely changes in nutrient fluxes between the offshore pelagic and coastal zones. We also sampled excreta of the south polar skua (Stercorarius maccormicki), which preys on penguins and scavenges the remains of both penguins and seals. We found strong coincidence of isotopic evidence for prey switching, between euphausiids (Euphausia superba and E. crystallorophias) and pelagic/cryopelagic fishes (for example, Pleuragramma antarcticum) in penguins, and between pelagic/cryopelagic fishes and Antarctic toothfish (Dissostichus mawsoni) in Weddell seals, with changes in sea ice cover among years. Further, prey switching was strongly linked to changes in the concentrations of nutrients (Fe and N) deposited in coastal environments by both penguins and seals. Our findings have important implications for understanding how the roles of large animals in supporting coastal productivity may shift with environmental conditions in polar ecosystems.Accepted manuscrip

IMPACT: The Journal of the Center for Interdisciplinary Teaching and Learning. Volume 10, Issue 2, Summer 2021

Impact: The Journal of the Center for Interdisciplinary Teaching & Learning is a peer-reviewed, biannual online journal that publishes scholarly and creative non-fiction essays about the theory, practice, and assessment of interdisciplinary education. Impact is produced by the Center for Interdisciplinary Teaching & Learning at Boston University College of General Studies. Impact accepts submissions throughout the year and publishes issues in February and July. Please submit your essays for consideration at https:// citl.submittable.com/submit. Impact provides free and open access to all of its research publications. There is no charge to authors for publication, and the journal abides by a CC-BY license. Authors published in Impact retain copyright on their articles, except for any third-party images and other materials added by Impact, which are subject to copyright of their respective owners. Authors are therefore free to disseminate and re-publish their articles, subject to any requirements of third-party copyright owners and subject to the original publication being fully cited. Visitors may download and forward articles subject to the citation requirements; all copyright notices must be displayed. If readers want to search by journal subject they might use these words: education, graduate, undergraduate, interdisciplinary, disciplines, curriculum, higher education.The theme of this issue is interdisciplinary approaches to, or including, the sciences. STEM disciplines like chemistry, biology, physics, computer science, and math are often taught as separate and distinct from the humanities. The concept of STEAM (STEM + Arts) has attempted to make STEM subjects more interdisciplinary, allowing students to interact with the material from different perspectives. The essays in this issue explore unique ways to design and implement interdisciplinary curricula that combine sciences and humanities/arts

Contribution of sea ice microbial production to Antarctic benthic communities is driven by sea ice dynamics and composition of functional guilds

Organic matter produced by the sea ice microbial community (SIMCo) is an important link between sea ice dynamics and secondary production in near-shore food webs of Antarctica. Sea ice conditions in McMurdo Sound were quantified from time series of MODIS satellite images for Sept. 1 through Feb. 28 of 2007-2015. A predictable sea ice persistence gradient along the length of the Sound and evidence for a distinct change in sea ice dynamics in 2011 were observed. We used stable isotope analysis (δ C and δ N) of SIMCo, suspended particulate organic matter (SPOM) and shallow water (10-20 m) macroinvertebrates to reveal patterns in trophic structure of, and incorporation of organic matter from SIMCo into, benthic communities at eight sites distributed along the sea ice persistence gradient. Mass-balance analysis revealed distinct trophic architecture among communities and large fluxes of SIMCo into the near-shore food web, with the estimates ranging from 2 to 84% of organic matter derived from SIMCo for individual species. Analysis of patterns in density, and biomass of macroinvertebrate communities among sites allowed us to model net incorporation of organic matter from SIMCo, in terms of biomass per unit area (g/m ), into benthic communities. Here, organic matter derived from SIMCo supported 39 to 71 per cent of total biomass. Furthermore, for six species, we observed declines in contribution of SIMCo between years with persistent sea ice (2008-2009) and years with extensive sea ice breakout (2012-2015). Our data demonstrate the vital role of SIMCo in ecosystem function in Antarctica and strong linkages between sea ice dynamics and near-shore secondary productivity. These results have important implications for our understanding of how benthic communities will respond to changes in sea ice dynamics associated with climate change and highlight the important role of shallow water macroinvertebrate communities as sentinels of change for the Antarctic marine ecosystem