Local and regional shifts in phytoplankton abundance and community structure along the western Antarctic Peninsula

Maria T Kavanaugh, Woods Hole, mkavanaugh@whoi.edu (Presenter)
David M. Glover, Woods Hole Oceanographic Institution, dglover@whoi.edu
Hugh Ducklow, Lamont-Doherty Earth Observatory, Columbia University, hducklow@ldeo.columbia.edu
Oscar Schofield, Rutgers University, oscar@imcs.rutgers.edu
Scott Doney, Woods Hole Oceanographic Institution, sdoney@whoi.edu

The western Antarctic Peninsula (WAP) is experiencing dramatic climate change as maritime conditions expand poleward and interact with local physics and topography, causing differential regional effects on marine ecosystems. At local scales, deep troughs (or canyons) bisect the continental shelf and act as conduits for warm Upper Circumpolar Deep Water, provide a reservoir of macro and micronutrients, changing phytoplankton dynamics. Shoreward of many canyon heads are Adélie penguin breeding colonies; it is hypothesized that these locations reflect improved or more predictable access to higher biological productivity. On regional scales, seasonal sea ice coverage, coastal physiography and glacial melt result in both latitudinal and cross shelf gradients in phytoplankton production and community structure. Biological-physical dynamics related to canyons and across the WAP were compared using in situ pigments and several satellite-derived variables. These variables included satellite-derived sea surface temperature, sea ice, chlorophyll-a (chl-a), fucoxanthin derived semi-empirically from remote sensing reflectance, and the > 20 um size fraction of chl-a derived from the spectral slope of scattering. Canyons exhibited higher SST and reduced sea ice relative to adjacent shelves. In the central and southern WAP they also exhibited increased chl-a, and fucoxanthin during high ice conditions. Regional patterns during the recent satellite record (1997- present), show decreased sea-ice and increased SST across the entire WAP shelf. Chl-a appears to be increasing in the southern WAP and decreasing in the northern WAP although the pivot point appears to be south of previous assessments. Shelf-wide decreases in the microphytoplankton are also evident. Locally, canyons appear to support a phytoplankton community conducive to both grazing by krill and enhanced vertical export. However, the positive effects likely cannot compensate for decreased biomass and shifts toward smaller size fractions as seasonal sea-ice declines

Presentation Type:  Poster

Session:  General Contributions   (Tue 4:35 PM)

Associated Project(s): 

• Doney, Scott: Climate-Driven Impacts on the Marine Ecology, Biogeochemistry, and Carbon Cycle of the West Antarctic Peninsula ...details

Poster Location ID: 90