IRON AND NUTRIENTS IN ANTARCTIC STREAMS FLOWING INTO THE ROSS SEA: POTENTIAL IMPACT ON MARINE PRIMARY PRODUCTION

The Southern Ocean (SO) has been an area of much biogeochemical interest due to the role of Fe limitation for primary production. Primary production is associated with increased carbon sequestration, making it important to characterize and quantify the fluxes of Fe and other nutrients to the ocean. Water samples were collected from five streams in the McMurdo Dry Valleys, Antarctica (MCM DV) flowing into the Ross Sea and analyzed for macronutrients (N, P, Si) and Fe to determine the potential impact of terrestrial water input on the biogeochemistry of coastal ocean. The character/speciation of the Fe in these streams was investigated through the analysis of three physiochemical forms of Fe - environmentally available Fe (acid addition/no filtration), filterable Fe (filtered through 0.4 mm), and dissolved Fe (filtered through 0.2 µm). The environmentally available Fe (EAFe) in these streams was 1-3 orders of magnitude higher than the filterable Fe (fFe). Changes in EAFe and fFe concentrations are often not in phase with each other. This variability suggests different hydrological and geochemical processes impact the distribution of these physiochemical forms. Our preliminary stream data yield an average filterable composition of N_0.9P₁ Si₄₁Fe_0.2, which is substantially different from the planktonic composition as demonstrated by empirical measurements. The current fluxes of nutrients from the terrestrial regions in the Ross Sea are probably low. As the Antarctic climate warms, ice-free regions similar to the MCM DV should increase in extent and glacier melt. This study will serve as an example of how Fe is solubilized and transported from the landscape into the SO in order to better inform predictions of Fe fluxes under future climate scenarios.