|Title||Fe and Nutrients in Coastal Antarctic Streams: Implications for Marine Primary Production in the Ross Sea|
|Year of Publication||2017|
|Secondary Authors||W. Lyons, B|
|Academic Department||Earth Sciences|
|University||Ohio State University|
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 in the McMurdo Dry Valleys, Antarctica (MDV) from four subaerial streams flowing into the Ross Sea. They were analyzed for macronutrients (N, P, Si) and Fe to determine the potential impact of terrestrial water input on the biogeochemistry of coastal oceanic waters. Our stream data yield an average filterable composition of N3P1 Si100Fe0.8, which is substantially different from the planktonic composition as demonstrated by empirical measurements, and suggests that these streams are a potential source of Fe and P, relative to N and Si, to coastal phytoplankton communities.The behavior and potential colloidal/nanoparticulate speciation of the Fe in these streams was investigated through analysis of three physiochemical forms of Fe - environmentally active Fe (acid-soluble/no filtration), filterable Fe (filtered through 0.4 μm), and dissolved Fe (filtered through 0.2 μm). It has been suggested that the dissolved fraction is mainly nanoparticulate and represents a more bioavailable form of Fe, as compared with colloids and particles. Overall, the combined average annual flux from two MDV streams is approximately 240 moles fFe yr-1, which is consistent with previously predicted values. The dissolved fraction of Fe (<0.2 μm) was between 18% and 27% percent of the fFe, meaning the fFe pool is mostly colloidal. While the Fe flux from these streams is several orders of magnitude less than aeolian and iceberg sources, terrestrial streams are expected to become a more significant source of Fe to the Ross Sea. As the Antarctic climate warms, ice-free regions similar to the MDV should increase in extent and glacier melt. This study questions how, and in what quantities, Fe is solubilized and transported from the landscape into the SO to better inform predictions of Fe fluxes following continued warming.