Examining Southern Ocean natural iron fertilization through a bio-optical lens

Primary productivity in the Southern Ocean is seasonally limited by the micronutrient iron. Shipboard observations in this region have historically been sparse, limiting our understanding of how iron modulates productivity both at Southern Ocean basin and annual scales, and in remote coastal Antarctic regions. Bio-optical observations from autonomous platforms—biogeochemical ocean profiling (BGC-Argo) floats and animal-borne sensors (seal tags)—can offer critical information on phytoplankton responses to iron stress and its relief and provide a basis for quantifying net community productivity and carbon export across broad spatial and temporal scales. In this seminar, I will discuss three studies in which we (a) used 11 years of BGC-Argo fluorometry, nitrate and oxygen data to investigate the effects of widespread iron supply by windblown mineral dust on Southern Ocean phytoplankton and carbon cycling, and (b) attempt to infer the spatiotemporal variability of iron sources in Antarctic coastal polynyas from seal tag-derived photophysiological metrics. This work showcases the exceptional coverage of the Southern Ocean bio-optical sensor array and its unique applications in studying the broad influence of natural iron fertilization on polar ecosystems.