Southern Ocean Iron Experiments (SOFeX) – Collaborative Research

Sponsored by NSF – Division of Ocean Sciences
Principle Investigator: Paul G. Falkowski

This component of the Southern Ocean iron enrichment experiment is designed to provide the instrumentation and expertise for biophysical assessment of the factors limiting phytoplankton photosynthesis in the open waters of the Antarctic Ocean. Our techniques incorporate both real-time, continuous underway measurements, as well as discrete sample analysis and include: fast repetition rate (FRR) fluorometry, single-celled fast repetition rate (SCFRR) fluorometry, and low temperature fluorescence excitation/emission spectroscopy. These “tools” are capable of sensitively and reliably detecting and quantifying intrinsic biophysical limitations of phytoplankton photosynthetic processes, and provide diagnostic profiles for specific limiting factors such as iron. This program element (1) provides key data that directly tests the iron limitation hypothesis for high nutrient, low chlorophyll waters in the Southern Ocean, (2) quantifies the temporal and spatial photosynthetic responses to the iron enrichment, (3) provides the capability for real-time adaptive sampling within an enrichment area, and (4) helps to determine the taxonomic components that are iron limited, and to understand their responses to enrichment.

We propose to evaluate all of the basic variable fluorescence characteristics at sea. We will also perform post-cruise measurements.