Project: CAREER: Building a more expansive understanding of Fe adaptation in marine phytoplankton across the global oceans

NSF Award Abstract:
Phytoplankton are responsible for roughly half of global photosynthesis. For this reason it is important to understand what controls their growth on a global scale. Iron is an essential nutrient for phytoplankton and it limits their growth in roughly a third of the world's oceans where it is chronically low in supply. Prior research on iron adaptation of phytoplankton has understandably focused mostly on populations from these regions; however, we know less about adaptation to iron conditions in the other two-thirds of the oceans. Furthermore, prior studies have often focused on a few populations from just one or two oceanic regions and with only a few conditions (iron limited and replete). What is needed is a more expansive framework of study that encompasses many globally relevant populations and over several iron conditions. This work aims to build a fuller understanding of how iron impacts phytoplankton by studying growth responses and gene regulation over a spectrum of iron levels on many different phytoplankton populations that span the global oceans. This project in particular targets phytoplankton beyond just those from chronically low-iron regions and includes those from regions with low, medium, or high levels of iron and relatively stable or variable iron levels over time. Authentic research experiences provide a means to help address the problem of inequitable representation in STEM fields, but access to and capacity for such educational experiences is often limiting. This project helps address these problems by building creative, authentic research experiences and training across a spectrum of future scientists: elementary, undergraduate, and graduate students and at the postdoctoral level.

The overarching hypothesis of this work is that different Synechococcus ecotypes as a model group of phytoplankton, employ distinct combinations of physiological adaptations and gene regulatory strategies to thrive in their particular iron niches. Synechococcus are globally distributed allowing this project to characterize iron adaptation in populations from a range of iron niches: 'classic' low-iron, high nutrient low chlorophyll (HNLC) regions and under-studied habitats - estuarine, coastal, and non-HNLC open-ocean regions. The first goal is to conduct culture experiments on 20 Synechococcus strains from eleven ecotypes to characterize iron storage capacities and limitation thresholds as key metrics of their adaptation to different iron niches in the oceans. The second goal is to characterize gene regulation responses to varying iron availability for a) the 20 isolates in the culture experiments above and b) in situ populations using bottle experiments where they are exposed to a range of iron addition and reduction (addition of an iron chelator) conditions. The third goal is to build authentic research opportunities to increase pathways for research training and scientific literacy among elementary and undergraduate students. This involves a) developing a research-focused course where undergraduates contribute to the research in the above goals and explore topics of bias in scientific research and b) developing an inquiry-based learning module for 5th graders on the impacts of nutrients on phytoplankton in our neighborhood watershed. In addition, undergraduate and graduate students and a postdoctoral fellow will receive training and mentoring as they contribute to the research in the first two goals.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.