Project: OCE-RIG: Developing Molecular Bioassays for Evaluating Iron Status of Environmentally Relevant Diatoms

This project focuses on an important group of photosynthetic algae, the diatoms, and how iron availability modulates their growth. Diatoms are important organisms at the base of the marine food web. Iron is required for the structure and function of proteins essential to diatom growth. Iron concentrations can be low in many areas of the ocean and exists in different forms classified by size and chemical characteristics. Recent efforts have increased understanding of the distribution of these different iron forms, but which forms individual phytoplankton can access remains unclear. The investigator will conduct experiments with important diatom species to develop and use assays that can assess whether iron provided in different forms or from different sources can be accessed by those species to alleviate iron stress. These data will help us understand the relationship between iron and an important group of organisms at the base of the food web, which will prove valuable to climate and food web modelers. This project will further the NSF goals of training new generations of scientists and making scientific discoveries available to the general public. The project supports the research of an early-career scientist, the training of undergraduate and high school students, including inner city middle and high school girls.

The project combines trace metal biogeochemistry, phytoplankton cultivation, and molecular biology to address questions about the bioavailability of various iron forms to environmentally relevant diatoms. Iron is an essential micronutrient for marine phytoplankton. While knowledge of the distribution of iron has increased significantly as a result of the ongoing GEOTRACES program, a mechanistic and quantitative understanding of the bioavailability of various forms of iron remains illusive. Previously, the investigator developed a calibrated molecular bioassay capable of indicating when a specific oceanic diatom was experiencing iron stress. It has been used to evaluate iron stress in oceanic field samples and in incubation samples in response to additions of different iron fractions. The goal of this proposal is to develop additional calibrated molecular assays for iron stress in other environmentally relevant diatoms from both coastal and oceanic habitats and use them to asses the biological availability of iron from varying sources. The experimental plan includes culture experiments monitoring growth, photosynthetic physiology, and gene expression of iron stress response genes. The molecular assays will then be used to test whether iron from a variety of sources can alleviate iron stress in the different species. Results from this project will provide tools to answer fundamental questions about the bioavailability of various forms of iron to important phytoplankton. As such, this research will provide valuable information for biogeochemical modelers, increasing their ability to use the data generated from the GEOTRACES program to accurately predict future changes in ocean productivity.