Collaborative Research: IMAGiNE: Quantifying Diatom Resilience in an Acidified Ocean

This research seeks to investigate how long-term environmental changes like ocean acidification will affect diatoms, a key microscopic phytoplankton forming the basis of many marine food webs. Diatoms account for ~40 percent of the primary production in our oceans, and a shift in their composition and abundance may result in dramatic changes in coastal ecosystems. A stress test will be developed to quantify the 'resilience' of diatoms, i.e., the degree to which they can withstand environmental stress such as saturating light, ultraviolet radiation, or increased temperature. By applying this stress test to three model diatoms that inhabit different oceanic environments, Thalassiosira oceanica, Phaeodactylum tricornutum, and Thalassiosira pseudonana, this study will uncover whether ocean acidification will have similar or distinct consequences on the future fate of these important organisms. Furthermore, this study will also characterize molecular mechanisms responsible for the observed shifts in the resilience of diatoms. Mechanistic understanding of how ocean acidification might alter the resilience of diatoms will enable predictive and actionable strategies for better environmental stewardship. Additionally, this project will generate new high school curriculum on the concepts of resilience and collapse of complex systems encountered in our everyday life. The curricula will be disseminated widely through teacher training.

Diatoms have evolved phenotypic plasticity to survive in fluctuating environments, and the capability to tolerate diverse types of stress. The proposed research addresses the challenge of quantifying how diatoms manage trade-offs between maintaining phenotypic plasticity and devoting resources to mitigating stress, which is central to predicting their resilience in complex environments. The stress test framework will enable the quantification of ecological resilience of a diatom, i.e., the degree to which a diatom population can tolerate a disturbance and persist without changing physiological state. By performing the stress test on three model diatoms representing different ecological niches, and in relevant conditions of current and future oceans (i.e., temperature, CO2, NO3, Fe, and light conditions), this study will allow the prediction of when interactions among specific factors will have synergistic or antagonistic effects on the resilience of diatoms. Systems level analysis of transcriptional (RNA-seq) and physiological changes coupled to hypothesis testing using CRISPR-cas9-based genome editing will provide predictive and mechanistic understanding of changes in diatom resilience in dynamic environments. The resulting knowledge, framework, and tools will serve as predictive indicators to forecast species partitioning and shifts in ecosystem function in changing oceans. Furthermore, the stress test framework and systems approaches will be generalizable to investigate resilience and other complex traits across microbial communities of environmental importance. This award is cofunded by the Division of Integrative Organismal Systems and the Division of Molecular and Cellular Biosciences.

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.