The overarching goal of this project is to investigate the molecular response of the Antarctic thecosome pteropod, Limacina helicina antarctica to ocean acidification (OA) and ocean warming (OW).
Specifically, we propose to investigate changes in the epigenome of juvenile L. h. antarctica, by assessing the dynamics of DNA methylation in response to three scenarios of environmental conditions that were simulated in laboratory mesocosm experiments: (1) seasonally relevant pCO2 conditions for present-day summer and winter, (2) future ocean acidification, and (3) a multiple stressor experiment, that investigated the potential synergistic interaction of OA and high temperature stress. This investigation is an important step in exploring mechanisms that can alter the transcriptome and influence phenotypic plasticity in an Antarctic marine invertebrate that is vulnerable to anthropogenic climate change.
The proposed investigation of the pteropod epigenome is based upon the analysis of samples that were collected in past field seasons in association with NSF award PLR-1246202. This interrogation of the epigenome regarding DNA methylation status is based upon observations we made when studying differential gene expression in L. h. antarctica. Specifically, our data showed significant changes in the dynamics of DNA methylation, along with differential gene expression in pteropods in response to conditions in our mesocosm experiments. These observations are: (1) genes involved in epigenetic response were observed to change in response to seasonal variation in pH, (2) global patterns of DNA methylation changed in L. h. antarctica in response to OA conditions, (3) genes that displayed differential expression were enriched with signatures of gene body methylation, and (4) overall, it was clear that juvenile L. h. antarctica are capable of mounting a substantial epigenetic response to ocean acidification. These findings are the basis for the aims in this proposal, and further, they strongly support the potential role of DNA methylation in regulating transcriptomic responses by L. h. antarctica to future ocean acidification and during in situ development in the Southern Ocean.
Based upon these observations of the pteropod transcriptome and epigenome, we propose the following objectives in the current proposal, noting again that this project will use samples reserved from previous fieldwork at McMurdo Station: (1) to assess the dynamics of DNA methylation in L. h. antarctica, (2) to integrate changes in methylation status with changes in gene expression in juvenile L. h. antarctica that were exposed to various stressors in our mesocosm experiments, (3) to analyze DNA methylation and gene expression in pteropods exposed to conditions of ocean acidification and multiple stressors, and (4) to measure DNA methylation dynamics and gene expression in L. h. antarctica in response to acute heat stress during a thermotolerance trial.
Scientifically, this project will contribute important information on the tolerance and resistance of Antarctic pteropods to future ocean conditions. The data will also provide insight into the response of Antarctic pteropods to the synergistic effects of ocean acidification and ocean warming. Lastly, the study addresses the environmental epigenetics of L. h. antarctica and will provide a deeper understanding of the genomic biology and the epigenetic plasticity of the an important member of the zooplankton community in the Southern Ocean. Overall, knowledge of L. h. antarctica’s adaptive capacity to withstand environmental change will help forecast how pteropod populations might respond to environmental change, a research goal that is consistent with strategic research goals within USAP (NAS report 2015).
From a perspective of inclusion and diversity, this project will provide significant opportunities for three female Ph.D. graduate students from groups that are under-represented in STEM. The project will leverage the existing samples to provide training in bioinformatics and experience in molecular biology to these Ph.D. graduate students at key times in their degree program, along with an appreciation for Antarctic research. In addition, we plan to integrate the global change biology story about Antarctic pteropods into a program designed to bring under-represented undergraduates into environmental science at UC Santa Barbara (UCSB), a Hispanic-Serving Institution. Efforts in this project will be integrated into a new program at UCSB, FUERTE, an NSF-funded program designed to increase the inclusion of Latinx undergraduates in environmental science via early engagement, fieldwork, and research experiences. This proposal does not require fieldwork in the Antarctic.