During winter months, a few days after the full moon, thousands of fish make their way to the warm tropical waters off the west coast of Little Cayman, Cayman Island. Nassau Grouper are typically territorial and don’t interact often, but once per year, they gather in the same spot where they all spawn to carry on the tradition of releasing gametes, in the hopes that some of them will develop to adulthood and carry on the population.
Our guest this week is Janelle Layton, a Masters (and soon to be PhD) student in Dr. Scott Heppel’s lab in the Department of Fisheries, Wildlife, and Conservation Sciences. Janelle’s research focuses on this grouper, which is listed as near threatened under the Endangered Species Act. Overfishing has been the largest threat to Nassau Grouper populations, but another threat looms: warming waters due to climate change. This threat is what Janelle is interested in studying – how does the warming water temperature affect the growth and development of grouper larvae?
Each winter Janelle travels to this aggregation site in the Cayman Islands, where these large groups of grouper (grouper groups?) aggregate for a few days to reproduce. During this time, she collects thousands of fertilized Nassau Grouper eggs to take back to the lab and study. These eggs will develop in varying water temperatures for 6 days, where each day a subset of samples are preserved for future analysis.
So far, Janelle is finding that the larvae raised in higher temperatures tend to demonstrate not only an increase in mortality, but an increase in variability in mortality. What does this mean? Basically, eggs from some females are able to survive and develop under these stressful conditions better than eggs from other females – so is there a genetic component to being able to survive these temperature increases?
The answer may lie in proteins
Aside from development and mortality, Janelle is investigating this theory by measuring the expression of heat shock proteins in the fertilized eggs and larvae. Heat shock proteins are expressed in response to environmental stressors such as increased temperatures, and can be measured through RNA sequencing. The expression of these proteins might hold the key to understanding why some grouper are more likely to survive than others. Janelle’s work is a collaborative effort between Oregon State University, Scripps Institute of Oceanography, Reef Environmental Education Foundation and the Cayman Islands Department of Environment.
To learn more about Nassau Grouper, heat shock proteins, and what it’s like being a Black woman in marine science, tune into Janelle’s episode this upcoming Sunday, March 12th at 7 PM! Be sure to listen live on KBVR 88.7FM, or download the podcast if you missed it. You can also catch Janelle on TikTok or at her website.