Hi, Madeline Piscetta! Great to have you on ReefBites.
Madeline is a recent Masters of Science in Marine Biology and Ecology graduate from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science program. She studied the interactive effects of heat stress and elevated nutrient concentrations on physiology of scleractinian coral larvae at Hawaii Institute of Marine Biology. Learn more about Madeline’s research below!
Give an elevator pitch of what your research/project is about.
In Kāne’ohe Bay, temperature anomalies and nutrient influxes from terrestrial runoff interact on reefs, impacting adult coral colonies and their larvae. My research examined how temperature and nutrients (nitrate and phosphate) impact the larval physiology of the brooding species Pocillopora acuta during their early stages of development. The study had an orthogonal design with two temperature treatments (ambient and high) and four nutrient treatments (control/ambient, 5-uM nitrate, 1-uM phosphate, 5-uM nitrate + 1-uM phosphate) for a total of eight treatments. I found that elevated nitrate concentrations negatively impacted larval survivorship, but the presence of elevated phosphate when nitrate concentrations are also elevated ameliorates the negative impact of nitrate by restoring the N:P ratio and allowing larvae to maintain their nutrient exchange mechanisms with their symbionts. Nutrient analyses confirmed that larvae in the nitrate + phosphate treatments took up more phosphate than larvae in treatments without elevated nitrate. Additionally, neither temperature nor nutrients affected symbiont densities, suggesting that P. acuta larvae are able to maintain their functional symbiosis in stress conditions. Elevated temperature, nitrate, and phosphate all increased settlement rates, which has implications for recruitment and connectivity between reefs in the bay. Elevated temperatures also decreased dark-adapted respiration rates but did not impact survivorship. Despite these effects, overall survivorship remained high, with no treatment experiencing lower than 91% survivorship by the fifth day. P. acuta larvae are hardier than other broadcast spawning species, like Montipora capitata and Lobactis scutaria, which experienced much higher mortality rates in the same treatments.
Why is this research/project important and timely?
Climate change is increasing seawater temperatures on a global scale, resulting in more frequent and severe bleaching events. Other stressors, such as nutrient pollution from runoff, interact with global stressors on a local to regional scale. My research demonstrates that P. acuta larvae are impacted by water quality and temperature, but are not nearly as negatively impacted as other species in the bay. This may mean that reefs in Kāne’ohe Bay will see community shifts in the future and has implications for source-sink dynamics within the bay.
What is the broader impact and implication of your findings?
Corals are exposed to multiple stressors at any given time– no stressor acts in isolation. By examining the interactions of elevated temperatures and elevated nitrate and phosphate concentrations on coral larvae, we can understand how stress conditions will impact spawning and recruitment on local scales. Understanding the impacts of water quality on larvae can inform management practices, such as managing water releases from terrestrial sources during spawning season. Additionally, larvae may experience different impacts than adult corals. For example, P. acuta larvae are hardy due to their lipid reserves, while adult colonies are more sensitive to changes in light and temperature. My research provides a better understanding of the impacts of stressors on the early life history stages of P. acuta and demonstrates their potential to successful recruit when exposed to temperature anomalies and nutrient loading.
How did you come to work in this field/project?
During the summer of 2016, I interned at the World Wildlife Fund’s US headquarters in Washing, D.D., where I helped plan their annual Fuller Science for Nature Symposium. Dr. Ruth Gates spoke at the event. While researching her work, everything clicked. I realized I wanted to pursue coral acclimatization and stress hardening in graduate school. It sounds cliché, but if you have ever heard Ruth talk, then you know how inspiring her words are for young scientists.
My bachelor’s degree is in geology, so I was able to connect my understanding of carbonate chemistry and sedimentation to coral reefs. At the University of Miami RSMAS, I was in Dr. Andrew Baker’s Coral Futures Lab. It was my goal to do my thesis research with the Gates Lab, and I am honored to have worked with them while Ruth was still with us.
What is your top graduate school life hack or survival resource?
Always have coffee readily available. And make time to decompress, because you will need it in order to stay productive.
Any additional information or comments you would like to share?
Never be afraid to go for it. Be persistent in asking for opportunities and believe in your potential. Even if you aren’t sure if you are qualified, apply for that internship, apply for that grant. You’ll never know unless you try, and you’ll learn in the process!