Updated: September 28, 2022
University of Hawaiʻi researchers say climate change-induced ocean warming has reshaped reef ecosystems as coral bleaching events, which continue to lead to mass coral die-offs globally.
A study led by University of Hawai‘i at Mānoa student researchers revealed that exposing rice coral larvae to warmer temperatures did not improve survival once the coral developed into juveniles and were exposed to heat stress.
Coral restoration efforts in Hawai‘i are vast and include selectively breeding more resilient coral, active management of vulnerable areas and outplanting coral reared in a lab.
Shayle Matsuda and Ariana Huffmyer, marine biology graduate students in the UH Mānoa School of Ocean and Earth Science and Technology, were on a mission to optimize efforts to restore corals. While at the Inclusive Science Communication Symposium, Matsuda met Gyasi Alexander, an undergraduate student at the University of Rhode Island, and invited him to participate in a summer internship at the Hawai‘i Institute of Marine Biology in SOEST.
Exposing larvae to different temperatures
The team’s approach was to start with gametes collected during mass spawning events and rear them to the larval stage, with the long term goal of planting more coral on the reef.
“Although this process can provide more genetic diversity to the reef than fragmentation practices alone, it takes considerable time, effort and capital, and the downstream survival of the corals may be impacted by ocean warming events,” said Matsuda who is now a postdoctoral fellow at the Shedd Aquarium. “With this study, we wanted to test whether exposing larvae to different temperatures would both increase larval survival and settlement, and importantly, if exposure to elevated temperatures as larvae would lead to increased thermal tolerance, that is, higher survival, at the juvenile stage.”
“However, we do not have a good understanding of the degree, time, and profile of stress required to produce positive carry over effects and, if the effects are produced, how long they last,” said Huffmyer, now a postdoctoral researcher at the University of Rhode Island.
In their experiments, the researchers, including HIMB coral ecologist Josh Hancock, found that elevating temperature to simulate future ocean warming did not improve larval survival and did not improve survival after larval settlement. Instead, their results suggest that rearing rice coral at ambient temperatures maximizes early life stage survival.
“As climate change intensifies, it is critical that we focus our restoration and conservation strategies on those that will have the greatest positive impact,” said Huffmyer in a UH press release. “Since we found that thermal conditioning did not provide positive benefits for thermal tolerance in recruits in this species, we suggest that our time and resources are best spent pursuing other avenues of thermal conditioning and further testing thermal conditioning scenarios that may produce positive impacts.”
“Prior to this experience, I hadn’t really known what it felt like to think like a scientist,” said Alexander. “The idea of research was definitely intimidating. Ariana and Shayle helped me immensely by encouraging me to share the observations and questions that I had, even when I was afraid to use my voice. That comfortability helped me to realize that thinking like a scientist, feeling like a scientist is really just pursuing the curiosity you feel behind what you see and take in, especially when you don’t have all the answers right away.”
After completing his summer internship at HIMB, Alexander has a clearer direction for his own graduate school pursuits.
“My current goal is to develop a skillset in big data,” said Alexander. “I reflected on my work on HIMB and realized how much more effective I could have been if I had a more robust set of data analysis skills. So among my next moves, I plan to learn a few programming languages like R and Python to aid my work in the future and make myself available to even more opportunities.”