A research trip by University of Hawaiʻi at Mānoa scientists to Wake Island and Johnston Atoll—two remote spots in the Pacific—will provide new and comprehensive insights into the historic and potential future role of these two places as biological stepping-stones for movement of marine species between the Hawaiian Islands and other archipelagoes of the North Pacific Ocean.
Wake and Johnston are isolated coral atolls 2,300 miles and 800 miles southwest of Honolulu, respectively. Both share many species in common with Hawaiʻi, and the apparent biogeographic connection has important implications for understanding how often species disperse via Johnston and Wake to and from Hawaiʻi, versus dispersing directly to Hawaiʻi from more distant archipelagoes, such as the Marianas, Line and Marshall Islands.
In July 2024, the UH Mānoa team collected thousands of tissue samples from several species of sea urchins, seawater samples, and water and plankton samples from the surface layers of the ocean as they transited between Guam, Wake, Johnston, and back to Hawaiʻi. DNA will be extracted from all of the samples to understand connections at gene, whole genome, species, and community levels of organization. The work to analyze each specimen will take months.
“The research will tell us about the biological connections between Hawaiʻi and other parts of the Pacific and also make predictions about what the future holds, including the potential dispersal of species that may have either a positive or negative impact on Hawaiian coral reef ecosystems,” said Peter Marko, professor in the School of Life Sciences and co-leader of the research team.
Access to the coral reef communities at Wake and Johnston has been limited by a long history of military activity at each atoll. Comprehensive species lists have not been completed, especially with respect to organisms that are not easily detected visually. Genetic analysis has been limited to a handful of species, but what data are available have generated intriguing ideas that can be tested with data from many more species.
Groundbreaking research
Scientists are studying sea urchins because their babies (larvae) float in the ocean, making them easy to observe in labs. This helps researchers understand how long these baby sea urchins can survive while drifting in the complicated currents of the North Pacific Ocean. Working with NOAA scientists, who are using computers to map how ocean currents move these larvae, the research team can predict where the baby sea urchins might end up. They can then test these predictions by looking at the DNA of sea urchins from different areas to see if they’re related.
“Models, genetic analysis, and larval biology all provide pieces of the puzzle, but only by combining all three can we understand how far marine larvae can travel in the ocean, and how often larvae from other parts of the Pacific arrive in Hawaiʻi,” said research co-leader and School of Life Sciences Professor Amy Moran.
Environmental DNA (or eDNA) will be extracted from seawater samples taken from around each atoll and be used similarly to study the genetic similarities of populations of species found in Hawaiʻi, Wake and Johnston. eDNA analysis is limited to a small number of genes from each species, but has the advantage of providing the population genetic signatures of an unprecedented number of species.
“eDNA can provide a new perspective on community population genetics by increasing the number of species in analyses from dozens to hundreds of species, including hard to find or identify species that are often overlooked,” said Taylor Ely, a School of Life Sciences PhD candidate who is leading the eDNA work.
Expedition challenges, opportunities
The expedition was funded by the National Science Foundation and conducted from the UNOLS (University-National Oceanographic Laboratory System) research vessel Thomas G Thompson. The research team boarded the R/V Thompson in Guam and then spent 18 days at sea, stopping for three days each at Wake and Johnston. The trip was a collaboration between faculty, staff, and students from the UH Mānoa School of Life Sciences, UH Diving Safety Program, NOAA, UH Marine Center, and University of Washington Marine Operations, the latter which operates the Thompson.
Scuba diving in remote locations presented numerous logistic hurdles and safety considerations for the team. Small craft and operators provided by both the UH Marine Center and the R/V Thompson supported four, two-diver missions per day.
“Once the boats are in the water and away from the ship, you still have to navigate through reefs and avoid surf to get divers to their sampling sites,” said Mills Dunlap, small boat manager and operator from the UH Marine Center. “This cruise was fortunate to not only have an incredible platform to get us there, but also a great crew and a gungho group of scientists.”
UH Diving Safety Officer David Pence added, “The support for this mission from UNOLS and personnel from the R/V Thompson and the UH Marine Center was exceptional. In recent years, very few UNOLS vessels have had experience with research diving support, so to accomplish this project was an exciting opportunity.”
“The trip was three years in the making,” Marko said. “We’re especially grateful to College of Natural Sciences Dean Philip Williams and the staff of the College of Natural Sciences, the School of Life Sciences, and the Research Corporation of the University of Hawaiʻi for making it possible to bring several UH students and recent graduates along with us to help on the project. These are invaluable opportunities for them.”
