Multi-Institutional Collaboration Completes First Expedition to Document Deep Coral Reefs off Maui: Three-year NOAA-funded Project Gets Off to a Successful Start
A team of researchers from the Bishop Museum, Department of Land and Natural Resources, University of Hawai‘i, and NOAA’s Pacific Island Fisheries Science Center has returned from a successful six-day expedition aboard the University’s research vessel, Ka‘imikai-o-Kanaloa, which included a total of five dives using the deep diving submersibles Pisces IV and Pisces V, operated by the University’s Hawaii Undersea Research Laboratory (HURL).
The multi-institutional project, funded by two separate NOAA grants ($1.4-million from NOAA’s Coral Reef Ecosystem Studies, and $150,000 from NOAA’s Coral Reef Conservation Program administered through HURL), seeks to characterize the nature of coral reef ecosystems that occur at depths of 50–100 meters (165–330 feet) off Maui. These deep reefs were not known to exist until relatively recently, in large part because they occur at depths below what can safely be accessed using conventional SCUBA gear. Although certain kinds of organisms, such as black coral, have been known from these depths for decades, the new discoveries are of vast expanses of densely-packed hermatypic (reef-building) corals, which have photosynthesizing algae called zooxanthellae in their tissues.
“These are among the deepest known coral reefs of this kind in the world,” says Tony Montgomery, Aquatic Biologist at the Department of Land and Natural Resources’ Division of Aquatic Resources, and one of the two Chief Scientists on the expedition. “The corals themselves have long been known to occur at these depths, but not at such high densities, and covering such large areas. It’s really extraordinary.”
In addition to Montgomery, the research team included ichthyologist Dr. Richard Pyle (the other Chief Scientist on the project), fish ecologist Dr. Ken Longenecker, and marine invertebrate specialist Holly Bolick (all of the Department of Natural Sciences, Bishop Museum); coral-reef geologist Dr. John Rooney and fisheries biologist Raymond Boland (NOAA Pacific Island Fisheries Science Center); algae specialist Heather Spalding (Department of Botany, University of Hawai‘i); stable isotope chemist Dr. Brian Popp (Department of Geology and Geophysics, University of Hawai‘i); coral researcher Daniel Wagner (Department of Oceanography, University of Hawai‘i) and disease specialist Dr. Thierry Work (U.S. Geological Survey).
Team members participated in a series of dives inside HURL’s two deep-sea submersibles, Pisces IV and Pisces V, spending upwards of eight hours at a time on the sea floor collecting specimens and making photographic and video images of the deep reefs. Included among the collected specimens is a scorpionfish that appears to represent a species new to science. The team also conducted a series of visual transects along these reefs using a Remotely Operated Vehicle (ROV) equipped with a video camera, deployed a device to monitor changing water temperature over time, and began an experiment to study the growth rate of corals on these deep reefs.
“One of our goals on this project is to understand the environmental conditions that favor the development of these deep reefs – parameters such as bathymetry, water temperatures, current patterns, light levels, and substrate types may all play a role.” says Dr. John Rooney, coral-reef geologist at NOAA’s Pacific Island Fisheries Science Center. “How fast do these deep-reef corals grow? Can we model their occurrence and distribution? These are some of the very basic questions we hope to answer.”
Heather Spalding, of the Department of Botany at the University of Hawai‘i, is the State’s leading expert on Halimeda algae in Hawaiian waters. “It’s just amazing to see vast meadows of Halimeda covering literally acres of the sea floor at these depths”, she says. Spalding is a veteran of submersible diving in this region, and has spent years studying the distribution and biology of Halimeda and other kinds of algae on deep Hawaiian reefs. “One of our most exciting discoveries on this expedition was a sample of Halimeda that was in a reproductive state.”
Holly Bolick, Collections Manager of the Marine Invertebrates at Bishop Museum, processed many of the samples brought up from the depths, looking for sponges, crustaceans, mollusks, and other invertebrates living on the rocks. “Invertebrates represent far and away the greatest diversity on coral reefs,” she said. “Many of them are tiny, or live in holes and on the undersides of rocks. Though they’re not as obvious as the fishes and corals, they are an extremely important part of coral-reef ecosystems.”
“These reefs play an important role in the overall ecology of Hawaiian reefs, and may also have important implications for fisheries management,” says Dr. Ken Longenecker of the Bishop Museum. “We want to compare growth rates and other ecological aspects of the fishes that live on these deep reefs, with the same species living on shallow reefs. We want to know whether the deep reefs serve as a refuge for some of the commercially harvested species.”
Dr. Richard Pyle, Associate Zoologist at Bishop Museum, has nearly twenty years’ experience exploring deep coral reefs throughout the Pacific, mostly using high-tech diving gear. “It was fantastic being able to spend all that time on the bottom,” says Pyle, who participated on his first dive in a research submersible on this expedition. “Usually when we do our exploratory dives, we’re limited to an hour or so on the bottom. With the submersibles, we can take our time collecting samples, placing instruments, and conducting experiments.”
This was only the first of several expeditions to be conducted by this project on the deep reefs southwest of Maui, in the Au‘au Channel. By the end of the three-year project, the research team hopes to have a better understanding of the biodiversity and environmental and ecological characteristics of this biologically rich but poorly known habitat. This knowledge will be of vital importance for successful and effective management of Hawaii’s marine resources.
For more information about this project, contact Tony Montgomery at (808) 587-0365 or Dr. Richard Pyle at (808) 848-4115.
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Photos coutesy of Hawai‘i Undersea Research Laboratory.