Maui reef expedition reveals new findings

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 returned last week from a successful 6-day expedition off the coast of Maui.

Aboard the university’s research vessel, the team completed five dives using deep-diving submersibles.

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 — seeks to characterize the nature of coral reef ecosystems that occur at depths of 50 to 100 meters 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, states a Bishop Museum press release. Although certain kinds of organisms, such as black coral, have been known to exist at these depths, 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,” Tony Montgomery, a DLNR aquatic biologist and one of two chief scientists on the expedition, said in the release. “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.”

Team members participated in a series of dives, 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 scorpion fish 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 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.

Dr. John Rooney, coral reef geologist at NOAA’s Pacific Island Fisheries Science Center, said a goal of the project was 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

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. She said one of the most exciting discoveries was a sample of Halimeda that was in a reproductive state.

“It’s just amazing to see vast meadows of Halimeda covering literally acres of the sea floor at these depths,” she said in the release.

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,” Bolick said in the release. “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.”

The trip was the first of several expeditions to be conducted 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.

For more information, contact Montgomery at (808) 587-0365 or Dr. Richard Pyle at (808) 848-4115. Footage of the Hawai‘i Undersea Research Lab in action during the dive is available at http://video.google.com/videoplay?docid=5585138128704810454