Creatures lurking under the sea

Researchers from HPU and UH-Manoa find unique marine life in waters off the Hawaiian Islands

Deep, underwater canyons off the Hawaiian Islands support abundant and unique marine life habitats just like the canyons off continents, according to a recent study by researchers from Hawaii Pacific University and the University of Hawaii at Manoa.

Some of the creatures, astonishingly odd in appearance, seem to have stepped off the pages of a Dr. Seuss storybook.

The researchers base their conclusions on observations from 36 dives off Oahu, Molokai, Nihoa and Maro Reef in the Northwestern Hawaiian Islands.

They were aboard the UH Pisces IV and Pisces V submersibles that descended between 1,100 and 4,900 feet off Oahu, Molokai and Maro. A submerged video camera was used in the survey off Nihoa.

The authors of the study, published in the March issue of the journal Marine Ecology, are Eric Vetter, professor of marine biology at HPU, and Craig Smith, a UH-Manoa professor of oceanography.

"Craig Smith and I wondered if the same dramatic contrast in (ocean floor) food resources between canyon and noncanyon settings seen in continental margins would also occur in tropical oceanic islands," said Vetter, who had previously studied canyon systems off California.

He and Smith had expected to see sparser marine habitats because tropical islands and atolls transport less nutrient-rich sediment from land into the ocean to feed deep-sea organisms. They also believed the steepness of the ocean floor and the islands' curved coastlines would limit how far the sediment could travel to the canyons.

"Perhaps the biggest surprise of this study was the large number of species -- 41 -- that we found only in canyon habitats," Smith said in an announcement of the discovery. "This suggests that canyons support a substantial specialized fauna that would not (otherwise) exist in the Hawaiian archipelago."

UH-Manoa doctoral candidate Fabio De Leo, who also took part in the research, said the canyons are ideal candidates for protection from commercial fishing because they can provide a critical habitat for bottom fish and shellfish.

Human activities like dumping dredged material could also harm the canyon life, Smith added.

Oahu and Molokai were picked as examples of mountainous islands that have a lot of organic matter slipping downslope. Nihoa and Maro were selected to represent low-lying islands.

Future studies will attempt to determine whether nutrients feeding the habitats come from ocean microorganisms or sediment that originated on land.

Source: http://www.starbulletin.com/news/20100412_creatures_lurking_under_the_sea.html

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