Scientists find clues to mysteries of ocean reef


Just beyond the colorful coral reefs and tropical waves of the island nation of Palau, a much rarer sort of reef looms out of the overwhelming darkness of the deep Pacific Ocean.

This is called the Ngaraard Pinnacle. And unlike neighboring coral reefs, the environment of the narrow shear ridge, which is surrounded by depths on all sides and peaks 300 feet below the ocean’s surface, has long been a mystery. So far, it’s thanks to a team of scientists led by Patrick Colin, who recently completed the first full look to what lives on Ngaraard Pinnacle, and “how this rare habitat – the first described in the Pacific – is able to support life”.

While coral reefs tend to monopolize attention, not all reefs are made of coral: any hard structure in the ocean, such as oysters or shale, can also interrupt the flow of surrounding water. These surfaces tend to be prime real estate for legions of sea creatures, from the Nemos and Dorys of the Great Barrier Reef to crabs and rockfish off the coast of California. Deeper reefs tend to receive nutrients and water flows from shallower upstream habitats; Ngaraard Pinnacle is unique in the Pacific Ocean because it is what Colin and his team call a “deep water island”. It is isolated from other environments, but it also exists at a depth at which most of the ocean is either bottomless or in gradual decline.

Local fishermen have known for a long time that something was going on there, but until recent years scientists had barely mapped the full contours of a lone, dimly-lit skyscraper of a reef, let alone sending cameras or collect data on the species there. Some researchers were hoping to find reef-building corals living at the edge of their comfort zones, as some do at deeper reef sites in Hawaii. Instead, they discovered “gorgonians and soft corals, a modest number of echinoderms. [seastar and urchin] abundant and diverse bony fish species and fauna.

Unlike tropical coral reefs, which are notoriously sensitive to water temperature, the creatures of Ngaraard Pinnacle can withstand water temperature changes as extreme as 20 degrees Fahrenheit in the same season, a difference similar to change from a whirlpool to a refrigerated swimming pool. They also live just on the lower edge of the mixed layer on the surface, giving animals that might migrate up or down the pinnacle a shocking blast of cooler, faster, or differently oxygenated seawater.

Not knowing what lies beneath the sea can seem almost outdated in the modern age of Google’s precise mapping and renewed space exploration. But these gulfs in our knowledge of the ocean are the rule rather than the exception. With much of the ocean floor still unexplored, even more surprising environments than Ngaraard Pinnacle will certainly be described, given the will to know what is there.

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By: Patrick L. Colin, TM Shaun Johnston, Jennifer A. MacKinnon, Celia Y. Ou, Daniel L. Rudnick, Eric J. Terrill, Steven J. Lindfield and Heidi Batchelor

Oceanography, Vol. 32, No. 4, SPECIAL FLEAT ISSUE: Flow Encountering Abrupt Topography (DECEMBER 2019), pp. 164-173

Oceanographic Society


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