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Banks and Seamounts

Gold CoralThere are approximately 30 submerged banks in the Northwestern Hawaiian Islands. Up until recently very little was known about the banks beyond that they were shield volcanoes formed at the hotspot. Some scientists believe that many of the banks act as ‘stepping stones’ for marine organisms to migrate in the region. The bank areas provide extensive habitat for bottomfish and a few are known to provide foraging habitat for endangered Hawaiian monk seals. Large precious corals, such as gold, pink and black are also found in the deep waters of the banks. Unlike shallow reef corals which are able to harness sunlight as an energy source due to photosynthesizing symbiotic dinoflagellates in their tissues, deep-water precious corals live in near-total darkness and are completely dependent upon capturing plankton from the water column with their tentacles.

The first Hawaiian coral reefs originated around the oldest islands. Many of these islands are now seamounts sunken to great depths. Other seamounts have never emerged above the ocean’s surface. Guyots are sunken volcanoes that became flat topped seamounts. Fish and precious corals may be concentrated near the tops of seamounts or guyots.

St. Rogatien, Brooks Banks, and other unnamed banks surrounding French Frigate Shoals. Little is known about these bank areas, except that Hawaiian monk seals have been observed foraging in these areas, probably for eels. The Hawai‘i Undersea Research Laboratory plans to visit these banks in several deep sea dives beginning in 2002 to build a greater understanding of the areas.

Raita Bank is just west of Gardner Pinnacles. The crest or top of Raita Bank is about 60 feet from the ocean surface. Bottom habitats of relatively shallow banks such as Raita tend to be barren when compared with more sheltered coral reef environments. Recent surveys revealed less than 1% live coral cover in the shallow portions of Raita Bank, with the bottom scoured by wave action and strong currents. Raita is one of the larger banks in the NWHI, and there is much yet to be discovered about this area.

Pioneer Bank is only 22 nautical miles from Neva Shoals, and the features combine to form a major coral reef ecosystem rich in biodiversity and with a variety of marine habitats.