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USGS To Track Coral Larvae Off Maui
Released: 6/26/2003

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
Mike Field 1-click interview
Phone: 808-667-7188

Curt Storlazzi
Phone: 831-212-1253

Note to Editors: Reproducible photos are available at:

An unprecedented experiment to track the travel route of microscopic coral larvae will be conducted off the coast of Maui from June 29 to July 5 by the U.S. Geological Survey (USGS), the University of Hawai‘i, the Hawaiian Division of Aquatic Resources, the Maui Ocean Center, and the University of Washington. These groups are trying to learn how waves, currents, and sea-water properties affect the dispersal of coral larvae to better understand why certain reefs off West Maui are doing well and why others are doing poorly.

The next coral-spawning event will begin shortly after the next new moon, which is June 29, and the scientists will be there with high-tech instruments to track the coral larvae’s nighttime journey, said Dr. Curt Storlazzi, USGS’s chief oceanographer for the project.

Corals are small colonial animals that secrete hard outer skeletons. One of the principal corals for building reefs in Hawai‘i, "rice coral" (Montipora capitata), releases packets of eggs and sperm at about 9 p.m. each evening for four nights starting one day after each new moon during a period of about 4 months—this year, from May through August. After the next new moon, on June 29, the next spawning event will begin. The packets rise to the ocean’s surface and float along—by the millions—in surface currents until the fertilized eggs, or larvae, sink and start to grow on rocky areas. The problem is, said Storlazzi, no one knows exactly where the currents take the larvae.

As researcher Eric Brown of the University of Hawai‘i explains, "Some coastal areas may not be developing coral reefs simply because the larvae are unable to settle."

Where the larvae go is exactly what the USGS scientists and their collaborators aim to determine. The researchers will use underwater tripods—much like lunar landers—to monitor temperature, water clarity, waves, and currents. At the same time, satellite-tracked drifters will be released at night to float along with the larvae, and the researchers will monitor the drifters’ positions all night on radio frequencies.

Storlazzi noted that the currents off West Maui are extremely complex, and understanding the fate of the larvae requires scientists to monitor currents for days to detect shifts due to changes in tides and wind. Storlazzi will round out the experiment by measuring water speeds along the coast from a boat using an acoustic doppler current profiler.

The USGS Coral Reef Team, led by Dr. Michael Field, has been studying the effects that current movements and sediment particles have on the condition of Hawaiian coral reefs for the past several years to provide resource managers with information on how to best protect these Hawaiian treasures. According to Field, "Our goal has been to identify the pathways of sediment to the reef, and how it is moved onto corals by waves and currents." After several years of research on the islands of Maui and Moloka‘i, the USGS team is applying their expertise to the tracking of microscopic larvae.

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