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Monitoring the Coral Reef Off Moloka'i, Hawai'i
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Setting up:
Securing the underwater camera package to the seabed in April 2001.
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In late July and early August, scientists from the USGS and several universities converged on the south
shore of the island of Moloka'i in the Hawai'ian Islands. They came to continue a project aimed at identifying
changes in coral reef health due both to human and natural causes, including sediment processes. This
multi-agency effort is spearheaded by Mike Field (Santa Cruz) and Bob Halley (St. Petersburg), and includes
researchers from Woods Hole, Menlo Park, BRD-Corpus Christi, the University of California, University of
Washington, University of Hawai'i, and University of Colorado.
A large number of offshore instruments has been deployed for continual monitoring of oceanographic
conditions that may affect the reef. The instruments include wave gauges, ReefProbes (instrumented tripods
that measure currents, conductivity, temperature, and turbidity), tube and rotating sediment traps, and an
underwater camera system--all self-logging. Approximately every 100 days, researchers retrieve the
instruments to download data ashore and refurbish the instruments before re-installing them on the reef.
Prepped and ready:
Camera package before deployment. The Canon high-resolution digital still camera, strobe light,
and battery pack are in separate underwater housings mounted within an adjustable
stainless-steel frame.
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This past spring, a new underwater-camera system was established on the reef to monitor the flux of
sediment on and over coral. The camera system, designed by Hank Chezar (Menlo Park), consists of
a Canon high-resolution digital still camera, strobe light, and battery pack, all in separate underwater
housings mounted within an adjustable stainless-steel frame. The camera is positioned over a small
coral colony with a gridded concrete block placed next to the colony for scale. The camera collects a
digital image every four hours, day and night. The objective is to record the period and frequency of
sediment stress and to correlate these data with data on swell, wind and wind waves, and tides. The
results will help scientists identify the principal agents of sediment re-suspension and movements on
corals of the shallow forereef (~10 m deep). This first three-month deployment successfully captured
more than 650 time-series images without a missed frame.
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click on any of the three images below to view a larger version |
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The camera at work: Examples of images
from the underwater digital camera. The lines on the gridded concrete block are 2 cm apart and are used
for scale. (A) Coral and clean concrete block after initial deployment (April 27, 2001). (B) Movement of
sediment during a re-suspension event (May 19, 2001). (C) Progressive settling of sediment on both the
coral and the concrete block (June 5, 2001).
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Also participating in the field studies were researchers from BRD-Corpus Christi (Scott Carr and Marion
Nipper), who sampled interstitial pore water from reef sediment to analyze for environmental toxicity.
Several areas of the reef are severely degraded, and pollution, along with sedimentation stress, is being
studied as a possible cause.
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September 2001
in this issue:
cover story:
Moloka'i Coral Reef Monitoring
North Carolina Cruises
California Offshore Oil Seeps
Training FWS in Geologic Processes of Coastal Ecosystems
MRIB to Host Digital Library of Gulf of Maine
Coastal Summit
Coastal Issues at GSA
Dust Transport
Gulf of Mexico Integrated Science
Geographical Honor Society—Larry Handley
Quenton Smith-Costello: SEPAC
NWRC Seminars
September Publications List
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U. S. Department of the Interior | U.S. Geological Survey
