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Status of the Reefs

The Hawaiian Islands extend over a vast area of the Pacific Ocean. Our initial assessment suggests that Hawaiian coral reefs are in better condition than reefs in many other regions. However, we may be dangerously close to the massive degradation that has occurred in other regions. Decline of reefs continues in Hawai‘i  due to increasing human population and human activity. Impacts affecting Hawaiian coral reefs include; overuse (over-fishing, anchor damage, diver damage, etc.), sedimentation, nutrient loading, coastal construction, urbanization, catastrophic natural events (storm wave impact, lava flows), global warming (bleaching), introduced species, and disease outbreaks.

CRAMP Reef Status 2000 - Quantitative evaluation of coral communities.

Coral Data from 28 CRAMP Sites

Coral data from 28 CRAMP sites are summarized in this figure. These data are currently undergoing detailed analysis. The data at each site from the 10 shallow (3m) and ten deep (10 m) transects are combined in this preliminary presentation. The data summarized in the figure consists of 560 transects, with each transect being analyzed using Point Count with 20 frames per transect and 50 points per frame to yield over 500,000 data points. This survey is the most thorough, accurate and reproducible quantitative assessment of coral coverage in the main Hawaiian Islands to date. These data will provide a powerful baseline, which will be used in the future to quantitatively assess environmental trends on Hawaiian coral reefs. Findings can be summarized as follows:

Overall coral coverage.

Average coverage for all CRAMP sites is approximately 23%. All transects are positioned on hard substratum. The sites were selected over a representative cross section of Hawaiian coastal environments, so this is probably a reasonable estimate for coral cover on hard substratum over the entire main Hawaiian Islands in the depth range sampled. Published literature values generally show coverage estimates higher (mean of the previously published values is approximately 35-40% cover). Previous studies often targeted high coral coverage areas rather than selecting a good cross section of reefs throughout the state. Further, Point Count yields lower coverage values than most other methods because it forces the observer to count only living tissue. An area that visually appears to be 100% live coral (no room for more colonies) can yield less than 90% cover when analyzed by the Point Count method).

Species composition

The reefs of Hawai‘i  are best described as "Porites reefs", being overwhelmingly dominated by massive and encrusting Porites lobata and branched Porites compressa. Montipora capitata (=Montipora verrucosa) and Montipora patula (=Montipora verrilli) account for a significant amount of the coverage also. Pocillopora meandrina is common in shallow turbulent environments.

Other observations:

A latitudinal gradient is not evident in these data. Differences in coral cover are controlled primarily by local variation in dominant environmental factors such as wave energy, bathymetry, watershed influences, substrate type, etc. In general, coastal sites with high wave exposure (e.g. Pupukea, Miloli‘i Bay) have the lowest cover while bays and wave-protected coastal areas (e.g south Moloka‘i) have the highest coral cover. The most significant anomaly occurs off south Moloka‘i. Coral cover along this coast is extremely high. The two sites with highest coral cover (Pālā‘au and Kamalo) are located here. A large zone of damaged reef occurs in the middle portion of the south Moloka‘i coastline as shown by the site at Kamiloloa, which has the lowest coral coverage.

 

Last Update: 05/08/2008

<needs update from Paul>

By: Lea Hollingsworth

Hawai‘i  Coral Reef Assessment & Monitoring Program

Hawai‘i  Institute of Marine Biology

P.O. Box 1346

Kāne‘ohe, HI 96744

808-236-7440 phone

808-236-7443 fax

email: jokiel@hawaii.edu