• Home
  • »
  • Reef Survey

Reef Survey

Image

We are documenting baseline levels of coral disease on Oahu using two 25 m belt transects with visual counts at each site. A team of two divers swim along the transects, with one diver identifying and enumerating coral colonies within a 25m x 2m (100 m2 reef area) belt transect, while the other diver records incidence of disease within a wider 25m x 6m transect (250m2 reef area). Corals are identified to the species level and assigned to one of seven size classes (0-5cm, 6-10cm, 11-20cm, 21-40cm, 41-80cm, 81-160cm and > 160cm). These size classes and protocols were adapted from Mundy (1996) who used them successfully for broad-scale surveys in American Samoa and have also been used successfully to examine coral community structure in the NWHI (Maragos et al., in press). This methodology yields quantitative estimates of coral size distributions, recruitment, density, diversity and prevalence and incidence of disease. Diseased corals are photographed and a general description of the condition is recorded. Samples of diseased coral (and healthy portions for controls) are collected for laboratory investigations using microbiological, molecular and histopathological techniques.

Coral cover is estimated using an Olympus 5050 digital camera and underwater housing mounted on a support frame 1.3 m above the bottom, providing a image size 1 m X 0.66 m that is enclosed by the frame’s base. The frame is centered over the transect line and a digital photograph taken every meter, providing a continuous belt transect 25 m X 0.66 m showing the bottom composition and coral coverage under the line, for a total of 16.5 m2 at each site surveyed. Species composition and percent coverage by species and for total coral are determined for each digital image using PhotoGrid software with 50 randomly assigned points within the quadrat. These values are averaged for the 25 quadrats for a mean value per transect and for the two transects for each survey site.

Survey sites

Coral coverage, coral visual counts, coral photographs and sampling of coral lesions have been completed at nine sites in Kaneohe Bay, two sites off Pupukea, one site off Haleiwa Trench and Lanai Lookout and three sites near Kahe Point. Also, coral, coverage transects and lesion photographs were completed at three sites in Hanauma Bay but no samples were taken in the Marine Life Conservation District.


Navigation :