Permanent quadrat survey


Permanent quadrat survey aims to investigate the temporal changes in corals and other sessile animals within a fixed square (quadrat) on the bottom by either illustrating or photographing. The size of our quadrat is 4 m2 (2m x 2m). Permanent quadrat survey provides information on the attribute of coral communities in a fine-scale and it complements the photo-transect survey. For example, we are able to know from quadrat data whether a coral community having the cover of 20% is comprised of several large colonies or many small colonies.

Permanent quadrat results
Download "quad" (kmz format, 351 b)
Permanent quadrat

Permanent quadrat sites and photographs can be viewed on Google Earth
Download Google Earth

Permanent quadrat sites and photographs can be viewed also on Google Map

Permanent quadrat procedure


A quadrat is permanently marked with a steel reinforcing rod at each of four corners. Field work requires 3 or 4 scuba divers. A 2m x 2m PVC frame having 400 square grids (each grid is 10cm x 10cm) is placed on the quadrat in accordance with marking reinforcing rods. The quadrat is photographed with a digital camera by each of 50cm x 50cm divisions. The photos overlap about 60% between neighboring divisions. Then a diver records the position and species name of all coral colonies that occur within the quadrat. All photographs are corrected to remove distortion using a PC and image processing software and are merged to create a mosaic image of the quadrat. A detailed coral map of the quadrat is drawn based on the mosaic image and the position/species records made in the field. Projected area and percentage cover of each coral colony are determined by analyzing the coral map.

Permanent quadrat results

Quadrat C2


Quadrat E


Quadrat F


Quadrat G


Quadrat I


Quadrat J


Quadrat K