Fixed photo-quadrats are used in order to examine trends of individual organisms with regards to growth, recruitment and mortality. Five haphazardly selected photo-quadrats at each depth contour have been established with 4 pins at each corner to ensure accurate repositioning of the frame.
Eric Brown of the UH Department of Zoology using the photo-quadrat apparatus. Photo by Paul Jokiel.
The frame is constructed of PVC plastic tubing and designed to hold a 35 mm Nikonos V camera system with and two SB105 strobes (master/slave) in a rigid array. The frame is designed to photograph 0.25 square meters of the substrate at a height of 0.50 m from the bottom. Images of sessile organisms are traced and digitized for two dimensional estimates of aerial coverage. Sampling is scheduled once a year at each site along with the digital video surveys.
Example results: change in photo-quadrat (Hanalei, 3m) over a 1 year time interval. (Click for a larger view)
Data Analysis Protocol
Flow chart showing analysis procedures. (Click for a larger view)
One roll of 35 mm film is used to capture 5 photo-quadrats at each depth with 2 exposures per photo-quadrat. Nikon Scan is used to convert the 35 mm images to digital format. Images are written to a CD-ROM for archiving and later analysis. SigmaScan or Scion Image programs are used to digitize dimensions of objects within the photo-quadrat by tracing lines around coral and different substrate types. Aerial coverage is computed for each object and compared with prior photos of the same site. Scion Image writes a text file that is readily available for a variety of programs. The resulting text file is imported into MS-Excel for proofreading. After proofreading, the data file is imported into MS-Access for storage into the CRAMP database. Output from Access is imported into Statistica for statistical analysis using an ANOVA repeated measures design with 2D aerial coverage of the substrate types as the dependent variable.
|Photoquadrats -- Digital Camera Transects -- Rugosity Measurements -- Sediment Analysis|
Last Update: 04/21/2008
By: Lea Hollingsworth
Hawai‘i Coral Reef Assessment & Monitoring Program
Hawai‘i Institute of Marine Biology
P.O. Box 1346
Kāne‘ohe, HI 96744