CRAMP experimental design allows detection of changes that can be attributed to various factors such as:
overuse (over-fishing, anchor damage, aquarium trade collection, etc.), sedimentation, nutrient loading, catastrophic natural events (storm wave impact, lava flows), coastal construction, urbanization, global warming (bleaching), introduced species, algal invasions, and fish and invertebrate diseases.
The emphasis of the program is on the major problems facing Hawaiian coral reefs as listed by managers and reef scientists during workshops and meetings held in Hawaii (1997-1998). These are:
over-fishing, sedimentation, eutrophication, and algal outbreaks.
CRAMP experimental design gives priority to areas where baseline data relevant to these issues were previously collected. Transect dimensions, number of replicates, and methods of evaluation have been selected to detect changes with statistical confidence. Standard techniques include the establishment of permanent transects to quantify fish, coral, algae, and invertebrates at study sites.
CRAMP researchers are quantifying changes that have occurred on coral reefs subjected to varying degrees of fishing pressure, sedimentation, eutrophication, and algal growth and are conducting experimental work in order to test hypotheses concerning the role of these environmental factors in the ecology of coral reefs. We are also in the process of resurveying, updating and integrating existing ecological information on an array of coral reefs that have been designated as areas of concern or, "hot spots," by managers and scientists.
The second step involved soliciting input from colleagues conducting coral reef monitoring programs in the Florida Keys and the Great Barrier Reef. Their general recommendation was to use digital video to sample coral cover over large areas of the reef. Before we could implement their designs, however, we had to evaluate the appropriateness of these techniques for Hawai`i. The following parameters in the sampling design were determined in the third step:
1.Repeatability and appropriate length of the transects using different methods 2.Observer variation within different methods 3.Number of points per frame to analyze 4.Number of frames per transect to analyze 5.Number of transects per depth to sample 6.Random versus fixed transects 7.Time and monetary considerations to optimize sampling design
The results of this evaluation were presented at the National Coral Reef Institute Conference in Florida and are summarized by the CRAMP research team (Brown, et al. 1999). Repeatability and appropriate transect length were tested using photoquadrats on a transect line sampled over a short time interval. Shorter transects of 10m were found to have higher precision (Ability to replicate quadrats on a transect) than transects of 25m and 50m. Photoquadrats produced similar results to visual estimation techniques, regardless of observer, but neither method yielded satisfactory precision.
Digital video was evaluated at Hanauma Bay, Oahu over 2 time intervals separated by 84 days. It was assumed that overall coral cover would not change dramatically during this time period. Power curves were constructed using methods described by Zar (1999) for detecting a 10% change in coral cover across 2 time periods (Figure 1). Number of frames was more important in increasing power than number of points though the difference was not substantial. This is primarily due to the fact that more frames sample a larger portion of the habitat, which incorporates more of the heterogeneity of the substrate. A sample size of 10 transects per site appeared to be adequate for characterizing the coral cover using a power value of 0.8 set as a convention by Cohen (1988).
Fixed transects were chosen over random for several reasons. First, it is difficult to properly implement a randomized protocol for transect placement without a map of benthic habitats that is geo-referenced. At present this does not exist for the state of Hawai`i. Second, the majority of the historical data uses fixed transect locations so integrating the current protocol with previous work will be simpler. Third, after the initial random setup the fixed transects should be easier to resample, thus reducing preparation time and ultimately costs to generate the random grid for subsequent transect measurements (Green and Smith, 1997). Fourth, randomized sampling of transects will have difficulty in detecting change in coral cover if reefs change dramatically over time. This is because the random protocol measures inherent spatial variation at each sampling period, which adds variance associated with spatial heterogeneity of the reef rather than changes or patterns that are time-related (Green and Smith, 1997). Fifth, using a repeated measures ANOVA design with fixed transects can provide additional information on population and community structure that is difficult to obtain with random transects (Hughes, 1996; Connell et al. 1997). Sixth, the time and cost complications with random transects are not worth the broader inference about reef "condition" especially if the fixed transects are representative of habitat variation (Andy Taylor, personal communication). Finally, interpreting results from fixed transects is much easier for the general public and resource managers to comprehend than using a randomized sampling design.
Time and monetary constraints were examined to determine the optimum sampling protocol. The analysis revealed that digital video collected more data per unit time than visual estimation, planar point intercept and photoquadrats. It was the most expensive option considered at $5,500 for the system but since field time underwater is the principal limiting factor then the quantity of field data collected outweighs the expense. In addition, digital video and photoquadrats also enable archiving of the data for later re-analysis to address additional questions.
Site Survey Protocol
Two types of protocol are utilized by CRAMP: Monitoring Protocol and Assessment Protocol. This submission to NOAA only includes data taken using the Monitoring Protocol. The Assessment Protocol is simply an abbreviated version of the Monitoring Protocol. The Assessment Protocol is a rapid method that is most useful for describing spatial relationships. The Assessment Protocol lacks the statistical power of the Monitoring Protocol to detect change in the benthos. The Assessment Protocol is a more cost-effective method for answering certain questions on the status of coral reefs.
Monitoring Protocol - General Description
Installing the fixed monitoring sites is a process that was generally completed by a team of six divers during a single dive. All primary sites have been installed. The initial monitoring of a given site was generally initiated at some time after installation. More detail on installation is discussed under the section on Benthic Monitoring. Upon reaching an established monitoring site site a number of tasks must be performed. CRAMP generally surveys one site (3 m and 10 m transect locations at each site) per day with a team of 6 divers. The deeper site is surveyed in the morning, the shallow site in the afternoon after a proper surface interval. The beginning of the transect is located by visual lineups and/or GPS by skin divers and marked with a dive flag to alert boaters of our presence and enable quick location by the divers. Subsequent SCUBA teams entering the water take materials needed for the survey (spooled transect tapes, rugosity chain, video camera, photo-quadrat apparatus, extra marker pins, etc) and deposit the material near the start of the transect for use by the teams during the dive.
The first SCUBA team to enter the water consists of two divers: the person doing the fish survey and a back-up diver who stays within visual range and photographs the fixed photo-quadrats as the fish survey proceeds. Estimates of fish species richness, abundance, and biomass are taken before the benthic transect lines are laid out so as to sample a relatively undisturbed habitat. The standard CRAMP fish transect is taken along a depth contour within the CRAMP grid of benthic transects, and consists of four, 5x25m transects that are separated by 5m. The scientist doing the fish survey counts fish while deploying a 25 m line behind him/her. As the survey proceeds, two more SCUBA divers enter the water. One of the pair starts video taping the replicate benthic transects while the second deploys the transect tapes and records species information on the corals/algae located along each transect for later reference. The third team of two divers follows the video transect team and measures rugosity under the replicate transects. Upon completion of the fish transect, the first dive team completes the photo-quadrats. As other teams complete their work they return to the start of the transect and begin taking up the transect tapes.
During the survey, various divers complete additional functions. These include taking sediment samples, stabilizing or replacing lose transect pins, routine photography of organisms, description of habitats, making algae collections or various activities.
The same procedure is carried out at the shallow site during the afternoon. In addition, at various times of the day (depending on time availability) two members of the group will skin dive with a dive flag and water proof GPS unit while describing and recording habitat distribution throughout the study site for later mapping efforts.
This database contains all of the fish transect data collected at each site during a survey. Data includes site, survey date, observer, transect, abundance and size estimates for all fish species present within the transect boundaries. Multiple queries extract species richness and abundance data for each site. Additional queries convert the size estimates to total biomass and biomass by species for each site. Length estimates of fishes from visual censuses can be converted to weight using the following length-weight conversion:
W = aSLb
the parameters a and b are constants for the allometric growth equation where SL is standard length in mm and W in grams. Length-weight parameters are available for 150 species commonly observed on visual fish transects in Hawaii (Friedlander, 1997) and are included in the Taxon table of the database.
Sources Used: Brown, E, E Cox, B Tissot, K Rodgers, and W Smith (1999). Evaluation of benthic sampling methods considered for the Coral Reef Assessment and Monitoring Program (CRAMP) in Hawaii. International Conference on Scientific Aspects of Coral Reef Assessment, Monitoring, and Restoration. April 14-16, Ft. Lauderdale, FL.
Connell, J H, T P Hughes, C C Wallace (1997). A 30-year study of coral abundance, recruitment, and disturbance at several scales in space and time. Ecol. Mono. 67(4): 461-488.
Friedlander, Alan and Parrish, James 1998. Habitat characteristics affecting fish assemblages on a Hawaiian coral reef. Journal of Experimental Marine Biology and Ecology 224: 1-30.
Green, R H and S R Smith (1997). Sample program design and environmental impact assessment on coral reef. Proc 8th International Coral Reef Symposium. 2: 1459-1464.
McCormick, Mark 1994. Comparison of field methods for measuring surface topography and their associations with a tropical reef fish assemblage. Marine Ecology Progress Series 112: 87-96.