CRAMP Rapid Assessment. Classification of Habitats
Parallel to a freshwater index of biotic integrity (IBI), a marine index would require environmental classification to address habitat differences that influence biological populations. For example, it would be expected that there would be very different fish populations in a sand habitat as compared with a coral reef. Thus areas with similar geologic and environmental conditions should be grouped together.
Biogeographical differences within the coral reef ecosystem occur on spatial, temporal, structural and functional levels. The heterogeneity of the biological condition makes habitat classification a critical first step to the development of bioindicators. Prior coral reef classification systems were based on geomorphological features, ignoring critical biogeographic communities.
Biogeographic classification groups similar ecological (algal ridge, seagrass beds), geomorphological (reef flat, fringing reef, reef slope), chemical (nutrients, salinity), and physical (depth, wave exposure) characteristics that are not dominated by anthropogenic disturbance. Presumably, each of these groups would have followed a similar pattern of ecological responses subsequent to human perturbation. For example, many marine organisms are stratified by depth and exposure. By dividing sites into groups based on these dominant natural forcing functions, much of the natural variability associated with the physical setting can be separated from the variability associated with human influences.
Each system class would have its own specific reference conditions and biological criteria. It is also feasible to stratify classes by grouping differences in the biological community together using multivariate procedures. From a practical standpoint, the number of classes must be limited since each class must have several associated reference sites and a range of impaired sites. Attempting to classify systems at a fine resolution would be prohibitive in terms of sampling and/or severely limit the statistical power for detecting differences among sites.
Through multivariate analyses we found that wave energy and depth most strongly influenced the stratification of fish and coral populations. Therefore, our classification of habitats is based on two different wave exposures and three depths.
High wave energy environment at Pūpūkea (Three Tables) on O‘ahu’s North shore
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