Most monitoring programs are designed to examine changes in reef structure. In many cases, physical and chemical properties of the water should be measured regularly for possible correlation with any changes observed on the reef. In addition, monitoring of ecological and structural components of a reef should be supplemented with collection of information on human activities such as snorkeling, boating, fishing and diving when these activities are suspected causes of reef degradation. It is important to keep in mind that long-term monitoring may show a correlation, for example, between reef conditions and certain environmental parameters such as increased temperature, but monitoring must be supplemented by experimental research to determine cause and effect relationships. Frequency of Sampling Sampling should be done often enough to obtain documentation of changes in reef organisms of interest, but not so frequently that it is destructive or inefficient.
Monthly observations are generally best for monitoring individual coral colonies.
Quadrat and transect surveys done every 6 months provide sufficient data for assessing changes in percent cover and species diversity, and reduce the risk of damaging reef organisms during the survey process. Of course, in the event of a storm, oil spill or other disturbance, it's important to assess the effects as soon as possible, survey permanent quadrats or transects from which data were obtained before the disturbance, and continue to monitor the aftermath and recovery. A pilot study can also help determine the most effective sample size for obtaining the required information. For example, the optimal sample size can be calculated by plotting sample effort versus the number of species seen during your pilot study. If an appropriate method is selected, but the sample size is inadequate, the credibility of any conclusions drawn from the data are irreparably compromised.