First, by comparison with other sites. Nonetheless, parameters such as the abundance of macro-algae, the abundance of living corals, and the fish community composition, may indicate human disturbance. Sometimes there are no pristine sites left, and comparison must be with historical data or supposed general standards. Of course, reef communities are dynamic, and they are going to change anyway. We know that there are seasonal changes, specific displacements and intermittent disturbances.
Replication is important.
10 independent m2 quadrats are more statistically useful than one of 10 m2. But the fact of global change, and the prospect of more, has increased the importance of the monitoring program, and brought more funding for it. There are 14 protocols, of which only 4 take place on coral reefs. Next, we shall introduce fish counts. Temperature, salinity and secchi depth are collected manually, once a week.