The assessment 'toolbox': Community-based reef evaluation methods coupled with geochemical techniques to identify sources of stress

There have been few seminal advances in techniques of health evaluation of coral reefs since line transects and visual fish counting were first proposed in 1972, yet the rate of resource destruction increases rapidly. Especially in Third World settings, coastal communities need access to simple techniques that have been shown to identify stress on reefs: (1) Coral mortality indices, (2) Benthic bioindicators (stomatopods, forams, amphipods), (3) Coral associate counts, and (4) Bioerosion amounts in coral rubble. Coral growth rates are an undependable measure of reef health: corals on dying reefs with low coral cover often exhibit higher than normal growth rates. Transect data may be cast into other forms, such as triangular diagrams, to be more effective in reef management. All of these rapid assessment techniques have been shown to be effective in the hands of persons with limited technical training. Each is rapid and cost-effective. Once one of the 'tools' in the assessment 'toolbox' has detected stress, the precise nature of the source can be identified via geochemical techniques: (1) Sewage: stable isotope ratios of nitrogen (δ¹⁵N) in a number of organisms (stomatopods, corals) are enriched at sites subject to sewage discharge. (2) Siltation: in areas subject to siliciclastic input, insoluble residues in coral skeletons are a measure of exogenous sediment input. (3) Thermal/Light stress: as has been shown in studies of El Niño events and the Indonesian 'haze' of 1997, the δ¹³C signal in coral skeletons is a measure of metabolic stress caused by changes in light and temperature.