Revista de Oceanografia e Pesquisa Marinha
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Stressors and Disturbance Regimes on Back Reef Systems: Scale and Scope from Natural and Anthropogenic Sources

Sullivan Sealey KM, Valerie P, Smith GW, Slingsby S

Back reef environments present a particular challenge in terms of characterization and management. Shallow near shore and lagoonal habitats associated with reef systems are the first areas to be impacted by land-based sources of pollutants and disturbances, defined as “stressors”. Stressors are a link in the chain of events that lead to environmental change or “phase shifts” in natural systems. Stressors as “damaging stimuli” need to be defined in terms of thresholds for both populations of organisms, and ecological communities. Stressors alter the abundance and dynamics of individual populations of organisms, and thus impact the community structure and function. Microbial communities are key to processing nutrients and pollutants from land-based sources, but poorly characterized. The effects of changes in microbial communities usually go unnoticed until visual signs of change occur in macro-organisms (death, disease or a shift in predominate species). Because microbial communities have a major influence on the transformation of nutrients as well as a protective influence, short-term stressors often can result in latent changes in larger back reef communities. The most notable changes in back reef environments from stressors include: 1) Changes in coastal species abundance and diversity (including local extirpation), 2) Changes in natural community structure, 3) Changes in coastal water quality (or the dynamic” habitat), and 4) Changes associated with exotic species invasion. Advances in technologies and research have facilitated the detection of stressors and stress responses. Recent researches in stable isotopes signatures as indicators of nutrient flux across the land-sea interface have helped identify eutrophication sources. Detection of pathogens, advances in microbial ecology (genetic probes), and disease ecology, bleaching and pollutant studies (e.g. pesticides, fungicides, pharmaceuticals) have helped identify chronic stressors to back reef systems. Historical ecology and studies of long-term environmental change remain key to understanding the nature of change and chronic degradation of complex coastal systems. Although we understand the basic ecology of tropical marine systems in a general sense, researchers need to initiate programs to look at integrated processes across the shoreline, particularly in terms of ecosystem function in back reef environments.