Recognition of ecosystem functional optima allows early detection of eutrophication in coral reef lagoons using seagrass meadows as bioindicators.

An analysis of the impact on seagrass ecosystems of the high nutrient levels recently reported for the Mexican Caribbean revealed major structural, floristic, and community transformations over 20 years, but no adverse effects; rather, photosynthesis stimulation and increases in biomass, leaf area, and species diversity. This finding contrasts with the declining global seagrass trend and the severe deterioration documented for adjacent coral reefs. Six meadow types and three community phase shifts were identified, from oligotrophic meadows to the establishment of an ecosystem optimum and the onset of moderate adverse alterations. Differences in the minimum light requirements and species plasticity for expanding the size of the photosynthetic light collector explained germane interactions among species and early community transformations in response to habitat fertilization. Understanding when ecosystem functional optima occur and community transformations beyond optimality initiate will enable early detection of habitat deterioration (here, eutrophication) and appropriate and timely conservation actions.