Ecological interactions between Tropical Coastal Ecosystems: Mangrove, Seagrass, Coral

Birkeland, Charles; Eldredge, Lucius; Grossenbaugh, Deborah

A review of existing information for the South Pacific Regional Environment Program. Coastal marine ecosystems are particularly important to Pacific islanders because most of the animal protein of islands has traditionally come from the coastal resources and because human settlements have tended to be in coastal regions for logistic reasons. An understanding of the functioning of coastal marine ecosystems is important both because the resources need more careful management as the human populations grow and because human activities will have the greatest effects on coastal environment where populations are concentrated. Fishes and invertebrates forage out from coral reef onto seagrass beds and return for shelter. In the Caribbean, field studies have indicated a flow of nutrients from the seagrass beds to coral reefs such that a greater biomass of fishes is found on reefs near seagrass beds and coral colonies grow faster near the aggregation sites on reefs for fishes that forage in seagrass beds than do coral colonies away from fish aggregation sites. Seagrass beds and mangrove swamps serve as nursery areas for several species of reef fishes. While nutrients move from seagrass beds to coral reefs, the effects of species interactions on community structure are in the other direction. Coral reef herbivores influence the structure of plant communities in the seagrass beds near reefs. Pacific reefs may differ from Caribbean reefs in this regard. Echinoids are far less common in Micronesia than in the Caribbean.