Coasts Dominated by Organisms

Abstract

Organisms, either plants or animals, at the interface of land and sea, form among the most productive and biologically complex ecosystems on Earth. Coral reefs, mangrove forests or sea grass meadows are important not only from an ecological point of view, but provide tens of millions of people in the tropics and subtropics with food, timber, fuel or medicine. The most prominent organisms that form vast 3-dimensional coastal structures are reefbuilding corals. They occur between approx. 30°N and S in all oceans, where the water is clear and over 18°C in the coldest month. Coral reefs occupy less than one tenth of one percent of the world ocean surface, about half the area of France, yet they provide a home for twenty-five percent of all marine species. Sea grass and mangrove forests are land builders par excellence by trapping sediments. Intact, they serve as natural breakwaters and dissipate the energy of waves along the coast. Despite their strategic importance, these ecosystems are under threat worldwide: They are destructed for salt pans, aquaculture enterprises, infrastructure and housing developments and suffer from indirect stresses such as climate warming, chemical pollution, sediment overload and disruption of a water and salinity balance, just to name a few. Moreover, many marine organisms also provide important insight in past environments, sea levels or tidal ranges, which might hold the answer to preserving ecosystems in a rapidly changing climate.