CARBON AND CARBONATE METABOLISM IN COASTAL AQUATIC ECOSYSTEMS

TLDR

The coastal zone, where land, ocean, and atmosphere interact, is a highly diverse and biogeochemically active interface that receives large terrestrial organic matter and nutrient inputs, exchanges substantial matter and energy with the open ocean, and is a major contributor to global carbon cycling. This review examines primary production, respiration, calcification, carbon burial, and exchanges with adjacent systems, including the atmosphere, across major coastal ecosystems such as estuaries, macrophyte communities, mangroves, coral reefs, and the continental shelf. The authors synthesize existing metabolic data on primary production, respiration, calcification, carbon burial, and exchanges for each major coastal ecosystem. Except for estuaries, all examined coastal ecosystems are net autotrophic.

Abstract

▪ Abstract The coastal zone is where land, ocean, and atmosphere interact. It exhibits a wide diversity of geomorphological types and ecosystems, each one displaying great variability in terms of physical and biogeochemical forcings. Despite its relatively modest surface area, the coastal zone plays a considerable role in the biogeochemical cycles because it receives massive inputs of terrestrial organic matter and nutrients, is among the most geochemically and biologically active areas of the biosphere, and exchanges large amounts of matter and energy with the open ocean. Coastal ecosystems have therefore attracted much attention recently and are the focus of several current national and international research programs (e.g. LOICZ, ELOISE). The primary production, respiration, calcification, carbon burial and exchange with adjacent systems, including the atmosphere, are reviewed for the major coastal ecosystems (estuaries, macrophyte communities, mangroves, coral reefs, and the remaining continental shelf). All ecosystems examined, except estuaries, are net autotrophic. The contribution of the coastal zone to the global carbon cycle both during pristine times and at present is difficult to assess due to the limited metabolic data available as well as because of major uncertainties concerning the magnitude of processes such as respiration, exchanges at the open ocean boundary, and air-sea fluxes of biogases.