Productivity and Biogeochemical Cycling in Seagrass Ecosystems

Seagrasses grow in reduced sediments, where they benefit from higher nutrient concentrations compared with the water column but may suffer from anoxia and sulfide toxicity. Seagrasses promote sedimentation of organic matter, and seagrass ecosystems are important contributors to sequestration of atmospheric CO2 as Blue Carbon. Inputs of organic matter stimulate microbial processes in the sediments, and sulfate reduction is an important mineralization pathway in seagrass meadows. Seagrasses are adapted to grow in reduced and sulfidic sediments where oxygen release from belowground tissues oxidizes the rhizosphere and prevents sulfide from intruding into the plants. Seagrass ecosystems are under intense pressure from human activities in the coastal zone. These activities often lead to increased sediment and water column hypoxia and anoxia and sulfide toxicity and contribute to the observed decline in seagrass ecosystem health and areal extent. To better manage, conserve, and reverse, seagrass degradation will require further understanding of the biogeochemical processes in seagrass sediments.