Biogeochemical buffers in coastal lagoons: from chemical reactions to ecosystem functions and properties

Anthropogenic disturbances and natural factors often cause unpredictable non-linear responses in coastal lagoons. Important changes include the shift from seagrass to ephemeral seaweed communities, especially in sheltered habitats. Here, biogeochemical reactions are related to primary production and decomposition processes and depend upon bioturbation by benthic fauna. Scaling up, the network of these components and reactions can be regarded as an ecosystem property which accounts for oxygen availability and for potential buffering functions - e.g. phosphate retention within the sediment, immobilisation of sulphides into the insoluble iron mono-sulphide and release of molecular nitrogen to the atmosphere