Kimberlee Baldry, Vincent Saderne, Daniel C. McCorkle, James H. Churchill, Susana Agustí, and Carlos M. Duarte
Biogeosciences, (2020)
We use observations of dissolved inorganic carbon (DIC)
and total alkalinity (TA) to assess the impact of ecosystem metabolic
processes on coastal waters of the eastern Red Sea. A simple,
single-end-member mixing model is used to account for the influence of
mixing with offshore waters and evaporation–precipitation and to model
ecosystem-driven perturbations on the carbonate system chemistry of
coral
reefs, seagrass meadows and mangrove forests. We find that
(1) along-shelf
changes in TA and DIC exhibit strong linear relationships that are
consistent with basin-scale net calcium carbonate precipitation;
(2) ecosystem-driven changes in TA and DIC are larger than offshore
variations
in >70 % of sampled seagrass meadows and mangrove forests,
changes which are influenced by a combination of longer water residence
times and community metabolic rates; and (3) the sampled mangrove forests
show strong and consistent contributions from both organic respiration and
other sedimentary processes (carbonate dissolution and secondary redox
processes), while seagrass meadows display more variability in the relative
contributions of photosynthesis and other sedimentary processes (carbonate
precipitation and oxidative processes). The results of this study highlight
the importance of resolving the influences of water residence times, mixing
and upstream habitats on mediating the carbonate system and coastal air–sea
carbon dioxide fluxes over coastal habitats in the Red Sea.