Anomalies in the carbonate system of Red Sea coastal habitats

Abstract

Abstract. 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.

Greenhouse gas emissions (CO2 and CH4) and inorganic carbon behavior in an urban highly polluted tropical coastal lagoon (SE, Brazil)

“…4). Comparing the covariations of ΔTA and ΔDIC along the salinity gradient, the data points followed mainly the vectors representing the processes of sulphur oxidation, iron oxidation and nitrification that are involved only in the consumption of TA, without net effect on DIC (Abril and Frankignoulle 2001;Baldry et al 2019;Rassmann et al, 2020). In the lagoons, the mixing of anoxic-acid freshwaters with well-oxygenated waters is associated with processes of re-oxidation of reduced by-products of organic matter degradation, generating titration of TA to dissolved CO2 particularly evident in the middle salinity regions.…”

A Unique Diel Pattern in Carbonate Chemistry in the Seagrass Meadows of Dongsha Island: The Enhancement of Metabolic Carbonate Dissolution in a Semienclosed Lagoon

“…Due to the variance changes across seasons and sites, a Wilcox's robust ANOVA (WR-ANOVA) was chosen to account for heteroscedasticity among habitat groups. Tests between medians were chosen rather than between means, as seagrass habitats displayed skewed carbonate chemistry observations (Baldry et al, 2020). Differences in the medians of pH 25 , pH in situ , pCO 2in situ , TpCO 2 , DIC, normalized DIC (NDIC), TA, and normalized TA (NTA) between the IL and NS sites in each season were assessed using a WR-ANOVA that was implemented by the function "med1way" of the R package "WRS2" (Mair and Wilcox, 2020).…”

“…Carbonate chemistry dynamics in the water column of seagrass meadows is well known to be driven by a variety of metabolic activities, including plant photosynthesis/respiration (Gattuso et al, 1998;Semesi et al, 2009), carbonate formation/dissolution (Barrón et al, 2006;Burdige et al, 2008;Howard et al, 2018;Saderne et al, 2019b), benthic metabolism (Berg et al, 2019), and hydrodynamic processes (Ruesink et al, 2015;Baldry et al, 2020). As a result, the carbonate system in the overlying water column of seagrass meadows generally shows large variabilities at diel and tidal time scales as well as seasonal variations (Frankignoulle and Distèche, 1984;Waldbusser and Salisbury, 2014;Cyronak et al, 2018;Saderne et al, 2019a).…”

The Diel and Seasonal Heterogeneity of Carbonate Chemistry and Dissolved Oxygen in Three Types of Macroalgal Habitats

“…The relationship between A T and C T has been used as a tool to quantify the relative contributions of ecosystem metabolism to seawater chemistry changes occurring in various aquatic habitats (Dutta et al, 2019;Baldry et al, 2020;Saderne et al, 2020). The variation in stoichiometry between these two carbonate parameters represents relative intensities of biological activities including photosynthesis (and respiration), calcification (and dissolution), nitrification (and denitrification), sulfate reduction, and fermentation (Saderne et al, 2020).…”