The carbonate system on the coral patches and rocky intertidal habitats of the northern Persian Gulf: Implications for ocean acidification studies

Abstract

This research characterizes the temporal and spatial variability of the seawater carbonate chemistry on the near-shore waters of the northern Persian Gulf and Makran Sea. In general, normalized total alkalinity (nAT) showed a westward decrease along the coasts of Makran Sea and the Persian Gulf. Intertidal seawater was always supersaturated in terms of calcium carbonate minerals during the daytime. Rocky shore waters in the Persian Gulf were sinks for CO2 in the winter during the daytime. The nAT decreased from Larak to Khargu Island by 81 μmol/kg. As expected, the two hypothetical drivers of bio-calcification, i.e., Ω and the [HCO3−]/[H+] ratio, were significantly related at a narrow range of ambient temperature. However, as data were pooled over seasons and study sites, in contrast to ΩAr, the [HCO3−]/[H+] ratio showed a slight dependence on temperature, suggesting that the ratio should be investigated as a more reliable factor in future biocalcification researches.