Distributions and Influencing Factors of Carbonate Species in Bohai Bay and Relevant Rivers Flowing into the Bay in Summer 2020

Abstract

The distributions of pH, total alkalinity (Alk), dissolved inorganic carbon (DIC) and the partial pressure of carbon dioxide (pCO2) were investigated in Bohai Bay in northeastern China during summer 2020. The CO2 air–sea fluxes were also estimated for that summer. The results of the survey showed that the distributions of Alk and DIC in surface and bottom seawater were generally consistent, with the maximum values of DIC and Alk appearing at the same station, station BHB33 at the surface and station BHB35 at the bottom, which were in the middle of the bay. The minimum values of pH and the maximums value of pCO2 were both located at station HH2 at the surface and station HH3 at the bottom, which were near the mouth of the Haihe River. Bohai Bay was estimated as a source of CO2 in summer 2020. Carbonate species presented significant correlations with biochemical parameters, such as chlorophyll α (Chl-α), dissolved oxygen (DO) and nutrients. In addition, terrestrial inputs and human activities, together with the poor hydrodynamics of Bohai Bay are also the main factors influencing the carbonate species in Bohai Bay.