Nutrient distribution and structure affect the acidification of eutrophic ocean margins: A case study in southwestern coast of the Laizhou Bay, China

• The inshore waters of the southwest Laizhou Bay show a sign of acidification.
• Inputting of DIN and DSi could enhance acidification in the SWLZB.
• The respiration process of OM may not be the major reason of acidification in the SWLZB.

The effects of nutrient distribution and structure on the acidity of coastal waters were analyzed based on the data of 48 surface water samples collected in the southwestern coast of the Laizhou Bay and its adjacent rivers (SWLZB) which are heavily influenced by nutrient-laden discharges. The concentration and structure of nutrients varied considerably along the coast owing to different contributors. The studied inshore waters exhibited a sign of acidification. The pH was significantly negatively correlated with the concentration of NO3-N, NO2-N, NH4-N and DSi, but showed no obvious correlation with the concentration of PO4-P and the ratio of TDN/TDP, DSi/DIN and DSi/PO4-P, respectively. The results indicated that the distribution of nutrients might well be an important environmental factor affecting the acidification of the SWLZB in warmer months.