Factors regulating the compositions and distributions of dissolved organic matter in the estuaries of Jiaozhou Bay in North China

Abstract

Summary Water samples collected from the Jiaozhou Bay every two months between April 2016 and February 2017 were analyzed for dissolved organic carbon (DOC), particulate organic carbon (POC), total dissolved carbohydrates (TCHO), total hydrolyzed amino acids (THAA), and chromophoric dissolved organic matter (CDOM) to explore the biogeochemical processes of dissolved organic matter (DOM) in anthropogenic estuarine and coastal environments. In addition, nutrients, chlorophyll a and COD (chemical oxygen demand) in these samples were also analyzed. All parameters exhibited temporal and spatial variations: POC 0.13–22.40 mg/L (average 1.75 mg/L), DOC 0.98–32.75 mg/L (average 5.04 mg/L), COD 0.23–7.58 mg/L (average 1.67 mg/L), TCHO 0.34–14.09 µM (average 3.18 µM), THAA 0.89–8.30 µM (average 4.04 µM), and the absorption coefficient a(355) of CDOM 0.23–16.35 m − 1 (average 3.09 m−1). The temporal and spatial variations in the concentrations of TCHO, THAA, and DOC implied that the DOM in the study areas had a relatively higher biochemical activity. The canonical correspondence analysis (CCA) and maximal information coefficient (MIC) revealed that seasonal variations in temperature and the phosphate concentration were the dominant factors regulating the DOM distributions in Jiaozhou Bay, while riverine inputs and in situ reproduction mainly controlled the DOM compositions.