Influence of natural and anthropogenic factors on spatial-temporal hydrochemistry and the susceptibility to nutrient enrichment in a subtropical estuary.

This study uses multivariate statistics to analyze hydrochemical spatial-temporal variations in the Maowei Sea of Beibu Gulf, South China Sea and evaluates its susceptibility to nutrient enrichment by a risk model. The seasonal variations of sea surface temperature (T), salinity (S), pH, dissolved oxygen (DO), chemical oxygen demand, transparency, total suspended particulate (TSP), petroleum hydrocarbons (PHCs), NO2-, and SiO32- were mainly driven by the meteorological factors (precipitation and air temperature), while NO3-, NH4+, and PO43- content were more likely related to the point-source factors. The spatial and seasonal variations of T, DO, TSP, PHCs, and SiO32- might also be affected by sea-source factors such as thermal water discharge from adjacent parts of the Beibu Gulf. The sea's susceptibility to nutrient enrichment was moderate, and is mainly affected by precipitation, temperature, and high irradiation. The results present the complexity of natural and anthropogenic influences on a small subtropic estuary.