Seasonal and Spatial Controls on the Eutrophication‐Induced Acidification in the Pearl River Estuary

Abstract

AbstractOur understanding of eutrophication‐induced acidification in estuaries and coastal oceans is complicated by the seasonally and spatially changing interactions between physical and biochemical drivers. By combining the conservative mixing method and a physical‐biogeochemical model, we present the seasonal and spatial dynamical analysis of eutrophication‐induced acidification in the Pearl River Estuary in the northern South China Sea. In summer, the widespread eutrophication‐induced acidification is regulated by two distinct physical drivers, which are the strengthened stratification in the hypoxia zone and the high turbidity in the Lingdingyang Bay. In the hypoxia zone, eutrophication‐induced acidification is controlled by the combined effect of benthic remineralization and stratification, while it is dominantly regulated by local biochemical processes (nitrification and respiration) of the whole water column in other regions of the estuary. In winter with the enhanced vertical mixing, the eutrophication‐induced acidification is still active in the Lingdingyang Bay, and its strength has largely decreased compared with summer condition. While for the hypoxia zone, the eutrophication‐induced acidification peaks in summer and disappears in winter.