Coastal sediments regulate the water-column oxygen budget due to their high rates of carbon mineralization and may contribute significantly to seasonal hypoxia. Using field observations of dissolved oxygen in the water column and sediments and the sediment oxygen consumption rates (SOC), we explore the effects of SOC on hypoxia formation at the Pearl River Estuary and its adjacent coastal seas. We show that sediment remineralization contributes to more than 50% of organic carbon produced in the euphotic zone, leading to disproportionally shallow oxygen penetration. Our results indicate that the vertical stratification of the water column, particularly the thickness of the bottom boundary layer (BBL), determines the effect of SOC on hypoxia formation. We further develop some relationships between SOC and the water column oxygen distributions and test the model using data from similar settings, including the Changjiang Estuary, the northern Gulf of Mexico, and the Louisiana Continental Shelf. We will discuss the possibility of using commonly measured physicochemical properties in the water column to parameterize SOC, which is expensive to quantify in coastal areas but crucial in modeling regional biogeochemical cycling and hypoxia formation.

Primary Presenter: Jing Sun, the Hong Kong University of Science and Technology (jsunbk@connect.ust.hk)

Authors:

Jing Sun, The Hong Kong University of Science and Technology  (jsunbk@connect.ust.hk)

Jiying Li, The Hong Kong University of Science and Technology  (jiyingli@ust.hk)