Every summer, a large area (15,000 km 2 on average) over the Texas–Louisiana shelf in northern Gulf of Mexico turns hypoxic due to decay organic matter that is primarily derived from nutrient inputs Mississippi/Atchafalaya River System. Interannual variability size zone large. The 2008 Action Plan put forth by Mississippi River/Gulf Watershed Nutrient Task Force, an alliance multiple state and federal agencies tribes, calls for reduction through management watershed. Comprehensive models...

Dongjiang River Network (DJRN), a complex urbanized river network in the Pearl Basin, China. Low-oxygen conditions have been expanding systems, whereas clear and quantitative understanding on deoxygenation processes is still lacking. This study utilized well-validated physical-biogeochemical model to investigate oxygen dynamics combined with ecosystem metabolisms over an annual cycle explicitly quantify contribution of major oxygen-depleting substances from different sources low-oxygen...

Abstract. The continental shelf of the northern Gulf Mexico receives high dissolved inorganic nitrogen and phosphorus loads from Mississippi Atchafalaya rivers. nutrient load results in primary production river plumes contributes to development hypoxia on Louisiana summer. While phytoplankton growth is considered be typically nitrogen-limited marine waters, limitation has been observed this region during periods peak discharge spring early Here we investigate presence, spatio-temporal...

Abstract. A three-dimensional (3-D) physical–biogeochemical coupled model was applied to explore the mechanisms controlling dissolved oxygen (DO) dynamics and bottom hypoxia during summer in Pearl River estuary (PRE). By using numerical tracers, we proposed a new method (namely physical modulation method) quantify contributions of boundary conditions each source sink process occurring local adjacent waters DO conditions. mass balance analysis based on indicated that at layer were mainly...

Abstract. Increase in riverine nutrient loads was generally recognized as the primary cause of coastal deoxygenation, whereas role other factors, especially suspended sediments, has received less attention. This study aims to discern impacts anthropogenic alterations various inputs on subsurface deoxygenation over past three decades a large river-dominated estuary, Pearl River Estuary (PRE). By utilizing physical-biogeochemical model, we reproduced observed dissolved oxygen (DO) conditions...

Abstract. The Pearl River estuary (PRE) frequently experiences low-oxygen conditions in summer, with large-extent events and a long-term deoxygenation trend being reported recently. In this study, we provide synthesis of the spatiotemporal patterns incidence different levels PRE based on situ observations collected from 1976 to 2017 aim elucidate underlying mechanisms their changes over past 4 decades. show that dissolved oxygen (DO) content has had significant temporal variability spatial...

Abstract. In summer, the Pearl River estuary (PRE) experiences hypoxia, largely driven by high input of fresh water with low dissolved oxygen (DO), abundant nutrients and particulate organic carbon from network. this study, we used a well-validated physical–biogeochemical model together DO species-tracing method to study responses hypoxia dynamics anthropogenic perturbations riverine inputs (i.e. DO, nutrients, carbon) in July–August 2006. Model results showed that PRE was most sensitive...

Abstract A carbon cycle model is built to describe the behavior of materials in Pearl River Estuary (PRE), China. The distributions and transformations dissolved inorganic (DIC), organic (DOC), particulate (POC) are simulated water column sediment for year 2006. terrestrial input dominant factor that determines seasonal variation carbon, while physical biochemical processes contribute spatial‐temporal circulation carbon. simulation results reveal PRE acts as a net source atmospheric CO 2...

A validated hydrodynamic-biogeochemical model was applied to investigate the effects of physical forcing (i.e., river discharge, winds, and tides) on summertime dissolved oxygen (DO) dynamics hypoxia (DO < 3 mg L−1) in Pearl River estuary (PRE), based a suite sensitivity experiments. Compared with base run 2006 (a wet year), simulated hypoxic area moderate year (with 75% discharge run) dry scenario 50% reduced by ~30% ~60%, respectively. This is because under lower levels, less...

Abstract Our understanding of eutrophication‐induced acidification in estuaries and coastal oceans is complicated by the seasonally spatially changing interactions between physical biochemical drivers. By combining conservative mixing method a physical‐biogeochemical model, we present seasonal spatial dynamical analysis Pearl River Estuary northern South China Sea. In summer, widespread regulated two distinct drivers, which are strengthened stratification hypoxia zone high turbidity...

Abstract. The Pearl River estuary (PRE) frequently experiences low-oxygen conditions in summer, with large extents of events and a long-term deoxygenation trend being reported recently. In this study, we provide synthesis the spatiotemporal patterns incidence different levels PRE based on in-situ observations collected from 1976 to 2017, aim elucidate underlying mechanisms their changes over past 4 decades. show that oxygen content had significant temporal variability spatial heterogeneity....