What drives interannual variability of hypoxia in Chesapeake Bay: Climate forcing versus nutrient loading?

Li, Ming; Lee, Younjoo; Testa, Jeremy M.; Li, Yun; Ni, Wenfei; Kemp, W. Michael; Toro, Dominic M. Di

doi:10.1002/2015gl067334

Cited by 99 publications

(96 citation statements)

References 44 publications

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“…ROMS‐RCA‐CC has been validated against a wide range of observational data in Chesapeake Bay at multiple time and space scales (Li et al, ; Li et al, ; Shen et al, ; Testa et al, ; Zhong & Li, ). We compared 30‐year (1986–2015) simulation results with field observations in the upper, middle, and lower bay for further validation.…”

Section: Resultsmentioning

confidence: 99%

Ecosystem Metabolism and Carbon Balance in Chesapeake Bay: A 30‐Year Analysis Using a Coupled Hydrodynamic‐Biogeochemical Model

Shen

Testa

et al. 2019

JGR Oceans

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The carbon cycle in estuarine environments is difficult to quantify because of substantial spatiotemporal heterogeneity in the sources, exchanges, and fates of carbon. We overcame these challenges with a multidecade numerical modeling analysis of seasonal, interannual, and decadal variability in net ecosystem metabolism (NEM) and associated carbon fluxes in Chesapeake Bay. Interannual variability in NEM along the estuarine axis indicated a clear spatial dependency of NEM on riverine discharge, with elevated flows causing increasing upper bay heterotrophy and increasing lower bay autotrophy during wet years. Our 30‐year simulation suggested the Chesapeake Bay is somewhat unique among estuaries in its tendency toward net autotrophy as a consequence of its extremely high nutrient to organic matter input ratio and large size. Budgets of three different carbon pools revealed that the entire Chesapeake Bay is a CO2 source to the atmosphere and organic carbon source to the open shelf, providing quantitative export estimates for interpretation of anthropogenic perturbations to the regional carbon flux.

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Section: Resultsmentioning

confidence: 99%

Ecosystem Metabolism and Carbon Balance in Chesapeake Bay: A 30‐Year Analysis Using a Coupled Hydrodynamic‐Biogeochemical Model

Shen

Testa

et al. 2019

JGR Oceans

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“…Therefore, one certain aspect about the impact of climate change on estuarine hypoxia is the increasing stratification and decreasing vertical supply of O 2 to the bottom water. The import of high‐O 2 coastal water by estuarine return flow is also a significant source of O 2 to the hypoxic region (Li et al, , ). According to our analysis, F hadv decreases in the future climate, primarily due to the seaward expansion of hypoxia and O 2 reduction in the lower Bay.…”

Section: Discussionmentioning

confidence: 99%

Large Projected Decline in Dissolved Oxygen in a Eutrophic Estuary Due to Climate Change

Ross

et al. 2019

JGR Oceans

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Climate change is known to cause deoxygenation in the open ocean, but its effects on eutrophic and seasonally hypoxic estuaries and coastal oceans are less clear. Using Chesapeake Bay as a study site, we conducted climate downscaling projections for dissolved oxygen and found that the hypoxic and anoxic volumes would increase by 10-30% between the late 20th and mid-21st century. A budget analysis of dissolved oxygen in the bottom water revealed differing physical and biogeochemical responses to climate change. Sea level rise and larger winter-spring runoff led to stronger stratification and large reductions in the vertical oxygen supply to the bottom water. On the other hand, warming led to earlier initiation of hypoxia, accompanied by weaker summer respiration and more rapid termination of hypoxia. Decreasing solubility due to warming accounted for about 50% of the reduction in the bottom-water oxygen content.

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“…Thus, RCA includes a two‐layer sediment biogeochemical model that represents the near‐surface aerobic and underlying anaerobic environments and simulates the cycling of carbon, O 2 , nitrogen, phosphorus, silica, and sulfur. A detailed description and validation of the ROMS‐RCA coupled model is provided in Testa et al () and M. Li et al ().…”

Section: Methodsmentioning

confidence: 99%

Controls on Carbonate System Dynamics in a Coastal Plain Estuary: A Modeling Study

Shen

Testa

et al. 2019

JGR Biogeosciences

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The study of acidification in Chesapeake Bay is challenged by the complex spatial and temporal patterns of estuarine carbonate chemistry driven by highly variable freshwater and nutrient inputs. A new module was developed within an existing coupled hydrodynamic‐biogeochemical model to understand the underlying processes controlling variations in the carbonate system. We present a validation of the model against a diversity of field observations, which demonstrated the model's ability to reproduce large‐scale carbonate chemistry dynamics of Chesapeake Bay. Analysis of model results revealed that hypoxia and acidification were observed to cooccur in midbay bottom waters and seasonal cycles in these metrics were regulated by aerobic respiration and vertical mixing. Calcium carbonate dissolution was an important buffering mechanism for pH changes in late summer, leading to stable or slightly higher pH values in this season despite persistent hypoxic conditions. Model results indicate a strong spatial gradient in air‐sea CO2 fluxes, where the heterotrophic upper bay was a strong CO2 source to atmosphere, the mid bay was a net sink with much higher rates of net photosynthesis, and the lower bay was in a balanced condition. Scenario analysis revealed that reductions in riverine nutrient loading will decrease the acid water volume (pH < 7.5) as a consequence of reduced organic matter generation and subsequent respiration, while bay‐wide dissolved inorganic carbon (DIC) increased and pH declined under scenarios of continuous anthropogenic CO2 emission. This analysis underscores the complexity of carbonate system dynamics in a productive coastal plain estuary with large salinity gradients.

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What drives interannual variability of hypoxia in Chesapeake Bay: Climate forcing versus nutrient loading?

Cited by 99 publications

References 44 publications

Ecosystem Metabolism and Carbon Balance in Chesapeake Bay: A 30‐Year Analysis Using a Coupled Hydrodynamic‐Biogeochemical Model

Ecosystem Metabolism and Carbon Balance in Chesapeake Bay: A 30‐Year Analysis Using a Coupled Hydrodynamic‐Biogeochemical Model

Large Projected Decline in Dissolved Oxygen in a Eutrophic Estuary Due to Climate Change

Controls on Carbonate System Dynamics in a Coastal Plain Estuary: A Modeling Study

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