Factors Controlling Hypoxia Occurrence in Estuaries, Chester River, Chesapeake Bay

Tian, Richard

doi:10.3390/w12071961

Cited by 12 publications

(8 citation statements)

References 46 publications

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“…The ratio of phosphorus (PO 4 ), nitrogen (NO 23 + NH 4 ), and silica concentrations to their respective half-saturation coefficients indicated that at both the upstream and downstream stations, none of the above nutrients were limiting, except for phosphorus during a brief period during winter-spring (i.e., ratios >1, data not shown), during which GPP was reduced by PO 4 load reductions scenarios (Figure 10). Tian (2020) recently reported that nutrient loading was an important factor controlling hypoxia in the Chester River using a multi-year numerical model simulation, but the reported half-saturation coefficients for nitrogen and phosphorus uptake (0.5 mg N L −1 and 0.0025 mg P L −1 ) were much larger than those used in the other Chesapeake water quality models (e.g., 0.007-0.025 mg N L −1 ) Feng et al 2015;Cerco and Noel 2017). This clearly indicates that modest alterations in nutrient loading rates may be expected to have a much more limited impact on phytoplankton growth and hypoxia than the mainstem Chesapeake Bay and other nutrient-limited estuaries.…”

Section: Discussionmentioning

confidence: 99%

Modeling Impacts of Nutrient Loading, Warming, and Boundary Exchanges on Hypoxia and Metabolism in a Shallow Estuarine Ecosystem

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Basenback

Shen

et al. 2021

J American Water Resour Assoc

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We sought to investigate the impacts of nutrient loading, warming, and open‐water boundary exchanges on a shallow estuary through idealized numerical model experiments. We performed these simulations using a stand‐alone implementation of the Regional Ocean Modeling System‐Row‐Column AESOP biogeochemical model in the Chester River estuary, a tributary estuary within the Chesapeake Bay estuarine complex. We found that metabolic rates were elevated in the shallow tributary creeks of the estuary relative to open waters and that rates of gross primary production, respiration, and net ecosystem metabolism were a function of both water temperature and local phytoplankton biomass. Warming 0.75°C and 1.25°C led to reductions in dissolved oxygen concentrations throughout the estuary. Reductions (50%) in dissolved nitrogen and phosphorus loading did not substantially alter hypoxic volumes in this turbid, nutrient‐rich estuary, but warming increased hypoxic volumes by 20%–30%. Alterations of the open‐water boundary that represent improved oxygen concentrations in the adjacent Chesapeake Bay mainstem led to more substantial relief of hypoxia in model simulations than nutrient reductions (~50% reductions in hypoxia). These simulations reveal the complex interplay of watershed nutrient inputs and horizontal exchange in a small tributary estuary, including the finding that future warming and nutrient reduction effects on Chesapeake Bay hypoxia will be translated to some tributary estuaries like the Chester River.

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Section: Discussionmentioning

confidence: 99%

Modeling Impacts of Nutrient Loading, Warming, and Boundary Exchanges on Hypoxia and Metabolism in a Shallow Estuarine Ecosystem

Testa

Basenback

Shen

et al. 2021

J American Water Resour Assoc

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“…Furthermore, Li et al (2016) concluded that variability in N load is the main driver of interannual variability of hypoxia in the Bay. On a more local scale, Tian (2020) reported that nutrient loads determine the intensity and variability in hypoxia in the Chester River estuary.…”

Section: Estuarine Response To Changes In Nutrient Loadsmentioning

confidence: 99%

Progress in reducing nutrient and sediment loads to Chesapeake Bay: Three decades of monitoring data and implications for restoring complex ecosystems

et al. 2023

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For over three decades, Chesapeake Bay (USA) has been the focal point of a coordinated restoration strategy implemented through a partnership of governmental and nongovernmental entities, which has been a classical model for coastal restoration worldwide. This synthesis aims to provide resource managers and estuarine scientists with a clearer perspective of the magnitude of changes in water quality within the Bay watershed, including nitrogen (N), phosphorus (P), and sediment for the River Input Monitoring (RIM) watershed and the unmonitored below‐RIM watershed. The flow‐normalized N load from the RIM watershed has declined in the period of 1985–2017, but P and sediment loads have lacked progress. Reductions of riverine N are largely driven by reductions of point sources and atmospheric deposition. Future reductions will require significant progress in managing agricultural nonpoint sources. The below‐RIM watershed, which comprises a disproportionately high fraction of inputs to the Bay, has shown long‐term declines in major sources, including point sources (N and P), atmospheric deposition (N), manure (N and P) and fertilizer (P), based on a combination of monitoring and modeling assessments. To date, the Bay cleanup efforts have achieved some progress toward reducing nutrients from the watershed, which have resulted in improving water quality in the estuary. However, further reductions are critical to achieve the Chesapeake Bay Total Maximum Daily Load goals, and emerging challenges due to Conowingo Reservoir, legacy nutrients, climate change, and population growth should be considered. Continued monitoring, modeling, and assessment are critically important for informing the restoration of this complex ecosystem.This article is categorized under: Science of Water > Water Quality Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness

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“…These heterogeneous conditions emerge from strong spatial patterns of phytoplankton biomass, as well as interactions between the coastline and current that drive changes in current velocity and direction. For example, Tian (2019) and Tian (2020) found that interactions between physics and coastline meanders can generate complex advection features that fundamentally alter biogeochemical processes and water quality properties in the Chester River. Helical advection resulting from interactions between currents and the coastline can interrupt saltwater intrusion, vertical diffusivity, Classification And Regression Tree (CART) analysis of DO simulation time-series data at the upper estuary station XHH3851.…”

Section: Physical Impacts On Do Variabilitymentioning

confidence: 99%

Simulation of high-frequency dissolved oxygen dynamics in a shallow estuary, the Corsica River, Chesapeake Bay

et al. 2022

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Understanding shallow water biogeochemical dynamics is a challenge in coastal regions, due to the presence of highly variable land-water interface fluxes, tight coupling with sediment processes, tidal dynamics, and diurnal variability in biogeochemical processes. While the deployment of continuous monitoring devices has improved our understanding of high-frequency (12 - 24 hours) variability and spatial heterogeneity in shallow regions, mechanistic modeling of these dynamics has lagged behind conceptual and empirical models. The inherent complexity of shallow water systems is represented in the Corsica River estuary, a small basin within the Chesapeake Bay ecosystem, where abundant monitoring data have been collected from long-term monitoring stations, continuous monitoring sensors, synoptic sensor surveys, and measurements of sediment-water fluxes. A state-of-the-art modeling system, the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM), was applied to the Corsica domain with a high-resolution grid and nutrient loads from the most recent version of the Chesapeake Bay watershed model. The Corsica SCHISM model reproduced observed high-frequency variability in dissolved oxygen, as well as seasonal variability in chlorophyll-a and sediment-water fluxes. Time-series signal analyses using Empirical Model Decomposition and spectral analysis revealed that the diurnal and M2 tide frequencies are the dominant high-frequency modes and physical transport contributes a larger share to dissolved oxygen budgets than biogeochemical processes on an hourly time scale. Heterogeneity and patchiness in dissolved oxygen resulting from phytoplankton distributions and geometry-driven eddies amplify the physical transport effect, and on longer time scales oxygen is controlled more by photosynthesis and respiration. Our simulation demonstrates that interactions among physical and biological dynamics generate complex high-frequency variability in water quality and non-linear reposes to nutrient loading and environmental forcing in shallow water systems.

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Factors Controlling Hypoxia Occurrence in Estuaries, Chester River, Chesapeake Bay

Cited by 12 publications

References 46 publications

Modeling Impacts of Nutrient Loading, Warming, and Boundary Exchanges on Hypoxia and Metabolism in a Shallow Estuarine Ecosystem

Modeling Impacts of Nutrient Loading, Warming, and Boundary Exchanges on Hypoxia and Metabolism in a Shallow Estuarine Ecosystem

Progress in reducing nutrient and sediment loads to Chesapeake Bay: Three decades of monitoring data and implications for restoring complex ecosystems

Simulation of high-frequency dissolved oxygen dynamics in a shallow estuary, the Corsica River, Chesapeake Bay

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