Resolving spatiotemporal characteristics of the seasonal hypoxia cycle in shallow estuarine environments of the Severn River and South River, MD, Chesapeake Bay, USA

Muller, Andrew C.; Muller, Diana Lynn; Muller, Arianna

doi:10.1016/j.heliyon.2016.e00157

Cited by 11 publications

(8 citation statements)

References 47 publications

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“…This study focuses on main stem hypoxia because it is the largest continuous expanse of hypoxia in the bay and occurs continuously for many months every year. Although hypoxia also occurs in the tributaries and shallows fringing the Bay (i.e., Breitburg, ) and affects water quality and biota in these areas (Muller et al, ), the tributaries and fringing shallows were not considered in this study because the hypoxia in these areas represents a relatively small water volume or occurs on diel time scales.…”

Section: Methodsmentioning

confidence: 99%

Estimating Hypoxic Volume in the Chesapeake Bay Using Two Continuously Sampled Oxygen Profiles

Bever¹,

Friedrichs

et al. 2018

JGR Oceans

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Low levels of dissolved oxygen (DO) occur in many embayments throughout the world and have numerous detrimental effects on biota. Although measurement of in situ DO is straightforward with modern instrumentation, quantifying the volume of water in a given embayment that is hypoxic (hypoxic volume (HV)) is a more difficult task; however, this information is critical for determining whether management efforts to increase DO are having an overall impact. This paper uses output from a three-dimensional numerical model to demonstrate that HV in Chesapeake Bay can be estimated well with as few as two vertical profiles. In addition, the cumulative hypoxic volume (HV C ; the total amount of hypoxia in a given year) can be calculated with relatively low uncertainty (<10%) if continuous DO data are available from two strategically positioned vertical profiles. This is because HV in the Chesapeake Bay is strongly constrained by the geometry of the embayment. A simple Geometric HV calculation method is presented and numerical model results are used to illustrate that for calculating HV C , the results using two daily-averaged profiles are typically more accurate than those of the standard method that interpolates bimonthly cruise data. Bimonthly data produce less accurate estimates of HV C because high-frequency changes in oxygen concentration, for example, due to regional-weather-or storm-induced changes in wind direction and magnitude, are not resolved. The advantages of supplementing cruise-based sampling with continuous vertical profiles to estimate HV C should be applicable to other systems where hypoxic water is constrained to a specific area by bathymetry.Plain Language Summary The Chesapeake Bay supports a diverse range of recreational and commercial fisheries. However, every summer the amount of oxygen dissolved in the bay's bottom water decreases to levels lethal for fish and shellfish, termed a "dead zone." To make informed management decisions and understand the health of the ecosystem, it is important to understand the variability in the dissolved oxygen and the amount of water with low dissolved oxygen. In this study, we used both observations collected from boats and three-dimensional computer models to demonstrate that the region of low dissolved oxygen is strongly constrained by the geometry of the Chesapeake Bay. Because of this geometric constraint, the amount of low dissolved oxygen water can be accurately calculated if continually monitored with only two vertical profiles. In contrast, the current method uses numerous locations sampled only twice per month. This study demonstrated that continuous vertical profiles at as few as two locations provide a better estimate of the volume of hypoxia in any given year. This means that the amount of hypoxic water can be estimated in real time using an ocean observing system that efficiently supplements the current monitoring program, because only a few continuous monitoring locations are needed.While the determination of whether a certain location experiences hypox...

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Section: Methodsmentioning

confidence: 99%

Estimating Hypoxic Volume in the Chesapeake Bay Using Two Continuously Sampled Oxygen Profiles

Bever¹,

Friedrichs

et al. 2018

JGR Oceans

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“…The dotted gizzard shad (DGS) also has a wide habitat range, while the flathead mullet (FHM) was observed to have a narrow habitat range and has a low tolerance for DO depletion. Carassius auratus 0-41 3…”

Section: Assessment Of Fish Habitat Volumementioning

confidence: 99%

“…However, many of those artificial waterways are eutrophic, because of high-concentration nutrients from nearby cities, and are affected by water pollution due to long retention times and poor water circulation [1]. Hypoxia, i.e., dissolved oxygen (DO) depletion, is a representative water quality problem that has been drastically increasing in shallow coastal and estuarine areas, as well as in estuarine waterways worldwide [2][3][4][5]. Hypoxia, which is defined as a DO level of less than 62.5 µmol/L (2.0 mg/L), develops wherever the consumption of oxygen by organisms or chemical processes exceeds the oxygen supply from adjacent water, the atmosphere, and photosynthesizing organisms [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, oxygen depletion is often caused by the oxidation of organic matter and reduced substances as well as by the advective intrusion of oxygen-poor waters from deeper layers or adjacent water bodies. As noted above, the hypoxia threshold is defined as a DO level below 2 mg/L in many studies [2][3][4][5]; however, the actual threshold for hypoxia and its associated effects can vary over time and space, depending on water temperature and salinity [6,7]. Hypoxia also has diverse effects on aquatic ecosystems.…”

Section: Introductionmentioning

confidence: 99%

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Modeling Summer Hypoxia Spatial Distribution and Fish Habitat Volume in Artificial Estuarine Waterway

Chong

Park

Lee

et al. 2018

Water

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This study analyzes the dissolved oxygen (DO) depletion or hypoxia formation affecting the ecological vulnerability of Gyeongin-Ara Waterway (GAW), an artificial estuarine waterway. The physical, chemical, and biochemical factors affecting the summer hypoxia dynamics and distribution are simulated and the habitat volumes of major fish species are calculated. CE-QUAL-W2, a two-dimensional hydrodynamic and water quality model, is applied for the simulation. Comparison with observation reveals that the salinity stratification, vertical DO gradient, and summer hypoxia characteristics are realistically reproduced by the model. Comprehensive analysis of the spatial distributions of the residence time, salinity, and DO concentration reveal that the residence time is longest at the bottom of a freshwater inflow zone. Accordingly, residence time is identified as the physical factor having the greatest influence on hypoxia. It is also clear that a hypoxic water mass diffuses towards the entire waterway during neap tides and summer, when the seawater inflow decreases. Based on the modeling results, the DO depletion drivers are identified and the hypoxic zone formation and distribution are sufficiently explained. Finally, fish habitat volumes are calculated. In particular, the survival habitat volume of Mugil cephalus is found to decrease by 32–34% as a result of hypoxia from July to August. The model employed in this study could be utilized to establish an operational plan for the waterway, which would increase fish habitat volumes.

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“…These temporal variations are caused by the combined effects of local DO dynamics and the transport of DO via the movement of water and therefore imply some degree of spatial variation. Spatial analysis of DO measured synoptically at multiple locations in the GOM shows various degrees of patchiness in hypoxia on kilometer scales (Zhang et al, 2009), and such spatial variation is common in other estuarine systems (e.g., Muller et al, 2016). Hypoxia in the GOM also varies in the vertical dimension.…”

Section: Introductionmentioning

confidence: 96%

Effects of spatial variability on the exposure of fish to hypoxia: a modeling analysis for the Gulf of Mexico

et al. 2021

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Abstract. The hypoxic zone in the northern Gulf of Mexico varies spatially (area, location) and temporally (onset, duration) on multiple scales. Exposure of fish to hypoxic dissolved oxygen (DO) concentrations (< 2 mg L−1) is often lethal and avoided, while exposure to 2 to 4 mg L−1 occurs readily and often causes the sublethal effects of decreased growth and fecundity for individuals of many species. We simulated the movement of individual fish within a high-resolution 3-D coupled hydrodynamic water quality model (FVCOM-WASP) configured for the northern Gulf of Mexico to examine how spatial variability in DO concentrations would affect fish exposure to hypoxic and sublethal DO concentrations. Eight static snapshots (spatial maps) of DO were selected from a 10 d FVCOM-WASP simulation that showed a range of spatial variation (degree of clumpiness) in sublethal DO for when total sublethal area was moderate (four maps) and for when total sublethal area was high (four maps). An additional case of allowing DO to vary in time (dynamic DO) was also included. All simulations were for 10 d and were performed for 2-D (bottom layer only) and 3-D (allows for vertical movement of fish) sets of maps. Fish movement was simulated every 15 min with each individual switching among three algorithms: tactical avoidance when exposure to hypoxic DO was imminent, strategic avoidance when exposure had occurred in the recent past, and default (independent of DO) when avoidance was not invoked. Cumulative exposure of individuals to hypoxia was higher under the high sublethal area snapshots compared to the moderate sublethal area snapshots but spatial variability in sublethal concentrations had little effect on hypoxia exposure. In contrast, relatively high exposures to sublethal DO concentrations occurred in all simulations. Spatial variability in sublethal DO had opposite effects on sublethal exposure between moderate and high sublethal area maps: the percentage of fish exposed to 2–3 mg L−1 decreased with increasing variability for high sublethal area but increased for moderate sublethal area. There was also a wide range of exposures among individuals within each simulation. These results suggest that averaging DO concentrations over spatial cells and time steps can result in underestimation of sublethal effects. Our methods and results can inform how movement is simulated in larger models that are critical for assessing how management actions to reduce nutrient loadings will affect fish populations.

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Resolving spatiotemporal characteristics of the seasonal hypoxia cycle in shallow estuarine environments of the Severn River and South River, MD, Chesapeake Bay, USA

Cited by 11 publications

References 47 publications

Estimating Hypoxic Volume in the Chesapeake Bay Using Two Continuously Sampled Oxygen Profiles

Estimating Hypoxic Volume in the Chesapeake Bay Using Two Continuously Sampled Oxygen Profiles

Modeling Summer Hypoxia Spatial Distribution and Fish Habitat Volume in Artificial Estuarine Waterway

Effects of spatial variability on the exposure of fish to hypoxia: a modeling analysis for the Gulf of Mexico

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