Ecological Forecasting and the Science of Hypoxia in Chesapeake Bay

Testa, Jeremy M.; Clark, J. Blake; Dennison, William C.; Donovan, E.; Fisher, Alexander W.; Ni, Wenfei; Parker, Matthew; Scavia, Donald; Spitzer, Suzanne E.; Waldrop, Anthony M.; Vargas, Vanessa M.D.; Ziegler, Gregory P.

doi:10.1093/biosci/bix048

Cited by 54 publications

(71 citation statements)

References 83 publications

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“…http://scavia.seas. umich.edu/hypoxia-forecasts/), and advance public understanding and participation (Testa et al 2017). While that particular model is limited to systems that are strongly one-dimensional longitudinally, other regression-based and simple biophysical models originally calibrated to hypoxic area (e.g.…”

Section: Resultsmentioning

confidence: 99%

Hypoxic volume is more responsive than hypoxic area to nutrient load reductions in the northern Gulf of Mexico—and it matters to fish and fisheries

Scavia

Justić

Obenour

et al. 2019

Environ. Res. Lett.

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While impacts of low oxygen on marine organisms have been reviewed from physiological and ecological perspectives, relating broad population-and ecosystem-level effects to the areal extent of hypoxia (dissolved oxygen concentration below 64 μM, or 2 mg l −1 ) has proven difficult. We suggest that hypoxic volume is a more appropriate metric compared to hypoxic area because volume better integrates the effects of hypoxia on ecological processes relevant to many marine taxa. In this paper, we compare the volume-based load responses from a simple biophysical model with results from an independent three-dimensional hydrodynamic-biogeochemical model, and discuss the implications with respect to potentially more ecologically-relevant hypoxia management goals. We also show that hypoxic volume appears more sensitive than hypoxic area to nutrient load reductions. Model simulations indicate that even under a modest 25% nitrogen load reduction, the thickness of the hypoxic layer in the northern Gulf of Mexico decreases markedly, and hypoxia remains localized to a relatively thin layer near the bottom that most fish and other mobile organisms can more effectively avoid. This finding should be considered when reviewing and potentially setting hypoxia management goals.

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Section: Resultsmentioning

confidence: 99%

Hypoxic volume is more responsive than hypoxic area to nutrient load reductions in the northern Gulf of Mexico—and it matters to fish and fisheries

Scavia

Justić

Obenour

et al. 2019

Environ. Res. Lett.

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“…Clear linkages in the production and consumption of these variables underscore their coupled changes in response to nutrient load reductions, temperature increases, and oxygen depletion. The most integrative alteration of a seasonal cycle we examined included a shift toward larger hypoxic volumes in spring-early summer and smaller volumes during late summerfall over the past 30 years (Murphy et al, 2011;Zhou et al, 2014;Testa et al, 2017). This springward shift in the maximum hypoxic volume did not correspond to significantly earlier hypoxia onset in the upper Bay (Figure 3), which has been shown to be strongly related to winter spring freshwater inputs and local bottom-water chlorophyll-a .…”

Section: Discussionmentioning

confidence: 98%

Nutrient- and Climate-Induced Shifts in the Phenology of Linked Biogeochemical Cycles in a Temperate Estuary

et al. 2018

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“…Numerous 3‐D numerical model implementations have been developed to study DO dynamics and hypoxia in the Chesapeake Bay (i.e., Cerco & Noel, ; Da et al, ; Feng et al, ; Irby et al, ; Li et al, ; Scully, ; Testa et al, ; Xia & Jiang, ) and have recently been compared and found to have similar skill in reproducing the mean and seasonal variability of DO (Irby et al, ). Here we used the implementation from Scully (), which is based on an implementation of the Regional Ocean Modeling System (ROMS) developed specifically for the Chesapeake Bay (ChesROMS; Xu et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…While the determination of whether a certain location experiences hypoxic conditions is relatively easy using modern instrumentation, quantifying the total volume of water experiencing hypoxic conditions is much more difficult. Accurately estimating the total amount of hypoxic volume (HV) integrated over the full year (i.e., the cumulative hypoxic volume [HV C ]) is even more challenging (Bever et al, ), yet is particularly critical for managers who need to determine whether management efforts, such as those aimed at reducing anthropogenic nutrient inputs, are resulting in an interannual trend of decreasing hypoxia (Anderson et al, ; Brady et al, ; Del Giudice et al, ; Irby et al, ; Scavia et al, ; Testa et al, ).…”

Section: Introductionmentioning

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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Ecological Forecasting and the Science of Hypoxia in Chesapeake Bay

Cited by 54 publications

References 83 publications

Hypoxic volume is more responsive than hypoxic area to nutrient load reductions in the northern Gulf of Mexico—and it matters to fish and fisheries

Hypoxic volume is more responsive than hypoxic area to nutrient load reductions in the northern Gulf of Mexico—and it matters to fish and fisheries

Nutrient- and Climate-Induced Shifts in the Phenology of Linked Biogeochemical Cycles in a Temperate Estuary

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

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