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Analysis of Chesapeake Bay Hypoxia and Stratification


The depletion of dissolved oxygen from coastal waters (i.e., hypoxia) due to anthropogenic nutrient over-enrichment is a major water quality problem worldwide.  In the Chesapeake Bay, hypoxia has been a persistent summertime feature for decades with effects on ecosystem structure, fisheries habitat, and overall environmental quality.  Despite comprehensive modeling and monitoring programs, the complex hydrodynamics, biogeochemistry, and varying inputs from a large watershed have led to uncertainty about the response of Bay hypoxia to management actions. 

Fig. 1
Dissolved oxygen (DO) spatially interpolated using 4 different methods and observations collected May 26-28, 1992 at 8 m deep.

In this study, we make full use of a rich set of historical monitoring data recently compiled into a prototypical environmental observatory, the Chesapeake Bay Environmental Observatory (CBEO), to develop integrated statistical and mechanistic modeling tools for understanding the extent, timing, and causes of Bay hypoxia.  Our research involves developing new methods for 4D (i.e., space and time) interpolation of existing observational data and using these methods to unravel the long-term trends and relationships between Chesapeake Bay hypoxia, stratification, nutrient loads, and regional climatic forces. The new interpolation methods have been used to develop a summertime forecast of Bay anoxia for Chesapeake Ecocheck, allowing for public dissemination of our preliminary findings on the varying influences of physical and biological factors during different times of the summer.  Results from this research have the potential to address pressing science questions about Bay water quality by quantifying the strength, relationship, and timing of hypoxia and stratification increases.  Some of these findings, as well as the new integrated statistical and mechanistic modeling methods, will be transferable to other coastal systems worldwide. 

Interpolated density profile along main channel of the Chesapeake Bay for June 13-15, 2005, showing the typical vertical density stratification that develops in late spring.

Keywords: Water quality, hypoxia, Chesapeake Bay, interpolation, modeling
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Rebecca R. Murphy

JHU Student
PhD Student
Project Manager for Chesapeake Bay Environmental Observatory

Whiting School of Engineering

Department of Geography and Environmental Engineering

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William P. Ball

GWP Steering Committee
Associate Director, Global Water Program
Associate Director, Center for Water and Health Faculty Advisor, JHU Student Chapter of Engineers Without Borders-USA

Whiting School of Engineering

Department of Geography and Environmental Engineering (Joint Appointment) Department of Civil Environmental Engineering

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