Modeling Hypoxia and Ecological Responses to Climate and Nutrients

We are developing modeling tools that can be used to predict ecological responses to climate and nutrient input management in coastal systems. This project is part of NOAA’s Coastal Hypoxia Research Program (CHRP).

Why We Care
Nutrient pollution in estuaries has contributed to the degradation of bottom habitats by causing algal blooms and resulting depletion of oxygen (hypoxia) from coastal waters. The lack of oxygen may lead to declines in fish populations. Despite the fact that many coastal regions have made major commitments to reduce nutrient loading and reverse this trend of declining water quality and habitat conditions, most estuaries in the U.S. continue to experience hypoxia and deteriorating water quality. Developing a successful nutrient restoration strategy is complicated by climate variability, because changes in temperature and salinity will also affect oxygen levels and available species habitat.

In many estuaries water quality monitoring and modeling programs have been developed to determine and predict ecological responses to nutrient inputs (loadings). We are improving the utility of such programs by developing modeling tools that are built in collaboration with resource managers, and that can be easily adapted for use in any coastal system.

What We Did
To help managers understand how the ecosystem will respond to changes in climate and nutrient inputs, we developed practical science-based predictive tools that can be readily implemented for any coastal system. The project combines:

1. historical analysis of existing data on climate, nutrients, and hypoxia, with
2. an identification assessment of mechanisms underlying the observed ecology,
3. development of numerical models to forecast and analyze water quality responses to climate and nutrient management, and
4. habitat evaluation of the variations in habitat size and quality for selected fish and invertebrate populations.

Our study sites included the partially-stratified Chesapeake Bay and the shallow, well-mixed Delaware Inland Bays. Information on variations in river flow, water temperature, and wind velocity was used in conjunction with water quality monitoring data to produce statistical models. These data will improve the understanding of how hypoxia responds to climate and nutrient loading variations.

The project was led by the University of Maryland’s Center for Environmental Science and included partners from the University of Delaware and Dalhousie University (Nova Scotia).

Benefits of Our Work
We worked closely with resource management agencies to develop a set of community-wide models usable by anyone involved in nutrient reduction planning and fisheries habitat protection. These models have advanced managers’ understanding of the factors controlling hypoxia. Selected accomplishments include:

• Developing a seasonal hypoxia forecast: The hypoxia model developed here, along with that developed from another CHRP project (Scavia et al.), have produced seasonal forecasts for Chesapeake Bay hypoxia over the last two years. The forecasts are valuable tools for promoting public and policy-makers’ awareness of the issue and, when compared against observations from Chesapeake Bay monitoring, in validating the link to nutrient pollution.
• Validating the relationship between nutrient control and hypoxia mitigation: This study demonstrated seasonally specific long-term trends in Chesapeake Bay hypoxia that indicated a significant relationship between nutrient load reductions and decreases in late summer hypoxia volume. Climatic factors were found to drive early summer hypoxia patterns, which exhibited an increase over time. An analysis of 60 years of monitoring data revealed seasonal differences in Chesapeake Bay hypoxia trends and driving forces indicating that nutrient controls have led to reduced hypoxia in late summer but large-scale climatic forces are promoting early summer hypoxia formation. The study showed that although climatic factors are influencing hypoxia and require adaptations to management approaches, nutrient controls remain a critical mitigation strategy for improving Chesapeake Bay water quality.
• Providing Delaware resource managers (Department of Natural Resources and Environmental Control – DNREC) with TMDL calculations to update their Pollution Control Strategy (PCS). Continuous monitoring of dissolved oxygen has demonstrated the hypoxia is by far the major water quality challenge facing the inland bays. The specific recommendation to the CMP and State of the Bay report was to put a greater emphasis on mechanistic modeling as a method of integrating data and understanding complex interactions that influence the efficacy of nutrient management, such as the relationship between tidal flushing through the dynamic Indian River Inlet and nutrient loading that continues to exceed goal set by the PCS.
• Developing an education module which focuses on hypoxia. The Center for Ocean Science Excellence Coastal Trends has developed a unique web-based science education module which focuses on hypoxia and contains video clips, real-time data, and computer animations that make the hypoxia concepts come alive for students. The contents of the website include a “Get Started” page with a short video about Dead Zones, a “Learn About” page which explains what dead zones are and how they are formed, an “Explore” page which provides details on seasonal and annual trends and other facts about dead zones, an “Investigate Current Research” which explains the research in which the team was involved, and an “Application to the Classroom” page which presents lessons and activities associated with the research that can be conducted in the classroom and which address the National Science Education Content Standards. It has been featured in three teacher professional development institutes to over 40 participants, used in the Horn Point STEM Center student activities for 45 students, and featured in an ocean science curriculum at the high school level titled “An Introduction to our Dynamic Ocean.” The curriculum is based on the Ocean Literacy Essential Principles and is currently piloted in 4 high schools and is taught in part by an additional 10 teachers. Lectures pertaining to hypoxia controls and consequences were presented (via interactive video conferencing and Distance-Learning) by CHRP PIs (Kemp and North).

For more information see the project web page at  http://northweb.hpl.umces.edu/CHRP/CHRP_home.htm