Hypoxia in the Northern Gulf of Mexico

Acknowledgments

Contents

List of Figures

List of Tables

Contributors

Glossary

List of Acronyms and Symbols

Conversion Factors and Abbreviations

Executive Summary

Findings

Recommendations for Monitoring and Research

Recommendations for Adaptive Management

Management Options

Protecting and Enhancing Social Welfare in the Basin

Conclusion

1 Introduction

1.1 Hypoxia and the Northern Gulf of Mexico A Brief Overview

1.2 Science and Management Goals for Reducing Hypoxia

1.3 Hypoxia Study Group

1.4 The Study Groups Approach

2 Characterization of Hypoxia

2.1 Historical Patterns and Evidence for Hypoxia on the Shelf

2.2 The Physical Context

2.2.1 Oxygen Budget: General Considerations

2.2.2 Vertical Mixing as a Function of Stratification and Vertical Shear

2.2.3 Changes in Mississippi River Hydrology and Their Effects on Vertical Mixing

2.2.4 Zones of Hypoxia Controls

2.2.5 Shelf Circulation: Local Versus Regional

2.3 Role of N and P in Controlling Primary Production

2.3.1 Nitrogen and Phosphorus Fluxes to the NGOM Background

2.3.2 N and P Limitation in Different Shelf Zones and Linkages Between High Primary Production Inshore and the Hypoxic Regions Farther Offshore

2.4 Other Limiting Factors and the Role of Si

2.5 Sources of Organic Matter to the Hypoxic Zone

2.5.1 Sources of Organic Matter to NGOM: Post 2000 Integrated Assessment

2.5.2 Advances in Organic Matter Understanding: Characterization and Processes

2.5.3 Synthesis Efforts Regarding Organic Matter Sources

2.6 Denitrification, P Burial, and Nutrient Recycling

2.7 Possible Regime Shift in the Gulf of Mexico

2.8 Single Versus Dual Nutrient Removal Strategies

2.9 Current State of Forecasting

3 Nutrient Fate, Transport, and Sources

3.1 Temporal Characteristics of Streamflow and Nutrient Flux

3.1.1 MARB Annual and Seasonal Fluxes

3.1.1.1 Annual Patterns

3.1.1.2 Seasonal Patterns

3.1.2 Subbasin Annual and Seasonal Flux

3.1.2.1 Annual Patterns

3.1.2.2 Annual Flux Estimates

3.1.2.3 Annual Yield Estimates

3.1.2.4 Seasonal Patterns

3.2 Mass Balance of Nutrients

3.2.1 Cropping Patterns

3.2.2 Nonpoint Sources

3.2.3 Point Sources

3.3 Nutrient Transport Processes

3.3.1 Aquatic Processes

3.3.2 Freshwater Wetlands

3.3.3 Nutrient Sources and Sinks in Coastal Wetlands

3.4 Ability to Route and Predict Nutrient Delivery to the Gulf

3.4.1 SPARROW Model

3.4.2 SWAT Model

3.4.3 IBIS/THMB Model

3.4.4 Discussion and Comparison of Models

3.4.5 Targeting

3.4.6 Model Uncertainty

4 Scientific Basis for Goals and Management Options

4.1 Adaptive Management

4.2 Setting Targets for Nitrogen and Phosphorus Reduction

4.3 Protecting Water Quality and Social Welfare in the Basin

4.3.1 Assessment and Review of the Cost Estimates from the CENR Integrated Assessment

4.3.2 Other Large-Scale Integrated Economic and Biophysical Models for Agricultural Nonpoint Sources

4.3.3 Research Assessing the Basin-Wide Co-benefits

4.3.4 Principles of Landscape Design

4.4 Cost-Effective Approaches for Nonpoint Source Control

4.4.1 Voluntary Programs -- Without Economic Incentives

4.4.2 Existing Agricultural Conservation Programs

4.4.3 Emissions and Water Quality Trading Programs

4.4.4 Agricultural Subsidies and Conservation Compliance Provisions

4.4.5 Taxes

4.4.6 Eco-labeling and Consumer Driven Demand

4.5 Options for Managing Nutrients, Co-benefits, and Consequences

4.5.1 Agricultural Drainage

4.5.1.1 Alternative Drainage System Design and Management

4.5.1.2 Bioreactors

4.5.2 Freshwater Wetlands

4.5.2.1 Nitrogen

4.5.2.2 Phosphorus

4.5.3 Conservation Buffers

4.5.4 Cropping Systems

4.5.5 Animal Production Systems

4.5.5.1 System Development and Nutrient Flows

4.5.5.2 Manure as a Component of N and P Mass Balances

4.5.5.3 Remedial Strategies

4.5.5.4 Alternative Manure Management Technologies

4.5.6 In-Field Nutrient Management

4.5.6.1 Fertilizer Sources

4.5.6.2 Fertilizer Use and Application Technology

4.5.6.3 Watershed-Scale Fertilizer Management

4.5.6.4 Controlled-Release Fertilizers

4.5.6.5 Effects of N Management on Soil Resource Sustainability

4.5.6.6 Precision Agriculture Management Tools for Nitrogen

4.5.6.7 Precision Agriculture Management Tools for Phosphorus

4.5.6.8 Nutrient Management Planning Strategies

4.5.7 Effective Actions for Other Nonpoint Sources

4.5.7.1 Atmospheric Deposition

4.5.7.2 Residential and Urban Sources

4.5.8 Most Effective Actions for Industrial and Municipal Sources

4.5.9 Ethanol and Water Quality in the MARB

4.5.9.1 Water Quality Implications of Projected Grain-Based Ethanol Production Levels

4.5.9.2 Impacts on Nutrient Application to Corn

4.5.9.3 Grain Versus Cellulosic Ethanol and Water Quality

4.5.10 Integrating Conservation Options

5 Summary of Findings and Recommendations

5.1 Characterization of Hypoxia

5.2 Nutrient Fate, Transport, and Sources

5.3 Goals and Management Options

5.4 Conclusion

Appendices

Appendix A: Studies on the Effects of Hypoxia on Living Resources

Appendix B: Flow Diagrams and Mass Balance of Nutrients

Global Material Cycles

Atmospheric Deposition

Appendix C: Animal Production Systems

Intensification of Animal Feeding Operations

Nutrient Budgets

Nutrient Surpluses

Targeting Remedial Strategies Within the MARB

Managing Manures

Crop Selected to Receive Manure Application

Rate and Frequency of Application

Intensity and Duration of Grazing

Stream-Bank Fencing

Appendix D: Calculation of Point Source Inputs of N and P

Appendix E: USUSEPAs Guidance on Nutrient Criteria

Comparison of SAB Nitrogen and Phosphorus Recommendations with USEPA Nitrogen and Phosphorus Criteria Recommended Reference Conditions ' Submitted by USEPA's Office of Water, 8-24-07.

A More Comprehensive Approach

References

Subject Index