Hypoxia Report

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Scien c Assessment of Hypoxiain U.S. Coastal Waters

Interagency Working Groupon Harmful Algal Blooms, Hypoxia, andHuman HealthSeptember 2010

Dissolved oxygen (mg/L)

Salinity

D e p

t h ( m )

60

32 34

0

80


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This document should be cited as follows:

Committee on Environment and Natural Resources. 2010. Scienti c Assessment of Hypoxia

in U.S. Coastal Waters. Interagency Working Group on Harmful Algal Blooms, Hypoxia, andHuman Health of the Joint Subcommittee on Ocean Science and Technology. Washington,DC.

Acknowledgements:Many scientists and managers from Federal and state agencies, universities, and researchinstitutions contributed to the knowledge base upon which this assessment depends. Manythanks to all who contributed to this report, and special thanks to John Wickham and LynnDancy of NOAA National Centers for Coastal Ocean Science for their editing work.

Cover and Sidebar Photos:

Background Cover and Sidebar: MODIS satellite image courtesy of the Ocean BiologyProcessing Group, NASA Goddard Space Flight Center.Cover inset photos from top: 1) CTD rosette, EPA Gulf Ecology Division; 2) CTD pro le takenoff the Washington coast, project funded by Bonneville Power Administration and NOAAFisheries; Joseph Fisher, OSU, was chief scientist on the FV Frosti; data were processedand provided by Cheryl Morgan, OSU); 3) Dead sh, Christopher Deacutis, Rhode IslandDepartment of Environmental Management; 4) Shrimp boat, EPA.


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Scienti c Assessment of Hypoxia in U.S. Coastal Waters i


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Scienti c Assessment of Hypoxia in U.S. Coastal Watersii

This report is dedicated to the memory of Dr. Peter Eldridge, who was a member of the hypoxia report writing team and a research scientist with the U.S.Environmental Protection Agency. Peter had a great love and passion for the ocean,the environment, and science. Among Peters scienti c contributions was the development of ecosystem models to address coastal environmental issues, such as coastal hypoxia, food web changes, and seagrass loss. Peters friendship and enthusiasm for science will be greatly missed.

Peter Eldridge (1946 2008)


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Scienti c Assessment of Hypoxia in U.S. Coastal Waters iii

Arctic Research CommissionJohn Farrell

Department of AgricultureLouie Tupas

Department of CommerceNational Oceanic and AtmosphericAdministrationCraig McLeanSteve MurawskiRoger Parsons

Department of DefenseU.S. Army Corps of EngineersCharles ChesnuttJoan Pope

Department of DefenseOf ce of Naval ResearchLinwood VincentJames Eckman

Department of EnergyOf ce of ScienceJulie CarruthersJames Ahlgrimm

Department of Health and Human ServicesCenters for Disease Control and PreventionLorraine BackerG. David Williamson

Department of Health and Human ServicesFood and Drug AdministrationRobert DickeyWilliam Jones

Department of Health and Human ServicesNational Institutes of HealthAllen Dearry

Department of Homeland SecurityU.S. Coast Guard

Jonathan Berkson

Department of the InteriorKameran OnleyTim Petty

Department of the InteriorMinerals Management ServiceJames KendallWalter Johnson

Department of the InteriorUnited States Geological SurveyJohn HainesLinda Gunderson

Department of JusticeMatt LeopoldAmber Blaha

Department of StateDavid BaltonLiz Tirpak

Department of TransportationMaritime AdministrationRichard Corley

U.S. Environmental Protection AgencyKevin TeichmanSteven Hedtke

Executive Of ce of the PresidentCouncil on Environmental QualityHardy Pearce

Executive Of ce of the PresidentDomestic Policy CouncilPaul Skoczylas

Executive Of ce of the PresidentOf ce of Management and BudgetStuart LevenbachKimberly Miller

Executive Of ce of the PresidentOf ce of Science and Technology PolicyJerry Miller

Joint Chiefs of StaffRobert WinokurNadeem Ahmad

National Aeronautics and SpaceAdministrationJack KayeEric Lindstrom

National Science FoundationTim KilleenJulie MorrisPhil Taylor

Marine Mammal CommissionRobert GisinerTim Ragen

Smithsonian InstitutionLeonard Hirsch

Joint Subcommittee on Ocean Science and Technology(JSOST)

Steve Murawski, DOC/NOAA, Co-ChairTim Killeen, NSF, Co-Chair

Jerry Miller, OSTP, Co-Chair


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Scienti c Assessment of Hypoxia in U.S. Coastal Watersiv

Lorraine C. Backer (Co-Chair)Centers for Disease Control and Prevention

Paul A. Sandifer (Co-Chair)

National Oceanic and Atmospheric Administration Paula Bontempi Alternate: Fredric LipschultzNational Aeronautics and Space Administration

Herbert T. Buxton United States Geological Survey

David Garrison National Science Foundation

Rob MagnienAlternate: Quay Dortch National Oceanic and Atmospheric Administration

Steven Plakas U.S. Food and Drug Administration

Tim RagenAlternate: Bob Gisiner Marine Mammal Commission

Teri RowlesNational Oceanic and Atmospheric Administration

Joyce SaltsmanU.S. Food and Drug Administration

Juli TrtanjNational Oceanic and Atmospheric Administration

Frederick L. Tyson

National Institute of Environmental HealthSciences

Usha VaranasiAlternate: Walton Dickhoff National Oceanic and Atmospheric Administration

William RussoU.S. Environmental Protection Agency

Mark Walbridge Department of Agriculture

Scienti c support staff :

Elizabeth B. Jewett Cary B. Lopez Carolyn Sotka Virginia FayNational Oceanic and Atmospheric Administration

Cheryl L. FossaniNational Science Foundation

JSOST Interagency Working Group onHarmful Algal Blooms, Hypoxia and Human Health (IWG-4H)

Primary AuthorsElizabeth B. Jewett, Cary B. Lopez, David M.Kidwell, Suzanne B. Bricker National Oceanic and Atmospheric Administration

Marianne K. Burke , Mark R. WalbridgeU.S. Department of Agriculture

Peter M. Eldridge , Richard M. Greene, JamesD. Hagy IIIU.S. Environmental Protection Agency

Herbert T. BuxtonU.S. Geological Survey

Robert J. DiazVirginia Institute of Marine Science

Major Contributors

Cheryl BrownU.S. Environmental Protection Agency

Bill PetersonNational Oceanic and Atmospheric Administration

Jay Peterson and Cheryl MorganOregon State University


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Scienti c Assessment of Hypoxia in U.S. Coastal Waters v

Table of Contents

vi List of Figuresvi List of Tables

vii List of Boxes

vii List of Case Studies

viii List of Acronyms

1 Executive Summary

7 Chapter 1. Legislative Background, Report Overview and DevelopmentProcess

11 Chapter 2. Causes and Status of Hypoxia in U.S. Coastal Waters25 Chapter 3. Federal Hypoxia and Watershed Science Research: Status and

Accomplishments

47 Chapter 4. Future Research Directions and Interagency Coordination

57 References

68 Appendices

69 Appendix I. Federal Agency Hypoxia or Hypoxia-related Research

83 Appendix II. Geographic Case Studies

118 Appendix III. Table of U.S. Systems Impacted by Hypoxia
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Page #

12 Figure 1. Global distribution of systems affected by low dissolved oxygen.

14 Figure 2. Change in number of U.S. coastal areas experiencing hypoxia from 12 documented areas in 1960

to over 300 now.15 Figure 3. Comparison of the relative contribution of major sources of nitrogen pollution in three coastal

ecosystems experiencing hypoxia.

16 Figure 4. Conceptual diagram illustrating development and effects of hypoxia in strati ed waters.

18 Figure 5. The range of ecological impacts exhibited as dissolved oxygen levels drop from saturation toanoxia.

19 Figure 6. Conceptual view of how hypoxia alters ecosystem energy ow with example systems.

23 Figure 7. Relative magnitude and contribution of land management practices versus climate change factorsto expansion or contraction of low dissolved oxygen.

25 Figure 8. Conceptual diagram explaining how, in an adaptive management framework, scienti c researchinforms management of environmental problems such as hypoxia.

27 Figure 9. Schematic describing general areas of hypoxia-related research.

29 Figure 10. Hypoxia is most intensively monitored in the largest and most impacted coastal systems in theUnited States. Examples include: a) Long Island Sound, b) Chesapeake Bay, c) Lake Erie, and d) NorthernGulf of Mexico.

31 Figure 11. Ensemble forecasts of the response of hypoxia to changes in riverine nitrogen load.

33 Figure 12. Trends in catch per unit effort for brown shrimp in the northern Gulf of Mexico.

34 Figure 13. Relationship between annual landings of brown shrimp in the northern Gulf of Mexico and thesize of the hypoxic zone.

35 Figure 14. Map of Gulf of Mexico with darker shaded areas indicating denser sh populations in the1960s.37 Figure 15. Estimated nitrate delivery to the Gulf of Mexico for April, May, and June in1979 - 2008.

40 Figure 16. Percent of the United States drained by arti cial means such as tile drains.

42 Figure 17. 2007 Map of CEAP projects.

83 Figure A1. Geographic locations of hypoxia case studies.

List of Figures

List of Tables Page #

13 Table 1. Percentage of U.S. estuaries and coastal water bodies with reports of hypoxia.20 Table 2. Principal ecosystem characteristics and services impacted by hypoxia.

21 Table 3. Examples of hypoxia-related economic impacts.

22 Table 4. Estimated in uence of climate drivers on the extent and severity of hypoxia.

30 Table 5. Models developed since 2002 to forecast or simulate Gulf of Mexico hypoxia.

84 Table A1. Comparison of Physical Systems Represented by Case Studies in Appendix II.


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Page #

7 Box 1. HABHRCA 2004 Reports and Assessments

8 Box 2. Legislation Relevant to Hypoxia

11 Box 3. Hypoxia De nition

26 Box 4. Adaptive Management Approach for Gulf of Mexico Hypoxic Zone

27 Box 5. Adaptive Management Approach for Chesapeake Bay

28 Box 6. Sound Science Leads to Signi cant Reductions in Hypoxia in Long Island Sound

29 Box 7. Hypoxia Advanced Warning Protects Drinking Water

38 Box 8. Application of SPARROW for Reducing Nutrients to the Gulf of Mexico

39 Box 9. EPA Works Closely With States to Develop and Adopt Nutrient Criteria

41 Box 10. Soil Drainage Research in Ohio

43 Box 11. Monitoring Winter Cover Crop Performance from Space

43 Box 12. USDA Conservation Research Program Bene ts in the Mississippi River Basin

54 Box 13. USGS Deployment of New Instruments to Measure Water Flow and Sediment Flux

List of Boxes

Page #

85 Long Island Sound

89 Lake Erie

92 Chesapeake Bay

99 Pensacola Bay

102 Northern Gulf of Mexico

108 Northeast Paci c Continental Shelf

112 Yaquina Bay

116 Hood Canal

List of Case Studies
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ADMS Agricultural Drainage Management SystemsARS Agricultural Research Service, USDABMP best management practice

CBEMP Chesapeake Bay Environmental ModelPackageCEAP Conservation Effects Assessment ProjectCENR Committee on Environment and NaturalResourcesCHRP Coastal Hypoxia Research Program, NOAACRP Conservation Reserve Program, USDACSREES Cooperative State Research, Education, andExtension Service, USDADOD U.S. Department of DefenseDOE U.S. Department of EnergyDOI U.S. Department of the InteriorEISA Energy Independence and Security Act of 2007EMAP Environmental Monitoring and AssessmentProgramEMVL Environmental Modeling and VisualizationLaboratoryEPA U.S. Environmental Protection AgencyERS Economic Research Service, USDAFSA Farm Service Agency, USDAFVCOM Finite Volume Community Ocean ModelGLNPO Great Lakes National Program Of ce, EPAHAB harmful algal bloomHABHRCA

Harmful Algal Bloom and Hypoxia Researchand Control ActHCDOP Hood Canal Dissolved Oxygen ProgramIFYLE International Field Years on Lake ErieIOOS Integrated Ocean Observing SystemIWG-4H Interagency Working Group on HABs, Hypoxia,and Human HealthLaMP Lakewide Management Plan, Lake ErieLISS Long Island Sound StudyLMAV Lower Mississippi Alluvial ValleyLUMCON Louisiana Universities Marine ConsortiumMARB Mississippi Atchafalaya River BasinMDA Maryland Department of AgricultureNASA National Aeronautics and Space AdministrationNAWQA National Water-Quality Assessment Program,USGSNBEP Narragansett Bay Estuary ProgramNCER National Center for Environmental Research,EPANCII Nutrient Control Implementation Initiative

NEP National Estuary Program, EPANERL National Exposure Research Laboratory, EPANERRS National Estuarine Research Reserve System,NOAA

NHEERL National Health and Environment EffectsResearch Laboratory, EPANMFS National Marine Fisheries Service, NOAANOAA National Oceanic and AtmosphericAdministration, U.S. Department of CommerceNRC National Research CouncilNRCS Natural Resources Conservation Service, USDANRL Naval Research Laboratory, U.S. Department ofDefenseNRMRL National Risk Management ResearchLaboratory, EPANSF National Science Foundation

OST Of ce of Science and Technology, EPAOW Of ce of Water, EPAOWOW Of ce of Wetlands, Oceans, and Watersheds,EPAPDO model Nitrogen-Phytoplankton-Detritus-OxygenmodelReCON Real-time Coastal Observation NetworkREMM Riparian Ecosystem Management ModelReNuMa Regional Nutrient Management ModelROMS Regional Ocean Model SystemRZWQM Root Zone Water Quality ModelSAV submerged aquatic vegetationSEAMAP Southeast Area Monitoring and AssessmentProgram, NOAASPARROW SPAtially Referenced Regressions OnWatershed AttributesSTAR Science to Achieve Results Program, EPASTEWARDS Sustaining the Earths WatershedsThrough Research, Data Analysis, and SynthesisSTORET STOrage and RETrieval data system, EPASWAT Soil and Water Assessment ToolSWMP System-Wide Monitoring ProgramSWWRP System-Wide Water Resources ProgramTMDL

total maximum daily loadUSACE U.S. Army Corps of Engineers, DODUSDA U.S. Department of AgricultureUSFWS U.S. Fish and Wildlife Service, DOIUSGS U.S. Geological Survey, DOIWRSIS Wetland Reservoir Subirrigation System

List of Acronyms


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Scienti c Assessment of Hypoxia in U.S. Coastal Waters 1

The Problem

T he occurrence of hypoxia, or low dissolvedoxygen, is increasing in coastal watersworldwide and represents a signi cant threat tothe health and economy of our Nations coastsand Great Lakes. This trend is exempli edmost dramatically off the coast of Louisiana andTexas, where the second largest eutrophication-related hypoxic zone in the world is associatedwith the nutrient pollutant load discharged by theMississippi and Atchafalaya Rivers.

Aquatic organisms require adequate dissolved

oxygen to survive. The term dead zone is oftenused in reference to the absence of life (other than bacteria) from habitats that are devoid of oxygen. The inability to escape low oxygen areasmakes immobile species, such as oysters andmussels, particularly vulnerable to hypoxia. Theseorganisms can become stressed and may die due tohypoxia, resulting in signi cant impacts on marinefood webs and the economy. Mobile organismscan ee the affected area when dissolved oxygen

becomes too low. Nevertheless, sh kills can resultfrom hypoxia, especially when the concentrationof dissolved oxygen drops rapidly. New researchis clarifying when hypoxia will cause sh kills asopposed to triggering avoidance behavior by sh.Further, new studies are better illustrating howhabitat loss associated with hypoxia avoidancecan impose ecological and economic costs, suchas reduced growth in commercially harvestedspecies and loss of biodiversity, habitat, and

biomass. Transient or diel-cycling hypoxia,where conditions cycle from supersaturation of oxygen late in the afternoon to hypoxia or anoxia

near dawn, most often occurs in shallow, eutrophicsystems (e.g., nursery ground habitats) and mayhave pervasive impacts on living resources becauseof both its location and frequency of occurrence.

Although coastal hypoxia can be caused bynatural processes, a dramatic increase in thenumber of U.S. waters developing hypoxia is

linked to eutrophication due to nutrient (nitrogenand phosphorus) and organic matter enrichmentresulting from human activities. Sources of enrichment include point source dischargesof wastewaters, nonpoint source atmosphericdeposition, and nonpoint source runoff fromcroplands, lands used for animal agriculture,and urban and suburban areas. The incidence of hypoxia has increased ten-fold globally in the past50 years and almost thirty-fold in the United Statessince 1960, with more than 300 systems recentlyexperiencing hypoxia (Diaz & Rosenberg 2008;Table 1 and Appendix III).

Diffuse runoff from nonpoint sources, suchas agriculture elds, can be dif cult to control,although improved production methods that

reduce tillage, optimize fertilizer application,and buffer elds from waterways can mitigatewater quality impairments. Despite the use of improved production methods in recent years,agriculture is still a leading source of nutrient

pollution in many watersheds due, in part, tothe high demand for nitrogen-intensive crops,

principally corn. Furthermore, drainage practices,including tile drainage, have brought wetlands intocrop production, short-circuited pathways (suchas denitri cation) that could ameliorate nutrientloading, and increased the transport of nitrogeninto waterways. Atmospheric nitrogen depositiondue to fossil fuel combustion has declined in manyareas due to emission controls, but it remains animportant source of diffuse nutrient loading. Thedif culty of reducing nutrient inputs to coastalwaters results from the close association betweennutrient loading and a broad array of humanactivities in watersheds and explains the growth inthe number and size of hypoxic zones.

Unfortunately, hypoxia is not the only stressor impacting coastal ecosystems. Over shing,harmful algal blooms (HABs), toxic contaminants,and physical alteration of coastal habitatsassociated with coastal development are several

problems that co-occur with hypoxia and interactto decrease the ecological health of coastal watersand reduce the ecological services that they can

provide.

ExecutiveSummary


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Scienti c Assessment of Hypoxia in U.S. Coastal Waters2

Executive Summary

Legislative Mandates forAction

The Harmful Algal Bloom and HypoxiaResearch and Control Act (HABHRCA) mandated

creation of this report, which serves as a thoroughupdate to the rst scienti c assessment of hypoxiareleased in 2003. Several other legislativedrivers also in uence how Federal agencieswork on coastal water quality including theClean Water Act; the Food, Conservation, andEnergy Act of 2008 (Farm Bill); the EnergyIndependence and Security Act of 2007; and theCoastal Zone Management Act. Responsibilityfor resolving hypoxia spans several Federalagencies (U.S. Department of Agriculture, U.S.Geological Survey, U.S. Environmental ProtectionAgency, and National Oceanic and AtmosphericAdministration), which oversee research andmanagement/control programs (Appendix I).States play a critical role in monitoring andmanaging hypoxia, but their efforts are notaddressed in detail here because this report wasmandated to focus on Federal efforts.

Adaptive ManagementAdaptive management recognizes that science

should inform management decision-making,

not only as the original questions are posed but as scienti c understanding continues todevelop. Current scienti c understanding of thefactors contributing to hypoxia is derived fromrigorous research that Federal agencies have beenconducting and funding for at least 25 years.Federal hypoxia research has made signi cant

progress in describing and quantifying the causesof hypoxia and reducing uncertainties required tocon dently proceed with an adaptive managementapproach. For example, the ecological mechanismslinking nutrient loading to hypoxia in theChesapeake Bay were quanti ed suf ciently to

justify an initial 40% nutrient reduction goal in themid-1980s; further research and sophistication insimulation models have been used subsequentlyto support three additional rounds of adaptivemanagement leading to more detailed nutrientreduction strategies.

From a national perspective, adaptivemanagement approaches will have to be exibleenough to address differences among ecosystems(e.g., geography, level of watershed development,agricultural in uence, nutrient loading, physicalcirculation of the waterbody) and futurecontingencies as they unfold. For example,it is likely that climate change will affect theincidence of hypoxia in coastal waters. A exiblemanagement approach will enable response toclimate impacts as they are realized. A exibleand meaningful adaptive management strategyfor agricultural productionincluding biofuelsshould be explored in order to ensure thatagricultural products are produced in a manner thatminimizes or prevents water quality impairments.

Reducing hypoxia via nutrient loadingreductions will require a concerted effort by adiverse group of stakeholders. Implementing theseactions will likely require organized programs tomonitor, study, and manage water quality problems.Such programs have already been established for a few coastal waterbodies (e.g., Lake Erie, Gulf of Mexico, Chesapeake Bay, Long Island Sound). Inthe case of other waterbodies where the problemhas just recently been recognized and understood(e.g., Narragansett Bay, Rhode Island; PensacolaBay, Florida), only nascent efforts, if any, are in

place to address it.

Scientists use the box corer to sample sediments withnegligible disturbance. Sediment cores are used to studysediment-oxygen-nutrient dynamics.Photo. L.Jewett, NOAA


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Federal ResearchAccomplishmentsand Opportunities forAdvancement

Understanding and managing hypoxia requiresresearch and management actions to addressentire watersheds and their coastal receivingwaters. This report examines progress in: 1)understanding the dynamics of hypoxia where itoccurs (i.e., in estuaries, coastal waters, and theGreat Lakes); 2) understanding and monitoringnutrient uxes in watersheds; and 3) understandinghow to reduce nutrient transport across thelandscape. Because responsibility for managementof nutrient enrichment in watersheds is shared

across several Federal agencies, coordinationand information-sharing are critical. Presently,interagency collaboration is most extensive andeffective in places where investments in scienti cand management activities have been largest andsustained for the longest period of time (e.g.,Chesapeake Bay).

Responsibility for monitoring dissolved oxygen in most coastal and Great Lakes waterbodies lieswith states or with Federal-state partnerships thatutilize state monitoring programs to track water

quality. For many coastal and Great Lakes waterswhere hypoxia occurs, fairly rigorous methodshave been implemented for measuring dissolvedoxygen and conveying this information to scientistsand the public. However, the two largest hypoxiczones in the United States, located at the mouthof the Mississippi River and on the Oregoncontinental shelf, occur beyond the limits of statewaters and, thus, rely on Federal support for monitoring. Monitoring informs coastal managersabout water quality conditions in the ecosystemsthey oversee, and it helps support the development

and veri cation of ecosystem simulation modelsused to guide management decisions.

Since the last scienti c assessment of hypoxiawas written in 2003, many computer models have

been developed or updated to simulate ecological processes related to hypoxia in estuarine,coastal, and Great Lakes ecosystems and their

watersheds. Sophisticated physical transportmodels, which examine ocean currents and mixing,are increasingly being coupled with water qualitymodels to examine alternatives for managinghypoxia. These models are most effective whenthey re ect a strong scienti c understanding of the processes that control hypoxia development.Relatively simple regression models can also beeffective for testing hypotheses regarding factorsthat control hypoxia, especially as more long-

term data on hypoxia become available. Therelative simplicity of regression analyses has alsomade them useful tools for short-term ecologicalforecasting. Regression analyses have been usedfor annual hypoxia forecasts for the northern Gulf of Mexico and Chesapeake Bay. Ecological boxmodels, which simplify processes into broader geographic resolution, have improved greatlyand have begun to incorporate bioeconomiccomponents for assessing impacts of hypoxia oncommercial and recreational sheries. Advanceshave been particularly dramatic in watershedscience. Watershed models now allow scientists toquantify the contribution of particular geographicregions to nutrients entering a coastal system. Asuite of models connecting sources of nutrientsin watersheds to the development of hypoxiain receiving waters, ideally with quanti eduncertainty, is needed by resource managers to

Researchers retrieve the CTD rosette, used for collectingwater and measuring dissolved oxygen and otheroceanographic parameters, after a sampling pro le iscompleted during rough seas.Photo: L.Jewett, NOAA


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Executive Summary

justify potentially costly actions to reduce nutrientsand hypoxia. Use of a multiple model consensus,where models use different approaches andassumptions, provides one way to better informmanagement decisions. This approach is wellknown for its application to forecasting hurricane

paths and predicting the effects of carbon dioxideuctuations on climate.

Monitoring stream and river flow and theassociated nutrients is critically important for evaluating nutrient sources in the watershed andmodeling uxes to coastal waterbodies. Streamand river monitoring was made more ef cient,maximizing the use of existing resources,through the redesign of the National StreamQuality Accounting Network in 2007. However,

it is important not only to maintain the currentstream ow gauges and water quality monitoringstations, but also to increase the number of streamsmonitored. Similar to hypoxia monitoring, themonitoring of nutrients in rivers and streams isrequired for the development and use of predictivemodels and to determine the cause-effectrelationships between activities that alter water nutrient export and the changes in water quality inthe receiving water. Expanded stream monitoring,in combination with modeling efforts, will allowdesign of effective nutrient reduction strategiesand will improve the ability to track progresstoward water quality goals. Thus, effective andsustained management of hypoxia will requirelong-term support of stream and river water qualitymonitoring programs.

Research exploring hypoxia impacts on fishand invertebrates has shown negative effects ongrowth, reproduction, species composition, andecological interactions among species. However,scaling up these impacts from individuals to entire

sheries populations or ecosystems is extremelycomplex and requires sophisticated ecosystemmodels that are generally beyond the state-of-the-science. Thus, research should be focusedon developing these models and linking them tothose that include more conventional water qualitycomponents. An additional modeling challengewill be resolving the impacts of hypoxia onliving resources in systems affected by a suite of

stressors as we move toward more comprehensiveecosystem management approaches.

Reducing nutrients from anthropogenic sourcescan lead to a reduction in coastal hypoxia andimprovements in water quality throughout thewatershed. Nutrient loads in some systems, suchas Long Island Sound and Narragansett Bay, are

being successfully reduced through targeting of wastewater treatment plants. However, nutrientloads from municipal and industrial facilities,de ned as point sources, are more easily addressedthan the diffuse sources of nutrients enteringwaterways as runoff from agricultural and urbanlands.

Signi cant Federal investments and scienti ceffort have focused on developing ef cient andeffective ways to reduce nutrient runoff, includingland conservation programs (which provideincentives for farmers to take marginal agriculturalland out of production, invest in working landsto reduce erosion and control nutrients, and re-establish wetlands), alternative drainage systems,remote sensing to target fertilizer applications,winter cover crops, and newly formulatedfertilizers.

Unfortunately, measures implemented onnonpoint sources to date have proven ineffectiveat reducing nutrient loads from large watershedsto levels needed to signi cantly reduce hypoxiczones. For example, reductions in total springnitrogen loads to the Gulf of Mexico from 2001-2005 were primarily from forms of nitrogenother than nitrate, which is a critical form fuelingspring primary production leading to hypoxia.This highlights the importance of the nutrientcomposition, as well as seasonality, for reductiontargets. Further, evidence suggests that someecosystems may not respond as expected to nutrient

management as they become nutrient saturated.Thus, major new initiatives should include rigorousscienti c evaluation of the effectiveness of existingnutrient reduction strategies through local analysesof downstream water quality so that strategiescan be re ned accordingly. Continued researchis also needed on new practices, such as thosethat enhance natural nutrient processes through


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Executive Summary

reforestation, river diversions into wetlands, andvegetation buffer systems for streams and rivers.Such research has already led to managementdecisions to protect wetlands and to reforest

portions of watersheds.

Establishment of criteria for acceptable nutrientlevels in both coastal areas and in rivers upstreamfrom hypoxic zones is also a critical tool for designing management plans. These criteria canalso be used to measure progress.

ConclusionHypoxia is a major contributor to the decline of

coastal water quality observed in recent decades,and its extent has been expanding. It is part of the

broader issue of nutrient-driven eutrophication.Eutrophication is also linked to increased HABs,loss of seagrasses, and other impacts on coastalecosystems. For eutrophic ecosystems, concertedand coupled research and management efforts,along with stakeholder support, will be needed

to rigorously identify, quantify, and implementnutrient reduction strategies that are effective andachievable. Furthermore, for systems such as theOregon shelf where hypoxia is driven primarily bynatural processes linked to variations in climate,improved scienti c understanding will provideinsight into future impacts of climate change onsimilar ecosystems. Moreover, knowledge gainedwill be important for developing forecasts of the extent and severity of low dissolved oxygen,which will help managers mitigate the impacts of hypoxia.

If properly planned and executed, adaptivemanagement of nutrient inputs will lead tosigni cant reductions in hypoxia. However, if current practices are continued, the expansion

of hypoxia in coastal waters will continue andincrease in severity, leading to further impacts onmarine habitats, living resources, economies, andcoastal communities.

Sunset aboard EPAs Ocean Survey Vessel Peter W. Anderson during a research cruise in the Gulf of Mexico hypoxic zone. Photo: EPA


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LegislativeBackground, Report Overview,and Development Process

Chapter 1

1.1. Legislative BackgroundIn the early 1980s, concern about low dissolved

oxygen in coastal waterbodies of the United Statesled to the rst national assessment of coastalhypoxia (Whitledge 1985), which found dissolvedoxygen levels in many U.S. waterbodies on the

decline as a result of eutrophication. By the 1990s,serious and large-scale water quality problems wereidenti ed, including harmful algal blooms (HABs)and hypoxia, most prominently in the northern Gulf of Mexico, Lake Erie, Chesapeake Bay, and LongIsland Sound. These problems led to a nationalassessment of eutrophication in 1999 (Bricker et al.1999), which was subsequently updated (Bricker etal. 2007), and an integrated assessment of hypoxiain the northern Gulf of Mexico (CENR 2000, U.S.EPA 2007), as well as the passage of the HarmfulAlgal Bloom and Hypoxia Research and ControlAct of 1998 (HABHRCA, Public Law 105-383).

HABHRCA was reauthorized by the HarmfulAlgal Bloom and Hypoxia Amendments Act of 2004 (HABHRCA 2004, Public Law 108-456).HABHRCA 2004 reconstituted the InteragencyTask Force on HABs and Hypoxia. To ful llthe requirements of both HABHRCA 2004 andthe Oceans and Human Health Act of 2004, theInteragency Task Force on HABs and Hypoxia wasincorporated into the Interagency Working Groupon HABs, Hypoxia, and Human Health (IWG-4H, see page iii) of the Joint Subcommittee onOcean Science and Technology. HABHRCA 2004required ve reports to assess and recommendresearch programs on HABs and hypoxia inU.S. waters, including this report, a Scienti c Assessment of Hypoxia in U.S. Coastal Waters (Box 1). HABHRCA 2004 stipulates that thisreport should:

examine the causes, ecological consequences,and economic costs of hypoxia;

describe the potential ecological and economiccosts and bene ts of possible actions for

preventing, controlling, and mitigating hypoxia; evaluate progress made by and needs of Federal

research programs; and identify ways to improve coordination among

Federal agencies with respect to research onhypoxia.

HABHRCA 2004 also authorizes appropriationsto the Secretary of Commerce and the NationalOceanic and Atmospheric Administration (NOAA)to conduct research on hypoxia.

Additional legislation affecting Federalresearch on hypoxia or factors that may affecthypoxia is listed in Box 2. The Coastal ZoneAct Reauthorization Amendments of 1990

reauthorized the Coastal Zone Management Act

Box 1. HABHRCA 2004 Reports andAssessments

Harmful Algal Bloom Management andResponse: Assessment and Plan National Assessment of Efforts to Predict and

Respond to Harmful Algal Blooms in U.S. Waters(Prediction and Response Report)

Report on National Scienti c Research,Development, Demonstration, and TechnologyTransfer Plan for reducing HAB Impacts (RDDTTPlan)

Scienti c Assessment of Freshwater HarmfulAlgal Blooms

Scienti c Assessment of Marine Harmful AlgalBlooms

Scientific Assessment of Hypoxia in U.S.Coastal Waters


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Chapter 1

and established a joint program between the U.S.Environmental Protection Agency (EPA) and the

states to develop and implement coastal nonpoint pollution management programs. We note thatEPAs Mississippi River Basin program will beenhanced in 2011, pending enactment of thePresidents proposed budget. The Water ResourcesDevelopment Act authorizes ood control,navigation, and environmental projects and studies

by the U.S. Army Corps of Engineers (USACE),and it states that the Secretary of the Army may

participate in assessments of hypoxia in thenorthern Gulf of Mexico. Some of this legislationfocuses on water quality in upland watersheds,which ultimately may affect the quality of water delivered to coastal ecosystems; therefore, it alsoimpacts coastal hypoxia. The Clean Water Actaims to restore and maintain the chemical, physical,and biological integrity of the Nations waters byreducing point and nonpoint pollution sources,

providing assistance to publicly owned treatmentworks for improving wastewater treatment,and maintaining the integrity of wetlands. TheFood, Conservation, and Energy Act of 2008 (theFarm Bill) authorized $25 billion to support

conservation programs administered by the U.S.Department of Agriculture (USDA) through its Natural Resources Conservation Service (NRCS)and Farm Service Agency (FSA). Finally, theEnergy Independence and Security Act (EISA) of 2007 potentially has far-reaching environmentalimplications. The bill mandates production of 36 billion gallons of biofuels by the year 2022,

including 15 billion gallons of corn-based ethanol.The legislation designates the EPA, USDA,and U.S. Department of Energy (DOE) as leadagencies in an interagency effort to develop criteriafor sustainable development of biofuels, whichinclude prevention of water quality and ecosystemimpairments.

1.2. Report OverviewThis assessment focuses on the science that

forms the basis for improving knowledge of thecauses, impacts, and solutions for hypoxia incoastal ecosystems of the United States as of 2009.This report has four chapters and three appendices:

Chapter 1: Legislative background, reportoverview, and report development process;

Chapter 2:The current status of hypoxia in U.S.coastal waters, the spectrum of causal factorscontributing to hypoxia, and the ecological andeconomic consequences of hypoxia;

Chapter 3: Status and accomplishments of current Federal monitoring, assessment, andresearch activities related to hypoxia, includingresearch on coastal ecosystems and their watersheds that provides the basis for effectivemanagement actions;

Chapter 4: Directions for future science activitiesand opportunities to increase effectiveness andcost-ef ciency through coordination of programsacross Federal agencies;

Appendix I: Federal Government Hypoxia or Hypoxia-related Research;

Appendix II: Case studies that feature coastalecosystems across the United States affected

by hypoxia. The featured systems wereselected to illustrate the range of circumstancescausing hypoxia as well as the range in statusof scienti c understanding and managementapproaches being implemented (the case studiesare referenced throughout the report); and

Appendix III: Details on U.S. coastal systems

affected by hypoxia.

1.3. The ReportDevelopment Process

This report was prepared by a task forceassociated with the IWG-4H that includedrepresentatives of Federal agencies participatingin the science and management of coastal hypoxia.

Box 2. Legislation Relevant toHypoxia

Harmful Algal Bloom and Hypoxia Researchand Control Act

Coastal Zone Management Act Water Resources Development Act Clean Water Act Food, Conservation, and Energy Act of 2008 Energy Independence and Security Act of

2007 Annual appropriations of Federal agencies


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Legislative Background and Report Process

It builds on earlier reports to assess hypoxia inU.S. coastal waters by updating the assessmentsand summarizing the major advances in hypoxiaresearch during the past ve years. Speci cally,this report draws on An Assessment of Coastal Hypoxia and Eutrophication in U.S. Waters (CENR 2003), which was called for in HABHRCA1998. This report also recommends priorities for future hypoxia-related research across the U.S.government.


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2.1. The Issue of Hypoxia

Hypoxia, or water with dissolved oxygenthat is too low to support sh and other important species (Box 3), has been recognized asone of the most important water quality problemsworldwide (Diaz and Rosenberg 2008). Hypoxiahas become a serious problem along all of the

Nations coasts and in the Great Lakes. Hypoxic

areas are often termed dead zones since theonly organisms that thrive there are those that canlive with little or no oxygen, often only bacteria.Most mobile organisms are able to avoid hypoxicwaters by swimming or crawling away; organismsunable to move or those trapped within a zoneof hypoxia become physiologically stressed anddie if exposure is prolonged or severe (Diaz andRosenberg 1995, Vaquer-Sunyer and Duarte 2008).

Most coastal hypoxia is associated at the globalscale with either areas of high population density

or developed watersheds thatexport large quantities of nutrients and organic matter (Figure 1, Rabalais et al. 2007,Galloway et al. 2008, Diaz andRosenberg 2008). The number of waterbodies with recordedand published accounts of low dissolved oxygen fromaround the globe has increasedabout an order of magnitudeduring the last 50 years, fromless than 50 in the 1960s toabout 400 by 2008 (Diazand Rosenberg 2008). Thenumber of waterbodies in theUnited States with documentedhypoxia followed the sametrend, increasing from 12 prior

Causes and Status of Hypoxia in U.S. Coastal Waters

Chapter 2

to 1960 to over 300 by 2008 (Appendix III; Figure2).

The second largest eutrophication-relatedhypoxic area in the world (after the Baltic Sea,which is approximately 80,000 square kilometers,or km 2, Karlson et al. 2002, Hansen et al. 2007)occurs in the United States, and is associated withthe discharge from the Mississippi/Atchafalaya

Rivers in the northern Gulf of Mexico. The Gulf of Mexico hypoxic area is similar in extent andvolume to another large hypoxic area associatedwith Chinas Changjiang River out ow (13,700km2 in 1999, Li et al. 2002). The northern Gulf of Mexico hypoxic area has increased substantiallyin size since the mid-1980s when it was rstmeasured at about 4,000 km 2 (Rabalais et al. 2007).In 2008, it encompassed 20,719 km 2, the secondlargest area on record ( http://www.gulfhypoxia.net/). A concerted Federal interagency and multi-

Box 3. HypoxiaDe nition

Hypoxia means low oxygen.In aquatic and marine systems,low oxygen generally refers to adissolved oxygen concentration lessthan 2 to 3 milligrams of oxygen per liter of water (mg/L), but sensitiveorganisms can be affected at higherthresholds (4.5 mg/L). A completelack of oxygen is called anoxia.

Hypoxic waters generally do nothave enough oxygen to support

sh and other aquatic animals, andare sometimes called dead zonesbecause the only organisms thatcan live there are microbes. Thecriteria set for health of variousspecies in Chesapeake Bay are agood example of how one de nitionfor hypoxia is not possible (EPA2003).
http://www.gulfhypoxia.net/http://www.gulfhypoxia.net/http://www.gulfhypoxia.net/http://www.gulfhypoxia.net/


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The Problem of Hypoxia in U.S. Waters

sources of pollutants. It was in the 1970s thatthe rising effects of nonpoint runoff of nutrientswere observed in water quality deteriorationaround the United States (Smith et al. 1987). The

1970s were also when rst reports of hypoxiaappeared for our larger coastal systems (northernGulf of Mexico, New York Bight, Long IslandSound). By the 1980s, it became apparent thatincreasing nutrient loads from nonpoint sourceswere responsible for an expansion of eutrophicconditions in estuarine and coastal systems withinthe United States (reviewed by Bricker et al.1999, 2007). Overall, the United States has led aglobal trend in which agricultural fertilizers are theleading nonpoint source of nutrient pollution, butatmospheric deposition from burning of fossil fuels

and nitrogen xation associated with legume cropsalso contribute signi cantly (Howarth et al. 1996).The primary sources of nutrient pollution varysubstantially among watersheds (e.g., Figure 3),complicating the task of nutrient management.

A current analysis of 647 U.S. coastal andestuarine ecosystems indicates that the percentageof systems with hypoxia has increased dramaticallysince the 1960s (Figure 2) and even since the 1980s(Table 1). The rst national assessment of oxygenconditions in U.S. waters, conducted in the 1980s,

found 38% of systems to have hypoxia (Whitledge1985). Subsequent eutrophication assessmentsfound greater than 50% of systems to have hypoxia(Bricker et al. 1996, 1997a, 1997b, 1998a, 1998b,2007). Updating the information from all thesesources nds that 307 of 647 ecosystems havehypoxia (Appendix III). Most of the increasessince the 1980s occurred in the North Atlantic,

South Atlantic, and Paci c regions and re ectan increase in the incidence of hypoxia. In theMiddle Atlantic and Gulf of Mexico regions, the

percentage of hypoxic systems was already high

in the 1980s and remains high to date. Further,the third National Coastal Condition Report (U.S.EPA 2008) found water quality for Atlantic andGulf coasts to range from fair to poor, based ondata from the early 2000s. For the Great Lakes,there appears to have been little change in hypoxicconditions since the 1980s.

Dissolved oxygen conditions have improvedin some waterbodies due to intensive regulationof nutrient or carbon inputs, primarily from moreadvanced sewage and industrial treatment. The

best examples are from smaller systems where point source discharges were the primary sourceof organic matter and nutrients, such as theHudson River in New York and the DelawareRiver in Pennsylvania and New Jersey (Brosnanand OShea, 1996; Patrick, 1988). In larger systems where point sources have been intenselymanaged, dissolved oxygen conditions have notimproved because of large nonpoint sources of nutrients. Examples include Chesapeake Bayand Lake Erie, which have a long history of nutrient management but continuing problems

with large-scale hypoxia. (See Appendix II).Even with improved management of nonpointsources, recovery of some large systems may

be delayed due to nutrient and organic matter that have accumulated in the sediments over theyears, thereby increasing oxygen demand, and,in turn, expanding the amount of hypoxia for agiven load of nutrients (Turner et al. 2008). This

Region % Hypoxic 1980s 1 % Hypoxic 1990s 2 % Hypoxic 2000s 3 % Hypoxic 2000s 4

North Atlantic 6 (1 of 17) 22 (4 of 18) 35 (7 of 20) 26 (10 of 38)

Mid-Atlantic 50 (19 of 38) 59 (13 of 22) 64 (14 of 22) 42 (76 of 180)

South Atlantic 18 (9 of 51) 64 (14 of 22) 91 (20 of 22) 55 (77 of 139)Gulf of Mexico 69 (38 of 55) 84 (32 of 38) 68 (26 of 38) 51 (105 of 205)

Paci c 21 (6 of 29) 26 (10 of 39) 35 (13 of 37) 46 (37 of 80)

Great Lakes 1 of 5 lakes 2 of 5 lakes 2 of 5 lakes

Total Nation 38 (73 of 190) 52 (73 of 139) 58 (80 of 139) 47 (307 of 647)1 Based on Whitledge 1985a; 2 Based on Bricker et al. 1996, 1997a, 1997b, 1998a, 1998b; 3 Based on Bricker et al. 2007; 4 FromAppendix III.

Table 1. Percentage of U.S. estuaries and coastal waterbodies with reports of hypoxia.


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Chapter 2

may be the case in the northern Gulf of Mexicoand Chesapeake Bay (Hagy et al. 2004, Turner etal. 2008). Unfortunately, nutrient loading fromagricultural and atmospheric sources is predicted toincrease globally over the next 50 years (Tilman etal. 2001, Galloway et al. 2008), creating additionalstress on coastal waterbodies already in decline.Federal research and management actions mustaccelerate the pace of water quality management inorder to protect and restore valued coastal aquaticresources.

2.3. Causes of HypoxiaWidespread and persistent hypoxia is generally

not a natural condition in estuaries, coastal waters,or large lakes like the Great Lakes, with Lake

Erie being an exception (Appendix II). However,naturally occurring oxygen depletion does occur,as in oceanic oxygen minimum zones, fjords,some strati ed seas (e.g., the Black Sea), lakes and

ponds, and swamps and backwaters that circulate poorly and have large loads of natural land-derivedorganic matter. Naturally occurring hypoxia isnot the focus of this report, but it is important toconsider these cases because human activities mayincrease the frequency, duration, and intensity of naturally occurring hypoxia (Cooper and Brush

1991, Helly and Levin 2004, Diaz and Rosenberg2008).

When the rate of oxygen consumption inaquatic environments increases such that theoxygen consumption rate exceeds resupply,oxygen concentrations can quickly declineto levels insuf cient to sustain most animallife. Two conditions are generally required for the development and maintenance of hypoxia(Figure 4): water column strati cation that isolates a layer

of bottom water and sediments from a usuallywell-oxygenated surface layer (see Section2.3.1), and

a source of organic matter, which is thendecomposed and depletes oxygen in the isolated

bottom layer (see Section 2.3.2).Diel-cycling hypoxia, where conditions can

cycle from supersaturation of oxygen late in theafternoon to hypoxia or anoxia near dawn, is aunique situation that does not require the rstcondition described above. This phenomenoncan occur in unstrati ed waters and appears to beincreasing in frequency (DAvanzo and Kremer 1994, Verity et al. 2006, Shen et al. 2008). It mostoften occurs in shallow, eutrophic tidal creekswhere oxygen exchange at the water surface

Figure 2. Change in number of U.S. coastal areas experiencing hypoxia from 12 documented areas in 1960 to over 300now (Appendix III). Not shown here are one hypoxic system in Alaska and one in Hawaii.


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is insuf cient to supply the respiratory needsof microbes and other organisms. This type of transient or diel hypoxia may cause pervasiveimpacts on living resources both because of thefrequency with which it occurs (hours to days)and its location (small and shallow nursery groundhabitats, e.g., Pepper Creek, Delaware; Tyler andTargett 2007, Tyler et al. 2008). The increased

production of organic matter within a system,mostly in the form of phytoplankton productivityin response to anthropogenic nutrient pollution,contributes to both seasonal and diel-cyclinghypoxia in coastal ecosystems. In shallow systemsthat are highly eutrophic, calm weather conditionsand extended periods of cloud cover can cause lowdissolved oxygen events (Tyler et al. 2008).

Whereas physical factors create the physicalconditions that are usually necessary for hypoxiato develop in bottom waters, nutrient-driveneutrophication provides the increased deposition of decomposing organic matter to the bottom layer,creating increased oxygen demand. Although

physical factors can change over the long-term,they have not in most cases (e.g., Hagy et al.2004, Greene et al. 2009). Thus, eutrophication isthe principal cause of the long-term increases inhypoxia that have been observed.

2.3.1. Physical FactorsDensity strati cation of the water column, in

which a less dense layer of water oats on topof a denser bottom layer, is an almost universalcharacteristic of coastal systems subject to seasonal

bottom water hypoxia. Strati cation reducesthe potential for oxygen from the atmosphere toreplenish oxygen depleted at depth. In most cases

involving marine systems, a vertical gradient of salinity, creating a halocline, is the most importantfactor contributing to density strati cation.Surface heating, creating warmer surface water temperatures and thus a vertical gradient of temperature, or a thermocline, is the cause of strati cation in lakes and can also contribute todensity strati cation in marine systems, especiallyduring spring when deeper waters are relativelycold. Thermal strati cation creates the potentialfor hypoxia in Lake Erie and is also known to beimportant in Long Island Sound and New York Bight (Boesch and Rabalais 1991, Hawley et al. 2005, Lee and Lwiza 2008). In the fall, coolingtemperatures and decreasing freshwater inputscan destabilize summer strati cation, leading torelatively abrupt mixing or turnover of the water column that eliminates seasonal hypoxia. Fallturnover is often associated with a wind event suchas a storm or frontal passage.

Urban/Suburban

Agriculture

Atmospheric

Urban/Suburban

Agriculture

Atmospheric

Urban/Suburban

Agriculture

Atmospheric

Urban/Suburban

Agriculture

Atmospheric

Agriculture

Atmospheric

Urban/Suburban

Pasture

Agriculture

Atmospheric

Urban/Suburban

Pasture

Figure 3. Comparison of the relative contribution of major sources of nitrogen pollution in three coastal ecosystemsexperiencing hypoxia. Urban/suburban includes both point (industrial and sewage ef uent) and nonpoint sources (residential runoff). Data sources: Chesapeake Bay: Chesapeake Bay Program; Narragansett Bay: Nixon et al. 2008, Moore et al. 2004; Gulf of Mexico: Alexander et al. 2008.

Chesapeake Bay Narragansett Bay Gulf of Mexico


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Chapter 2

In river-dominated estuaries and ocean margins,density strati cation and other circulation featuresare strongly affected by the amount of less densefreshwater owing out of associated rivers.Therefore, the extent and severity of seasonalhypoxia varies on an annual basis in relation tothe magnitude of freshwater inputs. In larger systems, where freshwater is retained in the systemfor longer periods of time, summer hypoxia isusually coupled most closely to freshwater inputsduring spring, when spring rains or snow meltcause high freshwater ow (e.g., ChesapeakeBay, Hagy et al. 2004; northern Gulf of Mexico,Greene et al. 2009). In smaller systems, physicalconditions conducive to development of hypoxiamay be coupled to freshwater inputs on a shorter time scale. For example, a single early fall pulseof freshwater associated with Hurricane Ivanstimulated development of an unseasonable period

of hypoxia in Pensacola Bay, Florida, duringfall 2004 (Hagy et al. 2006). Shen et al. (2008)observed periods of hypoxia lasting two to vedays in a shallow mid-Atlantic creek following arain event.

Development and maintenance of hypoxia arestrongly affected by water column mixing. Strongtidal mixing prevents water column strati cationalmost entirely in some systems. Where tides arenot as strong, low dissolved oxygen events may

occur during neap tides, the phase of the spring-neap tidal cycle when tidal mixing is minimal(Haas 1977). Strati cation, and thus vulnerabilityto hypoxia, is reduced during the larger springtides, which are associated with full and newmoons, when tidal currents are stronger andgenerate increased mixing of the water column.Some estuaries, such as Mobile Bay, Alabama,

Figure 4. Conceptual diagram illustrating development and effects of hypoxia in stratified waters (from Downing et al.1999). The pycnocline is the boundary that strati es and separates the bottom and surface water layers.


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and Pensacola Bay, Florida, in the northeasternGulf of Mexico have low amplitude tides (Hagyand Murrell 2007), and others, such as theAlbermarle-Pamlico Estuarine System on the NorthCarolina coast, are virtually tideless (Luettichet al. 2002). These estuaries, which are also ina warmer climate that yields higher respirationand nutrient regeneration rates, are particularlysusceptible to strati cation and hypoxia. Wind isan especially important factor affecting hypoxia inthese microtidal estuaries (Reynolds-Fleming andLuettich 2004, Park et al. 2007, Hagy and Murrell2007).

2.3.2. Biological/chemical FactorsEutrophication , fundamentally a biological

and biogeochemical process, is an importantfactor and indeed the principal cause of coastalhypoxia. In an update to the National Estuarine Eutrophication Assessment (Bricker et al. 2007,See Table I), eutrophication was recognized as awidespread problem, with 65% of assessed systems(99 of 141 systems had adequate data for analysis)showing moderate- to high-level problems. Themost commonly reported eutrophication-related

problems included hypoxia, losses of submergedgrasses, excessive algal blooms (the mostcommonly reported problem), and numerous

occurrences of nuisance and toxic HABs. The mid-Atlantic was identi ed as the region most impacted

by eutrophication. The majority (almost 60%) of estuaries assessed, with the exception of NorthAtlantic systems (Cape Cod north to Maine), werehighly in uenced by human-related activities thatcontributed to land-based sources of nutrient loads.The most commonly reported causes of nutrient-related impairments were agricultural activities(row crops and livestock operations), wastewater treatment plants, urban runoff, and atmosphericdeposition. Eutrophication-related problems were

predicted to worsen in 65% of estuaries, whereas19% of the assessed estuaries were expected toimprove in the future. Analysis of the extentof change in 58 estuaries from the early 1990sto the early 2000s shows that most (55%) wereunchanged, including all of the larger estuaries.

The principal sources of nutrients that sustaincoastal eutrophication vary among systems. Wheresigni cant rivers enter the coastal zone, nutrientloads associated with the freshwater discharge areusually the predominant source. Coastal systemslacking substantial riverine inputs may receive asubstantial fraction of nutrient inputs via submarinegroundwater discharge or direct atmosphericdeposition, as in Barnegat Bay, New Jersey(Kennish et al. 2007). The major anthropogenicsources of nutrients to coastal waters are rowcrop agriculture and animal operations, industrialand municipal wastewater discharges, nonpointsource runoff from urban and suburban areas,and atmospheric deposition (Figure 3). Humanactivities have been linked to a dramatic increasein nitrogen cycling in the natural environment.Watersheds can become nitrogen-saturated,for example, when further additions of nitrogendo not elicit a response from the ecosystem. Innitrogen-saturated watersheds, the surplus nitrogenwill theoretically leak to streams, groundwater,or the atmosphere (Vitousek et al. 1997). Loss or degradation of riverine and coastal wetlands canalso contribute to eutrophication of coastal waters

because wetlands naturally trap and retain nutrients(e.g., Valiela and Cole 2002).

In most cases, eutrophication has been caused by an anthropogenic increase in nutrient inputs. Ina few cases, large but, nonetheless, natural sourcesof nutrients have been implicated in sustaininghigh primary productivity in coastal systems. For example, some watersheds in southwest Floridahave naturally high concentrations of phosphatesthat can support high levels of primary production(Turner et al. 2006a). Natural upwelling of nutrient-rich deep ocean water into shallow areasalso can support large blooms of phytoplankton(Glenn et al. 1996, Chan et al. 2008) and can

result in hypoxia. Upwelling of nutrient-richwaters has been implicated in the development of severe widespread hypoxia and, for the rst time(in 2006), anoxia on Oregons inner continentalshelf (Grantham et al. 2004, Chan et al. 2008).Transport of hypoxic water from the continentalshelf into coastal embayments has also beendocumented along the Oregon coast (Brown


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Chapter 2

et al. 2007). These developments seem to belinked to impacts of climate variation on ocean

processes, such as intensity of upwelling winds,oxygen concentration in upwelled water, andwater column respiration (Grantham et al. 2004,Chan et al. 2008). More subtle upwelling has

been observed along the New Jersey coast andhas been implicated in development of nearshorehypoxia (Glenn et al. 1996, 2004). Both of thesecases, however, contrast with the situation for mostcoastal areas undergoing eutrophication, where thesource of increased nutrient input is land-based andattributable to anthropogenic causes.

Hypoxia can be related in some cases todocumented long-term increases in algal

biomass. For example, the long-term increase in

chlorophyll- a (a proxy for phytoplankton biomass)in the Chesapeake Bay, as documented by Hardingand Perry (1997), was concurrent with the increasein hypoxia documented by Hagy et al. (2004). Ina few cases, hypoxic events have been related tohigh biomass HABs. For example, the one-timehypoxic event in the New York Bight (Garlo et al.1979, Boesch and Rabalais 1991) and hypoxia inthe Peace River-Charlotte Harbor system (Turner etal. 2006a) were both related to high biomass algal

blooms. Further, massive mortalities of bottom-dwelling organisms were associated with thecascading effects of algal toxicity, hypoxia, anoxia,and hydrogen sul de poisoning during a toxic HABevent in Florida in 2005 (Landsberg et al. 2009).

2.4. Consequences of Hypoxia2.4.1. Ecological Consequences

Ecological effects of hypoxia in coastal systemscan vary in both degree and scale (Figure 5). Thespeci c concentration of dissolved oxygen below

which various animals suffocate varies, but for estuarine and marine species, effects generallyappear when oxygen drops below about 3 mg/L(Diaz and Rosenberg 1995, Ritter and Montagna1999, Rabalais et al. 2001, Breitburg et al. 2001,Karlson et al. 2002). However, the behavior of some organisms (e.g., sh, larvae) can benegatively affected at oxygen concentrations as

high as 4-4.5 mg/L (Whitmore et al . 1960, Kramer 1987, Breitburg 1994). Toxic hydrogen sul deis often present in waters nearly or completelydevoid of oxygen and signi cantly reduces survival(Gamenick et al. 1996).

Fish kills are an obvious and very unpleasantconsequence of hypoxia. The frequency andmagnitude of sh kills have increased as nutrient-related eutrophication has worsened both hypoxiaand HABs (Thurston 2002, Thronson and Quigg2008). Fish kills related to hypoxia have beennoted in waterbodies on all U.S. coasts, but theincidence of sh kills does not capture the extentof hypoxia impacts. Fish kills are much lesswidespread than hypoxia itself and sometimesoccur only when several factors are present along

with hypoxia (e.g., HABs as in Corsica River,Maryland, Bricker et al. 2007) or when hypoxiadevelops in a way that prevents sh from escaping.Other effects of hypoxia are less obvious, butmore pervasive and likely more important overall.These include shifts in spatial distribution of organisms, changes in community structure caused

by emigration of sh and mobile invertebrates,

Figure 5. The range of ecological impacts exhibited asdissolved oxygen levels drop from saturation to anoxia(based on Diaz and Rosenberg 1995, Rabalais et al. 2001).


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mortality of sessile (immobile) bottom-dwelling organisms,and alteration or blockage of normal migration routes of

sh and invertebrates.

Hypoxic habitats that areavoided by organisms arefunctionally lost from thesystem (Breitburg 2002,Rabalais and Turner 2001,Sagasti et al. 2001). Becauseoxygen thresholds for avoidance are usually higher than for survival (Figure 5),habitat loss due to hypoxiais far greater than would be

suggested by calculations based on recruitmentor survival tolerances. Changes in communitystructure and habitat loss associated with hypoxiacan also propagate to other components of the foodweb. For example, impacts to animals that act ascrucial food web linkages between algal producersand top predators (e.g., benthic suspension feeders)result in a decreased ow of energy to predatorsand an increase to microbes (Figure 6, Diaz andRosenberg 2008). Avoidance of hypoxia can alsoreduce energy ow to predators. Hypoxia cancause reduced growth (Taylor and Miller 2001),lower reproduction (Marcus et al. 2004), and other

physiological effects (Wu et al. 2003). Shrimpand crabs exposed to hypoxia, for example,

become immunocompromised and may suffer increased susceptibility to disease and mortalityfrom bacterial infections (Le Moullac et al. 1998,Holman et al. 2004, Burgents et al. 2005; Tanner etal. 2006).

Hypoxia has contributed to the collapse or impairment of a number of commercially important

sheries worldwide, including Norway lobster in the Kattegat Sea (Baden et al. 1990) and

bottom-dwelling sh in the Baltic and Black Seas(Breitburg et al. 2001, Mee 2006). Effectivelyseparating impacts of hypoxia on exploited shery

populations from those due to over shing can bechallenging (Breitburg et al. 2009). Most likely,the effect of hypoxia is to decrease productivityand resilience of exploited populations, making

them more vulnerable to collapse in the face of heavy shing pressure.

The ecological impacts of hypoxia may beunderstood in terms of the ecosystem servicesnormally provided by a healthy ecosystem, but lostas a result of hypoxia (Table 2). A full assessmentof ecosystem services lost helps bridge the gap

between ecological functions lost and their impacton people. In some cases, though not withoutchallenges, ecosystem services can be assigned areasonable dollar value. In these cases, analysisof services helps convey the economic costsassociated with ecological impacts.

Fisheries yield is one ecosystem service thatcan be impacted both directly and indirectly byhypoxia. Mortality of sheries species is a directmechanism by which services are lost. Loss of forage for bottom-feeding sh and shell sh due tohypoxia is probably more important in most casesand also amounts to a loss of ecosystem services.In the Chesapeake Bay, seasonal hypoxia lastsabout three months and reduces the Bays total

benthic secondary production by about 5% (Diazand Schaffner 1990), or roughly 75,000 metrictons of biomass (Diaz and Rosenberg 2008). Thisis enough to feed about half the annual blue crabcatch for a year. In the northern Gulf of Mexico,severe seasonal hypoxia can last up to six monthsand reduces benthic biomass by about 212,000metric tons when the hypoxic zone is 20,000 km 2 (Rabalais et al. 2001). This lost biomass could

Figure 6. Conceptual view of how hypoxia alters ecosystem energy flow withexample systems (modified from Diaz and Rosenberg 2008).


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Chapter 2

feed about 75% of the brown shrimp catch for aseason (Diaz and Rosenberg 2008). It is unknownwhether these systems can recover secondary

production lost to hypoxia during periods withnormal oxygen levels. The Chesapeake Bay hasa recovery period of approximately nine months,whereas the northern Gulf of Mexico requires sixmonths for recovery of the lost benthic production.Well-oxygenated conditions outside of summer,however, may be inadequate to support recovery

since many other growth requirements (especiallyappropriate water temperatures) are optimal in thesummer.

One of the less obvious ecosystem services lostduring hypoxia is sediment mixing by benthicorganisms, or bioturbation. Reworking of sediments via bioturbation promotes oxygenationof sediments, improving habitat for benthic

animals and promoting biogeochemical feedback processes that reduce nutrient recycling andlimit eutrophication. In particular, bioturbation

promotes coupled nitri cation and denitri cation,which eliminates excess bioavailable nitrogen fromthe ecosystem. Loss of these services amounts toadditional nitrogen loading, which must be offset

by additional controls on inputs (Hagy et al. 2004).When bioturbation is eliminated due to hypoxia,nitrogen is returned to the water as bioavailable

ammonium, often with phosphorus as well,reinforcing a cycle of eutrophication (Aller 1994,Kemp et al. 2005).

Determining the ecological consequences of hypoxia on ecosystem services (Table 2) is oftencomplicated by cumulative and interacting impactsinvolving a variety of stressors. Quanti cation of the relationship between hypoxia and impacts on

Impacts on Ecosystem Services Example ReferenceLoss of biomass

Direct mortality of sheries species Long Bay Koep er et al. 2007Direct mortality of prey species Northern Gulf of Mexico Rabalais et al. 2001Reduced growth and production Chesapeake Bay Diaz and Schaffner 1990

Reduced recruitment Patuxent River Breitburg 1992

Loss of biodiversity

Elimination of sensitive species Pensacola Bay Hagy et al. 2006Reduced diversity Pamlico River Tenore 1972Increased susceptibility to disease and other stressors St. Johns River Mason 1998Lower food web complexity Neuse River Estuary Baird et al. 2004

Loss of habitat Crowding of organisms into suboptimal habitats Neuse River Estuary Eby et al. 2005Increased predation risks (both natural and shing) Northern Gulf of Mexico Craig and Crowder 2005

Forced migration from preferred habitat St. Josephs Bay Leonard and McClintock 1999Altered or blocked migration routes New York Bight Sindermann and Swanson

1980Altered energy and biogeochemical cycling

Increased energy ow through microbes Corpus Christi Bay Montagna and Ritter 2006Production of toxic hydrogen sul de Dead end canals Luther et al. 2004Release of phosphorus from sediments Lake Erie Hawley et al. 2006Release of ammonia and ammonium from sediments Chesapeake Bay Cowan and Boynton 1996Loss of denitri cation Chesapeake Bay Lewis et al. 2007

Table 2. Principal ecosystem characteristics and services impacted by hypoxia. Ecosystemservices are processes by which the environment produces resources that are importantto humans. Lost ecosystem characteristics highlighted here are critical for supportingecosystem services. Not listed here are impacts to aesthetics or services lost due toeutrophication in general.


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commercial and recreational living resources areneeded by managers in order to improve coastalmanagement and policy decision-making. Recentresearch advances in this area are discussed inSection 3.2.

2.4.2. Economic ConsequencesThere is a growing collection of literature on the

ecological consequences of hypoxia, but economicevaluations are lacking. Economic effectsattributable to hypoxia are subtle and dif cultto quantify even when mass mortality eventsoccur. Much of the problem is related to multiplestressors (habitat degradation, over shing, HABs,and pollution) acting on targeted commercial

populations as well as factors that impact sherseconomics (aquaculture, imports, economic costs

of shing, and sheries regulations). Economicimpacts that stem from the effects of hypoxiaon shery stocks are mostly subtle and tied toecological impacts through reduced growth andreproduction. Other economic costs imposed on

shers are related to increased time on shinggrounds and costs of searching for stocks (e.g., toreach more distant shing grounds beyond areas

impacted by hypoxia). How these costs translateto impact on pro ts is complex, however, becausein addition to the rami cations of reduced quantity,the unit value of landings on the market affects itstotal value and must be considered when evaluatingthe economic impacts.

Although quantifying costs of hypoxia-relatedmortality events is dif cult, there are some

published examples (Table 3). Hypoxia in theearly 1970s in Mobile Bay, Alabama was estimatedto have killed over $500,000 worth of oysters(May 1973). An even greater economic cost wasassociated with the declining stock size associatedwith mortality and poor recruitment of oystersin years with severe hypoxia. A modeling studyin the Patuxent River in Maryland estimated thatthe net value of striped bass shing alone woulddecrease over the long-term by over $145 millionif the entire Chesapeake Bay were impacted byhypoxia, which would preclude shing in other sites (Lipton and Hicks 2003). Impacts of hypoxiaon the overall health of the striped bass populationand impacts to other Chesapeake sheries were notincluded in this estimate but would substantially

Event Impacts consideredin Estimate

Estimated EconomicImpact

Economic Impact in2009 dollars

Hypoxia in Mobile Bay in1970s (May 1973) Mortality to oysters $500,000 $2,400,000

Modeled hypoxiain Patuxent River,Maryland (Lipton andHicks 2003)

Striped bass shing andassociated activities inPatuxent River*

$100,000** for dissolvedoxygen below 5 mg/L inthe River

$300,000** for anoxia inthe River

$145,000,000** for dissolved oxygen lessthan 3mg/L in entireChesapeake Bay(eliminates substitute

shing sites)

$110,000**

$340,000**

$166,000,000**

New York Bight hypoxicevent in the summer of1976 (Figley et al. 1979)

Surf clams, n shes,ocean quahogs, seascallops, lobsters

$70,000,000 $265,000,000

* Note that the impact would be substantially greater if all target species were considered.

**Net present value; the net present value represents the chronic effects of hypoxia on the value of striped bassshing.

Table 3. Examples of hypoxia-related economic impacts. For a current perspective, impactsare also shown in 2009 dollars, calculated from the original values using the consumer pricein ation index (http://www.bls.gov/cpi/).


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Climate Driver Direct Effect Secondary Effect Infuence onHypoxia

Increasedtemperature

More evaporation Decreased stream ow -

Land-use and cover changes +/-

Less snow cover More nitrogen retention -

Warmer water Stronger strati cation +

Higher metabolic rates +

More precipitation More stream ow Stronger strati cation +

More nutrient loading +

More extreme rainfall Greater erosion of soil phosphorus +

Less precipitation Less stream ow Weaker strati cation -

Less nutrient loading -

Higher sea level Greater depth Stronger strati cation +

Greater bottom water volume -Less hydraulic mixing +

Less tidal marsh Diminished nutrient trapping +

Summer winds andstorms

Weaker, less watercolumn mixing

More persistent strati cation +

Stronger, more watercolumn mixing

Less persistent strati cation -

Shifting wind patterns Weaker/stronger upwelling potential +/-

Table 4. Estimated in uence of climate drivers on the extent and severity of hypoxia(+ = more hypoxia) (Diaz 2008, Modi ed from Boesch et al. 2007).

increase the overall economic consequences toshers in the region. During the 1976 summer

hypoxic event in the New York Bight, acute

economic losses were estimated to have been over $70 million (Figley et al. 1979). Much of thisloss was due to impacts to the surf clam resource,accounting for more than $60 million. Thesevalues consider short-term impacts from actuallosses reported by shers and potential losses dueto resource mortality.

Experience with hypoxic zones around the globeshows that both ecological and sheries impacts

become progressively more severe as hypoxiaworsens (Diaz and Rosenberg 1995, Caddy1993) and the area of suitable habitat declines(Bricker et al. 2006). Large systems aroundthe globe have suffered serious ecological andeconomic consequences from seasonal hypoxia;most notably the Kattegat and the Black Sea.Consequences range from localized loss of catchand recruitment failure to complete system-wideloss of shery species (Karlsen et al. 2002, Mee

1992). In systems where habitat is only partiallylost to hypoxia, such as Long Island Sound and theChesapeake Bay, catch rates for recreational shing

decline (Bricker et al. 2006).

2.5. Future Considerations2.5.1. Climate change

Climate change will almost certainly in uence both naturally occurring and eutrophication-related hypoxia, as well as the incidence of other ecological problems, such as HABs. To fullyunderstand environmental change, it is necessary toconsider the in uence of multiple climate drivers(Table 4). In general, the expected long-term

ecological changes favor progressively earlier onsetof hypoxia each year and, possibly, longer overallduration (Boesch et al. 2007).

Increasing average water temperature is onemechanism by which climate change may increasesusceptibility of systems to hypoxia. Higher water temperatures promote increased water column


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strati cation, decreased solubilityof oxygen, and increased metabolicrates, including oxygen consumptionand nutrient recycling. Climate

predictions also suggest largechanges in precipitation patterns,

but with signi cant uncertaintyregarding what changes will occur in any given watershed (Christensenet al. 2007). Increased precipitationcan be expected to promoteincreased runoff of nutrients toestuarine and coastal ecosystemsand increased water columnstrati cation within these systems,contributing to more severe oxygendepletion (Table 4, Global ClimateChange Impacts in the U.S. 2009,Justic et al. 2007, Najjar et al.2000). Climate predictions for theMississippi River basin suggesta 20% increase in river discharge(Miller and Russell 1992), which is expected toincrease the average extent of hypoxia on thenorthern Gulf of Mexico shelf (Greene et al. 2009).Climate-associated changes in oceanic wind

patterns can impact ocean circulation at a largescale. The severe hypoxia that has developed every

year since 2002 along the coast of Oregon has beenlinked to climate-based changes in regional wind

patterns, which affect water column strati cationand delivery of nutrients from deep water torelatively shallow coastal areas.

2.5.2. Impacts of Biofuels StrategyThe EISA of 2007 mandates production of

36 billion gallons of biofuels by the year 2022,with a 15 billion gallon limit for the amount tocome from corn. Compared to other potentialsources of biomass for biofuel production, such as

perennial grasses or soybeans, corn is less ef cientat taking up applied nutrients and usually requireshigher nutrient application ratesthese factorscontribute to higher nutrient loadings (especiallynitrogen) with corn (CBC 2007, NRC 2007).Increased production of corn-based ethanol biofuelis projected to exacerbate hypoxia in the Gulf

of Mexico and other coastal areas (Greene et al.2009, Rabalais et al. 2009). Donner and Kucharik (2008) estimate that expanded corn cultivationwill increase the average annual ux of dissolvedinorganic nitrogen to the Gulf of Mexico by 10-34%. The acreage planted in corn grew by 19%

between 2006 and 2007, replacing acreage inconservation reserve programs as well as soybeansand cotton (crops that are frequently less nitrogen-intensive, particularly in the Upper Midwest;see Potter et al. 2006) (Turner et al. 2008, NASS2007). However, this increase did not continueas high fertilizer prices, favorable prices for other crops, and a return to normal crop rotations led toa 7% decline in corn production in 2008 (NASS2008). The EISA mandates that the U.S. biofuelsstrategy be sustainable.

2.5.3. Impacts of Future ManagementDecisionsThe extent of hypoxia in the future will

depend on land management practices includingagricultural practices.. Climate change willaffect water column strati cation, organic matter

production, nutrient discharges, and rates of oxygen consumption. Land management will

Figure 7. Relative magnitude and contribution (the larger the arrow, thelarger the contribution) of land management practices versus climate changefactors to expansion or contraction of low dissolved oxygen (modified fromDiaz and Breitburg 2009).


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Chapter 2

affect nutrient budgets and concentrations of nutrients applied to land through agriculture(Figure 7). For example, the expansion of agriculture for production of crops to be usedfor food and biofuels will, lacking preventiveactions, result in increased nutrient loading tocoastal waters and increased eutrophication effects(U.S. EPA 2007, Rabalais et al. 2007). On theother hand, improved agricultural conservation

practices and large-scale implementation of nutrient best management practices (BMPs) cancreate dramatically better outcomes for water quality. The development of cellulosic ethanol

production will enable farmers and forest managersto derive income from their lands while reducingnutrient runoff. This is an important aspect of the plans to achieve water quality improvementsin the Chesapeake Bay region (Chesapeake BayCommission and Commonwealth of Pennsylvania2008). Application of these alternatives onagricultural lands that contribute disproportionatelyhigh nitrogen loads (e.g., tile-drained elds) will

be especially bene cial. More widespread andaggressive implementation of nutrient removaltechnologies in wastewater and stormwater management also offers opportunities to reducenutrient enrichment, eutrophication, and hypoxia.Together, comprehensive nutrient management

has the potential to offset the impact of human population pressure, which otherwise will likelycontinue to be the main driving factor in the

persistence and spreading of coastal hypoxia.


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Federal Hypoxia and Watershed Science Research:Status and Accomplishments

Chapter 3

T he serious and complex environmental issueof hypoxia and eutrophication cannot bestudied or managed by any one Federal or stateagency, but requires an organized, comprehensiveapproach. This chapter highlights Federalresearch accomplishments since 2003 when thelast HABHRCA-mandated hypoxia assessment

was compiled (CENR 2003). The Federalresearch presented herein is integral for informeddecision-making and successful management of nutrients and hypoxia in an adaptive managementframework (Figure 8).

Under this framework, current scienti cknowledge guides development of managementgoals with the option to continue to assess

knowledge gaps. As scienti c understandingadvances, management goals are reassessedand adjusted as needed. Approaches taken inthe Gulf of Mexico (Box 4), Chesapeake Bay(Box 5), and Long Island Sound (Box 6) providegood examples of the use of science to informmanagement decisions. In addition, regional

governance structures involving multiple stateand Federal partners are emerging as an importantmechanism for mitigating hypoxia because mostcases of coastal hypoxia are linked to nutrientloads resulting from watersheds that cross state

boundaries. Examples include the Gulf of Mexico/Mississippi River Watershed Nutrient Task Force, Gulf of Mexico Alliance, Gulf of MexicoProgram, Great Lakes Regional Collaboration,

Figure 8. Conceptual diagram explaining how, in an adaptive management framework, scientific researchinforms management of environmental problems such as hypoxia (and vice versa).


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Chapter 3

Chesapeake Bay Program, and Puget SoundPartnership. Many of the case studies presentedin Appendix II provide additional descriptionsof regional governance structures. Given theexponential increase in the number of systemsexperiencing hypoxia (Diaz and Rosenberg 2008),it is critical that more states take actions to reducenutrient transport into the coastal zone.

As highlighted in this chapter, each of thevarious research efforts conducted by Federalagencies or funded extramurally by Federalagencies has focused on understanding a differentaspect of the hypoxia issue (Figure 9). Studieshave addressed approaches for reducing nutrientsat their sources, what happens to nutrients duringtransit through the watershed, how nutrients affecthypoxia and related water quality concerns in thecoastal zone, and, nally, how hypoxia impactsaquatic life and ecological services provided bycoastal systems. Recipients of extramural fundshave included state governments and academicorganizations that have coordinated their researchwith Federal research programs (see Appendix I).

Many Federal agencies contribute to researchand management of hypoxia and nutrients. The

primary agencies include NOAA, EPA, USGS, andUSDA . NOAA has focused research funds andinternal capabilities on monitoring and improvingunderstanding of hypoxia and its impacts oncommercially- and ecologically-important livingresources in coastal waters. EPA bridges thecontinuum from freshwater ecosystems to estuariesand coastal waters and has focused resources onunderstanding and regulating nutrient inputs, suchas those from wastewater treatment plants, aswell as studying and modeling hypoxia in coastalwaters. USGS provides critical data through themeasurement and modeling of freshwater andnutrient delivery to coastal waters throughoutthe Nation. Finally, USDA is responsible for

developing and implementing strategies to reducenutrient inputs to coastal waters from agriculturallands and urban ecosystems, which is a major causeof eutrophication and hypoxia in many systems.Recent research accomplishments for these Federalagencies are highlighted in this chapter and in the

place-based case studies in Appendix II. AppendixI provides details about programs in Federal

Box 4. Adaptive Management Approach for Gulf of Mexico Hypoxic Zone

HABHRCA 1998 mandated an integrated scienti c assessment of hypoxia in the northern Gulf of Mexico. Thendings on how and why hypoxia forms in the Gulf informed the rst Action Plan signed by Federal and state

agencies in 2001. The nal recommendation of the 2001 Action Plan called for an updated scienti c assessmentto be completed in ve years which in turn would lead to an updated Action Plan. Following the release of the 2001Action Plan, the Task Force completed a series of reports, including A Science Strategy to Support Management Decisions in 2004 and The Management Action Review in 2006. A series of four state-of-science symposia werealso completed in 2006. These symposia and reports fed into a comprehensive EPA Science Advisory BoardReport. The ndings from the reassessment directly informed the 2008 Action Pl

Hypoxia Report

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