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Eutrophication and hypoxia in coastal areas: a global assessment of the state of knowledge

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MARCH 2008
6WORLD RESOURCES INSTITUTEMarch 2008
WRI POLICY NOTE
WATER QUALITY: EUTROPHICATION AND HYPOXIA No. 1
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
5March 2008WORLD RESOURCES INSTITUTE
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
EUTROPHICATION AND
HYPOXIA IN COASTAL AREAS:
A GLOBAL ASSESSMENT OF
THE STATE OF KNOWLEDGE
MINDY SELMAN, SUZIE GREENHALGH, ROBERT DIAZ AND ZACHARY SUGG
Within the past 50 years, eutrophication—the overen-
richment of water by nutrients such as nitrogen and
phosphorus—has emerged as one of the leading causes of water
quality impairment. Our research identifi es over 415 areas
worldwide that are experiencing symptoms of eutrophication,
highlighting the global scale of the problem.
Recent coastal surveys of the United States and Europe found
that a staggering 78 percent of the assessed continental U.S.
coastal area and approximately 65 percent of Europe’s Atlantic
coast exhibit symptoms of eutrophication.
1,2
In other regions,
the lack of reliable data hinders the assessment of coastal
eutrophication. Nevertheless, trends in agricultural practices,
energy use, and population growth indicate that coastal eutro-
phication will be an ever-growing problem.
This policy note focuses on what is currently known about the
extent of eutrophication globally, and how to improve the state
of our knowledge to more accurately inform and drive policy
decisions for mitigating eutrophication. Complementary policy
notes will discuss in more detail the sources of nutrients and
actions that can be implemented to mitigate eutrophication.
Key Messages
Eutrophication—the overenrichment of waters by nutrients—threat-
ens and degrades many coastal ecosystems around the world. The two
most acute symptoms of eutrophication are hypoxia (or oxygen deple-
tion) and harmful algal blooms, which among other things can destroy
aquatic life in affected areas.
Of the 415 areas around the world identifi ed as experiencing some
form of eutrophication, 169 are hypoxic and only 13 systems are clas-
sifi ed as “systems in recovery.”
Mapping and research into the extent of eutrophication and its threats
to human health and ecosystem services are improving, but there is
still insuffi cient information in many regions of the world to establish
the actual extent of eutrophication or identify the sources of nutri-
ents. To develop effective policies to mitigate eutrophication, more
information is required on the extent of eutrophication, the sources of
nutrients, and the impact of eutrophication on ecosystems.
Recommendations
To improve knowledge of where eutrophication is occurring and its
impacts, environmental agencies or coastal authorities worldwide
need to proactively assess and monitor water quality, specifi cally those
variables commonly linked to eutrophication such as nutrient levels
and dissolved oxygen. In addition, internationally accepted methods
and defi nitions for assessing and classifying eutrophic coastal wa-
ters—including proxies for eutrophication—need to be developed.
In Asia, Africa, and Latin America, environmental agencies or coastal
authorities should:
1. Undertake systematic and routine assessments of coastal areas,
particularly those exhibiting symptoms of eutrophication.
2. Develop transparent and public reporting procedures for tracking
the occurrence of eutrophication and hypoxia, as well as monitoring
their impact on ecosystem health.
3. Develop and adopt decision-support tools—such as nutrient bud-
gets and water quality models—that can facilitate the development
of appropriate local and regional responses to eutrophication.
In the United States, Europe, and Australia, environmental agencies
or coastal authorities should:
1. Continue coastal zone assessments.
2. Ensure that eutrophication assessment methodologies are being
consistently applied.
3. Enhance existing decision-support tools and develop tools for those
areas where none currently exist.
Bay, Baltic Sea, Black Sea, Gulf of Mexico (Mississippi-Atcha-
falaya plume), and Tampa Bay. The absence of detailed nutri-
ent budgets for the majority of eutrophic and hypoxic systems
around the world highlights the lack of concerted research
efforts in these areas, compromising the ability to effectively
address and manage nutrient overenrichment.
HOW DO WE IMPROVE THE STATE OF KNOWLEDGE?
To better assess the global, regional, and local extent of eutrophi-
cation, we need more and better data. Improving our knowledge
of where eutrophication is occurring, the sources contributing
to the problem, and the effects of eutrophication on marine
ecosystems and human communities ultimately infl uences the
ability of policy-makers to decide where and how resources can
be used most effectively to address eutrophication.
Closing the knowledge gap requires increased and improved
water quality monitoring and assessment of estuarine and
coastal waters. Without this information, communities cannot
effectively manage coastal ecosystems and address land-based
sources of pollution. Specifically, time series monitoring
data—on nutrient levels, chlorophyll a (as an indicator of the
presence of phytoplankton), and dissolved oxygen—as well
as eutrophication response parameters—such as loss of sub-
aquatic vegetation, fi sh kills, and algal blooms—are needed to
evaluate the extent and degree of eutrophication. Moreover,
widespread use and adoption of methods to classify and defi ne
eutrophic waters (such as the ones developed by NOAA and
OSPAR) are needed to increase the transparency, consistency,
and comparability of water quality information. For example,
currently no common defi nition of “hypoxia” exists and the
interpretation of what is hypoxic can vary widely from place
to place.
In countries or regions where robust and systematic monitor-
ing programs are unlikely to be implemented due to limited
resources, it would be benefi cial to develop credible and con-
sistent proxies for water quality (such as turbidity or sulfi de
smell) that could be used to identify likely eutrophic areas.
Finally, decision support tools that enable researchers and
policy-makers to formulate appropriate responses to eutro-
phication need to be continually developed and more widely
adopted by local and regional entities. Such tools include:
Watershed models to assess nutrient delivery and ecosys-
tem impacts;
Nutrient balance assessments to determine the sources of
nutrients and relative contribution of each source;
Regional and international online information portals
for compiling and sharing water quality information and
research;
Nutrient loss estimation tools; and
Tools to help assess the effectiveness of alternative sce-
narios for reducing nutrient inputs.
Implementation of these tools is especially needed to estimate
coastal impacts and target appropriate policy responses in coun-
tries and regions where actual monitoring data are scarce.
Eutrophication is an issue that requires greater attention by gov-
ernments and society in general. Left untouched, it may have
dire consequences for many ecosystems, the food webs that they
support, and the livelihoods of the populations that depend on
them. To get a better grasp on the immediate and long-term
consequences of eutrophication, we need more resources and
better information. Improving our knowledge and information
on eutrophication is the fi rst step in developing robust policy
measures to begin reversing or halting its impacts.
ABOUT THE AUTHORS
Mindy Selman is a senior associate in the People and
Ecosystems Program of the World Resources Institute.
Ph: +1-202-729 7644. Email: mselman@wri.org
Suzie Greenhalgh is a senior economist at Landcare
Research New Zealand Ltd. Ph: +64-9-574 4132.
Email: greenhalghs@landcareresearch.co.nz
Robert Diaz is a professor of marine science at the College
of William and Mary, Virginia Institute of Marine Science.
Ph: +1-804-684 7364. Email: diaz@vims.edu
Zachary Sugg is a research analyst with the People and
Ecosystems Program of the World Resources Institute.
Ph: +1-202-729 7605. Email: zsugg@wri.org
ACKNOWLEDGMENTS
The authors are grateful for the contributions provided by
Donald Anderson, James Galloway, Paul Harrison, Laurence
Mee, Qian Yi, and Nancy Rabalais, who served on a WRI
eutrophication advisory panel. The authors would also like to
acknowledge Kersey Sturdivant for his research assistance in
identifying areas of eutrophication. In addition, the authors
thank Craig Hanson, Lauretta Burke, Amy Cassara, Dan
Tunstall, Laurence Mee, and James Galloway for reviewing
earlier drafts of this paper. Finally, we extend our thanks to
the Linden Trust for Conservation and the David and Lucile
Packard Foundation for their support of this research.
NOTES
1. See Bricker, S. B., Longstaff, W. Dennison, A. Jones, K. Boicourt, C.
Wicks, and J. Woerner. 2007. Effects of Nutrient Enrichment in the
Nation’s Estuaries: A Decade of Change. NOAA Coastal Ocean Program
Decision Analysis Series No. 26. Silver Spring, MD: National Centers
for Coastal Ocean Science. Online at: http://ccma.nos.noaa.gov/publica-
tions/eutroupdate/
2. See OSPAR Commission. 2003. OSPAR integrated report 2003 on the
eutrophication status. London, U.K.: OSPAR.
3. See Howarth, R. and K. Ramakrrshna. 2005. “Nutrient Management.”
In K. Chopra, R. Leemans, P. Kumar, and H. Simons, eds. Ecosystems
and Human Wellbeing: Policy Responses. Volume 3 of the Millennium
Ecosystem Assessment (MA). Washington, DC: Island Press.
4. See National Oceanic and Atmospheric Administration (NOAA). “Global
Warming: Frequently asked questions.” Available at: http://lwf.ncdc.
noaa.gov/oa/climate/globalwarming.html. (accessed January 15, 2008)
5. See Galloway, J.N, J.D. Aber,, J.W. Erisman, S.P. Seitzinger, R.W.
Howarth, E.B. Cowling, and B.J. Cosby. 2003. “The Nitrogen Cascade.”
Bioscience 53( 4): 341–356
6. For a discussion on the impacts of eutrophication on coastal ecosystems,
see Mee, L. 2006. “Reviving Dead Zones.” Scientifi c American 295 (5):
79–85.
7. See: UN Chronicle Online Edition. “Risks, Untreated Sewage Threat-
ens Seas, Coastal Population.” http://www.un.org/Pubs/chronicle/2003/
issue1/0103p39.html. (accessed January 15, 2008)
8. Harmful algal blooms refer to several species of algae that produce tox-
ins that are harmful to aquatic life. See Anderson, D. M., P. M. Gilbert,
and J. M. Burkholder. 2002. “Harmful Algal Blooms and Eutrophica-
tion: Nutrient Sources, Composition, and Consequences.” Estuaries 25
(4b): 704–726.
9. See: Terra Daily Online Edition. “Hong Kong red tide spreads,” (June
10, 2007). http://www.terradaily.com/reports/Hong_Kong_Red_Tide_
Spreads_999.html (accessed February 8, 2008).
10. See Lu, S., and I. J. Hodgkiss. 2004. “Harmful algal bloom causative
collected from Hong Kong waters.” Hydrobiologia.512(1-3): 231-238
11. Hypoxia is generally defi ned as having a dissolved oxygen concentration
of 2.0 milligrams per liter or less.
12. See Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
13. See Rabalais, N. N., and R. E. Turner. 2001. Coastal hypoxia conse-
quences for living resources and ecosystems. Washington, DC: American
Geophysical Union.
14. See Europe Now|Next. “Is the Black Sea recovering?” http://www.eu-
rope.culturebase.net/contribution.php?media=307 (accessed December
30, 2008)
15. See Howarth, R. and K. Ramakrrshna. 2005. “Nutrient Management.”
In K. Chopra, R. Leemans, P. Kumar, and H. Simons, eds. Ecosystems
and Human Wellbeing: Policy Responses. Volume 3 of the Millennium
Ecosystem Assessment (MA). Washington, DC: Island Press.
16. See Spokes, L. J., and T. D. Jickells. 2005. “Is the atmosphere really an
important source of reactive nitrogen to coastal waters?” Continental
Shelf Research 25: 2022–2035.
17. Region-specifi c maps as well as the data used to create these maps is
made available on WRI’s website, www.wri.org/project/water-quality.
18. See Diaz, R. and R. Rosenburg. 1995. “Marine benthic hypoxia: a
review of its ecological effects and the behavioural responses of benthic
macrofauna.” Oceanography and Marine Biology: an Annual Review 33:
245–303.
19. The primary data sources include:
Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
Bricker, S. B., Longstaff, W. Dennison, A. Jones, K. Boicourt, C. Wicks,
and J. Woerner. 2007. Effects of Nutrient Enrichment in the Nation’s
Estuaries: A Decade of Change. NOAA Coastal Ocean Program Decision
Analysis Series No. 26. Silver Spring, MD: National Centers for Coastal
Ocean Science. Online at: http://ccma.nos.noaa.gov/publications/eu-
troupdate/.
OSPAR Commission. 2003. OSPAR integrated report 2003 on the eutro-
phication status. London, UK: OSPAR.
OzEstuaries. 2005. “Anoxic and Hypoxic Events.” Online at: http://www.
ozestuaries. org/indicators/anoxic_hypoxic_events.jsp (August, 2005).
United Nations Environment Program (UNEP). 2006. Challenges to
International Waters – Regional Assessments in a Global Perspective.
Nairobi, Kenya: United Nations.
20. See Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
21. OSPAR called for the uniform assessment of coastal waters by signatory
countries. Signatory countries to the 1992 Oslo-Paris Convention for
the Protection of the Marine Environment of the North-East Atlantic
(OSPAR Convention) include Belgium, Denmark, France, Germany,
Ireland, The Netherlands, Norway, Portugal, Spain, Sweden, and the
United Kingdom.
ABOUT WRI
The World Resources Institute is an environ-
mental think tank that goes beyond research
to fi nd practical ways to protect the Earth and
improve people’s lives. Our mission is to move
human society to live in ways that protect the
Earth’s environment and its capacity to pro-
vide for the needs and aspirations of current
and future generations.
Forthcoming publications in this series include:
1. Eutrophication: Sources and Drivers of Nutrient Pollution
2. Eutrophication: A Policy Framework for Addressing
Nutrient Pollution
Please visit www.wri.org/policynotes for links to available
Policy Notes.
BAR CODE TO COME
Red algal bloom at Leigh, near Cape Rodney, NZ.
PHOTO BY MIRIAM GODFREY. USED BY PERMISSION OF NIWA SCIENCE.
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
2 3
March 2008WORLD RESOURCES INSTITUTE 4WORLD RESOURCES INSTITUTEMarch 2008
WHY IS EUTROPHICATION A PROBLEM?
The rise in eutrophic and hypoxic events has been primar-
ily attributed to the rapid increase in intensive agricultural
practices, industrial activities, and population growth, which
together have increased nitrogen and phosphorus fl ows in
the environment. Human activities have resulted in the near
doubling of nitrogen and tripling of phosphorus fl ows to the en-
vironment when compared to natural values.
3
By comparison,
human activities have increased atmospheric concentrations
of carbon dioxide, the gas primarily responsible for global
warming, by approximately 32 percent since the onset of the
industrial age.
4
Before nutrients—nitrogen in particular—are delivered to
coastal ecosystems, they pass through a variety of terrestrial and
freshwater ecosystems, causing other environmental problems
such as freshwater quality impairments, acid rain, the forma-
tion of greenhouse gases, shifts in community food webs, and
a loss of biodiversity.
5
Once nutrients reach coastal systems, they can trigger a number
of responses within the ecosystem. The initial impacts of nutri-
ent increases are the excessive growth of phytoplankton, micro-
algae (e.g., epiphytes and microphytes), and macroalgae (i.e.,
seaweed). These, in turn, can lead to other impacts such as:
Loss of subaquatic vegetation as excessive phytoplankton,
microalgae, and macroalgae growth reduce light penetra-
tion.
Change in species composition and biomass of the ben-
thic (bottom-dwelling) aquatic community, eventually
leading to reduced species diversity and the dominance
of gelatinous organisms such as jellyfi sh.
Coral reef damage as increased nutrient levels favor
algae growth over coral larvae. Coral growth is inhibited
because the algae outcompetes coral larvae for available
surfaces to grow.
A shift in phytoplankton species composition, creating
favorable conditions for the development of nuisance,
toxic, or otherwise harmful algal blooms.
Low dissolved oxygen and formation of hypoxic or “dead”
zones (oxygen-depleted waters), which in turn can lead to
ecosystem collapse.
6
The scientifi c community is increasing its knowledge of how
eutrophication affects coastal ecosystems, yet the long-term
implications of increased nutrient fl uxes in our coastal waters
are currently not entirely known or understood. We do know
that eutrophication diminishes the ability of coastal ecosystems
to provide valuable ecosystem services such as tourism, recre-
ation, the provision of fi sh and shellfi sh for local communities,
sportfi shing, and commercial fi sheries. In addition, eutrophica-
tion can lead to reductions in local and regional biodiversity.
Today nearly half of the world’s population lives within 60 ki-
lometers of the coast, with many communities relying directly
on coastal ecosystems for their livelihoods.
7
This means that a
signifi cant portion of the world’s population is vulnerable to the
effects of eutrophication in their local coastal ecosystems.
Harmful Algal Blooms and Hypoxia. Two of the most acute and
commonly recognized symptoms of eutrophication are harmful
algal blooms and hypoxia.
Harmful algal blooms can cause fish kills, human illness
through shellfi sh poisoning, and death of marine mammals
and shore birds.
8
Harmful algal blooms are often referred to
as “red tides” or “brown tides” because of the appearance of
the water when these blooms occur. One red tide event, which
occurred near Hong Kong in 1998, wiped out 90 percent of
the entire stock of Hong Kong’s fi sh farms and resulted in an
estimated economic loss of $40 million USD.
9,10
Hypoxia, considered to be the most severe symptom of eutro-
phication, has escalated dramatically over the past 50 years,
increasing from about 10 documented cases in 1960 to at least
169 in 2007.
11,12
Hypoxia occurs when algae and other organ-
isms die, sink to the bottom, and are decomposed by bacteria,
using the available dissolved oxygen. Salinity and temperature
differences between surface and subsurface waters lead to
stratifi cation, limiting oxygen replenishment from surface
waters and creating conditions that can lead to the formation
of a hypoxic or “dead” zone.
13
Two of the most well-known hypoxic areas are the Gulf of
Mexico and the Black Sea. The Gulf of Mexico has a seasonal
hypoxic zone that forms every year in late summer. Its size
varies; in 2000, it was less than 5,000 km2, while in 2002 it
was approximately 22,000 km2 (or the size of the U.S. state of
Massachusetts). While the economic consequences of the Gulf
of Mexico dead zone are still unclear, concern over its increas-
ing size led to the formation of the Mississippi River/Gulf of
Mexico Watershed Nutrient Task Force in 1997 to develop a
strategy to reduce the fi ve-year running average areal extent of
the Gulf of Mexico hypoxic zone to less than 5,000 km2.
The Black Sea, which was once the largest dead zone in the
world, had 26 commercially viable fi sh species in the 1960s but
The fi rst comprehensive list of hypoxic zones was compiled by
Diaz and Rosenberg in 1995 and identifi ed 44 documented
hypoxic areas.
18
Twelve years later, there are 169 documented
hypoxic areas, a nearly four-fold increase. The list of hypoxic
areas assembled by Diaz was compiled from scientifi c litera-
ture and identifi ed the majority of documented hypoxic areas.
However, the list did not include areas with suspected—but
not documented—hypoxic events or systems that suffer from
other impacts of eutrophication such as nuisance or harmful
algal blooms, loss of subaquatic vegetation, and changes in
the structure of the benthic aquatic community (for example,
decline in biomass, changes in species composition, and loss
of diversity).
To supplement this list of hypoxic zones, the authors undertook
an extensive literature review to catalog systems experiencing
any symptoms of eutrophication, including—but not limited
to—hypoxia.
19
The eutrophic areas identifi ed were categorized
as:
Documented hypoxic areas. Areas with scientifi c evidence
that hypoxia was caused, at least in part, by nutrient
overenrichment. This category includes the most recent
list of hypoxic areas compiled by Diaz (excluding hypoxia
caused by natural upwelling of nutrients), as well as some
additional systems identifi ed by our research.
20
Areas of concern. Systems that exhibit effects of eutrophi-
cation, such as elevated nutrient levels, elevated chloro-
phyll a levels, harmful algal blooms, changes in the benthic
community, damage to coral reefs, and fi sh kills. These
systems are impaired by nutrients and are possibly at risk
of developing hypoxia. Some of the systems classifi ed as
areas of concern may already be experiencing hypoxia, but
lack conclusive scientifi c evidence of the condition.
Systems in recovery. Areas that once exhibited low dis-
solved oxygen levels and hypoxia, but are now improving.
For example, the Black Sea once experienced annual
hypoxic events, but is now in a state of recovery. Others,
like Boston Harbor in the United States and the Mersey
Estuary in the United Kingdom, also have improved
water quality resulting from better industrial and waste-
water controls.
WHERE ARE THE DATA INCONSISTENCIES AND GAPS?
The actual extent and prevalence of eutrophication in many
regions is only beginning to be studied. As a consequence, data
do not exist or are not publicly available for many areas that
may be suffering from the effects of eutrophication. In addi-
tion, the data that do exist are often inconsistent in terms of
parameters measured, indicators used, and the scale at which
data are reported.
Given the state of global data, the number of eutrophic and
hypoxic areas around the world is expected to be greater than
the 415 listed here. The most underrepresented region is Asia.
Asia has relatively few documented eutrophic and hypoxic
areas despite large increases in intensive farming methods,
industrial development, and population growth over the past
20 years. Africa, Latin America, and the Caribbean also have
few reliable sources of coastal water quality data, making it
diffi cult to assess the true level of eutrophication.
The scale at which data for eutrophic areas are reported var-
ies greatly. For example, red tides and other eutrophic events
are frequently recorded in the South China Sea, Yellow Sea,
and Bohai Sea. However, the actual extent of eutrophication
or hypoxia in specifi c bays and estuaries within these systems
is unknown. Therefore, these areas are coarsely recorded in
Figure 1 and most likely represent several affected bays and
estuaries along the Chinese coast. Conversely, within the
well-studied Chesapeake Bay system, there are 12 distinct and
documented eutrophic and hypoxic zones.
The United States, European Union, and Australia—all of which
have each undertaken comprehensive coastal surveys in the past
ve years—have the most comprehensive coastal data on eutro-
phication. However, even within the United States and Europe,
the quality, consistency, and availability of water quality data
varies. For example, in Europe, the coastal survey coordinated
through the Commission for the Protection of the Marine En-
vironment of the North-East Atlantic (OSPAR)
highlighted the
variability in quality and availability of monitoring data among
the various European countries.
21
Several coastal areas lacked
dissolved oxygen measures and many of the secondary effects
of eutrophication, such as fi sh kills and changes in the benthic
community, were not extensively monitored. The U.S. National
Oceanic and Atmospheric Agency’s (NOAA) National Estuarine
Eutrophication Assessment program, which conducted national
eutrophication surveys in 1999 and 2007, experienced data
issues similar to those encountered in the OSPAR survey. Of
the 141 U.S. estuaries evaluated in 2007, 30 percent lacked
adequate data for assessing their eutrophication status.
Most systems identifi ed as hypoxic or eutrophic also lack
detailed data on the sources of nutrient impairments and the
relative contribution of each source. Some systems that have
developed detailed nutrient budgets include the Chesapeake
only fi ve species by the 1980s.
14
The growth of the Black Sea
hypoxic zone was attributed to the intensifi cation of agriculture
in the former Soviet Union. It has been “in recovery” since
the economic collapse of Eastern Europe in the 1990s, which
resulted in signifi cant reductions in fertilizer use.
WHAT ARE THE SOURCES OF NUTRIENTS?
Agriculture, human sewage, urban runoff, industrial effl uent,
and fossil fuel combustion are the most common sources of
nutrients delivered to coastal systems. Among regions, there are
signifi cant variations in the relative importance of each nutrient
source. For example, in the United States and the European
Union, agricultural sources (particularly animal manure and
commercial fertilizers) are generally the primary contributors
to eutrophication, while sewage and industrial discharges,
which usually receive some treatment prior to discharge, are a
secondary source. However, in Latin America, Asia, and Africa,
wastewater from sewage and industry are often untreated and
may often be the primary contributors to eutrophication. It is
currently estimated that only 35 percent of wastewater in Asia
is treated, 14 percent in Latin America and the Caribbean, and
less than 1 percent in Africa.
15
Atmospheric sources of nitrogen are also recognized as a sig-
nifi cant contributor of nutrients in coastal areas.
16
Nitrogen
from fossil fuel combustion and volatilization from fertilizers
and manure is released into the atmosphere and redeposited
on land and in water by wind, snow, and rain. In the Chesa-
peake Bay in the mid-Atlantic region of the eastern United
States, atmospheric sources of nitrogen account for a third
of all controllable nitrogen that enters the Bay; similarly, in
the Baltic Sea in Europe, atmospheric nitrogen accounts for
a fourth of all controllable nitrogen.
WHERE ARE THE GLOBAL EUTROPHIC AND HYPOXIC
AREAS?
Our research identifi ed 415 eutrophic and hypoxic coastal
systems worldwide (Figure 1).
17
Of these, 169 are documented
hypoxic areas, 233 are areas of concern, and 13 are systems
in recovery.
The coastal areas reported as experiencing eutrophication are
steadily growing. This is because of the increasing prevalence
of eutrophication and advances in identifying and reporting
eutrophic conditions.
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
2 3
March 2008WORLD RESOURCES INSTITUTE 4WORLD RESOURCES INSTITUTEMarch 2008
WHY IS EUTROPHICATION A PROBLEM?
The rise in eutrophic and hypoxic events has been primar-
ily attributed to the rapid increase in intensive agricultural
practices, industrial activities, and population growth, which
together have increased nitrogen and phosphorus fl ows in
the environment. Human activities have resulted in the near
doubling of nitrogen and tripling of phosphorus fl ows to the en-
vironment when compared to natural values.
3
By comparison,
human activities have increased atmospheric concentrations
of carbon dioxide, the gas primarily responsible for global
warming, by approximately 32 percent since the onset of the
industrial age.
4
Before nutrients—nitrogen in particular—are delivered to
coastal ecosystems, they pass through a variety of terrestrial and
freshwater ecosystems, causing other environmental problems
such as freshwater quality impairments, acid rain, the forma-
tion of greenhouse gases, shifts in community food webs, and
a loss of biodiversity.
5
Once nutrients reach coastal systems, they can trigger a number
of responses within the ecosystem. The initial impacts of nutri-
ent increases are the excessive growth of phytoplankton, micro-
algae (e.g., epiphytes and microphytes), and macroalgae (i.e.,
seaweed). These, in turn, can lead to other impacts such as:
Loss of subaquatic vegetation as excessive phytoplankton,
microalgae, and macroalgae growth reduce light penetra-
tion.
Change in species composition and biomass of the ben-
thic (bottom-dwelling) aquatic community, eventually
leading to reduced species diversity and the dominance
of gelatinous organisms such as jellyfi sh.
Coral reef damage as increased nutrient levels favor
algae growth over coral larvae. Coral growth is inhibited
because the algae outcompetes coral larvae for available
surfaces to grow.
A shift in phytoplankton species composition, creating
favorable conditions for the development of nuisance,
toxic, or otherwise harmful algal blooms.
Low dissolved oxygen and formation of hypoxic or “dead”
zones (oxygen-depleted waters), which in turn can lead to
ecosystem collapse.
6
The scientifi c community is increasing its knowledge of how
eutrophication affects coastal ecosystems, yet the long-term
implications of increased nutrient fl uxes in our coastal waters
are currently not entirely known or understood. We do know
that eutrophication diminishes the ability of coastal ecosystems
to provide valuable ecosystem services such as tourism, recre-
ation, the provision of fi sh and shellfi sh for local communities,
sportfi shing, and commercial fi sheries. In addition, eutrophica-
tion can lead to reductions in local and regional biodiversity.
Today nearly half of the world’s population lives within 60 ki-
lometers of the coast, with many communities relying directly
on coastal ecosystems for their livelihoods.
7
This means that a
signifi cant portion of the world’s population is vulnerable to the
effects of eutrophication in their local coastal ecosystems.
Harmful Algal Blooms and Hypoxia. Two of the most acute and
commonly recognized symptoms of eutrophication are harmful
algal blooms and hypoxia.
Harmful algal blooms can cause fish kills, human illness
through shellfi sh poisoning, and death of marine mammals
and shore birds.
8
Harmful algal blooms are often referred to
as “red tides” or “brown tides” because of the appearance of
the water when these blooms occur. One red tide event, which
occurred near Hong Kong in 1998, wiped out 90 percent of
the entire stock of Hong Kong’s fi sh farms and resulted in an
estimated economic loss of $40 million USD.
9,10
Hypoxia, considered to be the most severe symptom of eutro-
phication, has escalated dramatically over the past 50 years,
increasing from about 10 documented cases in 1960 to at least
169 in 2007.
11,12
Hypoxia occurs when algae and other organ-
isms die, sink to the bottom, and are decomposed by bacteria,
using the available dissolved oxygen. Salinity and temperature
differences between surface and subsurface waters lead to
stratifi cation, limiting oxygen replenishment from surface
waters and creating conditions that can lead to the formation
of a hypoxic or “dead” zone.
13
Two of the most well-known hypoxic areas are the Gulf of
Mexico and the Black Sea. The Gulf of Mexico has a seasonal
hypoxic zone that forms every year in late summer. Its size
varies; in 2000, it was less than 5,000 km2, while in 2002 it
was approximately 22,000 km2 (or the size of the U.S. state of
Massachusetts). While the economic consequences of the Gulf
of Mexico dead zone are still unclear, concern over its increas-
ing size led to the formation of the Mississippi River/Gulf of
Mexico Watershed Nutrient Task Force in 1997 to develop a
strategy to reduce the fi ve-year running average areal extent of
the Gulf of Mexico hypoxic zone to less than 5,000 km2.
The Black Sea, which was once the largest dead zone in the
world, had 26 commercially viable fi sh species in the 1960s but
The fi rst comprehensive list of hypoxic zones was compiled by
Diaz and Rosenberg in 1995 and identifi ed 44 documented
hypoxic areas.
18
Twelve years later, there are 169 documented
hypoxic areas, a nearly four-fold increase. The list of hypoxic
areas assembled by Diaz was compiled from scientifi c litera-
ture and identifi ed the majority of documented hypoxic areas.
However, the list did not include areas with suspected—but
not documented—hypoxic events or systems that suffer from
other impacts of eutrophication such as nuisance or harmful
algal blooms, loss of subaquatic vegetation, and changes in
the structure of the benthic aquatic community (for example,
decline in biomass, changes in species composition, and loss
of diversity).
To supplement this list of hypoxic zones, the authors undertook
an extensive literature review to catalog systems experiencing
any symptoms of eutrophication, including—but not limited
to—hypoxia.
19
The eutrophic areas identifi ed were categorized
as:
Documented hypoxic areas. Areas with scientifi c evidence
that hypoxia was caused, at least in part, by nutrient
overenrichment. This category includes the most recent
list of hypoxic areas compiled by Diaz (excluding hypoxia
caused by natural upwelling of nutrients), as well as some
additional systems identifi ed by our research.
20
Areas of concern. Systems that exhibit effects of eutrophi-
cation, such as elevated nutrient levels, elevated chloro-
phyll a levels, harmful algal blooms, changes in the benthic
community, damage to coral reefs, and fi sh kills. These
systems are impaired by nutrients and are possibly at risk
of developing hypoxia. Some of the systems classifi ed as
areas of concern may already be experiencing hypoxia, but
lack conclusive scientifi c evidence of the condition.
Systems in recovery. Areas that once exhibited low dis-
solved oxygen levels and hypoxia, but are now improving.
For example, the Black Sea once experienced annual
hypoxic events, but is now in a state of recovery. Others,
like Boston Harbor in the United States and the Mersey
Estuary in the United Kingdom, also have improved
water quality resulting from better industrial and waste-
water controls.
WHERE ARE THE DATA INCONSISTENCIES AND GAPS?
The actual extent and prevalence of eutrophication in many
regions is only beginning to be studied. As a consequence, data
do not exist or are not publicly available for many areas that
may be suffering from the effects of eutrophication. In addi-
tion, the data that do exist are often inconsistent in terms of
parameters measured, indicators used, and the scale at which
data are reported.
Given the state of global data, the number of eutrophic and
hypoxic areas around the world is expected to be greater than
the 415 listed here. The most underrepresented region is Asia.
Asia has relatively few documented eutrophic and hypoxic
areas despite large increases in intensive farming methods,
industrial development, and population growth over the past
20 years. Africa, Latin America, and the Caribbean also have
few reliable sources of coastal water quality data, making it
diffi cult to assess the true level of eutrophication.
The scale at which data for eutrophic areas are reported var-
ies greatly. For example, red tides and other eutrophic events
are frequently recorded in the South China Sea, Yellow Sea,
and Bohai Sea. However, the actual extent of eutrophication
or hypoxia in specifi c bays and estuaries within these systems
is unknown. Therefore, these areas are coarsely recorded in
Figure 1 and most likely represent several affected bays and
estuaries along the Chinese coast. Conversely, within the
well-studied Chesapeake Bay system, there are 12 distinct and
documented eutrophic and hypoxic zones.
The United States, European Union, and Australia—all of which
have each undertaken comprehensive coastal surveys in the past
ve years—have the most comprehensive coastal data on eutro-
phication. However, even within the United States and Europe,
the quality, consistency, and availability of water quality data
varies. For example, in Europe, the coastal survey coordinated
through the Commission for the Protection of the Marine En-
vironment of the North-East Atlantic (OSPAR)
highlighted the
variability in quality and availability of monitoring data among
the various European countries.
21
Several coastal areas lacked
dissolved oxygen measures and many of the secondary effects
of eutrophication, such as fi sh kills and changes in the benthic
community, were not extensively monitored. The U.S. National
Oceanic and Atmospheric Agency’s (NOAA) National Estuarine
Eutrophication Assessment program, which conducted national
eutrophication surveys in 1999 and 2007, experienced data
issues similar to those encountered in the OSPAR survey. Of
the 141 U.S. estuaries evaluated in 2007, 30 percent lacked
adequate data for assessing their eutrophication status.
Most systems identifi ed as hypoxic or eutrophic also lack
detailed data on the sources of nutrient impairments and the
relative contribution of each source. Some systems that have
developed detailed nutrient budgets include the Chesapeake
only fi ve species by the 1980s.
14
The growth of the Black Sea
hypoxic zone was attributed to the intensifi cation of agriculture
in the former Soviet Union. It has been “in recovery” since
the economic collapse of Eastern Europe in the 1990s, which
resulted in signifi cant reductions in fertilizer use.
WHAT ARE THE SOURCES OF NUTRIENTS?
Agriculture, human sewage, urban runoff, industrial effl uent,
and fossil fuel combustion are the most common sources of
nutrients delivered to coastal systems. Among regions, there are
signifi cant variations in the relative importance of each nutrient
source. For example, in the United States and the European
Union, agricultural sources (particularly animal manure and
commercial fertilizers) are generally the primary contributors
to eutrophication, while sewage and industrial discharges,
which usually receive some treatment prior to discharge, are a
secondary source. However, in Latin America, Asia, and Africa,
wastewater from sewage and industry are often untreated and
may often be the primary contributors to eutrophication. It is
currently estimated that only 35 percent of wastewater in Asia
is treated, 14 percent in Latin America and the Caribbean, and
less than 1 percent in Africa.
15
Atmospheric sources of nitrogen are also recognized as a sig-
nifi cant contributor of nutrients in coastal areas.
16
Nitrogen
from fossil fuel combustion and volatilization from fertilizers
and manure is released into the atmosphere and redeposited
on land and in water by wind, snow, and rain. In the Chesa-
peake Bay in the mid-Atlantic region of the eastern United
States, atmospheric sources of nitrogen account for a third
of all controllable nitrogen that enters the Bay; similarly, in
the Baltic Sea in Europe, atmospheric nitrogen accounts for
a fourth of all controllable nitrogen.
WHERE ARE THE GLOBAL EUTROPHIC AND HYPOXIC
AREAS?
Our research identifi ed 415 eutrophic and hypoxic coastal
systems worldwide (Figure 1).
17
Of these, 169 are documented
hypoxic areas, 233 are areas of concern, and 13 are systems
in recovery.
The coastal areas reported as experiencing eutrophication are
steadily growing. This is because of the increasing prevalence
of eutrophication and advances in identifying and reporting
eutrophic conditions.
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
2 3
March 2008WORLD RESOURCES INSTITUTE 4WORLD RESOURCES INSTITUTEMarch 2008
WHY IS EUTROPHICATION A PROBLEM?
The rise in eutrophic and hypoxic events has been primar-
ily attributed to the rapid increase in intensive agricultural
practices, industrial activities, and population growth, which
together have increased nitrogen and phosphorus fl ows in
the environment. Human activities have resulted in the near
doubling of nitrogen and tripling of phosphorus fl ows to the en-
vironment when compared to natural values.
3
By comparison,
human activities have increased atmospheric concentrations
of carbon dioxide, the gas primarily responsible for global
warming, by approximately 32 percent since the onset of the
industrial age.
4
Before nutrients—nitrogen in particular—are delivered to
coastal ecosystems, they pass through a variety of terrestrial and
freshwater ecosystems, causing other environmental problems
such as freshwater quality impairments, acid rain, the forma-
tion of greenhouse gases, shifts in community food webs, and
a loss of biodiversity.
5
Once nutrients reach coastal systems, they can trigger a number
of responses within the ecosystem. The initial impacts of nutri-
ent increases are the excessive growth of phytoplankton, micro-
algae (e.g., epiphytes and microphytes), and macroalgae (i.e.,
seaweed). These, in turn, can lead to other impacts such as:
Loss of subaquatic vegetation as excessive phytoplankton,
microalgae, and macroalgae growth reduce light penetra-
tion.
Change in species composition and biomass of the ben-
thic (bottom-dwelling) aquatic community, eventually
leading to reduced species diversity and the dominance
of gelatinous organisms such as jellyfi sh.
Coral reef damage as increased nutrient levels favor
algae growth over coral larvae. Coral growth is inhibited
because the algae outcompetes coral larvae for available
surfaces to grow.
A shift in phytoplankton species composition, creating
favorable conditions for the development of nuisance,
toxic, or otherwise harmful algal blooms.
Low dissolved oxygen and formation of hypoxic or “dead”
zones (oxygen-depleted waters), which in turn can lead to
ecosystem collapse.
6
The scientifi c community is increasing its knowledge of how
eutrophication affects coastal ecosystems, yet the long-term
implications of increased nutrient fl uxes in our coastal waters
are currently not entirely known or understood. We do know
that eutrophication diminishes the ability of coastal ecosystems
to provide valuable ecosystem services such as tourism, recre-
ation, the provision of fi sh and shellfi sh for local communities,
sportfi shing, and commercial fi sheries. In addition, eutrophica-
tion can lead to reductions in local and regional biodiversity.
Today nearly half of the world’s population lives within 60 ki-
lometers of the coast, with many communities relying directly
on coastal ecosystems for their livelihoods.
7
This means that a
signifi cant portion of the world’s population is vulnerable to the
effects of eutrophication in their local coastal ecosystems.
Harmful Algal Blooms and Hypoxia. Two of the most acute and
commonly recognized symptoms of eutrophication are harmful
algal blooms and hypoxia.
Harmful algal blooms can cause fish kills, human illness
through shellfi sh poisoning, and death of marine mammals
and shore birds.
8
Harmful algal blooms are often referred to
as “red tides” or “brown tides” because of the appearance of
the water when these blooms occur. One red tide event, which
occurred near Hong Kong in 1998, wiped out 90 percent of
the entire stock of Hong Kong’s fi sh farms and resulted in an
estimated economic loss of $40 million USD.
9,10
Hypoxia, considered to be the most severe symptom of eutro-
phication, has escalated dramatically over the past 50 years,
increasing from about 10 documented cases in 1960 to at least
169 in 2007.
11,12
Hypoxia occurs when algae and other organ-
isms die, sink to the bottom, and are decomposed by bacteria,
using the available dissolved oxygen. Salinity and temperature
differences between surface and subsurface waters lead to
stratifi cation, limiting oxygen replenishment from surface
waters and creating conditions that can lead to the formation
of a hypoxic or “dead” zone.
13
Two of the most well-known hypoxic areas are the Gulf of
Mexico and the Black Sea. The Gulf of Mexico has a seasonal
hypoxic zone that forms every year in late summer. Its size
varies; in 2000, it was less than 5,000 km2, while in 2002 it
was approximately 22,000 km2 (or the size of the U.S. state of
Massachusetts). While the economic consequences of the Gulf
of Mexico dead zone are still unclear, concern over its increas-
ing size led to the formation of the Mississippi River/Gulf of
Mexico Watershed Nutrient Task Force in 1997 to develop a
strategy to reduce the fi ve-year running average areal extent of
the Gulf of Mexico hypoxic zone to less than 5,000 km2.
The Black Sea, which was once the largest dead zone in the
world, had 26 commercially viable fi sh species in the 1960s but
The fi rst comprehensive list of hypoxic zones was compiled by
Diaz and Rosenberg in 1995 and identifi ed 44 documented
hypoxic areas.
18
Twelve years later, there are 169 documented
hypoxic areas, a nearly four-fold increase. The list of hypoxic
areas assembled by Diaz was compiled from scientifi c litera-
ture and identifi ed the majority of documented hypoxic areas.
However, the list did not include areas with suspected—but
not documented—hypoxic events or systems that suffer from
other impacts of eutrophication such as nuisance or harmful
algal blooms, loss of subaquatic vegetation, and changes in
the structure of the benthic aquatic community (for example,
decline in biomass, changes in species composition, and loss
of diversity).
To supplement this list of hypoxic zones, the authors undertook
an extensive literature review to catalog systems experiencing
any symptoms of eutrophication, including—but not limited
to—hypoxia.
19
The eutrophic areas identifi ed were categorized
as:
Documented hypoxic areas. Areas with scientifi c evidence
that hypoxia was caused, at least in part, by nutrient
overenrichment. This category includes the most recent
list of hypoxic areas compiled by Diaz (excluding hypoxia
caused by natural upwelling of nutrients), as well as some
additional systems identifi ed by our research.
20
Areas of concern. Systems that exhibit effects of eutrophi-
cation, such as elevated nutrient levels, elevated chloro-
phyll a levels, harmful algal blooms, changes in the benthic
community, damage to coral reefs, and fi sh kills. These
systems are impaired by nutrients and are possibly at risk
of developing hypoxia. Some of the systems classifi ed as
areas of concern may already be experiencing hypoxia, but
lack conclusive scientifi c evidence of the condition.
Systems in recovery. Areas that once exhibited low dis-
solved oxygen levels and hypoxia, but are now improving.
For example, the Black Sea once experienced annual
hypoxic events, but is now in a state of recovery. Others,
like Boston Harbor in the United States and the Mersey
Estuary in the United Kingdom, also have improved
water quality resulting from better industrial and waste-
water controls.
WHERE ARE THE DATA INCONSISTENCIES AND GAPS?
The actual extent and prevalence of eutrophication in many
regions is only beginning to be studied. As a consequence, data
do not exist or are not publicly available for many areas that
may be suffering from the effects of eutrophication. In addi-
tion, the data that do exist are often inconsistent in terms of
parameters measured, indicators used, and the scale at which
data are reported.
Given the state of global data, the number of eutrophic and
hypoxic areas around the world is expected to be greater than
the 415 listed here. The most underrepresented region is Asia.
Asia has relatively few documented eutrophic and hypoxic
areas despite large increases in intensive farming methods,
industrial development, and population growth over the past
20 years. Africa, Latin America, and the Caribbean also have
few reliable sources of coastal water quality data, making it
diffi cult to assess the true level of eutrophication.
The scale at which data for eutrophic areas are reported var-
ies greatly. For example, red tides and other eutrophic events
are frequently recorded in the South China Sea, Yellow Sea,
and Bohai Sea. However, the actual extent of eutrophication
or hypoxia in specifi c bays and estuaries within these systems
is unknown. Therefore, these areas are coarsely recorded in
Figure 1 and most likely represent several affected bays and
estuaries along the Chinese coast. Conversely, within the
well-studied Chesapeake Bay system, there are 12 distinct and
documented eutrophic and hypoxic zones.
The United States, European Union, and Australia—all of which
have each undertaken comprehensive coastal surveys in the past
ve years—have the most comprehensive coastal data on eutro-
phication. However, even within the United States and Europe,
the quality, consistency, and availability of water quality data
varies. For example, in Europe, the coastal survey coordinated
through the Commission for the Protection of the Marine En-
vironment of the North-East Atlantic (OSPAR)
highlighted the
variability in quality and availability of monitoring data among
the various European countries.
21
Several coastal areas lacked
dissolved oxygen measures and many of the secondary effects
of eutrophication, such as fi sh kills and changes in the benthic
community, were not extensively monitored. The U.S. National
Oceanic and Atmospheric Agency’s (NOAA) National Estuarine
Eutrophication Assessment program, which conducted national
eutrophication surveys in 1999 and 2007, experienced data
issues similar to those encountered in the OSPAR survey. Of
the 141 U.S. estuaries evaluated in 2007, 30 percent lacked
adequate data for assessing their eutrophication status.
Most systems identifi ed as hypoxic or eutrophic also lack
detailed data on the sources of nutrient impairments and the
relative contribution of each source. Some systems that have
developed detailed nutrient budgets include the Chesapeake
only fi ve species by the 1980s.
14
The growth of the Black Sea
hypoxic zone was attributed to the intensifi cation of agriculture
in the former Soviet Union. It has been “in recovery” since
the economic collapse of Eastern Europe in the 1990s, which
resulted in signifi cant reductions in fertilizer use.
WHAT ARE THE SOURCES OF NUTRIENTS?
Agriculture, human sewage, urban runoff, industrial effl uent,
and fossil fuel combustion are the most common sources of
nutrients delivered to coastal systems. Among regions, there are
signifi cant variations in the relative importance of each nutrient
source. For example, in the United States and the European
Union, agricultural sources (particularly animal manure and
commercial fertilizers) are generally the primary contributors
to eutrophication, while sewage and industrial discharges,
which usually receive some treatment prior to discharge, are a
secondary source. However, in Latin America, Asia, and Africa,
wastewater from sewage and industry are often untreated and
may often be the primary contributors to eutrophication. It is
currently estimated that only 35 percent of wastewater in Asia
is treated, 14 percent in Latin America and the Caribbean, and
less than 1 percent in Africa.
15
Atmospheric sources of nitrogen are also recognized as a sig-
nifi cant contributor of nutrients in coastal areas.
16
Nitrogen
from fossil fuel combustion and volatilization from fertilizers
and manure is released into the atmosphere and redeposited
on land and in water by wind, snow, and rain. In the Chesa-
peake Bay in the mid-Atlantic region of the eastern United
States, atmospheric sources of nitrogen account for a third
of all controllable nitrogen that enters the Bay; similarly, in
the Baltic Sea in Europe, atmospheric nitrogen accounts for
a fourth of all controllable nitrogen.
WHERE ARE THE GLOBAL EUTROPHIC AND HYPOXIC
AREAS?
Our research identifi ed 415 eutrophic and hypoxic coastal
systems worldwide (Figure 1).
17
Of these, 169 are documented
hypoxic areas, 233 are areas of concern, and 13 are systems
in recovery.
The coastal areas reported as experiencing eutrophication are
steadily growing. This is because of the increasing prevalence
of eutrophication and advances in identifying and reporting
eutrophic conditions.
www.wri.org10 G Street, NE Washington, DC 20002
Tel: 202-729-7600 Fax: 202-729-7610
MARCH 2008
6WORLD RESOURCES INSTITUTEMarch 2008
WRI POLICY NOTE
WATER QUALITY: EUTROPHICATION AND HYPOXIA No. 1
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
5March 2008WORLD RESOURCES INSTITUTE
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
EUTROPHICATION AND
HYPOXIA IN COASTAL AREAS:
A GLOBAL ASSESSMENT OF
THE STATE OF KNOWLEDGE
MINDY SELMAN, SUZIE GREENHALGH, ROBERT DIAZ AND ZACHARY SUGG
Within the past 50 years, eutrophication—the overen-
richment of water by nutrients such as nitrogen and
phosphorus—has emerged as one of the leading causes of water
quality impairment. Our research identifi es over 415 areas
worldwide that are experiencing symptoms of eutrophication,
highlighting the global scale of the problem.
Recent coastal surveys of the United States and Europe found
that a staggering 78 percent of the assessed continental U.S.
coastal area and approximately 65 percent of Europe’s Atlantic
coast exhibit symptoms of eutrophication.
1,2
In other regions,
the lack of reliable data hinders the assessment of coastal
eutrophication. Nevertheless, trends in agricultural practices,
energy use, and population growth indicate that coastal eutro-
phication will be an ever-growing problem.
This policy note focuses on what is currently known about the
extent of eutrophication globally, and how to improve the state
of our knowledge to more accurately inform and drive policy
decisions for mitigating eutrophication. Complementary policy
notes will discuss in more detail the sources of nutrients and
actions that can be implemented to mitigate eutrophication.
Key Messages
Eutrophication—the overenrichment of waters by nutrients—threat-
ens and degrades many coastal ecosystems around the world. The two
most acute symptoms of eutrophication are hypoxia (or oxygen deple-
tion) and harmful algal blooms, which among other things can destroy
aquatic life in affected areas.
Of the 415 areas around the world identifi ed as experiencing some
form of eutrophication, 169 are hypoxic and only 13 systems are clas-
sifi ed as “systems in recovery.”
Mapping and research into the extent of eutrophication and its threats
to human health and ecosystem services are improving, but there is
still insuffi cient information in many regions of the world to establish
the actual extent of eutrophication or identify the sources of nutri-
ents. To develop effective policies to mitigate eutrophication, more
information is required on the extent of eutrophication, the sources of
nutrients, and the impact of eutrophication on ecosystems.
Recommendations
To improve knowledge of where eutrophication is occurring and its
impacts, environmental agencies or coastal authorities worldwide
need to proactively assess and monitor water quality, specifi cally those
variables commonly linked to eutrophication such as nutrient levels
and dissolved oxygen. In addition, internationally accepted methods
and defi nitions for assessing and classifying eutrophic coastal wa-
ters—including proxies for eutrophication—need to be developed.
In Asia, Africa, and Latin America, environmental agencies or coastal
authorities should:
1. Undertake systematic and routine assessments of coastal areas,
particularly those exhibiting symptoms of eutrophication.
2. Develop transparent and public reporting procedures for tracking
the occurrence of eutrophication and hypoxia, as well as monitoring
their impact on ecosystem health.
3. Develop and adopt decision-support tools—such as nutrient bud-
gets and water quality models—that can facilitate the development
of appropriate local and regional responses to eutrophication.
In the United States, Europe, and Australia, environmental agencies
or coastal authorities should:
1. Continue coastal zone assessments.
2. Ensure that eutrophication assessment methodologies are being
consistently applied.
3. Enhance existing decision-support tools and develop tools for those
areas where none currently exist.
Bay, Baltic Sea, Black Sea, Gulf of Mexico (Mississippi-Atcha-
falaya plume), and Tampa Bay. The absence of detailed nutri-
ent budgets for the majority of eutrophic and hypoxic systems
around the world highlights the lack of concerted research
efforts in these areas, compromising the ability to effectively
address and manage nutrient overenrichment.
HOW DO WE IMPROVE THE STATE OF KNOWLEDGE?
To better assess the global, regional, and local extent of eutrophi-
cation, we need more and better data. Improving our knowledge
of where eutrophication is occurring, the sources contributing
to the problem, and the effects of eutrophication on marine
ecosystems and human communities ultimately infl uences the
ability of policy-makers to decide where and how resources can
be used most effectively to address eutrophication.
Closing the knowledge gap requires increased and improved
water quality monitoring and assessment of estuarine and
coastal waters. Without this information, communities cannot
effectively manage coastal ecosystems and address land-based
sources of pollution. Specifically, time series monitoring
data—on nutrient levels, chlorophyll a (as an indicator of the
presence of phytoplankton), and dissolved oxygen—as well
as eutrophication response parameters—such as loss of sub-
aquatic vegetation, fi sh kills, and algal blooms—are needed to
evaluate the extent and degree of eutrophication. Moreover,
widespread use and adoption of methods to classify and defi ne
eutrophic waters (such as the ones developed by NOAA and
OSPAR) are needed to increase the transparency, consistency,
and comparability of water quality information. For example,
currently no common defi nition of “hypoxia” exists and the
interpretation of what is hypoxic can vary widely from place
to place.
In countries or regions where robust and systematic monitor-
ing programs are unlikely to be implemented due to limited
resources, it would be benefi cial to develop credible and con-
sistent proxies for water quality (such as turbidity or sulfi de
smell) that could be used to identify likely eutrophic areas.
Finally, decision support tools that enable researchers and
policy-makers to formulate appropriate responses to eutro-
phication need to be continually developed and more widely
adopted by local and regional entities. Such tools include:
Watershed models to assess nutrient delivery and ecosys-
tem impacts;
Nutrient balance assessments to determine the sources of
nutrients and relative contribution of each source;
Regional and international online information portals
for compiling and sharing water quality information and
research;
Nutrient loss estimation tools; and
Tools to help assess the effectiveness of alternative sce-
narios for reducing nutrient inputs.
Implementation of these tools is especially needed to estimate
coastal impacts and target appropriate policy responses in coun-
tries and regions where actual monitoring data are scarce.
Eutrophication is an issue that requires greater attention by gov-
ernments and society in general. Left untouched, it may have
dire consequences for many ecosystems, the food webs that they
support, and the livelihoods of the populations that depend on
them. To get a better grasp on the immediate and long-term
consequences of eutrophication, we need more resources and
better information. Improving our knowledge and information
on eutrophication is the fi rst step in developing robust policy
measures to begin reversing or halting its impacts.
ABOUT THE AUTHORS
Mindy Selman is a senior associate in the People and
Ecosystems Program of the World Resources Institute.
Ph: +1-202-729 7644. Email: mselman@wri.org
Suzie Greenhalgh is a senior economist at Landcare
Research New Zealand Ltd. Ph: +64-9-574 4132.
Email: greenhalghs@landcareresearch.co.nz
Robert Diaz is a professor of marine science at the College
of William and Mary, Virginia Institute of Marine Science.
Ph: +1-804-684 7364. Email: diaz@vims.edu
Zachary Sugg is a research analyst with the People and
Ecosystems Program of the World Resources Institute.
Ph: +1-202-729 7605. Email: zsugg@wri.org
ACKNOWLEDGMENTS
The authors are grateful for the contributions provided by
Donald Anderson, James Galloway, Paul Harrison, Laurence
Mee, Qian Yi, and Nancy Rabalais, who served on a WRI
eutrophication advisory panel. The authors would also like to
acknowledge Kersey Sturdivant for his research assistance in
identifying areas of eutrophication. In addition, the authors
thank Craig Hanson, Lauretta Burke, Amy Cassara, Dan
Tunstall, Laurence Mee, and James Galloway for reviewing
earlier drafts of this paper. Finally, we extend our thanks to
the Linden Trust for Conservation and the David and Lucile
Packard Foundation for their support of this research.
NOTES
1. See Bricker, S. B., Longstaff, W. Dennison, A. Jones, K. Boicourt, C.
Wicks, and J. Woerner. 2007. Effects of Nutrient Enrichment in the
Nation’s Estuaries: A Decade of Change. NOAA Coastal Ocean Program
Decision Analysis Series No. 26. Silver Spring, MD: National Centers
for Coastal Ocean Science. Online at: http://ccma.nos.noaa.gov/publica-
tions/eutroupdate/
2. See OSPAR Commission. 2003. OSPAR integrated report 2003 on the
eutrophication status. London, U.K.: OSPAR.
3. See Howarth, R. and K. Ramakrrshna. 2005. “Nutrient Management.”
In K. Chopra, R. Leemans, P. Kumar, and H. Simons, eds. Ecosystems
and Human Wellbeing: Policy Responses. Volume 3 of the Millennium
Ecosystem Assessment (MA). Washington, DC: Island Press.
4. See National Oceanic and Atmospheric Administration (NOAA). “Global
Warming: Frequently asked questions.” Available at: http://lwf.ncdc.
noaa.gov/oa/climate/globalwarming.html. (accessed January 15, 2008)
5. See Galloway, J.N, J.D. Aber,, J.W. Erisman, S.P. Seitzinger, R.W.
Howarth, E.B. Cowling, and B.J. Cosby. 2003. “The Nitrogen Cascade.”
Bioscience 53( 4): 341–356
6. For a discussion on the impacts of eutrophication on coastal ecosystems,
see Mee, L. 2006. “Reviving Dead Zones.” Scientifi c American 295 (5):
79–85.
7. See: UN Chronicle Online Edition. “Risks, Untreated Sewage Threat-
ens Seas, Coastal Population.” http://www.un.org/Pubs/chronicle/2003/
issue1/0103p39.html. (accessed January 15, 2008)
8. Harmful algal blooms refer to several species of algae that produce tox-
ins that are harmful to aquatic life. See Anderson, D. M., P. M. Gilbert,
and J. M. Burkholder. 2002. “Harmful Algal Blooms and Eutrophica-
tion: Nutrient Sources, Composition, and Consequences.” Estuaries 25
(4b): 704–726.
9. See: Terra Daily Online Edition. “Hong Kong red tide spreads,” (June
10, 2007). http://www.terradaily.com/reports/Hong_Kong_Red_Tide_
Spreads_999.html (accessed February 8, 2008).
10. See Lu, S., and I. J. Hodgkiss. 2004. “Harmful algal bloom causative
collected from Hong Kong waters.” Hydrobiologia.512(1-3): 231-238
11. Hypoxia is generally defi ned as having a dissolved oxygen concentration
of 2.0 milligrams per liter or less.
12. See Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
13. See Rabalais, N. N., and R. E. Turner. 2001. Coastal hypoxia conse-
quences for living resources and ecosystems. Washington, DC: American
Geophysical Union.
14. See Europe Now|Next. “Is the Black Sea recovering?” http://www.eu-
rope.culturebase.net/contribution.php?media=307 (accessed December
30, 2008)
15. See Howarth, R. and K. Ramakrrshna. 2005. “Nutrient Management.”
In K. Chopra, R. Leemans, P. Kumar, and H. Simons, eds. Ecosystems
and Human Wellbeing: Policy Responses. Volume 3 of the Millennium
Ecosystem Assessment (MA). Washington, DC: Island Press.
16. See Spokes, L. J., and T. D. Jickells. 2005. “Is the atmosphere really an
important source of reactive nitrogen to coastal waters?” Continental
Shelf Research 25: 2022–2035.
17. Region-specifi c maps as well as the data used to create these maps is
made available on WRI’s website, www.wri.org/project/water-quality.
18. See Diaz, R. and R. Rosenburg. 1995. “Marine benthic hypoxia: a
review of its ecological effects and the behavioural responses of benthic
macrofauna.” Oceanography and Marine Biology: an Annual Review 33:
245–303.
19. The primary data sources include:
Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
Bricker, S. B., Longstaff, W. Dennison, A. Jones, K. Boicourt, C. Wicks,
and J. Woerner. 2007. Effects of Nutrient Enrichment in the Nation’s
Estuaries: A Decade of Change. NOAA Coastal Ocean Program Decision
Analysis Series No. 26. Silver Spring, MD: National Centers for Coastal
Ocean Science. Online at: http://ccma.nos.noaa.gov/publications/eu-
troupdate/.
OSPAR Commission. 2003. OSPAR integrated report 2003 on the eutro-
phication status. London, UK: OSPAR.
OzEstuaries. 2005. “Anoxic and Hypoxic Events.” Online at: http://www.
ozestuaries. org/indicators/anoxic_hypoxic_events.jsp (August, 2005).
United Nations Environment Program (UNEP). 2006. Challenges to
International Waters – Regional Assessments in a Global Perspective.
Nairobi, Kenya: United Nations.
20. See Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
21. OSPAR called for the uniform assessment of coastal waters by signatory
countries. Signatory countries to the 1992 Oslo-Paris Convention for
the Protection of the Marine Environment of the North-East Atlantic
(OSPAR Convention) include Belgium, Denmark, France, Germany,
Ireland, The Netherlands, Norway, Portugal, Spain, Sweden, and the
United Kingdom.
ABOUT WRI
The World Resources Institute is an environ-
mental think tank that goes beyond research
to fi nd practical ways to protect the Earth and
improve people’s lives. Our mission is to move
human society to live in ways that protect the
Earth’s environment and its capacity to pro-
vide for the needs and aspirations of current
and future generations.
Forthcoming publications in this series include:
1. Eutrophication: Sources and Drivers of Nutrient Pollution
2. Eutrophication: A Policy Framework for Addressing
Nutrient Pollution
Please visit www.wri.org/policynotes for links to available
Policy Notes.
BAR CODE TO COME
Red algal bloom at Leigh, near Cape Rodney, NZ.
PHOTO BY MIRIAM GODFREY. USED BY PERMISSION OF NIWA SCIENCE.
www.wri.org10 G Street, NE Washington, DC 20002
Tel: 202-729-7600 Fax: 202-729-7610
MARCH 2008
6WORLD RESOURCES INSTITUTEMarch 2008
WRI POLICY NOTE
WATER QUALITY: EUTROPHICATION AND HYPOXIA No. 1
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
5March 2008WORLD RESOURCES INSTITUTE
POLICY NOTE: Eutrophication and Hypoxia in Coastal Areas
EUTROPHICATION AND
HYPOXIA IN COASTAL AREAS:
A GLOBAL ASSESSMENT OF
THE STATE OF KNOWLEDGE
MINDY SELMAN, SUZIE GREENHALGH, ROBERT DIAZ AND ZACHARY SUGG
Within the past 50 years, eutrophication—the overen-
richment of water by nutrients such as nitrogen and
phosphorus—has emerged as one of the leading causes of water
quality impairment. Our research identifi es over 415 areas
worldwide that are experiencing symptoms of eutrophication,
highlighting the global scale of the problem.
Recent coastal surveys of the United States and Europe found
that a staggering 78 percent of the assessed continental U.S.
coastal area and approximately 65 percent of Europe’s Atlantic
coast exhibit symptoms of eutrophication.
1,2
In other regions,
the lack of reliable data hinders the assessment of coastal
eutrophication. Nevertheless, trends in agricultural practices,
energy use, and population growth indicate that coastal eutro-
phication will be an ever-growing problem.
This policy note focuses on what is currently known about the
extent of eutrophication globally, and how to improve the state
of our knowledge to more accurately inform and drive policy
decisions for mitigating eutrophication. Complementary policy
notes will discuss in more detail the sources of nutrients and
actions that can be implemented to mitigate eutrophication.
Key Messages
Eutrophication—the overenrichment of waters by nutrients—threat-
ens and degrades many coastal ecosystems around the world. The two
most acute symptoms of eutrophication are hypoxia (or oxygen deple-
tion) and harmful algal blooms, which among other things can destroy
aquatic life in affected areas.
Of the 415 areas around the world identifi ed as experiencing some
form of eutrophication, 169 are hypoxic and only 13 systems are clas-
sifi ed as “systems in recovery.”
Mapping and research into the extent of eutrophication and its threats
to human health and ecosystem services are improving, but there is
still insuffi cient information in many regions of the world to establish
the actual extent of eutrophication or identify the sources of nutri-
ents. To develop effective policies to mitigate eutrophication, more
information is required on the extent of eutrophication, the sources of
nutrients, and the impact of eutrophication on ecosystems.
Recommendations
To improve knowledge of where eutrophication is occurring and its
impacts, environmental agencies or coastal authorities worldwide
need to proactively assess and monitor water quality, specifi cally those
variables commonly linked to eutrophication such as nutrient levels
and dissolved oxygen. In addition, internationally accepted methods
and defi nitions for assessing and classifying eutrophic coastal wa-
ters—including proxies for eutrophication—need to be developed.
In Asia, Africa, and Latin America, environmental agencies or coastal
authorities should:
1. Undertake systematic and routine assessments of coastal areas,
particularly those exhibiting symptoms of eutrophication.
2. Develop transparent and public reporting procedures for tracking
the occurrence of eutrophication and hypoxia, as well as monitoring
their impact on ecosystem health.
3. Develop and adopt decision-support tools—such as nutrient bud-
gets and water quality models—that can facilitate the development
of appropriate local and regional responses to eutrophication.
In the United States, Europe, and Australia, environmental agencies
or coastal authorities should:
1. Continue coastal zone assessments.
2. Ensure that eutrophication assessment methodologies are being
consistently applied.
3. Enhance existing decision-support tools and develop tools for those
areas where none currently exist.
Bay, Baltic Sea, Black Sea, Gulf of Mexico (Mississippi-Atcha-
falaya plume), and Tampa Bay. The absence of detailed nutri-
ent budgets for the majority of eutrophic and hypoxic systems
around the world highlights the lack of concerted research
efforts in these areas, compromising the ability to effectively
address and manage nutrient overenrichment.
HOW DO WE IMPROVE THE STATE OF KNOWLEDGE?
To better assess the global, regional, and local extent of eutrophi-
cation, we need more and better data. Improving our knowledge
of where eutrophication is occurring, the sources contributing
to the problem, and the effects of eutrophication on marine
ecosystems and human communities ultimately infl uences the
ability of policy-makers to decide where and how resources can
be used most effectively to address eutrophication.
Closing the knowledge gap requires increased and improved
water quality monitoring and assessment of estuarine and
coastal waters. Without this information, communities cannot
effectively manage coastal ecosystems and address land-based
sources of pollution. Specifically, time series monitoring
data—on nutrient levels, chlorophyll a (as an indicator of the
presence of phytoplankton), and dissolved oxygen—as well
as eutrophication response parameters—such as loss of sub-
aquatic vegetation, fi sh kills, and algal blooms—are needed to
evaluate the extent and degree of eutrophication. Moreover,
widespread use and adoption of methods to classify and defi ne
eutrophic waters (such as the ones developed by NOAA and
OSPAR) are needed to increase the transparency, consistency,
and comparability of water quality information. For example,
currently no common defi nition of “hypoxia” exists and the
interpretation of what is hypoxic can vary widely from place
to place.
In countries or regions where robust and systematic monitor-
ing programs are unlikely to be implemented due to limited
resources, it would be benefi cial to develop credible and con-
sistent proxies for water quality (such as turbidity or sulfi de
smell) that could be used to identify likely eutrophic areas.
Finally, decision support tools that enable researchers and
policy-makers to formulate appropriate responses to eutro-
phication need to be continually developed and more widely
adopted by local and regional entities. Such tools include:
Watershed models to assess nutrient delivery and ecosys-
tem impacts;
Nutrient balance assessments to determine the sources of
nutrients and relative contribution of each source;
Regional and international online information portals
for compiling and sharing water quality information and
research;
Nutrient loss estimation tools; and
Tools to help assess the effectiveness of alternative sce-
narios for reducing nutrient inputs.
Implementation of these tools is especially needed to estimate
coastal impacts and target appropriate policy responses in coun-
tries and regions where actual monitoring data are scarce.
Eutrophication is an issue that requires greater attention by gov-
ernments and society in general. Left untouched, it may have
dire consequences for many ecosystems, the food webs that they
support, and the livelihoods of the populations that depend on
them. To get a better grasp on the immediate and long-term
consequences of eutrophication, we need more resources and
better information. Improving our knowledge and information
on eutrophication is the fi rst step in developing robust policy
measures to begin reversing or halting its impacts.
ABOUT THE AUTHORS
Mindy Selman is a senior associate in the People and
Ecosystems Program of the World Resources Institute.
Ph: +1-202-729 7644. Email: mselman@wri.org
Suzie Greenhalgh is a senior economist at Landcare
Research New Zealand Ltd. Ph: +64-9-574 4132.
Email: greenhalghs@landcareresearch.co.nz
Robert Diaz is a professor of marine science at the College
of William and Mary, Virginia Institute of Marine Science.
Ph: +1-804-684 7364. Email: diaz@vims.edu
Zachary Sugg is a research analyst with the People and
Ecosystems Program of the World Resources Institute.
Ph: +1-202-729 7605. Email: zsugg@wri.org
ACKNOWLEDGMENTS
The authors are grateful for the contributions provided by
Donald Anderson, James Galloway, Paul Harrison, Laurence
Mee, Qian Yi, and Nancy Rabalais, who served on a WRI
eutrophication advisory panel. The authors would also like to
acknowledge Kersey Sturdivant for his research assistance in
identifying areas of eutrophication. In addition, the authors
thank Craig Hanson, Lauretta Burke, Amy Cassara, Dan
Tunstall, Laurence Mee, and James Galloway for reviewing
earlier drafts of this paper. Finally, we extend our thanks to
the Linden Trust for Conservation and the David and Lucile
Packard Foundation for their support of this research.
NOTES
1. See Bricker, S. B., Longstaff, W. Dennison, A. Jones, K. Boicourt, C.
Wicks, and J. Woerner. 2007. Effects of Nutrient Enrichment in the
Nation’s Estuaries: A Decade of Change. NOAA Coastal Ocean Program
Decision Analysis Series No. 26. Silver Spring, MD: National Centers
for Coastal Ocean Science. Online at: http://ccma.nos.noaa.gov/publica-
tions/eutroupdate/
2. See OSPAR Commission. 2003. OSPAR integrated report 2003 on the
eutrophication status. London, U.K.: OSPAR.
3. See Howarth, R. and K. Ramakrrshna. 2005. “Nutrient Management.”
In K. Chopra, R. Leemans, P. Kumar, and H. Simons, eds. Ecosystems
and Human Wellbeing: Policy Responses. Volume 3 of the Millennium
Ecosystem Assessment (MA). Washington, DC: Island Press.
4. See National Oceanic and Atmospheric Administration (NOAA). “Global
Warming: Frequently asked questions.” Available at: http://lwf.ncdc.
noaa.gov/oa/climate/globalwarming.html. (accessed January 15, 2008)
5. See Galloway, J.N, J.D. Aber,, J.W. Erisman, S.P. Seitzinger, R.W.
Howarth, E.B. Cowling, and B.J. Cosby. 2003. “The Nitrogen Cascade.”
Bioscience 53( 4): 341–356
6. For a discussion on the impacts of eutrophication on coastal ecosystems,
see Mee, L. 2006. “Reviving Dead Zones.” Scientifi c American 295 (5):
79–85.
7. See: UN Chronicle Online Edition. “Risks, Untreated Sewage Threat-
ens Seas, Coastal Population.” http://www.un.org/Pubs/chronicle/2003/
issue1/0103p39.html. (accessed January 15, 2008)
8. Harmful algal blooms refer to several species of algae that produce tox-
ins that are harmful to aquatic life. See Anderson, D. M., P. M. Gilbert,
and J. M. Burkholder. 2002. “Harmful Algal Blooms and Eutrophica-
tion: Nutrient Sources, Composition, and Consequences.” Estuaries 25
(4b): 704–726.
9. See: Terra Daily Online Edition. “Hong Kong red tide spreads,” (June
10, 2007). http://www.terradaily.com/reports/Hong_Kong_Red_Tide_
Spreads_999.html (accessed February 8, 2008).
10. See Lu, S., and I. J. Hodgkiss. 2004. “Harmful algal bloom causative
collected from Hong Kong waters.” Hydrobiologia.512(1-3): 231-238
11. Hypoxia is generally defi ned as having a dissolved oxygen concentration
of 2.0 milligrams per liter or less.
12. See Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
13. See Rabalais, N. N., and R. E. Turner. 2001. Coastal hypoxia conse-
quences for living resources and ecosystems. Washington, DC: American
Geophysical Union.
14. See Europe Now|Next. “Is the Black Sea recovering?” http://www.eu-
rope.culturebase.net/contribution.php?media=307 (accessed December
30, 2008)
15. See Howarth, R. and K. Ramakrrshna. 2005. “Nutrient Management.”
In K. Chopra, R. Leemans, P. Kumar, and H. Simons, eds. Ecosystems
and Human Wellbeing: Policy Responses. Volume 3 of the Millennium
Ecosystem Assessment (MA). Washington, DC: Island Press.
16. See Spokes, L. J., and T. D. Jickells. 2005. “Is the atmosphere really an
important source of reactive nitrogen to coastal waters?” Continental
Shelf Research 25: 2022–2035.
17. Region-specifi c maps as well as the data used to create these maps is
made available on WRI’s website, www.wri.org/project/water-quality.
18. See Diaz, R. and R. Rosenburg. 1995. “Marine benthic hypoxia: a
review of its ecological effects and the behavioural responses of benthic
macrofauna.” Oceanography and Marine Biology: an Annual Review 33:
245–303.
19. The primary data sources include:
Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
Bricker, S. B., Longstaff, W. Dennison, A. Jones, K. Boicourt, C. Wicks,
and J. Woerner. 2007. Effects of Nutrient Enrichment in the Nation’s
Estuaries: A Decade of Change. NOAA Coastal Ocean Program Decision
Analysis Series No. 26. Silver Spring, MD: National Centers for Coastal
Ocean Science. Online at: http://ccma.nos.noaa.gov/publications/eu-
troupdate/.
OSPAR Commission. 2003. OSPAR integrated report 2003 on the eutro-
phication status. London, UK: OSPAR.
OzEstuaries. 2005. “Anoxic and Hypoxic Events.” Online at: http://www.
ozestuaries. org/indicators/anoxic_hypoxic_events.jsp (August, 2005).
United Nations Environment Program (UNEP). 2006. Challenges to
International Waters – Regional Assessments in a Global Perspective.
Nairobi, Kenya: United Nations.
20. See Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. “A global perspec-
tive on the effects of eutrophication and hypoxia on aquatic biota.” In
G. L. Rupp and M. D. White, eds. Proceedings of the 7th International
Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn,
Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protec-
tion Agency, Ecosystems Research Division (EPA 600/R-04/049).
21. OSPAR called for the uniform assessment of coastal waters by signatory
countries. Signatory countries to the 1992 Oslo-Paris Convention for
the Protection of the Marine Environment of the North-East Atlantic
(OSPAR Convention) include Belgium, Denmark, France, Germany,
Ireland, The Netherlands, Norway, Portugal, Spain, Sweden, and the
United Kingdom.
ABOUT WRI
The World Resources Institute is an environ-
mental think tank that goes beyond research
to fi nd practical ways to protect the Earth and
improve people’s lives. Our mission is to move
human society to live in ways that protect the
Earth’s environment and its capacity to pro-
vide for the needs and aspirations of current
and future generations.
Forthcoming publications in this series include:
1. Eutrophication: Sources and Drivers of Nutrient Pollution
2. Eutrophication: A Policy Framework for Addressing
Nutrient Pollution
Please visit www.wri.org/policynotes for links to available
Policy Notes.
Red algal bloom at Leigh, near Cape Rodney, NZ.
PHOTO BY MIRIAM GODFREY. USED BY PERMISSION OF NIWA SCIENCE.
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Increasing inputs of reactive nitrogen have led to excessive phytoplankton growth in some coastal waters. Until recently, rivers were thought to be the most important nitrogen source but we now know that atmospheric inputs are large and can equal, or exceed, those from the rivers. These atmospheric nitrogen compounds have both agricultural sources (ammonia emitted from animal wastes) and combustion sources (nitrate derived from NOx emitted by vehicles and power stations). Our hypothesis is that atmospheric nitrogen deposition in summer to nutrient depleted, well lit, surface waters in coastal seas stimulates phytoplankton blooms. This paper summarises and compares studies conducted in the North Sea, the North East Atlantic Ocean and the Kattegat Sea. Budgeting approaches imply that the atmosphere can, under certain meteorological conditions and over short time periods, provide enough nitrogen to support a large increase in phytoplankton growth. This is not true in all areas and at all times and this emphasises the highly episodic nature of atmospheric deposition. However, productivity-based approaches suggest that atmospheric nitrogen inputs have little effect on phytoplankton growth. This may be because productivity in the North Sea and the Kattegat is controlled by internal recycling of nitrogen, even in the summer when inorganic nitrogen levels are very low. Over longer time scales, atmospheric inputs do increase the overall nitrogen stock in the water column. Reducing the input of nitrogen from the atmosphere will, therefore, reduce total nitrogen loads to coastal seas and hence may decrease eutrophication problems.
Effects of Nutrient Enrichment in the Nation's Estuaries: A Decade of Change. NOAA Coastal Ocean Program Decision Analysis Series No. 26. Silver Spring, MD: National Centers for Coastal Ocean Science
  • J Wicks
  • Woerner
Wicks, and J. Woerner. 2007. Effects of Nutrient Enrichment in the Nation's Estuaries: A Decade of Change. NOAA Coastal Ocean Program Decision Analysis Series No. 26. Silver Spring, MD: National Centers for Coastal Ocean Science. Online at: http://ccma.nos.noaa.gov/publica- tions/eutroupdate/
For a discussion on the impacts of eutrophication on coastal ecosystems, see Reviving Dead Zones
  • L Mee
For a discussion on the impacts of eutrophication on coastal ecosystems, see Mee, L. 2006. " Reviving Dead Zones. " Scientifi c American 295 (5): 79–85.
Harmful algal bloom causative collected from Hong Kong waters
  • See Lu
  • I J Hodgkiss
See Lu, S., and I. J. Hodgkiss. 2004. "Harmful algal bloom causative collected from Hong Kong waters." Hydrobiologia.512(1-3): 231-238
A global perspective on the effects of eutrophication and hypoxia on aquatic biota
  • See Diaz
  • J Nestlerode
  • M L Diaz
See Diaz, R. J., J. Nestlerode, and M. L. Diaz. 2004. "A global perspective on the effects of eutrophication and hypoxia on aquatic biota." In G. L. Rupp and M. D. White, eds. Proceedings of the 7th International Symposium on Fish Physiology, Toxicology, and Water Quality, Tallinn, Estonia, May 12-15, 2003. Athens, Georgia: U.S. Environmental Protection Agency, Ecosystems Research Division (EPA 600/R-04/049).
Coastal hypoxia consequences for living resources and ecosystems
  • See Rabalais
  • R E Turner
See Rabalais, N. N., and R. E. Turner. 2001. Coastal hypoxia consequences for living resources and ecosystems. Washington, DC: American Geophysical Union.
Risks, Untreated Sewage Threatens Seas, Coastal Population
See: UN Chronicle Online Edition. "Risks, Untreated Sewage Threatens Seas, Coastal Population." http://www.un.org/Pubs/chronicle/2003/ issue1/0103p39.html. (accessed January 15, 2008)