ArticlePDF AvailableLiterature Review

Abstract and Figures

Beneath the waves, oxygen disappears As plastic waste pollutes the oceans and fish stocks decline, unseen below the surface another problem grows: deoxygenation. Breitburg et al. review the evidence for the downward trajectory of oxygen levels in increasing areas of the open ocean and coastal waters. Rising nutrient loads coupled with climate change—each resulting from human activities—are changing ocean biogeochemistry and increasing oxygen consumption. This results in destabilization of sediments and fundamental shifts in the availability of key nutrients. In the short term, some compensatory effects may result in improvements in local fisheries, such as in cases where stocks are squeezed between the surface and elevated oxygen minimum zones. In the longer term, these conditions are unsustainable and may result in ecosystem collapses, which ultimately will cause societal and economic harm. Science , this issue p. eaam7240
Content may be subject to copyright.
Declining oxygen in the global ocean
and coastal waters
Denise Breitburg,*Lisa A. Levin, Andreas Oschlies, Marilaure Grégoire,
Francisco P. Chavez, Daniel J. Conley, Véronique Garçon, Denis Gilbert,
Dimitri Gutiérrez, Kirsten Isensee, Gil S. Jacinto, Karin E. Limburg, Ivonne Montes,
S. W. A. Naqvi, Grant C. Pitcher, Nancy N. Rabalais, Michael R. Roman,
Kenneth A. Rose, Brad A. Seibel, Maciej Telszewski, Moriaki Yasuhara, Jing Zhang
BACKGROUND: Oxygen concentrations in
both the open ocean and coastal waters have
been declining since at least the middle of the
20th century. This oxygen loss, or deoxygenation,
is one of the most important changes occurring
in an ocean increasingly modified by human
activities that have raised temperatures, CO
levels, and nutrient inputs and have altered the
abundances and distributions of marine species.
Oxygen is fundamental to biological and bio-
geochemical processes in the ocean. Its decline
can cause major changes in ocean productivity,
biodiversity, and biogeochemical cycles. Analy-
ses of direct measurements at sites around the
world indicate that oxygen-minimum zones in
the open ocean have expanded by several million
square kilometers and that hundreds of coast-
al sites now have oxygen concentrations low
enough to limit the distribution and abundance
of animal populations and alter the cycling of
important nutrients.
ADVANCES: In the open ocean, global warm-
ing, which is primarily caused by increased
greenhouse gas emissions, is considered the
primary cause of ongoing deoxygenation. Nu-
merical models project further oxygen declines
during the 21st century, even with ambitious
emission reductions. Rising global temperatures
decrease oxygen solubility in water, increase
the rate of oxygen consumption via respira-
tion, and are predicted to reduce the introduc-
tion of oxygen from the atmosphere and surface
waters into the ocean interior by increasing
stratification and weakening ocean overturn-
ing circulation.
In estuaries and other coastal systems strongly
influenced by their watershed, oxygen declines
have been caused by increased loadings of nu-
trients (nitrogen and phosphorus) and organic
matter, primarily from agriculture; sewage; and
the combustion of fossil fuels. In many regions,
further increases in nitrogen discharges to coast-
al waters are projected as human populations
and agricultural production rise. Climate change
exacerbates oxygen decline in coastal systems
through similar mechanisms as those in the
open ocean, as well as by increasing nutrient
delivery from watersheds that will experience
increased precipitation.
production of N
O, a potent greenhouse gas;
reduce eukaryote biodiversity; alter the structure
of food webs; and negatively affect food secu-
rity and livelihoods. Both acidification and in-
creasing temperature are mechanistically linked
with the process of deoxygenation and combine
with low-oxygen conditions to affect biogeo-
chemical, physiological, and
ecological processes. How-
ever, an important paradox
to consider in predicting
large-scale effects of future
deoxygenation is that high
levels of productivity in
nutrient-enriched coastal systems and upwell-
ing areas associated with oxygen-minimum zones
also support some of the worldsmostprolific
OUTLOOK: Major advances have been made
toward understanding patterns, drivers, and
consequences of ocean deoxygenation, but there
is a need to improve predictions at large spatial
and temporal scales important to ecosystem ser-
vices provided by the ocean. Improved numerical
models of oceanographic processes that control
oxygen depletion and the large-scale influence
of altered biogeochemical cycles are needed
to better predict the magnitude and spatial pat-
terns of deoxygenation in the open ocean, as
well as feedbacks to climate. Developing and
verifying the next generation of these models
will require increased in situ observations and
improved mechanistic understanding on a va-
riety of scales. Models useful for managing
nutrient loads can simulate oxygen loss in coast-
al waters with some skill, but their ability to
project future oxygen loss is often hampered
by insufficient data and climate model projec-
tions on drivers at appropriate temporal and
spatial scales. Predicting deoxygenation-induced
changes in ecosystem services and human wel-
fare requires scaling effects that are measured
on individual organisms to populations, food
webs, and fisheries stocks; considering com-
bined effects of deoxygenation and other ocean
stressors; and placing an increased research
emphasis on developing nations. Reducing the
impacts of other stressors may provide some
protection to species negatively affected by low-
oxygen conditions. Ultimately, though, limiting
deoxygenation and its negative effects will ne-
cessitate a substantial global decrease in green-
house gas emissions, as well as reductions in
nutrient discharges to coastal waters.
Breitburg et al., Science 359, 46 (2018) 5 January 2018 1of1
The list of author affiliations is available in the full article online.
*Corresponding author. Email:
Cite this article as D. Breitburg et al., Science 359, eaam7240
(2018). DOI: 10.1126/science.aam7240
Low and declining oxygen levels in the open ocean and coastal waters affect processes
ranging from biogeochemistry to food security. The global map indicates coastal sites
where anthropogenic nutrients have exacerbated or caused O
declines to <2 mg liter
(<63 mmol liter
) (red dots), as well as ocean oxygen-minimum zones at 300 m of depth
(blue shaded regions). [Map created from data provided by R. Diaz, updated by members of
the GO
NE network, and downloaded from the World Ocean Atlas 2009].
Read the full article
at http://dx.doi.
on January 4, 2018 from
Declining oxygen in the global ocean
and coastal waters
Denise Breitburg,
*Lisa A. Levin,
Andreas Oschlies,
Marilaure Grégoire,
Francisco P. Chavez,
Daniel J. Conley,
Véronique Garçon,
Denis Gilbert,
Dimitri Gutiérrez,
Kirsten Isensee,
Gil S. Jacinto,
Karin E. Limburg,
Ivonne Montes,
S. W. A. Naqvi,
Grant C. Pitcher,
Nancy N. Rabalais,
Michael R. Roman,
Kenneth A. Rose,
Brad A. Seibel,
Maciej Telszewski,
Moriaki Yasuhara,
Jing Zhang
Oxygen is fundamental to life. Not only is it essential for the survival of individual animals,
but it regulates global cycles of major nutrients and carbon. The oxygen content of the
open ocean and coastal waters has been declining for at least the past half-century, largely
because of human activities that have increased global temperatures and nutrients
discharged to coastal waters. These changes have accelerated consumption of oxygen by
microbial respiration, reduced solubility of oxygen in water, and reduced the rate of oxygen
resupply from the atmosphere to the ocean interior, with a wide range of biological and
ecological consequences. Further research is needed to understand and predict long-term,
global- and regional-scale oxygen changes and their effects on marine and estuarine
fisheries and ecosystems.
Oxygen levels have been decreasing in the
open ocean and coastal waters since at least
the middle of the 20th century (13). This
ocean deoxygenation ranks among the most
important changes occurring in marine eco-
systems (1,46) (Figs. 1 and 2). The oxygen content
of the ocean constrains productivity, biodiversity,
and biogeochemical cycles. Major extinction events
in Earths history have been associated with warm
climates and oxygen-deficient oceans (7), and un-
der current trajectories, anthropogenic activities
coulddrive the ocean towardwide spread oxygen
deficiency within the next thousand years (8). In
this Review, we refer to coastal watersas systems
that are strongly influenced by their watershed,
and the open oceanas waters in which such in-
fluences are secondary.
The open ocean lost an estimated 2%, or 4.8 ±
2.1 petamoles (77 billion metric tons), of its oxy-
gen over the past 50 years (9). Open-ocean oxygen-
minimum zones (OMZs) have expanded by an
area about the size of the European Union (4.5 mil-
lion km
,basedonwaterwith<70mmol kg
gen at 200 m of depth) (10), and the volume of
water completely devoid of oxygen (anoxic) has
more than quadrupled over the same period (9).
Upwelling of oxygen-depleted water has intensi-
fied in severity and duration along some coasts,
with serious biological consequences (11).
Since 1950, more than 500 sites in coastal waters
have reported oxygen concentrations 2mgliter
(=63 mmol liter
or 61 µmol kg
), a threshold
often used to delineate hypoxia (3,12) (Fig. 1A).
Fewer than 10% of these systems were known to
have hypoxia before 1950. Many more water bodies
may be affected, especially in developing nations
where available monitoring data can be sparse
and inadequately accessed even for waters receiv-
ing high levels of untreated human and agricul-
tural waste. Oxygen continues to decline in some
coastal systems despite substantial reductions in
nutrient loads, which have improved other water
quality metrics (such as levels of chlorophyll a)
that are sensitive to nutrient enrichment (13).
Oxygen is naturally low or absent where bio-
logical oxygen consumption through respiration
exceeds the rate of oxygen supplied by physical
transport, air-sea fluxes, and photosynthesis for
sufficient periods of time. A large variety of such
systems exist, including the OMZs of the open
ocean, the cores of some mode-water eddies, coastal
upwelling zones, deep basins of semi-enclosed seas,
deep fjords, and shallow productive waters with
restricted circulation (14,15). Whether natural or
anthropogenically driven, however, low oxygen
levels and anoxia leave a strong imprint on bio-
geochemical and ecological processes. Electron ac-
ceptors, such as Fe(III) and sulfate, that replace
oxygen as conditions become anoxic yield less energy
than aerobic respiration and constrain ecosystem
energetics (16). Biodiversity, eukaryotic biomass,
and energy-intensive ecological interactions such
as predation are reduced (1719), and energy is
increasingly transferred to microbes (3,16). As
oxygen depletion becomes more severe, persistent,
and widespread, a greater fraction of the ocean is
losing its ability to support high-biomass, diverse
animal assemblages and provide important eco-
system services.
But the paradox is that these areas, sometimes
called dead zones, are far from dead. Instead they
contribute to some of the worldsmostproduc-
tive fisheries harvested in the adjacent, oxygenated
waters (2022) and host thriving microbial assem-
blages that utilize a diversity of biogeochemical
pathways (16).Eukaryoteorganismsthatuselow-
oxygen habitats have evolved physiological and
behavioral adaptations that enable them to extract,
transport, and store sufficient oxygen, maintain
aerobic metabolism, and reduce energy demand
(2326). Fishes, for example, adjust ventilation
rate, cardiac activity, hemoglobin content, and O
binding and remodel gill morphology to increase
lamellar surface area (27). For some small taxa,
including nematodes and polychaetes, high surface
areatovolume ratios enhance diffusion and con-
tribute to hypoxia tolerance (26). Metabolic depres-
sion (23,25,28) and high H
S tolerance (24)are
also key adaptations by organisms to hypoxic and
anoxic environments.
Causes of oxygen decline
Global warming as a cause of oxygen
loss in the open ocean
The discovery of widespread oxygen loss in the
open ocean during the past 50 years depended
on repeated hydrographic observations that re-
vealed oxygen declines at locations ranging from
the northeast Pacific (29) and northern Atlantic
(30) to tropical oceans (2). Greenhouse gasdriven
global warming is the likely ultimate cause of this
ongoing deoxygenation in many parts of the open
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 1of11
Smithsonian Environmental Research Center, Edgewater, MD 21037, USA.
Center for Marine Biodiversity and Conservation and Integrative Oceanography Division, Scripps Institution of
Oceanography, University of California, San Diego, CA 92093, USA.
GEOMAR Helmholtz Centre for Ocean Research Kiel, 24105 Kiel, Germany.
Department of Astrophysics, Geophysics and
Oceanography, MAST-FOCUS Research Group, Université de Liège, 4000 Liège, Belgium.
Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA.
Department of Geology,
Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden.
CNRS/Laboratoire dEtudes en Géophysique et Océanographie Spatiales, 31401 Toulouse, CEDEX 9, France.
Institute, Fisheries and Oceans Canada, Mont-Joli, Québec G5H 3Z4, Canada.
Instituto del Mar del Perú (IMARPE), Esquina Gamarra y General Valle s/n, Callao, Peru.
Facultad de Ciencias y
Filosofıa, Programa de Maestrıa en Ciencias del Mar, Universidad Peruana Cayetano Heredia, Lima 31, Peru.
Intergovernmental Oceanographic Commission of UNESCO, 75732 Paris, CEDEX 7,
The Marine Science Institute, University of the Philippines, Diliman, Quezon City, Philippines.
State University of New York College of Environmental Science and Forestry, Syracuse,
NY 13210, USA.
Instituto Geofísico del Perú, Lima, Perú.
Environment and Life Sciences Research Center, Kuwait Institute for Scientific Research, Salmiya, 22017 Kuwait.
Fisheries Research
and Development, Department of Agriculture, Forestry and Fisheries, Cape Town, South Africa.
Department of Biological Sciences, University of Cape Town, South Africa.
Department of
Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
University of Maryland Center for Environmental Science, Horn Point Laboratory, Cambridge, MD
21613, USA.
College of Marine Science, University of South Florida, St. Petersburg, FL 33701, USA.
International Ocean Carbon Coordination Project, Institute of Oceanology of Polish
Academy of Sciences, Ul. Powstancow Warszawy 55, 81-712 Sopot, Poland.
School of Biological Sciences and Swire Institute of Marine Science, University of Hong Kong, Hong Kong SAR,
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.
*Corresponding author. Email: Present address: Council of Scientific and Industrial Research, Rafi Marg, New Delhi, India.
on January 4, 2018 from
ocean (31). For the upper ocean over the period
19582015, oxygen and heat content are highly cor-
related with sharp increases in both deoxygenation
and ocean heat content, beginning in the mid-
1980s (32).
Ocean warming reduces the solubility of oxy-
gen. Decreasing solubility is estimated to account
for ~15% of current total global oxygen loss and
>50% of the oxygen loss in the upper 1000 m of
the ocean (9,33). Warming also raises metabolic
rates, thus accelerating the rate of oxygen con-
sumption. Therefore, decomposition of sinking
particles occurs faster, and remineralization of
these particles is shifted toward shallower depths
(34), resulting in a spatial redistribution but not nec-
essarily a change in the magnitude of oxygen loss.
Intensified stratification may account for the
remaining 85% of global ocean oxygen loss by re-
ducing ventilationthe transport of oxygen into
the ocean interiorandbyaffectingthesupplyof
nutrients controlling production of organic mat-
ter and its subsequent sinking out of the surface
ocean. Warming exerts a direct influence on ther-
mal stratification and indirectly enhances salinity-
driven stratification through its effects on ice melt
and precipitation. Increased stratification alters
the mainly wind-driven circulation in the upper
few hundred meters of the ocean and slows the
deep overturning circulation (9). Reduced venti-
lation, which may also be influenced by decadal
to multidecadal oscillationsinatmosphericforcing
patterns (35), has strong subsurface manifestations
at relatively shallow ocean depths (100 to 300 m)
in the low- to mid-latitude oceans and less pro-
nounced signatures down to a few thousand meters
at high latitudes. Oxygen declines closer to shore
have also been found in some systems, including
the California Current andlowerSaintLawrence
Estuary, where the relative strength of various
currents have changed and remineralization has
increased (36,37).
There is general agreement between numerical
models and observations about the total amount
of oxygen loss in the surface ocean (38). There is
also consensus that direct solubility effects do
not explain the majority of oceanic oxygen decline
(31). However, numerical models consistently sim-
ulate a decline in the total global ocean oxygen
inventory equal to only about half that of the most
recent observation-based estimate and also pre-
dict different spatial patterns of oxygen decline or,
in some cases, increase (9,31,39). These discrep-
ancies are most marked in the tropical thermo-
cline (40). This is problematic for predictions of
future deoxygenation, as these regions host large
open-ocean OMZs, where a further decline in oxy-
gen levels could have large impacts on ecosystems
and biogeochemistry (Fig. 2A). It is also unclear
how much ocean oxygen decline can be attributed
to alterations in ventilation versus respiration.
Mechanisms other than greenhouse gasdriven
global warming may be at play in the observed
ocean oxygen decline that are not well represented
in current ocean models. For example, internal os-
cillations in the climate system, such as the Pacific
Decadal Oscillation, affect ventilation processes
and, eventually, oxygen distributions (35).
Models predict that warming will strengthen
winds that favor upwelling and the resulting
transport of deeper waters onto upper slope and
shelf environments in some coastal areas (41,42),
especially at high latitudes within upwelling sys-
tems that form along the eastern boundary of
ocean basins (43). The predicted magnitude and
direction of change is not uniform, however, either
within individual large upwelling systems or
among different systems. Upwelling in the south-
ern Humboldt, southern Benguela, and northern
Canary Eastern Boundary upwelling systems is
predicted to increase in both duration and inten-
sity by the end of the 21st century (43). Where the
oxygen content of subsurface source waters de-
clines, upwelling introduces water to the shelf that
the central Oregon coast of the United States in
2006, for example, anoxic waters upwelled to
depths of <50 m within 2 km of shore, persisted for
benthic macro-invertebrates (11). There are no prior
records of such severe oxygen depletion over the
continental shelf or within the OMZ in this area (11).
Nutrient enrichment of coastal waters
Sewage discharges have been known to deplete
oxygen concentrations in estuaries since at least
to agricultural fertilizer runoff was discussed (45).
Nevertheless, the number and severity of hypoxic
sites has continued to increase (Fig. 2B). The hu-
man population has nearly tripled since 1950 (46).
Agricultural production has greatly increased to
feed this growing population and meet demands
for increased consumption of animal protein, re-
sulting in a 10-fold increase in global fertilizer use
over the same period (47). Nitrogen discharges
from rivers to coastal waters increased by 43% in
just 30 years from 1970 to 2000 (48), with more
than three times as much nitrogen derived from
agriculture as from sewage (49).
Eutrophication occurs when nutrients (primar-
ily N and P) and biomass from human waste and
agriculture, as well as N deposition from fossil
fuel combustion, stimulate the growth of algae
and increase algal biomass. The enhanced primary
and secondary production in surface waters in-
creases the delivery rate of degradable organic
matter to bottom waters where microbial decom-
position by aerobic respiration consumes oxygen.
Once oxygen levels are low, behavioral and bio-
geochemical feedbacks can hinder a return to
higher-oxygen conditions (50). For example, bur-
rowing invertebrates that introduce oxygen to
sediments die or fail to recruit, and sediment phos-
phorus is released, fueling additional biological
production in the water column and eventual in-
creased oxygen consumption.
Coastal systems vary substantially in their sus-
ceptibility to developing low oxygen concentrations.
Low rates of vertical exchange within the water
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 2of11
Fig. 1. Oxygen has declined in both the open ocean and coastal
waters during the past half-century. (A) Coastal waters where oxygen
concentrations 61 mmol kg
(63 mmol liter
or 2 mg liter
) have been
reported (red) (8,12). [Map created from data in (8) and updated by
R. Diaz and authors] (B) Change in oxygen content of the global ocean
in mol O
(9). Most of the coastal systems shown here
reported their first incidence of low oxygen levels after 1960. In some
cases, low oxygen may have occurred earlier but was not detected
or reported. In other systems (such as the Baltic Sea) that reported
low levels of oxygen before 1960, low-oxygen areas have become
more extensive and severe (59). Dashed-dotted, dashed, and solid
lines delineate boundaries with oxygen concentrations <80, 40, and
20 mmol kg
, respectively, at any depth within the water column (9).
[Reproduced from (9)]
on January 4, 2018 from
column reduce rates of oxygen resupply (51), and
long water-retention times favor the accumulation
of phytoplankton biomass (14) and its eventual
subsurface degradation. Chesapeake Bay develops
hypoxia and anoxia that persist for several months
during late spring through early autumn and cover
up to 30% of the system area. In contrast, the
nearby Delaware Bay, which has weaker strat-
ification and a shorter retention time, does not
develop hypoxia, in spite of similar nutrient loads
(52). Manila Bay is adjacent to a mega-
city and also receives similar loads
on an annual basis, but it becomes
hypoxic principally during the wet
southwest monsoon period, when
rainfall increases nutrient loads and
stratification (53).
semi-enclosed seas can persist for
minutes to thousands of years and
may extend over spatial scales rang-
ing from less than one to many thou-
sands of square kilometers. Both local
and remote drivers lead to tempo-
ral and spatial variations in hypoxia.
Local weather can influence oxy-
gen depletion in very shallow water
through wind mixing and the effect
of cloud cover on photosynthesis (54).
At larger spatial scales, variations in
wind direction and speed (55), pre-
cipitation and nutrient loads (56),
sea surface temperature (57), and
nutrient content of water masses
transported into bottom layers of
stratified coastal systems contribute
to interannual and longer-period var-
iations in hypoxic volume, duration,
and rate of deoxygenation (14).
Climate change in
coastal waters
Warming is predicted to exacerbate
oxygen depletion in many nutrient-
enriched coastal systems through
mechanisms similar to those of the
open ocean: increased intensity and
duration of stratification, decreased
oxygen solubility, and accelerated res-
piration (4,58,59). The current rate
of oxygen decline in coastal areas ex-
ceeds that of the open ocean (60),
however, likely reflecting the com-
bined effects of increased warming
of shallow water and higher con-
centrations of nutrients. Higher air
temperatures can result in earlier
onset and longer durations of hypoxia
in eutrophic systems through effects
on the seasonal timing of stratifica-
tion and the rate of oxygen decline
(58). An ensemble modeling study of
the Baltic Sea projects declining oxy-
gen under all but the most aggres-
sive nutrient-reduction plans, owing
to increased precipitation and con-
sequent nutrient loads, decreased
flux of oxygen from the atmosphere, and increased
internal nutrient cycling. Even aggressive nutrient
reduction is projected to yield far less benefit under
Because of regional variations in the effects of
global warming on precipitation and winds, the
rate and direction of change in oxygen content is
expected to vary among individual coastal water
bodies (4,58). Where precipitation increases, both
stratification and nutrient discharges are expected
to increase, with the reverse occurring in regions
where precipitation decreases. Changes in seasonal
patterns of precipitation and rates of evaporation
can also be important. Coastal wetlands that re-
move nutrients before they reach open water are
predicted to be lost as sea levels rise, decreasing
capacity to remove excess nitrogen, but the rate
of wetland inundation and the ability of wetlands
to migrate landward will vary.
Effects of ocean deoxygenation
Oxygen influences biological and bio-
geochemical processes at their most
fundamental level (Fig. 3). As re-
search is conducted in more habitats
and using new tools and approaches,
the range of effects of deoxygenation
that have been identified, and the
understanding of the mechanisms
behind those effects, has increased
substantially. Although 2 mg liter
(61 mmol kg
) is a useful threshold
for defining hypoxia when the goal is
to quantify the number of systems or
the spatial extent of oxygen-depleted
waters, a more appropriate approach
when considering biological and eco-
logical effects is to simply define hy-
poxia as oxygen levels sufficiently low
to affect key or sensitive processes.
Organisms have widely varying oxy-
systems (19). In addition, because tem-
perature affects not only oxygen sup-
ply (through its effect on solubility
and diffusion) but also the respira-
tory demand by organisms, oxygen
limitation for organisms is better
expressed as a critical oxygen partial
pressure below which specific or-
ganisms exhibit reduced metabolic
functions than in terms of oxygen
concentration (62,63).
Biological responses
Ocean deoxygenation influences life
processes from genes to emergent
properties of ecosystems (Fig. 4). All
obligate aerobic organisms have limits
to the severity or duration of oxygen
depletion for which they can com-
pensate. Low oxygen levels can re-
duce survival and growth and alter
behavior of individual organisms
(3,4,26,64). Reproduction can be
impaired by reduced energy alloca-
tion to gamete production, as well
as interference with gametogenesis,
neuroendocrine function, and hor-
mone production, and can ultimate-
ly affect populations and fisheries
(6567). Exposure to hypoxia can
trigger epigenetic changes expressed
in future generations, even if these
generations are not exposed to hy-
poxia (68). Brief, repeated exposure
to low oxygen can alter immune
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 3of11
Fig. 2. Dissolved oxygen concentrations in the open ocean and the
Baltic Sea. (A) Oxygen levels at a depth of 300 m in the open ocean.
Major eastern boundary and Arabian Sea upwelling zones, where oxygen
concentrations are lowest, are shown in magenta, but low oxygen levels
can be detected in areas other than these major OMZs. At this depth, large
areas of global ocean water have O
concentrations <100 mmol liter
(outlined and indicated in red). ETNP, eastern tropical North Pacific; ETSP,
eastern tropical South Pacific; ETSA, eastern tropical South Atlantic;
AS, Arabian Sea. [Max Planck Institute for Marine Microbiology, based on
data from the World Ocean Atlas 2009] (B) Oxygen levels at the bottom
of the Baltic Sea during 2012 (59). In recent years, low-oxygen areas
have expanded to 60,000 km
as a result of limited exchange, high
anthropogenic nutrient loads, and warming waters (59)(red,O
63 mmol liter
[2 mg liter
]; black, anoxia). [Reproduced from (59)]
on January 4, 2018 from
responses, increase disease, and reduce growth
In both oceanic and coastal systems, vertical
and horizontal distributions of organisms follow
oxygen gradients and discontinuities, and migra-
tory behavior is constrained in response to both
oxygen availability and the ways that oxygen alters
the distributions of predators and prey (64,71). Be-
cause oxygen tolerances and behavioral responses
to low oxygen levels vary among species, taxa,
trophic groups, and with mobility (19), encounter
rates, feeding opportunities, and the structure of
marine food webs change. Movement to avoid low
oxygen can result in lost feeding opportunities on
low-oxygentolerant prey and can increase energy
expended in swimming (19,70). Hypoxia effects
on vision, a function that is highly oxygen intensive,
may contribute to these constraints, in part through
changing light requirements (72).
The presence and expansion of lowwater col-
umn oxygen reduces diel migration depths, com-
pressing vertical habitat and shoaling distributions
of fishery species and their prey (7375). For pelagic
species, habitat compression can increase vulner-
ability to predation as animals are restricted to
shallower, better-lit waters and can increase vul-
nerability to fishing by predictably aggregating
individuals at shallower or lateral edges of low-
oxygen zones (71,7678). For demersal species,
hypoxia-induced habitat compression can lead to
crowding and increased competition for prey (73),
potentially resulting in decreased body condition
of important fishery species such as Baltic cod (79).
In contrast, migration into and out of hypoxic
waters can allow some animals to utilize oxygen-
depleted habitats for predator avoidance or to
feed on hypoxia-tolerant prey, and then to return
to more highly oxygenated depths or locations
(23,80). Habitat compression may also enhance
trophic efficiency in upwelling regions, contrib-
uting to their extraordinary fish productivity
(20,21). Some hypoxia-tolerant fish and inverte-
brate species expand their ranges as OMZs expand
(28,81), and their predators and competitors are
Multiple stressors
Deoxygenation is mechanistically linked to other
ocean stressors, including warming (82)andacidi-
fication (83), and thus it is often their combined
effects that shape marine ecosystems (84,85).
Because hypoxia limits energy acquisition, it is es-
pecially likely to exacerbate effects of co-occurring
stressors that increase energy demands (65). The
thermal tolerance of ectotherms is limited by their
capacity to meet the oxygen demands of aerobic
metabolism (62). Increased temperature elevates
oxygen demand while simultaneously reducing
oxygen supply, thus expanding the area of the
oceans and coastal waters where oxygen is insuf-
ficient. Through this mechanism, ocean warming
is predicted to result in shifts in the distribution
of fishes and invertebrates poleward by tens to
hundreds of kilometers per decade, shifts into
deeper waters, and local extinctions (63,86). Mod-
els project that warming combined with even
modest O
declines (<10 mmol kg
) can cause
declines in important fishery species that are
sensitive to low oxygen levels (87). Physiological
oxygen limitation in warming waters is also pre-
dicted to reduce maximum sizes of many fish
species, including some that support important
fisheries (88).
Increased respiration that causes deoxygenation
also amplifies the problem of ocean acidification
because the by-product of aerobic respiration is
. Temporal and spatial variations in oxygen
in subpycnocline and shallow eutrophic waters
are accompanied by correlated fluctuations in
. In highly productive estuarine, coastal, and
upwelling regions, oxygen concentrations and pH
can exhibit extreme fluctuations episodically and
on diel, tidal, lunar, and seasonal cycles (83,89).
Elevated CO
can sometimes decrease the oxygen
affinity of respiratory proteins (90), reduce toler-
ance to low oxygen by increasing the metabolic
cost of maintaining acid-base balance (91), and
reduce responses to low oxygen that would other-
wise increase survival (92). Neither the occurrence
nor the magnitude of cases in which acidification
exacerbates the effects of low oxygen are currently
predictable (83).
Other covarying factors, such as nutrients and
fisheries dynamics, can mask or compensate for
effects of deoxygenation, complicating manage-
ment decisions. Fisheries management is designed
to adjust effort and catch as population abundance
changes (93). Thus, direct and indirect effects of
deoxygenation on a harvested population may
not be easily traceable in monitoring or catch data
because management actions adjust for the loss
in abundance. In addition, high nutrient loads can
stimulate production in a habitat that remains
well oxygenated, at least partially offsetting lost
production within a hypoxic habitat (52). Total
landings of finfish, cephalopods, and large mobile
decapods are positively correlated with nitrogen
loads (22), in spite of hypoxia in bottom waters
(52). The conflation of habitat loss and nutrient
enrichment is prominent in upwelling zones, as
well as eutrophic coastal waters. Increased upwell-
ing of nutrient-rich, oxygen-depleted waters from
the 1820s to the 20th century has increased pri-
mary and fish productivity off the coast of Peru,
for example (94). However, there are limits to
the extent of hypoxia that can form before total
system-wide fishery landings decline. In addition,
individual species dependent on a degraded habitat
may decline, whereas other species able to use
more highly oxygenated habitats within the same
system thrive (52).
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 4of11
Fig. 3. Life and death at low oxygen leve ls. (A) Animals using low-oxygen habitats exhibit
a range of physiological, morphological, and behavioral adaptations. For example, teribellid
worms (Neoamphitrite sp., Annelida) with large branchaea and high hemoglobin levels can
survive in the extremely low oxygen levels found at 400 m depth in the Costa Rica Canyon.
(B) Fish kills in aquaculture pens in Bolinao, Philippines, had major economic and health
consequences for the local population. (C) The ctenophore Mnemiopsis leidyi is more
tolerant of low oxygen than trophically equivalent fishes in its nat ive habitat in the Chesapeake
Bay and can use hypoxic areas from which fish are excluded. (D) A low-oxygen event
caused extensive mortality of corals and associated organisms in Bocas del Toro, Panama.
These events may be a more important source of mortality in coral reefs than previously
on January 4, 2018 from
Oxygen availability affects remineralization pro-
cesses and associated sources and sinks of im-
portant nutrient elements, such as nitrogen,
phosphorus, and iron. Even when occurring in
relatively small, low-oxygen regions, the effects of
oxygen-dependent nutrient-cycling processes are
communicated to the wider ocean by circulation.
Hence, local changes within OMZs can influence
nutrient budgets, biological productivity, and
carbon fixation on regional to global scales, and
changes in oxygen-depleted bottom waters of coast-
al systems can affect entire water bodies.
In addition to nitrogen, phosphorus, and iron,
which are discussed in more detail below, a wide
range of other elements are affected by oxygen
conditions. Hydrogen sulfide, which is toxic to
most aerobic organisms, is produced in anoxic
sediments and can be released to the overlying
water column, especially during upwelling events
(16). Methane, a potent greenhouse gas, is also
produced in anoxic sediments, but methanotro-
phic activity limits its release to the atmosphere
(95). Hypoxia increases conversion of As(V) to the
more toxic As(III) (96). Cadmium, copper, and zinc
form sulfide precipitates in the presence of anoxic
or extremely oxygen-deficient waters and sulfides
(97). This process may affect the global distribu-
tion of trace metals, some of which serve as micro-
nutrients for plankton growth, but the importance
of such controls is yet to be fully evaluated.
Where oxygen levels are extremely low or ab-
sent, anaerobic remineralization of organic matter
by denitrification and anaerobic ammonium oxi-
dation (anammox) leads to a net loss of bioavailable
nitrogen through the formation of dinitrogen gas
). Recent investigations have reported func-
tionally anoxic conditions within open-ocean OMZs
(98) and have shown that traces of oxygen at nano-
molar levels can inhibit anaerobic processes, such
as denitrification (99). Total loss of bioavailable
nitrogen from the open ocean is currently esti-
mated to be 65 to 80 Tg year
from the water
column and 130 to 270 Tg year
from sediments
(100). Analysis and modeling of global benthic
data also indicate that denitrification in sediments
underlying high-nutrient and low-oxygen areas
(such as OMZs) removes around three times as
much nitrogen per unit of carbon deposited as
sediments underlying highly oxygenated water
and accounts for ~10% (i.e., 15 Tg year
benthic denitrification (101). Similarly enhanced
benthic denitrification has been observed at very
low bottom-water oxygen concentrations in eutro-
phic coastal systems (102,103)andintheoxycline
of the water column, comparable to OMZs (104).
Certainly, there is genetic potential for water col-
umn denitrification to occur once anoxic conditions
are reached.
A by-product of both nitrification and de-
nitrification is nitrous oxide, N
O, a potent green-
house gas (105). The amount of N
strongly dependent on prevailing oxygen condi-
tions. Production of N
suboxic boundaries of low-oxygen waters, but N
is further reduced to N
in anoxic conditions (95),
so small differences in oxygen concentration de-
termine whether there is net production or con-
sumption of this gas. Low-oxygen zones (including
shelf and coastal areas) contributealargefraction
of the total oceanic N
O emission to the atmo-
sphere, and expansion of these systems may sub-
stantially enhance oceanic N
O emissions (95).
Record air-sea N
O fluxes have recently been ob-
served above the OMZ in the eastern tropical South
Pacific (106).
Although our understanding of the relationships
among oxygen, remineralization of bioavailable
N, and production of N
O has greatly increased,
the consequences of a shift in these relationships
in a warming world with increased O
waters are less well understood. Continued de-
oxygenation of OMZ waters is expected to increase
the volume of water where denitrification and
anammox occur and may lead to increased marine
nitrogen loss (99). This could alter the oceansni-
trogen inventory and, eventually, biological pro-
duction on millennial time scales if nitrogen losses
are not compensated for by increases in nitrogen
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 5of11
Eukaryotic biomass and diversity not
limited by oxygen unless increasing
temperature increases oxygen demand
above oxygen supply
Fishing boats target nsh and
invertebrates found at high densities at
the edge of low-oxygen zones where they
escape physiologically stressful
conditions and take advantage of prey
that use this edge as a refuge habitat
Upwelling of low-O2, high-CO2 waters
can kill and displace sh and benthic
invertebrates, but high nutrients in
upwelled waters fuel high productivity
Organisms inhabiting low-oxygen
habitats have evolved physiological
and behavioral adaptations, but when
tolerances are exceeded, survival,
growth, and reproduction decline
Global warming is expected to continue
to worsen deoxygenation in the open
ocean, and both increasing nutrient
loads and warming could worsen future
deoxygenation in coastal waters
Absence of eukaryotes dependent on
aerobic respiration; increased
dentrication, production of N2O, and
release of Fe and P from sediments
Fig. 4. Oxygen exerts a strong control over biological and biogeochemical processes
in the open ocean and coastal waters. Whether oxygen patterns change over space, as with
increasing depth, or over time, as the effects of nutrients and warming become more
pronounced, animal diversity, biomass, and productivity decline with decreasing levels of oxygen.
At the edge of low-oxygen zones, where nutrients are high and predators and their prey are
concentrated into an oxygenated habitat, productivity can be very high, but even brief exposures
to low oxygen levels can have strong negative effects. (Top ) Well-oxygenated coral reef with
abundant fish and invertebrate assemblages. (Middle) Low-oxygen event in Mobile Bay, United
States, in which crabs and fish crowd into extreme shallows where oxygen levels are highest.
(Bottom) Anoxic mud devoid of macrofauna.
on January 4, 2018 from
fixation (107). However, the feedbacks that link
nitrogen loss and nitrogen fixationremain enig-
matic (101). The direction and magnitude of
change in the N
O budget and air-sea N
are also unclear because increased stratification
could reduce the amount of N
O that reaches
the surface ocean and escapes to the atmo-
sphere (108).
The supply of phosphorus and iron released
from the sediments is generally enhanced under
anoxic conditions (109,110). These nutrients have
the potential to further stimulate biological pro-
duction if they reach well-lit surface waters, such
as above the OMZs associated with coastal up-
welling regions and the surface layer of coastal
waters. Elevated dissolved inorganic phosphorus
and chlorophyll are found in surface waters when
anoxia occurs in fjords and estuaries (111), and,
in some systems, deep waters supply as much
phosphorus to productive surface layers as do
watershed discharges (112). Increased productivity
will tend to increase oxygen consumption, may
increase the sediment area in contact with low-
oxygen waters, and may eventually lead to further
release of phosphorus and iron from the sediment.
There is evidence for this positive feedback in en-
closed seas such as the Baltic Sea, where enhanced
nitrogen fixation in response to deoxygenation
has led to the recent proliferation of undesirable
cyanobacterial blooms that can be toxic and have
adverse effects on ecosystems and society (102).
Enhanced phosphate and iron levels may gen-
erally favor nitrogen fixation by diazotrophs, es-
pecially in the presence of nitrogen loss when
ordinary plankton are driven toward nitrogen
Predicting oxygen decline
Sound management of marine ecosystems is based
on reliable predictions under a range of future
scenarios and an understanding of associated
uncertainties. Numerical models that can project
effects of climate change and eutrophication on
oxygen availability in the open ocean and in coastal
systems can offer these predictions. Current state-
of-the-art global models generally agree that the
total amount of oxygen loss will be a few percent
by the end of the century (31), a decline that
could have substantial biogeochemical and eco-
logical effects. However, there is little agreement
among models about the spatial distribution of
future low-oxygen zones having <100 mmol O
(113) or the spatial patterns of O
changes that
have occurred over the past several decades (40).
This uncertainty currently limits our ability to
reliably predict the regional impact of climate
warming on open-ocean OMZs and, hence, on
oxygen-sensitive biogeochemical processes, in-
cluding the nitrogen budget. More realistic and
detailed inclusion of mechanisms other than
-driven global warmingsuch as atmospheric
nutrient deposition and decadal- to multidecadal-
scale climate variability (especially fluctuations
in wind patterns)may improve agreement among
models and, therefore, their ability to predict the
spatial distribution of past and future low-oxygen
Predicting oxygen levels in individual coastal
water bodies requires modeling the variability in
these systems, which is tightly governed by inter-
actions with the land, atmosphere, sediment, and
offshore waters at small space and time scales.
This can be achieved by current estuary-specific
and regional three-dimensional coupled hydro-
dynamicwater quality models (67); these and
other state-of-the-art modeling approaches de-
serve broader implementation. However, model
performance can be hampered by the use of forcing
data, such as river discharges and atmospheric
conditions, that lack sufficiently resolved spatial
and temporal detail. Projections of future de-
oxygenation also require reliable information on
changes in key parameters and interactions under
a range of climate change and nutrient manage-
ment scenarios and benefit from the use of ap-
proaches that explicitly model connections along
the riverestuaryadjacent ocean or sea continuum.
Projections of local changes in timing and magni-
tude of precipitation and warming are especially
important. Future characteristics of human pop-
ulations, such as rates of population growth, the
ulation centers, and the effects of education and
income on demands for improved sanitation and
animal protein are also needed because of their
influence on nutrient discharges at both local
and global scales.
Improving predictions critical for manage-
ment in both the open ocean and coastal systems
will require increased observations from field mea-
surements and experiments to constrain and refine
models. Ideally, such data should include repre-
sentations of future environmental conditions.
An improved mechanistic understanding of feed-
backs that limit or exacerbate oxygen depletion
and alter oxygen-sensitive biogeochemical cycles
is especially important. In the open ocean, infor-
mation is needed on transport mechanismssuch
as small-scale mixing processes (114), stirring, and
transport by mesoscale structures (115)that influ-
ence oxygen distributions.
Advanced observation networks can provide
data to underpin the development of an improved
mechanistic understanding and the refinement
of current models. Drifters and autonomous plat-
forms ranging from Argo floats to tethered arrays
provide real-time data and have the potential to
increase knowledge of oxygen dynamics at the
tely needed for both regional and global models.
High-resolution measurements have revealed the
small-scale patchiness of oxygen-sensitive process-
es in space and time (99,106) and have provided
new insight into the biogeochemistry of OMZs
(98). Optical oxygen sensors mounted on Argo
floats or gliders can now use atmospheric oxygen
to perform ongoing, in situ calibrations through-
out the float (116) or glider lifetime. The accuracy
of autonomous measurements of in situ oxygen
concentrations 1mmol kg
has been improved
by the development of STOX (switchable trace
amount oxygen) sensors (117), and novel trace-
oxygen optical sensors can now provide precise
oxygen quantification in OMZs and detect oxygen
concentrations as low as ~5 nmol kg
(118). The
new platforms and sensors facilitate the implemen-
tation of regional and global oxygen observatories
targeted toward the much-improved monitoring
and, eventually, modeling and management of de-
oxygenation. For coastal waters, it is also important
to develop sensors that are affordable for use in
low-income developing countries (LIDCs) and
that can be used to generate reliable data from
citizen science.
Predicting effects at large scales of
space, time, and ecological organization
Improved management and conservation of open-
ocean and coastal systems requires predictions of
the effects of deoxygenation at spatial, temporal,
and ecological scales most relevant to the eco-
system services provided by these waters. Although
research has clearly shown that low-oxygen zones
reduce habitat for species dependent on aerobic
respiration and that exposure to suboptimal oxy-
gen levels leads to a host of negative effects on
individuals, identifying effects of expanding de-
oxygenation at the scale of populations or fish-
eries stocks has been difficult, particularly for
mobile species (52,119). A similar problem applies
to scaling up oxygen-sensitive biogeochemical pro-
cesses to predict feedbacks on global ocean nutrient
inventories and Earthsclimate.
Scaling to predict effects on food webs and
anisms; examples include increased production
of planktonic prey under high nutrient loads and
increased encounter rates between predators and
their prey when they are squeezed into smaller
oxygenated habitat space (52,119,120). In addi-
tion, populations maintained below their habitat-
dependent carrying capacity by fisheries or other
of habitat as species nearer their carrying capacity.
In these cases, habitats suitable for feeding and
other life functions may remain sufficient, even
when their size is reduced by low oxygen.
The most promising approaches to scaling em-
ploy a suite of methods ranging from detailed
mechanistic studies to large-scale field efforts, as
well as new and increasingly sophisticated analy-
ses and modeling tools that address spatial pro-
cesses (120), temporal fluctuations (121,122), and
the role of co-occurring stressors. Consideration
of the effects of early hypoxia exposure on later
life stages after organisms migrate to more highly
oxygenated habitats can indicate the large spatial
scales over which even spatially limited hypoxia
can have impacts (123). Paleoecological approaches
are critical for gaining a long-term perspective
beyond the time scale of biological and oceano-
graphic observation (94,124). Even sophisticated
approaches will not always provide support for
large-scale negative effects of deoxygenation, but
eliminating deoxygenation as a major cause of
population declines is also important to effective
Increased research is most needed in locations
where deoxygenation is likely to affect local eco-
nomies and food security. Place-based, artisanal
fisheries with little capacity to relocate as local
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 6of11
on January 4, 2018 from
habitat degrades are more likely to suffer from
deoxygenation than industrialized fisheries with
highly mobile fishing fleets. Aquaculture, in par-
ticular, can be a critical intersection between de-
oxygenation and societal effects because aquaculture
itself can cause deoxygenation (125), and animals
restrained in nets and cages are unable to escape
harmful oxygen conditions. But critically, much
of the worlds marine aquaculture is done in
LIDCs. Fish kills in aquaculture pens (125) can
compromise livelihoods and can directly harm
human health when low incomes and food in-
security lead to consumption of fish killed by
low-oxygen conditions (126). Coral reefs contrib-
ute to food security and local economies through
their value to tourism and storm protection, as well
as food production. Recent research indicates that
low oxygen may be an increasingly important factor
in the mortality of corals and associated fauna in
some regions and that low-oxygen problems on coral
reefs are likely underreported (127).
Reducing deoxygenation and its
negative effects
Local, national, and global efforts are required
to limit further oxygen declines, restore oxygen
to previously well-oxygenated environments, and
enhance the resilience of ecosystems affected by
deoxygenation. At their most basic level, the actions
needed to address deoxygenationreducing nutri-
ent loads to coastal waters and reducing green-
house gas emissions globallyhave substantial
benefits to society above and beyond improving
oxygen conditions. Improved sanitation can ben-
efit human health directly while also reducing
coastal nutrient loads. Eliminating excess and
inefficiently applied fertilizer can reduce costs to
farmers (128) and emissions of N
O(129) and
may decrease nitrogen loads to waterways. Eli-
minating emissions from combustion of fossil
fuels can reduce greenhouse gas production and
may result in decreased atmospheric deposition
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 7of11
Deoxygenation management and policy strategies
Ecosystem-based mitigation to
restore and protect the environment
Implement and maintain monitoring and analysis programs
Adaptation to restore and protect
marine organisms and sheries
Reduce anthropogenic nutrients
reaching coastal waters to reduce
eutrophication-driven deoxygenation
Reduce greenhouse gas
emissions to reduce deoxygen-
ation due to climate change
Monitoring, data analysis, and
dissemination of results are
critical to detect problems and
determine the eectiveness of
management and restoration
Create marine protected areas and no-catch zones in well-oxygenated
areas that can serve as refugia; protect populations when oxygen is low
Consider eects of low
oxygen on production,
non-shing mortality, and
shing mortality in setting
catch limits
Reduce shing pressure on hypoxia-intolerant species. Utilize shing
gear that minimizes additional stress on oxygen-impacted sh stocks
and ecosystems.
Develop aquaculture practices and limits to protect oxygen
content of waters
Fig. 5. Strateg ies for deoxygenati on management and
policy-making. (Left) Multiple management actions can help to mitigate
deoxygenation. Key among these are reductions in (i) anthropogenic
nutrient inputs from land, which will reduce algal blooms and
subsequent oxygen drawdown; (ii) greenhouse gas emissions, which
will slow warming; and (iii) waste production from aquaculture, which
will contribute to oxygen consumption. (Right) Adaptive measures
can reduce stress and may increase resilience of marine ecosystems
that face deoxygenation. Examples include creating protected
areas that can serve as refugia in hypoxic areas or during hypoxic
events; incorporating oxygen effects on population distribution
and dynamics into catch limits and closures, as has been done for
rockfish; and adopting gear regulations that reduce stress on vulnerable
fisheries or ecosystems. (Bottom) Both types of actions benefit
from enhanced oxygen and biological monitoring, including access
to real-time data that can elicit quick management responses, as
well as more synthetic analyses that might reveal spatial and
temporal trends.
on January 4, 2018 from
of nitrogen that stimulates primary production
in coastal waters (130). Reducing or eliminating
greenhouse gas emissions can, more generally,
lower the threats from global warming and ocean
acidification and, simultaneously, reduce ocean
deoxygenation. Improved management of fish-
eries and marine habitats that are sensitive to
the development and effects of low oxygen helps
to protect economies, livelihoods, and food secu-
rity (Fig. 5).
Failure to reduce nutrient loads, at all or suf-
ficiently, is the primary reason that oxygen levels
have not improved in most coastal systems. But
some of the reasons for slow progress are inher-
ent in the problem itself. High sedimentary oxygen
demand can continue for decades as accumulated
organic matter degrades (57), phosphorus may con-
tinue to be released from sediments once oxygen
thresholds have been crossed (102), and nitrogen
leached from soils and dissolved in groundwater
continues to enter waterways for decades (131).
Increasing temperatures can require greater re-
ductions in nutrients to meet the same oxygen goals
(57,61). Because of changing conditions and the
nonlinearity of ecological processes, ecosystems
may not return to their predisturbed state even if
conditions that caused the initial deoxygenation
are eased (132).
To maintain the current conditions, per capita
reductions in nutrient discharges and greenhouse
gas emissions will need to increase as the global
population continues to grow. Nevertheless, con-
siderable improvements have been observed in
some coastal systems through implementation of
a wide range of strategies to reduce the input of
nutrients and biomass (133). Some of the most
notable improvements have occurred in systems
such as the Thames and Delaware River estuaries,
where steps to keep raw sewage out of the rivers
and, eventually, to treat wastewater substantially
decreased biological oxygen demand (133). In the
Maryland portion of the Chesapeake Bay, where
both point- and nonpoint-source nutrient reduc-
tion strategies have been implemented, oxygen
concentrations <0.1 mg liter
(<3 mmol kg
rarely been measured since 2014amarkedcon-
trast to the first 30 years of frequent monitoring
(19842013) (134). In one Chesapeake tributary,
the Potomac River, nitrogen reductions due to
better air quality have played the major role in
water quality improvements (135). Additionally,
better understanding of deoxygenation may
enable a range of adaptive, protective actions
for fisheries and the habitats that sustain them
(Fig. 5).
An integrated framework that combines mod-
eling, observations, and experiments in a multiple-
stressor environment and involves the full range
of stakeholders (e.g., scientists, local governments,
intergovernmental bodies, industrial sectors, and
the public) will facilitate the development and im-
plementation of the most ecologically and econo-
mically effective plans to reverse deoxygenation
(Fig. 6). Networks of research scientists, such as
the Intergovernmental Oceanographic Commis-
sion (IOC)UNESCO Global Ocean Oxygen Network
global-ocean-oxygen-network/), as well as groups
with more limited geographic and disciplinary
scope, can help to keep the process updated and
to build capacity in parts of the world where
improved technology and training are needed.
The key to effective management is raised aware-
ness of the phenomenon of deoxygenation, as well
as its causes, consequences, and remediation
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 8of11
Monitoring: sophisticated automated oceanographic sensor arrays and citizen scientists document
current and changing oxygen conditions.
Inclusion of data in regional and global databases allows local measurements to contribute to analyses of
local and large-scale patterns and trends.
Numerical models use monitoring and experiment results to predict future conditions and loss of
ecosystem services under a range of possible scenarios.
Research can inform
regulations for restoring
oxygen and reducing its
decline, as well as aid
sheries managment to
minimize eects on
economies and food
Societal goals based on protection of ecosystem services
and historical conditions
D = [exp(–k1t) – exp(–k2t)]
+ D0exp(–k2t)
s use mon
ng an
ces under a ran
sible scenarios
Fig. 6. Monitoring in coastal waters and the open ocean enables documentation of
deoxygenation and, in some cases, improved oxygen conditions. In shallow water, handheld,
continuous, and shipboard sensors are used worldwide. In the open ocean and nearshore waters,
global arrays of sensors (such as the Argo floats), shipboard measurements, and deep platforms and
profilers provide data to validate global models. Archiving data in well-documented databases
accessible by all stakeholders facilitates scientific and management advances and public
engagement. Experiments and field studies at scales ranging from genes to ecosystems provide
information to predict the effects of low oxygen levels on ecological processes and services and are
also used to develop fisheries and ecosystem models. Model projections and analyses of
deoxygenation and its effects inform management and policy at both local and multinational scales
and provide the basis for strategies to combat deoxygenation.
on January 4, 2018 from
1. R. E. Keeling, A. Körtzinger, N. Gruber, Ocean deoxygenation
in a warming world. Annu. Rev. Mar. Sci. 2, 199229 (2010).
pmid: 21141663
2. L. Stramma, G. C. Johnson, J. Sprintall, V. Mohrholz,
Expanding oxygen-minimum zones in the tropical oceans.
Science 320, 655658 (2008). doi: 10.1126/science.1153847;
pmid: 18451300
3. R. J. Diaz, R. Rosenberg, Spreading dead zones and
consequences for marine ecosystems. Science 321,
926929 (2008). doi: 10.1126/science.1156401;
pmid: 18703733
4. N. N. Rabalais et al., Eutrophication-driven deoxygenation in
the coastal ocean. Oceanography 27, 172183 (2014).
doi: 10.5670/oceanog.2014.21
5. L. A. Levin, D. L. Breitburg, Linking coasts and seas to
address ocean deoxygenation. Nat. Clim. Chang. 5, 401403
(2015). doi: 10.1038/nclimate2595
6. J. Zhang et al., Natural and human-induced hypoxia and
consequences for coastal areas: Synthesis and future
development. Biogeosciences 7, 14431467 (2010).
doi: 10.5194/bg-7-1443-2010
7. R. D. Norris, S. K. Turner, P. M. Hull, A. Ridgwell, Marine
ecosystem responses to Cenozoic global change. Science
341, 492498 (2013). doi: 10.1126/science.1240543;
pmid: 23908226
8. A. J. Watson, Oceans on the edge of anoxia. Science 354,
15291530 (2016). doi: 10.1126/science.aaj2321;
pmid: 28008026
9. S. Schmidtko, L. Stramma, M. Visbeck, Decline in global
oceanic oxygen content during the past five decades. Nature
542, 335339 (2017). doi: 10.1038/nature21399;
pmid: 28202958
10. L. Stramma, S. Schmidtko, L. A. Levin, G. C. Johnson, Ocean
oxygen minima expansions and their biological impacts.
Deep-Sea Res. Part I 57, 587595 (2010). doi: 10.1016/
11. F. Chan et al., Emergence of anoxia in the California current
large marine ecosystem. Science 319, 920 (2008).
doi: 10.1126/science.1149016; pmid: 18276882
12. K. Isensee et al., The ocean is losing its breathin Ocean and
Climate Scientific Notes, ed. 2 (2016), pp. 2032;
13. B. Riemann et al., Recovery of Danish coastal ecosystems
after reductions in nutrient loading: A holistic ecosystem
approach. Estuaries Coasts 39,8297 (2016). doi: 10.1007/
14. N. Rabalais et al., Dynamics and distribution of natural and
human-caused hypoxia. Biogeosciences 7, 585619 (2010).
doi: 10.5194/bg-7-585-2010
15. J. Karstensen et al., Open ocean dead-zone in the tropical
North Atlantic Ocean. Biogeosciences 12, 25972605 (2015).
doi: 10.5194/bg-12-2597-2015
16. J. J. Wright, K. M. Konwar, S. J. Hallam, Microbial ecology of
expanding oxygen minimum zones. Nat. Rev. Microbiol. 10,
381394 (2012). pmid: 22580367
17. A. J. Gooday et al., Habitat heterogeneity and its influence on
benthic biodiversity in oxygen minimum zones. Mar. Ecol. 31,
125147 (2010). doi: 10.1111/j.1439-0485.2009.00348.x
18. E. A. Sperling et al., Oxygen, ecology, and the Cambrian
radiation of animals. Proc. Natl. Acad. Sci. U.S.A. 110,
1344613451 (2013). doi: 10.1073/pnas.1312778110;
pmid: 23898193
19. R. Vaquer-Sunyer, C. M. Duarte, Thresholds of hypoxia for
marine biodiversity. Proc. Natl. Acad. Sci. U.S.A. 105,
1545215457 (2008). doi: 10.1073/pnas.0803833105;
pmid: 18824689
20. A. Bertrand et al., Oxygen: A fundamental property regulating
pelagic ecosystem structure in the coastal southeastern
tropical Pacific. PLOS ONE 6, e29558 (2011). doi: 10.1371/
journal.pone.0029558; pmid: 22216315
21. F. P. Chavez, A. Bertrand, R. Guevara-Carrasco, P. Soler,
J. Csirke, The northern Humboldt current system: Brief
history, present status and a view towards the future.
Prog. Oceanogr. 79,95105 (2008). doi: 10.1016/
22. S. W. Nixon, B. A. Buckley, A strikingly rich zone”—Nutrient
enrichment and secondary production in coastal marine
ecosystems. Estuaries 25, 782796 (2002). doi: 10.1007/
23. B. A. Seibel, Critical oxygen levels and metabolic suppression
in oceanic oxygen minimum zones. J. Exp. Biol. 214, 326336
(2011). doi: 10.1242/jeb.049171; pmid: 21177952
24. A. C. Utne-Pa lm et al., Trophic structure and community
stability in an overfished ecosystem. Science 329,
333336 (2010). doi: 10.1126/science.1190708;
pmid: 20647468
25. R. S. Wu, Hypoxia: From molecular responses to ecosystem
responses. Mar. Pollut. Bull. 45,3545 (2002). doi: 10.1016/
S0025-326X(02)00061-9; pmid: 12398365
26. L. Levin, Oxygen minimum zone benthos: Adaptation and
community response to hypoxia. Oceanogr. Mar. Biol. 41,
145 (2003).
27. J. G. Richards, Metabolic and molecular responses of fish to
hypoxia. Fish Physiol. 27, 443485 (2009). doi: 10.1016/
28. N. D. Gallo, L. A. Levin, Fish ecology and evolution in the
worlds oxygen minimum zones and implications of ocean
deoxygenation. Adv. Mar. Biol. 74, 117198 (2016).
doi: 10.1016/bs.amb.2016.04.001; pmid: 27573051
29. F. A. Whitney, H. J. Freeland, M. Robert, Persistently declining
oxygen levels in the interior waters of the eastern subarctic
Pacific. Prog. Oceanogr. 75, 179199 (2007). doi: 10.1016/
30. I. Stendardo, N. Gruber, Oxygen trends over five decades
in the North Atlantic. J. Geophys. Res. 117, C11004
31. L. Bopp et al., Multiple stressors of ocean ecosystems in the
21st century: Projections with CMIP5 models. Biogeosciences
10, 62256245 (2013). doi: 10.5194/bg-10-6225-2013
32. T. Ito, S. Minobe, M. C. Long, C. Deutsch, Upper ocean O
trends: 19582015. Geophys. Res. Lett. 44, 42144223
(2017). doi: 10.1002/2017GL073613
33. K. P. Helm, N. L. Bindoff, J. A. Church, Observed decreases in
oxygen content of the global ocean. Geophys. Res. Lett. 38,
L23602 (2011). doi: 10.1029/2011GL049513
34. P. G. Brewer, E. T. Peltzer, Depth perception: The need to
report ocean biogeochemical rates as functions of
temperature, not depth. Philos. Trans. R. Soc. London Ser. A
375, 20160319 (2017). doi: 10.1098/rsta.2016.0319;
pmid: 28784710
35. C. Deutsch et al., Centennial changes in North Pacific anoxia
linked to tropical trade winds. Science 345, 665668 (2014).
doi: 10.1126/science.1252332; pmid: 25104384
36. S. Nam, Y. Takeshita, C. A. Frieder, T. Martz, J. Ballard,
Seasonal advection of Pacific Equatorial Water alters oxygen
and pH in the Southern California Bight. J. Geophys. Res.
Oceans 120, 53875399 (2015). doi: 10.1002/2015JC010859
37. D. Gilbert, B. Sundby, C. Gobeil, A. Mucci, G.-H. Tremblay,
A seventy-two-year record of diminishing deep-water oxygen
in the St. Lawrence estuary: The northwest Atlantic
connection. Limnol. Oceanogr. 50, 16541666 (2005).
doi: 10.4319/lo.2005.50.5.1654
38. A. Oschlies et al., Patterns of deoxygenation: Sensitivity to
natural and anthropogenic drivers. Philos. Trans. R. Soc.
London Ser. A 375, 20160325 (2017). doi: 10.1098/
rsta.2016.0325; pmid: 28784715
39. A. Oschlies, K. G. Schulz, U. Riebesell, A. Schmittner,
Simulated 21st centurys increase in oceanic suboxia by
enhanced biotic carbon export. Global Biogeochem.
Cycles 22, GB4008 (2008). doi: 10.1029/2007GB003147
40. L. Stramma, A. Oschlies, S. Schmidtko, Mismatch between
observed and modeled trends in dissolved upper-ocean
oxygen over the last 50 yr. Biogeosciences 9, 40454057
(2012). doi: 10.5194/bg-9-4045-2012
41. W. J. Sydeman et al., Climate change and wind intensification
in coastal upwelling ecosystems. Science 345,7780 (2014).
doi: 10.1126/science.1251635; pmid: 24994651
42. R. A. Feely, C. L. Sabine, J. M. Hernandez-Ayon, D. Ianson,
B. Hales, Evidence for upwelling of corrosive acidifiedwater
onto the continental shelf. Science 320, 14901492 (2008).
doi: 10.1126/science.1155676; pmid: 18497259
43. D. Wang, T. C. Gouhier, B. A. Menge, A. R. Ganguly,
Intensification and spatial homogenization of coastal
upwelling under climate change. Nature 518, 390394
(2015). doi: 10.1038/nature14235; pmid: 25693571
44. D. Galton, 10th Meeting: Report of the royal commission on
metropolitan sewage. J. Soc. Arts 33, 290 (1884).
45. A. D. Hasler, Cultural eutrophication is reversible. Bioscience
19, 425431 (1969). doi: 10.2307/1294478
46. United Nations Department of Economic and Social Affairs/
Population Division, World Population Prospects: The 2015
Revision,DVD Edition (2015);
47. International Fertilizer Association, IFADATA (2016);
48. S. Seitzinge r et al., Global river nutrient export: A
scenario analysis of past and future trends.
Global Biogeochem. Cycles 24, GB0A08 (2010).
doi: 10.1029/2009GB003587
49. A. F. Bouwman, G. Van Drecht, J. M. Knoop, A. H. W. Beusen,
C. R. Meinardi, Exploring changes in river nitrogen export to
the worlds oceans. Global Biogeochem. Cycles 19, GB1002
(2005). doi: 10.1029/2004GB002314
50. A. Steckbauer, C. M. Duarte, J. Carstensen, R. Vaquer-Sunyer,
D. J. Conley, Ecosystem impacts of hypoxia: Thresholds of
hypoxia and pathways to recovery. Environ. Res. Lett. 6,
025003 (2011). doi: 10.1088/1748-9326/6/2/025003
51. D. C. Reed, J. A. Harrison, Linking nutrient loading and
oxygen in the coastal ocean: A new global scale model. Global
Biogeochem. Cycles 30, 447459 (2016). doi: 10.1002/
52. D. L. Breitburg, D. W. Hondorp, L. A. Davias, R. J. Diaz,
Hypoxia, nitrogen, and fisheries: Integrating effects across
local and global landscapes. Annu. Rev. Mar. Sci. 1, 329349
(2009). pmid: 21141040
53. L. P. A. Sotto, G. S. Jacinto, C. L. Villanoy, Spatiotemporal
variability of hypoxia and eutrophication in Manila Bay,
Philippines during the northeast and southwest monsoons.
Mar. Pollut. Bull. 85, 446454 (2014). doi: 10.1016/
j.marpolbul.2014.02.028; pmid: 24655947
54. R. M. Tyler, D. C. Brady, T. E. Targett, Temporal and spatial
dynamics of diel-cycling hypoxia in estuarine tributaries.
Estuaries Coasts 32, 123145 (2009). doi: 10.1007/s12237-
55. M. E. Scully, The importance of climate variability to wind-
driven modulation of hypoxia in Chesapeake Bay. J. Phys.
Oceanogr. 40, 14351440 (2010). doi: 10.1175/
56. M. Li et al., What drives interannual variability of hypoxia in
Chesapeake Bay: Climate forcing versus nutrient loading?
Geophys. Res. Lett. 43, 21272134 (2016). doi: 10.1002/
57. A. Capet, J.-M. Beckers, M. Grégoire, Drivers, mechanisms
and long-term variability of seasonal hypoxia on the Black
Sea northwestern shelfis there any recovery after
eutrophication? Biogeosciences 10, 39433962 (2013).
doi: 10.5194/bg-10-3943-2013
58. A. H. Altieri, K. B. Gedan, Climate change and dead zones.
Global Change Biol. 21, 13951406 (2015). doi: 10.1111/
gcb.12754; pmid: 25385668
59. J. Carstensen, J. H. Andersen, B. G. Gustafsson, D. J. Conley,
Deoxygenation of the Baltic Sea during the last century.
Proc. Natl. Acad. Sci. U.S.A. 111, 56285633 (2014).
doi: 10.1073/pnas.1323156111;pmid: 24706804
60. D. Gilbert, N. N. Rabalais, R. J. Díaz, J. Zhang, Evidence for
greater oxygen decline rates in the coastal ocean than in the
open ocean. Biogeosciences 7, 22832296 (2010).
doi: 10.5194/bg-7-2283-2010
61. H. M. Meier et al., Hypoxia in future climates: A model
ensemble study for the Baltic Sea. Geophys. Res. Lett. 38,
L24608 (2011). doi: 10.1029/2011GL049929
62. H.-O. Pörtner, Integrating climate-related stressor effects on
marine organisms: Unifying principles linking molecule to
ecosystem-level changes. Mar. Ecol. Prog. Ser. 470, 273290
(2012). doi: 10.3354/meps10123
63. C. Deutsch, A. Ferrel, B. Seibel, H.-O. Pörtner, R. B. Huey,
Climate change tightens a metabolic constraint on marine
habitats. Science 348, 11321135 (2015). doi: 10.1126/
science.aaa1605; pmid: 26045435
64. D. Breitburg, Effects of hypoxia, and the balance between
hypoxia and enrichment, on coastal fishes and fisheries.
Estuaries Coasts 25, 767781 (2002). doi: 10.1007/
65. I. M. Sokolova, Energy-limited tolerance to stress as a
conceptual framework to integrate the effects of multiple
stressors. Integr. Comp. Biol. 53, 597608 (2013).
doi: 10.1093/icb/ict028; pmid: 23615362
66. P. Thomas, M. S. Rahman, M. E. Picha, W. Tan, Impaired
gamete production and viability in Atlantic croaker collected
throughout the 20,000 km
hypoxic region in the northern
Gulf of Mexico. Mar. Pollut. Bull. 101, 182192 (2015).
doi: 10.1016/j.marpolbul.2015.11.001; pmid: 26547103
67. K. A. Rose et al., Numerical modeling of hypoxia and its
effects: Synthesis and going forwardin Modeling Coastal
Hypoxia (Springer, ed. 1, 2017), pp. 401421.
68. S. Y. Wang et al., Hypoxia causes transgenerational
impairments in reproduction of fish. Nat. Commun. 7, 12114
(2016). doi: 10.1038/ncomms12114; pmid: 27373813
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 9of11
on January 4, 2018 from
69. A. G. Keppel, D. L. Breitburg, G. H. Wikfors, R. B. Burrell,
V. M. Clark, Effects of co-varying diel-cycling hypoxia and pH
on disease susceptibility in the eastern oyster Crassostrea
virginica.Mar. Ecol. Prog. Ser. 538, 169183 (2015).
doi: 10.3354/meps11479
70. K. L. Stierhoff, T. E. Targett, J. H. Power, Hypoxia-induced
growth limitation of juvenile fishes in an estuarine nursery:
Assessment of small-scale temporal dynamics using RNA:
DNA. Can. J. Fish. Aquat. Sci. 66, 10331047 (2009).
doi: 10.1139/F09-066
71. W. F. Gilly, J. M. Beman, S. Y. Litvin, B. H. Robison,
Oceanographic and biological effects of shoaling of the
oxygen minimum zone. Annu. Rev. Mar. Sci. 5, 393420
(2013). doi: 10.1146/annurev-marine-120710-100849;
pmid: 22809177
72. L. R. McCormick, L. A. Levin, Physiological and ecological
implications of ocean deoxygenation for vision in marine
organisms. Philos. Trans. R. Soc. London Ser. A 375,
20160322 (2017). doi: 10.1098/rsta.2016.0322;
pmid: 28784712
73. L. A. Eby, L. B. Crowder, Hypoxia-based habitat compression
in the Neuse River Estuary: Context-dependent shifts in
behavioral avoidance thresholds. Can. J. Fish. Aquat. Sci. 59,
952965 (2002). doi: 10.1139/f02-067
74. M. Roman, J. J. Pierson, D. G. Kimmel, W. C. Boicourt,
X. Zhang, Impacts of hypoxia on zooplankton spatial
distributions in the northern Gulf of Mexico. Estuaries Coasts
35, 12611269 (2012). doi: 10.1007/s12237-012-9531-x
75. K. F. Wishner et al., Vertical zonation and distributions of
calanoid copepods through the lower oxycline of the Arabian
Sea oxygen minimum zone. Prog. Oceanogr. 78, 163191
(2008). doi: 10.1016/j.pocean.2008.03.001
76. J. A. Koslow, R. Goericke, A. Lara-Lopez, W. Watson, Impact
of declining intermediate-water oxygen on deepwater fishes
in the California Current. Mar. Ecol. Prog. Ser. 436, 207218
(2011). doi: 10.3354/meps09270
77. L. Stramma et al., Expansion of oxygen minimum zones
may reduce available habitat for tropical pelagic fishes.
Nat. Clim. Chang. 2,3337 (2012). doi: 10.1038/nclimate1304
78. J. K. Craig, S. H. Bosman, Small spatial scale variation in
fish assemblage structure in the vicinity of the northwestern
Gulf of Mexico hypoxic zone. Estuaries Coasts 36, 268285
(2013). doi: 10.1007/s12237-012-9577-9
79. M. Casini et al., Hypoxic areas, density-dependence and food
limitation drive the body condition of a heavily exploited
marine fish predator. R. Soc. Open Sci. 3, 160416 (2016).
doi: 10.1098/rsos.160416; pmid: 27853557
80. W. Ekau, H. Auel, H.-O. Pörtner, D. Gilbert, Impacts of hypoxia
on the structure and processes in pelagic communities
(zooplankton, macro-invertebrates and fish). Biogeosciences
7, 16691699 (2010). doi: 10.5194/bg-7-1669-2010
81. K. N. Sato, L. A. Levin, K. Schiff, Habitat compression and
expansion of sea urchins in response to changing climate
conditions on the California continental shelf and slope
(19942013). Deep-Sea Res. Part II 137, 377389 (2017).
doi: 10.1016/j.dsr2.2016.08.012
82. A. P. Farrell, Pragmatic perspective on aerobic scope:
Peaking, plummeting, pejus and apportioning. J. Fish Biol. 88,
322343 (2016). doi: 10.1111/jfb.12789; pmid: 26592201
83. C. J. Gobler, H. Baumann, Hypoxia and acidification in ocean
ecosystems: Coupled dynamics and effects on marine life.
Biol. Lett. 12, 20150976 (2016). doi: 10.1098/rsbl.2015.0976;
pmid: 27146441
84. D. L. Breitburg et al., And on top of all thatCoping with
ocean acidification in the midst of many stressors.
Oceanography 28,4861 (2015). doi: 10.5670/
85. S. C. Doney, The growing human footprint on coastal and
open-ocean biogeochemistry. Science 328, 15121516
(2010). doi: 10.1126/science.1185198; pmid: 20558706
86. W. W. Cheung, J. Dunne, J. L. Sarmiento, D. Pauly, Integrating
ecophysiology and plankton dynamics into projected
maximum fisheries catch potential under climate change in
the Northeast Atlantic. ICES J. Mar. Sci. 68, 10081018
(2011). doi: 10.1093/icesjms/fsr012
87. C. H. Stortini, D. Chabot, N. L. Shackell, Marine species in
ambient low-oxygen regions subject to double jeopardy
impacts of climate change. Global Change Biol. 23,
22842296 (2017). doi: 10.1111/gcb.13534; pmid: 27753179
88. D. Pauly, W. W. L. Cheung, Sound physiological knowledge
and principles in modeling shrinking of fishes under climate
change. Global Change Biol. 10.1111/gcb.13831 (2017).
doi: 10.1111/gcb.13831; pmid: 28833977
89. L. A. Levin et al., Comparative biogeochemistryecosystem
humaninteractionson dynamic continental margins.J. Mar. Syst.
141,317 (2015). doi: 10.1016/j.jmarsys.2014.04.016
90. B. A. Seibel, The jumbo squid, Dosidicus gigas
(Ommastrephidae), living in oxygen minimum zones II:
Bloodoxygen binding. Deep-Sea Res. Part II 95, 139144
(2013). doi: 10.1016/j.dsr2.2012.10.003
91. J. R. Hancock, S. P. Place, Impact of ocean acidification
on the hypoxia tolerance of the woolly sculpin, Clinocottus
analis.Conserv. Physiol. 4, cow040 (2016). doi: 10.1093/
conphys/cow040; pmid: 27729981
92. S. H. Miller, D. L. Breitburg, R. B. Burrell, A. G. Keppel,
Acidification increases sensitivity to hypoxia in important
forage fishes. Mar. Ecol. Prog. Ser. 549,18 (2016).
doi: 10.3354/meps11695
93. R. Hilborn, C. J. Walters, Quantitative Fisheries Stock
Assessment: Choice, Dynamics and Uncertainty (Springer,
94. D. Gutiérrez et al., Rapid reorganization in ocean
biogeochemistry off Peru towards the end of the Little
Ice Age. Biogeosciences 6, 835848 (2009). doi: 10.5194/
95. S. Naqvi et al., Marine hypoxia/anoxia as a source of CH
and N
O. Biogeosciences 7, 21592190 (2010). doi: 10.5194/
96. L. Li et al., Revisiting the biogeochemistry of arsenic in the
Baltic Sea: Impact of anthropogenic activity. Sci. Total
Environ. 10.1016/j.scitotenv.2017.09.029 (2017).
pmid: 28926810
97. D. J. Janssen et al., Undocumented water column sink for
cadmium in open ocean oxygen-deficient zones. Proc. Natl.
Acad. Sci. U.S.A. 111, 68886893 (2014). doi: 10.1073/
pnas.1402388111; pmid: 24778239
98. L. Tiano et al., Oxygen distribution and aerobic respiration in
the north and south eastern tropical Pacific oxygen minimum
zones. Deep-Sea Res. Part I 94, 173183 (2014). doi: 10.1016/
99. L. A. Bristow et al., N
production rates limited by nitrite
availability in the Bay of Bengal oxygen minimum zone.
Nat. Geosci. 10,2429 (2017). doi: 10.1038/ngeo2847
100. C.J.Somes,A.Oschlies,A.Schmittner,Isotopic
constraints on the pre-industrial oceanic nitrogen budget.
Biogeosciences 10,58895910 (2013). doi: 10.5194/
101. L. Bohlen, A. W. Dale, K. Wallmann, Simple transfer functions
for calculating benthic fixed nitrogen losses and C:N:P
regeneration ratios in global biogeochemical models. Global
Biogeochem. Cycles 26, GB3029 (2012). doi: 10.1029/
102. D. J. Conley, J. Carstensen, R. Vaquer-Sunyer, C. M. Duarte,
Ecosystem thresholds with hypoxia. Hydrobiologia 629,
2129 (2009). doi: 10.1007/s10750-009-9764-2
103. M. J. McCarthy, S. E. Newell, S. A. Carini, W. S. Gardner,
Denitrification dominates sediment nitrogen removal and is
enhanced by bottom-water hypoxia in the Northern Gulf of
Mexico. Estuaries Coasts 38, 22792294 (2015).
doi: 10.1007/s12237-015-9964-0
104. T. Dalsgaard, L. De Brabandere, P. O. J. Hall, Denitrification in
the water column of the central Baltic Sea. Geochim.
Cosmochim. Acta 106, 247260 (2013). doi: 10.1016/
105. H. W. Bange et al., Marine pathways to nitrous oxidein
Nitrous Oxide and Climate Change (Earthscan, 2010),
pp. 3662.
106. D. L. Arévalo-Martínez, A. Kock, C. R. Löscher, R. A. Schmitz,
H. W. Bange, Massive nitrous oxide emissions from the
tropical South Pacific Ocean. Nat. Geosci. 8, 530533 (2015).
doi: 10.1038/ngeo2469
107. N. Gruber, Elusive marine nitrogen fixation. Proc. Natl. Acad.
Sci. U.S.A. 113, 42464248 (2016). doi: 10.1073/
pnas.1603646113; pmid: 27071128
108. J. Martinez-Rey, L. Bopp, M. Gehlen, A. Tagliabue, N. Gruber,
Projections of oceanic N
O emissions in the 21st century
using the IPSL Earth system model. Biogeosciences 12,
41334148 (2015). doi: 10.5194/bg-12-4133-2015
109. E. Ingall, R. Jahnke, Evidence for enhanced phosphorus
regeneration from marine sediments overlain by oxygen
depleted waters. Geochim. Cosmochim. Acta 58, 25712575
(1994). doi: 10.1016/0016-7037(94)90033-7
110. F. Scholz, J. McManus, A. C. Mix, C. Hensen, R. R. Schneider,
The impact of ocean deoxygenation on iron release from
continental margin sediments. Nat. Geosci. 7, 433437
(2014). doi: 10.1038/ngeo2162
111. D. J. Conley et al., Longterm changes and impacts of
hypoxia in Danish coastal waters. Ecol. Appl. 17, S165S184
(2007). doi: 10.1890/05-0766.1
112. K. Eilola, E. Almroth-Rosell, H. M. Meier, Impact of saltwater
inflows on phosphorus cycling and eutrophication in the
Baltic Sea: A 3D model study. Tellus Ser. A 66, 23985 (2014).
doi: 10.3402/tellusa.v66.23985
113. A. Cabré, I. Marinov, R. Bernardello, D. Bianchi, Oxygen
minimum zones in the tropical Pacific across CMIP5 models:
Mean state differences and climate change trends. Biogeosciences
12,54295454 (2015). doi: 10.5194/bg-12-5429-2015
114. O. Duteil, A. Oschlies,Sensitivity of simulated extent and future
evolution of marine suboxia to mixing intensity. Geophys. Res. Lett.
38, L06607 (2011). doi: 10.1029/2011GL046877
115. J. H. Bettencourt et al., Boundaries of the Peruvian oxygen
minimum zone shaped by coherent mesoscale dynamics.
Nat. Geosci. 8, 937940 (2015). doi: 10.1038/ngeo2570
116. S. Bushinsky, S. R. Emerson, S. C. Riser, D. D. Swift, Accurate
oxygen measurements on modified Argo floats using in situ
air calibrations. Limnol. Oceanogr. Methods 14, 491505
(2016). doi: 10.1002/lom3.10107
117. N. Revsbech et al., Determination of ultra-low oxygen
concentrations in oxygen minimum zones by the STOX
sensor. Limnol. Oceanogr. Methods 7, 371381 (2009).
doi: 10.4319/lom.2009.7.371
118. M. Larsen et al., In situ quantification of ultra-low O
concentrations in oxygen minimum zones: Application of
novel optodes. Limnol. Oceanogr. Methods 14, 784800
(2016). doi: 10.1002/lom3.10126
119. K. A. Rose et al., Does hypoxia have population-level effects
on coastal fish? Musings from the virtual world. J. Exp. Mar.
Biol. Ecol. 381, S188S203 (2009). doi: 10.1016/j.
120. K. de Mutsert et al., Exploring effects of hypoxia on fish and
fisheries in the northern Gulf of Mexico using a dynamic
spatially explicit ecosystem model. Ecol. Model. 331,142150
(2016). doi: 10.1016/j.ecolmodel.2015.10.013
121. K. E. Limburg et al., Tracking Baltic hypoxia and cod
migration over millennia with natural tags. Proc. Natl. Acad.
Sci. U.S.A. 108, E177E182 (2011). doi: 10.1073/
pnas.1100684108; pmid: 21518871
122. R. Miller Neilan, K. Rose, Simulating the effects of fluctuating
dissolved oxygen on growth, reproduction, and survival of
fish and shrimp. J. Theor. Biol. 343,5468 (2014). doi:
10.1016/j.jtbi.2013.11.004; pmid: 24269807
123. B. B. Hughes et al., Climate mediates hypoxic stress on fish
diversity and nursery function at the land-sea interface. Proc.
Natl. Acad. Sci. U.S.A. 112, 80258030 (2015). doi: 10.1073/
pnas.1505815112; pmid: 26056293
124. M. Yasuhara, G. Hunt, D. Breitburg, A. Tsujimoto, K. Katsuki,
Human-induced marine ecological degradation:
Micropaleontological perspectives. Ecol. Evol. 2, 32423268
(2012). doi: 10.1002/ece3.425; pmid: 23301187
125. M. A. Rice, Extension programming in support of public policy
for the management of aquaculture in common water bodies.
Aquacultura Indonesiana 15,2631 (2014).
126. R. R. Cayabyab et al., Histamine fish poisoning following
massive fishkill in Bolinao, Pangasinan, February 2002
(Regional Epidemiology and Surveillance Unit I Report 3,
Department of Health, Philippines, 2002).
127. A. H. Altieri et al., Tropical dead zones and mass mortalities
on coral reefs. Proc. Natl. Acad. Sci. U.S.A. 114, 36603665
(2017). doi: 10.1073/pnas.1621517114; pmid: 28320966
128. S. S. Rabotyagov et al., Cost-effective targeting of
conservation investments to reduce the northern Gulf of
Mexico hypoxic zone. Proc. Natl. Acad. Sci. U.S.A. 111,
1853018535 (2014). doi: 10.1073/pnas.1405837111;
pmid: 25512489
129. E. A. Davidson, D. Kanter, Inventories and scenarios of nitrous
oxide emissions. Environ. Res. Lett. 9, 105012 (2014).
doi: 10.1088/1748-9326/9/10/105012
130. S. P. Seitzinger, L. Phillips, Nitrogen stewardship in the
Anthropocene. Science 357, 350351 (2017). doi: 10.1126/
science.aao0812; pmid: 28751593
131. K. Van Meter, N. Basu, P. Van Cappellen, Two centuries of
nitrogen dynamics: Legacy sources and sinks in the
Mississippi and Susquehanna River Basins. Global
Biogeochem. Cycles 31,223 (2017). doi: 10.1002/
132. C. M. Duarte, D. J. Conley, J. Carstensen,
M. Sánchez-Camacho, Return to Neverland: Shifting
baselines affect eutrophication restoration targets. Estuaries
Coasts 32,2936 (2009). doi: 10.1007/s12237-008-9111-2
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 10 of 11
on January 4, 2018 from
133. W. M. Kemp, J. M. Testa, D. J. Conley, D. Gilbert,
J. D. Hagy, Temporal responses of coastal hypoxia to nutrient
loading and physical controls. Biogeosciences 6, 29853008
(2009). doi: 10.5194/bg-6-2985-2009
134. Chesapeake Bay Program DataHub (2017); http://data.
135. K. N. Es hleman , R. D. Sabo, De clinin g nitrat e-N yield s in
the Upper Potomac River Basin: What is really driving
progress under the Chesapeake Bay restoration? Atmos.
Environ. 146,280289 ( 2016). doi: 10.1016/
We thank IOC-UNESCO for financial support and for initiating
and supporting the Global Ocean Oxygen Network. We also
thank R. Diaz for help with updating the list of coastal sites that
have reported hypoxia (Fig. 1A); B. Michael and M. Trice of
the Maryland Department of Natural Resources for help w ith the
Maryland water quality database; and our many current and
past collaborators on deoxygenation research in coastal
systems, OMZs, the Black Sea, and elsewhere. Funding was
provided by National Oceanic and Atmospheric Administration
(NOAA)Center for Sponsored Coastal Ocean Research
grant NA10NOS4780138 and Maryland Sea Grant SA75281450-P
(to D.B.), NSF-EAR grant 1324095 (to L.A.L.), the Deutsche
Forschungsgemeinschaft via grant SFB754 (to A.O.), and the
Fonds National de la Recherche Scientifique and the BENTHOX
program grant T.1009.15 (to M.G.). This study was partly
supported by the BONUS COCOA project (grant 2112932-1),
funded jointly by the European Union and the Swedish
Research Council for Environment, Agricultural Sciences
and Spatial Planning.
Breitburg et al., Science 359, eaam7240 (2018) 5 January 2018 11 of 11
on January 4, 2018 from
Declining oxygen in the global ocean and coastal waters
Yasuhara and Jing Zhang
Grant C. Pitcher, Nancy N. Rabalais, Michael R. Roman, Kenneth A. Rose, Brad A. Seibel, Maciej Telszewski, Moriaki
Garçon, Denis Gilbert, Dimitri Gutiérrez, Kirsten Isensee, Gil S. Jacinto, Karin E. Limburg, Ivonne Montes, S. W. A. Naqvi,
Denise Breitburg, Lisa A. Levin, Andreas Oschlies, Marilaure Grégoire, Francisco P. Chavez, Daniel J. Conley, Véronique
DOI: 10.1126/science.aam7240
(6371), eaam7240.359Science
, this issue p. eaam7240Science
which ultimately will cause societal and economic harm.
oxygen minimum zones. In the longer term, these conditions are unsustainable and may result in ecosystem collapses,
result in improvements in local fisheries, such as in cases where stocks are squeezed between the surface and elevated
sediments and fundamental shifts in the availability of key nutrients. In the short term, some compensatory effects may
are changing ocean biogeochemistry and increasing oxygen consumption. This results in destabilization of−−activities each resulting from human−−the open ocean and coastal waters. Rising nutrient loads coupled with climate change
review the evidence for the downward trajectory of oxygen levels in increasing areas of et al.deoxygenation. Breitburg
As plastic waste pollutes the oceans and fish stocks decline, unseen below the surface another problem grows:
Beneath the waves, oxygen disappears
This article cites 126 articles, 27 of which you can access for free
Terms of ServiceUse of this article is subject to the
is a registered trademark of AAAS.Science
licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. The title
Science, 1200 New York Avenue NW, Washington, DC 20005. 2017 © The Authors, some rights reserved; exclusive
(print ISSN 0036-8075; online ISSN 1095-9203) is published by the American Association for the Advancement ofScience
on January 4, 2018 from
... Earth's global ocean has been steadily losing oxygen due to warming-induced decreases in oxygen solubility, accelerated respiration, increases in water column stratification and coastal eutrophication, commonly referred to as ocean deoxygenation [1][2][3] . Since the 1950s, the open ocean has lost more than 2% of its dissolved oxygen (DO), oxygen minimum zones have expanded and shoaled, and hundreds of coastal sites have reported severe hypoxic conditions (that is, aquatic oxygen levels below a given environmental threshold) [1][2][3][4][5][6] . ...
... Earth's global ocean has been steadily losing oxygen due to warming-induced decreases in oxygen solubility, accelerated respiration, increases in water column stratification and coastal eutrophication, commonly referred to as ocean deoxygenation [1][2][3] . Since the 1950s, the open ocean has lost more than 2% of its dissolved oxygen (DO), oxygen minimum zones have expanded and shoaled, and hundreds of coastal sites have reported severe hypoxic conditions (that is, aquatic oxygen levels below a given environmental threshold) [1][2][3][4][5][6] . These trends will continue in the future, as ocean surface oxygen concentrations are projected to decrease by an additional 3.2-3.7% ...
... by 2100, with oxygen loss expected to emerge across 59-80% of the ocean by 2050 4 . While trends of deoxygenation in the open ocean and the occurrence of temperate hypoxic and anoxic zones (defined as ≤2 mg O 2 l −1 and 0 mg O 2 l −1 (~61 µmol O 2 kg −1 and 0 µmol O 2 kg −1 ) respectively 6 ) are relatively well documented [1][2][3]6 , there has been less focus on tropical coastal ecosystems, such as coral reefs [7][8][9] , despite mounting evidence that modern hypoxic events can lead to mass mortality of coral reef taxa (for example, refs. [7][8][9][10]. ...
Full-text available
Ocean deoxygenation is predicted to threaten marine ecosystems globally. However, current and future oxygen concentrations and the occurrence of hypoxic events on coral reefs remain underexplored. Here, using autonomous sensor data to explore oxygen variability and hypoxia exposure at 32 representative reef sites, we reveal that hypoxia is already pervasive on many reefs. Eighty-four percent of reefs experienced weak to moderate (≤153 µmol O2 kg⁻¹ to ≤92 µmol O2 kg⁻¹) hypoxia and 13% experienced severe (≤61 µmol O2 kg⁻¹) hypoxia. Under different climate change scenarios based on four Shared Socioeconomic Pathways (SSPs), we show that projected ocean warming and deoxygenation will increase the duration, intensity and severity of hypoxia, with more than 94% and 31% of reefs experiencing weak to moderate and severe hypoxia, respectively, by 2100 under SSP5-8.5. This projected oxygen loss could have negative consequences for coral reef taxa due to the key role of oxygen in organism functioning and fitness.
... Greenhouse gases, such as CO 2 and CH 4 , accumulate in the atmosphere resulting in increased surface temperatures and are also dissolved in the world´s oceans [3]. These combined effects lead to changes in marine salinity, acidification, stratification, deoxygenation, and increased microbial metabolic rates [4][5][6]. For example, long-term temperature observations of the upper 2000 m of the oceans show an average temperature increase of 0.09°C since 1955 that is equivalent to an energy increase of 24 × 10 22 J yr −1 [7]. ...
Full-text available
Besides long-term average temperature increases, climate change is projected to result in a higher frequency of marine heatwaves. Coastal zones are some of the most productive and vulnerable ecosystems, with many stretches already under anthropogenic pressure. Microorganisms in coastal areas are central to marine energy and nutrient cycling and therefore, it is important to understand how climate change will alter these ecosystems. Using a long-term heated bay (warmed for 50 years) in comparison with an unaffected adjacent control bay and an experimental short-term thermal (9 days at 6–35 °C) incubation experiment, this study provides new insights into how coastal benthic water and surface sediment bacterial communities respond to temperature change. Benthic bacterial communities in the two bays reacted differently to temperature increases with productivity in the heated bay having a broader thermal tolerance compared with that in the control bay. Furthermore, the transcriptional analysis showed that the heated bay benthic bacteria had higher transcript numbers related to energy metabolism and stress compared to the control bay, while short-term elevated temperatures in the control bay incubation experiment induced a transcript response resembling that observed in the heated bay field conditions. In contrast, a reciprocal response was not observed for the heated bay community RNA transcripts exposed to lower temperatures indicating a potential tipping point in community response may have been reached. In summary, long-term warming modulates the performance, productivity, and resilience of bacterial communities in response to warming.
... SDG implementers at all levels ( Figure 3) have the task of recognising that the ICRS SPI, Rebuilding Coral Reefs: A Decadal Grand Challenge [35], and global ocean financing models need the integration of ILO decent work and healthy job creation as per the SDG 8 targets [25,30,63,80]. For SIDS to support reskilling and upskilling, their blue workforce urgently requires innovation in SPI at the UN that is inclusive of the islands' marine scientific community, industry, and private sector actors [47,81,82]. The science-to-policy process mapping the coral reef economy driven from the diving industry has frequently been referenced by grantmakers in the global coral reef funding prospectus [46]. ...
Full-text available
To achieve coral reef resilience under Agenda 2030, island governments need to institutionalise a competent blue workforce to expand their reef resilience initiatives across economic organisations and industries. The ability of island governments to shape new policies for sustainable island development relying on natural capital, such as coral reefs, has been hampered by structural and institutional deficiencies on both sides of the science-policy interface (SPI) at the UN. Using a qualitative research design, this article explores the science-policy interface (SPI) policy paper, Rebuilding Coral Reefs: A Decadal Grand Challenge and the role of this SPI in guiding UN coral reef financing for island states. This article uses the dive industry to investigate the needs of policymakers in island states via a conceptual framework for policy analysis. This article highlights the gaps of the SPI from the perspective of the global south and is beneficial for the islands selected under the Global Coral Reef Investment Plan. The article highlights the results of the SPI to island decision makers, which indicate that, without a policy framework that includes space for industrial policy within UN SPI, island governments will continue to fall into financial traps that constrain their efforts in operationalising their blue workforce. The study concludes that interlinked SDGs, such as SDG 9 and SDG 8, which focus on linking industrial innovation and infrastructure with decent work, as well as SDG 16 and 14.7, provide SIDS institutions with integrated policy approaches capable of bridging the divides between the scientific community, the diving industry, and island governments and that this needs to be further explored at all levels.
... In the North Sea, changes in the net primary production are expected to impact transfer of energy in the food web, with consistent responses over a large range of habitats (Steger et al., 2019;Frelat et al., 2022). Excessive increase in primary production and subsequent degradation of organic material at depth can lead to oxygen deficiency at vulnerable locations (Ciavatta et al., 2016;Breitburg et al., 2018). Increase in water temperature may induce an additional risk of hypoxia. ...
... Enhanced nutrient concentrations in the water column (Tengberg et al., 2003;Kalnejais et al., 2010;Niemistö and Lund-Hansen, 2019) have been observed to harm coastal ecosystems worldwide (Malone and Newton, 2020). The list of detrimental effects includes harmful algal blooms, eutrophication, habitat loss, the disappearance of macrobenthic communities, coastal acidification, deoxygenation, and dead zones (Qin et al., 2004;Breitburg et al., 2018;Chen et al., 2018;Malone and Newton, 2020). Indeed, studies in lacustrine environments have reported eutrophic conditions and algal blooms following resuspension events (Ogilvie and Mitchell, 1998;Qin et al., 2004;Schallenberg and Burns, 2004;Dzialowski et al., 2008). ...
Full-text available
Intertidal coastal sediments are important centers for nutrient transformation, regeneration, and storage. Sediment resuspension, due to wave action or tidal currents, can induce nutrient release to the water column and fuel primary production. Storms and extreme weather events are expected to increase due to climate change in coastal areas, but little is known about their effect on nutrient release from coastal sediments. We have conducted in-situ sediment resuspension experiments, in which erosion was simulated by a stepwise increase in current velocities, while measuring nutrient uptake or release in field flumes positioned on intertidal areas of a tidal bay (Eastern Scheldt) and an estuary (Western Scheldt). In both systems, the water column concentration of ammonium (NH 4 +) and nitrite (NO 2 −) increased predictably with greater erosion as estimated from pore water dilution and erosion depth. In contrast, the phosphate (PO 4 3−) dynamics were different between systems, and those of nitrate (NO 3 −) were small and variable. Notably, sediment resuspension caused a decrease in the overlying water PO 4 3− concentration in the tidal bay, while an increase was observed in the estuarine sediments. Our observations showed that the concentration of PO 4 3− in the water column was more intensely affected by resuspension than that of NH 4 + and NO 2 −. The present study highlights the differential effect of sediment resuspension on nutrient exchange in two contrasting tidal coastal environments.
... These hypoxic zones are located mainly along coasts with large populations and developed economies, such as western and northern Europe, eastern and western United States, eastern China, and Japan (Breitburg et al., 2018). Hypoxic events seriously threaten coastal and marine ecosystems and have become a focus of research worldwide (Diaz, 2001;Dagg et al., 2007;Schmidtko et al., 2017). ...
Full-text available
Dissolved organic matter (DOM) in the ocean is one of the largest carbon pools on Earth. Microbial metabolism is an important process that shapes the marine DOM pool. Current studies on the interactions between microorganisms and DOM focus mainly on oxic environments. Few studies have addressed the molecular characteristics of DOM in microbial-mediated transformation under anoxic/hypoxic conditions. As a result of deteriorating water quality due to eutrophication and global warming, anoxia occurs frequently in coastal waters. In this study, we performed an experiment to investigate changes in microbial community responses and the molecular characteristics of DOM in microbial-mediated transformation under hypoxic conditions. We compared microbial-mediated DOM transformation at different dissolved oxygen levels (7, 5, and 2 mg L −1) and in different media (natural and artificial seawater with and without laminarin). We also investigated differences in DOM composition between groups using spectroscopic analysis and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry. The results showed decreased microbial metabolic activity and delayed community succession at low oxygen (≤2 mg L −1) in natural seawater supplemented with laminarin. The growth of strictly aerobic bacteria such as Pseudomonadaceae and Sphingomonadaceae was inhibited and the total organic carbon utilization rate was reduced by 36.9-46.7% from 4 to 32 days. Moreover, tyrosine-like and tryptophan-like components were preserved, while DOM humification and modified ar-omaticity index were significantly reduced under low oxygen conditions. This experiment provides justification for further study of the processes and mechanisms of improved labile DOM preservation in anoxic estuarine and coastal waters.
... Over the past few decades, a long-term global ocean deoxygenation trend has clearly emerged as an indirect result of anthropogenic climate change (Breitburg et al., 2018;Schmidtko et al., 2017), with particularly rapid oxygen loss in the Northeast Pacific (Cummins & Ross, 2020;Keeling et al., 2010;Ross et al., 2020;Schmidtko et al., 2017;Whitney et al., 2007). As a consequence of the decreasing ocean oxygen baseline, extreme low oxygen events (i.e., large anomalies relative to a climatological reference) are projected to become more frequent and intense (Gruber et al., 2021). ...
Full-text available
Plain Language Summary Most marine organisms consume oxygen, and are therefore impacted when seawater oxygen concentrations reach low values. Extreme low oxygen concentrations are rare in the coastal waters of British Columbia, Canada. However, unusually strong oxygen depletion was observed off the coast of Vancouver Island during summer 2021. Unusually strong, early season upwelling winds along the California coast impacted Vancouver Island by causing nutrient‐rich water to be mixed into the surface, stimulating a large and earlier than usual spring phytoplankton bloom. Decomposition of the bloom‐derived organic carbon consumed local subsurface oxygen throughout the spring and summer. These subtle changes in timing and intensity of seasonal processes likely caused this low oxygen event, which was also associated with high concentrations of inorganic carbon, leading to ocean acidification. Such extreme low oxygen events, even if short‐lived, can have a significant impact on marine ecosystems, restricting the habitat available for groundfish species, such as Pacific halibut, and impacting the formation of carbonate shells by various organisms. The drivers of extreme low oxygen events are projected to intensify as climate change progresses.
Full-text available
Human modification of coastal ecosystems often creates barriers to fish movement. Passive acoustic telemetry was used to quantify movement patterns and habitat use of red drums (Sciaenops ocellatus) within and around a complex of coastal impoundments, and explored how the presence of artificial structures (i.e., bollards and culverts) and a hypoxia-related mortality event impacted fish movement. Results indicated bollards impede the movement of individuals with head widths greater than the mean distance between bollards (~16.0 cm). Red drum home range area and daily distance traveled were related to water dissolved oxygen concentrations; as oxygen levels decreased, fish habitat use area decreased initially. However, continued exposure to hypoxic conditions increased fish cumulative daily distance traveled. When exposed to anoxic waters, fish daily distance traveled and rate of movement were greatly reduced. These findings suggest prolonged exposure to low dissolved oxygen in combination with artificial structures can reduce movement of red drum, increase risk of mortality, and decrease habitat connectivity. Constructing and maintaining (sediment and biofouling removal) larger culvert openings and/or using wider bollard spacing would improve water circulation in impoundments, increase habitat connectivity, and facilitate movement of large sportfish inhabiting Florida’s coastal waters.