oxygen decline in coastal waters - xiamen university · upwelling_category 0.0392 log10 (openness)...
TRANSCRIPT
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Oxygen Decline in Coastal Waters
GO2NEGlobal Ocean
Oxygen NEtwork
Denise BreitburgSmithsonian Environmental
Research Center
Hayle Estuary, UK, image: https://www.rspb.org.uk/reserves-and-
events/reserves-a-z/hayle-estuary/
Mattole River Estuary, California, USA
Image: https://en.wikipedia.org/wiki/Estuary
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What am I including in coastal waters?
Estuaries, semi-enclosed seas, embayments, fjords, coastal lagoons,
etc. – Not open wave-swept coasts
Water bodies in which oxygen depletion is strongly influenced by their local watershed (catchment).
Will rely heavily on systems in the US and Europe for examples – I hope
during the discussion and the rest of the week everyone can share
observations from the rest of the world
UNITS: 1 mg/L ~ 1.4 ml/L ~ 31 μmol/L
Hypoxia definition: oxygen (concentration, saturation, partial pressures)
sufficiently low to negatively impact biological or ecological processes.
• 2 mg/L conventional cutoff, but not ideal to use
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Outline:
Causes
Patterns
Ecological Effects
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Jenny et al., 2016
Low oxygen occurs naturally
in many water bodies
Baltic
Sea
Black
Sea
Paleo evidence:
Instances of low
oxygen in the past in
some systems even
where nutrients have
now made oxygen
depletion more severe and extensive
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1) Diaz map
• since 1950 - Over 600 coastal systems identified with <20-25% oxygen
saturationDiaz and Rosenberg 2008, Diaz
unpublished, Breitburg et al., 2018
Number of water bodies reporting hypoxia has increased
dramatically since the mid-20th century
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Based on date of earliest verified
measurement of hypoxia. Probably
more unreported
‘Diaz database’
Caveate: The more we look the
more we find. Reporting lower in
developing economies
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Expansion of hypoxic area
through time - Baltic Sea
Carstensen et al. (2014)
1,500 km2 65,000 km225,000 km2
Within systems oxygen depletion getting more severe and widespread
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Image: www.renewableresourcescoalition.org/
overpopulation-causes-effects-solutions/
Invention of chemical fertilizers in
early 20th century:
Haber–Bosch process converts
atmospheric N2 to ammonia (NH3)
though a reaction with H2
Hot, sour and breathlessTurley et al., 2016
Underlying problems – increasing human
population, use of chemical fertilizers to
feed that population, and increasingly,
climate change
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phytoplankton
zooplanktonN, P, Si
Dead cells
Fresh
water
Nutrients
(N&P)
Organic
carbon
Sediment
Modified from: https://upload.wikimedia.org/wikipedia/commons
/d/dd/Scheme_eutrophication-en.svg
Eutrophication – too much nutrients – too much production –
consequence is low oxygen
NOx, NH3/NH4+,
DON
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Main nutrient sources include agriculture, sewage and burning of fossil fuels
Baltic Proper 2014 (Sources and pathways of
nutrients to the Baltic Sea
HELCOM PLC-6)
TN TP
Riverine
sources
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Nutrients important but high nutrient loads not whole story
Openness~
residence time
HYPOFIN – unpublished data
Model R2= 0.72 p<0.003 Source of variation p upwelling_category 0.0392 log10 (openness) 0.0237 log10 basin+atmosTN 0.0472 warmest month mean oC 0.078
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Reduced O2 introduction →
reduced ventilation (mixing)
long residence time
darkness
Balance tipped towards oxygen decline
Increased respiration →
nutrient enrichment
high biomass/oxygen demand
increased temperature
***Same basic processes as open ocean but very different
spatial & temporal scales
Fennel & Testa 2018
Cause of oxygen decline
*Aerobic respiration O2 → CO2
*Introduction of O2 (photosynthesis,
ventilation)< O2 consumption
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Fennel &Testa 2018
Most important factors:
Oxygen content of source water
Respiration rate
Residence time
Nutrient loads
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Untreated sewage tends to cause the most
extreme oxygen depletion
Manila Bay, 2010<20% treated
sewage,
10 million people in
watershed
River Thames , England
(raw sewage in 1800s)
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Mariager Fjord, Denmark 1997 anoxia eventFallesen et al. 2000
Every year
Long residence time
High nutrient loads
High chlorophyl
1997
Warmer weather
Low wind mixing
Increased oxygen
depletion
Mussels die
Feedbacks can be important
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Temporal patterns of hypoxia in nutrient-enriched systems
Persistent
(years to millennia)
Seasonal
Episodic
Diel/tidal
Chesapeake
Baltic
Black
Weeks Bay
Venice Lagoon
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• year round stratification in deep basins
• Seasonal cycle in shallower water
• hypoxic/anoxic volume sensitive to inflow, warming
Persistent for years to thousands of years
(e.g. Baltic proper, Black Sea)
Black Sea
Image: https://geologycafe.com/oceans/chapter9.html
Oxygen penetration depthCapet et al., 2016
Seasonal hypoxia, NW shelf
HELCOM 2009 Conley et al., 2008
Baltic Sea
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Seasonal hypoxia- stratified temperate estuary
Chesapeake Bay
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dis
so
lve
d o
xyg
en
(m
g/L
)
0
2
4
6
8
10
12
Respiration dominates during dark lowest
DO around dawnTemporal patterns vary; timing as well as duration
and severity may determine which
processes/species are affected
Diel & tidally driven hypoxia
– sub-daily cycles
-natural but exacerbated by high nutrient loads
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dis
so
lve
d o
xyg
en
(m
g/L
)
0
2
4
6
8
10
12
time of day
pH
6.5
7.0
7.5
8.0
8.5
Oxygen and pH daily cycles
Daylight –
Photosynthesis dominates
+ oxygen, -CO2
Tight correlation between oxygen & pH/pCO2
Chesapeake Bay
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Boynton et al., 1996
Chlorophyll important driver
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Mangrove ponds in Belize & Panama
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Diel-cycling hypoxia
Harness Creek,
MD
Jun Jul Aug Sep
SERC
Creates temporal & spatial variability at a
variety of scales
Affects productive refuge from deep-
water hypoxia
Affects habitat that is important predator
refuge for small & juvenile fish
Sites <
2 m
depth
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Upwelling/intrusions of low oxygen water
nearshoreCrab jubileeMobile Bay (image: NOAA)
Local weather influence & decadal climate variability affect
spatial/temporal patterns and the relationship between N loads
and hypoxia extent
Chesapeake Bay hypoxia :Large-scale climate cycles and local wind
directionsMurphy et al., 2011
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Altieri & Gedan 2015
Warming
Decreases oxygen introduction
• Stratification (intensity & duration)
• currents
Alters patterns of precipitation & nutrient delivery
Decreases oxygen solubility
Increases oxygen consumption
Respiration rates
Climate change will worsen oxygen depletion in most coastal systems
Meier et al., 2011
Baltic – rising temperature increases oxygen depletion, increasing precipitation
increases stratificationBusiness as usual
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Effects: If you can’t breathe,
nothing else matters(American Lung Association)
• important force in evolution
•creates biologically &
ecologically important spatial and
temporal structure
• decreases biodiversity
• alters biogeochemical cycles
• direct exposure decreases
survival, growth, reproduction,
and increases disease
• alters predator-prey interactions
• effects found tropics – to – poles
• fisheries affected – location,
value, catch
• economies and human health
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Declining oxygen – Important force in evolution through geological time and now
Decker et al., 2003
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Robert J. Diaz, and Rutger Rosenberg Science
2008;321:926-929
Deoxygenation increases energy flow to microbes
Wright 2012
Terminal electron acceptors
Hood Canal
(Washington State, US)
Speitz et al., 2015
94 → 375 μmol/L
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Hypoxia typically decreases biomass and diversity-
especially for sessile & low-mobility species
Villna s̈ et al., 2004
Benthic invertebrates – Baltic Sea
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Hypoxia, and the nutrients and warming that cause deoxygenation, create
biologically, ecologically & economically relevant spatial structure- need to
consider effects both within hypoxic water and larger time & space scales
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Behavior (or lack thereof) determines effects
High
oxygen
Chronic
effects
Lethal
conditionsHighly mobile species
reduced growth & reproduction
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0 1 2 3 4 5 6 7 8
0.0
0.2
0.4
0.6
0.8
1.0
Bottom dissolved oxygen (mg L-1)
sea nettles
ctenophores
0 1 2 3 4 5 6 7 8
Pro
po
rtio
na
l d
en
sity
0.0
0.2
0.4
0.6
0.8
1.0
0 1 2 3 4 5 6 7 8
0.0
0.2
0.4
0.6
0.8
1.0
adult copepods and copepodites
Bottom dissolved oxygen (mg L-1)
bay anchovy larvae
naked goby larvae
0 1 2 3 4 5 6 7 8
0.0
0.2
0.4
0.6
0.8
1.0
0 1 2 3 4 5 6 7 8
0.0
0.2
0.4
0.6
0.8
1.0
random
distribution
Keister et al 1998
Breitburg et al. 1997
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Reproductive to population-level effects
Normoxic Hypoxic
10
3e
gg
s fish
-1
Normoxic
sites
Hypoxic
sites
Atlantic croaker, Gulf of Mexico
Thomas & Rahmen 2011 Modified from Rose et al., 2018; croaker image: sc.dnr.gov
Low N – High O2
High N - Hypoxia
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Data& images: Kevin Craig (NOAA)Total CPUE
0 - 1
1 - 2
2 - 4
> 4
Bottom Oxygen (mg l-1)
Combination of hypoxia, species behavior and fishers behavior may
increase fishing mortality & increase likelihood of overfishing
2-4
0-1
1-2
>4
DO (mg l-1)
20 m
80 m
50 km
Shrimp Vessel Sightings Shrimp abundance
Craig 2012; Purcell et al., 2017
Northern Gulf of Mexico
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Data& images: Kevin Craig (NOAA)
Hypoxia creates economically relevant spatial structure
0
10
20
30
40
50
60
70
80
90
7000
9000
1100
0
1300
0
1500
0
1700
0
1900
0
2100
0
2300
0
Sp
atia
l Ov
erla
p
90-d Mean Hypoxia Area (km2)
R2=0.32
2008
2004-2016
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Low oxygen exacerbates acquisition & progression of disease
Generally reduces immune response by decreasing phagocytosis and
production of reactive oxygen species
Host Pathogen
taxa
Pathogen/
disease
Dino-flagellate
Perkinsus marinus (dermo)
Keppel et al., 2016Breitburg et al., 2015b
virus White spot syndrome virus
Lehman et al., 2016
protist Amoebic gill disease Fisk et al., 2002
helminth Anguilla crassus Gollock et al., 2005
bacteria Vibrio campbelli Macey et al., 2008
bacteria Vibrio parahemolyticus
Henroth et al., 2015
bacteria Vibrio parahemolyticus
Boleza et al., 2010 Breitburg et
al., in press
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}2008
2009
Patuxe
nt
julian day
160 180 200 220 240 260 280 300
Daily
min
imum
[D
O]
(mg l
-1)
0.0
2.0
4.0
6.0
8.0
10.0
HCR
HPL
LMN
MUL
SERC
Jun Jul Aug OctSep
3 mg/l
2 mg/l
1 mg/l
Even cycling low oxygen can increase susceptibility to pathogens
Breitburg et al., 2015
Mean daily minimum DO during days with salinity > 11 (mg/L)
2.0 3.0 4.0 5.0 6.0 7.0
Pe
rkin
su
s p
reva
len
ce
(%
)
40
50
60
70
80
90
100
2008
2009
Darryl Hondorp
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Atlantic menhaden in Narragansett Bay
Productive Fisheries
Fish kills
Contrasting effects of
nutrient enrichment
and hypoxia
0
20
40
60
80
100
120
140
160
0 100 200 300 400 500
PRIMARY PRODUCTION, g C m-2 y-1
AN
NU
AL F
IS
HE
RY
LA
ND
IN
G, K
g H
a-1
Nixon 2002Eutrophication severity
Fis
heri
es
land
ings
Caddy 1993
hypoxia
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La
ndin
gs f
ish a
nd m
obile
inve
rte
bra
tes
(lo
g1
0 k
g k
m -
2 y
ea
r -1
)
2.5 3.0 3.5 4.0 4.5 5.0 5.5
2.5
3.0
3.5
4.0
4.5
<1% hypoxia
2-9% hypoxia
10-77% hypoxia
N loadings (log10 kg km -2 surface area year -1)
Rose et al., in press; redrawn from Breitburg et al., 2009
Eutrophic coastal
systems still
function as
‘protein
factories’for
mobile catch, but
individual
important species
can be harmed,
and long-term
consequences are
uncertain
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Breitburg et al., 2009
Hypoxia reduces the production efficiency of
systems: less biomass & catch/N load
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•Behavior, growth and fishing
practices result in spatial and
temporal averaging by fish and
fisheries
Hypoxia direct effectsdominant
Direct and indirect effects of hypoxia and increased production
Increased production and Indirect effects of hypoxia
Increased production effects only
landland
Evidence of negative population-level
effects elusive:
Compensatory mechanisms
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•turbidity as a substitute
refuge for submerged
macrophytes
Compensatory mechanisms
Abundant Solomons
Island
SAV during May 1938
compared to Summer 1999
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Compensatory mechanisms
•Behavior, growth and fishing
practices
result in spatial and temporal
averaging by fish and fisheries
•overfishing keeps populations below
habitat-determined carrying capacity –
therefore little effect of decreased habitat
effects strongest when pops high and
affected habitat is critical and limited
•turbidity as a substitute refuge for
submerged macrophytes
Deoxygenation = destruction of an
ecosystem even where it does not affect
fisheries
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Human dimension – dependence on local resources may
determine effects
Bolinao, PhilippinesSan Diego-McGlone et al., 2008
Finfish aquaculture
Increased fish biomass and added feed
Increased oxygen demand
Hypoxia
Fish kills
Economic losses
Human impact
Photo: http://kickerdaily.com/wp-content/uploads/2014/06/Batangas-Fish-Kill1.jpg
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Laajalahti Bay, Gulf of Finland
Kauppila et al., 2005Testa et al., 2018 b
Chesapeake Bay, US
Nutrient reduction can work but will be more difficult as waters warm
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Modified from Bopp et al., 2013
Low oxygen does not occur in isolation –
oxygen decline in a multiple stressor world
Oxygen change
pH changeTemperature change
1o production change
Photo: http://oceans.ubc.ca/2018/08/01/fishing-fleets-travelling-further-to-catch-fewer-fish-2/
Management & prediction requires
that we consider this
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Steps to restore ocean oxygen can directly benefit people
http://7-themes.com/data_images/out/59/6971871
-big-ocean-wave.jpg
• Reduce nutrients
• Reduce greenhouse gas
emissions
• Adaptation strategies
manage resources to
acknowledge and
compensate for the
problem
Improved sanitation,
agriculture efficiency &
air quality
Avoiding the
devastation of rising
temperatures and rising
seas
Managing fisheries,
including aquaculture,
more sustainably
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Take home messages:
Causes – combination of physical characteristics of system,
anthropogenic nutrients and warming
Patterns – minutes to thousands of years; meters to 10s of
thousands of km
Ecological Effects- All aspects of biology, ecology, local
fisheries
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Challenge to us:
Increase Engagement with civil society and policy makers
Increase & Improve Communication
big picture
develop language to communicate importance
effects on people and on things people care about
(our children)
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GO2NEGlobal Ocean Oxygen NEtwork
A major goal of GO2NE is to help
Increase research capacity and
knowledge transfer.
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end
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Nutrient overenrichment
We have solutions:
agriculture
wastewater treatment
reduced NOx emissions from power generation
Planning, regulations and clear goals critical
Will, $$$
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Southwest River Estuary
Prince Edward Is, Canada
(explosive increase in fertilizer use;
inappropriate crop choice)
…but a combination of excess fertilizer runoff and
restricted circulation can also lead to complete
anoxia
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Chesapeake Bay
Gedan et al, unpubl
Breitburg et al.,
2015
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Ludsin et al., 2009
Behavior determines spatial distributions – especially vertically
Low
DOFish
avoid
bottom
Can concentrate or separate predators and their prey