Oxygen-depleted water in the Columbia River estuary:

Observations and consequences

Curtis Roegner NOAA Fisheries

Estuary Partnership

Science Work Shop

23 April 2013

Overview of dissolved oxygen

Columbia River measurements

Consequences for migrating salmon and crab

Summary and management implications

Overview of talk

Juvenile salmon Dungeness crab

Gas exchange

Stratification limits oxygen exchange

Organic matter decomposition uses O2 and produces CO2

Mixing by wind, tides, river flow can limit stratification

Stratification enhanced by temperature and salinity gradients

Dep

th

Mixing

Stratification

[Oxygen]

Dep

th

Well mixed oxygen

profile

Oxygen reduced

in bottom water

Nutrient input & eutrophication

Organic matter decomposition leads to low dissolved oxygen

Dep

th

[Oxygen]

Dep

th

Phytoplankton can

supersaturate

oxygen in the

water column….

…but O2 is consumed

by their decomposition

Phytoplankton bloom

Sinking

&

Decay O2 CO2

O2 CO2

Heterotrophic respiration in poorly ventilated water is what causes low DO

in lakes, estuaries and the oceans.

Scientific Assessment of Hypoxia in U.S. Coastal Waters

Effect of low DO on biota: Differential susceptibility

Overview

Columbia River measurements

Consequences for migrating

salmon and crab

Summary and management

implications

Sublethal effects:

Migration

Quiescence

Reduced feeding

and growth

Altered

predator – prey

relationships

Dissolved

oxygen

concentration

(mg/L)

0

2

4

6

8

10

12 Supersaturated

Normoxic

Mild biological stress

Moderate biological stress

Severe biological stress (hypoxia)

Anoxia

Oxygen category

Characterization of DO levels

Juvenile salmon prefer > 9 mg/L and avoid 6 mg/L

Reduced swimming speed and growth < 4 mg/L

Dungeness crabs reduce activity ~50% saturation

Estuarine-ocean linkage and

physical drivers

Characterization of DO levels –

biological perspective

DO observations in the CRE

2006-2008

Oxygen production

Consequences for migrating

salmon and crab

Salinity

(psu)

0 15 30

Dissolved

oxygen

concentration

(mg/L)

0

2

4

6

8

10

12 Supersaturated

Normoxic

Mild biological stress

Moderate biological stress

Severe biological stress (hypoxia)

Anoxia

Oxygen category

Dissolved oxygen sources and sinks

No relation to salinity

Conservative (linear mixing) with reduced DO in ocean end-member

Conservative (linear mixing) with reduced DO in river end-member

Non-conservative mixing with an estuarine source

Dissolved oxygen observations in the CRE

Data sources

Shipborne sensors

CTD from transects or anchor stations

Moorings

Wind

Tide

Saturn system (Salinity, DO, ect)

Definitions

Columbia River measurements

Consequences for migrating

salmon and crab

Summary and management

implications

http://www.stccmop.org/

-124.1 -124.0 -123.9 -123.8 -123.746.1

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ML03

ML04ML05

ML07

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SC02

SC03

SC04SC05SC06SC07SC08

SC09

SC10

SC11

SC12

SC13

SC14

SC15SC16

AS-B

AS-M

AS

AS

Tidal station

CRB Buoy (local wind)

Columbia River Estuary stations

Dissolved oxygen observations in the CRE

0 10 20 30

0

2

4

6

8

10

12

Salinity (ppt)

O2 (

mg/

L)

MILD

MODERATE

HYPOXIC

River

SUPERSATURATED

Ocean

Upwelledwater

Estuary

Low DO

in ocean water

Normal concentrations

in river water

Salinity

(psu)

Dissolved

oxygen

concentration

(mg/L)

No relation to salinity

Conservative (linear mixing) with reduced DO in ocean end-member

Conservative (linear mixing) with reduced DO in river end-member

Non-conservative mixing with an estuarine source

Supersaturated

in 0-20 psu

NORMOXIC

O2 c

on

cen

trat

ion

(mg

L-1

)

A. 22 Aug B. 8 Sep C. 13 Sep D. 21 Sep E. 15 Oct

A B C D E

2006

0 10 20 30

0

2

4

6

8

10

12

Salinity (ppt)

0 10 20 30 0 10 20 30 0 10 20 30

% O

2 satu

ration

0

20

40

60

80

100

120

0 10 20 30

210 220 230 240 250 260 270 280 290 300

-0.15

-0.10

-0.05

0.00

0.05

Win

d s

tres

s

(N m

-2)

Wat

er l

evel

(m

)

0

2

Lu

nar cy

cle0.000.250.500.751.00

Physical time series and O2/salinity diagrams 2006

Upwelling

Downwelling

6 mg/L

Saturation

Dep

th (

m)

Distance (km)

A. Cruise A

-20

-10

0

0 10 20 30-20

-10

0

-20

-10

0

0 10 20 30-20

-10

0

-20

-10

0

0 10 20 30-20

-10

0

-20

-10

0

0 10 20 30-20

-10

0

D. Cruise E C. Cruise C

B. Cruise D

Depth-distance transects of salinity and oxygen: South Channel

Low

DO

High

salinity

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South Channel

Upwelling Downwelling

180 190 200 210

Win

d s

tres

s

(N m

-2)

-0.20

-0.15

-0.10

-0.05

0.00

0.05

Wat

er l

evel

(m

)

0

2

Lunar cy

cle0.000.250.500.751.00

2008

O

0 10 20 300 10 20 30

0

2

4

6

8

10

12

Salinity (ppt)

O2

conce

ntr

atio

n

(mgL

-1)

O. 10 July R. 20 JulyP. 13 July Q. 18 July

0 10 20 30 0 10 20 30

P

Q R

Physical time series and O2/salinity diagrams: 2008

10 Jul 2008

20 Jul 2008 18 Jul 2008

13 Jul 2008

-20

-10

0

10 12 14 16-20

-10

0 -20

-10

0

12 14 16 18-20

-10

0

-20

-10

0

8 10 12 14-20

-10

0 -20

-10

0

8 10 12 14-20

-10

0

Anchor station time series of oxygen and salinity

Upwelling/

Neap tide

Upwelling/

Spring tide

Greater

vertical

extent

Time of day

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AS-B

AS-M

AS

AS

Longer

duration

Less

vertical

extent

Shorter

duration

-20

-10

0

0 1 2 3 4-20

-10

0

-20

-10

0

0 1 2 3 4-20

-10

0

-20

-10

0

0 1 2 3 4-20

-10

0

-20

-10

0

0 1 2 3 4-20

-10

0

-20

-10

0

0 1 2 3 4-20

-10

0

Dep

th (

m)

Distance (km)

Distance (km)

A. Cruise A – early ebb (-0.9)

B. Cruise C – Low water (0.0)

C. Cruise C – mid-flood (0.5)

D. Cruise D – late flood (0.9)

E. Cruise E – early ebb (-0.7)

B. Cruise C – Low water (0.0)

Cross-channel transects: semidiurnal tide variation

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ML04ML05

ML07

Upwelling Downwelling

Out-cropping

Steep

gradients

Myrionecta

Dissolved oxygen source, a mixotrophic ciliate

Estuarine-ocean linkage and

physical drivers

Characterization of DO levels –

biological perspective

DO observations in the CRE

2006-2008

Oxygen production

Consequences for migrating

salmon and crab

Chlorophyll0 20 40 60 80 100

-10

-8

-6

-4

-2

0

Dep

th

Salinity0 10 20 30

0

20

40

60

80

100

Chlo

rphyll

Salinity0 10 20 30

0

20

40

60

80

100

120

140

%O

xygen

7-14 psu

Dissolved oxygen source, a mixotrophic ciliate

Cummulative Northward Wind stress

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

28

29

30

31

32

33

34

y= -3.48X + 31.0r ²=0.48S

max

Cummulative Northward Wind stress

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

2

4

6

8

y= 6.48 X + 6.0r ²=0.82

O2 m

in

Smax

28 29 30 31 32 33 34

2

4

6

8

O2

min

y= -1.03X - 37.3r ²=0.52

Correlation of physical indices

Minimum O2 vrs wind stress

Maximum salinity vrs wind stress Minimum O2 vrs Max Salinity

Upwelling Relaxation Downwelling

N

Low DO

N

Bloom

Distance

(Offshore=>Estuary)

High N Low DO

Halocline

Low wind stress

Saltier

Fresher

PNW: Strong ocean-estuary linkage modulated by upwelling dynamics

Wind from North Wind from South

Dep

th DO DO?

Estuaries “sample” nearshore water sources

Upwelling can deliver high salinity & low DO to estuaries

During relaxation, ocean productivity transferred to estuaries

Downwelling (surface) typically has lower salinity and higher DO

Low DO prevalent during summer upwelling season

N

Low DO

Definitions

Columbia River measurements

Consequences for migrating

salmon and crab

Summary and management

implications

Consequences for salmon and crabs: Spring tides

EBB

Low DO

Consequences for salmon and crabs: Spring tides

Fish: Vertical displacement

Crabs: Horizontal displacement

Periods of vulnerability FLOOD

EBB

Low DO

Definitions

Columbia River measurements

Consequences for migrating

salmon and crab

Summary and management

implications

Consequences for salmon and crabs: Neap tides

EBB

Definitions

Columbia River measurements

Consequences for migrating

salmon and crab

Summary and management

implications

Consequences for salmon and crabs: Neap tides

Fish: Vertical displacement

Crabs: Temporal displacement FLOOD

Definitions

Columbia River measurements

Consequences for migrating

salmon and crab

Summary and management

implications

Low DO is entering the CRE and other PNW coastal estuaries

Low DO water generally has reduced pH (acidic)

Source of low DO is upwelled ocean water - River water was always normoxic (in

mainstem)

Recorded values were in the moderate biological stress range – no hypoxia (yet)

Even so, recorded values likely induced adverse behavioral and physiological

effects on salmon and crabs: Effect on CONDITION & SURVIVAL??

Based on the number of wind events each year, there could be significant impacts on biota

Predictions are for worsening future conditions

Summary

Cannot prevent – can defend

Update and maintain coastal monitoring observatories like SATURN

Minimize impact to aquaculture facilities

Time salmon releases from hatcheries with favorable DO conditions

Management implications

Thanks to my once and future CMOP collaborators Joe Needoba,

Antonio Baptista, Ben Li, Lydie Herfort, Charles Seaton,

& captains and crew of Forerunner

Cruise

ID Station

Study

length

DO category

B NC07 4.7 17.0 53.2 29.8

J NC07 8.4 0.0 0.0 100.0

K NC14 9.0 0.0 0.0 100.0

M NC14 7.6 0.0 55.3 44.7

N NC07 7.8 17.9 61.5 20.5

O SC09 7.9 100.0 0.0 0.0

P SC09 4.5 100.0 0.0 0.0

Q SC09 4.9 46.9 13.9 39.2

R NC10 7.0 11.4 15.0 73.6

Year Events DO

Category Days % Time

2006

6

0 to 2 4 1.9

>2 to 4 48 22.9

>4 to 6 100 47.6

0 to 6 152 72.4

2007

9

0 to 2 1 0.5

>2 to 4 27 12.9

>4 to 6 75 35.7

0 to 6 103 49.0

2008

11

0 to 2 8 3.8

>2 to 4 31 14.8

>4 to 6 95 45.2

0 to 6 134 63.8

Bottom exposure : Semidiurnal Tidal scale

Interannual scale (Model)

Consequences?

Longer exposures at bottom

during neap tides

Interannual variation

Hypoxic conditions rare

Biologically stressful

conditions common

0 10 20 30

120 130 140 150 160 170 180 190 200 210 220 230 240 250

Win

d s

tres

s

(N m

-2)

-0.15

-0.10

-0.05

0.00

0.05

Wat

er l

evel

(m

)

0

2L

un

ar cycle0.00

0.250.500.751.00

0 10 20 30

0

2

4

6

8

10

12

0 10 20 30

Salinity (ppt)

O2

co

nce

ntr

atio

n

(mg

L-1

)

F. 8 May J. 21 August L. 27 August N. 29 August

0 10 20 30 0 10 20 30 0 10 20 30 0 10 20 30

% O

2 satu

ration

0

20

40

60

80

100

120

G. 15 May H. 31 May I. 20 August

2007

F G H I NLJ

Physical time series and O2/salinity diagrams: 2007