Climate influences on the California Currentpelagic ecosystem

Mark D. OhmanScripps Institution of Oceanography

California Current Ecosystem Long Term Ecological Research site

CCE LTER

M. KahruB.G. MitchellSIO

A coastal upwelling biome

Calif Sea LionElephant seal Blue WhaleHumpback WhaleSooty ShearwaterLaysan AlbatrossBlack Footed Albatross

TOPP Marine Mammals & Seabirds

Dan Costa, UCSC

Pacific hake migration

Saunders and McFarlane. 1997. CalCOFI Reports 38:147

responses to

Climate Forcing in the California Current

Secular Changes

Year (A.D.)

Fluxes of subtropical foraminiferaPaleo-reconstructions from S.B. Basin sediments

David B. Field et al. 2006. Science 311:63

Kasten cores (black) + box cores (colors)

X-radiograph

Long-term warming of the NE Pacific Ocean

20th-21st century trends

Year1950 1960 1970 1980 1990 2000Tem

perature anomaly (º C

)

-2

-1

0

1

2

SIO pier Tempanomalies

Lavaniegos and Ohman 2007 Progr. Ocean. 75:42-69

Salps

Year1950 1960 1970 1980 1990 2000

C B

iomass

( Log mg C

m-2

)

0.0

1.0

2.0

3.0

Salp C Biomass

Year1950 1960 1970 1980 1990 2000

Density stratification

( Δ σt 150-10 m

)

1.0

1.2

1.4

1.6

1.8

Density stratification(150 m - 10 m)

CCE average to Sta. 70

1949 1959 1969 1979 1989 1999

Year

0

10

20

30

40

50

Secchi depth (m

)

0

20

40

60

80

100N

itracline depth (m)

Secchi depth Nitracline depth

B

Aksnes and Ohman, unpubl.

Long-term changes in water column transparency

Multi-decadal Ecosystem Shifts

responses to

Climate Forcing in the California Current

Multi-decadal ecosystem shifts?

Year1950 1960 1970 1980 1990 2000

PDO Index

-2

-1

0

1

2 PDO index

Log

No.

10

m-2

1950 1960 1970 1980 1990 2000-2

-1

0

1

2

Nyctiphanes simplexanomalies

J. Gomez

Year

Decline of the California sardine in the early 1940’s:

Figure courtesy of D. Checkley & SWFSC

• 1949 → present

• Perhaps the most comprehensive biological- chemical-physical oceanographic time series in existence

Sampling pattern since 1984(today, quarterly cruises)

Partners: SIO, NMFS, Calif. DFGBasic station pattern

CalCOFI California Cooperative Oceanic Fisheries Investigations

Decline of the California sardine in the 1940’s:

Sardine figure courtesy of D. Checkley/SIO & SWFSC/NMFS

Now recognized:

a combination of

increased fishing pressure in the post-war years

together with

a change in the ocean from a warmer to a cooler state in the early 1940’s

PDO

inde

x

PDO index

responses to

Climate Forcing in the California Current

El Niño

El Niño

Kahru and Mitchell 2000

SeaWifs Ocean Color

1950 1960 1970 1980 1990 2000-2

-1

0

1

2

Nyctiphanes simplex

1950 1960 1970 1980 1990 2000-2

-1

0

1

2Euphausia pacifica

Log

No.

10

m-2

Log

No.

10

m-2

anomalies

anomalies

Reciprocal krill variations

Brinton, Townsend, Ohman (unpubl)

El Niño’s

Butler 1989

El Niño effects on growth rate of juvenile N. anchovy

Engraulis mordax

- strong El Niño year

Salps

Year1950 1960 1970 1980 1990 2000

C B

iomass

( Log mg C

m-2

)

0.0

1.0

2.0

3.0

Log

No.

10

m-2

1950 1960 1970 1980 1990 2000-2

-1

0

1

2

Nyctiphanes simplexanomalies

1950 1960 1970 1980 1990 2000-2

-1

0

1

2Euphausia pacifica

Log

No.

10

m-2

anomalies

Secular trend

Pacific DecadalOscillation

El Niño

Year

Summary

• The California Current pelagic ecosystem is influenced by very large-scale changes in the ocean and atmosphere

• Food web effects of a warming trend, multi-decadal shifts, and El Niño have already been documented (esp. from the CalCOFI region)

• It is vitally important to build and sustain measurement programs that document biological changes in ocean ecosystems, and not to rely on surrogate measures of physical ocean variables alone

fin

Do biological systems “track” physical systems in a linear

manner, or do biological systems show characteristic

variations that cannot be predicted from ocean physics

alone?

Linear vs. Nonlinear Responses

Time

Mag

nitu

de

Time

Mag

nitu

deLinear

Nonlinear

Forcing

Response

Forcing Response

Nonlinear: commonly exhibit thresholds

courtesy of Peter Franks

Time scale Physical variable Best θ Δ r Nonlinear? N p-valueweekly Scripps Pier SST 0 0 NO 4226 1monthly Scripps Pier SST 0 0 NO 984 1monthly Pacific Grove SST 0 0 NO 945 1monthly Farallones SST 0 0 NO 764 1monthly PDO 0 0 NO 1248 1monthly NPI 0 0 NO 1260 1monthly SOI 0 0 NO 852 1quarterly Scripps Pier SST 0 0 NO 328 1quarterly PDO 0 0 NO 416 1quarterly NPI 0 0 NO 420 1quarterly SOI 0 0 NO 284 1annual Scripps Pier SST, composite 0 0 NO 984 1annual PDO, composite 0 0 NO 1248 1annual NPI, composite 0 0 NO 1260 1annual SOI, composite 0 0 NO 852 1

θ = nonlinear tuning parameter, Δ r = improvement in forecast skill (nonlinear - global linear model)

Physical time series from the North Pacific

Chih-hao Hsieh et al. (2005) Nature 435: 336

S-map method

Exhibit characteristics of linear red noise

Time scale Biological variable Best θ Δ r Nonlinear? N p-valueweekly Scripps Pier diatoms 0.3 0.139 * YES 830 < 0.01monthly Scripps Pier diatoms 0.05 0.083 YES 206 0.134quarterly CalCOFI coastal larval fish 1.6 0.031 * YES 3220 < 0.01quarterly CalCOFI coastal-oceanic larval fish 0.6 0.017 YES 1400 0.164quarterly CalCOFI oceanic larval fish 1.4 0.020 * YES 4760 0.04biannual CalCOFI copepods 1.2 0.027 YES 1736 0.078annual CalCOFI copepods 0.4 0.015 YES 868 0.322annual CalCOFI coastal larval fish 0.6 0.060 * YES 805 0.038annual CalCOFI coastal-oceanic larval fish 0.2 0.092 YES 350 0.063annual CalCOFI oceanic larval fish 0.6 0.017 YES 1190 0.273annual Chinook 0.4 0.44 * YES 63 < 0.01annual Coho 0.3 0.117 YES 63 0.212annual Chum 0.175 0.767 * YES 63 < 0.01annual Steelhead 0.2 0.272 YES 63 0.118annual Sockeye 0.7 0.168 YES 63 0.168annual Composite salmon and trout 0.3 0.078 YES 315 0.148

θ = nonlinear tuning parameter, Δ r = improvement in forecast skill (nonlinear - global linear model)

Biological time series from the North Pacific ⇒ Expect nonlinear biological responses to linear environmental forcing

Chih-hao Hsieh et al. (2005) Nature 435: 336

Year

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Coastw

ise Landings (M

etric Tons)S

ardine

0

200000

400000

600000

800000

Anc

hovy

0

50000

100000

150000

200000

SardineAnchovy

• Experimental Process Cruises

CCE LTER Program Elements

- Focusing on altered stratification and nutrient supply

- Exploiting spatial differences as an analog oftemporal change

Stratified, deep nitracline Deep mixed layer Low vertical velocities Picoplankton dominated Microbial food web

Well mixed, shallow nitracline Shallow mixed layer Strong upwelling (coastal boundaryor wind stress curl) Microplankton dominated Metazoan food web

1950 1960 1970 1980 1990 2000

Temperature

anomaly (

oC)

-2

-1

0

1

2

Secular trend

Climate forcing in the CCS

SIO Pier Temp.

El Niño

PDO Index (N. Mantua)

Year1950 1960 1970 1980 1990 2000

PDO

Index

-3-2-10123

Pacific DecadalOscillation

Collier & Palenik (2003)

Changing phytoplankton biomass and community structure in relation to nitracline depth

Nitracline Depth vs. Time

0

20

40

60

80

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004Year

Nitr

aclin

e Dep

th (m

)CCE-average

from CalCOFI data

(Goericke, unpub.)

Spatial differences in nitracline depth : CCE site

http://ccelter.sio.ucsd.edu Scripps Institution of Oceanography/U.C.S.D.

CCE LTER Station Plan

CCE LTER Station Plan

Line 80

Line 90

California coast

La Jolla

Russ Davis, Mark Ohman, and Dan Rudnicksupported by Gordon and Betty Moore Foundation

Spray ocean gliders

Spray

Log mg C

m-2

Limacina spp.

1950 1960 1970 1980 1990 20000.0

0.6

1.2 anomaly

1950 1960 1970 1980 1990 2000-0.5

0.0

0.5

1.0

Clio spp.

1950 1960 1970 1980 1990 20000.00

0.15

0.30 anomaly

1950 1960 1970 1980 1990 2000-0.15

0.00

0.15

0.30

Corolla spectabilis

1950 1960 1970 1980 1990 20000.0

0.5

1.0

Desmopterus sp.

1950 1960 1970 1980 1990 20000.00

0.03

0.06

Clione limacina

1950 1960 1970 1980 1990 20000.0

0.3

0.6

anomaly

1950 1960 1970 1980 1990 2000-0.4

0.0

0.4

0.8

anomaly

1950 1960 1970 1980 1990 2000-0.03

0.00

0.03

0.06

anomaly

1950 1960 1970 1980 1990 2000-0.3

0.0

0.3

0.6

d

e

f

g

Pteropods(from CalCOFI samples)

YearOhman and Lavaniegos (unpubl)

Anomaly

1950 1960 1970 1980 1990 2000-1

0

1

2FORAMIN.

1950 1960 1970 1980 1990 20000

1

2

3

Foraminifera(from CalCOFI samples)

Ohman and Lavaniegos (unpubl)

Year

Baumgartner et al. 1992Dominant periodicity of 60-70 yr

for both species (low pass filtered, < 150 yr)

300 2000

Historical variations in epipelagic fish populations (fish scales from varved sediments of Santa Barbara Basin)

1000 1500500

Rebstock 2001

El Niño-related perturbationsto copepod community structure

El Niños(S. California region)

Multidecadal Variation

Ohman and Venrick 2003Lavaniegos and Ohman 2003Brinton and Townsend 2003

euphausiid

doliolid

salps

Average velocity, 0-400 m Sigma-θ

Chl a fluorescence

eddy

Acoustic Backscatter

@ 750 kHz

Pre

ssur

e (d

b)

Russ Davis and Mark OhmanSIO

Glider-based observations in the California Current

Distance (km)

Oct.-Nov. 2005

front

front

Why focus on this part of the California Current System?

• Large dynamic range of ocean conditions, from highproductivity to highly stratified, oligotrophic

• 59 years of CalCOFI observations (1949 → )

• most of epipelagic fish biomass in the CCS spawns in this region

• Paleoclimate connection in the Santa Barbara Basin

Brinton 1981, Haury et al. 1986

• A Biogeographic Boundary Region

Transported by ocean currents

Lifespan closely coupled to physical forcing

Unicellular algae; rapid growth rates

• exploited species

Δ unexploited species

Chih-hao Hsieh et al. 2006 Nature 443:859

Fishing effects on population variability and extinction risk > 55 years of ichthyoplankton observations from CalCOFI

destabilizing effect of fishery-induced truncation ofpopulation age structure

Harvesting