Tullio Rossi Jonathan Jones Anna James Jan Taucher Shalin Seebah Graduate Students, past and present, working on OA in my lab:

Julia Sweet

Ocean Acidification, Warming and the Biological Carbon Pump

Uta Passow MSI, UC Santa Barbara

Caitlin Fairfield

Collaborators: Mark Brzezinski, Craig Carlson, Ed Laws

Lab Assistants:

S2-9895 11:40 Th. 26Mar Diam. 6-7

pCO2

today

370

Year 2100

~750 µatm

irradiance

pH ~8.1 ~7.8

mixing

Some direct and indirect changed to the abiotic environment of the surface ocean:

- ocean acidification

- light climate - nutrient availability & stoichiometry

nutrient input

Global Change

- temperature

- stratification/ turbulence

Adapted Rost et al. 2008

- trace element availability - exoenzyme activity - saturation state of CaCO3

Introduction

- allochthonous inputs (N, Fe)

- deoxygenation, OMZ

- sea level rise

CO2

DIC POM

Allochthonous nutrient input

Surface layer Export flux

DIC nutrients

100 yrs. to surface

10 yrs. to surface

Carbon Sequestration by the Biological Pump

DIC & Nutrients

1000 yrs. to surface

~ 100 m

~ 1000 m

Euphotic zone M

esopelagic zone D

eep Ocean

& DOM

Vertical migration

Physical transport

Introduction

Passow & Carlson 2012

Sequestration flux

Gravitational settling

Species/ Population

Community

Ecosystem

Global Biochemical Cycle

Physiological Response

1 2 3 multiple

What we want to know (BCP) What we can

measure well

Models

The Problem: An Analysis of Relevant Scales Introduction

Adapted Arrigo 2007

Ambient Temp., pCO2

Future Temp., pCO2

Introduction Hypothesis on TEP, aggregation and carbon flux

TEP = Transparent Exopolymer Particles: Sticky exopolysaccharides that form the matrix of most sinking marine snow

TEP in ug Xeq. L-1

Rossi et al. in prep.

Skeletonema costatum

3000

3500

4000

4500

present future

POC in ug L-1

1000120014001600180020002200240026002800

present future

POC & TEP production as a function of pCO2 (exp. 1)

Note: Population level: Higher pCO2 • has no impact on POC • leads to increased TEP

Batch growth till nutrient limitation

Carbon Fixation

Carbon Fixation

Taucher et al. L&O 2015

POC

TEP

Temp. effect

Temp. & pCO2 effect

POC & TEP production as a function of pCO2 & temperature (exp. 3)

T. weissflogii: (CCMP 1336)

Note: Population level: Higher pCO2 • no impact on POC • increased TEP Higher temperature • increased POC • Increased TEP

Batch growth after N-limitation

POC

TEP

Temp. & pCO2 effect

Dactyliosolen fragilissimus pCO2 effect

Note: Population level: Higher pCO2 • increased POC !!! • increased TEP

Higher temperature • unchanged POC !!! • decreased TEP !!!

Batch growth after N-limitation

POC & TEP production as a function of pCO2 & temperature (exp. 3) C

arbon Fixation

Taucher et al. L&O 2015

0

500

1000

1500

Amb Fut 1 Fut 2 Amb Fut 1 Fut 2

TEP

µg G

Xeq

L-1

15⁰C

20⁰C

Aggregation

Seebah et al. PLOS ONE 2014

T. weissflogii: (CCMP1336)

TEP Production as a function of pCO2 & temperature (exp. 6)

Note: Population level: Higher pCO2:

• No consistent effect on TEP!!!

Higher temperature: • increased TEP

Why is there no consistent response pattern of POC and TEP to increased temperature and pCO2?

T. weissflogii: Dactyliosolen fragilissimus Skeletonema costatum

Three coastal diatoms, all bloom forming

1. Keeping Perspective

Single abiotic stressor experiments: A fixed change in stressor may result in three different answers

Perf

orm

ance

, e.g

. gro

wth

Environmental parameter, e.g. temperature, irradiance, pCO2

Optimum

Optimum

Lethal limit

Inhibition threshold

Growth range

Performance (Optimum, Response) Curves

Carbon Fixation

0

100

200

300

400

500

15C Amb 20C Amb 15C Fut 20C Fut

POC

per

cel

l

050

100150200250300350400450

15C Amb 20C Amb 15C Fut 20C Fut

TEP

per c

ell

2. Interactive effects of multiple stressors (exp. 2)

CO2: P < 0.001 Temp: P < 0.001 CO2*Temp: P < 0.001

CO2: P < 0.001 Temp: P < 0.001 CO2*Temp: P < 0.001

pCO2 & Temperature

0

50

100

150

200

250

300

Amb HL Amb LL Fut HL Fut LL

POC

per

cel

l

-500

50100150200250300350

Amb HL Amb LL Fut HL Fut LL

TEP

per c

ell

CO2: P < 0.05 (only POC) Light: P < 0.001 CO2*Light: P < 0.001

CO2: NS Light: P < 0.001 CO2* Light: NS

Passow & Laws subm.

T. Weissflogii (CCMP 1053) pCO2 & light C

arbon Fixation

Carbon Fixation

Future Temp., pCO2

Hypothesis on POC and TEP production C

arbon Fixation

Sin

king

vel

ocity

m/d

Tota

l Agg

rega

te A

rea

mm

2 Sinking Velocity

Aggregation

TEP in ug Xeq. L-1

1000

1500

2000

2500

3000

present future

Aggregation & sinking velocity as a function of pCO2 (& TEP)(exp. 1)

Skeletonema costatum

Rossi et al. in prep.

0100200300400500600700800900

present future 0

10

20

30

40

50

60

70

80

90

present future

0

1

2

3

4

Amb Fut 1 Fut 2 Amb Fut 1 Fut 2Tota

l Agg

rega

te V

olum

e cm

3

0

500

1000

1500

Amb Fut 1 Fut 2 Amb Fut 1 Fut 2

TEP

µg G

Xeq

L-1

15⁰C

20⁰C

20⁰C

15⁰C Aggregation

Seebah et al. PLOS ONE 2014

T. weissflogii:

Aggregation as a function of pCO2 & temperature (and TEP)(exp. 6)

Aggregation: Higher pCO2:

• decreased aggregation (independent of TEP)

Higher temperature: • decreased aggregation

(increased TEP)

0

50

100

0 5 10 15

Equivalent Spherical Diameter (ESD) mm

Sin

king

vel

ocity

m d

-1

Sinking velocity as a function of pCO2 & temperature (exp. 6)

20⁰C; more TEP

15⁰C

Seebah et al. PLOS ONE 2014

Sinking Velocity

No pCO2 effect

Aggregation

Future Temp., pCO2

Sinking Velocity Hypothesis on aggregation and sinking velocity

CO2

DIC POM

Surface layer

Carbon Sequestration by the Biological Pump

~ 100 m

~ 1000 m

Euphotic zone M

esopelagic zone D

eep Ocean

& TEP (DOM)

Conclusions

Allochthonous nutrient input

DIC & Nutrients

↑ pCO2 & ↑temperature

Summary & Conclusions Carbon Fixation

• No a priori predictions with regards to carbon partitioning (between TEP and POC and DOC) as a function of increased temperature or pCO2 currently possible. The response is a

• function of stressor in relation to response curve of that species

• function of species physiology • function of interactive effects of multiple environmental

stressors

Conclusions Aggregation & Sinking • Aggregation rate decreased at high pCO2 or high temperature • Sinking velocity decreased at high temperature (more TEP),

but no pCO2 effect per se (or maybe a high TEP effect).

BCP • Diatom aggregation section of the Biological Carbon Pump

would suggest a weakening of carbon flux under high pCO2 and high temperature conditions

Gotschalk