Prsentation PowerPoint

1
The biological contribution to the
atmosphere-ocean bottom CO2 fluxes Myth or
reality?
G. Ferreyra and S. Demers
2
Strategy of the presentation

• The biological pump process
• Whats known and whats unknown
• Main of uncertainties regarding the
  functionality of the BP Environmental controls
  of the plankton community metabolic balance
• Conclusions and future venues of research

3
Strategy of the presentation

• The biological pump process
• Whats known and whats unknown
• Main of uncertainties regarding the
  functionality of the BP Environmental controls
  of the plankton community metabolic balance
• Conclusions and future venues of research

4
Sun
Herviborous food web (HFW)
CO2
Atmosphere
CO2
Phyto
Zoo
NO3 (new production)
Bact
Ocean
DOC
POC
Pycnocline - Zeu
Burial
5
Sun
Mixed food web
CO2
Atmosphere
CO2
Phyto
Zoo
NO3NH4
Bact
Ocean
DOC
POC
Pycnocline - Zeu
Burial
6
Sun
Microbial food web
CO2
Atmosphere
CO2
Phyto
Zoo
NH4 (regenerated prod.)
Bact
Ocean
DOC
POC
Pycnocline - Zeu
Burial
7
Biological component of CO2 fluxes
8
Hypothesis
9
Community type
Herbivorous food web
Mixed food web
Microbial food web
P
R
Time
Production type
New
Regenerated
Intense, A-H uncoupling
Low, A-H coupling
Carbon export
10
Strategy of the presentation

• The biological pump process
• Whats known and whats unknown
• Main of uncertainties regarding the
  functionality of the BP Environmental controls
  of the plankton community metabolic balance
• Conclusions and future venues of research

11
Some significant points

• Most of the estimations of the biological
  contribution to carbon fluxes are based on
  chlorophyll a
• Main advantage easy to measure in the field, and
  detectable by satellite imaginery
• Limitations
• State variable, not a process
• Only representative of the photosynthetic
  component of the community
• Heterotrophic contribution not considered

A central gap Few oceanographic information on
Respiration is available
12
Del Giorgio Duarte, 2002 Karl et al.,
2003 Serrett et al., 2006 Duarte, 2006
13
Strategy of the presentation

• The biological pump process
• Whats known and whats unknown
• Main of uncertainties regarding the
  functionality of the BP Environmental controls
  of the plankton community metabolic balance
• Conclusions and future venues of research

14
The UVBR problem
O3 decrease
Increased UVBR
1 - Molecular
UVR effects at the molecular and cell levels
propagate to higher levels of organization in
the ecosystem the balance between damage and
repair will control community production, and
extra energy would be needed to generate defence
mechanisms, increasing community respiration
2 - Cellular
3 - Population
3 - Population
4 - Community
15
Metabolic cost of defence mechanisms
Damage Repair
These processes may result in significant
changes in the autotrophic and heterotrophic
components of the community
In the context of global warming, UVR changes at
the community level may be more important than at
lower levels, affecting biogeochemical cycles and
carbon fluxes.
16
The DMS/DMSP problem

• Dimethylsulphide (DMS) is the most abundant form
  of volatile sulphur in the ocean
• Oxidation of DMS in the marine atmosphere
  produces sulphur aerosols, which originate cloud
  condensation nuclei (CCN)
• CCN scatter solar radiation, thereby influencing
  the radiative balance of the Earth (Simó, 2001)
• Algae are the main source of DMS in the ocean,
  notably coccolitophorides and Phaeocystis (Liss
  et al., 1993)

17

• DMS is produced by marine phytoplankton from its
  intracellular precursor, Dimethylsulphoniopropiona
  te (DMSP)
• DMSP is released during senescence, zooplankton
  grazing, and viral lysis Dacey and Wakeham,
  1986 Malin et al., 1998

18
Albedo
Solar radiation (heat, PAR, UVR)
Only 1 of the total DMS biologically produced,
which is not metabolized or photolysed, is lost
to the atmosphere, where is rapidly oxidized to
produce 90 of the oceanic CCN (Larsen, 2005,
and references therein)
Temperature Wind speed
1
Removal
DMSaq
Oceanic mixing layer
Planktonic food web
60 m
(Simó, 2001 Larsen, 2005 Toole et al., 2006)
19

• It has been hypothesized that significant changes
  in biologically mediated climate forcing may be
  expected in a scenario with increased surface
  water temperature and stratification (Larsen,
  2005)

20
Increasing temperature and freshening in the
water column
UVB
UVA
PAR
Z1UVB
Z1UVA
Pycnocline
Z1PAR
21
These changes may be the following

• Photolysis of CDOM is increased, increasing the
  transparency of the sea to UVR
• Photo-oxidation of DMS in the seawater by
  UVA/blue light is increased
• Phytoplankton are directly inhibited, reducing
  primary production reduced overall production
  of DMS/DMSP
• Near-surface bacterioplankton are inhibited,
  causing reduced mineralization, nitrogen
  fixation, and CDOM production
• Bacterioplankton activity is increased at greater
  depths (feeding on more labile photo-oxidized
  DOM), with increased metabolism there of
  DMS/DMSP. A reduction of the surface seawater DMS
  concentration would then be expected when this
  deeper water is mixed upwards
• A possible change occurs from DMSP rich species
  to DMSP poorer diatoms

These effects would lead to a reduced flux of
DMS from the ocean, resulting in decreased
aerosol, cloud cover, and cloud optical depth.
This increases the total exposure of the surface
to UVA, UVB and blue light, with positive
feedbacks on all of the above.
22
The acidification problem

• UVBR penetration in the water column is mainly
  controlled by absorbance and scattering by living
  and non-livng, particles, as well as by CDOM
  (Kirk, 1994).
• As CDOM is highly reactive in the UVBR band,
  these wavelengths may be able to penetrate deeper
  due to photobleaching following solar exposure.
• Anthropogenic carbon emissions could
  significantly reduce the pH of the ocean by 0.7
  units in the next 200 years, leading to an
  acidification higher than that from the past 300
  million years (Caldeira and Wickett, 2003 see
  also Cicerone et al., 2004)
• Increased acidity of the seawater will increase
  CDOM degradation (Schindler et al., 1996).
• Lower pH values in the water column will also
  modify carbonate chemistry and significantly
  affect the life cycle of calcareous organisms
  like coccolitophoriids, which are a dominant
  group in extended oceanic areas, as well as the
  main producers of carbonate on the Earth (Hays et
  al., 2005)

23
Three key topics emerge then from the previous
information as significant controls of the BP
activity

• UVR effects on the biological pump ? Pc Rc
  ratio and carbon export
• UVR effects on biologically mediated climate
  controls ? DMS-DMSP
• Increasing acidity in the water column

Few data available
24
Putting the pieces of the puzzle together
UVR
Temperature
Sea surface
UVR
Temperature
CDOM
BP
Pycnocline
Nutrients
Export
25
Putting the pieces of the puzzle together
UVR
Temperature
Sea surface
UVR
Temperature
CDOM
BP
Pycnocline
Nutrients
Export
26
Putting the pieces of the puzzle together
UVR
Temperature
Sea surface
UVR
Temperature
CDOM
BP
Pycnocline
Nutrients
Export
27
Putting the pieces of the puzzle together
UVR
Temperature
Sea surface
UVR
Temperature
CDOM
BP
Pycnocline
Nutrients
Export
28
Strategy of the presentation

• The biological pump process
• Whats known and whats unknown
• Main of uncertainties regarding the
  functionality of the BP Environmental controls
  of the plankton community metabolic balance
• Conclusions and future venues of research

29

• The biological contribution to atmosphere-ocean
  CO2 fluxes is poorly known
• Until now only the photosynthetic organisms were
  considered as the only biological variable
  influencing such a process
• The heterotrophic component of the plankton
  community should be included in models, as well
  as respiration. Consequently, the biological
  contribution to CO2 fluxes should be viewed as a
  more complex process than before
• The BP activity can be controlled by multiple
  global change related processes, which can play a
  significant role in the long-term

30

• Within the above framework, the Instituto
  Antártico Argentino and the Institute des
  sciences de la mer de Rimouski (Canada) are
  developing a joint IPY project entitled
  "Combined effects of Ultraviolet B Radiation,
  increased CO2 and Climate Warming on the
  Biological Pump A temporal and latitudinal
  study, with financial support of DNA and the
  National Science and Engineering Research Conseil
  of Canada
• The project is based on three field missions in
  the Antarctic and the Arctic, the first one
  presently ongoing on board the canadian vesel
  Sedna IV in the area of the Melchior Archipel
  with the support of DNA and the Argentinean Navy
• A second mission is foreseen for the austral
  winter 2007 on board the Argentinean icebreaker
  A.R.A. Almte. Irizar, and another one for the
  austral summer 2007-2008 (December-January) on
  board the Argentinean oceanographic vessel A.R.A.
  Pto. Deseado. This last mission includes an
  experimental study (mesocosms) in a coastal
  Antarctic Station (Esperanza)
• A second mesocosms experiment will be performed
  in the Arctic Whapmagoostui-Kuujjuarapik station
  on April 2008.

31
Many thanks
32
Removal
Sea surface
VENTILATION
DMSP
60 m
(Simó, 2001 Larsen, 2005 Toole et al., 2006)
33
Putting the pieces of the puzzle together
UVR
Temperature
Sea surface
UVR
Temperature
CDOM
BP
Pycnocline
Nutrients
Export