Download Marine Ecology II - Surface Ocean

Marine Ecology II:
Bacterioplankton, Respiration and
other microbial processes
Osvaldo Ulloa
University of Concepcion, Chile
[email protected]
From SOLAS Science Plan
International Summer School, Cargèse, 2005; Marine Ecology II
International Summer School, Cargèse, 2005; Marine Ecology II
Size and relationship among the general groups
of pelagic organisms
Microorganisms
200 m
Metazoa
Macroplankton
20 m
• Are the essential catalyst for all of the geochemical
reactions within the biogeochemical cycles
• Great metabolic diversity
Microplankton
2 m
Flagelletes
Mixotrophs
Algae
Cianobacterias
Bacteria
+
Archaea
Picoplankton
• <1% have been isolated in cultures
Protists
Nanoplankton
SIZE
• Account for 98% of oceanic biomass
ZOOPLANKTON
0.2 m
BACTERIOPLANKTON
Autotrophs
CARBON METABOLISM
CELULAR STRUCTURE
PHYTOPLANKTON
mm
EUCARYOTES PROCARYOTES
• Were the only form of life for the first 2-3 billion years of
planetary and biological evolution
Heterotrophs
International Summer School, Cargèse, 2005; Marine Ecology II
International Summer School, Cargèse, 2005; Marine Ecology I
Bacterioplankton, biogeochemistry and
climate I
• Release of CO2 through respiration
• Release of N2O through nitrification and
denitrification
• Release of CH4 through methanogenesis
– Can affect the infrared radiative properties of the
atmosphere
International Summer School, Cargèse, 2005; Marine Ecology II
• Very small in size
• Lack of distinctive taxonomic
• Phylogenetically and metabolically
very diverse
• Very abundant 106 - 108 cells mL-1
DNA Fluorescence
characters in the field
characters in the field
• Metabolism of dimethyl sulphide (DMS)
– Source of cloud condensation nuclei, which
change the reflectance (albedo) of clouds
– Can affect the shortwave radiative properties of
the atmosphere
International Summer School, Cargèse, 2005; Marine Ecology II
The “universal” tree of life (rARN)
Bacterioplankton
• Lack of distinctive functional
Bacterioplankton, biogeochemistry and
climate II
Relative Size
International Summer School, Cargèse, 2005; Marine Ecology II
Aerobic Respiration (O2 as oxidant)
Biological (organic) pump
CH2O + O2
CO2 + H2O
_G0 = -402 kJ mol-1 of CH2O (for acetate)
• CH2O = organic matter (Simplification!!!)
Heterotrophic Bacterioplankton
Organic matter + O2
-
CO2 + H2O + Nutrients
International Summer School, Cargèse, 2005; Marine Ecology II
Other oxidants of organic matter
Energy Yield
• Nitrate ion
• Manganese IV oxides
• Iron III oxides
• Sulfate ion
(dissolved)
(solids)
(solids)
(dissolved)
• Models: usually the equation does not include all reactions
or even all organisms
• Many intermediates and other reactions within an organism
International Summer School, Cargèse, 2005; Marine Ecology II
Nitrate Reduction (NO3- as oxidant)
5CH2O + 4NO3-
CO2 + 3H2O
+ 2N2 + 4HCO3-
High
_G0 = -359 kJ mol-1 of CH2O
Low
NO3
NO2
NO
N2O
N2
All used microbially
• Important in Oxygen Minimum Zones and in sediments
International Summer School, Cargèse, 2005; Marine Ecology II
International Summer School, Cargèse, 2005; Marine Ecology II
Oxygen Minimum Zones in the Global Ocean
(O2 < 0.5 mL/L ~ 22 µM)
Levin, L.A. American Scientist 90: 436 (2002).
Oxygen Minimum Zones
•
Constitute ~0.1% of the global ocean volume
•
In contact with ~2.3 of the ocean floor (mainly with continental shelf
and slope)
•
Contribute with 30-50% of the total nitrogen lost, commonly
attributed to denitrification (the dissimilative reduction of nitrate to N2
by heterotrophic bacteria).
•
Significant source of N2O
•
Variability in their extension has been invoked to explain past
changes in atmospheric N2O and CO2 (changes in the ocean
nitrogen inventory - carbon sequestration via the biological pump)
International Summer School, Cargèse, 2005; Marine Ecology II
International Summer School, Cargèse, 2005; Marine Ecology II
Denitrification
A three dimensional view of the OMZ in the ESP
(Anaerobic respiration of organic matter using NO3- as the
electron acceptor – dissimilative reduction of NO3- to N2)
N2
N2O
N2
N2
OMZ
Water column
NO3Ulloa & De Pol (2004).
Sediments
N2O in surface waters and dissolved O2 in the upper 500 m
along the WHP-6 transect (32.5° S)
Manganese Reduction (MnO2 as oxidant)
CH2O + 2MnO2
+ 3CO2 + H2O
2Mn2+ 4HCO3-
_G0 = -385 kJ mol-1 of CH2O
• Observed in anoxic basins and in sediments
International Summer School, Cargèse, 2005; Marine Ecology II
Fgure 11. Dissolved oxygen through the transect WHP 6.
Iron Reduction (Fe2O3 as oxidant)
CH2O + 2Fe2O3
+4H+ + 3CO2
2Fe2+ + 4HCO3- + H2O
_G0 = -241 kJ mol-1 of CH2O
• Observed in anoxic basins and in sediments
International Summer School, Cargèse, 2005; Marine Ecology II
Sulfate Reduction (SO42- as oxidant)
2CH2O + SO42-
2HCO3- + H2S
_G0 = -43.8 kJ mol-1 of CH2O
• Important in anoxic basins (e.g., Black Sea,Cariaco Basin, some fjords, etc.)
and in sediments
International Summer School, Cargèse, 2005; Marine Ecology II
Biogeochemical cycling in
anoxic basins
Fermentation
2CH2O
CO2 + CH4
_G0 = -19.9 kJ mol-1 of CH2O
• Organic matter itself can serve as both oxidant and reductant
(disproportionation reaction)
International Summer School, Cargèse, 2005; Marine Ecology II
International Summer School, Cargèse, 2005; Marine Ecology II
Results of reductive processes in sediments
International Summer School, Cargèse, 2005; Marine Ecology II
International Summer School, Cargèse, 2005; Marine Ecology II
Other important microbial processes:
Other important microbial processes:
Anammox
Nitrification
anaerobic ammonium oxidation
NOB
AOB
Ammonium oxidation
N2O
NH4+
Nitrite oxidation
N2O
NH2OH
NO2-
N2O
NO2-
NO3-
O2
O2
Ammonium
monooxigenase
NH4+ + NO2-
Hidroxilamine
oxidase
Nitrite
oxidase
International Summer School, Cargèse, 2005; Marine Ecology II
Microbial Loop
Nutrients
+
CO2
Remineralization
Nutrients
+
CO2
International Summer School, Cargèse, 2005; Marine Ecology II
N2 + 2H2O
•
Discovered in wastewater treatment reactors
(Muelder et al. 1995).
•
Anammox bacteria belong to the bacterial division
of planctomycetes and have specific ladderane
membrane lipids.
•
Found in anoxic waters off Costa Rica (Dalsgaard
et al. 2003) and in the Black Sea (Kuypers et al.
2003).
•
Found in suboxic waters over the shelf off
Namibia (Kuypers et al. 2005).