Download - The Ocean as a Microbial Habitat Matthew Church Marine Microplankton Ecology OCN 626/Fall 2008
The Ocean as a Microbial Habitat
Matthew ChurchMarine Microplankton Ecology
OCN 626/Fall 2008
The Ocean as a Habitat
• Energy, nutrients, and life
• Description of the physical, chemical, and biological environment
• What does life require?– Energy– Nutrients (carbon, nitrogen, phosphorus, oxygen,
sulfur, etc., etc.)– Electron donor-a source of reductant– Electron acceptor- required for respiration
• Common habitat controls microorganism distributions and abundance– Light– Nutrients– Temperature– Pressure– Redox environment
Energy flows, matter cycles
Sources of energy for life in the sea
• Light-aside from hydrothermal vents, sunlight is the ultimate energy source for life in the sea (phototrophy).
• Chemical-both organic and inorganic compounds (chemotrophy).
H2S Glucose
Nutrient sources
• Nitrogen: protein, nucleic acids– NO3
-, NO2-, N2, NH3, organic N
• Phosphorus: nucleic acids, lipids– PO4
3-, organic P
• Carbon: nucleic acids, protein, lipids, carbohydrates, etc.– CO2, organic C
• Sulfur: amino acids, protein, lipids– SO4
2-, S, H2S, organic S
• Light, Salinity, Nutrients, Temperature, Pressure
Spatial gradients in the marine environment
Time-space scales of physical processes
B
P
ZF
From T. Dickey
Scales of variability are importantNote that increasing time scales generally
correspond to increasing space
scales
•Generation time of a tree:
years
•Generation time of
microbe:minutes to
days
Temperature-salinity plot from Station ALOHA showing the time-dependent changes in physical ocean properties. Note greater variability in physical
environment in upper 200 m; deep sea (>1000 m) largely invariant with time.
NOAA-NESDIS-National Oceanographic Data Center
~30X variation in temperature in the surface ocean
~4X variation in temperature in the deep sea
Sea Surface Temperature Chl a (°C) (mg m-3)
The ocean is stirred more than mixed
Yoder, 1994
Spatial discontinuities at various scales (basin, mesoscale, microscale) in the ocean habitat play an important role in controlling the growth of microorganisms.
Shelford’s Law of Tolerances:The distribution and abundance of an
organism will be controlled by that environmental factor for which the species has
the narrowest range of tolerance.
Oceans
Organisms have evolved specific tolerances to habitat variables (light, temperature, nutrients,
pH, oxygen, salinity)Group
ClassificationMinimum Optimum Maximum
Psychrophile <0 10-15 >20
Psychrotroph 0 15-20 >25
Mesophile 10-15 30-40 <45
Thermophile 45 50-85 >100
Most organisms in the oceans are psychrophiles and mesophiles
Oceans
Div
isio
ns p
er d
ay
Temperature (oC)
Temperature plays an important role in
controlling plankton growth and distributions. In this example, diatoms
have a wider range of optimal temperatures
than flagellated phytoplankton.
Which group of plankton would be predicted to
have a more cosmopolitan distribution?
Light transmission through the atmosphere and ocean
Visible
UV
Infrared
Energy impinging on the Earth’s surface is most
intense in visible portion of the spectrum
Profile of irradiance with depth
Data from Station ALOHA
Downwelling irradiance (W cm-2 nm-1)
0 20 40 60 80 100
De
pth
(m
)
0
20
40
60
80
100
120
140
160
412 nm510 nm 665 nm
Downwelling irradiance (W cm-2 nm-1)
0.1 1 10 100 1000
De
pth
(m
)
0
20
40
60
80
100
120
140
160
412 nm510 nm 665 nm
In the blue-green regions of the visible spectrum, sunlight penetrates deep into the ocean
Differences in growth as a
function of light energy by
4 isolates of Prochlorococcus
Vertical Profiles of Nutrients
Nutrient distributions with depth (pressure) at Station ALOHA
NOAA-NESDIS-National Oceanographic Data Center
Nutrient availability is governed by physics: mixing, upwelling, advection, diffusion AND biology: the balance between assimilation and remineralization
7 years of ocean chlorophyll from satellites
Mean
Maximum
Minimum
High latitudes are highly variable, central
gyres more stable
Spatially coherent interannual variability in selected ecosystems (equator for example) but most ocean
ecosystems appear highly variable in space and time
Biological variability in space and time
The mesopelagic zone is an important
region of decomposition.
Photosynthetically derived material
produced in the well-lit upper ocean sinks
to the ocean’s interior-microbes in the mesopelagic rely
on this sinking material for energy.
NO3- + NO2
- (mol L-1)
0 10 20 30 40 50
De
pth
(m
)0
1000
2000
3000
4000
PacificAtlantic
Basin scale differences in
nutrient concentrations
controlled by biology (decomposition) and
physics (thermohaline
circulation)
The bathypelagic
Barophilic (or piezophilic) microorganisms
• Barophilic microorganisms grow optimally at pressures in excess of 1 atm.
• Low temperatures and high pressures both solidify lipids (cell membranes).
• Microorganisms can adapt to changes in pressure by increasing or decreasing the fluidity of cell membranes through changes in fatty acid composition (through production of unsaturated fatty acids)
Yayanos et al. (1981) PNAS
Interactive influences of pressure and temperature on the growth of a bacterium isolated from Mariana Trench