The Ocean as a Microbial Habitat Matthew Church Marine 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). H2SH2S Glucose

Nutrient sources Nitrogen: protein, nucleic acids –NO 3 -, NO 2 -, N 2, NH 3, organic N Phosphorus: nucleic acids, lipids –PO 4 3-, organic P Carbon: nucleic acids, protein, lipids, carbohydrates, etc. –CO 2, organic C Sulfur: amino acids, protein, lipids –SO 4 2-, S, H 2 S, organic S

Light, Salinity, Nutrients, Temperature, Pressure Spatial gradients in the marine environment

Time-space scales of physical processes B P Z F From T. Dickey Scales of variability are important Note 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 Classification MinimumOptimumMaximum Psychrophile<010-15>20 Psychrotroph015-20>25 Mesophile <45 Thermophile >100 Most organisms in the oceans are psychrophiles and mesophiles Oceans

Divisions per day Temperature ( o C) 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 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.

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