The Ocean Habitat Life at the microscale Friday, February 25, 2011
The Ocean HabitatLife at the microscale
Friday, February 25, 2011
Marine Planktonic Food Web
Prokaryotes
Friday, February 25, 2011
Most Life in the Sea is Microscopic
Friday, February 25, 2011
Friday, February 25, 2011
• Fish
• Copepods
• Diatoms
• Dinoflagellates
• Nanoflagellates
• Cyanobacteria
• Prokaryotes
• Viruses
What’s in a liter of water?NONE
10
1,000
10,000
1,000,000
100,000,000
1,000,000,000
10,000,000,000
Friday, February 25, 2011
Friday, February 25, 2011
Friday, February 25, 2011
http://www.youtube.com/watch?v=zOZi9v9p1lU
Friday, February 25, 2011
Reynolds Number
Re =
u = velocity (m/s)L= length (m)v = kinematic viscosity m2/s (10-6 for water)
Dimensionless number useful for determining relative importance of inertial versus viscous forces
uLv
Friday, February 25, 2011
Laminar vs Turbulent Flow
http://video.google.com/videoplay?docid=-4535320633959087386#docid=1827702182265329855Friday, February 25, 2011
Reynolds NumberRe =
u = 1 m/sL= 2 mv = 10-6 m2/s
uLv
Re = 1 x 210-6
= 2,000,000
Human Swimming
u = 0.000150 m/sL= 0.0000002 mv =10-6 m2/s
Re = 0.000150 x 0.000000210-6
=0.00003
Bacterium Swimming
Friday, February 25, 2011
• Large whale 10m/s
• Tuna 10 m/s
• Copepod 20 cm/s
• Invert Larva 1 mm/s
• Protozoan 35 µm/s
• Bacterium 150 µm/s
Reynolds Numbers
300,000,000
30,000,000
300
0.3
0.0003
0.00003
Friday, February 25, 2011
Viscosity
http://video.google.com/videoplay?docid=-4535320633959087386#docid=-4556431258553465670
Friday, February 25, 2011
Length Scales of Variability
L = 2π(v / e)1/43Kolmogoroff Length Scale
v = kinematic viscosity of water = 10 m s e = turbulent energy dissipation = 10 to 10 W kg
(winds 5 - 15 m s )
-1-6
-8 -6 -1
-1
2
3-6 mm20-30 mmFriday, February 25, 2011
Diffusion dominates transport at the microscale
F = D dC/dz
Values for Diffusivity (m2/s)
Heat = 1.5 x 10-7
Nutrient = 1.5 x 10-9
D = L2/t so t = L2/Dif L = 1 mm
7 sec11 min
Friday, February 25, 2011
Length Scales of Variability
L = 2π(v / e)1/43
L = 2π(vD / e)1/42
Kolmogoroff Length Scale
Batchelor Scale
v = kinematic viscosity of water = 10 m s e = turbulent energy dissipation = 10 to 10 W kg
(winds 5 - 15 m s ) D = molecular diffusivity = X m s
-1-6
-8 -6 -1
-1-12
2
Friday, February 25, 2011
Length Scales of Variability
• turbulence = 6 - 20 mm
• heat = 2 - 14 mm
• salt/nutrient = 0.2 - 1 mm
Friday, February 25, 2011
Eddy Diffusivity
• Typical eddy diffusivity for horizontal diffusion (deep ocean) is 500 m2 s-1
• 6 x 10-5 m2 s-1 vertical (deep ocean)
• Compare to molecular diffusivities of 10-7 10-11
Eddy diffusivities for deep sea from Gargett (1984) J. Mar. Res. 42: 359-395
Friday, February 25, 2011
Nutrient Diffusion
• Horizontal eddy diffusion (500 m^2/s):
• Vertical eddy diffusion (6 x 10-5 m^2/s):
• Molecular diffusion (1.5 x 10-9 m^2/s):
t = L2/D
Time for nutrients to diffuse 10 meters
20 seconds
19 days
2000 years
assuming empirical estimates on the km scale
Friday, February 25, 2011
The Problem for Small Cells
• no turbulence at the micro-scale
• diffusion is very slow
• Swimming or sinking by large cells can increase the nutrient flux to the cell to some degree.
• Boundary layers make swimming less effective for smallest cells
Friday, February 25, 2011
Friday, February 25, 2011
F = D dC/dz
Friday, February 25, 2011
Marine Snow
Friday, February 25, 2011
F. Azam & R. A. Long 2001
Photo D.C. Smith
Microscale Hot Spots Exist
colonized marine snow particle
Friday, February 25, 2011
F. Azam 1998
Microscale Patchiness and Hotspots
Creates niche space contributing to microbial diversity
Friday, February 25, 2011
Friday, February 25, 2011
Bacterial Motility
• Old models based on E. coli
• about 25 µm per sec
• run and tumble
• New observations show high speed bursts (45 to 300 µm per sec), stops and, direct reversals
• Swimming does not increase flux directly, but can move the cell to a place where nutrient concentrations are higher
Friday, February 25, 2011
Paradox of the plankton (Hutchinson)
Utilization of the same resource by two species in a homogenous environment will lead to elimination of the less competitive species
G. E. Hutchinson posed the question: Why is there so much diversity among phytoplankton? Because according to ecological theory, namely the competitive exclusion principle of Gause:
The simple explanation (recognized by Hutchinson) is that the pelagic marine environment is far from
homogeneous
Friday, February 25, 2011
Friday, February 25, 2011