Phytoplankton Entrainment and distribution in the Pelagic

C. Reynalds, Chapter 2Ecology of Phytoplankton

Paul Simonin

John Bisgrove

Physical Properties of Water

• Higher density• Higher viscosity• Higher melting point• Higher boiling point• Lower compressibility• Polar molecule• Aquo polymers• High specific heat

• Density is greatest at 3.98 Celsius

• Rate of density change increases as heated above

Viscosity and Turbulence

• Turbulent Intensity– Product of root mean

squares of time averaged fluctuations (u*)2

– Turbulent velocity (u*)

1

absolute viscosity

mild horizontal force

u horizontal velocity

z depth

dudz

Turbulent Dissipation

• Environmental grain– The size and velocities

decrease with transfer

-1

largest eddy size

m s

e

e

l

duu l dz

Wind

Velocities must equalor create heat

Total volumes must equal

2 3* * 1 2 -3

Rate of energy dissipation (E)

E= u u m sedu ldz

Turbulent Embedding of Phytoplankton

1Re w su d

Sinking and Floating

12 1

c

w

Stokes equation

18

sinking velocity

g gravity

d diameter

density of cell

density of water

absolute viscosity

s c w

s

w gd m s

w

Regulation of Density

• Densities of cellular components – Proteins ~1,300 kg m-3 – Carbohydrates ~1,500 kg m-3

(cellulose)– Nucleic acids ~1,700 kg m-3 – SiO2 ~2,600 kg m-3(diatom walls) – Lightest lipids ~860 kg m-3

– Average cell density is rarely less than ~1050 kg m-3

Form resistance

rs

grV

9

'2 2

Sinking and Entrainment in Natural Turbulence

• Tendency to sink or float (ws)

• Propulsion (us)

• Velocities of the water • Horizontal motion

increases distance traveled during fall

12 2/15[ ' ]sw w

Loss of Sinking Particles from Turbulent Layers

• 95% elimination te/t’=3.0

• 99% elimination te/t’=4.6

Mixing1( )( / )el u du dz

12

b w m wRi gh u

121 2

b m w m wW Ri Lh gh u L

1*

1*

0.2 time of travel in mixed layer, unconstained

2 time of travel in mixed layer, constained

m m

m m

t h u

t h u

Robustness of gradient

Resistance to mixing

Largest eddy size

Vertical Structure in the Pelagic

• diurnal time-scale

• wind time-scale

• seasonal time-scale

• compare to euphotic zone

• mixed layer

• thermocline

Spatial Distribution of Phytoplankton - Vertical

• non-motile, negatively buoyant planters

• positively buoyant plankters

• neutrally buoyant plankters

• motile plankters

( )c w

( )c w

( ~ )c w

( )su u

Spatial Distribution of Phytoplankton – Langmuir

circulation

Horizontal Spatial Distribution of Phytoplankton - Patchiness

• Sampling Issues• Ecological Reasons

– In fisheries patchiness leads to very reduced zones of high growth potential (Hobbie, 2000)

• Small scale patchiness– Langmuir circulation

• Small lake basins– Drift interrupted by

shallows, margins, islands

– Basin scale conveyer current

– Drift of buoyant organisms

– Patchiness as inverse function to wind speed

• Large scale patchiness– Horizontal mixing time– Diffusivity– Population change

Oceanic Circulation

Additional resources• General concepts: Inland waters and their ecology, by I. A. E. Bayly

and W. D. Williams; Textbook of limnology, by Gerald A. Cole; Wetzel texts…

• United States. Environmental Protection Agency. Ecological research series ; EPA-600/…

• Ecology of harmful algae, by E. Graneli, J.T. Turner (eds.)• The Algae and their life relations; fundamentals of phycology, by

Tilden, Josephine E (1935)• Local resources: ESF theses such as:The distribution and density of

phytoplankton of Jamesville Reservoir, by Pingel, Patricia A. • Estuarine Science: A Synthetic Approach to Research and Practice

Edited by John E. Hobbie, Island Press, Washington, D.C. (2000)