Phytoplankton

Nutrients

Zooplankton

Small Algae   Diatoms

  Silica frustule, unique division   Coccolithophores

  Calcium carbonate plates   Dinoflagellates

  “two flagella”--starch plates

  Picoplankton   Includes cyanobacteria and

eukaryotic organisms

  Raphidophytes, Cryptophytes, Euglenophytes, etc.

Physical mixing processes

Nutrients Optical Properties of the Water Column

In the modern ocean carbon fixation by diatoms, dinoflagellates, and coccolithophorrids dominate the global signal.

This provides the organic carbon for metazoans and carbon flux to the ocean interior and seafloor.

PHANEROZOIC MESOZOIC CENOZOIC

Carbon. Permian Triassic Jurassic Cretaceous Tertiary

Spec

ies

dive

rsity

/abu

ndan

ce (

rela

tive

scal

e)

Dinoflagellates

Chlorophytes

Diatoms

Coccolithophorids

The dominance by the big-3 is recent

End-Permian extinction

End-Triassic extinction

Critter Genome size % used in plastid

Bacteria ~3.1*106

Cyanobacteria ~6.1* 106

Chlorophyceae ~4.6* 108 10-50%

Diatoms ~1.6* 109 2-10% Coccolithophores ~2.4* 109 2-10% Dinoflagellates ~7.4* 1010 <0.1%

Assuming an average protein has 3000 amino acids and a typical cells has 105 proteins/cell.

Glaucocystophyta

Rhodophyta (Red Algae)

Cryptophyta

Heterokontophyta (kelps, diatoms, chrysophytes)

Haptophyta (Coccolithophorrids)

Chlorophyta (Green Algae)

Chlorarachniophyta

Euglenophyta Chl c & fucoxanthin Chl c &

peridinin Chl c & Chl b

Dinophyta

EUKARYOTES: Division Chromophyta Class Bacillariophyceae (Diatoms)

  Cannot swim; Can regulate buoyancy (some can migrate)

  Require silicon; Encased in Pill-box shaped silica frustule

  Important in coastal areas and spring blooms

Looking Down on the Valve

�New

Side View

epitheca

hypotheca

pennate

centric

Images from http://www.microscopy-uk.org.uk/mag/wimsmall/diadr.html

pennate

pennate

centric

Silica frustule

EUKARYOTES (continued): Division Chromophyta Class Pyrrophyta (Dinoflagellates)   Motile; Can migrate vertically   “Red tides” and shellfish poisoning   There are autotrophic and heterotrophic species

www.jochemnet.de/fiu/phaeocystis.gif

Dinoflagellates: Some are bioluminescent

http://www.microscopy-uk.org.uk/mag/art98/nocti.html

Noctiluca Noctiluca bloom

www.redtide.whoi.edu/hab/rtphotos/rtphotos.html

Dinoflagellates

Naked Noctiluca

EUKARYOTES (continued): Division Chromophyta Class Prymnesiophyceae (Haptophyceae) Coccolithophores

  CaCO3 skeletal plates   pCO2 increases   DMS production

Emiliania huxleyi earthguide.ucsd.edu/images/eg/img/ehuxleyi.gif

EUKARYOTES (continued): Division Chromophyta Class Cryptophyceae

  Motile   Contain phycobiliproteins   Can be recognized by size and fluorescence (flow cytometry)

Cryptomonas http://mac2031.fujimi.hosei.ac.jp/PDB/Images/Mastigophora/Cryptomonas/Cryptomonas.jpg www.unex.es/botanica/ clases.htm

Other Small Organisms

  1977--Hobbie discovers the importance of bacteria, using Acridine Orange

  1981--Chisholm and Olson discover picoplankton:   Cyanobacteria (or blue-green algae)   Prochlorococcus

  Late 1990s--Delong and others recognize importance of archaea

  2000-02--Small organisms dominate?

PROKARYOTES (continued): Synechococcus

  Discovered in 1979   very small (ca. 1 µm)   contains phycoerythrin   can fluoresce orange or red   counted with epifluorescence

microscopy or flow cytometry

reprinted from Johnson and Sieburth 1979 http://www.woodrow.org/teachers/esi/1999/ princeton/projects/cyanopigs/data.htm

  Discovered in 1988   Very small (<1.0 µm)   Divinyl chl a   Counted by flow

cytometry   Most abundant

autotroph on earth

PROKARYOTES (continued): Prochlorococcus

reprinted from Johnson and Sieburth 1979

PROKARYOTES (continued): Trichodesmium(Oscillatoria thiebautii)

  Forms aggregates   Fixes nitrogen   Can migrate vertically   May transport phosphate

from depth to near surface   New production transports

more C

http://www.botan.su.se/fysiologi/Cyano/Tricho.jpg www.aims.gov.au/pages/research/ trichodesmium/tricho-01.html

Trichodesmium bloom

Phytoplankton

• Photosynthesis can be described using PvsE curves

• Nutrient uptake can be described using Michaelis-Menten curves

• When the cells are healthy, they are in balanced growth and have Redfield proportions of elements

• There’s a general relationship between size and number for everything in the ocean (including phytoplankton)

• Large cells can use “luxury uptake”

Phytoplankton

Nutrients

PvsE curves

Michaelis-Menten curves

• Photosynthetic Quotient: we can measure productivity using several methods, and convert one to the other using the PQ

• Redfield Ratios: we can measure any nutrient and convert to any other nutrient

Who takes up nutrients the fastest?

Nutrient-uptake kinetics and ecological/evolutionary selection

Phytoplankton isolated from oligotrophic environments have lower Ks values than phytoplankton from eutrophic environments (consistent with prediction based on ecological theory)

0.0

0.5

1.0

1.5

2.0

2.5

0 2 4 6 8 10 12

Nutrient Uptake

Spe

cific

Rat

e of

Upt

ake

(d-1)

Nutrient Concentration (µM)

I

IIV

max = 2.25 d-1

Ks = 2.0 µM

Vmax

= 1.5 d-1

Ks = 0.5 µM

Nutrient kinetics for growth (rather than for uptake) are more difficult to determine: experiments involve growth in chemostat culture

Ks < 0.1 µg-at L-1

Droop Kinetics µ = µmax(1 - kq / Q)

µ = growth rate kq = minimum cell quota Q = current cell quota Qmax = max cell quota

•  If an organism has a high degree of “quota flexibility”, it can vary the ratio kq/Qmax by quite a bit--this allows for luxury uptake

•  Redfield Ratios are ONLY approximated when µ/µmax is close to 1

•  Therefore, cell composition can provide an indication of cell growth status, or limitation

Consequently, chemical composition responds to growth conditions

0.00

0.02

0.04

0.06

0.08

0.10

N:C

mol

ar ra

tio

0.12

0.0 0.2 0.4 0.6 0.8 1.0µ (d-1)

A

189 µmol m-2 s-1

63 µmol m-2 s-1

N-Limited <——> N-sufficient The chemical composition of phytoplankton is very responsive to growth conditions. Here, nitrogen content is lower when growth rate is limited by the supply of N (carbohydrates are accumulated).

Classic Bloom Dynamics

Margalef’s Mandala

Seasonal Patterns

Kudela et al., 2005, Oceanography 18: 185-197

Diatoms vs. Dinoflagellates

  Diatoms   Annual cycle   Prolonged duration   High species diversity   Clear succession pattern

  Sinking strategy   Elevated nutrients,

turbulence

  Dinoflagellates   Unpredictable   Ephemeral   Low diversity   Truncated

succession

  Swimming strategy

  Low nutrients, stratified water column

Size Scaling in the ocean

Log (size)

Log

(abu

ndan

ce)

viruses bacteria

phytoplankton zooplankton

Small fish Large fish

Whales

• There are “rules” about size and abundance— • small organisms grow faster, and are more abundant • You need large phytoplankton to get high biomass, to feed fish, etc.

Large Cells = High Biomass

From Chisholm, 1992

Summary • Large cells do better in high nutrient environments because they can store excess nutrients

• Small cells do better in low nutrient environments because they have a high surface/volume ratio, generally grow faster, and require less of everything

• There are low macronutrients in much of the surface ocean

• large scale patterns of low biomass & small cells in the open ocean are driven by fast growth and large loss terms—diatoms and dinoflagellates exist at the “edges”, competing for higher nutrients, & show up when nutrients increase (e.g. upwelling)

• High biomass means large cells—leads to higher trophic transfer (diatoms rule!)