Phytoplankton and Primary Production
(www.microbiological garden)
Marine habitats
High tide
Supralitoral
Low tide
Pelagic zone
neritic
oceanic
Litoral
Epipelagic
Mesopelagic
Sublitoral
Bathyal
Bathypelagic
Benthic
habitats
Abyssal
Abyssopelagic
pelagic Hadal
Hadal
(Lalli & Parsons 1995)
Communities of the marine pelagic zone
Plankton:
Organisms buoyant and passively drifting in the water, unable to actively
move against the water currents.
- Virioplankton
- Bacterioplankton
- Mycoplankton
- Phytoplankton
- Protozooplankton / Metazooplankton
Nekton:
Actively moving and migrating organisms
Benthos:
Organisms living in benthic habitats.
Viriobenthos, Bacteriobenthos, Mycobenthos, Phytobenthos, Zoobenthos.
Neuston:
Organisms living at the air-sea interface.
Producers
Consumers
Decomposers
Plankton size classes
Size (m)
Size
Body weight
(Sieburth 1978)
Primary Production – light as a resource
De novo synthesis of organic matter
from inorganic constituents
by autotrophic organisms.
If the energy source is light: photoautotrophic
6 H2O + 6 CO2
→
C6H12O6 + 6 O2
Light reaction (absorption by light-harvesting pigments and chlorophyll a)
H2O + NADP+ + Pi + ADP
→
½ O 2 + NADPH + H+ + ATP
Dark reaction (Calvin-Benzon Cycle)
CO2 + NADPH + H+ + ATP
→
CH2O + NADP+ + ADP + Pi
Light harvesting pigments
of phytoplankton
(http://www.uic.edu/classes/bios/bios100/lecturesf04am/absorption-spectrum.jpg)
Light harvesting pigments
of phytoplankton
(Lalli & Parsons 1995)
Primary Production
Controlling factors of primary production:
· Light (ressource and environmental factor!)
photosynthetic active radiation (PAR): 400 – 700 nm
· Temperature
· Hydrography, Stratification
· Nutrients
Primary Production – Light (P vs I curve)
Photosynthetic rate
mg C (mg Chl x l x h)-1
Pmax
α
Controlled by:
α:
Ic:
Ii:
light reaction
Ic
Ii:
I (µE m-2 s-1)
Irradiance
dark reaction
slope
light saturation
light inhibition
Light adaptation of phytoplankton groups
low light-adapted
high light-adapted
Vertical attenuation of light in the water column
• Exponential attenuation with depth
(absorption by pigments and dissolved
organic substances and scattering by
ions and particles)
• Attenuation is wave length-specific
• Euphotic depth:
photosynthesis = respiration
(0.1-1% of surface light intensity)
(Lalli & Parsons 1995)
Vertical zonation of light in the water
column
(Lalli & Parsons 1995)
Controlling factors for the light climate in the euphotic zone
(Lalli & Parsons 1995)
Temperature as controlling factor
• Direct control of primary production of minor importance.
Light reaction of photosynthesis little controlled by temperature.
• Indirect control by hydrographic conditions
(blooms only develop when euphotic depth exceeds
critical depth)
Temperature as controlling factor
Sverdrup's Model of Critical Depth
• Photosynthesis decreases exponentially with
depth due to decrease in light availability.
• Respiration is unaffected by light and
remains constant with depth.
• Phytoplankton is mixed by turbulence and
experiences different light intensities over
time, sometimes above and sometimes below
compensation point.
• Critical depth = depth at which photosynthesis
of the total water column phytoplankton
population equals their total respiration.
A phytoplankton population can only
proliferate if mixing is shallower than
the critical depth.
Only then is the population net production >0
(Lalli & Parsons 1995)
Nutrients
• Macro-Nutrients: C, N, P, Si, S, K, Ca, Mg.
• Micro-Nutrients:
Fe, Zn, Mb, Cl-
• Vitamins
Available form of macro-nutrients (C, N, P, Si, S)?
Nutrient uptake
Uptake rate
Concentration
Michaelis-Menten Kinetics:
V = Vmax x [S] / (Ks + [S])
Nutrient requirements and limitation
• Phytoplankton biomass - C : N : P = 106 : 16 : 1
(Redfield-ratio)
• In most cases N or P are limiting (sometimes Fe).
N : P > 16 Æ P-limitation
N : P < 16 Æ N-limitation
Nitrate : phosphate ratio in the eastern tropical Pacific
(Fiedler et al. 1991)
Nitrate : phosphate ratio
in the eastern Mediterranean Sea
(Krom et al. 1991)
Nitrogen and phosphorus
in the open and coastal North Sea 1980-2002
Coastal North Sea: PPR P-limited
open North Sea: PPR N-limited
(McQuatters et al. 2007)
HNLC-regions
(High Nutrient Low Chlorophyll)
Fe limits primary production.
Dugdale & Wilkerson 1991
Annual vertical pattern of
primary production and nutrients
(Lalli & Parsons 1995)
Saisonal pattern of primary production in
various climatic regions
(Lalli & Parsons 1995)
Phytoplankton
(Lalli & Parsons 1995)
Cyanobacteria
• prokaryotes
• appr. 150 genera and >2000 species
• single cells or colonies
• pigments: chlorophyll a (and b)
phycocyanin, phycoerythrin
• asexual cell division
• most important marine genera:
• Syneccococcus (single cell)
• Prochlorococcus (single cell, chlorophyll a+b)
• Crocosphaera (N2-fixation)
• Trichodesmium (colonies, bundles, N2-fixation)
• Nodularia (colonies, N2-fixation, Baltic Sea)
• Richelia intracellularis (colony, diatom symbiont, N2-fixation)
Phylogenetic tree of cyanobacterial DNA polymerase I protein sequences
showing genetic diversity among Prochlorococcus and Synechococcus
strains compared with gene conservation in Crocosphaera strains
high light adapted
low light adapted
Zehr J P et al. PNAS 2007;104:17807-17812
©2007 by National Academy of Sciences
Phylogenetic tree of Synechococcus and
Prochlorococcus (16S rRNA gene)
Low light
High light
Low light
(West et al., Microbiology 147: 1731, 2001)
Trichodesmium
Satellite image of a Trichodesmium surface bloom
Richelia intracellularis in a diatom cell
(Bar Zeev et al., ISME J 2: 911, 2008)
Cyanobacteria
• important components of the phytoplankton in oligotrophic
subtropical and tropical oceans.
• constitute populations at the lower end of the euphotic zone
(deep chlorophyll maximum) in stratified seas.
• important sources of new nitrogen in N-limited regions
(oligotrophic subtropical and tropical oceans).
This source has been seriously underestimated in the past.
Diatoms
• 250 genera with appr. 100.000 species.
• chloroplasts with chlorophyll a and fucoxanthin.
• single cells or colony-forming, silicate frustule with
epy- and hypotheca.
• suborders Biddulphiales (Centrales) and Bacillariales
(Pennales).
• asexual reproduction usual, but sexual reproduction
and formation of auxospores possible.
Diatoms
Diatoms
(Sommer 2005)
(Lalli & Parsons 1995)
Diatoms
Corethron sp
Chaetoceros convolutus
Asterionellopsis glacialis
Chaetoceros debilis
Annual production of particulate biogenic silikate
(Bishop 1989)
Diatoms
• a dominant phytoplankton component in nutrient-rich
marine regions (temperate, subpolar, upwelling).
• important component of the sinking flux.
Dinoflagellates
• 130 genera with appr. 2000 species.
• single cells with two flagella, one embedded in the sulcus
as part of the cingulum.
• cell surface covered with a layer of polygonal vesicles (theka).
• vesicles can be empty (naked dinoflagellates) or filled
with cellulose plates.
• can be autotrophic or heterotrophic (Noctiluca scintillans).
• asexual and sexual reproduction usual, formation of resting cysts.
Dinoflagellates
Dinoflagellates
(Sommer 2005)
(Lalli & Parsons 1995)
Dinoflagellates
Ceratium horridum
C. fusus
C. tripos
C. furca
Red Tide (Noctiluca scintillans)
www.ecodivecenter.com/ecofact_otm-php?id=22)
Dinoflagellates
• important components of the phytoplankton in tropical to
temperate seas.
• can form toxic blooms (red tides).
Prymnesiophytes / Haptophytes
• 75 genera with appr. 500 species.
• single cells with two flagella or colonies (Phaeocystis).
• one important order includes the genus Phaeocystis,
forming colonies with mucus and foam as decomposition
product.
• one important order has calcified scales: Coccolithophores.
• important components of the oceanic phytoplankton globally.
Various haptophytes
(Sommer 2005)
Coccolithophores
Emiliana huxleyi
10 µm
Global distribution of Emiliana spp
Phaeocystis pouchetii
(www.microbiological garden)
Foam of Phaeocystis
Global distribution of the major phytoplankton groups
Diatoms:
Polar-, subpolar regions, temperate zone and upwelling regions.
Dinoflagellates:
Tropical, subtropical and temperate zone, in summer and fall
after disappearance of diatoms (depletion of silicate).
Coccolithophores: Tropical, subtropical, temperate and subpolar (global).
Synecchococcus: Tropical, subtropical, temperate and subpolar
(deep chlorophyll maximum).
Prochlorococcus:
Tropical and subtropical
stratified regions
(surface and deep populations)