Phytoplankton and Primary Production
(www.microbiological garden)
Marine habitats
Pelagic zone
oceanic
SupralitoralHigh tide
Low tide
Litoral
Sublitoral
Abyssal
Hadal
Bathyal
Benthichabitats
Epipelagic
Mesopelagic
Bathypelagic
Abyssopelagic
pelagic Hadal
neritic
(Lalli & Parsons 1995)
Communities of the marine pelagic zone
Plankton: Organisms buoyant and passively drifting in the water, unable to activelymove 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
(Sieburth 1978)
Size (m)
Body weightSize
Primary Production – light as a resource
De novo synthesis of organic matter from inorganic constituentsby 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 O2 + NADPH + H+ + ATP
Dark reaction (Calvin-Benzon Cycle)
CO2 + NADPH + H+ + ATP → CH2O + NADP+ + ADP + Pi
Light harvesting pigmentsof phytoplankton
(http://www.uic.edu/classes/bios/bios100/lecturesf04am/absorption-spectrum.jpg)
Light harvesting pigmentsof 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 ratemg C (mg Chl x l x h)-1
Pmax
α Ic Ii: I (µE m-2 s-1)Irradiance
α: slopeIc: light saturationIi: light inhibition
Controlled by: light reaction dark reaction
Light adaptation of phytoplankton groups
low light-adapted high light-adapted
Vertical attenuation of light in the water column
(Lalli & Parsons 1995)
• Exponential attenuation with depth(absorption by pigments and dissolvedorganic substances and scattering byions and particles)
• Attenuation is wave length-specific
• Euphotic depth: photosynthesis = respiration(0.1-1% of surface light intensity)
Vertical zonation of light in the watercolumn
(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 exceedscritical depth)
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 overtime, sometimes above and sometimes belowcompensation point.
• Critical depth = depth at which photosynthesisof the total water column phytoplanktonpopulation equals their total respiration.
Temperature as controlling factor
A phytoplankton population can onlyproliferate if mixing is shallower thanthe 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
Concentration
Uptake rate
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 � P-limitationN : P < 16 � 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)
(McQuatters et al. 2007)
Nitrogen and phosphorusin the open and coastal North Sea 1980-2002
Coastal North Sea: PPR P-limitedopen North Sea: PPR N-limited
HNLC-regions(High Nutrient Low Chlorophyll)
Dugdale & Wilkerson 1991Fe limits primary production.
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
Zehr J P et al. PNAS 2007;104:17807-17812
©2007 by National Academy of Sciences
low light adaptedhigh light adapted
Phylogenetic tree of Synechococcus and Prochlorococcus (16S rRNA gene)
(West et al., Microbiology 147: 1731, 2001)
Low light
High light
Low light
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 oligotrophicsubtropical 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 withepy- and hypotheca.
• suborders Biddulphiales (Centrales) and Bacillariales(Pennales).
• asexual reproduction usual, but sexual reproductionand formation of auxospores possible.
Diatoms
(Lalli & Parsons 1995)(Sommer 2005)
Diatoms
Diatoms
Corethron spAsterionellopsis glacialis
Chaetoceros convolutus Chaetoceros debilis
Annual production of particulate biogenic silikate
(Bishop 1989)
Diatoms
• a dominant phytoplankton component in nutrient-richmarine 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 sulcusas part of the cingulum.
• cell surface covered with a layer of polygonal vesicles (theka).
• vesicles can be empty (naked dinoflagellates) or filledwith cellulose plates.
• can be autotrophic or heterotrophic (Noctiluca scintillans).
• asexual and sexual reproduction usual, formation of resting cysts.
Dinoflagellates
Dinoflagellates
(Lalli & Parsons 1995)(Sommer 2005)
Dinoflagellates
Ceratium horridum
C. fusus
C. furcaC. tripos
Red Tide (Noctiluca scintillans)
www.ecodivecenter.com/ecofact_otm-php?id=22)
Dinoflagellates
• important components of the phytoplankton in tropical totemperate 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 decompositionproduct.
• 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 fallafter 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 subtropicalstratified regions(surface and deep populations)