Phytoplankton and Primary Production (www.microbiological garden) Marine habitats High tide Supralitoral Low tide Pelagic zone Litoral Sublitoral neritic Bathyal oceanic Epipelagic Mesopelagic Bathypelagic Benthic habitats Abyssal Abyssopelagic Hadal pelagic Hadal (Lalli & Parsons 1995)
Communities of the marine pelagic zone Plankton: Nekton: Benthos: Neuston: Organisms buoyant and passively drifting in the water, unable to actively move against the water currents. - Virioplankton - Bacterioplankton - Mycoplankton - Phytoplankton - Protozooplankton / Metazooplankton Actively moving and migrating organisms Organisms living in benthic habitats. Viriobenthos, Bacteriobenthos, Mycobenthos, Phytobenthos, Zoobenthos. Organisms living at the air-sea interface. Producers Consumers Decomposers Plankton size classes Size (m) Body weight Size (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 H 2 O + 6 CO 2 C 6 H 12 O 6 + 6 O 2 Light reaction (absorption by light-harvesting pigments and chlorophyll a) H 2 O + NADP + + Pi + ADP ½O 2 + NADPH + H + + ATP Dark reaction (Calvin-Benzon Cycle) CO 2 + NADPH + H + + ATP CH 2 O + 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 I c I i : I (µe m -2 s -1 ) Irradiance Controlled by: light reaction dark reaction α: slope Ic: light saturation Ii: 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 Michaelis-Menten Kinetics: V = V max x [S] / (K s + [S]) Concentration 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-limitation N : 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)
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 Asterionellopsis glacialis Chaetoceros convolutus 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. singlecellswithtwoflagellaorcolonies(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: Dinoflagellates: Polar-, subpolar regions, temperate zone and upwelling regions. 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)