Marine Ecology I: Phytoplankton
and Primary production
Osvaldo Ulloa
University of Concepcion, Chile
[email protected]
From SOLAS Science Plan
International Summer School, Cargèse, 2005; Marine Ecology I
Phytoplankton, biogeochemistry and
climate I
• Uptake (through photosynthesis) of CO2
International Summer School, Cargèse, 2005; Marine Ecology I
Phytoplankton, biogeochemistry and
climate II
• Production of dimethyl sulphide (DMS)
• Calcification
Ca+2 + CO32-
CaCO3
– Can affect the infrared radiative properties of the
atmosphere
International Summer School, Cargèse, 2005; Marine Ecology I
– Source of cloud condensation nuclei, which
change the reflectance (albedo) of clouds
– Can affect the shortwave radiative properties of
the atmosphere
International Summer School, Cargèse, 2005; Marine Ecology I
Phytoplankton, biogeochemistry and
climate III
Biological (organic) pump
• Modulation of the absorption of shorwave
(visible) radiation in the surface ocean
Phytoplankton
– Can affect absorption and the transport of heat in
the ocean
CO2 + H2O + Nutrients + Light
International Summer School, Cargèse, 2005; Marine Ecology I
Diatoms
International Summer School, Cargèse, 2005; Marine Ecology I
Dinoflagellates
- Eukaryotes
• Eukaryotes
- Major primary producers
• Usually exist as single cells
- Commonly form chains or colonies
• Have two flagella
- Have external “skeletons” made of
silica
Organic matter + O2
i.e., they can swim weakly
• Alkenones are used for reconstruction
- Can sink fast
of paleo-temperatures
• Red tide producers
International Summer School, Cargèse, 2005; Marine Ecology I
International Summer School, Cargèse, 2005; Marine Ecology I
Coccolithophorids
Phytoflagellates
• Eukaryotes
• Have two flagella but only
• Eukaryotes
at certain life stages
• Single cells or can form large
• Spherical organisms
(up to 1 cm) hollow, gelatinous
covered with plates of
colonies
Ca+2
calcium carbonate
+
CO32-
CaCO3
• Blooms increase water albedo
• Fossils are used to make chalk
International Summer School, Cargèse, 2005; Marine Ecology I
• Producers of DMS
• Decaying remains can cause
foam on the sea shore
International Summer School, Cargèse, 2005; Marine Ecology I
Cyanobacteria I
Cyanobacteria II
Trichodesmium
Marine Synechococcus
• Exist as single filaments, trichomes
(10’-100’s of cells), or colonies
(visible to the naked eye; 1-10 mm in length)
• Nitrogen fixers (i. e., contribute to new
production)
• Have gas vacuoles
• Tropical and subtropical distribution
International Summer School, Cargèse, 2005; Marine Ecology I
• Small unicellular prokaryotes (ca. 1 µm)
• Contain phycobilisomes
• Orange-yellow fluorescence under blue light
• Some motile strains
• Global distribution, throughout euphotic zone
• Up to 104 -105 cells mL-1
International Summer School, Cargèse, 2005; Marine Ecology I
Flow cytometry
Cyanobacteria III
Prochlorococcus
• Small unicellular prokaryotes
• Size: 0.5 a 0.7 µm in diameter
• Main photosynthetic pigments are
divinyl chlorophyll a (Chl a2) and divinyl
chlorophyll b (Chl b2)
• Most abundant phytoplankton (40°N-40° S)
• Genomic size ca. 2 Mbp. Smallest of all
known oxyphotobacteria
Discovered in the 80’s (Chisholm et al., Nature 344: 340, 1988).
International Summer School, Cargèse, 2005; Marine Ecology I
Genetic library of 18S rRNA genes
PICOEUKARYOTES
(< 2 - 3 m)
• Ubiquous and significant members
Figure by Glen Tarran
Chlorophyll-a: an index of phytoplankton biomass, B
• Main photosynthetic pigment
• Present in all -and only in- phytoplankton
of the plankton
• Phylogentically very diverse
• New clades very different from
known organisms
Dimensions: M L-3
Units: mg m-3 ( µg L-1)
• Phototrophic: 103-104 cells mL-1
• Heterotrophic: 102-103 cells mL-1
Sample from Equatorial Pacific
(depth of 75 m)
Moon-van der Staay et al., Nature 409: 607, 2001
Methods: Colorimetric
Fluorometric (in vivo, on extracts)
High Performance Liquid Chromatography (HPLC)
Remote sensing
• Photosynthetic
International Summer School, Cargèse, 2005; Marine Ecology I
International Summer School, Cargèse, 2005; Marine Ecology I
Phytoplankton absorption spectrum
mg Chl-a m-3
International Summer School, Cargèse, 2005; Marine Ecology I
International Summer School, Cargèse, 2005; Marine Ecology Ib
Primary production, P
*CO
Light
2
+ H2O
Organic* matter + O2
Rate of photosynthesis (carbon fixation) per unit volume
per unit time
Dimensions: M L-3 T-1
Units: mg C m-3 h-1
Daily water-column primary production:
PT,Z = P(z,t) dz dt
International Summer School, Cargèse, 2005; Marine Ecology I
International Summer School, Cargèse, 2005; Marine Ecology I
Which are the factors controlling primary production?
External
Internal
• Light
• Nutrients (macro & micro)
• Grazing
• Temperature
• ...
• Pigments
• Nutrient pool
• Enzyme concentration
• Cell size
• ...
• Most of the variability in the photosynthetic rate of phytoplankton can
be attributed to variations in light
• After light, most of the variability in primary production measurements
can be explained in terms of variability in biomass
International Summer School, Cargèse, 2005; Marine Ecology I
Photosynthesis-light curve
One useful approach
a) To establish a quantitative description of the relationship
between biomass-normalised primary production and light
b) To study the effect of other variables (e.g., nutrients, T°,
cell size, etc.) on the photosynthetic parameters
P(I) = PB(I) * B
PB = Biomass-normalised primary production
I = Irradiance (Photosynthetically Active Radiation 400–700 nm)
B = Biomass
International Summer School, Cargèse, 2005; Marine Ecology I
Photosynthetic parameters
PBm = Assimilation number
Information about the dark reaction of photosynthesis
i. e., enzymatic reactions
B = Initial slope
B= a* PB = ƒ (I; B, PmB) + RB
International Summer School, Cargèse, 2005; Marine Ecology I
a* = Specific absorption coefficient
= Quantum yield (mol C / mol quanta)
Related to the efficiency of photosynthesis. Information
about the photochemical reaction
International Summer School, Cargèse, 2005; Marine Ecology I
Wavelength dependence of photosynthesis
at low light intensities
International Summer School, Cargèse, 2005; Marine Ecology I
Wavelength composition of light changes with depth
International Summer School, Cargèse, 2005; Marine Ecology I