Transcript Lec #6 - University of San Diego Home Pages

Tree of Life
Planktonic Organisms
• Planktonic organisms are at the mercy of the
prevailing water movements
• Are essential components of the oceanic
ecosystem
• Are normally caught in nets of various mesh sizes
and are therefore often classified by size
Planktonic Organisms
• Holoplankton
• Meroplankton
Planktonic Subdivisions
Phytoplankton
Zooplankton
Bacteria/Archaea
Microbial World - Prokaryotes
A. Bacteria
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Prokaryotes and unicellular
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Very small cells (<0.1 µm)
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Found in all areas of the ocean
1. Heterotrophic Bacteria
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Decomposers
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Recycle nutrients
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Food for benthic organisms
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Can be symbiotic
Microbial World - Prokaryotes
A. Bacteria
2. Autotrophic Bacteria
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Chemosynthetic
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Photosynthetic
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Chlorophyll a
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Phycoerythrin and phycocyanin
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Called Cyanobacteria
Microbial World - Prokaryotes
A. Bacteria
2. Cyanobacteria
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Stromatolites
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Epiphytes
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Nitrogen fixation
Microbial World - Prokaryotes
B. Archaea
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Look like bacteria but more closely related to eukaryotes
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Decomposers
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Extremophiles
Tree of Life
Microbial World - Eukaryotes
A. Diatoms (Bacillariophyta)
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Unicellular
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May form chains
Cell enclosed by silica (SiO2) frustules (test)
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Test usually perforated and ornamented with spines or
ribs (Why?)
Perforations allow gases, nutrients, waste products to pass
through test to cell
Important open-water primary producers, especially in
temperate and polar regions
Microbial World - Eukaryotes
A. Diatoms (Bacillariophyta)
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Reproduction
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Asexual - Cell division
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Sexual - Egg + Sperm --> Auxospore
Microbial World - Eukaryotes
A. Diatoms (Bacillariophyta)
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Explosive population growth --> Bloom
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May deplete nutrients locally
Sediments beneath areas where diatoms are abundant may
contain many tests
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Diatomaceous oozes
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Diatomaceous earth
Microbial World - Eukaryotes
B. Dinoflagellates (Dinoflagellata/Pyrrophyta)
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•
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Possess two flagella
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Motile
Covered with theca made of cellulose plates
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Theca may have spines
Important open-water primary producers, especially in
tropical regions
Trophically diverse
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Autotrophic
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Heterotrophic
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Mixotrophic
May bloom like diatoms
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Red tides
Microbial World - Eukaryotes
B. Dinoflagellates (Dinoflagellata/Pyrrophyta)
Microbial World - Eukaryotes
B. Dinoflagellates (Dinoflagellata/Pyrrophyta)
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Some forms live symbiotically with corals, anemones,
jellyfish, giant clams, sponges
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Zooxanthellae
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Lose flagella
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Especially important in reef building corals
Some forms can be extremely toxic
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Pfiesteria
- Blooms triggered by coastal pollution
- Toxin can cause memory loss in humans
Microbial World - Eukaryotes
B. Dinoflagellates (Dinoflagellata/Pyrrophyta)
Microbial World - Eukaryotes
C. Other Algae
1.
2.
3.
Silicoflagellates (Chrysophyta)
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Silica test, usually with spines
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Single flagellum
Coccolithophorids (Haptophyta)
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Covered by calcium carbonate coccoliths
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Coccoliths may be important components of sediments
Cryptomonads (Cryptophyta)
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Lack skeleton
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Two flagella
Why are Phytoplankton Important?
• Fix 40 - 50 Gigatonnes C per year
• Phytoplankton make up ~1% of global plant
biomass, but are responsible for ~50% global
photosynthesis
• Are the base of the oceanic food web
• Regulate global climate
• Sink for atmospheric CO2
Light vs depth