Phytoplankton Notes
Photosynthesis & Chlorophyll
- Chlorophyll: Green pigment that powers photosynthesis by absorbing light.
- Speed: Light reactions complete in milliseconds; full cycle in fractions of a minute.
- Importance: Produces oxygen and fuels aquatic food webs.
Phytoplankton Basics
- Microscopic, unicellular organisms that photosynthesize.
- Live for weeks to months depending on conditions.
- Over 1.5 billion years old; major groups emerged in the Mesozoic Era (251–65 million years ago).
- Key types: Diatoms, Dinoflagellates, Coccolithophores.
Plankton Size Categories
| Type |
Size Range |
Notes |
| Pico-plankton |
< 2 µm |
Tiny cyanobacteria |
| Nano-plankton |
2–20 µm |
Small flagellates |
| Micro-plankton |
20–200 µm |
Diatoms and larger algae |
Silica & Diatom Shells
- Ocean receives ~8.3 teramoles of silicon/year from beaches.
- Diatoms use silicic acid to build silica shells (frustules).
- Shells formed in silica deposition vesicles (SDVs).
- Contribute to marine sediment and carbon cycling.
Bioluminescence
- Produced via luciferin-luciferase chemical reaction.
- Found in bacteria, dinoflagellates, jellyfish, squid, deep-sea fish.
- Functions: defense, communication, hunting, camouflage.
Blooms & Human Impact
- Fertilizer and sewage runoff cause nutrient overload.
- Triggers rapid phytoplankton growth (algal blooms).
- Some blooms are toxic (harmful algal blooms).
Plankton Life Cycles
- Holoplankton: Entire life as plankton (e.g., diatoms).
- Meroplankton: Temporary planktonic stage (e.g., fish larvae).
Note: Phytoplankton are not true plants, but they perform photosynthesis and are vital to ocean
ecosystems.