Summary
Drifting organisms: phytoplankton photosynthesise and zooplankton feed on them, forming the base of marine food webs.
In depth
Phytoplankton include diatoms, dinoflagellates and cyanobacteria (Prochlorococcus is the most abundant photosynthetic organism). Zooplankton include copepods, krill and larvae. Plankton form the base of food webs and drive the biological pump.
Plankton are defined by drifting, not by size. Meroplankton are temporary members such as larvae; holoplankton are permanent. Blooms follow spring warming and nutrient supply.
Remember: phytoplankton need light and nutrients, so they live near the surface.
Plankton are organisms that drift with currents, unable to swim against them. Phytoplankton (diatoms, dinoflagellates, cyanobacteria) photosynthesise and produce much of Earth's oxygen; zooplankton (copepods, krill, larvae) graze on them. Meroplankton are the larval stages of animals that later become bottom-dwellers or swimmers.
Plankton form the base of most marine food webs and drive the biological pump. Their growth depends on light, nutrients (nitrate, phosphate, iron) and grazing; spring blooms follow stratification and light increases. Prochlorococcus is the most abundant photosynthetic cell on Earth.
Example: baleen whales feed on krill, a zooplankton.
Remember: size does not define plankton, drifting does; jellyfish are plankton.
Frequently asked questions
What is Plankton?
Drifting organisms: phytoplankton photosynthesise and zooplankton feed on them, forming the base of marine food webs.
Which area of biology covers Plankton, and how advanced is it?
Plankton is one of the 54 topics in Marine & Environmental Biology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Dead Zones, Upwelling, Harmful Algal Blooms.
Can you give an example of Plankton?
Krill feed whales in Antarctic waters.
What should I learn before Plankton?
Plankton is a Beginner topic, so no earlier topic is required. Other Beginner topics in Marine & Environmental Biology that pair well with it include Oceans, Ocean Zones, Coral Reefs.
What topics are related to Plankton?
The closest topics to Plankton are Dead Zones, Upwelling, Harmful Algal Blooms, Biological Pump. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Plankton?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Plankton. To practise the whole of Marine & Environmental Biology, use the Marine & Environmental Biology quiz.
How is Plankton different from Dead Zones?
Plankton: Drifting organisms: phytoplankton photosynthesise and zooplankton feed on them, forming the base of marine food webs. Dead Zones: Oxygen-depleted ocean areas caused by nutrient runoff, fertiliser and decomposition of algal blooms. Read both side by side and note what each one explains.
How should I study Plankton step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Dead Zones and explain the difference aloud. Finally, take the Marine & Environmental Biology quiz and come back to this page for any question you miss.