Difference between Phytoplankton and Zooplankton

May 31, 2017 by Editorial Team

The term “plankton” is fairly common and is pretty understandable by many, even if you are not a Marine Science fanatic. (No, we are not referring to the cartoon character, by the way!) But did you know that there are two kinds of plankton, specifically phytoplankton and zooplankton? If you did not know this, you’ve come to the right place. In this article we will discuss the difference between the two groups.

Descriptions

Phytoplankton vs Zooplankton
Phytoplankton

The term phytoplankton is derived from the Greek words phyton and planktos, which mean “plant” and “drifter” respectively.

Phytoplankton, in general, are non-swimming microscopic organisms that dwell in the upper sunlit layer (the euphotic zone) of the earth’s oceans and other bodies of water. They depend on macronutrients (such as calcium, phosphate, nitrate, etc.) carbon dioxide, and sunlight. They are too tiny to be seen by the naked eye, although some kinds appear as cloudy or brown patches on the surface of the water when they are grouped in large numbers. Very similar to plants, they do not swim but float freely instead. Examples of phytoplankton include protists, cyanobacteria, dinoflagellates, chalk-coated coccolithophores, diatoms, cyanobacteria, and green algae.

Phytoplankton are photosynthesizing organisms (similar to land plants), which means they get their energy from sunlight (which is why they dwell in layers that are well-lit) and produce chlorophyll within their cells. They have the capability to transform carbon dioxide into organic compounds, such as oxygen, which is an initial step in sustaining the entire food web. Because of this, they are often called the “primary producers.” They feed different organisms like zooplankton, whales, small and big fish, and other marine invertebrates. Although they are tiny, they supply half of the earth’s oxygen supply.

The presence of phytoplankton affects the odor, color, and taste of the water. This is especially evident when there a phenomenon called “red tide” occurs. This is caused when certain types of phytoplankton produce strong biotoxins, killing marine animals and poisoning the humans who consume contaminated seafood.

zooplankton
Zooplankton

The term zooplankton comes from the Greek words zoon and planktos, which mean “animal” and “drifter,” respectively.

Zooplankton dwell in the deep sections of the earth’s bodies of water, usually where there is no sunlight, and move to the surface at night to hunt for food. They feed on phytoplankton, bacteria, detritus (marine snow), and, cannibalistically, other zooplankton. They are then eaten by small fish, making them the second link of the aquatic food chain.

Zooplankton come in different colors, shapes, sizes (some are tiny and some can grow up to 8 feet). In general, the term “zooplankton” covers “holoplankton,” which are those that stay planktonic forever, and “meroplankton,” which are those that are larval forms of bigger sea animals. Examples of zooplankton include protozoa, worms, copepods, larvae of annelids, crustaceans, and fish, and other animals such as the giant Nomura’s jellyfish and Portuguese Man o’ War.

Moreover, some kinds of zooplankton can house disease-causing bacteria, such as the Vibrio Cholerae, the bacterium that causes cholera.

Phytoplankton vs Zooplankton

What, then, is the difference between phytoplankton and zooplankton?

In general, phytoplankton is considered to be a plant form (the Greek word phyton means “plant”), whereas zooplankton is an animal form (the Greek word zoon means “animal”). Being similar to land plants, phytoplankton have the ability to go through photosynthesis and convert carbon dioxide into oxygen, They need sunlight, so they dwell in the well-lit surface layer of the earth’s waters. Zooplankton, on the other hand, dwell in the deep sections of the water, usually with little to no sunlight, because they do not go through photosynthesis.

Phytoplankton is the primary producer in the aquatic food chain. They depend on macronutrients (such as calcium, phosphate, nitrate, etc.), carbon dioxide, and sunlight. They, then, get eaten by zooplankton and other marine animals such as whales. They also supply half of the world’s oxygen. On the other hand, zooplankton are the second link of the aquatic food web. They eat phytoplankton, other zooplankton, bacteria, and marine snow. They get eaten by small fish.

Phytoplankton are usually too tiny to be seen by the naked eye unless they are in groups (they appear as brown or cloudy spots). They include protists, cyanobacteria, dinoflagellates, chalk-coated coccolithophores, diatoms, cyanobacteria, and green algae. On the other hand, zooplankton come in different colors, shapes, and sizes (from microscopic organisms to giant creatures). They include holoplankton (true planktons) and meroplankton (larval forms of larger animals), specifically worms, copepods, larvae of annelids, crustaceans, and fish, and other animals such as the giant Nomura’s jellyfish and Portuguese Man o’ War.

Both phytoplankton and zooplankton play an integral role in the aquatic food chain, but they can also be harbingers of diseases and death. “Red tide,” which can kill marine life and poison humans is caused by toxin-producing phytoplankton, while the bacterium that causes cholera (Vibrio Cholerae) may attach to certain types of zooplankton.

Comparison Chart

PhytoplanktonZooplankton
Derived from the Greek words phyton and planktos, meaning “plant drifter”; plant formComes from the Greek words zoon and planktos, meaning “animal drifter”; animal form
Microscopic; some may appear as brown or cloudy patches on the surface when they group togetherComes in different colors, shapes, and sizes
Dwell in the upper sunlit layer (the euphotic zone) of the earth’s oceans and other bodies of water.Dwell in the deep sections of Earth’s bodies of water, usually where there is no sunlight, and move to the surface at night to hunt for food
Depend on macronutrients (such as calcium, phosphate, nitrate, etc.), carbon dioxide, and sunlightFeed on phytoplankton, other zooplankton, and detritus (marine snow)
Called the “primary producers” because of their ability to transform carbon dioxide into oxygen and feed other organisms such as zooplankton and larger animalsThe second link of the aquatic food chain; cannot produce oxygen; feed larger animals such as fish and whales
Include protists, cyanobacteria, dinoflagellates, chalk-coated coccolithophores, diatoms, cyanobacteria, and green algaeInclude “holoplankton” and “meroplankton”; examples of zooplankton are protozoa, worms, copepods, larvae of annelids, crustaceans, and fish, and other animals such as the giant Nomura’s jellyfish and Portuguese Man o’ War
May produce strong biotoxins causing the phenomenon called “red tide”; can kill marine animals and poison the humans who consume contaminated seafoodCan house disease-causing bacteria, such as Vibrio Cholerae, the bacterium that causes cholera