What Do Zooplankton Eat?

Written by Volia Nikaci
Updated: January 23, 2023
© Choksawatdikorn/Shutterstock.com
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The ocean and other bodies of water are home to a variety of life. A wide variety of marine life lurks in the deep waters of the ocean, from tons of fish to larger marine life. However, did you know that the ocean also has a vast array of life that is too tiny for the naked eye to even see? These microscopic lifeforms are known as plankton. Particularly the zooplankton. Nearly all bodies of water contain small, floating animals known as zooplankton. So how much do you know about these tiny animals? Let’s take a peek at the world of zooplankton, where there’s so much to discover. We’ll go over what zooplankton eat and so much more!

What Is Zooplankton?

What Do Plankton Eat - Microscopic View
Zooplankton are named after the Greek word planktos, meaning to drift or float. 

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Let’s begin by explaining what zooplankton is. Plankton is derived from the Greek word planktos, which means “wanderer” or “drifter.” Since plankton are too weak to swim against the current, they are carried by currents and tides. In the water, they simply drift along. Depending on the size, type, and length of time they spend drifting in the ocean, plankton can be classified in different ways. Among these microscopic organisms, two distinct categories exist. Among them are zooplankton, which acts as animals, and phytoplankton, which acts as plants.

Zooplankton are larger organisms than phytoplankton and can include many microscopic animals drifting in the water. Some of these include microscopic animals such as krill, sea snails, and more. This category can also include jellyfish. Zooplankton are divided into two major groups. They’re divided into Holoplankton, which lives all their lives in the state of being plankton, and Meroplankton, which live as plankton only in a larval or reproductive stage.

Lakes and ponds are mainly home to Cladocera and Copepods, both classified as micro-crustaceans, rotifers, and protozoans. In most lakes, there will be at least 40 different zooplankton species.

Let’s look at what zooplankton eat now that we know what they are.

What Do Zooplankton Eat?

What Do Plankton Eat - Zooplankton
Zooplankton are considered herbivores because they mostly feed on microscopic plants known as phytoplankton.

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Zooplankton primarily eat plants as part of their diet. Most of them are herbivores, meaning they feed on various plants rather than meat. In fact, phytoplankton is the main food source for zooplankton. They eat microscopic plants that live in the water but are too small to be seen by the naked eye. As a result, zooplankton plays an important part in creating the food web in the ocean.

In addition to phytoplankton, they eat bacteria and algae at the bottom of the food chain. Rarely, there may also be times when zooplankton may feed off each other to survive. It has even been concluded that zooplankton can sustain themselves on carbohydrates at times, according to studies done on their diets. When phytoplankton is absent, zooplankton may consume carbohydrates from fallen leaves and shoreline vegetation.

Having learned what zooplankton eat, let’s examine how they obtain their food.

How Does Zooplankton Get Its Food?

When the sun is shining, zooplankton tend to drift into deeper waters to avoid daytime predators. In the evenings, however, these tiny creatures venture up to the surface in an attempt to feed on phytoplankton that is visible at the surface. 

As they vary in many ways, zooplankton makes use of a variety of eating habits. As mentioned above, they may eat bacteria, algae, and other zooplankton. Sometimes they even eat parasites. Cladocera, and many zooplankton species in general, feed without discrimination. They will eat any particle they can filter from the water with their feeding appendages. Some zooplankton, like Copepods, is more particular about what they will eat. This zooplankton picks out the particles it will eat based on size, shape, and taste.

Overall, it seems that all zooplankton species are filter feeders. They do not move independently, so they must filter what they find in the water through their limbs to survive.

We now know how zooplankton finds their food, so let’s take a look at the animals that consume zooplankton and how they do it.  

What Eats Zooplankton?

Biggest Whale the Blue Whale
The blue whale has been known to eat enormous amounts of zooplankton per day.

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Since zooplankton are herbivorous creatures that cannot move on their own, for the most part, they are an important source of food for a variety of animals. A comparable food chain relationship between zooplankton and phytoplankton occurs in the outer marine environment. Zooplankton are a valuable food source for many marine animals for energy and nutrients. As the food chain grows, small predators feed on copepods and other plankton they strain from the water.

Several species of crustaceans, including shrimp and krill, and small fish, such as sardines and herring, consume large amounts of zooplankton. As the food chain grows, even more, even larger fish eat zooplankton. Blue whales, the largest animals in the world, can consume as much as 16 tons of plankton daily, for example. Similarly, Basking sharks enjoy zooplankton as a source of nutritional protein.

Now that we’ve got all this information, we have one final question. What makes zooplankton so important for the ecosystem?

Why Are Zooplankton Important To The Ecosystem?

The aquatic food chain relies heavily on zooplankton. There would be no no big ocean animals without zooplankton. It would be devastating to ocean life if there weren’t enough zooplankton around. The reason for this is that zooplankton provides food for many ocean creatures.

The zooplankton can also significantly impact water quality in their habitats. A lot of factors in the ocean ecosystem affect plankton, including temperature, salinity, pH level, and the number of nutrients present in the water. Flows of harmful algae, like red tide, can occur when water levels of certain nutrients are too high. Phytoplankton plays a major role in the food chain, so changes in phytoplankton abundance or timing can rapidly affect zooplankton populations. 


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What Do Plankton Eat - Zooplankton
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About the Author

Volia Nikaci is a freelance copywriter and content editor with a passion and expertise in content creation, branding, and marketing. She has a background in Broadcast Journalism & Political Science from CUNY Brooklyn College. When she's not writing she loves traveling, perusing used book stores, and hanging out with her other half.

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