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What Do Plankton Eat [Dietary habits of Plankton]

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Plankton, the microscopic organisms that drift through the aquatic realms, play a crucial role in the marine ecosystem. 

Even though they’re small, they’re crucial for the ocean’s well-being. They form the base of the ocean food chain, making sure everyone else gets their meals. 

What’s interesting is that different kinds of plankton have their unique diets, and we’ll talk more about that in this article.

We’ll also discuss how these super tiny organisms get their food and learn about the dangers they face from predators. 

But before we get into all that, let’s first get to know the various types of plankton.

Different Types of Plankton

Different Plankton
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Plankton is not a single group, it’s a diverse collection of microscopic life! Mainly there are two main types of Plankton :

1. Phytoplankton

Firstly, there’s Phytoplankton – these are small, plant-like organisms floating in the water, creating their food through photosynthesis.

They form the foundation of the marine food web and are responsible for about half of the world’s oxygen production. 

Some familiar faces among phytoplankton are diatoms, dinoflagellates, and cyanobacteria.

2. Zooplankton

On the flip side, we have Zooplankton – these are animal-like plankton that feed on other planktonic organisms or organic particles. 

Essentially, they are tiny animals drifting in the water, munching on phytoplankton. Larger creatures like fish and whales, in turn, feast on zooplankton. 

Some well-known types of zooplankton include copepods, krill, and protozoans.

Yet there is also another type of plankton which is  Bacterioplankton! These are the bacteria living in the water, doing important work breaking down organic matter and recycling nutrients. They are another crucial element in the complex realm of plankton. 

Now that you know the different kinds of Plankton, let’s explore what they eat all year round.

What Do Plankton Eat Throughout The Year?

1. Phytoplankton

Phytoplankton, those minuscule oceanic plants, have a preference for sunlight, carbon dioxide, and water.

They’re smart because they use a process called photosynthesis, just like how plants on land make their food. Further insight into this process will be provided later.

To stay healthy and reproduce, these tiny plants absorb important nutrients like nitrate, phosphate, and iron from sources such as bacteria, dead organisms, or deep ocean currents. 

Although they eat the same things all year, the changing seasons affect how much of these nutrients they can get.

This change impacts how many of these plants grow and live in the ocean.

2. Zooplankton

Zooplankton mostly eat phytoplankton, which are tiny ocean plants. They can eat other small creatures by either filtering them from the water or actively hunting them. 

Some eat specific kinds of algae, and their numbers might change when there’s a lot of this algae around. 

Depending on the time of year and where they are, zooplankton might also eat bacteria, dead stuff, or even other zooplankton. 

They’re like tiny underwater hunters, and what they eat can change with the seasons and where they live.

In lakes and rivers, plankton might eat different things than in the ocean because the water has different nutrients and tiny creatures. 

If the water gets warmer or colder, it can affect how much plant-like plankton (phytoplankton) and animal-like plankton (zooplankton) grow and move, which can change what they eat. 

Even though plankton usually eat the same types of food, their menu can change a lot throughout the year, showing how they adapt to the seasons and the place they live.

The Photosynthesis Process of Phytoplankton

Photosynthesis Process of Phytoplankton
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Phytoplankton, these remarkable organisms, have a unique way of making their food through a fundamental biological process called photosynthesis.  

1. Sunlight as the Energy Source

Phytoplankton are dependent on sunlight as their primary source of energy. Through a process known as photosynthesis, they capture sunlight using pigments such as chlorophyll, found within their cells. 

This captured sunlight serves as the driving force for the subsequent chemical reactions that enable the conversion of raw materials into energy-rich organic compounds.

2. Carbon Dioxide Absorption

Apart from capturing sunlight, phytoplankton also take in carbon dioxide from the water around them. 

This dissolved gas in seawater is essential for creating organic matter.

During photosynthesis, phytoplankton uses the carbon atoms from carbon dioxide to construct intricate organic compounds, leading to the production of glucose and oxygen.

3. Nutrient Utilization

Phytoplankton also depend on nutrients, such as nitrogen, phosphorus, and trace elements, which they acquire from the water. 

These nutrients act as essential building blocks for the creation of proteins, nucleic acids, and other vital cellular components. 

The availability of these nutrients influences the growth and productivity of phytoplankton populations.

As a result of this process, phytoplankton releases oxygen into the water, adding to the total amount of oxygen in the nearby environment. 

Overall, phytoplankton are important because they turn sunlight into energy for the ocean, helping all kinds of life thrive in the sea.

But being plankton comes with its difficulties, and these tiny beings have to deal with dangers from different predators hiding in the water.

In the next part, we’ll talk about the creatures that eat plankton:

Predators of Plankton

Tiny plankton are important in the ocean, even though they’re small. They have to deal with predators like small fish and big whales. 

These predators actively hunt plankton to eat them up. Small fish, which are always hungry, help keep the number of plankton in check by eating them and searching for them. 

Jellyfish, with their see-through bodies and stinging tentacles, are good at catching and stopping plankton, making the ocean a lively place. 

Larger zooplankton, like copepods and krill, have complicated relationships in their group, affecting how many of them there are and how they stick together. 

Special whales, like the blue whale, eat in a unique way called filter-feeding. They use baleen plates to catch plankton while letting water flow out. 

All these interactions among plankton predators, from small fish to jellyfish, larger zooplankton, and amazing baleen whales, decide how many plankton there are and where they are found.

This affects the overall health and changes in the ocean’s food web.


Understanding what plankton eat and how they obtain their food provides valuable insights into their significance in the ocean. 

Despite their small size, these tiny creatures play a crucial role in maintaining the health of the ocean. Feel free to comment below if you have any questions. Thank you for reading!


Can plankton eat grass?

No, plankton can’t eat grass. Plankton are tiny, mostly microscopic organisms found in water, and they have specific diets.
Some plankton, like phytoplankton, are plant-like and use sunlight to make their food through photosynthesis.
They can’t consume grass or other complex plant materials.

Does plankton eat fungi?

No, plankton generally don’t eat fungi. Plankton have diverse diets, and some types, like zooplankton, may consume other tiny organisms or particles in the water.
However, the consumption of fungi is not a typical part of their diet.
Plankton play crucial roles in marine ecosystems, but their feeding habits are more aligned with other small aquatic organisms.

Can humans eat plankton?

Yes, humans can eat plankton, but it’s not a common practice. Plankton are incredibly small, and harvesting them on a large scale would be challenging.
Some marine animals, like certain species of fish and whales, consume plankton, indirectly making it a part of the human diet when we eat seafood.
However, there are also dietary supplements available that contain extracts from certain types of plankton, which some people choose to consume for their potential health benefits.

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