Planktons are freshwater or marine organisms that currents and tides carry since they are too weak or too small to swim against these forces. The term ‘plankton’ originates from the Greek for ‘wanderer’ or ‘drifter.’ It shows that these organisms typically drift for their entire lifetime. However, some only drift when they are young and are classified as plankton during this period, but they grow large enough to swing against tides and currents with time.

While most planktons are microscopic, less than an inch in length, you can find larger ones. There are two common ways to classify these organisms. These are zooplankton (animals) and phytoplankton (plants).

This article delves deeper into this subject to help you understand the significance of plankton to the environment. It shall pay close attention to issues like these organisms’ appearance, diet, habitat, reproduction, and threats.


Considering the information above, plankton refers to a diverse collection of plants and animals. So, the term doesn’t refer to any single organism.  

Some great examples of plankton are:

  • Protozoa
  • Algae
  • Bacteria
  • Archaea
  • Fish eggs
  • Crab larvae
Assorted plankton
Assorted plankton

Copepods are the most common zooplankton.

Copepods, the most common and easily recognized zooplankton
Copepods, the most common and easily recognized zooplankton

Most planktons are less than one inch long, but scientists consider large floating seaweeds like Sargassum and many related multicellular algae as plankton. It is distinguished from nekton, strong swimming animals, and benthos, which refers to plenty of burrowing organisms on the seafloor.

In short, we can refer to any animal or plant too weak or too small to swim as plankton.


Phytoplankton makes their food through photosynthesis. These plant-like living things contain the green coloring matter found in plants and use it to convert sunlight into energy. Once this process is over, they combine water and carbon dioxide to create a form of simple sugar known as glucose.

Phytoplankton store glucose as carbohydrates, which they rely on for survival.

Note that phytoplankton also depends on nutrients they find in their surroundings, such as calcium and phosphate.

The next category of plankton, zooplankton, also feeds to survive and reproduce. However, unlike their counterparts that manufacture their food, these animal-like organisms prey on other planktonic creatures.


Planktons are available in large numbers in saltwater and freshwater. That’s why most people refer to them as freshwater and marine drifting organisms.

However, there is enough evidence that some plankton also spends part of their lives drifting in the atmosphere. Examples of plankton that do this are plant spores, pollens, and lightweight seeds.

How can you know whether a body of water or the atmosphere has a large plankton population? Consider its clarity. According to the National Geographic Society, there’s usually less plankton in clear water than in brownish or greenish water.

Phytoplankton blooms in the Barents Sea. The solid white area is cloud cover
Phytoplankton blooms in the Barents Sea. The solid white area is cloud cover

You can apply this same test to the atmosphere if you want to know whether the air you breathe has large quantities of plankton.


Many planktonic organisms reproduce sexually. Some use specialized appendages to prevent their partners from drifting away during copulation.

Studies have also shown that some planktonic organisms release sperm into the water column near their female counterparts. Once that’s done, the females take up the sperm, and the reproduction process moves on to the next step.

That’s not all, though. 

Some of these organisms release eggs and sperm simultaneously to increase the probability of fertilization. Chemical, environmental, and environmental cues often trigger this simultaneous reaction.

What about asexual reproduction? This is highly possible but isn’t common in these invertebrates.


Like many animals, the rising sea temperature and climate change pose a great risk to plankton. Experts have also pointed out that plastic pollution is killing them in large numbers every day.

Since plankton is the primary food source in the sea, they are highly valuable for the ocean ecosystem. Crustaceans, whales, and fish are some sea creatures that thrive by feeding on them. Zooplanktons also depend on phytoplankton for food.

While plankton isn’t endangered currently, a combination of the factors presented in this section could lead to their extinction in the future.

Facts About Plankton

  1. Planktons are the primary source of food in the ocean ecosystem.
  2. Phytoplanktons manufacture their food through photosynthesis.
  3. Besides energy from photosynthesis, phytoplanktons depend on nutrients available in the ocean, like nitrite, calcium, and phosphate, to thrive.
  4. Most sea animals eat zooplankton, and large marine animals like whales also eat the plankton-eaters.
  5. Blue whales can eat approximately 12,000 pounds of krill in a single feeding session.
  6. Climate change, global warming, and pollution pose a serious threat to the survival of these animal-like and plant-like organisms.
  7. Plankton doesn’t swim independently— tides and currents carry them and determine where they go.


What does plankton need to survive?

Plankton needs sunlight, water, and carbon dioxide to survive. Phytoplankton, the primary food source in the ocean ecosystem, use chlorophyll to make their food. They are typically buoyant and float on water to access all these essentials. Zooplankton feeds on these plant-like materials. It’s important to add that plankton also needs a population-free environment to survive. Without this, their life remains at risk even if they can make food well.

Is plankton harmful to the environment in any way?

Yes, too much plankton at sea can seriously threaten the environment. Which one? Plankton is essential for food chains but can lower water quality or air we breathe. Note that too much concentration of these organisms often turns the color of the water from crystal-clear to brown or green. Besides, if the plankton population increases uncontrollably, some of them can release harmful toxins and contaminate the marine environment.

Can phytoplankton live on land or in the atmosphere?

Yes, phytoplankton can live on land or in the atmosphere in some circumstances. They typically get energy through photosynthesis and should spend most of their time in places where this process can occur without interruptions. That’s why they are mainly found in the well-light surface layer of a lake, sea, ocean, or other water bodies. However, plankton can also survive on land or in the air for limited periods.

Does plankton live in warm or cold water?

Plankton lives in both warm and cold water. However, the water temperature has a strong influence on their growth rate. You’ll find more phytoplankton in warmer equatorial waters than in cold regions. That means they can grow in cold water but only do well in warmer waters.

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