Marine Microbiology: Meet the Microbes of the Sea!

"Microbes" is another name for microorganism. They are tiny living things. They’re too small for you to see with just your eyes. But even if you can’t see them, they’re there! They live in every type of environment you can imagine! They live in rainforests, in the Arctic, in deserts and at the bottom of the ocean. 

The ocean is a marine environment. And a single drop of seawater can contain millions of marine microbes. These tiny living things help supply oxygen and food to other organisms that live in the ocean. They even help keep the ocean clean.

What are the different types of marine microbes?

There are many types of marine microbes. Maybe you’ve heard of bacteria, which you can also find on land. Most bacteria are single-celled organisms. That means their bodies are made up of only one cell. In the ocean, bacteria support many chemical processes.

Phytoplankton are another group of marine microbes. These microscopic creatures can create their own food. Most of the time, they do this through photosynthesis. That means phytoplankton convert sunlight and carbon dioxide from the ocean into oxygen and sugars. 

Have you heard of marine plants called algae? They are a common type of phytoplankton.

Did you know? 

Only some of the oxygen you breathe comes from plants and trees on land. Every second breath you take comes from the billions of phytoplankton living in the ocean! 

Other types of microbes also live in the ocean. For example, there are fungi and viruses. There are also archaea and protists. They are single-celled organisms that look like bacteria. 

Did you know?

Microscopic animals called rotifers live in brackish environments. That’s where freshwater and saltwater mix. Unlike other microbes, rotifers have more than one cell!  

How do ocean food chains work?

A food chain describes the relationship between organisms that eat other organisms. Plants are the base of land food chains. For example, cows eat grass and then some people eat cows. 

Phytoplankton are the base of ocean food chains. You already learned that algae are a type of phytoplankton. They get their energy from the sun. On the next level of the food chain, zooplankton eat phytoplankton. 

Zooplankton include krill and the larvae of crabs and fish. These tiny critters drift along with the ocean currents. They can’t create their own food using photosynthesis.

Bigger animals, like fish and whales, eat zooplankton. And zooplankton eat phytoplankton. So without phytoplankton, there would be no life in the oceans!

What do marine bacteria do? 

Cyanobacteria are a common type of marine bacteria. They are also a type of phytoplankton. That means they produce their own food. But they use nitrogen instead of carbon dioxide! 

Cyanobacteria are an important part of the nitrogen cycle. They convert nitrogen to a form that other marine organisms can use. Marine bacteria also help clean up the ocean. Some help break down dead marine animals. Others can even help break down oil after an oil spill!

Some marine bacteria are bioluminescent. And some of them live in symbiotic relationships with other marine organisms. Often, the relationship is mutualistic. That means both organisms benefit. 

You may have seen pictures of scary looking fish called anglerfish that hunt their prey using lights. Those “lights” are actually bioluminescent bacteria! The bacteria help the fish catch food. And the fish give the bacteria a place to live! 

Unfortunately, not all marine bacteria are helpful. Some of them can hurt other marine organisms or even cause disease. For example, Vibrio cholerae is the bacteria responsible for the disease cholera. And as ocean temperatures rise, these types of harmful bacteria are spreading faster. 

How do scientists study marine microbes?

It’s not easy for scientists to study marine microbes. Only 1% of marine bacteria can be grown in a laboratory. So scientists have to study them in the ocean. And their tiny size also makes this very hard.

Scientists sometimes collect microbes using plankton nets. These cone-shaped nets have a very fine mesh. A container at one end of the net collects the samples.

Remote sensing is another way to study marine microbes. For example, scientists use satellites to study algal blooms from space. 

In 2018, scientists made a breakthrough in the field of metagenomics. They can now use DNA samples from ocean bacteria to study new types of marine microbes.

Going to the beach this summer? Remember that the water is full of creatures too tiny to see. But don’t be scared! Those critters help support all forms of life beneath the waves. And by producing the oxygen you breathe, they help you survive, too!