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various marine microorganisms as they appear under a microscope

An illustration of various marine microorganisms as they appear under a microscope (lulupme, iStockPhoto)

STEM in Context

Marine Microbiology: Meet the Microbes of the Sea!

Mira Okshevsky

Summary

The ocean is full of very small but very useful creatures called microbes. Without them, none of the sea plants or animals you’ve seen would exist!

"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!  

Microscopic rotifer
Microscopic rotifer (Bob Blaylock at English Wikipedia [CC BY-SA 3.0] via Wikimedia Commons).

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!

Comparison of terrestrial and marine food chains
Comparison of terrestrial and marine food chains (Let’s Talk Science using images by lukaves via iStockphoto and iStockphoto).

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! 

Artist’s illustration of an anglerfish
Artist’s illustration of an anglerfish (Source: spyder24 via iStockphoto).

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.

US Environmental Protection Agency staff preparing a plankton net
US Environmental Protection Agency staff preparing a plankton net (Source: USEPA Environmental Protection Agency via Wikimedia Commons).

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!

Starting Points

Connecting and Relating
  • Did you know that your body is home to trillions of microbes? How does that make you feel? Explain.
  • Would you swim in water if you discovered it had microorganisms living in it? Why/Why not?
Connecting and Relating
  • Did you know that your body is home to trillions of microbes? How does that make you feel? Explain.
  • Would you swim in water if you discovered it had microorganisms living in it? Why/Why not?
Relating Science and Technology to Society and the Environment
  • What effect would increasing the amount of phytoplankton in the oceans have on the greenhouse effect? Should scientists take steps to increase the amount of phytoplankton? Explain.
  • What impact would there be if all of the microbes in the oceans died off? Explain.
  • Should governments spend money and time on research to develop other methods to determine what microbes are present in water? Why/why not?
  • Do you think we are as concerned with issues related to the ocean as we are with those that affect land-based ecosystems? Explain.
Relating Science and Technology to Society and the Environment
  • What effect would increasing the amount of phytoplankton in the oceans have on the greenhouse effect? Should scientists take steps to increase the amount of phytoplankton? Explain.
  • What impact would there be if all of the microbes in the oceans died off? Explain.
  • Should governments spend money and time on research to develop other methods to determine what microbes are present in water? Why/why not?
  • Do you think we are as concerned with issues related to the ocean as we are with those that affect land-based ecosystems? Explain.
Exploring Concepts
  • What is a marine microorganism? Where do marine organisms live? 
  • What type of organism forms the base of the marine food chain? How does this organism get energy to live? 
  • What is the difference between zooplankton and phytoplankton?
  • What is a mutualistic relationship? Explain using examples.
Exploring Concepts
  • What is a marine microorganism? Where do marine organisms live? 
  • What type of organism forms the base of the marine food chain? How does this organism get energy to live? 
  • What is the difference between zooplankton and phytoplankton?
  • What is a mutualistic relationship? Explain using examples.
Nature of Science/Nature of Technology
  • How is the development of metagenomics a good example of how scientific knowledge and technology progress? Explain.
Nature of Science/Nature of Technology
  • How is the development of metagenomics a good example of how scientific knowledge and technology progress? Explain.
Teaching Suggestions
  • This article can be used to support teaching and learning in Biology and Environmental Science related to aquatic ecosystems, invertebrates, food chains & webs and diversity of living things. Concepts introduced include microorganisms, environment, marine, marine microorganisms, bacteria, phytoplankton, photosynthesis, brackish, food chain, zooplankton, nitrogen cycle, bioluminescent, mutualistic, algal blooms and metagenomics. 
  • Teachers could introduce this topic by engaging students with an Admit Slip learning strategy to activate their prior knowledge related to microorganisms. Ready-to-use reproducibles can be downloaded in [Google doc] and [PDF] formats.
  • Before students read the article, conduct a Vocabulary Preview learning strategy to have students identify words that may be new to them and to activate prior knowledge through the words they are familiar with. A Vocabulary Preview for this article is available for download in [Google doc] and [PDF] formats.
  • To consolidate learning, teachers could have students do a Concept Definition Web for the concept of marine microbes. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • To conclude, teachers could lead a discussion using one of the questions above to help students reflect on and consolidate the information they have learned.
Teaching Suggestions
  • This article can be used to support teaching and learning in Biology and Environmental Science related to aquatic ecosystems, invertebrates, food chains & webs and diversity of living things. Concepts introduced include microorganisms, environment, marine, marine microorganisms, bacteria, phytoplankton, photosynthesis, brackish, food chain, zooplankton, nitrogen cycle, bioluminescent, mutualistic, algal blooms and metagenomics. 
  • Teachers could introduce this topic by engaging students with an Admit Slip learning strategy to activate their prior knowledge related to microorganisms. Ready-to-use reproducibles can be downloaded in [Google doc] and [PDF] formats.
  • Before students read the article, conduct a Vocabulary Preview learning strategy to have students identify words that may be new to them and to activate prior knowledge through the words they are familiar with. A Vocabulary Preview for this article is available for download in [Google doc] and [PDF] formats.
  • To consolidate learning, teachers could have students do a Concept Definition Web for the concept of marine microbes. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • To conclude, teachers could lead a discussion using one of the questions above to help students reflect on and consolidate the information they have learned.

Learn more

Marine Microbes (2010)

Video (2:45 min.) from the Australian Institute of Marine Science discussing some types of marine microbes, what they do, and the rise of potential harmful ocean bacteria.

Magnificent Marine Algal Blooms Seen From Space (2010)

Article by Betsy Mason for Wired including examples of satellite images taken of marine algal blooms from around the world.

The Brilliance of Bioluminescence (2013) 

Video (4:08 min.) from TED-Ed discussing bioluminescence, and the reactions and processes that occur in the animal kingdom to produce its glow - including the angler fish and its bacteria.

References

Australian Institute of Marine Science. (n.d.). Marine microbes.

Becker, J. (n.d.). A drop in the ocean is teeming with life. MIT WHOI.

Center for microbial oceanography. (n.d.). Marine microbes.

Lin, L. Y., & Meighen, E. A. (2009, January 25). Bacterial bioluminescence. Photobiology.info.

Lindsey, R., & Scott, M. (2010, July 13). What are phytoplankton? NASA.

Microbial Life Educational Resources. (n.d.). Microbial life in marine environments. Carleton College.

Roach, J. (2004, June 7). Source of half Earth's oxygen gets little credit. National Geographic.