COOL Classroom 2.1

Discover Microbe Size and Abundance

In this section,you will learn about how small microbes really are…

Bigger is better, right? Well, if we’re talking about desserts and bank accounts many people would probably agree with that statement.
But, what about things that are small – really small? Are they important, valuable or interesting? If we are talking about living organisms on our planet then the answer is YES! If those organisms are in the ocean definitely, yes.

What comes to your mind when you think of life in the ocean? Many people immediately think of whales, dolphins, sharks, sea turtles, seals, sea otters or other animals. Sure, these animals are cool, but they all have something else in common, they are all MACRO organisms. This means they are BIG and able to be seen by the human eye.

Is there life in the sea that you cannot see? Yes, these are called micro organisms. Microbes (both those on land and in the water) are organisms so small you need equipment to view them.

Let’s start here…

How wide do you think a human hair is? In other words, not how long (like hair of a rock star or your sister), but how thick?

A. 1 m
B. 1 cm
C. 1 mm
D. 0.1 mm

Right…0.1 mm. Meaning, if you were to look at one millimeter on a ruler and then slice it into ten pieces, each piece would be 0.1 mm. An average hair is about that size.

How small do organisms really get and if you can’t easily see them, how do you find out about them?

Viewing Marine Microbes

Usually, we use a magnifying glass or a light microscope to enlarge whatever it is we are trying to see. Some things are so small that traditional microscopes cannot even see them.

Scientists then use a scanning electron microscope (SEM for short) that creates a magnified image by using electrons instead of light waves. Using this method, marine microbes and other microscopic objects can be magnified more than 200,000 times! Another advantage of the SEM is that it creates
3-D images, whereas traditional light microscopes allow you only to see the surface of the image you are viewing.

The pictures below show two common marine microbes taken with a SEM. The image on the left is a diatom, magnified at 500x. It is a single-celled plant that is abundant in both marine and freshwater environments.

The image on the right is a photo of a radiolarian magnified 750x. It is a free-floating microbe that feeds on phytoplankton (such as diatoms) and bacteria.

Marine Diatom (magnification x500)


Marine Radiolarian (magnification x750)


How Many Are There?

Now that you understand how small microbes are, let’s try to picture how many are in the water.

Think of a 2-liter bottle of soda ~ if you go to the beach and fill the bottle with ocean water, chances are you have scooped up over 2 billion microbes, that’s 2,000,000,000 in just one bottle!