What Different Types Of Microorganisms Are Found In Pond Water?

In every little drop of pond water, there is a world of microorganisms invisible to the naked eye. These tiny creatures are incredibly varied and abundant.

What Different Types Of Microorganisms Are Found In Pond Water?

In only a single drop of pond water, you’d be able to find forms of life such as bacteria, algae, protozoans, and even adorable microscopic water bears! 

In this article, we will take a closer look at these microscopic life forms. With our guide and a microscope, you’ll be able to see this world of tiny creatures too, and discover how they are able to live in pond water.

Without further ado, let’s take a closer look at what you can see in a single drop of pond water under a microscope.

What Are Microorganisms?

Microbes or microorganisms are microscopic organisms that exist all over the globe. They can be comprised of single celled organisms or clusters of cells.  Because they are so small, they can only be seen through a microscope.  

Microorganisms are mostly comprised of prokaryotic cells, such as bacteria and archaea. Otherwise, they can also be unicellular protists, which come under the umbrella of eukaryotes.  Protists are types of cells that can be subdivided into the following:

  • Protozoa – cells that are like microscopic animals, which includes amoeba and paramecium 
  • Protophyta – cells that are similar to plants, such as green, red or brown algae and diatom 
  • Molds – fungi like smile mold and water mold

Pond water usually contains a wide variety of microorganisms. These microorganisms can be single cell organisms or clusters of organisms that form colonies of large numbers, sometimes thousands of cells. These are what’s known as multicellular organisms.  

Most microorganisms that can be found in pond water are between 100 and 500 micrometers in size. 

The size of different organisms found in pond water can vary significantly.  For example, Amoeba, Euglena, and Paramecium are comprised of one large cell, known as a single cell organism or a unicellular organism.

These organisms are classified as protists.  Other types of organisms, such as tardigrade and rotifer, are comprised of many thousands of cells, and they are called multicellular animals. 

If you look at a drop of pond water under a microscope, you are likely to see the following organisms:



In pond water, you can typically find arthropods such as ostracods, copepods, and water fleas.

These organisms can be seen with the naked eye, as the largest specimen of athropod measures over 3 millimeters in length, so you don’t need a microscope to see some arthropods.  

Other microorganisms that are classified as arthropods include mater mites, water shrimp, water bears or tardigrades, mosquito larvae, and crustaceans such as water lice.  

Most types of arthropods can be found on the surface of the water, while others only can live beneath the surface of the water, which generally is the case with crustaceans. 



Among the most common and smallest microorganisms found in aquatic systems, bacteria can multiply rapidly in the right conditions. For example, after rainfall has occurred, bacteria can dramatically multiply into millions of bacteria per meter. 

In a pond, bacteria can typically be seen on the surface of decaying leaves, or on rocks, wood, or metallic objects.  

There are multiple types of bacteria that can be found in pond water, including heretrophic and autotrophic bacteria.

The former plays a big role in the decomposition of organic matter. The most common bacteria found in pond water are anabaena and nostac. These bacteria are known as cyanobactera, which causes the green color of pond water.



Protozoa are known for being characteristically similar to animals in many ways.

They make up the majority of microorganisms found in pond water, not only in terms of the number of organisms but in diversity and biomass.  Because of this, protozoa varies wildly by their size, shape, and the features they have. 

Protozoa are also capable of forming large clusters or colonies. Similarly to bacteria, there are also hererotrophic and autotrophic protozoa, however, unlike bacteria, protozoa consume many other organisms such as other protists or algae.  

Along with many other microorganisms that can be found in pond water, protozoa are also responsible for comprising the bio film that covers the surface of the water.

Protozoa can move around, making it possible for  colonies of protozoa to move without having to rely on the movement of the water.  

The most common protozoa found in pond water are ciliates, paramecium, and amoebas.  They have the ability to move around whilst consuming other organisms. 



Hydra are categorized as hydroza, and they are typically found in marine environments.  They are predatory animals as they have the ability to hunt for their prey.  

Hydra gets its name from the mythical snake-like creature from Roman and Greek mythology, as hydra have multiple tentacles around their mouth, similar to the many heads of the mythical hydra.  

Hydra are a microorganism that can measure up to 30mm long when fully extended.  They are difficult to see with the naked eye, so it helps to at least use a hand lens to see them properly.  

Hydra can be different colors, depending on their specific type.  They are usually green or brown.  This coloration is because of hydra’s relationship with algae. 

This type of microorganism can also be found on the surface of a pond or clinging onto any given surface.  They are able to move around by gliding along the surface of the water or sumersaulting along the substratum. 



Algae are abundant autotrophic protists in pound water.  They are for the most part green in color, but they can also be brown or a yellowish brown.  Algae are also a diverse organism, and they can be multicellular or unicellular. 

The most common forms of algae that you can find in pond water are chlamydomonas, euglena, and spongomonas.

Chlamydomonas can swim freely in water when looking for food to consume, whereas spongomonas exist only in gelatinous matrices and they use their distinctive features to feed themselves without having to move. 



Gastrotrichs are also known as hairybacks or hairbellies. They are microscopic worm-like creatures with a brain and other sensory organs, and a simple gut.

They have skin that is covered by lots of cilia, which is what gave gastrotrich is common name as they look hairy.  

Gastrotrich mainly live on the bottom of ponds, feeding on detritus that sinks down to the floor.  They feed by sucking organic particles up by using their muscular pharynx. 



Tardigrades are also known as moss piglets or water bears. They look like microscopic bears who move slowly around using their eight small legs.  They are known for being able to survive in very harsh conditions.

They can perform a process called cryptobiosis, making them dormant and dried up, allowing them to survive for years without the need for water. 

They can live in temperatures ranging from -270 °C and 150 °C.  They can also withstand extreme levels of pressure, like the pressure at the bottom of the Mariana Trench. 



You may not think of fungus as a microorganism as they can be easily seen with the naked eye, but fungi are actually single celled organisms.

They can be found in small filaments known as hyphae, which usually have a mutualistic relationship with other living things such as plants.  

Fungi is heterophic, and it can release enzymes into their environment, breaking down organic compounds and nutrients so that they can be consumed by the fungi and other microorganisms.

For this reason, fungi is essential for the cycling of nutrients, in addition to the process of decomposition. 

What’s Important About Microorganisms?

All organisms play an important role in their ecosystems, and the same can be said about microorganisms.  Autotrophic microorganisms such as algae produce nutrients for many other organisms.

They are consumed by protozoans, which then get consumed by larger predators.  This ends up being a long food chain within the aquatic ecosystem alone.

How Are Microorganisms Named And Classified?

The science of classifying biological organisms is called ‘taxonomy’.  By naming and categorizing different species, it helps us to differentiate them from each other, and see how similar they are in the way they live.  

Taxonomy works much like how books are organized in a library.  Different types of microorganisms are classified based on their species, and then these sections can be divided further into subcategories – much like how books in a library are separated into sections, and these sections are organized into subsections.

A common system of taxonomic classification has 7 main levels.  The first of these levels are known as the Kingdoms (plants, animals, and bacteria).  Next is the Plylum, Class, Order, Family, Genus, and finally the Species.  

Some species of microorganisms are difficult to classify by these systems, such as euglena. Euglena shares some characteristics of both animals and plants. 


Pond water can also be classified as freshwater.  Because of this, the two terms can be used interchangeably when referring to the types of microorganisms found in freshwater.

Microorganisms are abundant and incredibly diverse wherever you look for them.   They are so varied that there’s not much that different types of microorganisms have in common.

They are, however, essential for many ecological processes, and life as we know it would not be possible without them.

They are responsible for releasing oxygen in addition to breaking down living organisms, decomposing them and prompting the carbon cycle to release essential nutrients, making them accessible to other living organisms. 

Ponds are a great place to look for a wide variety of microorganisms.  Naturally occurring ponds, in particular, have a much greater diversity of microorganisms than man made ponds.

Jennifer Dawkins

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