Microorganisms you can see with a microscope in pond water
Here’s a quick guide to some of the creatures you might find in your local pond.
Protozoa
Some of the more interesting and easy-to-see microorganisms are protozoa, such as paramecia and amoebas.
They’re a diverse group of species and come in all shapes and sizes.
Protozoa will often stand out in pondwater samples, because they tend to be quite large and mobile.
They use a variety of interesting methods to move about. Some are covered with hair-like cilia that undulate to drive them forward, while others use rotate a tail-like flagellum as a propellor. Some protozoa can even extend part of their bodies like limbs to pull themselves along.
Bacteria
Bacteria are everywhere, and pond water is no exception.
They are, however, very tiny and quite hard to see even with a microscope.
You’ll need a minimum of 100x magnification just to see them as very small dots. At 400x, you can start to make out their shapes and see them moving. But it’s only at 1000x magnification that you’ll be able to get a relatively detailed look.
Bacteria are simple, single-celled organisms that comes in a variety of shapes and sizes, including rods, spheres or filaments. You’ll find them either alone or in colonies. Some have tail-like flagella that they use to motor around the pond in their search for food.
Some break down dead plant matter, recycling nutrients back into the ecosystem. Others are involved in symbiotic relationships with plants and fungi, fixing the nitrogen they need to grow. And, of course, bacteria are also an important source of food for many other pond species.
Algae
Algae are a common sight in most ponds.
They look quite similar to plants, but they don’t have leaves, roots or stomata. They do, however, photosynthesise just like plants, getting their energy from the sun, and come in the traditional plant colours – green, brown and yellow.
While algae can look bland to the naked eye, it’s a different story under the microscope. Different kinds of algae come in an astonishing array of unusual shapes and structures.
A group of free-floating algal species known as diatoms don’t resemble plants so much as colourful glass or aquatic snowflakes. Other species such as Spirogyra produce a helical arrangement of filaments that resemble a green strand of DNA.
Algae can also form spherical or star-like colonies, and sometimes look like green bananas, in the case of Closterium.
Microfauna
Microfauna, or micro animals, is a blanket term for a wide range of microscopic multi-cellular creatures. It’s an incredibly varied group, containing everything from tiny crustaceans to water bears.
Here are some of the more common varieties of pond microfauna you might encounter:
Arthropods
Arthropods are a huge group of invertebrates (animals with no backbones) that includes crustaceans, insects and arachnids.
They all have a hard outer shell known as an exoskeleton, segmented bodies and jointed legs.
You can find quite a few different species of arthropods in a pond. Look for mosquito larvae, tiny water fleas, seed shrimp and the oar-footed copepod.
Rotifers
Named for the unusual wheel-shaped corona of cilia around its mouth (rota = ‘wheel’ in Latin), rotifers are large filter feeders you’ll occasionally find in ponds.
They’re largely omnivorous, using their cilia to draw dead and decomposing matter into their mouths. They’ve even been known to feed on other rotifers.
Tardigrades (water bears)
The microscopic water bear is one of the hardiest creatures on the planet.
Resembling a chubby 8-legged bear, tardigrades can survive in almost any environment, but these semi-aquatic critters prefer to live in watery habitats such as ponds.
You’ll sometimes encounter one of the 1300 species of water bear pulling itself along using its stubby legs. You can recognise them by their barrel-like bodies, tube-like mouths and their 8 legs tipped with bendy claws, which allow them to cling to different surfaces.
You’ll also encounter flatworms, fungi, hydras and much, much more.