Diversity of aquatic species

Even a small pond is teeming with life. How many different species of animals and plants are there in Finnish lakes and rivers, and which groups are the most numerous?

It has been calculated that around 5,000 different organisms live in Finnish inland waters. This is almost one ninth of all species in Finland. While the majority of aquatic organisms are animals, more than one thousand algae species have been identified, mostly single-cell planktonic algae, and a couple of hundred aquatic plants.

Most of us know best the larger animal species living in water: fishes and other vertebrates, as well as crayfish, mussels and gastropods. However, the large species only represent a small part of the diversity of the fauna in our inland waters. A much larger number of different invertebrates is hiding under the surface.

Insects are the group with the largest number of species; around 1,640 species have been found in Finnish inland waters. This may seem an incredibly large number – until you come to think about larvae. And there is no shortage of them in waters: the larvae of mosquitoes, dragonflies and many other flying insects. More than one half of the insect species found in inland waters are different types of flies. They are counted as aquatic species, as the larval stage spent in water is a vital part of their life cycle.

Other relatively numerous animal groups include microscopic rotifers as well as tapeworms and crustaceans. Groups of species considered primitive are well represented in the aquatic environment; after all, water is the cradle of life.

Life under water is amazingly rich. Buy or make yourself an aquascope. You will be able to see beneath the surface!