What Is Algae: Learn About Types Of Algae And How They Grow

Pond Covered With Green Algae
pond algae
(Image credit: jeancliclac)

We understand a great deal more about the world around us than our ancestors did 100 or so years ago, but there are still some mysteries that remain. Algae is one of them. Blurring the line between plant and animal with their chlorophyll, eyespots, and flagella, algae has confounded even scientists, who have sorted algaes into two Kingdoms: Protista and Prokaryotae. How algae relates to your landscape is a difficult question. It can be both friend and foe, depending on the circumstances.

What is Algae?

There are numerous types of algae, divided into 11 phyla. Many species live in saltwater, so are not something you'll run into often, but three main groups make their homes in fresh water. These algae belong to:

  • Phylum Chlorophyta
  • Phylum Euglenophyta
  • Phylum Chrysophyta

The types of algae growth you see in your backyard pond is due to one of these three groups, most often the green algae in Phylum Chlorophyta or the diatoms belonging to Phylum Chrysophyta. If you were to put algae under a microscope, you'd see that they're mostly made up of a single cell. Many have flagellum that help them move about. Some species even have a rudimentary eyespot that helps them locate and head toward light sources. Due to the wide range of creatures included under the umbrella, algae identification can be tricky at the cellular level. It's easy to see when these creatures have overrun your pond though.

Is Algae Control Necessary?

Algae are pretty amazing creatures that can move around, but also produce their own food. Some gardeners might tolerate them simply because they're so fascinating, but unless algae colonies are the only thing you're growing, you should consider controlling these organisms. Unfortunately, algae tends to bloom and die rapidly, first flooding your pond with the oxygen it produces while it removes all the nutrients from the water. Once all those nutrients are spent and the water is overly-oxygenated, the algae colonies die back dramatically, creating an opening for a bacterial bloom. All this cycling, not to mention the competition for nutrients, is hard on your pond plants and animals, so control is usually recommended. Mechanical filtration can catch some algae, as well as helping to eliminate the dead colonies, but you'll need to change or clean your filtration medium every few days until your algae colonies are under control. Whole pond changes are dramatic, but can eliminate most of your algae colonies if you scrub the liner well with an algaecidal disinfectant. If your algae problem isn't too bad and your pond life can tolerate it, regular treatment with an algaecide is a good idea.

Kristi Waterworth

Kristi Waterworth was a regular contributor to Gardening Know How for many years, answering countless queries on plant pests and diseases.