Part 2 – What are Green Algae?

The most common type of algae is green algae. In some instances, mostly in salt water, “green” algae may also look brown, red or gold. These species can be single-celled, multi-celled or colonial. Although most are aquatic, green algae are also found on tree trunks, moist rocks, snowbanks and creatures like turtles, sloths & mollusks.

Green algae is very old; some fossils have been dated to 1 billion years. There are three classes: one marine and two freshwater. The freshwater algae are the precursors of the plants of the Earth. This is the most diverse group of algae, having some 8000 species. They vary greatly in both size and shape. However, all contain both Chlorophyll-a and Chlorophyll-b (which give them their green color), as well as secondary pigments like beta carotene and xanthophyll. Sunlight is needed for photosynthesis.

Some species feel slimy; others feel like green wool. Green algae make their own food, which is stored as starch, and reproduce by asexual reproduction. They can live up to 30 years!
Unless someone has a special sensitivity, green algae is not generally harmful to humans. However, it can reach nuisance levels, especially in the case of filamentous algae. Although there are several species of filamentous algae, all are comprised of long chains of single cells. They can form big mats that interfere with recreation, shade out sunlight, and even use up oxygen needed for fish.

This series about algae in our waters was written by Lake Specialist Reesa Evans of the Adams County Land & Water Conservation Department. She is also a lake manager certified by the North American Lake Management Society.