Here you can see tons of freshwater algae Chloé Savard found in a pond located an hour from Montreal! These algae are highly diverse; they come in all shapes and colours and yes, most of them move around as if they were little animals! Algae and animals are both eukaryotes but unlike animals, algae possess chloroplasts and are able to produce their own source of food by a process called photosynthesis.
Freshwater algae are at the bottom of the food chain as primary producers, transforming CO2 and energy from sunlight into sugars by photosynthesis. These algae then get eaten by a lot of small herbivores including rotifers, crustaceans, ciliates, worms and insect larvae which are all placed in the second level of the food web. Those small invertebrates then get eaten by bigger carnivorous animals, like fish, frogs, birds and aquatic insects, which are classified in the third level of the food chain.
All freshwater algae are aquatic and photosynthetic (they all possess chlorophyll a). Although the vibrant colours of freshwater algae come from different pigments they possess. Green algae and euglenoids get their green colours from chlorophyll a and b while golden algae and diatoms get theirs from chlorophyll a and c but also from fucoxanthin. Freshwater algae also come in many many shapes and organisations; some are unicellular (like most of those in this video) while some others are colonial (like Volvox or Synura) or even filamentous!