Algae are diverse photosynthetic organisms found in various environments, from oceans and freshwater bodies to damp soils and tree bark. Ranging from microscopic single cells to large seaweeds, they form the base of many food webs. As primary producers, algae convert sunlight into energy, making it available to other life forms. Many organisms across different habitats depend on algae as a fundamental food source.
Microscopic and Invertebrate Algae Eaters
Many tiny organisms consume algae, forming crucial links in aquatic food webs. Zooplankton, a group of microscopic animals, are primary grazers of phytoplankton, which are tiny marine and freshwater algae. Copepods, for instance, graze on microalgae and diatoms. Rotifers and daphnia are other common zooplankton that consume algae.
Small invertebrates also consume algae. Aquatic snails, such as nerite, ramshorn, and bladder snails, scrape algae off surfaces in freshwater and marine environments. Various crustaceans, including crabs, shrimp, amphipods, and isopods, feed on algae. Freshwater shrimp, like Amano and Neocaridina shrimp, consume softer algae types.
Aquatic insect larvae also eat algae. Mayfly nymphs primarily consume algae and detritus, often using specialized mouthparts for grazing or filter-feeding. Caddisfly larvae include species that graze on periphyton, a layer of algae and associated organisms, found on underwater objects.
Fish and Other Aquatic Vertebrate Algae Eaters
A variety of fish species, both freshwater and marine, are known for their algae-eating habits. In freshwater aquariums, plecos (short for Plecostomus) are popular, with some species, like Bristlenose plecos, effectively cleaning algae from tank surfaces and driftwood.
Otocinclus catfish are smaller, peaceful algae eaters that specialize in consuming soft green algae and brown diatoms, often found grazing on plant leaves and tank walls. Certain cichlids, particularly Mbuna cichlids from Lake Malawi, are primarily algae eaters in their natural habitat, using their specialized mouths to scrape algae from rocks.
Marine environments host several prominent algae-eating fish. Surgeonfish are primarily herbivores that graze on green and brown algae from coral reefs and rocks, helping to maintain the health of these ecosystems.
Parrotfish are another group of colorful, tropical fish that spend a significant portion of their day consuming algae off coral reefs, using their beak-like teeth to scrape both macroalgae and microalgae. Some carp species, like the common carp, are omnivores that include aquatic plants and algae in their diet, while grass carp are specifically used to control certain types of aquatic weeds and algae in ponds.
Other aquatic vertebrates also consume algae. Some species of turtles, such as adult green sea turtles, are primarily herbivorous and feed on algae and seagrasses. Manatees, large aquatic mammals, are also herbivores that eat a wide variety of aquatic vegetation, including algae, especially when their primary food source, seagrass, is scarce. Certain waterfowl, including ducks and geese, consume filamentous algae and other aquatic plants.
Land-Based and Semi-Aquatic Algae Eaters
Algae are not exclusively consumed in aquatic environments; various land-based and semi-aquatic organisms also rely on them as a food source. Terrestrial snails and slugs, often found in damp gardens or forests, graze on algae and fungi that grow on surfaces like rocks, tree bark, and moist soil. Their feeding activities can leave characteristic “tracks” where they’ve scraped off the algal film.
Certain insects also feed on terrestrial algae. Springtails, tiny arthropods found in moist environments, consume algae, mold, and decaying organic matter. Some beetle larvae graze on algae found in shallow waters or on decaying organic matter. Alkali flies have larvae and adults that feed on algae beneath the surface of salty lakes.