Six Ways in Which Algae is Our Friend

Algae comes in an array of colors, as with this seascape at Massachusetts’ Cape Ann.

ALGAE COMES IN EIGHT GAZILLION DIFFERENT FORMS, from tiny little slimy green stuff to giant kelp, and to most of us it seems obnoxious and a thing to be ignored, if not despised.

Except that algae is the foundation of the food chain, a pioneer in the evolution of life, and essential to our existence.  Algae uses sunlight to photosynthesize the carbon dioxide and hydrogen in water into the simple sugars that are nutrients for many animals – the process called “primary production.” And, in the battle against global warming, it serves as a significant agent for the removal of carbon from the environment. 

Animals as diverse as parrotfishes, damselfishes and black spiny sea urchins all directly survive on algae. Even the kelps that thrive in colder waters provide food and shelter for herbaceous fishes and invertebrates. And their broad blades and stipes (“leaves”) function as hosts for the bacteria preyed on by snails and other invertebrates. 

The algae that starts the food chain is more likely to be micro-types that are barely visible to us.


This launches the food-chain process in which nutrition is transferred from smaller herbivores to larger predators, on up the web until it reaches apex predators, quite possibly ending up on our dinner table in the form of a tuna steak.

As a byproduct to the whole thing, algae produce much of the planet’s oxygen, releasing it from the carbon dioxide consumed in photosynthesis. It’s estimated that at least 50 percent of all the earth’s primary production still takes place in the oceans – some scientists put the oceans’ share to be as high as 90 percent.



Algae regularly get referred to as “plants” in casual conversation. Scientifically, they’re protists, organisms separate from animals and plants, with some characteristics of each. As such, they’re located in a separate kingdom from the animal, plant and fungi kingdoms and from the bacteria and archaea domains. Many protists are single-celled organisms but some, like seaweeds, are multicellular.

Red algae from Cape Ann. No matter what color it is, it’s green. Reds and browns mask the green Chlorophyll “a,” found in all algae and plants, that is the world’s principal driver of photosynthesis.


On land, it’s grasses, trees and other plants that are the engines of photosynthesis. Without algae in the oceans, the tree-and-grass world we know wouldn’t have happened. Algae led the way in the move from the oceans to dry land. Some 420 million years ago, when there was life in the seas and none whatever on the earth’s landmasses, green algae were the pioneers that made the jump to land-plant organisms, developing impermeable walls for internal water reservoirs that let them live outside the oceans.

PRINCIPAL SOURCES:  Marine Biology, Fourth Edition, Peter Castro, Michael Huber; Marine Biology, An Ecological Approach, James W. Nybakken; National Oceanic and Atmospheric Administration; Monterrey Bay Aquarium Research Institute; “Photosynthesis,” Maricopa Community College;, Royal Botanic Garden Edinburgh; “Asteroidea,” Tree of Life Web Project; “An Introduction to Photosynthesis and Its Applications,” Arizona State University;“ Photosynthetic Pigments,” University of California Museum of Palentology, Berkeley.

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