Most of us have heard the term algae used when we see that slimy green goo caked on rocks along the beach, or when we see a mold-like muck in the water of an outdoor Jacuzzi that’s overdue for a clean. You may have even heard of them in the news, with headlines reading “Dangerous algal bloom appears off the coast”. But what actually are algae? Are they plants? Fungi? Is it even alive or just some kind of aquatic debris that collects over time? And what purpose could they possibly serve?

algae_audioYou can listen to our podcast on algae here. Well, while science can definitively say they are living organisms, a strict definition has eluded scientists even today. In fact, the creatures currently referred to as algae span several different major groups of organisms including plants, bacteria, protozoans, and the relatively newly named “chromists” (Guiry 2012, Ruggiero et. al 2015). Some named algal species may or may not be considered algae (I’m looking at you, cyanobacteria) depending on the scientist in question, but most can agree on a few generalized features which all algae should share. They should be found in or very near damp places. This includes both salt and fresh water, and as such can be found in lakes, rivers, and oceans around the world. Algae are not restricted to water however, and also can be found in a myriad of terrestrial habitats from living on the side of rocks and trees to growing on the bodies of worms and the shells of turtles. Secondly, they are able to create their own food via sunlight (a process called photosynthesis) and produce oxygen as a result. Although this may make them sound very similar to land plants, a major feature that separates them is their body structure. A large number of algae are unicellular, meaning their body plan is composed of a single cell; this is opposed to true plants (and animals), which are multicellular. Other algae form cell colonies, or are multicellular but without the tissue differentiation into the leaves, stems, and roots we’d expect from true plants (Guiry 2012).

Given the generality of their definition, it’s no surprise to learn that algae are diverse in their appearance. In fact, most seaweeds are actually algae. Even the giant kelp forests that you may kelp foresthave seen in nature documentaries are, indeed, fields of algae swaying in the ocean current, providing protection to the animals that live within them. On the other side of the spectrum are the tiny, microscopic creatures known as phytoplankton. They act as a primary food source for small crustaceans and fish and are an integral part of aquatic food chains. Some algae even work symbiotically with other organisms, such as corals, to provide them with nutrients for survival in exchange for protection (Baker 2003). There are estimates of over 150,000 species of algae to date, and their global distribution sheds light on the weight of their ecological importance (

red_tide_genera.v3Although they aren’t given too much attention in the mainstream, they make substantial impacts to our planet’s ecosystems. For one, they produce a size-able amount of the oxygen found both in the air and in our oceans. In addition, disturbances in algal communities can have devastating effects on the local ecosystem in the form of algal blooms. During a bloom, microscopic algae exponentially grow in number, sometimes changing the color of the waters for which they reside (an example being a “red tide”). When certain algae reach such high numbers, chemicals they release into the surrounding water become so concentrated they turn toxic; causing illness and sometimes death for both for the surrounding aquatic animals and the humans who may consume them. In fact, a bloom has been attributed to the death of over 343 whales which washed up along the Chilean coast in 2017, supposedly killed by toxins they had ingested (Hakai Magazine). Further, an algal bloom decomposes, it removes oxygen from the surrounding water which can lead to fish and other aquatic animals actually “drowning” due to their inability to breathe. While blooms do occur naturally, human intervention has led to the increase in their appearance. Nutrient dumping either through waste or run-off adds compounds into our rivers and lakes that result in the algae’s rapid growth; header-killer-algae2a process called eutrophication. As such, scientists are working to better manage water pollution in part to help reduce the frequency of  these events from occurring (Anderson et. al 2002).

So now when you see the slimy green gunk on the underside of a boat or see a bed of kelp floating in the ocean, you can you can better appreciate what they are all about. Whether they be several feet in length or the size of a pin needle, algae are an integral part of all aquatic and several terrestrial ecosystems. Although they look unassuming enough, and maybe at times a bit gross, their existence on our planet impacts the very air we breathe, and our ability to attend our beaches unscathed.

Anderson, D. M., Glibert, P. M., & Burkholder, J. M. (2002). Harmful algal blooms and eutrophication: nutrient sources, composition, and consequences. Estuaries25(4), 704-726.

Baker, A. C. (2003). Flexibility and specificity in coral-algal symbiosis: diversity, ecology, and biogeography of Symbiodinium. Annual Review of Ecology, Evolution, and Systematics34(1), 661-689.

Guiry, M. D. (2012). How many species of algae are there?. Journal of phycology48(5), 1057-1063.

Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 03 September 2018.

Ruggiero, M. A., Gordon, D. P., Orrell, T. M., Bailly, N., Bourgoin, T., Brusca, R. C., … & Kirk, P. M. (2015). A higher level classification of all living organisms. PloS one10(4), e0119248.

Article on whales:

Photo credits:
algae on rocks:Zoran Milisavljevic via
kelp forest: NRDC via Flickr
red tide:Photo by Miriam Godfrey
whales: whales killed by algal bloom off the Chilean coast; Photo by Keri-Lee Pashuk

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