Weekly Sea Discovery: What are phytoplankton and why are they globally important?

In this week’s Sea Discovery, we are going microscopic! Lately, you may have noticed the waters surrounding Mayne becoming very green and murky. This colour change is due to microscopic algae known as phytoplankton.

These are various diatom phytoplankton species under a microscope. Their glass frustule shells form incredible geometric shapes. Photo: ZEISS Microscopy
What are phytoplankton?

Their name derives from the Greek words “phyto” meaning plant, and “plankton” meaning “to wander” or “drift”. From the arctic to the tropics, phytoplankton are distributed across all latitudes. Like larger algae and terrestrial plants, these single-cell plants get their food by transforming carbon dioxide into carbohydrates using the sun’s energy through photosynthesis. Phytoplankton depend on nutrients and light to be able to grow and reproduce, forming blooms.

Sometimes these blooms are so massive they can be seen from space. In 2016 a large bloom of coccolithophore phytoplankton created incredibly green waters in the Strait of Georgia (photo below).

Coccolithophore phytoplankton bloom in the Strait of Georgia, August 19th 2016. Photo: NASA Observatory
Toxic phytoplankton

Some phytoplankton (like diatoms and dinoflagellates) produce toxins that can be dangerous for various marine species, like fish and marine mammals, as well as humans. Here in BC, you may be familiar with the harmful algal bloom, red tide. The dinoflagellates responsible for this bloom produce a toxin that causes paralytic shellfish poisoning. It is essential to check where there are current shellfish closures, as it is illegal and unsafe to harvest in these areas.

The base of global marine ecosystems

In marine and aquatic ecosystems, phytoplankton are at the base of the food web and have a vital role in the carbon cycle. These micro-organisms are responsible for consuming the same amount of carbon dioxide as all of the plants on land combined! They also provide over half of the Earth’s oxygen production every year. Therefore, they contribute to the stability of our atmosphere and oceans, while regulating climate change.

This diagram shows the transfer of carbon in the marine environment. To learn more about the biological carbon pump visit the Earth Observatory.

Did you know one of the oldest phytoplankton groups known as cyanobacteria played a crucial role in the formation of Earth’s oxygen-rich atmosphere?

Even though we can’t see them with our naked eye, these tiny marine plants are possibly the most important organisms on Earth. They have the power to change our global climate and marine ecosystems on a large scale.


Phytoplankton: Arguably the Most Important Life on Earth (Video)

Canadian Waters Teem With Phytoplankton (Article)

Importance of Phytoplankton (Article)


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