Algae are a form of life*. This term collects at least 50 000 beings that are not closely related to each other (they are protists**), but have all developed the same way to live - by turning the light of the sun into energy (photosynthesis). Although cyanobacteria photosynthesize and they are often called blue-green 'algae', they are not technically algae as they are bacteria. Algae exist in countless forms ranging from microscopic single cells ('microalgae') to larger multicellular macroalgae (often called 'seaweed'). The majority are very small, and belong to the plankton - beings that drift in water, that cannot move against the current. This is just one way to categorise.
The first algae-like being appeared 3.5 billion years ago, and while it looked roughly the same as algae today, this does not mean that algae are primitive, they have had 3.5 billion years to adapt and evolve. Algae have adapted to the different conditions of the world’s waters. They are irreplaceable parts of these ecosystems, even blue-green algae. Our understanding of the roles algae play also changes as we learn more about them, and the roles themselves change as algae respond to changing environments. When algae bloom, they are sending a message about their waters. For example, when the spring sun returns to the Gulf of Finland, Skeletonema diatoms bloom and activate the food web. But when our human systems change these conditions, by changing the climate or increasing nutrients through our agriculture, this can favour certain algae over others (such as cyanobacteria) and lead to their excessive growth.
* A bit like the terms 'tree' or 'bush' (which don't describe only plants that are closely related to each other)
** Protist is a now informal term (previously kingdom) that describes all eukaryotic (organisms that aren't bactera or archaea. Their cells have a nucleus, which contains their DNA) that are not plants, animals or fungi. Protists are not all closely related to each other (unlike bacteria, archaea, fungi, animals and plants). Most protists are microscopic single cells, but there are also colonial and multicellular protists.
The first algae-like being appeared 3.5 billion years ago, and while it looked roughly the same as algae today, this does not mean that algae are primitive, they have had 3.5 billion years to adapt and evolve. Algae have adapted to the different conditions of the world’s waters. They are irreplaceable parts of these ecosystems, even blue-green algae. Our understanding of the roles algae play also changes as we learn more about them, and the roles themselves change as algae respond to changing environments. When algae bloom, they are sending a message about their waters. For example, when the spring sun returns to the Gulf of Finland, Skeletonema diatoms bloom and activate the food web. But when our human systems change these conditions, by changing the climate or increasing nutrients through our agriculture, this can favour certain algae over others (such as cyanobacteria) and lead to their excessive growth.
* A bit like the terms 'tree' or 'bush' (which don't describe only plants that are closely related to each other)
** Protist is a now informal term (previously kingdom) that describes all eukaryotic (organisms that aren't bactera or archaea. Their cells have a nucleus, which contains their DNA) that are not plants, animals or fungi. Protists are not all closely related to each other (unlike bacteria, archaea, fungi, animals and plants). Most protists are microscopic single cells, but there are also colonial and multicellular protists.
Tree of life with different algae groups highlighted (modified from a paper by Adl et al. 2012)
More information about algae and the microscopic world
- https://algaeexhibition.weebly.com
- Becoming Earth - Ferris Jabr
- Journey to the Microcosmos
- Pondlife
- Jam’s Germs
- https://planktonchronicles.org/en/
