alga

/ ăl′gə /

, Plural algae ăl′jē

1. Any of various green, red, or brown organisms that grow mostly in water, ranging in size from single cells to large spreading seaweeds. Like plants, algae manufacture their own food through photosynthesis and release large amounts of oxygen into the atmosphere. They also fix large amounts of carbon, which would otherwise exist in the atmosphere as carbon dioxide. Algae form a major component of marine plankton and are often visible as pond scum and blooms in tidal pools. Land species mostly live in moist soil and on tree trunks or rocks. Some species live in extreme environments, such as deserts, hot springs, and glaciers. Although they were once classified as plants, the algae are now considered to be protists, with the exception of the cyanobacteria, formerly called blue-green algae. The algae do not form a distinct phylogenetic group, but the word alga serves as a convenient catch-all term for various photosynthetic protist phyla, including the green algae, brown algae, and red algae.

Example Sentences

You may never have heard of this single-celled alga, but sailors and fishermen know its effect very well: the P. lunula algae are the organisms that occasionally make the see glow blue.

From Science Daily

The purpose of this brilliance remains unclear, especially because the alga lives too deep for it to be related to photosynthesis.

From Science Magazine

The alga, native to the Southern Ocean, starts as a single-cell that can transform into millimeter scale colonies.

From Science Daily

"More than 80 fish were observed around a single floating alga," said Mr Mazoudier.

From Science Daily

Blue-green algae is not actually an alga but rather a type of bacteria called cyanobacteria.

From BBC