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Longman Dictionary of Contemporary English
▪ Complete removal of green algae from the aquarium is very difficult unless chemicals are used.
▪ Now it's choking with thick green algae.
▪ Filamentous green algae are seldom a nuisance unless they are allowed to reproduce excessively.
▪ I wish to eventually add invertebrates to this tank. Green filamentous algae can be a big problem in some tanks.
▪ Summer often brings a green coloration caused by dense growths of unicellular green algae stimulated by excess light.
▪ The tank has green hairy algae all over the rocks, heaterstat, gravel and glass.
▪ This may contain phosphates, sulphates and nitrates in abundance - enough to start a green algae plague.
▪ They graze on the algae that grow on the coral.
▪ There was algae and seaweed growing on the top layer of bamboos, which was certainly not there before.
▪ Current cryptogamic research areas include: diatoms, algae, fungi, lichens, bryophytes and ferns.
▪ Cyaniding a reef, on the other hand, kills the reef, by allowing bacteria and algae to set in.
▪ So the algae hang on as debilitating parasites rather than evolving towards benign cooperation.
▪ Specific ways of checking individual groups of algae are discussed below.
▪ There are changes in the number and species of protozoans, algae, and bacteria.
▪ There was algae and seaweed growing on the top layer of bamboos, which was certainly not there before.
▪ White fluorescent light increases the rate of growth of this plant while apparently not encouraging unwanted algae formation.
▪ Yves Rocher Dynamic Corp Bio-Vegetal range includes gel, tonics and creams all with a high proportion of sea algae.
The Collaborative International Dictionary

Alga \Al"ga\, n.; pl. Alg[ae] or algae. [L., seaweed.] (Bot.) A kind of seaweed; pl. the class of cellular cryptogamic plants which includes the black, red, and green seaweeds, as kelp, dulse, sea lettuce, also marine and fresh water conferv[ae], etc. The algae are primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves.


algae \algae\ n. plural of alga.

Douglas Harper's Etymology Dictionary

(plural), 1794, from alga (singular), 1550s, from Latin alga "seaweed," which is of uncertain origin, perhaps from a PIE root meaning "to putrefy, rot."


n. (en-irregular plural of: alga)


n. primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves [syn: alga]

Algae (disambiguation)

Algae are a type of Protist.

Algae may also refer to:

  • Algae fuel, a biofuel
  • Algae (programming language)
  • Algae eaters, species that feed on algae
  • Snow algae, cold-tolerant species of algae
  • Ice algae, algae that live in sea ice
  • AlgaeBase, a database of algae
  • Algae Lake, lake in Antarktis

Algae (; singular alga ) is an informal term for a large, diverse group of photosynthetic organisms which are not necessarily closely related and are thus polyphyletic. Included organisms range from unicellular genera, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 meters in length. Most are aquatic and autotrophic and lack many of the distinct cell and tissue types, such as stomata, xylem and phloem, which are found in land plants. The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and the stoneworts.

There is no generally accepted definition of algae. One definition is that algae "have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells". Some authors exclude all prokaryotes and thus do not consider cyanobacteria (blue-green algae) as algae.

Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria. Diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga.

Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction.

Algae lack the various structures that characterize land plants, such as the phyllids (leaf-like structures) of bryophytes, rhizoids in nonvascular plants, and the roots, leaves, and other organs that are found in tracheophytes ( vascular plants). Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy. Some unicellular species of green algae, many golden algae, euglenids, dinoflagellates and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic, relying entirely on external energy sources and have limited or no photosynthetic apparatus. Some other heterotrophic organisms, like the apicomplexans, are also derived from cells whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago.

Usage examples of "algae".

The algae naturally and continuously desalinated sea water, which was why its core was salty while its outer surface was wet with fresh water: it was oozing the fresh water out.

Nothing distracted the meerkats from their little lives of pond staring and algae nibbling.

A sloth’s hairs shelter an algae that is brown during the dry season and green during the wet season, so the animal blends in with the surrounding moss and foliage and looks like a nest of white ants or of squirrels, or like nothing at all but part of a tree.

It was striking-looking in an ugly sort of way, with a rugged, yellowish brown shell about three feet long and spotted with patches of algae, and a dark green face with a sharp beak, no lips, two solid holes for nostrils, and black eyes that stared at me intently.

The smell of spent hand-flare shells, and prayers at dawn, and the killing of turtles, and the biology of algae, for example.

In the algae that covered the shells of some hawks-bills I sometimes found small crabs and barnacles.

It seemed to be a variety of marine algae, but quite rigid, far more so than normal algae.

In cross-section it consisted of two concentric walls: the wet, slightly rough outer wall, so vibrantly green, and an inner wall midway between the outer wall and the core of the algae.

The algae had a light sweetness that outdid in delight even the sap of our maple trees here in Canada.

The tree did indeed grow right out of the algae, as I had seen from the lifeboat.

Evidently the algae covered the shore thickly, for it was all I could find.

Finally, I resolved the problem by driving an oar, handle first, deep into the algae and tethering the boat to it.

I thought it was a cramp, that perhaps I had poisoned myself with the algae.

After a few seconds, they went back to doing what they had been doing before I appeared, which was either nibbling at the algae or staring into the ponds.

I did not ask myself why the algae did this, or how, or where the salt went.