Hi Anna,

I think in the first and third cases, the correct word would be "algal", the adjective of alga. As for the second, I would think "alga-colonized", in the same way you would say "termite-infested" and not "termites-infested".

Good luck!

Álvaro :O) :O)

I've never heard the term "alga" used either. In support of the posting by JAGirard, the Chambers 21st Century Dictionary has no separate entry for "alga", and has the following to say:
"Algae /'algi: plural noun (singular alga) a large and very diverse group of mainly aquatic organisms, ranging from single-celled members of the plant PLANKTON to large multicellular seaweeds. Origin 16th C., as alga Latin, meaning 'seaweed'.

This is an authoritative dictionary, so please feel free to believe what it says....

I just wanted to add that there certainly are occasions when I have had to use the word 'alga' in the singular - very recently in fact, when talking about lichens. However, in the cases you mention, Anna, such as 'algae mats' etc, I would agree that the plural term 'algae' should be used.

Tom Volk's Fungus of the Month for July 2002, Cladonia cristatella ...
... This particular lichen is formed when the fungus and the alga come together.
In a mutualistic symbiosis, both organisms should benefit. ...
botit.botany.wisc.edu/toms_fungi/jul2002.html - 8k - Còpia en memòria - Pàgines semblants

Cladonia rangifera, one of the reindeer lichen, Tom Volk's Fungus ...
... As you may know, a lichen is a "dual organism," a mutualistic association between
a fungus (the mycobiont) and an alga or cyanobacterium (the photobiont). ...
botit.botany.wisc.edu/toms_fungi/dec2000.html - 12k - Còpia en memòria - Pàgines semblants
[ Més resultats a botit.botany.wisc.edu ]

MSN Encarta - Lichen
... The relationship between the fungus and the alga in a lichen is an example of mutualism,
in which both partners benefit from the partnership (see Symbiosis). ...
encarta.msn.com/encyclopedia_761563114/Lichen.html - 55k - Còpia en memòria - Pàgines semblants


The Hermit and the Recluse Retreat
... together. Lichen is made of an alga and a fungus living together. Both ... The fungus
in turn, provides water and minerals for the alga. The fungus ...
groups.msn.com/ TheHermitandtheRecluseRetreat/yourwebpage1.msnw - 30k - Còpia en memòria - Pàgines semblants

Product Licensing Guidance Document
... (b) When the ingredient is a plant or a plant material, an alga, a fungus, a bacterium,
a non-human animal material or a probiotic, the Latin name of its genus ...
www.hc-sc.gc.ca/hpfb-dgpsa/ nhpd-dpsn/product_licensing_2_e.html - 40k - Còpia en memòria - Pàgines semblants

[PDF] LICHENS
Format del fitxer: PDF/Adobe Acrobat - Versió HTML
... The fungus provides protection from environmental stress, such as excess light.”
And, unlike the alga, the fungus reproduces sexually. ...
www.ars.usda.gov/is/AR/archive/jan01/lichen0101.pdf - Pàgines semblants

English term (edited): alga

As a native English-speaking botanist and writer, I would disagree with your translators. 'Alga' is in regular use in the scientific community and there is a clear divergence between scientific and colloquial usage on this point. Colloquial use also generally doesn't include the adjective 'algal', hence 'algae blooms' in the popular UK press. It depends who you are writing for!

I allways had the same question, but to a differnt occasion.
For exemple, if I wanna say: The microalgae (microalga) Nannochloropsis oculata is ...
Someone knows what is the right form???