Talk:Algae

This article was the subject of a Wiki Education Foundation-supported course assignment, between 5 January 2022 and 4 April 2022. Further details are available on the course page. Student editor(s): Osad3840 (article contribs).

Another issue

We should remember that algae are specifically capable of performing oxygenic photosynthesis, which excludes anoxygenic photosynthesis seen in purple bacteria and other prokaryotes. — Snoteleks (talk) 13:06, 19 May 2025 (UTC)

alga /ælɡə/ ⓘ AL-gə) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not land plants, and includes species from multiple distinct clades. Alga should be algae in sentence two Nico askew (talk) 17:52, 5 October 2025 (UTC)

Section reorganization

The article is difficult to read as the information is often displayed all over the place, and there is little cohesion. I'm going to try to reorganize it over the following days into something similar to this scheme:

1. Etymology and study
2. Description (intro would be the definition of algae, as in the "Classification" section)
   1. Morphology
   2. Nutrition (new)
   3. Physiology (osmorregulation, etc.)
   4. Life cycle
3. Diversity (new; merge of "Number" + "Classification" sections)
   1. Cyanobacteria
   2. Eukaryotic algae
      1. Primary plastid algae
      2. Secondary plastid algae
4. Evolution
   1. Origin of oxygenic photosynthesis (new, essentially origin of cyanobacteria)
   2. First endosymbiosis (new)
   3. Serial endosymbioses (new)
   4. Relationship to land plants
   5. Plastid losses (new)
5. Ecology
   1. Primary production
   2. Biogeochemical cycles
   3. Symbiotic algae
6. In human culture (new, as the present paragraph is completely uncited)
7. Cultivation
8. Use
   1. Biofuel (=energy source)
   2. Fertilizer
   3. Food industry (actual food, pigments, stabilizers)
   4. Gelling agents (agar, alginate)
   5. Bioremediation and pollution control
   6. Bioplastic (=polymers)

— Snoteleks (talk) 19:14, 20 May 2025 (UTC)

I will also add a Distribution section which can house the awkward "local estimates" paragraphs from the current "Numbers" section. — Snoteleks (talk) 19:16, 20 May 2025 (UTC)

Multiple and serial endosymbiosis

@User:Snoteleks Multiple and serial endosymbiosis are different terms. The more common term multiple endosymbiosis of a plastid is an endosymbiosis of an alga which has the plastid from the endosymbiosis of another alga. Serial endosymbiosis is specific and means that the ancestral plastid has been lost and replaced by another one in an act of endosymbiosis of another algae (the ochrophyte plastid was replaced in some dinoflagellates by other plastids, e.g. from cryptophytes, other ochrophytes, haptophytes, or green algae - the example is the green plastid in Lepidodinium).

So, be careful with the "serial endosymbiosis" application. Petr Karel (talk) 08:40, 21 May 2025 (UTC)

@Petr Karel Oh! Thank you for bringing this to my attention, I wasn't aware. I will use the more accurate terminology. — Snoteleks (talk) 10:32, 21 May 2025 (UTC)

Chlorarachniophyta

@User:Snoteleks Chlorarachniophyta are included in the AlgaeBase, but not as phylum. Class Chlorarachniophyceae (with 20 species) is included into phylum Cercozoa. In the same phylum the three Paulinella species are listed which perform the oxygenic photosynthesis (P. chromatophora, P. micropora and P. longichromatophora) with plastids with very specific origin, independent of all other chloroplasts. Are you sure, that all these algae were "omitted" (as written in the note)? Are their numbers not included in the last row with the strange name "Incertae sedis etc." (what etc. means?) Petr Karel (talk) 15:13, 22 May 2025 (UTC)

@Petr Karel I haven't considered that possibility. I'll go check that. — Snoteleks (talk) 15:36, 22 May 2025 (UTC)

@Petr Karel Hey, so I took a look and the situation is very weird. Within the 2024 paper there are a lot of inconsistencies between Table 1 with all the phyla and the individual phylum tables (e.g., Charophyta has 5644 total described species and 4940 living species in Table 1, but 5583 and 4879 in Table 3). The "Incertae sedis etc." row is never mentioned in the text, so there is no way to know what the author included as those.

Judging by the number of species (2995), it could be that all protozoa listed in AlgaeBase are counted in this row, since a lot of Rhizaria appear in the database down to species level, not just Paulinella or chlorarachniophytes.

It could also be that only truly incertae sedis taxa are listed here, as it is unknown whether they belong to one algal phylum or another, or even if they are really algae (e.g., the fossil Chisibyllites kerguelensis, listed as Retaria incertae sedis). This would be consistent with Table 8 in the 2024 paper, where the 2995 species are listed as belonging to kingdom "Incertae" instead of any combination of the four other kingdoms.

Another possibility is that Incertae sedis in that table only refers to fossil taxa, since the "living species" column is empty for this row; only the "species" column is filled with a number.

It's honestly impossible to know for certain, and the numbers themselves are not as reliable as it seemed considering their variation between tables. Either we assume that "Incertae sedis etc." are just fossil taxa, or we assume that it's wrongly classifying protozoa as algae, and therefore we should probably find better references for each phylum instead. — Snoteleks (talk) 17:09, 22 May 2025 (UTC)

@Petr Karel Nevermind, the answer was in table 8 all along. It explicitly divides all species by kingdom into fossil and living, and the 2995 species listed as kingdom "Incertae" are all under the "Fossil" column. Chlorarachniophytes cannot be included here, because they are all living species. — Snoteleks (talk) 17:10, 22 May 2025 (UTC)

Am I looking in the same place (here)? I see 2995 incertae species with 2475 fossil and no entry under living.  —  Jts1882 | talk  17:31, 22 May 2025 (UTC)

@Jts1882 Oh huh, you're right, it says 2475 fossils and no living species, despite the total being larger. This is getting even stranger. I honestly don't know what to make of it, but I personally prefer to assume that chlorarachniophytes are not included until proven otherwise. — Snoteleks (talk) 22:06, 22 May 2025 (UTC)

If you check the counts in table 8 there are errors. The species total column underestimates the fossil+living count for the four kingdoms. The missing species number is the same as the extra 520 in the incertae sedis species total. It's as if some living species are assign to kingdoms for living column but are incertae sedis in the total species columm. The totals for the species total column and the summed fossil and living columns are the same (61145). Not sure this helps the main question.  —  Jts1882 | talk  14:05, 24 May 2025 (UTC)

Well, if anything, it helps knowing that the paper is not very reliable. I'm sure they're still a good approximation, but ideally we should use more accurate ones. I don't even know how Michael Guiry got those numbers in the first place; he runs AlgaeBase, so perhaps he has an algorithm that displays the number of entries automatically for him according to kingdom, phylum and order, but I don't know of any method to do the same as a user. — Snoteleks (talk) 01:12, 25 May 2025 (UTC)

Pronunciation in British English

I am writing this in case my edit to the British pronunciation is challenged. I remember hearing "AL-jee" in the 1964 film Children of the Damned uttered in Received pronunciation which is the standard British accent. I have heard "AL-ghee" in real life but this led me to check some editions of the Oxford English Dictionary, whose pronunciation guide is based on RP although they do occasionally include other common pronunciations, from the 2000s and they recognise "AL-jee" as the primary pronunciation which has led to my decision to edit this article based on the use of "UK also" in Amsterdam.Tk420 (talk) 18:51, 12 August 2025 (UTC)

Well, I'm British and I would say that although the general public may use "j" in my experience biologists use the hard g. This is also consistent with the singular: "alga" always has hard g, so it's odd to change in the plural. Peter coxhead (talk) 21:55, 12 August 2025 (UTC)

Are there plant algae?

"Algae ... is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants ..."

ChatGPT: Yeah, that line on Wikipedia is a bit misleading if you read it literally. It’s trying to capture the informal usage: Botanists often say “plants” = land plants only (embryophytes). Under that definition, algae are not plants. Phylogenetically though, green algae and red algae are in the same clade (Archaeplastida) as land plants, so many biologists do include them in the kingdom Plantae (just not “land plants”). So the tension is: Everyday/Informal definition → “Algae = photosynthetic organisms that aren’t ‘real’ plants (the land ones).” Modern taxonomy → Some algae are Plantae (green & red algae), some are Chromista, some are Protists, some are Bacteria.

https://en.wikipedia.org/wiki/Chlamydomonas Chlamydomonas ... is a genus of green algae Kingdom: Plantae Darsie42 (talk) 08:54, 9 September 2025 (UTC)

That is not good. It does link to the plant article which describes the different usage of the term plant, which does include being restricted to land plants. I think changing the lede to say land plants would be correct. The ChatGTP answer isn't entirely correct either as it's not just a informal versus formal difference.  —  Jts1882 | talk  09:14, 9 September 2025 (UTC)

@Darsie42 There is a strong tendency among certain biologists to group algae with land plants and call them plants, but there is no biological basis for this. It's just a relic from when all plant-like organisms (even fungi) were considered plants. Nowadays, Kingdom Plantae has a more reduced usage, but it is still equivalent to Archaeplastida, a group containing at the very least red algae, glaucophytes, and green algae. Green algae are the closest relatives of plants, so some people group them as "green plants". The concept of "plant", as you might already be seeing, is very vague and can be stricter or more inclusive depending on the author. Therefore it is absolutely true that some algae are still considered plants today. — Snoteleks (talk) 12:02, 9 September 2025 (UTC)