dido9

Hello everybody.

There is a question that bothers me. I witnessed a recent discussion about black brush algae - freshwater Rhodophyta species. There was a strange opinion that originated from a russian aquarium plants book by M.B. Cirling "Aquarium and water plants" ( http://www.aquaria.ru/img/bookshell/970144581.jpg ) that black brush algae are mixotrophic species and that they can benefit DOC by a mixotrophic path additionally to the photosynthetical (autothrophic) pathway.

I couldn't find any evidence that Rhodophyta feeds mixotrophic so I'll appreciate your opinion on the topic.

Laith

Sure.... what's mixotrophic??

Maybe if you explained a little bit more what the concept is...

Laith

Okay, for those like me who had no clue, here's Wikipedia's description:

"The term mixotrophic can describe organisms (usually algae or bacteria) capable of deriving metabolic energy both from photosynthesis and from external energy sources. These organisms may use light as an energy source, or may take up organic or inorganic compounds. They may take up simple compounds osmotically (by osmotrophy) or by engulfing particles (by phagocytosis or myzocytosis)."

dido9

Laith, thanks for providing wiki's explanation of 'mixotrophic'.

The question in short is: Are BBAs mixotrophic or not. Or - does BBA feed directly with organic and inorganic compounds from the water.

You have seen eventually that BBA seem to expand quickly if there are organic particles that cover the tufts. That's is probably why Cirling claims it's mixotrophic - because BBA (eventually) gain additional food and energy from dissolved organics around the algae filaments.

In the contrary, I couldn't find absolutely no evidence of that on the web. There are some mixotrophic unicellular species - Euglenas, some bacterias, etc, but they are not common to Rhodophyta phylum. So the whole thing about BBS being mixotrophic seems like a hoax to me. Anyway this question bothers me so I would like to hear some other opinions on the topic.

plantbrain

I'd say both.

But.......this knowledge is not going to help you eradicate it nor control it.
It does just find either way in our tanks, nature is another story entirely.

Regards,
Tom Barr

plantbrain

BTW, you have a reference for that statment in that book?

Eg (Sanders, 1989), (Sheath, 1999) etc specifically?

The species and genus of the red alga in question is critical for the support of such statements.

There is only one species and genus that bothers us, many species do radically different things and have novel pathways.

A deep water marine macro algae might be quite different than a FW stream algae like BBA.

But some authors try and use weak references to support their conclusions without doing observations and testing.

This is a common problem in this hobby.

Regards,
Tom Barr

www.BarrReport.com

dido9

Sorry, there's no reference in the book - p.71 for those who read russian. The author (M.B. Cirling '1991) states mixotrophy for species in the Compsopogon genus.

Reading your post I suppose the one troublesome genus in question is actually Audouinella, not Compsopogon - I don't know what the species are.

Cirling's book is more like a reference guide to hobbyst aquarium plant breeders . This only statement - about BBA mixotropic nature - leads to an improper mystification of BBA's abilities to survive most hobbyst' countermeasures.

plantbrain

Actually Compsopopgon is present in FW aquariums.
Sometimes called staghorn algae.
It's a red alga.
It appears to have the ability for mixtrophy.
I have induced this with a high fish load(progressively adding more and more shrimp till you get algae), initially I got green water, but then I got staghorn soon thereafter.

If I added solely NH4 from organic forms(or PO4+ NH4 etc), I was unable to induce staghorn algae.

I repeated this several times for conformation.
The added organic nutrients appear to help encourage or induces this algae.
This might suggest it has such ability, but it's not particularly significant in our tanks really.

At least it's a FW algae though!
Sheath has a few good references for it, the species is C. coeruleus.
It's found in the USA, Brazil etc and is not temp dependent.
94% of all red FW algae occur in streams and rivers also.

The interaction between pH and DIC greatly influences growth and sporulation of red algae(Sheath and Hambrock, 1990). Most are found at pH 6-7. They are alos found in high O2 levels.

Many red algae are found below the detection limits of PO4.
Thus they have extremely wide variation in nutrient levels.
This as well as the other traits are also found to be true in our tanks.

At least two references for snail herbivory are found and many insects feed on it. 38 critters in all.

Regards,
Tom Barr

dido9

Thanks Tom.

You said "Actually Compsopopgon is present in FW aquariums." And what about those bushy soft black/brown algae - aren't they Audouinella species?

plantbrain

Yes on the BBA genus, the brachy lighter grey nasty stuff is the Compsopogon, the filaments are much larger and there is braching.

Regards,
Tom Barr