Why does dying algae fluoresce?

[Ghost25]

A rather technical question but I've noticed when red algaes like Coraline or Gracillaria are exposed to air for a while they become brightly fluorescent and die.

Any theories on why? I've searched scientific literature and perhaps not surprisingly this is not something that has received much study.

 

[Subsea]

First off, Gracilaria is green and it will not florescense.

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RED MACROALGAE (RHODOPHYTA)​

The genus Rhodophyta is the largest and most diverse group of tropical and temperate marine algae with more than 2,000 species worldwide. Their dominant pigment is phycoerythrin, which gives off rich shades of red, orange and blue. Red macro algae are some of the most varied and striking of all marine algae and are highly sought after as aquarium specimens. Identification can be difficult in some species and some have slight variations depending on the location and depth. Although this index is not a complete listing, it represents species that are commonly

I suggest research pigment phycoerythrin.

 

[TokenReefer]

I would venture to guess your lighting has a lot to do with it.

 

[Diastro]

This a great question. I wish I knew the answer. I have a macroalgae that fluoresces completely yet it is not dying, it is dragon's tongue. Not sure if any others do aswell.

 

[Subsea]

Generic names confuse the question. Dragons tongue or dragons breath is confusing. Halymenia fluorescence’s with intense light. Not the same process as dying pigment phycoerythrin.

Fluorescence is a two-stage chemical process involving absorption of shorter-wavelength light by a chemical fluorophore such as a protein or carotenoid (excitation), followed by the release of some of the absorbed energy as longer-wavelength light (emission).

@Diastro
Is this what you have?

Halymenia durvillei (Dragons Breath)​

This is a Pacific variety that is aqua-cultured in the United States. Unlike other species of halymenia, the tissue on this particular macro algae isn't as thin and is slightly rigid. It features a deep red coloration and a brilliant orange-yellow fluorescence at the tip of each frond. It's a very hardy species once established but grows in cycles so should be divided regularly to preserve the algae.

 

[Ghost25]

First off, Gracilaria is green and it will not florescense.

No, it's red. https://en.wikipedia.org/wiki/Gracilaria and it absolutely does fluoresce if you expose it to air for a few minutes and let it dry out a bit and rewet it.

Here's the phenomenon I'm talking about. This is my MP10 powerhead with Coralline algae immediately after being removed from the water, no fluorescence:

Here is the same powerhead about 10 minutes later after being allowed to dry in air, then briefly rewet:

The same phenomena occurs with red algae like Gracilaria. Something clearly changes when the algae becomes desiccated and rewet. Maybe some cells are destroyed and previously isolated molecules are oxidized.

 

[Diastro]

Generic names confuse the question. Dragons tongue or dragons breath is confusing. Halymenia fluorescence’s with intense light. Not the same process as dying pigment phycoerythrin.

Fluorescence is a two-stage chemical process involving absorption of shorter-wavelength light by a chemical fluorophore such as a protein or carotenoid (excitation), followed by the release of some of the absorbed energy as longer-wavelength light (emission).

@Diastro
Is this what you have?

Halymenia durvillei (Dragons Breath)​

This is a Pacific variety that is aqua-cultured in the United States. Unlike other species of halymenia, the tissue on this particular macro algae isn't as thin and is slightly rigid. It features a deep red coloration and a brilliant orange-yellow fluorescence at the tip of each frond. It's a very hardy species once established but grows in cycles so should be divided regularly to preserve the algae.

I want to say yes, it looks very similar. I bought it only under a generic name though, that's the problem with macroalgaes, the scientific names aren't common. Just trade names which does make everything confusing.

The whole macroalgae chunk fluoresces though, not just the tips. Perhaps it's because it's still on the smaller size.

 

[taricha]

It has to do with how phycoerythrin containing algae (red algae) breaks down..

yes. phycoerythrin is an accessory pigment and normally does a handoff of energy from phycoerythrin through other pigments to chl a in an intact phycobilisome

now imagine in a dead cell or otherwise damaged phycobilisome, the coupling between phycoerythrin and the other pigments is broken. So instead of handing off that energy down the chain, it fluoresces at ~570nm and longer which looks orange.

you can see this by putting a little vinegar on some coralline algae...




maybe, but probably not. it might just generate more sunscreen pigments (carotenoids or similar). Also photosynthetic organisms have ways of turning down their photosynthetic machinery when the light is too high. This might change the look.

here's a link to the whole post - some bits don't quote.
https://www.reef2reef.com/threads/when-macros-glow-questions-on-red-macroalgae.926561/post-10448486

 

[SFREEF3R]

A rather technical question but I've noticed when red algaes like Coraline or Gracillaria are exposed to air for a while they become brightly fluorescent and die.

Any theories on why? I've searched scientific literature and perhaps not surprisingly this is not something that has received much study.

I had noticed the same thing and wondered why! Thanks for asking the question

 

[Ghost25]

It has to do with how phycoerythrin containing algae (red algae) breaks down..




here's a link to the whole post - some bits don't quote.
https://www.reef2reef.com/threads/when-macros-glow-questions-on-red-macroalgae.926561/post-10448486

That makes sense. So in the damaged algae somewhere along the chain accessory pigments can no longer effectively transfer photons to chlorophyll.

I just got a near UV flashlight and noticed dead plant leaves and dead section of plant leaves also fluoresce more than healthy leaves. Presumably a similar mechanism where accessory pigments like xanthophylls are decoupled from chlorophyll.