Question on photosynthesis data from Dana Riddle articles

[Dana Riddle]

Dana,
is it right that using a light source made only of a narrow spectrum as for 450nm LED, ora maybe ATI actinic t5 tube (not so narrow as LED, but not full spectrum as an aquabluespezial tube) photosynthesis can be saturated as well (I mean reaching maximum ETR, photosynthesis yield)?
And if theory is correct, a blue light is "safer" because there is the energy shunt (in case of excess of light) that lacks for red light?

Sorry if my terms are uncorrect or poor... but I'm trying to detangle myself in a field I only know thank to your articles and in a foreign language.

Thanks.

Luca

Hi Luca,
Sorry for the late reply. Yes, if the intensity of the blue light is intense enough, the accessory or antennae photopigments (chlorophyll a, chlorophyll c2, peridinin, beta-carotene, possibly fucoxanthin) will channel the photons they collect to reaction centers in P-680 and P-700 and photosynthesis will become saturated. Now, the issue is this - I think. The reaction of zooxanthellae to blue light is to increase photopigment content/density, hence more light is collected. If the amount of light collected during the photoperiod (Daily Light Integral) far exceeds what a coral would experience at depths where there is a lot of blue light and little red, is it possible that this unnatural combinations exceeds the natural defenses. I wish I had a better answer, but each question answered asks 10 more questions.

 

[Dana Riddle]

Hi Luca,
Sorry for the late reply. Yes, if the intensity of the blue light is intense enough, the accessory or antennae photopigments (chlorophyll a, chlorophyll c2, peridinin, beta-carotene, possibly fucoxanthin) will channel the photons they collect to reaction centers in P-680 and P-700 and photosynthesis will become saturated. Now, the issue is this - I think. The reaction of zooxanthellae to blue light is to increase photopigment content/density, hence more light is collected. If the amount of light collected during the photoperiod (Daily Light Integral) far exceeds what a coral would experience at depths where there is a lot of blue light and little red, is it possible that this unnatural combinations exceeds the natural defenses. I wish I had a better answer, but each question answered asks 10 more questions.

I'm going to run some calculations and review some old research papers, plus combine it with some work I've done.

 

[ink]

Thanks Dana for answer.
I think my level of knowledge about this topic doesn’t allow me to give some suggestion about collateral effects using a blue light only source.
I’ll wait for updates from You and I’ll updates with short term impressions with my actual light (almost blue and at subsaturating level).

Luca

 

[Dana Riddle]

Thanks Dana for answer.
I think my level of knowledge about this topic doesn’t allow me to give some suggestion about collateral effects using a blue light only source.
I’ll wait for updates from You and I’ll updates with short term impressions with my actual light (almost blue and at subsaturating level).

Luca

Keep me posted please. I can learn a lot from others' experiences.

 

[ink]

A small update.
I've used for two weeks 12 t5 54W tubes (6 ati actinic, 4 blueplus, 2 aquabluespezial) at 45 above water level. Tank is 150x130x65cm. Corals received PPDF ranging from 150 to 250umoles/m2/s (apogee MQ-200, set on sun) for 12 hours.
While polyp expansion remained good, growth visually stopped on most corals (about 90%, tank is sps dominated) and alk level quickly raised.
Nitrate raised to 1ppm (salifert test), while in the past (fixtures lowest as possible) couldn't detect nitrate despite heavy feeding.

Two days ago, I decided to shift then to max light power, using 18 54W T5 aquabluespezial tubes and a 460nm LED bar 70W at minimal height above water. PPFD ranges from 400 to 700umoles. I'm using a shorter photoperiod, about 6 hours. I'm trying regulate it looking at signs of phosynthesis saturation (reduction of polyp expansion, reduction of ph slope increase, or other signs). After a few hours of this light setup, powder-like greenish biofilm appeared on glasses. Water clarity was reduced and was green colored. Corals kept a good polyp expansion without reduction. After the first day, nitrate reduced to 0,2ppm, despite heavy feeding.
Today (second day), after six hours light, tiny bubbles appeared on surfaces. Dana, any explanation for those? oxygen concentration in water was saturated? Could it be a sign of photosynthesis saturation? In my experience, when significant and increasing, it is linked to coral health worsening.
I will update with impressions about this new setup in the next weeks.

Luca

 

[Dana Riddle]

A small update.
I've used for two weeks 12 t5 54W tubes (6 ati actinic, 4 blueplus, 2 aquabluespezial) at 45 above water level. Tank is 150x130x65cm. Corals received PPDF ranging from 150 to 250umoles/m2/s (apogee MQ-200, set on sun) for 12 hours.
While polyp expansion remained good, growth visually stopped on most corals (about 90%, tank is sps dominated) and alk level quickly raised.
Nitrate raised to 1ppm (salifert test), while in the past (fixtures lowest as possible) couldn't detect nitrate despite heavy feeding.

Two days ago, I decided to shift then to max light power, using 18 54W T5 aquabluespezial tubes and a 460nm LED bar 70W at minimal height above water. PPFD ranges from 400 to 700umoles. I'm using a shorter photoperiod, about 6 hours. I'm trying regulate it looking at signs of phosynthesis saturation (reduction of polyp expansion, reduction of ph slope increase, or other signs). After a few hours of this light setup, powder-like greenish biofilm appeared on glasses. Water clarity was reduced and was green colored. Corals kept a good polyp expansion without reduction. After the first day, nitrate reduced to 0,2ppm, despite heavy feeding.
Today (second day), after six hours light, tiny bubbles appeared on surfaces. Dana, any explanation for those? oxygen concentration in water was saturated? Could it be a sign of photosynthesis saturation? In my experience, when significant and increasing, it is linked to coral health worsening.
I will update with impressions about this new setup in the next weeks.

Luca

I'll have to research this quite a bit. Give me a few days to digest the details you've provided.

 

[Dana Riddle]

I'll have to research this quite a bit. Give me a few days to digest the details you've provided.

Apologies for the tardy reply Luca. I would expect polyp expansion to be poor due to self-shading if photosaturation is occurring, but there are contradictions (increase in alkalinity, pH delta)… Was the increase to 400-700 PPFD done suddenly (sounds like it was)? I've seen blooms of nuisance growths (diatoms, dinoflagellates?) when blue light is suddenly and drastically increased.

 

[RevMH]

A small update.
I've used for two weeks 12 t5 54W tubes (6 ati actinic, 4 blueplus, 2 aquabluespezial) at 45 above water level. Tank is 150x130x65cm. Corals received PPDF ranging from 150 to 250umoles/m2/s (apogee MQ-200, set on sun) for 12 hours.
While polyp expansion remained good, growth visually stopped on most corals (about 90%, tank is sps dominated) and alk level quickly raised.
Nitrate raised to 1ppm (salifert test), while in the past (fixtures lowest as possible) couldn't detect nitrate despite heavy feeding.

Two days ago, I decided to shift then to max light power, using 18 54W T5 aquabluespezial tubes and a 460nm LED bar 70W at minimal height above water. PPFD ranges from 400 to 700umoles. I'm using a shorter photoperiod, about 6 hours. I'm trying regulate it looking at signs of phosynthesis saturation (reduction of polyp expansion, reduction of ph slope increase, or other signs). After a few hours of this light setup, powder-like greenish biofilm appeared on glasses. Water clarity was reduced and was green colored. Corals kept a good polyp expansion without reduction. After the first day, nitrate reduced to 0,2ppm, despite heavy feeding.
Today (second day), after six hours light, tiny bubbles appeared on surfaces. Dana, any explanation for those? oxygen concentration in water was saturated? Could it be a sign of photosynthesis saturation? In my experience, when significant and increasing, it is linked to coral health worsening.
I will update with impressions about this new setup in the next weeks.

Luca

Any updates? This was an intensely interesting topic before it seemed to die.

 

[Dana Riddle]

@ink - I get so many messages (email, PMs, Messenger, text, etc.) - Didn't we discuss this privately? Please excuse an old man (me) who has a failing memory. It sounds like the bubbles (nascent oxygen) is being produced by algal growth encouraged by stronger light/spectral shifts. Or am I really off base?

 

[ink]

It's a bit early to take conclusions, but my system seems to work finally. In the past I've tried so many actions, but anything worked. Light increase, light decrease, increase food, increase nitrate/phosphate, change light spectrum, increase/decrease skimming, UV filtration, ozone, organic carbon administering, biopellet, algae filter, algae refugium, mechanical filtration... I can't even remeber all... and in the last 5 years life of this tank I've always struggled fighting bryopsis, w/o success.
Every time I did something to increase nutrients, firstly corals improved, but 3-4 days after, polyps closed and STN/RTN started. Algae were increasing every time I was adding nutrients. In order to decrease bryopsis I had to starve the system, and corals suffered. In the last 5 years, my system alternated between these two states. I have been never able to detect nitrate. Most of aquarist recommend to have nitrate 2-5ppm and I've seen very beautiful and thriving tanks with that nitrate level, but both adding food or directly nitrate, I could only see bryopsis increase as fast as I was adding nitrogen. And no nitrate in the water.
Recently I finally decided to give a try to fluconazole treatment. Now I'm on day 10 of treatment. Bryopsis has nearly completed disappeared. And I have been increasing food since I saw algae reducing and corals are improving day by day.
I repeat, It takes a longer time to have confirm, but my actual thought is that bryopsis made impossible to find a balance. Corals need food, but If I fed in presence of bryopsis, the latter take advantage and I guess it leaches something in the water harming corals. I tried in the past a huge number of antagonist against bryopsis, but nothing could control it.
I'll update.

Luca