Argument against reverse lighting cycle on a refugium

[MnFish1]

Not exactly. I have two seperate screens. It would be over a 24 hour period

"In two of the species (S. costatum and E. huxleyi), but not the third, the contribution of bicarbonate to the total carbon uptake increased dramatically in light/dark cycles compared to continuous light."

Im not sure that quote answers the question I was asking. But in any case - even in this study it only affected 2/3 of 'micro algae' - not macro algae. So I guess the jury is 'still out'

 

[Scrubber_steve]

@MnFish1
http://reefkeeping.com/issues/2006-10/rhf/index.php#13

 

[Scrubber_steve]

Im not sure that quote answers the question I was asking. But in any case - even in this study it only affected 2/3 of 'micro algae' - not macro algae. So I guess the jury is 'still out'

Plants for the most part have evolved in a day/night cycle. To me it seems logical that their uptake of carbon would be more efficient in this environment.

 

[MnFish1]

Plants for the most part have evolved in a day/night cycle. To me it seems logical that their uptake of carbon would be more efficient in this environment.

Some plants are exposed to light nearly 24 hours a day - during various parts of the year (in the northern hemispheres). Its pretty well documented (logic or not) - that the effects of light on photosynthesis/growth are species specific. Most plants do as well or better - with 24/7 lighting as compared to a dark cycle. Some require a photoperiod to flower and grow properly.

I still dont understand the article Randy wrote - suggesting that putting the refugium on a night light cycle 'may' be beneficial to macro algae (but he wasn't doing it himself:). And a quote from another article by Randy in this thread - "I should note I just searched and found this that Randy posted in another forum (I am not posting the link as it is another forum). This was two years after the above article I posted and feel I should mention it to be complete: What functions are you referring to? The observation by lots of people is that many species of macroalgae thrive under 24/7 lighting. Exactly what biochemical changes this might entail isn't clear from hobby experiments, but I will point out that many photosynthesizing organisms live in 24/7 sunlight, such as in high latitude summertime. ”"

 

[jason2459]

Please keep in mind most all algae are not plants...

 

[MnFish1]

Please keep in mind most all algae are not plants...

Agreed - what is your point?

Algae doesn't deplete oxygen but just the opposite. Bacteria however could.

And pH is directly related to CO2 not Oxygen levels. So, again the algae would help there in consuming CO2.

When it's dark - and depending on the amount of algae present - it can oxygen can be depleted:

When a dense bloom produces a surplus of oxygen on a summer afternoon, the oxygen will not stay in solution and escapes into the atmosphere. During the night, the bloom attempts to take more oxygen out of the water than what remains from daytime photosynthesis. When this occurs, dissolved oxygen levels approach zero.

 

[Scrubber_steve]

The influence of day/night cycles on biomass yield and composition of Neochloris oleoabundans
Conclusions
Microalgae cultures of N. oleoabundans that were synchronized by day/night cycles were able to use the light provided 10–15% more efficiently than cultures grown under continuous light.
In other words, the net efficiency of light usage varies over the cell cycle and the ability to schedule cell division during the night provides a fitness benefit to microalgae.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5401387/

 

[jason2459]

Agreed - what is your point?

To clarify as the term plant keeps popping up. Same as I needed to post a clarification to my post you quoted.

 

[Scrubber_steve]

Adjusted Light and Dark Cycles Can Optimize Photosynthetic Efficiency in Algae Growing in Photobioreactors
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0038975

Abstract
Biofuels from algae are highly interesting as renewable energy sources to replace, at least partially, fossil fuels, but great research efforts are still needed to optimize growth parameters to develop competitive large-scale cultivation systems. One factor with a seminal influence on productivity is light availability. Light energy fully supports algal growth, but it leads to oxidative stress if illumination is in excess. In this work, the influence of light intensity on the growth and lipid productivity of Nannochloropsis salina was investigated in a flat-bed photobioreactor designed to minimize cells self-shading. The influence of various light intensities was studied with both continuous illumination and alternation of light and dark cycles at various frequencies, which mimic illumination variations in a photobioreactor due to mixing.

Results show that Nannochloropsis can efficiently exploit even very intense light, provided that dark cycles occur to allow for re-oxidation of the electron transporters of the photosynthetic apparatus.
If alternation of light and dark is not optimal, algae undergo radiation damage and photosynthetic productivity is greatly reduced.
Our results demonstrate that, in a photobioreactor for the cultivation of algae, optimizing mixing is essential in order to ensure that the algae exploit light energy efficiently.

 

[MnFish1]

The influence of day/night cycles on biomass yield and composition of Neochloris oleoabundans
Conclusions
Microalgae cultures of N. oleoabundans that were synchronized by day/night cycles were able to use the light provided 10–15% more efficiently than cultures grown under continuous light.
In other words, the net efficiency of light usage varies over the cell cycle and the ability to schedule cell division during the night provides a fitness benefit to microalgae.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5401387/

LOL - and they are micro algae not macro algae. In a later post as I quoted - Randy said many people use 24/7 refugium lighting successfully (and he was doing the same) - that's what I didnt understand, i.e. what Randy really thought. As I said - its species specific. In the other article 2/3 species benefited. Looking at Macroalgae reactors - its recommended to maximize growth - to set at 12 hours on - starting at dark - FWIW.

 

[Scrubber_steve]

LOL - and they are micro algae not macro algae.

I see. So to push your argument you propose that the photosynthetic mechanisms for micro & macro algaes are completely different.

 

[Randy Holmes-Farley Verified Community Expert]

How low - and why? I thought this was discussed before - that there was no real difference in coral growth as long as the pH rose above 8.2 during the day. Though it may 'even out' the pH swing, during the day - the algae (not lit) will be net producers of CO2 - which will tend to lower the pH. (I personally leave my macro-algae lit all the time) - in the hopes of having a higher pH during the day - and a higher pH during the night. The 'swing' doesnt seem to harm anything (IMHO)

Yes, there was one study that suggested part of the time at higher pH is good enough. Is that that study correct? Is it the same for every organisms we keep?

Many studies show that calcification is less at lower pH.

I think it is fair to assume until shown otherwise, that lower pH is likely less desirable. :)

 

[MnFish1]

I see. So to push your argument you propose that the photosynthetic mechanisms for micro & macro algaes are completely different.

No - I said - as many articles do - that many plants thrive with 24/7 photo synthesis so it seems species specific. I also said - that at least with the macro algae reactors that I looked at they recommend that the algae reactor (light) be on at night and off during the day.

Having said that - people here seem to believe that the photosynthetic mechanisms for plants and algae are completely different.

 

[MnFish1]

Yes, there was one study that suggested part of the time at higher pH is good enough. Is that that study correct? Is it the same for every organisms we keep?

Many studies show that calcification is less at lower pH.

I think it is fair to assume until shown otherwise, that lower pH is likely less desirable. :)

Thanks Randy - Here is my rationale for leaving my light on my macro algae 24/7.

During the day - if the refugium light is off - algae in the tank has more opportunity to grow/use nutrients than if it is on.
Keeping the light on 24/7 would seem to raise pH during the whole time it is on. As compared to leaving it on at night (raises pH) and off during the day (relatively lower pH) - while this minimizes the 'swing', does it benefit?
As to the study being correct or not - I have no clue... My guess is that it depends on the coral species studied (as you suggest)

 

[Scrubber_steve]

many plants thrive with 24/7 photo synthesis so it seems species specific.

Can you post a link to a paper that shows increased photosynthetic efficiency by macro algae due to 24/7 illumination

 

[Scrubber_steve]

Coral tricks for adapting to ocean acidification

 

[Randy Holmes-Farley Verified Community Expert]

Can you post a link to a paper that shows increased photosynthetic efficiency by macro algae due to 24/7 illumination

Is "efficiency" the question? What about total photosynthesis over 24 h?

 

[Scrubber_steve]

Is "efficiency" the question? What about total photosynthesis over 24 h?

Carbon fixation, inorganic nutrient removal.

 

[Randy Holmes-Farley Verified Community Expert]

Carbon fixation, inorganic nutrient removal.

If that is defined total over 24 h with a light level that reefers typically use, I agree. If that is per unit (photons) of light used, no. :)

 

[Scrubber_steve]

If that is defined total over 24 h with a light level that reefers typically use, I agree. If that is per unit (photons) of light used, no. :)

Can you be more specific?