Argument against reverse lighting cycle on a refugium

[Randy Holmes-Farley Verified Community Expert]

Can you be more specific?

The word "efficiency" (e.g., photosynthetic efficiency) concerns me if we are extracting data from a scientific paper on photoreactors. I haven't read them all, but they may be very concerned with electricity costs and are looking at optimal "efficient" use of the light, while we are usually more concerned with the total degree or extent of photosynthesis.

For example, photosynthetic efficiency is defined as

https://en.wikipedia.org/wiki/Photosynthetic_efficiency

"The photosynthetic efficiency is the fraction of light energy converted into chemical energy during photosynthesis in plants and algae. "

I personally do not care about that nearly as much as the total photosynthesis per day.

If 24/7 lighting of an ATS or macroalgae refugium has lower photosynthetic efficiency but more total photosynthesis, I might opt for 24/7.

 

[Scrubber_steve]

The word "efficiency" (e.g., photosynthetic efficiency) concerns me if we are extracting data from a scientific paper on photoreactors. I haven't read them all, but they may be very concerned with electricity costs and are looking at optimal "efficient" use of the light, while we are usually more concerned with the total degree or extent of photosynthesis.

For example, photosynthetic efficiency is defined as

https://en.wikipedia.org/wiki/Photosynthetic_efficiency

"The photosynthetic efficiency is the fraction of light energy converted into chemical energy during photosynthesis in plants and algae. "

I personally do not care about that nearly as much as the total photosynthesis per day.

If 24/7 lighting of an ATS or macroalgae refugium has lower photosynthetic efficiency but more total photosynthesis, I might opt for 24/7.

Ok. Is there any evidence to show 24/7 illumination of a macro algae filter will remove more inorganic nutrients over a given period, than when using a day/ night cycle.

 

[chipmunkofdoom2]

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/

This study, as well as the other you cited in your later post, applies only to very specific microalgae species that are particularly useful in biofuel production. This study makes one and only one claim: that Neochloris oleoabundans uses light most efficiently when it is lit 24/7 as opposed to a day/night cycle. This does not suggest or imply that other micro or macro algae species have the same reactions under the same conditions.

I encourage you to read the method section of the paper quoted above. It states that the authors maintained a pH of 7.5 +/- 0.2 by dosing HCl to the reaction chamber, as well as adding an emulsification agent. The authors also maintained a very specific hydration, dissolved oxygen and CO2 concentrations. Any number of these other factors could have influenced the algae's use of light, and it's possible that without one of these very specific factors, the algae would not have used light more efficiently.

Because of the single specie used in the study as well as the very specific testing conditions maintained during the experiment, I don't think it's appropriate to blindly apply the findings from the paper to any of the many algae we typically culture in the hobby. The paper does not claim that all plants or algae use light more efficiently when lit for 24 hours a day. The claim is very specifically that Neochloris oleoabundans does use light most efficiently when lit 24/7.

It's possible that the macroalgae we use could benefit from a 24/7 cycle. But, it's not appropriate to use this paper as the evidence for that claim. A specific study of a specific strain of macro/micro algae from the hobby would need to be done.

 

[Scrubber_steve]

This study, as well as the other you cited in your later post, applies only to very specific microalgae species that are particularly useful in biofuel production. This study makes one and only one claim: that Neochloris oleoabundans uses light most efficiently when it is lit 24/7 as opposed to a day/night cycle. This does not suggest or imply that other micro or macro algae species have the same reactions under the same conditions.

I encourage you to read the method section of the paper quoted above. It states that the authors maintained a pH of 7.5 +/- 0.2 by dosing HCl to the reaction chamber, as well as adding an emulsification agent. The authors also maintained a very specific hydration, dissolved oxygen and CO2 concentrations. Any number of these other factors could have influenced the algae's use of light, and it's possible that without one of these very specific factors, the algae would not have used light more efficiently.

Because of the single specie used in the study as well as the very specific testing conditions maintained during the experiment, I don't think it's appropriate to blindly apply the findings from the paper to any of the many algae we typically culture in the hobby. The paper does not claim that all plants or algae use light more efficiently when lit for 24 hours a day. The claim is very specifically that Neochloris oleoabundans does use light most efficiently when lit 24/7.

It's possible that the macroalgae we use could benefit from a 24/7 cycle. But, it's not appropriate to use this paper as the evidence for that claim. A specific study of a specific strain of macro/micro algae from the hobby would need to be done.

Ok. Is there any evidence to show 24/7 illumination of a macro algae filter will remove more inorganic nutrients over a given period, than when using a day/ night cycle.

 

[Randy Holmes-Farley Verified Community Expert]

Ok. Is there any evidence to show 24/7 illumination of a macro algae filter will remove more inorganic nutrients over a given period, than when using a day/ night cycle.

I've not seen a test of this one way or the other.

 

[Scrubber_steve]

I've not seen a test of this one way or the other.

So in my opinion 24/7 illumination would be a stress on a macroalgae as a dark cycles allows for re-oxidation of the electron transporters of the photosynthetic apparatus.

Algae when put under stress release a far greater percentage of exudates.

 

[Randy Holmes-Farley Verified Community Expert]

So in my opinion 24/7 illumination would be a stress on a macroalgae as a dark cycles allows for re-oxidation of the electron transporters of the photosynthetic apparatus.

Algae when put under stress release a far greater percentage of exudates.

OK, but IME, it made little difference between 24/7 and shorter daily light cycles (say, 12-18 h on). The macroalgae seemed unchanged, but I wasn't quantifying growth. Just eyeballing it.

 

[Randy Holmes-Farley Verified Community Expert]

http://www.fao.org/docrep/003/w3732e/w3732e06.htm#b12-2.3.1.2. Light

"The duration of artificial illumination should be minimum 18 h of light per day, although cultivated phytoplankton develop normally under constant illumination."

 

[MnFish1]

https://www.semanticscholar.org/pap...arbà/f52b83f5a22437a3c82dd06af85b96dea59b559f

 

[Scrubber_steve]

https://www.semanticscholar.org/pap...arbà/f52b83f5a22437a3c82dd06af85b96dea59b559f

Perhaps a make hay while the sun shines evolutionary reaction to kelp living in this zone?

I found the following more useful -

Best Practice Guidelines for Seaweed Cultivation and Analysis
file:///C:/Users/Steve/Downloads/WP1A5%20Macroalgae%20BP.pdf

2.1.1 Hatchery Set-Up
In all three case studies -
Queen’s University Belfast – Marine Laboratory, Portaferry,
CEVA, Pleubian,
& National University of Ireland Galway, Carna Research Station, Co. Galway,
a day/night cycle photoperiod was implemented.


Optimal temperature and photoperiod for cultivation of Agardhiella subulata microplantlets in a bubble-column photobioreactor.
https://www.researchgate.net/public...oplantlets_in_a_bubble-column_photobioreactor

Biomass production was maximized at 16:8 Light/Day, where biomass densities exceeding 3.6 g dry cell mass L(-1) were achieved after 60 days in culture.

Biomass production was proportional to photoperiod at low fractional photoperiods (< or =10:14 LD), but high fractional photoperiods approaching continuous light (> or = 20:4 LD) shut down biomass production.



Optimal conditions for tissue growth and branch induction of Gracilariopsis persica
file:///C:/Users/Steve/Downloads/IFRO-v12n1p24-en.pdf

The seaweed Gracilariopsis persica showed the highest growth rates on a 12 h L: 12 h D cycle

This one is interesting as it includes a species of ulva, not the same as what grows on my scrubber screen, but ulva non the less.

Growth rates of North Sea macroalgae in relation to temperature, irradiance and photoperiod
https://hmr.biomedcentral.com/track/pdf/10.1007/BF01983538?site=hmr.biomedcentral.com

Three eulittoral algae (Ulva lactuca, Porphyra umbilicalis, Chondrus crispus) and one sublittoral alga (Laminaria saccharina) from Helgoland (North Sea) were cultivated in a flowthrough system at different temperatures, irradiances and day lengths.

Growth rate increased continuously up to photoperiods of 24 h light per day in L. saccharina and C. crispus, whereas day length saturation occurred at photoperiods of more than 16 h light per day in Ulva. lactuca and P. umbilicalis.

This graph from the paper shows how the rate of biomass production for Ulva lactuca & Porphyra umbilicalis slows considerably at 16 hours.
This is in a 24 hour period, so, production would be severely affected if illumination was to continue on continuously.

You can run a 24/7 photoperiod if you choose, but for most macroalgaes the effect on the rate of biomass production would be negative - less fixation of co2 to o2, less inorganic nutrient uptake, over a 24 hour period,

 

[Randy Holmes-Farley Verified Community Expert]

I'm confused. Your graph posted above shows 24/7 for macroalgae is best 3 out of 4 cases, and equal to best on the other.

 

[Rcpilot]

My head just literally exploded!!!!!!!!;Wacky

Clean up on post #23!!
Clean up please!!

 

[Scrubber_steve]

I'm confused. Your graph posted above shows 24/7 for macroalgae is best 3 out of 4 cases, and equal to best on the other.

Well I'm confused. The authors state -
"Continuous light provided best growth in Chondrus crispus as well as in Laminaria saccharina.
However, for several other algae daylength saturation is known to occur, as was the case in Ulva
lactuca and Porphyra umbilicalis for which the growth rate did not increase at daylengths longer than 16 h light per day."

Take the ulva; it had on average a specific growth rate percentage increase of around 5.5% for each 4 hour period up to 16 hours.
But, for the next two 4 hour periods - 16 to 24 hours, growth rate fell dramatically to 0.5% per 4 hour period, & this would be the average rate of growth for every 4 hour period going forward if illumination continued on, 24/7.

If, however, illumination was ceased for the period 16 to 24 hours, & then resumed, the growth rate would resume at an average of 5.5% per 4 hour period, up to 16 hours of illumination, giving an average growth rate of 3.75% per 4 hour period over a 24 hour period.

So If I had that ulva growing on my scrubber screen, & I wanted maximum efficiency in regards of nutrient export & carbon fixation, I would run a light/dark cycle of 16/8.

 

[oceanrider]

Probably in reality. Each species of plant. Algae or even each different plant within a species. May react differently to different photo periods Depending on nutrients, ph. Temp. Etc.

I can see how micro algae which has shorter lifespans and less complicated internal systems. May benefit from continuous lighting.

But in my opinion other macro algae , will vary in terms of reaction to extreme lighting

 

[oceanrider]

To be honest you guys post great hypothetical situations.

Back when I was studying marine biology. The algae class was mainly lecture about morphology of diff algae’s. And lab was 3 hrs long of looking into microscope to see each cell. See the seeds. Pods. Different phases of algae Etc. But not one minute was devoted to culturing or measuring parameters that affected growth.

 

[MnFish1]

Well I'm confused. The authors state -
"Continuous light provided best growth in Chondrus crispus as well as in Laminaria saccharina.
However, for several other algae daylength saturation is known to occur, as was the case in Ulva
lactuca and Porphyra umbilicalis for which the growth rate did not increase at daylengths longer than 16 h light per day."

Take the ulva; it had on average a specific growth rate percentage increase of around 5.5% for each 4 hour period up to 16 hours.
But, for the next two 4 hour periods - 16 to 24 hours, growth rate fell dramatically to 0.5% per 4 hour period, & this would be the average rate of growth for every 4 hour period going forward if illumination continued on, 24/7.

If, however, illumination was ceased for the period 16 to 24 hours, & then resumed, the growth rate would resume at an average of 5.5% per 4 hour period, up to 16 hours of illumination, giving an average growth rate of 3.75% per 4 hour period over a 24 hour period.

So If I had that ulva growing on my scrubber screen, & I wanted maximum efficiency in regards of nutrient export & carbon fixation, I would run a light/dark cycle of 16/8.

You really confuse me. You stated that you use 24/7 light on your refugium. LOL

You misinterpret the graphs the you posted IMHO. Its not about 'rate of growth' its about 'growth'. Since the data you show doesn't show that growth slows after 24 hours of continuous light, you can make no conclusion.

As I said before - its likely species specific. Lots of articles suggest (if not a benefit) no detrimental effect to a 24 hour light cycle. So - IDK. but - Im leaving mine the way it is - Out competing algae in the tank during the day - and improving chemistries at night (IMHO)

 

[Scrubber_steve]

You really confuse me. You stated that you use 24/7 light on your refugium. LOL

LOL, I don't even have a refugium. I said "I have algae illuminated 24/7 in my tank." & "I have two seperate screens". I have a scrubber, & I have two screens, each illuminated seperately, & neither illuminated for 24 hours.

You misinterpret the graphs the you posted IMHO. Its not about 'rate of growth' its about 'growth'. Since the data you show doesn't show that growth slows after 24 hours of continuous light, you can make no conclusion.

LOL, the growth rate of Ulva lactuca and Porphyra umbilicalis does slow down significantly after 16 hours of illumination, its shows this plainly in the graph, & the authors state "in the case in Ulva lactuca and Porphyra umbilicalis for which the growth rate did not increase at daylengths longer than 16 h light per day." So illuminating either of them for 8 hours longer, is, at the very least, a waste of electricity. This is most likely the logic for a light/dark cycle being employed at the algae Hatchery Set-Ups previously mentioned.

As I said before - its likely species specific. Lots of articles suggest (if not a benefit) no detrimental effect to a 24 hour light cycle. So - IDK.
but - Im leaving mine the way it is - Out competing algae in the tank during the day - and improving chemistries at night (IMHO)

No detriment? OK, so consider Porphyra umbilicalis, specifically. It gained zero "area increase" from being illuminated for longer than 16 hours over a 24 hour period. What if being continuously illuminated stresses it?
Algae release a far higher percentage of their primary production into the water (exudates) when under stress. Bacteria would consume the exudates & oxygen at the same time. Could this be counter intuitive when attempting to oxygenate the water? Just a thought.

Anyway, yes, some algae are happy with 24/7 illumination, with some its a waste of electricity, & some others no doubt would be stressed.

 

[MnFish1]

LOL, I don't even have a refugium. I said "I have algae illuminated 24/7 in my tank." & "I have two seperate screens". I have a scrubber, & I have two screens, each illuminated seperately, & neither illuminated for 24 hours.


LOL, the growth rate of Ulva lactuca and Porphyra umbilicalis does slow down significantly after 16 hours of illumination, its shows this plainly in the graph, & the authors state "in the case in Ulva lactuca and Porphyra umbilicalis for which the growth rate did not increase at daylengths longer than 16 h light per day." So illuminating either of them for 8 hours longer, is, at the very least, a waste of electricity. This is most likely the logic for a light/dark cycle being employed at the algae Hatchery Set-Ups previously mentioned.


No detriment? OK, so consider Porphyra umbilicalis, specifically. It gained zero "area increase" from being illuminated for longer than 16 hours over a 24 hour period. What if being continuously illuminated stresses it?
Algae release a far higher percentage of their primary production into the water (exudates) when under stress. Bacteria would consume the exudates & oxygen at the same time. Could this be counter intuitive when attempting to oxygenate the water? Just a thought.

Anyway, yes, some algae are happy with 24/7 illumination, with some its a waste of electricity, & some others no doubt would be stressed.

So - here is the problem with your graphs. There is nothing shown for what happens after 24 hours. It seems obvious that over time the growth rate of ANYTHING slows. If you charted the growth rate of a human from birth to death the curve would look similar. It doesn't imply or mean that there is any 'stress'. Using your graphs showing growth rate - if they continued on for 3 days - and the algae started dying, etc that would suggest a detrimental effect. At this point I don't see a relationship to the topic we're discussing.

It seems completely intuitive that algae growth rates increase and decrease when light increases and decreases.

If the total amount of macro algae is increasing - then even if the growth rate is slowing it may make no difference (and probably does not). There is lots of evidence that algae can be stressed as the INTENSITY of light is increased over a certain amount. There is not as much evidence (at all) as to the duration.

As to the LOL about you not having a refugium - LOL - your original post 'I have algae illuminated 24/7 in my tank.' seems a little lacking in explanation. Sorry I assumed you had a refugium. Also sorry that I assumed that you had 2 places you put algae. LOL

 

[Scrubber_steve]

So - here is the problem with your graphs. There is nothing shown for what happens after 24 hours. It seems obvious that over time the growth rate of ANYTHING slows. If you charted the growth rate of a human from birth to death the curve would look similar. It doesn't imply or mean that there is any 'stress'. Using your graphs showing growth rate - if they continued on for 3 days - and the algae started dying, etc that would suggest a detrimental effect. At this point I don't see a relationship to the topic we're discussing.

It seems completely intuitive that algae growth rates increase and decrease when light increases and decreases.

If the total amount of macro algae is increasing - then even if the growth rate is slowing it may make no difference (and probably does not). There is lots of evidence that algae can be stressed as the INTENSITY of light is increased over a certain amount. There is not as much evidence (at all) as to the duration.

As I stated in post #63 "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."
The macro algaes used for filtration in reef tanks have typically evolved in tropical, or at least sub tropical areas (not in arctic areas with 24/7 light for a few months of the year). Water temperature & light intensity affect their productivity & can stress them to death if too far from ideal. So IMO blasting these algae with 24/7 light may or may not kill them, but there is no reason to assume that it would be benificial. As in the case of Ulva lactuca and Porphyra umbilicalis, illuminating them longer than 16 hours is just wasting electricity at the very least, & possibly stressful.

If lighting 24/7 is benificial that would be great. So if you can post a link to a paper that shows increased photosynthetic production by fast metabolising macro algae, as a consequence of applying a 24/7 illumination, over an indefinate period, that would be great.

As to the LOL about you not having a refugium - LOL - your original post 'I have algae illuminated 24/7 in my tank.' seems a little lacking in explanation. Sorry I assumed you had a refugium. Also sorry that I assumed that you had 2 places you put algae. LOL

There was no need to assume that I "had 2 places I put algae". I posted I had two screens here, & you responded to it here.
LOL, no need to apologise.

Just to end this conversation; growing a fast metabolising algae is the best way to aerate an aquarium, & to convert CO2 to O2. As Eric Borneman found in his tests "Aquaria can and do become saturated or supersaturated with oxygen during the day, and this is a result of oxygen resulting from irradiance of photosynthetic organisms. In no case was saturation or supersaturation measured without photosynthesis."

Illuminating the algae when the tank lights go out is especially important.

 

[MnFish1]

As I stated in post #63 "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."
The macro algaes used for filtration in reef tanks have typically evolved in tropical, or at least sub tropical areas (not in arctic areas with 24/7 light for a few months of the year). Water temperature & light intensity affect their productivity & can stress them to death if too far from ideal. So IMO blasting these algae with 24/7 light may or may not kill them, but there is no reason to assume that it would be benificial. As in the case of Ulva lactuca and Porphyra umbilicalis, illuminating them longer than 16 hours is just wasting electricity at the very least, & possibly stressful.

If lighting 24/7 is benificial that would be great. So if you can post a link to a paper that shows increased photosynthetic production by fast metabolising macro algae, as a consequence of applying a 24/7 illumination, over an indefinate period, that would be great.


There was no need to assume that I "had 2 places I put algae". I posted I had two screens here, & you responded to it here.
LOL, no need to apologise.

Just to end this conversation; growing a fast metabolising algae is the best way to aerate an aquarium, & to convert CO2 to O2. As Eric Borneman found in his tests "Aquaria can and do become saturated or supersaturated with oxygen during the day, and this is a result of oxygen resulting from irradiance of photosynthetic organisms. In no case was saturation or supersaturation measured without photosynthesis."

Illuminating the algae when the tank lights go out is especially important.

Not to respond to it *** for tat so to speak - the vast majority of readers here (myself included) have no clue what 2 screens means.

Again - to repeat - If the amount of algae increases - the amount of photosynthesis increases - independent of the 'growth rate'. Instead of asking new questions - why dont you respond to mine lol.

Lastly - in the tropics - there is no 24 hour daylight cycle - that doesn't mean it wouldn't be beneficial or at least - non detrimental.