Individual LED wattage Research

[oreo54]

Compounding all of this is the actual light field inside a coral is not equiv to the light field outside the coral.

It has always been...complicated.

 

[oreo54]

Sorry, seperating this out a bit for clarity
Afaict most ( or common) pcp complexes have a 4:1 ( varies by species) ratio of per to chl a.
So is your quantum yield based one one or the complex as a whole?
https://www.researchgate.net/profil...P-complexes-a-Room-temperature-absorption.pngHeck just throw iron in the equation .
For interest only, not pertaining to this discussion
https://www.pnas.org/doi/10.1073/pnas.0705006105

The water soluble light-harvesting complex of dinoflagellates, peridinin-chlorophyll protein (PCP), is remarkable in using the relatively polar carotenoid peridinin as its main chromophore

Discount it at your own risk I guess

 

[Hurricane Aquatics]

All good points. I suspect this is why led light bars work better than led fixtures.

The leds are usually the same spectrum in a long row. Then you add another spectrum in another row, much like T5 bulbs.

Some have reflectors as well on each led.

Great discussion and I would say using light bars combined together, one spectrum per bar, would work better than say a Radion fixture that's trying to blend.

 

[razorskiss]

That particular measurement came from this study:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2025647/#!po=33.0769
But this is a general property of fluorescence processes. I'm not arguing that cyan / green isn't utilized, just that it's fundamentally going to be less efficiently utilized than wavelengths that can be directly absorbed. Even higher end LEDs will still use 450ish nm LEDs and PCP will absorb in that range almost as efficiently as in the cyan where its absorbance peak lies.

 

[razorskiss]

All good points. I suspect this is why led light bars work better than led fixtures.

The leds are usually the same spectrum in a long row. Then you add another spectrum in another row, much like T5 bulbs.

Some have reflectors as well on each led.

Great discussion and I would say using light bars combined together, one spectrum per bar, would work better than say a Radion fixture that's trying to blend.

I definitely agree that improving spread, for example with LED bars is a good idea, but I would predict that the benefits from decreased shadowing will be much more prominent than improved micro-scale spectrum blending.

I could be wrong but I'm not aware of any optochemical mechanism that would account for why poorly blended lights would be undesirable except from an aesthetic standpoint (which for an aesthetic hobby is definitely important). The rapid motion induced by refraction through turbulent water is also going to reduce the dwell time of any spectral hot spots to millisecond scales. Granted, I think most products that cause disco ball effects that bad also do a poor job of optimizing their spectra to the near-violet and red peaks of chlorophyll.

 

[oreo54]

Here is the other wrench ..:)
https://www.researchgate.net/publication/261876485_The_in_situ_light_microenvironment_of_corals

Although the detailed ecological implications
remain to be investigated, we show here that corals
harbor complex light microenvironments that can now be
characterized at micrometer resolution under in situ
conditions. Such optical microniches show pronounced
spatiotemporal variation and differ strongly from the
incident underwater irradiance regime, in terms of both
intensity and spectral quality. The optical properties of
the surrounding benthos also affect local light fields and
photosynthesis in corals, and such interaction needs
further attention in coral photobiology studies.

Intresting..

For instance, a 4.4-fold decrease in ambient
scalar irradiance (from 1750 to 400 mmol photons m2/ s )
led to only a 2.4-fold decrease in scalar irradiance at the
polyp tissue (from 126 to 53 mmol photons m2/ s ;
Fig. 6b).

In situ spectral scalar irradiance at the upper surface of
faviid corals—Spectral scalar irradiance at the upper
surfaces of faviid corals (E 0 ) differed markedly from the
incident downwelling irradiance (E d ; Fig. 3). Depending on
the wavelength in the PAR region, the E 0 : Ed ratio varied
between 0.8 and 2.4, with the most pronounced enhance-
ment at wavelengths 500–640 nm and . 680 nm (Fig.
3a–c).

CoralLIghtField

 

[oreo54]

All good points. I suspect this is why led light bars work better than led fixtures.

Or.....because you can't drop output . :)

 

[oreo54]

Approximately 40% of photosynthesis on earth occurs in aquatic environments, where autotrophic organisms form the base of the vast majority of food chains (1). Dinoflagellates are notable among aquatic photosynthetic eukaryotes for using predominately carotenoids over chlorophylls for light harvesting (2). This adaptation allows dinoflagellate lineages to use a larger range of photonic wavelengths to facilitate photosynthesis. PCP and the unrelated chloroplast membrane light-harvesting complex (LHC) mediate excitation energy transfer between associated pigments and reaction centers in the thylakoid membrane, driving photosynthesis (6).

https://collab.its.virginia.edu/acc...erae__1PPR_Peridinin_Chlorophyll_Protein.html

https://www.researchgate.net/public...-a_protein_Insight_into_light-harvesting_stra why tegy_of_marine_algae

Just a tad more..sorry.

Personally I think that, knowingly or not, reef lighting by embracing the "broad blue" spectrum as a "goal" has caught up w/ reality.. Pushing past the 470-ish
;)

As to the violet region.. think that is still open to interpretation.

ANOTHER mystery..
https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-020-00798-w
https://www.nature.com/articles/s41586-019-1072-z
https://www.newscientist.com/articl...en-lurking-unsuspected-in-most-coral-species/

 

[oreo54]

That particular measurement came from this study:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2025647/#!po=33.0769
But this is a general property of fluorescence processes. I'm not arguing that cyan / green isn't utilized, just that it's fundamentally going to be less efficiently utilized than wavelengths that can be directly absorbed. Even higher end LEDs will still use 450ish nm LEDs and PCP will absorb in that range almost as efficiently as in the cyan where its absorbance peak lies.

You may want to consider this.
Coefficients are used to determine concentrations of pigments.
Correct me if I'm wrong here (this is all a bit confusing) but this seems to imply Chl a is less efficient in light absorption at say 440 than "photosynthetic carotenoids" (sadly not just peridinin afaict) at say 490.

ε is the molar absorptivity coefficient that gives light absorbed by 1 mole of a molecule. This is measured in cm2/mole

Chart has odd units to me. Ratios should hold.
https://en.wikipedia.org/wiki/Molar_attenuation_coefficient