Have we been wrong in our understanding of PAR this whole time??

[BeanAnimal]

While turbidity may reduce light transmittance in shallower reefs in sandy coastal areas, it would be reduced slightly reduced intensity more than spectral shift. That and there are surely plenty of tidal lagoons with low turbidity and low surface agitation that are much higher intensity per depth, especially in equatorial areas. I think a lot of these studies and observations are turned into generalizations that don't always fit as tightly as we want them to.

 

[Lasse]

We know from photos taken on a reef that 4m is very much not almost the limit of transmittance

Sorry - do not understand what you mean - please give me a source. Which photos? And where have I say that 4 m is a limit?

Sincerely Lasse

 

[Lasse]

While turbidity may reduce light transmittance in shallower reefs in sandy coastal areas, it would be reduced slightly reduced intensity more than spectral shift. That and there are surely plenty of tidal lagoons with low turbidity and low surface agitation that are much higher intensity per depth, especially in equatorial areas. I think a lot of these studies and observations are turned into generalizations that don't always fit as tightly as we want them to.

From the abstract

Knowledge of water clarity is an essential component of coral reef ecology. While qualitative trends are well known, there are currently few published records of spectral—varying as a (relatively) continuous function of wavelength—water optical properties for these systems. The purpose of this study is to quantify trends in the range and variability of the spectral diffuse attenuation coefficient (Kd) in coral reef and adjacent waters. Using a Biospherical PRR-800, 199 vertical profiles of downwelling spectral irradiance were collected across the reefs and nearby optically deepwaters of Bermuda and Hawaii. A single spectral Kd was calculated for each profile. Results reveal water types ranging from clear oceanic to turbid coastal, with Bermuda and Hawaii showing similar patterns. Kd roughly correlates with reef geomorphic zonation, consistent with well-known reef water characteristics: (a) Suspended sediments are ubiquitous on coral reef flats and in lagoons, chiefly comprising calcium carbonate, which is effectively spectrally flat and has the effect of increasing the overall magnitude of Kd; (b) reefs generate large amounts of dissolved organic matter, which becomes apparent in some lagoonal Kd; and (c) the Kd data exhibit little indication of chlorophyll, which is typically very low in the water column above reefs. These patterns appear reproducible when compared with prior data from French Polynesia. The depth of the 1% light level varies accordingly, approximately 30 m, 45 m, 75 m, and 105 m for lagoon, reef flat, fore reef, and offshore, respectively. The data presented here provide some insight into trends in the spatial context of reef geomorphology and lay the foundation for a more quantitative understanding of reef water clarity and color and their importance to reef ecology.

This was the result and it shows the variation in different situations and places according to turbidity

Sincerely Lasse

 

[BeanAnimal]

Thanks Lasse - I missed that in your prior post. Is that the whole study that is behind the paywall?

 

[SueAubu]

Someone said they weren't sure what wavelengths of light do what. For those of us newbs who still rip their hair out at the first sign of bleaching, I thought I'd add some background. Going back to my days as a biology teacher, I found a couple quotes that would be what I taught about what wavelengths activate which steps of photosynthesis (without me being long-winded about it). Basically, blue wavelengths promote flowers (reproduction) health and growth of our resident photosynthesizers. Red wavelengths promote growth up and out (size & fullness).

PAR stands for photosynthetically available radiation.. or wavelengths. Wavelengths of light activate the different pigments (chlorophyll a,b,c and carotene) in chloroplasts to absorb CO2. "When the PAR rises, Pn increases up to a certain limit beyond which further higher PAR results in a decrease in light-harvesting efficiency and photosynthetic capacity, and a loss of chlorophyll" https://doi.org/10.1016/B978-044450891-1/50020-7

"The blue light wavelength at 400-500nm is connected to growth and flowering and can improve the quality of certain types of plant. When used in conjunction with other grow light spectrum wavelengths, blue light can help you tightly manage growth cycles. The green light spectrum from 500-600nm is not seen to be as useful as the other wavelengths for plant grown but it is valuable for photosynthesis and research has found that green light can ‘actually promote extension growth’ and that the results it offers depend on intensity and type of crop. Then, red light at 600-700nm is one of the most efficient grow light spectrums for photosynthesis and plant biomass growth and is one of the most efficient spectrums for plant growth and energy consumption. Finally, far-red radiation from 700-800nm can promote extension growth and ‘influences the size of the leaves, the length of stems, and ultimately the height of plants.’ " (I'll footnote it, if you want, but it's from a grow house LED system sales page, just the best summary of what I wanted to say...)

 

[SueAubu]

Still, having done the research and having great growth and propagation results from my single Vitaspectra led... I just HAD to go and double the size of my tank, increasing the depth...

I'm starting this PAR stress all over again!!!

 

[areefer01]

Still, having done the research and having great growth and propagation results from my single Vitaspectra led... I just HAD to go and double the size of my tank, increasing the depth...

I'm starting this PAR stress all over again!!!

Why? Don't get caught up marketing and let your display guide you. Control what you can.

 

[HudsonReefer2.0]

Still, having done the research and having great growth and propagation results from my single Vitaspectra led... I just HAD to go and double the size of my tank, increasing the depth...

I'm starting this PAR stress all over again!!!

No stress. Just throw a proven spectrum w 100% intensity for a certain photoperiod like 10 hrs and ur set What’s run at home.

 

[areefer01]

No stress. Just throw a proven spectrum w 100% intensity for a certain photoperiod like 10 hrs and ur set What’s run at home.

Define "proven".

 

[Acroguy]

Blue light does result in more energy, that is stated further up on the wiki page you're referencing. Shorter, higher frequency of waves is more energy.
Whilst I appreciate that the energy may be utilised differently once absorbed it doesn't detract from the fact that if we light our tanks with a fixed rate of par with blue v red light we are going to see vastly different results. I may be wrong in my interpretation of how the energy is used, but it's been proven by numerous studies that blue light is the most beneficial to coral health.
Like I say, I may be slightly misinterpreting the way in which "energy" plays a role, but ultimately my original point that par cannot simply be interpreted as an "energy" reading by which we can base all spectrums on a reef tank is absolutely valid. Blue light evidently has far more importance and is absorbed more by chlorophyll a and b than red light

Well my 5600k plasma light wich is yellow like the sun and full spectrum grows acropora like weed.Night and day difference from blue light wich I’ve also used.Explain that.?

 

[Acroguy]

Corals evolved in the blue light of the sea underwater. No wonder then, that it is the favored light wavelength. White light and infrared add some warmth to the tank. Lighting may influence how well the human cares for the tank.

Yes especially 1-2 meters under water, there is very much blue light indeed…

 

[BeanAnimal]

Well my 5600k plasma light wich is yellow like the sun and full spectrum grows acropora like weed.Night and day difference from blue light wich I’ve also used.Explain that.?

While there may be a predominant yellow cast, it does not mean that the output spectrum is devoid of blue, or blue in high amounts. No different than taking your "full spectrum" led fixture and cranking the white, red and green channels... you overpower the blue cast, but the rest of the spectrum is still there... just like the sun

 

[Lasse]

Yes especially 1-2 meters under water, there is very much blue light indeed…

The amount blue photons is highest just in the surface but they are a smaller part of the total irradiation (photons) compared with further down

Here a comparison between plasm, sun and LED

Sincerely Lasse

 

[Acroguy]

The amount blue photons is highest just in the surface but they are a smaller part of the total irradiation (photons) compared with further down

Here a comparison between plasm, sun and LED

Sincerely LasseIt

 

[Acroguy]

The amount blue photons is highest just in the surface but they are a smaller part of the total irradiation (photons) compared with further down

Here a comparison between plasm, sun and LED

Sincerely Lasse

It was meant sarcastically

 

[jda]

Here is my normal contribution to this type of thread... nearly all corals that we have are collected on one breath in less than 3m of water. Most of them can grow at lower depths up to 15 or 20m, but not all of them. Many of them are taken at low tide in water were people can walk in the substrate around the rocks. All of the BS that some early LED manufacturers put out about corals being only from deep water where only blue light penetrates and all of that was just stupid - you need highly trained people with VERY expensive equipment to go below 100 feet and the collectors that do this want to catch fish that they can get $100+ for from a wholesaler instead of pennies or a buck - a single rare deepwater fish can be fetch a year's salary, or more.

You can go to the South Pacific an collect your own corals - there are many collectors who will let you do this (for a fee). You get a mask, snorkel, some cutters and a mesh bag (or something to put your corals in).

PAR has always sucked. Waves from about 350 to 850nm are important and all of them are in the depths where these corals thrive and certainly where they are collected.

 

[Acroguy]

While there may be a predominant yellow cast, it does not mean that the output spectrum is devoid of blue, or blue in high amounts. No different than taking your "full spectrum" led fixture and cranking the white, red and green channels... you overpower the blue cast, but the rest of the spectrum is still there... just like the sun

This is the spectrum of that plasma light.

 

[Acroguy]

Here is my normal contribution to this type of thread... nearly all corals that we have are collected on one breath in less than 3m of water. Most of them can grow at lower depths up to 15 or 20m, but not all of them. Many of them are taken at low tide in water were people can walk in the substrate around the rocks. All of the BS that some early LED manufacturers put out about corals being only from deep water where only blue light penetrates and all of that was just stupid - you need highly trained people with VERY expensive equipment to go below 100 feet and the collectors that do this want to catch fish that they can get $100+ for from a wholesaler instead of pennies or a buck - a single rare deepwater fish can be fetch a year's salary, or more.

You can go to the South Pacific an collect your own corals - there are many collectors who will let you do this (for a fee). You get a mask, snorkel, some cutters and a mesh bag (or something to put your corals in).

PAR has always sucked. Waves from about 350 to 850nm are important and all of them are in the depths where these corals thrive and certainly where they are collected.

On point

 

[Acroguy]

While there may be a predominant yellow cast, it does not mean that the output spectrum is devoid of blue, or blue in high amounts. No different than taking your "full spectrum" led fixture and cranking the white, red and green channels... you overpower the blue cast, but the rest of the spectrum is still there... just like the sun

Sorry, ignore the my first picture of the spectrum. This is the right one.

 

[HudsonReefer2.0]

Define "proven".

Idk it grows coral, sry not playing semantics and I’m not going to site any studies sry just from my exp. So ab+ @ 100 % has proven to work for me.