understanding par

Damon- I can talk ALL day about UV lol... Unfortunately this is one place where a few people disagree with me. Anyways, it is too hard for me to follow this thread via my cell phone haha. I will get on my computer tonight and explain UV and any other questions that come up.[/QUOTE]

Looking forward to it, and think your for your time and info. It can be really hard to find some one that not only has the info I am looking for AND can explain it in a way that I can understand..... the second part can be asking a lot some times lol.
Thanks.

 

First, here is a link to a thread from ages ago where I posted the 9 article series by Dana.
http://www.3reef.com/forums/coral/how-color-up-your-corals-71882.html#post692875

Now onto UV... Whether you want to believe it or not, our corals use UV and do much better with it to be honest. T5 bulbs do not release UV but they do get close to UV by going the whole way down to around 400nm. Now im talking about the stuff lower than 400nm though (UVA). If you go down to UVB or UVC you will be risking mutating the DNA and killing the coral as well as its zoox.

UV light is utilized in a lot of photosystems and since violet and UV light travel almost as good as blue light through water, this makes sense. The UV photon will also have more energy attached to it because it has a shorter wavelength. The photosystem can then pull out more energy from each photon. This is because the electrons in the system are excited and move farther from their associated atom. This created a flow of electrons down an electron transport chain... higher energy photons will make the electrons go farther in an ETC. The relative distance traveled can be observed by the gap in nanometers between absorbance and re-emitance, thus giving insight as to how much energy was absorbed. Generally, UV/violet light (380nm) is absorbed and then re-emitted in the far blue to green wavelength, (550nm) which is a pretty large gap in the spectrum, given that it is measured on a logarithmic scale.

Some people say that UV light only produces a "sunscreen" on corals, however this sunscreen is only to block out the UV that is able to mutate the DNA of the symbiotic zoox or else the coral itself. This harmful light is only below the 380nm range and as i stated before, UVA and violet wavelengths are still used verrry efficiently by a majority of corals.

Now here is where LEDs come into play. LEDs do not produce UVA or adequate levels of violet at all... You can purchase violet LED's but they are very expensive. Some people will disagree with this statement but the fact is that the wavelengths are not present and they are not "required" but are heavily relied upon by a majority of corals.

 

Interesting, but I wonder if there actually would be more ability to transfer zooxanthellae in our systems? If you think about it, there are reasons why available zooxanthellae would be limited in the ocean. First, it's big and things tend to disperse. And ability to survive outside of a host for any given time is likely limited. Second, it's stable and things don't change as much as in our systems. Therefore, in many areas, over time, nitches would occur and specific zooxanthellae would come to dominate, leaving little competition in that specific local.

In our tanks, however, we collect coral from all over. So the diversity should be wide. Also, corals with zooxanthellae that is well suited for our systems are more likely to survive. And finally, there are more fluctuations in our systems, leaving more opportunity for corals to expel some of their zooxanthellae. Therefore I would think there should also be more opportunity or inoculation other corals to occur. Of course, this all works better if there is an alternative mechanism of transfer, to the coral bleaching hypothosis. Although that does happen from time to time. Maybe more, if the light source does not have a significantly diverse spectrum?

However, I am not aware of any alternative to the coral bleaching hypothosis. However, for the sake of argument, maybe there is no alternative to the coral bleaching hypothesis due to the reasons described above. There just isn't enough opportunity for alternative modes of transfer to occur.

Especially now, with the ability to obtain leds with fairly specific wavelength output. Light adaptation seems like an area of marine biology hobbyists can actually contribute to. granted it probably wouldn't be looking at specific zooxanthellae, yet...

Anyways, sorry, fascinating subject ;D

 

I would love to jump in, but I have a friend in town for a few days, so I will just have to wait to read the last posts. I really am looking forward to learning more, and can't wait to get back to this.