UV Dive Lights

[Cheekymonkey]

To start off with, I have been seeing for the last year a lot of UV dive lights, UV night dives, UV photography etc. Besides being an avid diver, my income as well as my hobby is generated from the keeping of live corals and reef aquariums

I am curious how many folks are aware that UV light is severely damaging to corals?

I imagine most of you know it isn't the greatest thing in the world for us to be over exposed too, and that part of our bodies are more sensitive to it. For corals it is absolutely brutal, the very thin tissues that are the coral polyp are incredibly sensitive to UV, and just a couple minutes of UV exposure can end in death.

Anyone that has ever spent any time on the pacific reefs, especially shallow ones that are exposed to air have noticed that the corals emit a sort of slime after a few minutes exposed to air. One purpose of that is for UV protection.

So I guess at the end of the day I am curious who already knew this, and knowing this if you still intend to do "UV dives".

 

[UCFKnightDiver]

Never really thought of UV light being damaging to corals interesting.

 

[Packhorse]

What do you base this on?

 

[Matt S.]

If I shine my HID light on some coral with a UV filter in place, that is damaging where the full force of the unfiltered light is not?

UV light that is as or more intense than what the coral might receive naturally could be bad, that seems obvious... but that isn't what's being emitted by dive lights, I think.

 

[Cheekymonkey]

What do you base this on?

Personal experience dealing with people's captive corals. Black lights in particular are famous for killing corals, and they have fairly low UV.

Additionally the need for UV filters between their aquarium lighting and their photosynthetic organisms is well known among aquarists.

This article does not directly pertain to UV lights, but addresses UV as a possible cause of bleaching events. UV Exposure of Coral Assemblages in the Florida Keys

If you have journal access through work or school, this article was all about the differing UV tolerances of reef animals based on depth, higher tolerance higher in the water column, and lower tolerance as you descend. http://www.springerlink.com/content/h56883637161t778/

If I shine my HID light on some coral with a UV filter in place, that is damaging where the full force of the unfiltered light is not?

UV light that is as or more intense than what the coral might receive naturally could be bad, that seems obvious... but that isn't what's being emitted by dive lights, I think.

I don't know for sure, but I doubt the dive lights with UV filters in place are particularly a problem at their relatively low wattage, however a quick google showed that there are a number of UV bulbs being marketed that intentionally produce more UV.

I would love a light meter that only reads in UV, it would be interesting to test at what UV lamps put out more UV then naturally reaches specific depths in the ocean. Unfortunately my meter is only a PAR meter.

Anyway, just beginning a discussion.

 

[Packhorse]

There is a huge difference between an aquarium that constantly have a UV light shining away on it and a open water reef that has a UV dive light shine on it for 5 seconds.

 

[Matt S.]

You can also get some interesting views using colored light, not UV. I did this in my reef tank with a blue LED flashlight.

Wrongcrowd Gallery :: Nano Cube :: mushroom_coral_led1

 

[Blazinator]

I would love a light meter that only reads in UV, it would be interesting to test at what UV lamps put out more UV then naturally reaches specific depths in the ocean. Unfortunately my meter is only a PAR meter.

Anyway, just beginning a discussion.

Interesting topic Mr. Monkey. The light meter you reference is called a radiometer, and I used them all the time when I was a UV chemist (UV cured coatings and adhesives), and they measured two separate important measurements: intensity of the UV radiation and the quantity of the radiation, and gave those measurements in all four common bandwidths of UV A, B, C and D wavelengths, measuered in milijoules.

It was along time since then, but here is an expert opinion as simplified as possible:

Radiation damage is infinitely more dangerous over longer time (quantity) at low intensity like from aquarium fluorescent bulbs rather than short bursts of time at high (relative) intensity (a few seconds from a divers HID light).

I will give you this - HID Lights do put out a lot of intensity of UV (way more than LED or halogen) and my 24 watt HID will cure my UV resins within seconds (which I love because my dive light became a tax write off for my business when I started using it to spot cure my resins).

While I never measured the radiation from common fluorescent bulbs (same as used in aquarium black lights, just no phosphorescent coatings - violet paint/glass instead), they output a huge amount of UV for their wattage (they will cure UV resins from ten feet away within minutes), which makes sense why the aquarium world would see damage to coral tanks.

But UV damage from high-powered HIDs? Definitely debateable, if not negligible.

I will, however, thanks to you, increase my distance from the corals on my UV night dive photo shoots, and try to reduce the time I hold the light on them (video doesn't require lots of dwell time anyway).

BTW, we did measure sunlight with the radiometer, and there was significantly more radiation than fluorescent bulbs would produce, and shallow corals are under that intensity for many hours of the day (hense bleaching), and that is seriously more UV than any divers will ever radiate.

 

[CompuDude]

Thanks for the info, Blazinator!