Re: Can marine animals get sunburned?

Hi Ashley

Sunburn, as you may know, is due to the damaging effects of ultraviolet radiation in sunlight. UV is damaging because of its high-energy (i.e. high-frequency) short-wavelength nature. However, this also means that when it enters a dense medium with dissolved substances, such as seawater, it is very quickly scattered and blocked, and does not penetrate very far (much like blue light which penetrates less than red or green wavelengths).

So, marine animals do not have a problem with UV light, even if they are quite near the surface, and have generally not evolved defenses against it. So, if you put a fish in direct sunlight, it would burn, but not before it suffocated due to its gills drying out of water.

Damage to the ozone layer causes problems for marine plants though, as they can not move deeper to avoid the increased levels of UV. This doesn't cause sunburn as we understand it in animals, but has the biochemical equivalent in plants by reducing their rate of photosynthesis, and may damage their DNA (in the same way that burning may lead to skin cancer in humans).

I hope that answers your question, both for fish and other marine organisms.

Dr David Hubble, UK

Reference
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'Environmental Physiology of Animals' by Pat Willmer, Graham Stone & Ian Johnston. Published by Blackwell (2000).

ADMIN NOTE:
Although UV doesn't seem to harm things the size of fish and larger, it does appear to affect zooplankton and phytoplankton.
Zooplankton will adjust the amount of pigments in their body depending on water clarity in order to prevent UV damage - that's a trade off, because more pigments means that they're more likely to be spotted by a predator! Phytoplankton also have "photoprotective" pigments that they produce to protect them from UV.
-Rob Campbell