By: Megan Siemann
Today for my Coral Reef Ecology class we talked about and saw fluorescence on the reef. Most people see fluorescence every day- in highlighters, neon clothes, and under blacklight. Fluorescence is more common than you probably think (and definitely more so than I thought). What really is fluorescence though? A simple explanation is that when an object fluoresces it sends back a different color of light than was shone on it. On coral reefs using a blue light and yellow filtered goggles at night allows you to see most of the fluorescence that is too dim to see during the day. Diving at Playa Lechi, our typical site here in Bonaire with CIEE, the reef looked like another world. Entering the water after sun went down, ambient light was low enough for fluorescent organisms to glow brightly under the blue lights.
Many corals re-emit orange, green, or yellow light. Fireworms, anemones, and many fish species fluoresce also. For some species, the colors they emit are suggestive of the colors that species can perceive. For example, if a fish fluoresces green light, likely the species can see green light. Signaling is a possible use of fluorescence by organisms on the reef.
Some things are quite difficult to see on the reef during the night when their fluorescence is difficult to detect. At night, however, fluorescent organisms have high contrast from the non-fluorescent background. This makes even coral recruits smaller than a cm2 easy to detect. Diving with fluorescence is a great way to see a familiar site in (literally) a new light.