Charles Mazel on Coral Fluorescence
Fluorescence in the Marine Aquarium

More than thirty years ago, a simple love of night diving led Dr. Charles Mazel to a career focused on the optical properties of marine organisms, especially corals. No stranger to the ocean, Mazel has accomplished many firsts, including leading the team that outfitted the first manned research submersible searching for deep sea fluorescing organisms. A friend of the aquarium industry, Dr. Mazel has spoken at IMAC and MACNA conferences and is on the Marine Aquarium Societies of North America, Inc. (MASNA) speakers list.

While he has excavated famous shipwrecks, worked in the deep sea survey business, managed a hydrodynamics laboratory at MIT, and served as the assistant director of the Edgerton Center at MIT, for the last ten years Dr. Mazel has been employed as a Principal Research Scientist at Physical Sciences Inc. in Andover, MA. He is also the founder of NightSea, a company committed to making the joys of underwater fluorescence available to all.

We are honored that Dr. Mazel has taken the time to share his thoughts regarding fluorescing organisms in the aquarium with Blue Zoo News.

BZN: Thank you very much for taking the time to answer some questions for us, Dr. Mazel. Let’s start at the beginning—when did you first become aware of fluorescence in corals and other reef animals?

CM: I became curious about fluorescence in the early 1970s. I was a scuba diver, and I liked diving at night. Somewhere along the way I wondered what would happen if you swam around with an ultraviolet light-would anything fluoresce, and could you photograph it? I made some early attempts then, but then dropped it as I became busy with other things. I went back to it in the mid-1980s, building my own underwater ultraviolet lights and adapting my camera setup. I was doing this in the cold waters of Massachusetts, and when I finally had things working I booked a trip to Roatan, off the coast of Honduras. My first dive there with the lights was just spectacular and really fixed me on this path. I later came to find out that others had done some work with coral fluorescence, but I wasn’t aware of it and am glad I wasn’t—If I had known about it, I might not have been so motivated to continue for myself.

BZN: What is fluorescence in corals and other reef animals?

CM: From the physics point of view, fluorescence is the process by which light of one wavelength (color) is absorbed in a substance and transformed into another color. On the biology side, fluorescence comes from a few sources—the intense greens, yellows, and oranges in your corals and anemones come from fluorescent proteins in the host tissue; a deep red fluorescence originates from chlorophyll in algae, including the symbiotic algae in the invert tissues, and algae coating live rock and your tank walls. You get an orange fluorescence from phycoerythrin, a photosynthetic accessory pigment found in red algae and cyanobacteria. We have found fluorescence in many other reef animals, including fish, shrimp, crabs, mantis shrimp (more on them below), bristleworms, and more. In many cases we have no idea what is doing the fluorescing.

BZN: While many aquarists are familiar with the effects produced by actinic lighting, what are the best ways to stimulate and observe fluorescing proteins in coral?

CM: You can certainly see fluorescence under actinics. You can even see some of it under normal white lighting, since fluorescence contributes the intense greens seen in many specimens. But with actinics you don’t get the full effect, for two reasons. One is that both the fluorescence and the reflected blue from the lights reaches your eyes, giving you a mixed color effect. The other is that the intensity per unit area is just not high enough to bring out the effects that are there. The best way to look at fluorescence is by illuminating with an intense light source and viewing through matched filters to completely block the reflected light and pass only the fluorescence. The effect is much more dramatic and you will see a lot more fluorescence in your tank. And it’s not just the corals and anemones. With the actinics you won’t see the red chlorophyll fluorescence, but it will stand out with an intense source.

BZN: Beyond its aesthetic value, what is the value of fluorescence in corals? To medical research? To studies concerning coral bleaching?

There are two ways to look at value—what’s the value to the animal doing the fluorescing, and what’s the value to the scientist. For corals there are a number of theories, but none have yet been proved. It is thought that it might be a ‘sunscreen’, protecting corals or their algae from too much light and protecting against bleaching. But there is at least one scientific paper arguing that corals with fluorescent pigments are more sensitive to bleaching. There is another idea that it might actually help photosynthesis in darker, light-limited environments, or that it may act as a beacon. Or the protein may be performing some biochemical function totally unrelated to its fluorescence.

It’s a different story when it comes to the value of fluorescence for scientists. The fluorescence of juvenile corals makes it possible to find newly settled juveniles on the reef, and marine biologists are using this to study coral recruitment. This works in your own tank, too—you will see tiny corals and anemones that you never suspected were there.

Coral fluorescence is playing an incredibly valuable role in medical research. The genetic code for the proteins that fluoresce in corals can be inserted into the genes for different cells in fish, mice, and other laboratory subjects. The resulting fluorescence is an easy tracer for the development of organs, the effectiveness of anti-tumor treatments, and many other applications. The same equipment that NightSea provides for hobbyists to use with their aquaria is being used in laboratories around the world to observe their fluorescent subjects.

BZN: For the aquarist who wants to design a system featuring fluorescence in corals and other reef animals, what recommendations would you make concerning equipment and livestock?

Your livestock doesn’t have to be very different from what you already have. You can select specimens that are known to fluoresce and arrange them so that they are exposed to whatever fluorescence excitation source you are using. Actinics and moonlights will bring out some of the fluorescence, but for the most dramatic effects, and to see chlorophyll fluorescence and smaller specimens you will need more intense light sources. With the right equipment you will be surprised at how much fluorescence there is in specimens that don’t look at all fluorescent under white light or even actinics.

BZN: Tell us a little more about NightSea, its mission and the products that may be of interest to the marine aquarist.

CM: I had been building fluorescence viewing and photography equipment for myself for years, mostly in support my research work. A number of years ago I decided to make the equipment available to others and started NightSea with the mission of sharing my enthusiasm for fluorescence with others. Originally the primary users of the gear were sport divers and marine biologists. More recently there has been interest from the aquarium community. The main product for that is the NightSea BlueStar flashlight together with a pair of yellow filter glasses. The light produces a really intense blue spot to excite the fluorescence, and the glasses are matched to the light so that they completely remove the reflected blue and pass the fluorescence to your eyes. (In addition to lots of aquarists, there are almost 200 research and educational institutions worldwide using NightSea gear for a variety of applications, both above and below water. –ed.)

BZN: I’m not sure you knew this, but Blue Zoo Aquatics is somewhat known for our work with mantis shrimp. We understand you made an interesting discovery regarding fluorescence and mantis shrimp. Will you tell us a little bit about this?

CM: This was a case of bad luck leading to good luck. I was leading a small team on a research project in the Bahamas specifically to search for fluorescence in animals other than corals. It was May and the weather should have been great, but a weather front came through and stalled and for day after day it was too rough to get out to the reefs on the windward side of the island. We ended up doing a lot of night diving right off the boat dock at the research station. One night I was testing a video camera rigged up for fluorescence imaging and the other two divers wandered off to scout around. When I caught up with them they were lying on the bottom with their lights pointed at this critter in a hole in the sand–this was in about 7’ of water, just off the dock. I recognized it as a mantis shrimp—the first one I had ever seen in nature—and it had a bright yellow-fluorescent patch on its ***. I videotaped the mantis for about 25 minutes, and I was lucky enough to film it spearing a not-too-bright fish that came by. I sent the video to a colleague who researches mantis shrimp vision, and he got really excited. This led to a team of four of us trying to figure out what the spot was for. Roy Caldwell from UC Berkeley, a leading expert on stomatopod ecology, got great photos, both white light and fluorescing, of a mantis shrimp in a threat display. We documented that fluorescence functioned to keep that spot bright at greater depths, where yellow light would normally be absorbed. This was the first demonstration of a color-related function of fluorescence in a marine animal.

BZN: I guess it’s appropriate to end on yet another first for you, Dr. Mazel. It has truly been a pleasure speaking with you. Thank you for sharing your thoughts on fluorescence, and thank you for being so committed to the intersection of hobby and science.

Please do visit NightSea at www.nightsea.com/aquarium.htm, where you will find the NightSea BlueStar flashlight the yellow filter glasses to which Dr. referred in this interview. You can also see the mantis shrimp, fish-spearing video clip on the NightSea web site www.nightsea.com/mantis.htm.

Published 27 May 2008. © Blue Zoo Aquatics