Underwater fluorescence draws MIT Sea Grant researcher


While most scuba divers plunge into the underwater world to escape urban annoyances like fluorescent light, Charles Mazel dives in search of fluorescence.

Under ultraviolet light, many otherwise drab corals, anemones, shrimps and other organisms mysteriously fluoresce in brilliant colors. Such displays are in many circumstances still a mystery, with little known about what causes the illumination within tissues or the function of such brilliance.

To study this phenomenon, Dr. Mazel, a research engineer in ocean engineering and assistant director of the Edgerton Center, designed and built a prototype instrument to measure the spectral distributions of underwater fluorescence. Lydia Chan and Quoc Tran, students in mechanical engineering who have since graduated, collaborated on the project.

The device has now caught the eye of researchers who study how light interacts both with the sea floor and the organisms that live there. As a result, Dr. Mazel has been using it for research in the waters off Southern California and Florida, and will be heading to the Caribbean this summer.

"The light that comes into the ocean affects what grows and what pigmentation it has, and that affects light coming off the bottom," Dr. Mazel explained. Thus, researchers curious about sediments, sea grasses and coral reefs look to light to illuminate their subjects.

Much of the gathering and recording of information from marine environments is accomplished by remote sensing. These techniques include photography, spectral detectors and laser-based sensing, using platforms ranging from satellites and airplanes to unmanned vehicles. Such methods allow scientists to rapidly acquire large amounts of information. However, interpreting the significance of all this data is another matter.

By recording measurements of fluorescence from different sources, Dr. Mazel hopes to understand the biological processes that produce fluorescence and equip scientists with "a library of signatures" for interpreting the vast quantities of data available.

The device that Dr. Mazel and his colleagues built uses a light source, filters and fiber optics to excite the fluorescence of corals and other organisms. A low-cost spectrometer which measures incoming light is hooked up to a computer that logs and stores the spectral data. While some instruments measure a limited range of wavelengths, this device, which Dr. Mazel calls the Benthic Spectrofluorometer, measures the entire spectrum of light emitted. Housed in two watertight plastic boxes, the contraption is small enough to be strapped to a diver's wrist or chest.

Dr. Mazel's investigation of underwater fluorescence began as a sideline while he was pursuing his master's degree in ocean engineering at MIT. What started out as qualitative work, limited to visual observation and photography, turned quantitative-measuring spectral distributions of fluorescence-while he was completing his PhD at Boston University. During that time, Dr. Mazel conceived of an instrument for making these measurements underwater instead of having to collect specimens and bring them back to the laboratory.

Dr. Mazel's MIT Sea Grant-funded research has led to four new related research projects. In a project funded by the Office of Naval Research's Environmental Optics Program, Dr. Mazel and ocean engineering graduate student Eran Fux traveled last summer to Florida's Dry Tortugas with the fluorometer to study both fluorescent and reflected light of corals as part of a multi-disciplinary team.

A Naval Research Lab contract took the researcher to Southern California in October, where he conducted measurements of light reflected from the sea bottom. Dr. Mazel also received funding to build a copy of his instrument for a scientist at Western Washington University. That work took him and Mr. Fux to the Florida Keys in June.

The ONR's Environmental Optics Program has also funded Dr. Mazel to study fluorescence in the Caribbean through photography, video and spectral measurement. That work will be coordinated with efforts to better understand why coral fluoresces and why it does so with varied spectral characteristics, intensity and distribution.

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Charles Mazel's photographs of fluorescing corals, already the subject of an exhibit in MIT's Strobe Alley, will be part of a two-person show at the headquarters of the National Academy of Sciences in Washington this spring. Twenty of Dr. Mazel's photographs will be featured in the show, which runs from April 2 to June 28. For more information call (202) 334-2436.

A version of this article appeared in MIT Tech Talk on March 6, 1996.


Topics: Oceanography and ocean engineering

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