Despite a disconcerting setback, scientists are still working to compile global maps of plankton that glow in the dark. Four Ukrainian marine biologists, free-lancing for the US Navy, were accused by Ukraine police last fall of exporting military secrets to foreign governments. The four are researchers with the department of plankton at the Institute of Biology of the Southern Seas in Sevastopol. Their Western colleagues -- there are only a few dozen studying marine luminescence worldwide -- have labeled the charges as political and incredible. At first blush, the study of bioluminescent plankton seems harmless enough. The tiny but ecology-critical dinoflagellates and related species flash when they are physically disturbed. This is commonly measured with photomultiplier tubes and image intensifiers, although some research is being done with photosensitive diodes. Plankton luminesces around a swimmer. Courtesy of Michael Latz, Scripps Institution of Oceanography. But some of the information compiled by the Ukrainian biologists had been gathered at a time when bioluminescence was a more important military tool, used to track or sink submarines or for the security of naval forces. One flash, lasting 0.1 s and duplicated by thousands, millions or billions of plankton, can be detected by surface vessels, aircraft and orbiting satellites. The US has done similar research, said James F. Case, a marine biologist at the University of California. Case, who has worked for the Navy on various projects, said the Ukrainian scientists received a relatively small grant to compile their data in England and had published several papers on their findings before the Ukrainian police objected. "The Navy was definitely not buying secrets," Case said. "The papers were on bioluminescence in the Atlantic Ocean," not territorial waters. Michael Latz, a scientist with the University of California's Scripps Institution of Oceanography in La Jolla, said he doesn't do military studies on bioluminescent marine creatures but acknowledged that there is close rapport among the small community of academic and government scientists. His data are published to further the study of marine luminescence and the role that plankton plays in the world's oceans. Perhaps that's what the Ukrainian scientists thought. In a prepared statement, the Office of Naval Research said the project was an international effort "to increase knowledge of the basic scientific properties of the oceans, including the distribution and abundance of marine luminescent animals and plants."