Editing Biosensor (section)

===Ozone measurement===
Because [[ozone]] filters out harmful ultraviolet radiation, the discovery of holes in the ozone layer of the earth's atmosphere has raised concern about how much [[ultraviolet light]] reaches the earth's surface. Of particular concern are the questions of how deeply into sea water ultraviolet radiation penetrates and how it affects [[Marine life|marine organisms]], especially [[plankton]] (floating microorganisms) and [[virus]]es that attack plankton. Plankton form the base of the marine food chains and are believed to affect our planet's temperature and weather by uptake of CO<sub>2</sub> for photosynthesis.

Deneb Karentz, a researcher at the Laboratory of Radio-biology and Environmental Health ([[University of California, San Francisco]]) has devised a simple method for measuring ultraviolet penetration and intensity. Working in the Antarctic Ocean, she submerged to various depths thin plastic bags containing special strains of ''E. coli'' that are almost totally unable to repair ultraviolet radiation damage to their DNA. Bacterial death rates in these bags were compared with rates in unexposed control bags of the same organism. The bacterial "biosensors" revealed constant significant ultraviolet damage at depths of 10 m and frequently at 20 and 30 m. Karentz plans additional studies of how ultraviolet may affect seasonal plankton [[Algal bloom|bloom]]s (growth spurts) in the oceans.<ref>J. G. Black,"Principles and explorations", edition 5th.</ref>