Raman spectroscopy in the deep ocean: Successes and challenges

The deep-ocean Raman in situ spectrometer (DORISS) was deployed down to a depth of 3.6 km in April 2002 in Monterey Bay off the coast of California. The aim was to determine the possibility of obtaining on the sea floor at a depth of 3600 m Raman spectra having high signal-to-noise ratio and very good spectral resolution. Due to the need for DORISS to be placed repeatedly at different sites on the sea floor, a frequency-doubled Nd:YAG laser operating at 535 nm was chosen as the core instrument. From 2002-2003, Raman spectra of seawater, CO2, and various solids were taken. Laboratory tests were made with a duplicate KOSI Raman instrument to validate data obtained using DORISS. Preliminary results show that despite the many difficulties that need to be overcome during construction and implementation of DORISS, the project aim was successfully met.