Investigation of in Situ Surface Plasmon Resonance Spectroscopy for Environmental Monitoring in and around Deep-Sea Hydrothermal Vents

We have developed a fiber optic Surface Plasmon Resonance (SPR) sensor capable of continuous in situ and real-time monitoring of physical or chemical properties in and around deep-sea hydrothermal vents. The spectroscopic sensor system was deployed on three Alvin cruises to hydrothermal fields in the eastern Pacific: cruise AT11-20 to the East Pacific Rise (EPR) and cruises AT11-31 and AT15-09 to the Juan de Fuca Ridge. The SPR-based sensor was integrated with a thermocouple employed to measure the densities of hydrothermal vent fluid and seawater surrounding the vent. The system was battery powered and placed in a pressure vessel capable of operating six kilometers below the ocean surface in and around hydrothermal vents. Results show the potential of in situ SPR analysis for monitoring in and around hydrothermal vents, including the ability to characterize spatial gradients of the dissolved hydrocarbons and mixing of vent fluid.