Smart Sensors for In Situ Monitoring of Hydrothermal Vent Systems.
Proposal: 0119999 Date: June 27, 2001 PI: Booksh Institution: Arizona State University
This project is supported by the program Biocomplexity in the Environment, subprogram Instrumentation Development for Environmental Activities (BE-IDEA). The objective of this project is to develop a suite of five sensors designed for in situ analysis of the ecosystem in and around hydrothermal deep-sea vents. This ecosystem may be one of the most ancient of Earth and have had a long-term effect on global geochemical cycles, yet it is one of the least well understood. Hydrothermal vent ecosystems are in a turbulent state of disequilibrium with large gradients of thermal and chemical energy. Along this thermal/chemical gradient a complex ecosystem of tube worms, thermophilic microbes, and specially adapted crustaceans and fish survive The sensors are chosen that best monitor the physical, chemical, and biological environment of the vent ecosystem to better understand the inter-relationship between this unique environment and the life that it supports. The development of in situ chemical sensors will provide a significant advancement in the state of the art of hydrothermal vent monitoring.
We will employ a fiber optic surface plasmon resonance (SPR) based sensor integrated with a thermocouple and conductivity sensor to better measure the density hydrothermal vent fluid and salinity of the seawater surrounding the vent. Fiber optic SPR sensors can be made sufficiently small and sensitive to probe the vent fluid/sea water gradient where many thermophilic microbes reside. A fiber optic coupled grating light reflectance spectroscopy (GLRS) sensor will be employed to monitor the size distribution and relative abundance of mineral precipitates that form during the mixing of vent fluid and sea water. This precipitate forms the vent chimney walls where most microbes reside. Fiber optic Raman spectroscopy probes will be tested to detect trace organic molecules that may be forming biotically or abiotically in the vent fluid. Raman spectroscopy will also be tested to survey the mineral and microbial distribution on the vent walls. An ambient pressure driven liquid chromatography-Raman spectroscopy system will be developed to enhance the selectivity and sensitivity of Raman spectroscopy to simple organic molecules that may serve as food for or originate as waste from microbes in the vent ecosystem. Sensitivity enhancement will come from novel waveguide technology that has been demonstrated to push Raman detection limits to low ppb for simple alcohols. Finally, a fiber optic, single measurement excitation-emission matrix (EEM) fluorometer will be adapted to detect and characterize larger biomolecules such as amino acids, proteins, and DNA fragments that may prove indicative of biological activity in the vent ecosystem Each of the proposed sensors has been previously developed past the proof of concept stage for environmental or industrial process monitoring. The project will adapt and test the sensors for the more challenging application of deep sea vent monitoring. The sensors represent a promising technology that fills a large need in the oceanographic/ life in extreme environments community. If the proposed NEPTUNE network of deep-sea research nodes were built, these sensors would be ideal for long-term field deployment. Successful development of these sensors would lead to expansion of the technology for other biological and environmental process monitoring applications.
