is to be established, a substantial parallel investment in sensor technology will be necessary.

CURRENTLY AVAILABLE TECHNOLOGY

Sensors currently available for deployment in a seafloor observatory setting include those for basic physical measurements (temperature, pressure, turbulence, optical clarity, current velocity, wind speed, wave height, seismicity, acoustics, magnetics, gravity), measurements of water properties (conductivity, oxygen, nutrients, dissolved gasses, analysis of suspended particles), and biological measurements (fluorescence, video plankton recorders, hydrophones for ambient noise, acoustic sensors for detection of biota, and gene chips1). There are also several types of samplers available for the collection of fluids and biological samples that require shore-based analysis. Many of these sensors and samplers, however, are not presently suitable for long-term deployment for a variety of reasons, such as the need for frequent servicing, instability of chemical reagents, sensitivity to biofouling, or intolerance to high temperatures (for example, there are currently only a handful of properties [temperature, pH, H2S]) that can be measured in 300°C hydrothermal fluid). Thus, the properties of most high-temperature hydrothermal fluids are presently determined by laboratory analysis of samples after they have cooled. Biofouling is another problem that affects almost all seafloor instrumentation and is especially severe with video cameras, pumps, and other instruments deployed at hydrothermal sites.

In each of the research disciplines, there are certain “basic” sensors that are considered so critical or common that the observatory should supply them as part of the standard infrastructure. At coastal observatories (see Chapter 2, section titled “Coastal Ocean Processes”), these include sensors for basic meteorological conditions (wind speed, air temperature, air pressure); for ocean surface conditions (current velocity, wave height, turbulence); and for water column conditions (temperature, conductivity, nitrate, dissolved gases, pH, gene chip, plankton recorder, water sampler, fluorometer, acoustic fish-tag trackers). For the deep ocean (see Chapter 2, sections titled “Role of the Ocean in Climate,” “Turbulent Mixing and Biophysical Interaction,” and “Ecosystem Dynamics and Biodiversity”), many critical water-column measurements are similar to those for coastal regions, but they also include sensors for pressure and horizontal electric field, inverted echo sounders, hydrophones, and bioacoustic profilers. In the case of benthic experiments (see Chapter 2, sections titled “Fluids and Life in the Oceanic Crust” and

1  

Although gene chip technology currently exists, it will need significant refinement to be suitable for wide use in oceanographic research.



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