ABSTRACT
This chapter presents a brief overview of the large range of optical sensing technologies that are used to great effect to measure our oceans and aquatic environments. Natural biogeochemical cycles in the oceans alone provide "ecosystem services" valued at US$19 trillion per annum in 1997, equivalent to the global gross national product. A central problem in oceanography and aquatic applications is the acquisition of data over the vast expanse and depth of the oceans, rivers, and lakes. Direct optical systems are used to great effect in remote sensing/satellite sensors. In situ sensors can provide high accuracy measurements of subsurface and surface water parameters at high temporal resolutions and if deployed in number, or combined with moving platforms, can make measurements over wide geographic scales. Indirect optical methods are powerful for creating high specificity and high performance in situ sensors because sensitivity to the parameter of interest can be greatly enhanced by modification of the sample.
