The U.S. Geological Survey is actively engaged in the study of many different aspects of San Francisco Bay, such as changing land use, hydrology, water currents, nutrients, toxic contaminants, geologic structure, and biological communities. This website provides information about the following components of water quality: salinity, temperature, suspended solids, dissolved oxygen, light penetration, and chlorophyll concentration. These parameters are measured using a submersible instrument package called a CTD. See our page describing how we calibrate the CTD.

Our CTD includes sensors for measuring: depth (Paroscientific Digiquartz pressure transducer), conductivity (Sea-Bird Electronics 4 conductivity sensor), temperature (Sea-Bird Electronics-3 thermistor), suspended solids (D&A Instruments optical backscatter sensor), chlorophyll (Turner Designs Cyclops7 fluorometer), light penetration (Li-Cor 192s quantum sensor), and dissolved oxygen (Sea-Bird Electronics-13 oxygen electrode). These sensors are integrated with a Sea-Bird Electronics-9 data acquisition system that digitizes and records signals on a personal computer 24 times per second. The package is lowered through the water column at about one meter per second, so measurements are made about every 4 centimeters from the water surface to the Bay bottom. Sample depth profiles of data collected from each sensor can be viewed by clicking on the image to the right or on any parameter in the list below.

These basic elements of water quality define the sustainability of the Bay as habitat for fish and organisms of the lower trophic levels. Learn more about the dynamics of these elements by viewing examples of data displays in San Francisco Bay.