Environmental Health - Toxic Substances Hydrology Program
These graphs summarize the data used to document changes in San Francisco Bay phytoplankton (measured as chlorophyll a concentrations) caused by the prolonged cold phase in the ocean off the California coast. The cold phase occurred between 1999 and 2004 (yellow shaded area). From top to bottom the graphs are:
(1) The differences from the average (mean) sea surface temperatures in degrees Celsius measured at Farallon Islands between 1977 and 2005,
(2) An index of the abundance of three clam predators in the Bay expressed as differences from the average (mean) annual catch per hectare of English Sole, Bay Shrimp, and Dungeness crab in San Francisco Bay from 1980 to 2005,
(3) Biomass of bivalves (clams) and phytoplankton in San Francisco Bay. Biomass is the quantity of a living community or population and is usually expressed as weight per unit area. The clam biomass (blue squares) is given in grams dry weight per square meter. Scientists use chlorophyll a concentration to measure how much algae (phytoplankton biomass) are suspended in water. The median chlorophyll a concentration in San Francisco Bay for the months August through December (green circles) is given in milligrams per cubic meter (mg/m3).
Cloern, J.E., Jassby, A.D., Thompson, J.K., and Hieb, K.A., 2007, A cold phase of the east pacific triggers new phytoplankton blooms in San Francisco Bay: Proceedings of the National Academy of Sciences of the United States of America, v. 104, no. 47, p. 18561-18565, doi:10.1073/pnas.0706151104.
Cloern, J.E., Jassby, A.D., Schraga, T.S., and Dallas, K.L., 2006, What is causing the phytoplankton increase in San Francisco Bay?, The Pulse of the Estuary -- Monitoring and managing water quality in the San Francisco Estuary: San Francisco Estuary Institute Annual Report 2006, 62-70 p.