Water Quality
Greater Farallones

california coast line
Coastal areas of the sanctuary can be impacted by land based pollution that can reduce water quality. Land based pollutants including runoff, agricultural waste products, and residual sediments can travel in streams to coastal habitats. Credit: Jenny Stock, CBNMS, NOAA

Why is it a concern?

Water quality can be impacted by the presence of contaminants (for example pesticides,  oil pollution, and heavy metals), excessive sedimentation, and elevated nutrient loads. Hundreds of millions of tons of waste have been dumped into the Greater Farallones since the mid-1800s. Since the 1940s, this has included waste from oil refineries and fruit canneries, acids from steel production, and ships from World War II and other unwanted vessels. From 1958 to 1969, the U.S. military disposed of chemical and conventional munitions at several sites in the Greater Farallones, mostly by scuttling World War II-era cargo vessels. Between 1946 and 1970, approximately 47,800 containers of low- level radioactive waste were dumped into the Gulf south and west of the Farallon Islands. In addition, evidence suggests that several other types of wastes were dumped, including cyanides, mercury, beryllium and other heavy metals, dredge spoils, explosives, and garbage, although available documentation does not specify an origin.

Open coastal and offshore areas of the sanctuary are also threatened by nonpoint source pollution. Coastal and offshore regions of the sanctuary are threatened by acute events (large ship-based spills) and ongoing chronic sources (San Francisco outflow). Outflow from San Francisco Bay carries pollution from the 8 million people living in the Bay Area, including sewage outfalls, combined sewage overflows, agricultural waste products from the Central Valley, and residual sediments and metals from historical mining. In addition, treated wastewater discharges from the city of San Francisco and San Mateo County are located to the southeast of the sanctuary.

Historically, oil pollution is one of the biggest threats to the health of the sanctuary.  The total number of spills from transiting vessels is small, but the potential impacts may be enormous given the number and volume of vessels, and their proximity to the Farallon Islands and major seabird and marine mammal populations.  Since designation there have been six large oil pollution events, releasing more than 750,000 gallons of bunker and crude oil, costing more than $52 million dollars for clean-up and restoration.

In addition to current threats, persistent organic pollutants such as DDT and PCBs were widely used nationwide before the mid-1970s and residuals of these chemicals still remain in sediments and organisms within the sanctuary. Elevated levels of pollutants have been reported for fish, seabirds and marine mammals, and are suspected to have caused and sustained in part the decline of pupping rates in Steller sea lions.

Overview of Research

Sampling for nutrients occurs three to four times a year, through our ACCESS monitoring project. Nutrients can be analyzed for status, trends, contribution and influences from San Francisco Bay and the San Francisco sewage outfall. Data from ACCESS contributes to our understanding of how these sources of nutrient loading may contribute to harmful algal blooms or low O2 and eutrophication. Monitoring oil pollution in GFNMS is a primary objective of the Beach Watch project. This monitoring project detects oil pollution from known sources, as well unknown sources and natural seeps. Since the establishment of Beach Watch, oil pollution rates have decreased by at least half.

Project Name PI and contacts Links

Cetacean & Ecosystem Assessment Survey of the California Current

Jay Barlow


Beach Watch

Jan Roletto and Kirsten Lindquist


Applied California Current Ecosystem Studies

Jan Roletto, Jaimie Jahnke, and Dani Lipski


Phytoplankton monitoring and early warning

Gregg Langlois



Science Needs and Questions

The best available science is used by Sanctuary scientists and managers working to address priority resource conservation and management issues. As priorities change and new issues emerge, each Sanctuary develops new science needs and questions and works with partners to address them.

  • What are the resources at risk form oil pollution?  Where do vulnerable species concentrate and what time of year are they most vulnerable?
  • What are the net environmental benefits to the use of alternative response techniques, such as dispersants, in situ burning and bioremediation?
  • What are the potential sources and risks of emerging pollutants to surface waters and near shore environments?
  • Is oil pollution increasing or decreasing in the sanctuary?
  • How is the sewage outfall from San Francisco public utilities impacting the nearshore and offshore water quality?
  • Under what conditions do harmful algal blooms (HABs) produce biotoxins?
  • Are there areas of the sanctuary where HABs are more likely to occur?  Under what oceanographic conditions will HABs most likely occur?
  • What are the levels of legacy pollutants in locally breeding seabirds and marine mammals?

Education and Outreach Material

Please refer to the Greater Farallones National Marine Sanctuary website to learn more
about education and outreach materials.


Office of National Marine Sanctuaries. 2010. Gulf of the Farallones National Marine Sanctuary Condition Report 2010. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries, Silver Spring, MD. 97 pp.

Chin, J.L. and A. Ota. 2001. Disposal of dredged materials and other wastes on the continental shelf and slope. In: Karl, H.A., J.L. Chin, E. Ueber, P.H. Stauffer, J.W. Hendley, J.W. (eds.) 2001. Beyond the golden gate—oceanography, geology, biology, and environmental issues in the Gulf of the Farallones. U.S. Geological Survey Circular 1198. 84 pp. Electronic document available from: http://pubs.usgs.gov/circ/c1198/

Gulland. F.  2000.  Domoic acid toxicity in California sea lions (Zalophus californianus)stranded along the central California coast, May-October 1998.  NOAA Tech. Memo. NMFS-OPR-17, National Oceanic and Atmospheric Administration, Silver Spring, MD, 45 p. (contributing author).

Jones, D.G., P.D. Roberts, J. Limburg, H. Karl, J.L. Chin, W.C. Shanks, R. Hall, D. Howard. 2001b. Measurement of seafloor radioactivity at the Farallon Islands radioactive waste dump site, California. U.S. Geological Survey Report 01-62. Electronic document available from: http://pubs.usgs.gov/of/2001/of01-062/

Roletto, J., J. Mortenson, I. Harrald, J. Hall, L. Grella.  2003.  Beached bird surveys and chronic oil pollution in central California.  Marine Ornithology 31(1): 21-28.

Sydeman, W.J. and W.M. Jarman. 1998. Trace metals in seabirds, Steller sea lion, and forage fish and zooplankton from Central California. Mar. Poll. Bull. 36:828-832.