Tarballs Wash up on Sanctuary Beaches

By Shannon Lyday
Published: March 2007

Beach Watch Volunteers inspecting a dead bird.

Nothing can ruin a beautiful walk on the beach like coming across a dead bird covered in oil. In the beginning of February, Beach Watch volunteers started noticing tarballs and oil-covered birds during their monthly beach surveys.  Sarah Lenz, a Beach Watch volunteer and ranger at Fitzgerald Marine Reserve noted, “All along the wrack line were continuous tarballs, ranging from the size of a pencil eraser to over 5 inches.  I have never seen so many tarballs in the three years I have worked at Fitzgerald.”

Tarballs are dark, sticky remnants of oil that can be as small as a coin or weigh many pounds.  As oil floats on the surface of the ocean, its physical characteristics change, a process called “weathering”.  In some instances, tarballs can remain buried on a beach and be re-exposed after storms.  This is especially the case at two beaches in Point Reyes National Seashore, Drakes East and Limantour West, where surveyors constantly encounter old, weathered tarballs. 

But last month, after heavy seas, Beach Watch surveyors from Bodega down through Año Nuevo documented fresh, sticky tarballs along long expanses of beach.  Some volunteers collected over three pounds of tarballs off of their beach.  Oiled birds were also documented, including a Northern Fulmar and a Common Murre. GFNMS Research Coordinator Jan Roletto explained, “Tarball deposition is correlated to swell height, direction, wind speed and wind direction, with wind direction having the strongest influence for bringing at-sea carcasses and tarballs on shore.”

The Department of Fish and Game Office of Spill Prevention and Response (OSPR) lab “fingerprinted” the oil samples to determine the source, using gas chromatography mass spectrometry analysis.  The tarballs that were tested were typed to the Monterey Formation, indicating that the oil source is natural seeps.  According to Irina Kogan, GFNMS Resource Protection Specialist,  “The Monterey Formation is a prolific source of crude oil in California.  The majority of known seeps are in southern California and it is probable that currents transported the tarballs to the central coast. However, the Monterey Formation is also present in this area and evidence of a local hydrocarbon system indicates that there could also be local seeps into the Sanctuary.”  Although it is a naturally occurring source of oil, tarballs are still a hazard to wildlife and people.  Animals can ingest the oil, and sea birds can get oil on their feathers, causing them to lose insulation and die of hypothermia.

Beach Watch is a long-term monitoring program in which citizen scientists collect data on live and dead birds and marine mammals, and assist the Sanctuary in the early detection of oil events.  The volunteers survey “their” beach segment once a month, and are trained in documenting and sampling tarballs and oiled wildlife. In 1996, the information gathered by Beach Watch helped win a $7.7 million settlement after a spill within the San Francisco Bay and the Gulf of the Farallones and a $9.9 million settlement in 1996 after an oil spill along the central California coast.  These monetary settlements are used for restoration projects.