THE FIVE-YEAR RECRUITMENT OF MARINE LIFE AFTER THE 1971 SAN FRANCISCO OIL SPILL

Abstract

ABSTRACT On January 18, 1971, two Standard Oil tankers collided underneath the Golden Gate Bridge, releasing about 840,000 gallons of Bunker C fuel. An estimated 4.2 million to 7.5 million intertidal invertebrates, chiefly barnacles, were smothered by the oil. Five-year observations of marine life recruitment following the spill indicate that population densities of some marine species have significantly increased in the San Francisco Bay area intertidal zones at Sausalito and Duxbury Reef. With some fluctuations, the barnacles Balanus glandula and Chthamalus dalli have increased from July 1971 to May 1976—from 93 to 189 barnacles per dm2 at Sausalito and from nine to 34 per dm2 at Duxbury Reef. The large bed of mussels, Mytilus californianus, showed a steady rise from 5.9/m2 in April 1971 to 14.0/dm2 in July 1976. The density of mobile organisms, such as limpets, snails, crabs, and starfish, all show cyclical variations; some show an overall increase. The limpets, Collisella spp., which suffered high mortality during the spill have increased threefold over pre-oil counts. In 1975, some significantly low sample means were recorded for barnacles in Sausalito and for 18 composite species at Duxbury Reef, probably due to natural ecological forces. The five-year recruitment (1971-76), however, shows no evidence of lasting detrimental effects of Bunker C oil on the populations of marine life within the transect sites.