long been recognized as a major cause of shellfish associated disease. It has also been determined that the indicator concept is inadequate for determining viral water quality. Methods were developed for the recovery and detection of viruses and studies implemented as a result of the European Economic Community recognizing a need for virological monitoring. Past and ongoing studies continue to evaluate virus contamination of the marine environment in the United States.
With a better appreciation of the limitations of the indicator system, new methods are being used to detect the presence of bacterial pathogens in coastal waters. In a study in Spain, Salmonella was detected in 32 percent of 256 samples collected from 21 bathing beaches along the north coast (Perales and Audicana 1989). Similarly, 16 sites in New York Harbor, the Hudson and East rivers offshore in the Hudson River plume, Chester River, and the upper Chesapeake Bay were sampled for the presence of Salmonella (Knight et al. 1990). Salmonellae were detected at 75 percent of the sites and in 50 percent of these samples, cultivation techniques failed to isolate the organism. Previous work has demonstrated that non-cultivatable organisms can remain infectious (Colwell et al. 1985, Grimes and Colwell 1986).
DePaola et al. (1990) investigated the occurrence of Vibrio parahaemolyticus in shellfish growing waters in Washington, California, Texas, Louisiana, Alabama, Florida, South Carolina, Virginia, and Rhode Island. They found no correlation of V. parahaemolyticus with fecal coliforms. Average densities were 3, 11, and 2.1 x 103/100 g of oyster in samples from the Atlantic, Gulf, and Pacific coasts, respectively. Concentrations were 100 times greater in oysters than in the water. Temperature appeared to be a significant factor in the seasonal and geographical distribution of this organism.
Newly recognized bacterial pathogens have also been studied in coastal estuarine waters. Listeria monocytogenes has been associated with foodborne gastroenteritis. This organism was detected in 62 percent of the samples in the Humboldt-Arcata Bay in California. The organism was found in 17 percent of the sediment samples and was not detected in oysters. It was suggested that domestic animals, such as horses and cattle, were responsible for the contamination (Colburn et al. 1990).
During the 1960s, several studies were published reporting the occurrence of enteroviruses in marine waters and shellfish (Metcalf and Stiles 1968, Bendinelli and Ruschi 1969). The next two decades brought with them improvements in the methods for the recovery and detection of enteric