Effectiveness of Escherichia coli as an Indicator in the Mitigation of Contaminated Urban Waterways by Asian Clam (Corbicula fluminea)

Abstract

An exotic freshwater clam, the Asian clam (Corbicula fluminea) , native to Southeast Asia, has been expanding its habitat in Japan in recent years. Clams are filter-feeders that are known to ingest bacteria and viruses as well as phytoplankton, which will either be digested or accumulated in their bodies. The potential for the Asian clams to remove Escherichia coli, a microbial indicator of fecal contamination, and bacteriophage MS2, a model of pathogenic viruses causing waterborne infections, was investigated in the following study. The clams collected from the Yamato River removed E. coli in water and in interstitial water between sands, but they were not able to remove MS2. The difference in size of the bacterial cells and bacteriophage particles was deduced to be responsible for the difference in removal. It is suggested that it is possible to decrease indicator counts of E. coli using freshwater clams, even though viruses can still remain in the environment.