Avoid moonlit bathing

A study of sixty beaches along the coast of southern California has revealed that water pollution varies with the lunar cycle, reaching the highest levels when tides are ebbing during new and full moons. The findings, reported in Environmental Science & Technology, could help beachgoers and managers better assess the potential risk of swimming. Alexandria Boehm of Stanford University and her colleagues in the Southern California Coastal Water Research Project found that in the full and new phases of the moon, levels of certain pathogenic bacteria were higher at the vast majority of the beaches studied. "Most sources of enterococci at beaches are unknown," Boehm says. "Because we found tidal signals in enterococci densities at beaches with no obvious point source, like storm drains and creeks, this suggests that there is a widespread tidally forced source of enterococci at beaches."