Biota of fecal bacteria concentrated in stable foam formed along water's edge in coastal zones

Abstract Since the coastal zone plays an important role in recreation, humans might be directly or indirectly exposed to pathogenic bacteria. Along the water's edge at the coast, stable yellowish brown foam generated by breaking waves is observed frequently. We examined the foam, and determined the fecal bacteria count in coastal water, sand and the foam on the Miyazaki coast, Japan. Fecal coliform and fecal streptococcus counts in the foam were markedly higher than those in the coastal water and sand. Furthermore, the concentration of dissolved organic carbon in the foam was much higher than that in the coastal water. We concluded that the fecal bacteria were concentrated in the foam formed by bubbles generated in the water and that the dissolved organic substances exhibit surface activity. In addition, the main species of fecal streptococcus in the foam was enterococcus faecium, which is often used as an indicator of fecal pollution.