STRICTLY AEROBIC AND ANAEROBIC-BACTERIA ASSOCIATED WITH SINKING PARTICULATE MATTER AND ZOOPLANKTON FECAL PELLETS

Particulate material collected in sediment traps at 80 m depth in coastal northwestern Mediterranean waters, and fresh fecal pellets of copepods harvested in the surrounding water, were examined for the presence and activity of ammonia-oxidizing and methanogenic bacteria. Results provide the first evidence for the coexistence of living and active cells of methanogenic and nitrifying bacteria in either fresh zooplankton fecal pellets or large settling particles containing numerous large size fecal pellets. In addition, the presence of these 2 bacterial types in both copepods and the fecal pellets produced by them suggests that the bacterid probably originate from the digestive tract of zooplankton, most likely as ingested species for nitrifiers and enteric species for methanogens.