Bacterial enhancement of gel particle coagulation in seawater

摘要

Gel-like particles are ubiquitous in marine environments, affecting global carbon cycles, but the mechanisms controlling gel particle coagulation in seawater are not entirely clear. We investigated whether marine bacteria enhance the coagulation of gel particles. Gel particles composed of polysaccharides with an equivalent spherical diameter (ESD) of 0.01 cm were suspended in seawater contained in rotating tubes to examine time course changes in particle ESD and abundance. Marine bacterial assemblages strongly enhanced the coagulation of gel particles into large aggregates (ESD, 0.1 to 1 cm) over a period of 24 to 96 h. Catalyzed reporter deposition fluorescence in situ hybridization revealed that one group of bacteria that grew rapidly was affiliated with the genus Pseudoalteromonas. Experiments using Pseudoalteromonas spp. isolates indicated that 6 of 11 isolates enhanced gel particle coagulation. This enhancement differed greatly by species. High settling velocities, up to 270 m d(-1), were determined for the large aggregates. Our results demonstrate that bacteria can substantially enhance gel particle coagulation and the formation of fast-settling large aggregates in seawater.