AME 70:261-272 (2013)  -  DOI: https://doi.org/10.3354/ame01658

ABSTRACT: We investigated whether attached bacteria affect the settling velocity of organic aggregates via modifications of the physical properties of aggregates, including density, porosity, and morphology. Model aggregates, prepared by mixing 2 different polysaccharides (fucoidan and chitosan), were incubated in coastal seawater passed through either 0.8 µm (AGG_0.8) or 0.2 µm (AGG_0.2) filters. After incubation for 48 h, AGG_0.8 were much more densely (3.2- to 10.1-fold) colonized by bacteria than AGG_0.2. Based on median settling velocities (W₅₀), as determined by laser in situ scattering and transmissometry, the W₅₀ of AGG_0.8 was lower (1.6- to 4.5-fold) than that of AGG_0.2 for a size class of 62 to 119 µm. Stokes model analyses indicated that this reduction in W₅₀ could be largely attributed to the higher porosities of AGG_0.8 (0.932-0.981) than those of AGG_0.2 (0.719-0.929). Our results support the notion that the modification of aggregate structure by attached bacteria (porosity enhancement) can be an important factor controlling the settling velocity of marine particles.

KEY WORDS: Bacteria · Aggregate · Settling velocity · Porosity · Marine environments

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Cite this article as: Yamada Y, Fukuda H, Inoue K, Kogure K, Nagata T (2013) Effects of attached bacteria on organic aggregate settling velocity in seawater. Aquat Microb Ecol 70:261-272. https://doi.org/10.3354/ame01658 Export citation Share:    Facebook - - linkedIn