Heterogeneity in bacterioplankton abundance from 4.5 millimetre resolutionsampling

A suite of pneumatically operated sampling devices was employed to investig ate distributional patterns of marine bacteria at the millimetre scale. Spa tial heterogeneity in bacterial abundance, or patchiness, was expressed as a coefficient of variation, and ranged from 5.5 to 75%. Discrete regions of enhanced bacterial abundance; as well as clear gradients in abundance acro ss entire sample arrays were observed, with changes in bacterial abundance of up to 16-fold observed across a distance of 32 mm. The role of turbulenc e in influencing bacterial distribution patterns was examined in a series o f laboratory experiments. Levels of heterogeneity were found to be up to 6. 5 times higher in stirred than unstirred water samples under laboratory con ditions. The gradients in bacterial abundance observed here suggest that sm all-scale processes operate within the marine microenvironment to create an d maintain spatial structure in the bacterioplankton community. We suggest that previously hypothesised nanoscale 'hot spots' and microzones exist onl y as maxima within a continuously variable distribution of bacteria within the marine environment.