Scale dependence of bacterioplankton patchiness

We provide evidence, based on the assessment of bactenal abundance in a series of samples representing geometncally decreasing volumes (5 1 to 0.25 ml), for the existence and scale dependence of patchiness in mixed-layer marine bacterioplankton.Our results demonstrate the existence of strong bacterioplankton patchiness at centimetre scale, the bacterioplankton community appearing as homogeneous when sampling at larger or smaller scales.We also provide, based on the inferred frequency distribution of bacterial densities, a representation of the in situ s p a t ~a l distribut~on of the bacterioplankton population sampled This dlstrlbution depicts the bacterioplankton community as composed of high density (> 107 bacteria ml-l) bacterial patches scattered within a 'matrix' of low bactenal density (105 bacteria ml-l).These results imply that the processes regulating bactenal abundance operate at centimetre scale.