Influence of laminar flow velocity and nutrient concentration on attachment of marine bacterioplankton

Abstract

A two‐stage continuous culture system was employed to study the influence of laminar flow velocity and nutrient concentration on the attachment of marine bacterioplankton to Pyrex surfaces. Both instantaneous Sorption and accumulation rates of bacterioplankton were significantly greater at high than low nutrient concentrations over a range of flow velocities, from 0.5 to 8.5 cm‐s‐1. Bacterial accumulation generally increased as a function of laminar flow velocity during 12 h trials. Under low flow — low nutrient regimes, concentrations of epibacteria were very low, probably due to low rates of advective transport to the surface and nutrient depletion within surface boundary layer. Experimental results demonstrate that both laminar flow velocity and nutrient concentration affect not only bacterial attachment but also subsequent growth, metabolic activity, and removal of epibacteria. To explain the observed accumulations of epibacteria, a model based on empirical results is presented to estimate rates of attachment and removal. This model is consistent with the hypothesis that the attachment rate is a function of laminar flow velocity, i.e. delivery of cells to the interface. However, removal rate, described as a shear‐related function under nutrient replete conditions, appears to be controlled by nutrient supply to the interface and the metabolic state of epibacteria under nutrient limiting conditions.