Figure 2.

A typical profile of the current recorded by the phosphate selective microelectrode. A) The microelectrode was inserted into a densely populated area of the biofilm as confirmed by microscopy. B) The microelectrode equilibrated with interstitial phosphate concentrations within the biofilm. C) Phosphate was added to the seawater overlying the biofilm. D) The microelectrode current responded to the transport of the phosphate from the overlying seawater into the biofilm. E) The microelectrode was withdrawn from the biofilm and after equilibration the current reflected the phosphate in the overlying seawater. Experimental conditions summarized in Table 1.