Poly(β-hydroxyalkanoate) accumulation in bacterioplankton from Lake Cisó (Spain)

The specific poly(β-hydroxyalkanoate) (PHA) content of the bacterioplankton from Lake Cisó (Spain) was measured at different depths. Phototrophic bacteria reach large populations in this lake and the PHA concentration changed seasonally according to their biomass. During summer stratification of the lake, phototrophic bacteria formed a metalimnetic peak. Bacterial counts were maximal at a depth of 1.5–2.0 m, whereas the PHA specific content reached a maximal value at 3.0–3.5 m. Since the limiting factor in this ecosystem is light availability, we assume that cells beneath the dense metalimnetic peak have unbalanced growth conditions and thus accumulate large amounts of PHA.Key words: bacterioplankton, PHA accumulation, Lake Cisó, light limitation.