Poly--hydroxybutyrate accumulation as a measure of unbalanced growth of the estuarine detrital microbiota

The effects of variations in water composition on the metabolism of poly--hydroxybutyrate (PHB) by the estuarine microbenthos were examined in the laboratory. Changes in the PHB to lipid phosphate ratios observed in the field could be reproduced in the laboratory under conditions simulating common stresses in the estuarine environment. Acute anoxia or low pH depressed both the synthesis and catabolism of PHB without change in the lipid phosphate under conditions of zero growth. Balanced growth increased lipid phosphate but depressed PHB synthesis and stimulated PHB catabolism. Unbalanced growth induced by high salinity or by dark upland water, resulted in rapid accumulation of PHB, slowing of PHB catabolism and little change in lipid phosphate.