Tidal coupling between carbohydrate concentrations and bacterial activities in diatom-inhabited intertidal mudflats

Abstract

Sechment bacterial production, abundance and P-glucosidase activity were studied in relation to carbohydrate concentrations in diatom-inhabited intertidal mudflats during the tidal cycle in the Ems-Dollard estuary in summer 1996 During the diurnally emerged period significant increases in water-and EDTA-extracted carbohydrates, bacterial production and abundance in the sediment surface layer (0 to 2 mm) were established. Exposure had no effect on algal biomass (chlorophyll a), doubling times of bacteria or P-glucosidase activity in the surface layer. Net changes in water-extracted carbohydrates together with net changes in total and CTC (5-cyano-2,3-ditolyl tetrazolium chloride)stained bacteria accounted for 85% of the variations in net increase in bacterial production during the emerged period. During the submerged period significant decreases of water-extracted carbohydrate concentrations occurred. The changes in P-glucosidase activity and water-extracted carbohydrates could explain 93% of the net changes in bacterial production during the submerged period. Waterextracted carbohydrates derived mainly from live diatoms. The source of EDTA-extracted carbohydrates was less specific, but related to chlorophyll a and pheopigments. The results suggest that the net increases in water-extracted carbohydrates due to &atom activities are inbrectly coupled to benthic heterotrophic bacterial production. Bacteria do respond to tidal variations in organic compounds, and water-extracted carbohydrates are an important indicator.