MEPS 191:19-32 (1999)  -  doi:10.3354/meps191019

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

Fleur C. van Duyl1,*, Ben de Winder2,**, Arjen J. Kop1, Ute Wollenzien3

1Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
2Amsterdam Research Institute for Substances in Ecosystems, Microbiology, Nieuwe Achtergracht 127, 1018 WS Amsterdam, The Netherlands
3Netherlands Institute of Ecology, Centre of Estuarine and Coastal Ecology (NIOO-CEMO), PO Box 140, 4400 AC Yerseke, The Netherlands
*E-mail: **Present address: National Institute for Coastal and Marine Management, PO Box 8039, 4330 EA Middelburg, The Netherlands

ABSTRACT: Sediment bacterial production, abundance and β-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 β-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 β-glucosidase activity and water-extracted carbohydrates could explain 93% of the net changes in bacterial production during the submerged period. Water-extracted 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 diatom activities are indirectly coupled to benthic heterotrophic bacterial production. Bacteria do respond to tidal variations in organic compounds, and water-extracted carbohydrates are an important indicator.

KEY WORDS: Extracellular polymeric substances · Carbohydrates · Benthic bacterial production · Bacterial abundance · β-glucosidase activity · Cohesive sediments · Diatoms · Ems-Dollard estuary

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