Bacterial production, glucosidase activity and particle-associated carbohydrates in Dona Paula bay, west coast of India

Size-fractionated bacterial production, abundance and alpha- and beta- glucosidase enzyme activities were studied with respect to changes in hydrography, total suspended matter (TSM), chlorophyll a, particulate organic carbon and nitrogen ratio (POC:PON), 1.5 M NaCl-soluble and 10 mM EDTA-soluble carbohydrates (Sal-PCHO and CPCHO) and transparent exopolymeric particles (TEP) in the surface waters from July 1999-2000 at a shallow coastal station in Dona Paula Bay, west coast of India. The bulk of the total bacterial production and glucosidase activity were associated with particles (75% and >80%, respectively). Total bacterial production was linearly correlated to chlorophyll a (r = 0.513; p < 0.05) whereas enzyme activity was significantly correlated to TSM (alpha-glucosidase: r = 0.721 (p < 0.001): beta-glucosidase: r = 0.596 (p < 0.01)). Both alpha-glucosidase (r = 0.514: p < 0.05) and beta-glucosidase enzymes (r = 0.598; p < 0.01) appeared to be involved in the degradation of CPCHO and Sal-PCHO, respectively. Changes in alpha-glucosidase/beta-glucosidase ratios highlighted the varying composition of particulate organic matter, The bacterial uptake of 14 C-labeled bacterial extracellular carbohydrate measured over 11 days showed a strong linear correlation between C-14-uptake and bacterial production using tritiated thymidine. The turnover rate of C-14-labeled carbohydrate-C was 0.52 d(-1), higher than the estimated annual mean potential carbohydrate carbon turnover Fate of 0.33 +/- 0.2 d(-1). Our study suggests that carbohydrates derived from sediments may serve as an important alternative carbon source sustaining the bacterial carbon demand in the surface waters of Dona Paula Bay. (C) 2008 Elsevier Ltd. All rights reserved.