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

Size-fractionated bacterial production, abundance and a- and b- 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 ¼ 0.513; p < 0.05) whereas enzyme activity was significantly correlated to TSM (a-glucosidase: r ¼ 0.721 (p < 0.001); b-glucosidase: r ¼ 0.596 (p < 0.01)). Both a-glucosidase (r ¼ 0.514; p < 0.05) and b-glucosidase enzymes (r ¼ 0.598; p < 0.01) appeared to be involved in the degradation of CPCHO and Sal-PCHO, respectively. Changes in a-glucosidase/b-glucosidase ratios highlighted the varying composition of particulate organic matter. The bacterial uptake of 14C-labeled bacterial extracellular carbohydrate measured over 11 days showed a strong linear correlation between 14C-uptake and bacterial production using tritiated thymidine. The turnover rate of 14C-labeled carbohydrate-C was 0.52 d 1, higher than the estimated annual mean potential carbohydrate carbon turnover rate 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.