Benthic bacterial biomass supported by streamwater dissolved organic matter

350 210 Stroud Water Research Center

Bott, T.L., L.A. Kaplan, and F.T. Kuserk. 1984. Microbial Ecology 10:335–344.

doi: 10.1007/BF02015558


Bacterial biomass in surface sediments of a headwater stream was measured as a function of dissolved organic carbon (DOC) flux and temperature. Bacterial biomass was estimated using epifluorescence microscopic counts (EMC) and ATP determinations during exposure to streamwater containing 1,788 μg DOC/liter and after transfer to groundwater containing 693 μg DOC/liter. Numbers of bacteria and ATP concentrations averaged 1.36×109 cells and 1,064 ng per gram dry sediment, respectively, under initial DOC exposure. After transfer to low DOC water, biomass estimates dropped by 53 and 55% from EMC and ATP, respectively. The decline to a new steady state occurred within 4 days from ATP assays and within 11 days from EMC measures. A 4°C difference during these exposures had little effect on generation times. The experiment indicated that 27.59 mg/hour of natural DOC supported a steady state bacterial biomass of approximately 10 μg C/g dry weight of sediment (from EMC determinations). Steady state bacterial biomass estimates on sediments that were previously muffled to remove organic matter were approximately 20-fold lower. The ratio of GTP∶ATP indicated differences in physiological condition or community composition between natural and muffled sediments.