Patterns of Microbial Heterotrophy Through Changing Environments in a Marine Sediment

Publisher Website
Google Scholar
Abstract
Heterotrophic activity was measured through a vertical profile in sediments from Halifax Harbor [Nova Scotia, Canada] using 14C labeled glucose, glutamate and lactate as substrates. A modified heterotrophic potential method was used to detect the amount of label that was converted to low molecular weight metabolites, and the amounts respired to CO2 and incorporated into cellular material. For all 3 substrates, total uptake was greatest at the transition from aerobic to anerobic sediments (40 cm subbottom). The percentage of the total uptake respired reflected the predominant type of heterotrophic metabolism at the various horizons, with the highest values occurring above aerobic respiration and below sulfate reduction.sbd.the 40 cm horizon. Incorporation of the substrates into cellular material was low for both glutamate and lactate (< 5%) but averaged approximately 30% for glucose. For all 3 substrates tested, low molecular weight metabolites represented a significant portion of the substrate uptake at many horizons (approximately 50% at 40 cm). Data are presented indicating that the observed increase in heterotrophic activity at 40 cm subbottom may be due to chemoautotrophic organic C production at this horizon.