Availability of dissolved organic carbon to bacterioplankton examined by oxygen utilization

Abstract

Oxygen consumption is used to study the dynamics of dissolved organic carbon (DOC) utilization by bacteria. Preliminary incubation experiments examining oxygen consumption and bacterial growth demonstrated that a small labile fraction of the total DOC pool typically supports bacterial metabolism. Bacterial growth and respiration rates were frequently fastest within the first few hours of incubation experiments suggesting that the pool of organic matter used for growth was rapidly consumed. Comparisons of bacterial production and respiration with total DOC concentrations suggested that approxinlately 1 to 3 % of the pool supports bacterial growth. The presence of a small labile component of the DOC pool suggests a close coupl~ng between bacteria and sources of substrate. Bacterial coupling to phytoplankton was examined in mesocosm experiments in which phytoplankton were enriched with nutrients and bacterial production and oxygen consumption were followed over diel cycles. Bacterial production, oxygen consumption and the availability of organic matter were highest during daylight, when phytoplankton production was assumed to be greatest. The effect of a varying carbon supply over diel cycles on bacterial growth efficiency was examined. During the mesocosm experiment, growth efficiencies were greatest during daylight when substrate availability was greatest. At several estuarine sites, efficiencies varied markedly over daily and seasonal temporal scales. These results suggest that growth efficiency is an important consideration when estimating the bacterial role in aquatic carbon cycles.

Habitat-specific distinctions in estuarine denitrification affect both ecosystem function and services

“…For the shallow-water estuarine habitats in our study system, we found a strong correlation between SOD and DNF in all habitats throughout the seasonal cycle. Measuring SOD is v www.esajournals.org a simple, low-cost alternative to directly measuring DNF (Coffin et al 1993, APHA 1998, Grenz et al 2003. This relationship has the potential to be used as a predictive tool for determining spatial and temporal scales of ecosystem services provided by estuarine habitats.…”

Linking diel patterns in community respiration to bacterioplankton in an oligotrophic high‐elevation lake

“…The diel variability observed in heterotrophic bacterioplankton growth rates tends to match the diel pattern in CR, with daytime rates higher than nighttime rates (Straskrabova and Fuksa 1982;Fuhrman et al 1985). This pattern is often explained as a bacterioplankton response to diel fluctuations in the labile dissolved organic matter (DOM) pool (Coffin et al 1993), but rarely is such a linkage between DOM and diel patterns demonstrated directly.…”

“…Diel variation in extracellular release has been interpreted as a driver of diel differences in bacterioplankton production or growth rates in marine (Fuhrman et al 1985) and freshwater (Straskrabova and Fuksa 1982) systems. While the more labile fraction of the DOM pool fueling this diel variability is rapidly turned over (Fuhrman 1990;Coffin et al 1993) and may make up a small fraction of the overall DOM pool (Coffin et al 1993;Carlson 2002), this fraction also provides a high proportion of overall carbon and nitrogen requirements to bacterioplankton (Fuhrman 1990). Using in situ experiments that captured these complex interactions between bacterioplankton and phytoplankton communities, Carrillo et al (2002) demonstrated coupling between primary and bacterial production mediated through bacterioplankton dependence on extracellular release at the seasonal time scale in an oligotrophic alpine lake.…”

Microbial efficiency in a meromictic reservoir

“…Thus in Piaseczno Reservoir the monimolimnion plays a role in settling the organic matter which can then only be decomposed via anaerobic processes. Analogous results, with regard to indexing microbial efficiency and the role of the monimolimnion in meromictic lakes, were presented by Coffin et al (1993) and Oremland et al (2000).…”

“…Processes not requiring available oxygen are the energy sources for bacteria capable of acquiring energy from oxidation of various compounds, such as sulphur compounds. In meromictic lakes divided into two layers, where one is saturated with oxygen (mixolimnion) and one is anaerobic (monimolimnion), the efficiency of microbial decomposition of organic matter is an important index of metabolic transformations in the environment (Coffin et al 1993, Kroer 1993, Del Giorgio and Cole 1998, Oremland et al 2000, Humayoun et al 2003. In many meromictic lakes sulphur compounds act as electron acceptors during cellular respiration, which can cause an accumulation of hydrosulphuric acid, exerting a negative influence on biological processes (Overmann et al 1996).…”