Synergy of Fresh and Accumulated Organic Matter to Bacterial Growth

Abstract

The main goal of this research was to evaluate whether the mixture of fresh labile dissolved organic matter (DOM) and accumulated refractory DOM influences bacterial production, respiration, and growth efficiency (BGE) in aquatic ecosystems. Bacterial batch cultures were set up using DOM leached from aquatic macrophytes as the fresh DOM pool and DOM accumulated from a tropical humic lagoon. Two sets of experiments were performed and bacterial growth was followed in cultures composed of each carbon substrate (first experiment) and by carbon substrates combined (second experiment), with and without the addition of nitrogen and phosphorus. In both experiments, bacterial production, respiration, and BGE were always higher in cultures with N and P additions, indicating a consistent inorganic nutrient limitation. Bacterial production, respiration, and BGE were higher in cultures set up with leachate DOM than in cultures set up with humic DOM, indicating that the quality of the organic matter pool influenced the bacterial growth. Bacterial production and respiration were higher in the mixture of substrates (second experiment) than expected by bacterial production and respiration in single substrate cultures (first experiment). We suggest that the differences in the concentration of some compounds between DOM sources, the co-metabolism on carbon compound decomposition, and the higher diversity of molecules possibly support a greater bacterial diversity which might explain the higher bacterial growth observed. Finally, our results indicate that the mixture of fresh labile and accumulated refractory DOM that naturally occurs in aquatic ecosystems could accelerate the bacterial growth and bacterial DOM removal.

Ultrahigh bacterial production in a eutrophic subtropical Australian river: Does viral lysis short‐circuit the microbial loop?

“…The flows of DOC into bacterial production and respiration are related by the bacterial growth efficiency (BGE) term that is defined as bacterial production/ (bacterial production + bacterial respiration) (Farjalla et al 2009b). Determining quantitatively the amount of readily degradable DOC supplied to the bacteria relies on sensitive and accurate measurements of bacterial production in situ.…”

“…In freshwater ecosystems, bacterial activity respires terrestrial dissolved organic carbon (DOC) and returns CO 2 to the atmosphere (Cole and Caraco 2001;Cole et al 2006;Farjalla et al 2009a). However, there are few reports that consider the quantitative significance of bacterial dynamics in lakes and rivers as major sources of CO 2 to the atmosphere (Richey et al 2002;Mayorga et al 2005;Cole et al 2007).…”

“…On the other hand, in temperate environments, allochthonous (outside the system) terrestrial particulate organic carbon is directly subsidizing river and lake food webs via zooplankton (Pace et al 2004;Cole et al 2006;Caraco et al 2010). In either scenario, there is little contribution to higher trophic levels from the heterotrophic bacterial production (Tanaka et al 2005;Cole et al 2006;Farjalla et al 2009b). …”

Interaction between resource identity and bacterial community composition regulates bacterial respiration in aquatic ecosystems

“…Differences in their leachates were also observed; e.g U. foliosa leachates showed high concentrations of soluble carbohydrates and lower phosphorus concentration than N. indica leachates (Suhett, 2007). Previous studies have shown that dissolved organic matter (DOM) from such species strongly affects bacterial respiration and growth (Stepanauskas et al, 2000;Farjalla et al, 2009). Only senescent leaves were collected because DOM leaching is more effective during plant senescence.…”

“…floating, emergent, submerged, floating-leaves) (Demars and Edwards, 2008). Different leachates have contrasting effects on microbial community processes (Wehr et al, 1999;Stepanauskas et al, 2000;Farjalla et al, 2009) and resource identity can have strong effects on BCC (Judd et al, 2006;Szabo et al, 2007;Kominoski et al, 2009).…”