Moss and Peat Leachate Degradability by Heterotrophic Bacteria: The Fate of Organic Carbon and Trace Metals
Creators: name: Shirokova, Liudmila S.
name: Bredoire, Romain
name: Rols, Jean-Luc
name: Pokrovsky, Oleg S.
Publisher: name: Taylor & Francis
Year: 2016
Subjects: subject: Microbiology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: FOS: Earth and related environmental sciences
subject: Ecology
subject: Immunology
subject: FOS: Clinical medicine
subject: FOS: Clinical medicine
subject: Developmental Biology

description: The respiration of dissolved organic matter (DOM) by aerobic heterotrophic bacterioplankton in boreal surface waters is one of the major factors that regulate CO<sub>2</sub> exchange of lakes and rivers with the atmosphere in arctic and subarctic zones. The DOM that originates from topsoil leaching and vegetation degradation is brought to the lakes by surface flow and is subjected to coagulation and degradation by heterotrophic bacteria, which are well-established processes in the majority of boreal aquatic settings. The behavior of colloids and organic complexes of trace metals during this process is virtually unknown. In this work, we studied the interaction of two model heterotrophic bacteria, soil <i>Pseudomonas aureofaciens</i> and aquatic <i>Pseudomonas reactans</i>, with peat and <i>Sphagnum</i> moss leachates from the permafrost region under controlled laboratory conditions in nutrient-free media. The moss leachate was the better substrate for bacterial survival, with <i>P. reactans</i> exhibiting an order of magnitude higher live cell number compared with <i>P. aureofaciens</i>. In eight-day experiments, we analyzed organic carbon and ∼40 major and trace elements (TEs) during heterotrophic bacteria growth. The total net decrease in the concentration of dissolved organic carbon (DOC) was similar for both bacteria and ranged from 30 mg g<sub>wet</sub><sup>−1</sup> to ≤10 mg g<sub>wet</sub><sup>−1</sup> during 8 days for the moss and peat leachate, respectively. Despite significant evolutions of pH, DOC, dissolved inorganic carbon (DIC), and cell number, most major (Mg, K, and Ca) and TEs remained nearly constant (within ±30% of the control). Only Fe, Al, P, Zn, Mn, Co, and Ba and to a much lesser extent Cd, Pb, <i>Rare Earth Elements</i> (REEs), U, Ti, and Zr were affected (p −1 to µg L<sup>−1</sup> and followed the order DOC &gt;&gt; P &gt;&gt; Ba &gt; Zn ≥ Fe ≥ Al &gt; Mn &gt; Cu ≥ Sr &gt; Zr ≥ Ti &gt; Ni ≥ Co &gt; REEs ≥ U &gt; Hf∼Th, which reflected the abundance of the elements in the two substrates. Generally, the soil exopolysaccharide producing bacterium <i>P. aureofaciens</i> in the peat leachate had the greatest impact of the four combinations investigated in this study (two bacteria with two substrates). Under ongoing environmental changes in the boreal zone, the autochthonous processes of bacterioplankton activity are able to decrease the concentrations of a very limited number of TEs, including mainly Fe and several macro- (P) and micro- (Zn, Mn, and Ba) nutrients.