Effects of volcanic pumice inputs on microbial community composition and dissolved C:P ratios in lake waters: an experimental approach.

MODENUTTI, B.,; BALSEIRO, E; BASTIDAS NAVARRO, M.,; LEE, Z.; SOUZA, MS,; CORMAN, J.; J. ELSER

MICROBIAL ECOLOGY

SPRINGER

Lugar: Berlin; Año: 2016 vol. 71 p. 18 - 28

0095-3628

Volcanic eruptions discharge massiveamounts of ash and pumice that decrease light penetration in lakes and lead to concomitantincreases in phosphorus (P) concentrations and shifts in soluble C:P ratios.The consequences of these sudden changes for bacteria community composition,metabolism and enzymatic activity remain unclear, especially for the dynamicperiod immediately after pumice deposition. Thus, the main aim of our study wasto determine how ambient bacterial communities respond to pumice inputs inlakes that differ in DOC and P concentrations and to what extent theseresponses are moderated by substrate C:P stoichiometry. We performed an outdoorexperiment with natural lake water from two lakes that differed in dissolvedorganic carbon (DOC) concentration. We measured nutrient concentrations, alkalinephosphatase activity (APA), and DOC consumption rates and assessed differentcomponents of bacterial community structure using next-generation sequencing ofthe 16S rRNA gene. Pumice inputs caused a decrease in the C:P ratio ofdissolved resources, a decrease in APA, and an increase in DOC consumption, indicatingreduced P limitation. These changes in bacteria metabolism were coupled with modificationsin the assemblage composition and an increase in diversity, with increases in bacterialtaxa associated with biofilm and sediments, in predatory bacteria, and in bacteriawith gliding motility. Our results confirm that volcanic eruptions have thepotential to alter nutrient partitioning and light penetration in receivingwaterways which can have dramatic impacts on microbial community dynamics.