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Spatial microheterogeneity and selective microbial consumption of dissolved free amino acids in an oligomesotrophic lake


Krempaska, Natalia; Horňák, Karel; Silva, Marisa O D; Pernthaler, Jakob (2021). Spatial microheterogeneity and selective microbial consumption of dissolved free amino acids in an oligomesotrophic lake. Limnology and Oceanography, 66(10):3728-3739.

Abstract

We studied the cm to m scale spatial distribution of dissolved free amino acids (DFAA) in the upper epilimnion of oligomesotrophic Lake Zurich in 14 sampling campaigns over > 3 years and at various periods of the growing season. During each campaign, 10 sets of 10 simultaneously drawn samples (10 mL, 2 cm distance) were collected from 5 m depth. DFAA concentrations varied by one to > 3 orders of magnitude within sets, providing field evidence for DFAA release from macroscopic point sources and for substantial variability of the in-situ growth conditions of bacterioplankton metacommunities. There was a tight relationship between the median DFAA concentration per sampling campaign and the compositional heterogeneity of the 15 most common AA: their composition was similar in samples from campaigns with high median DFAA concentrations, indicating that spatial distribution patterns were mainly a result of physical mixing. By contrast, AA composition was spatially variable in campaigns with low median DFAA concentrations, and serine, aspartate, and glycine were disproportionally high in the 10% samples with highest DFAA concentrations. We hypothesized that pelagic bacteria would preferably target pulses of such locally overrepresented AA. Short-term incubations with radiolabeled tracers revealed substantially higher microbial uptake of serine and, to a lesser extent, aspartate, than of two amino acids with consistently low in situ concentrations (leucine, isoleucine). This illustrates a “preparedness” of the bacterioplankton to preferably incorporate those AAs that are more available in DFAA hotspots.

Abstract

We studied the cm to m scale spatial distribution of dissolved free amino acids (DFAA) in the upper epilimnion of oligomesotrophic Lake Zurich in 14 sampling campaigns over > 3 years and at various periods of the growing season. During each campaign, 10 sets of 10 simultaneously drawn samples (10 mL, 2 cm distance) were collected from 5 m depth. DFAA concentrations varied by one to > 3 orders of magnitude within sets, providing field evidence for DFAA release from macroscopic point sources and for substantial variability of the in-situ growth conditions of bacterioplankton metacommunities. There was a tight relationship between the median DFAA concentration per sampling campaign and the compositional heterogeneity of the 15 most common AA: their composition was similar in samples from campaigns with high median DFAA concentrations, indicating that spatial distribution patterns were mainly a result of physical mixing. By contrast, AA composition was spatially variable in campaigns with low median DFAA concentrations, and serine, aspartate, and glycine were disproportionally high in the 10% samples with highest DFAA concentrations. We hypothesized that pelagic bacteria would preferably target pulses of such locally overrepresented AA. Short-term incubations with radiolabeled tracers revealed substantially higher microbial uptake of serine and, to a lesser extent, aspartate, than of two amino acids with consistently low in situ concentrations (leucine, isoleucine). This illustrates a “preparedness” of the bacterioplankton to preferably incorporate those AAs that are more available in DFAA hotspots.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Plant and Microbial Biology
Dewey Decimal Classification:580 Plants (Botany)
Scopus Subject Areas:Physical Sciences > Oceanography
Life Sciences > Aquatic Science
Uncontrolled Keywords:Aquatic Science, Oceanography
Language:English
Date:1 October 2021
Deposited On:12 Oct 2022 08:35
Last Modified:27 Jun 2024 01:40
Publisher:American Society of Limnology and Oceanography
ISSN:0024-3590
OA Status:Green
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:https://doi.org/10.1002/lno.11912
PubMed ID:0000-0002-8986-1418
  • Content: Published Version
  • Licence: Creative Commons: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)