Linkage Between Dissolved Organic Matter Transformation, Bacterial Carbon Production, and Diversity in a Shallow Oligotrophic Aquifer: Results From Flow-Through Sediment Microcosm Experiments

Hofmann, Roland; Uhl, Jenny; Hertkorn, Norbert; Griebler, Christian

doi:10.3389/fmicb.2020.543567

Cited by 27 publications

(15 citation statements)

References 103 publications

(160 reference statements)

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“…Some research however shows that both subsurface heterogeneity and input variation affect subsurface microbial community structure. Schwab et al (2017), Zhou et al (2012), and Hofmann et al (2020) linked changing diversity of microbial communities in groundwater with spatio-temporal variation in the groundwater physico-chemical quality. McGuire et al (2000) and Benk et al (2019) linked changing composition of terminal electron acceptors and of dissolved organic matter (DOM) in groundwater with surficial events, respectively.…”

Section: Introductionmentioning

confidence: 99%

Predicting the impact of spatial heterogeneity on microbially mediated nutrient cycling in the subsurface

et al. 2022

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Abstract. The subsurface is a temporally dynamic and spatially heterogeneous compartment of the Earth's critical zone, and biogeochemical transformations taking place in this compartment are crucial for the cycling of nutrients. The impact of spatial heterogeneity on such microbially mediated nutrient cycling is not well known, which imposes a severe challenge in the prediction of in situ biogeochemical transformation rates and further of nutrient loading contributed by the groundwater to the surface water bodies. Therefore, we used a numerical modelling approach to evaluate the sensitivity of groundwater microbial biomass distribution and nutrient cycling to spatial heterogeneity in different scenarios accounting for various residence times. The model results gave us an insight into domain characteristics with respect to the presence of oxic niches in predominantly anoxic zones and vice versa depending on the extent of spatial heterogeneity and the flow regime. The obtained results show that microbial abundance, distribution, and activity are sensitive to the applied flow regime and that the mobile (i.e. observable by groundwater sampling) fraction of microbial biomass is a varying, yet only a small, fraction of the total biomass in a domain. Furthermore, spatial heterogeneity resulted in anaerobic niches in the domain and shifts in microbial biomass between active and inactive states. The lack of consideration of spatial heterogeneity, thus, can result in inaccurate estimation of microbial activity. In most cases this leads to an overestimation of nutrient removal (up to twice the actual amount) along a flow path. We conclude that the governing factors for evaluating this are the residence time of solutes and the Damköhler number (Da) of the biogeochemical reactions in the domain. We propose a relationship to scale the impact of spatial heterogeneity on nutrient removal governed by the log10Da. This relationship may be applied in upscaled descriptions of microbially mediated nutrient cycling dynamics in the subsurface thereby resulting in more accurate predictions of, for example, carbon and nitrogen cycling in groundwater over long periods at the catchment scale.

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Section: Introductionmentioning

confidence: 99%

Predicting the impact of spatial heterogeneity on microbially mediated nutrient cycling in the subsurface

et al. 2022

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“…1 Location of the study area within Styria (green boundaries), and Salzburg, as well as the sub-regions within the Mur valley (The Upper Mur valley, Lungau, Aichfeld, Middle Mur valley, Murdurchbruchstal, Grazer Feld, Leibnitzer Feld, and Lower Mur valley). The position of sampling sites of groundwater and surface water along the river Mur and its tributaries is indicated by black dots the DOM is usually composed of recalcitrant, humic compounds derived from the surface with a comparatively small contribution of fresh microbially produced DOM (Gooddy and Hinsby 2009;Hofmann et al 2020;Shen et al 2015). Furthermore, we hypothesize that in general the increased inputs of organic matter from the surface can cause changes in groundwater DOM quality either directly, or indirectly via the stimulation of biological productivity.…”

Section: Originalarbeitmentioning

confidence: 98%

Application of the D-A-(C) index as a simple tool for microbial-ecological characterization and assessment of groundwater ecosystems—a case study of the Mur River Valley, Austria

Retter

Griebler

Haas

et al. 2021

Österr Wasser- und Abfallw

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The assessment and monitoring of the ecological quality and status of groundwater is a timely issue. At present, various assessment tools have been developed that now await application and validation. One of these, the D‑A‑C index, evaluates the microbiological-ecological quality of groundwater based on of prokaryotic cell counts, microbial activity measurements, and the qualitative characterization of dissolved organic carbon (DOM). The purpose of this paper is to illustrate the different ways of application of the D‑A-(C) index making use of a recently collected data set (n = 61) from the river Mur valley, Austria. First, we present an extension of the D‑A-(C) index by including measurements of dissolved organic matter quality (DOM) derived from fluorescence spectroscopy as additional variables to supplement the analysis of microbial cell density and activity levels. Second, we illustrate how the definition of a reference status for a ‘good’ microbiological-ecological state can improve the analysis and allow for a more sensitive and accurate detection of impacts on groundwater ecosystems. Based on our results, we advocate that the analysis be performed by making use of expert knowledge for the definition of reference sites to which target sites are to be compared.

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“…Even when present in higher concentrations, much of the organic matter in groundwaters may be non-labile (Hofmann et al, 2020), leading to nutrient limitation. Dissolved oxygen concentrations in groundwater may vary from <0.3 to >3.0 mg/L (Malard & Hervant, 1999), and decrease with distance from exchange zones with surface aquatic and terrestrial systems.…”

Section: Environmental Fac Tor S S Haping Tr Ait D Iver S It Y In G R...mentioning

confidence: 99%

“…For example, dissolved organic matter concentrations in pristine groundwaters are typically 0.2–2 mg/L (Thurman, 1985), with the median global dissolved organic carbon concentration in groundwater being 1.2 mg/L (McDonough et al, 2020) compared to 5.7 mg/L in lake waters (Sobek et al, 2007). Even when present in higher concentrations, much of the organic matter in groundwaters may be non‐labile (Hofmann et al, 2020), leading to nutrient limitation. Dissolved oxygen concentrations in groundwater may vary from <0.3 to >3.0 mg/L (Malard & Hervant, 1999), and decrease with distance from exchange zones with surface aquatic and terrestrial systems.…”

Section: Environmental Factors Shaping Trait Diversity In Groundwatersmentioning

confidence: 99%

Invertebrate traits, diversity and the vulnerability of groundwater ecosystems

et al. 2022

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Groundwater comprises the largest freshwater ecosystem on the planet. It has a distinct regime of extreme, yet stable environmental conditions that have favoured the development of similar morphological and functional traits in the resident invertebrate fauna (stygofauna). The analysis of community traits is increasingly used as an alternative to taxonomy‐based assessments of biodiversity, especially for monitoring ecosystem status and linking the functions of organisms to ecological processes, yet it has been rarely applied to stygofauna and groundwater ecosystems. In this paper, we review the variation in functional traits among the invertebrate fauna of this important ecosystem. We focus on the stygofauna and processes of alluvium and fractured rock aquifers that are typified by small voids and fissures that constrain the habitats and environmental conditions. As a first step, we compare trait variability between groundwater and surface water invertebrate communities and then examine the significance of the ranges of these traits to the vulnerability of the ecosystem to change. Fifteen potentially useful functional traits are recognised. Eight of these have narrower ranges (i.e. exhibit fewer states, or attributes, of a particular trait) in groundwater than they do in surface water. Two traits have wider ranges. Our synthesis suggests that the relative stability of groundwater environments has led to low trait variability. The low biomass and low reproductive rate of stygofauna suggest that recovery potential following disturbance is likely to be low. For the purposes of both improved understanding and effective management, further work is needed to document additional functional traits and their states in groundwater fauna, enabling a better understanding of the relationship between response and effect traits in these ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

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Linkage Between Dissolved Organic Matter Transformation, Bacterial Carbon Production, and Diversity in a Shallow Oligotrophic Aquifer: Results From Flow-Through Sediment Microcosm Experiments

Cited by 27 publications

References 103 publications

Predicting the impact of spatial heterogeneity on microbially mediated nutrient cycling in the subsurface

Predicting the impact of spatial heterogeneity on microbially mediated nutrient cycling in the subsurface

Application of the D-A-(C) index as a simple tool for microbial-ecological characterization and assessment of groundwater ecosystems—a case study of the Mur River Valley, Austria

Invertebrate traits, diversity and the vulnerability of groundwater ecosystems

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