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Ecotoxicological assessments of biochar additions to soil employing earthworm species Eisenia fetida and Lumbricus terrestris.

ABSTRACT: Biochar is the degradation-resistant product generated by the pyrolysis of organic materials and is produced for the intended use of land application in order to promote carbon sequestration and soil improvement. However, despite the many potential benefits biochar application offers, it is important to quantify any ecological impacts that may result from soil amendment in order to avoid potentially causing negative effects upon soil biota which are crucial in the many ecosystem services provided by soil. Any impacts on earthworms in particular are important to evaluate because of their pivotal role in organic matter breakdown, nutrient cycling and soil formation. In this study, we conducted a series of ecotoxicological assays to determine lethal and sublethal (avoidance, mass change and moisture content) effects of heavy biochar applications that reflect levels that may be used in soil restoration efforts. Two earthworm species, Eisenia fetida, an epigeic species, and Lumbricus terrestris, an anecic species, were utilised as test organisms. Two types of biochar, produced from wheat straw and rice husk feedstocks, respectively, were applied to OECD artificial soil and to a natural soil (Kettering loam) at rates of up to 20% w/w. The influence of biochar application on soil porewater chloride, fluoride and phosphate concentrations was also assessed. The biochar applications induced only a subtle level of avoidance behaviour while effects on survival over a 4-week exposure period were inconsistent. However, death and physical damage to some individual earthworms at high biochar application rates were observed, the mechanisms and processes leading to which should be investigated further. Earthworm development (mean mass change over time) proved to be a more sensitive measure, revealing negative effects on L. terrestris at 10% and 20% (w/w) wheat biochar applications in OECD soil and at 20% (w/w) applications of both biochars in Kettering loam. The moisture content of E. fetida remained remarkably consistent across all treatments (~?82%), indicating that this is not a sensitive measure of effects. The high rates of biochar application resulted in increased chloride (2 to 3-fold) and phosphate (100-fold) concentrations in simulated soil porewaters, which has important implications for soil fertility and production but also for environmental management.

SUBMITTER: Elliston T

PROVIDER: S-EPMC7423795 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Ecotoxicological assessments of biochar additions to soil employing earthworm species Eisenia fetida and Lumbricus terrestris.

Elliston Tom T Oliver Ian W IW

Environmental science and pollution research international 20190222 27

Biochar is the degradation-resistant product generated by the pyrolysis of organic materials and is produced for the intended use of land application in order to promote carbon sequestration and soil improvement. However, despite the many potential benefits biochar application offers, it is important to quantify any ecological impacts that may result from soil amendment in order to avoid potentially causing negative effects upon soil biota which are crucial in the many ecosystem services provide ...[more]

PMID: 30796657

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Project description:The earthworm gut is an anoxic, saccharide-rich microzone in aerated soils. The apparent degradation of diverse saccharides in the alimentary canal of the model earthworm Lumbricusterrestris is concomitant with the production of diverse organic acids, indicating that fermentation is an ongoing process in the earthworm gut. However, little is known about how different gut-associated saccharides are fermented. The hypothesis of this investigation was that different gut-associated saccharides differentially stimulate fermentative microorganisms in gut contents of L. terrestris This hypothesis was addressed by (i) assessing the fermentation profiles of anoxic gut content microcosms that were supplemented with gut-associated saccharides and (ii) the concomitant phylogenic analysis of 16S rRNA sequences. Galactose, glucose, maltose, mannose, arabinose, fucose, rhamnose, and xylose stimulated the production of fermentation products, including H2, CO2, acetate, lactate, propionate, formate, succinate, and ethanol. Fermentation profiles were dependent on the supplemental saccharide (e.g., glucose yielded large amounts of H2 and ethanol, whereas fucose did not, and maltose yielded large amounts of lactate, whereas mannose did not). Approximately 1,750,000 16S rRNA sequences were affiliated with 37 families, and phylogenic analyses indicated that a respective saccharide stimulated a subset of the diverse phylotypes. An Aeromonas-related phylotype displayed a high relative abundance in all treatments, whereas key Enterobacteriaceae-affiliated phylotypes were stimulated by some but not all saccharides. Collectively, these results reinforce the likelihood that (i) different saccharides stimulate different fermentations in gut contents of the earthworm and (ii) facultative aerobes related to Aeromonadaceae and Enterobacteriaceae can be important drivers of these fermentations.IMPORTANCE The feeding habits of earthworms influence the turnover of elements in the terrestrial biosphere. The alimentary tract of the earthworm constitutes an anoxic saccharide-rich microzone in aerated soils that offers ingested microbes a unique opportunity for anaerobic growth. The fermentative activity of microbes in the alimentary tract are responsible for the in situ production of (i) organic compounds that can be assimilated by the earthworm and (ii) H2 that is subject to in vivo emission by the earthworm and can be trophically linked to secondary microbial events in soils. To gain insight on how fermentative members of the gut microbiome might respond to the saccharide-rich alimentary canal, this study examines the impact of diverse gut-associated saccharides on the differential activation of fermentative microbes in gut contents of the model earthworm L. terrestris.

Dataset Information

Ecotoxicological assessments of biochar additions to soil employing earthworm species Eisenia fetida and Lumbricus terrestris.

Publications

Ecotoxicological assessments of biochar additions to soil employing earthworm species Eisenia fetida and Lumbricus terrestris.

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