Arsenic effect on gut microbiota of great tit nestlings and life history trait consequences
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Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
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Verkkojulkaisu
DOI
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Toxic metal(loid) pollution is a global challenge because of its persistent and hazardous nature. Anthropogenic activities such as smelting, mining, and agricultural practices release heavy metals and metalloids into surrounding ecosystems. Arsenic is a metalloid that accumulates in soil and passes to higher trophic levels through dietary exposure. The gut microbiome has crucial roles in host nutrition, immunity, and development. However, the effects of arsenic on the gut microbiota of wild bird nestlings under natural conditions remain understudied. This study investigated how experimental arsenic exposure affects the gut bacterial microbiota of nestlings of an insectivorous passerine, the great tit (Parus major), and examined associations between gut microbiota and nestlings’ growth. The experiment was conducted around the Harjavalta copper-nickel smelter in South-West Finland in 2015, at polluted areas (<2 km distance from smelter) and control areas (>5 km distance). Faecal samples, pooled from broods, were collected at Day 7 post-hatching from 53 broods across three experimental groups: arsenic-supplemented nestlings in clean control areas (As group, n = 16), nestlings exposed by copper smelter (pollution group, n = 22), and clean-area controls (control group, n = 15). The DNA extraction and 16S rRNA amplicon sequencing were performed in 2024. In this study, after downstream sequence data processing and subsequent statistical analyses, I found that gut bacterial communities were dominated by Pseudomonadota, Bacillota, and Actinomycetota across all groups, consistent with typical insectivorous passerine gut microbiota. No significant effects of experimental treatment were detected regarding bacterial alpha diversity (Shannon index and observed richness) or beta diversity, and there was no arsenic dose-response associated with alpha/beta diversity. Differential abundance analysis (ANCOM-BC2) identified three genera with significant treatment-associated differences: Brevundimonas was depleted in arsenic-exposed birds, while Neochlamydia and Paeniclostridium were enriched in the pollution group. However, all these taxa had low relative abundances (<1%)and Neochlamydia were markedly clustered in one study plot. In contrast to the arsenic results, the Shannon diversity was positively related to nestling body mass and wing length but not to fledging success. These findings suggest that the host developmental condition is a stronger driver of early-life gut microbiome than acute arsenic exposure at moderate doses. This highlights the context-dependency of pollution effects on avian gut microbiota.