Abstract
Aquatic organisms are increasingly exposed to lowering of environmental pH due to anthropogenic pressure (e.g. acid rain, acid mine drainages). Such acute variations trigger imbalance of fish-associated microbiota, which in turn favour opportunistic diseases. We used the tambaqui (Colossoma macropomum), an Amazonian fish tolerant to significant pH variation in its natural environment, to assess the response of fish endogenous microbiota to acute short-term acid stress. We exposed 36 specimens of tambaquis to acidic water (pH 4.0) over 2 consecutive weeks and sampled cutaneous mucus, feces and water at 0, 7 & 14 days. The 16S RNA hypervariable region V4 was sequenced on Illumina MiSeq. After two weeks of acidic exposure, fecal and skin microbiota taxonomic structures exhibited different patterns: skin microbiota was still exhibiting a significantly disturbed composition whereas fecal microbiota recovered a similar composition to control group, thus suggesting a stronger resilience capacity of the intestinal microbiota than cutaneous microbiota.
Highlights
Aquatic organisms are increasingly exposed to lowering of environmental pH due to anthropogenic pressure
The physiological response of Amazonian fishes exposed to acid stress has been documented on the tambaqui (Colossoma macropomum), the most commercially important fish in Brazil, that migrates annually from white water to black water streams to feed during the rainy season[28,29]
We hypothesized that exposure to short-term acid stress triggers a perturbation of the taxonomic structure of commensal microbiota, potentially followed by a replacement with opportunistic bacteria from the environmental water or rare endogenous strains that are more resistant to acidic conditions
Summary
Aquatic organisms are increasingly exposed to lowering of environmental pH due to anthropogenic pressure (e.g. acid rain, acid mine drainages). The resistance and resilience of ecosystems exposed to acidic rainfall relies on a multitude of abiotic and biotic characteristics from the environment: the presence of exogenous polyamines[24], local soil chemistry[25] or the ionic composition of the water, all of which potentially affecting the response of an ecosystem following acid precipitation. We hypothesized that exposure to short-term acid stress triggers a perturbation of the taxonomic structure of commensal microbiota (dysbiosis), potentially followed by a replacement with opportunistic bacteria from the environmental water or rare endogenous strains that are more resistant to acidic conditions. The impact of acidic stress on the taxonomic structure of the endogenous microbiota on teleosts has not been documented yet
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