Environmental Concentrations of Copper, Alone or in Mixture With Arsenic, Can Impact River Sediment Microbial Community Structure and Functions

Abstract

In many aquatic ecosystems, sediments are an essential compartment, which supports high levels of specific and functional biodiversity thus contributing to ecological functioning. Sediments are exposed to inputs from ground or surface waters and from surrounding watershed that can lead to the accumulation of toxic and persistent contaminants potentially harmful for benthic sediment-living communities, including microbial assemblages. As benthic microbial communities play crucial roles in ecological processes such as organic matter recycling and biomass production, we performed a 21-day laboratory channel experiment to assess the structural and functional impact of metals on natural microbial communities chronically exposed to sediments spiked with copper (Cu) and/or arsenic (As) alone or mixed at environmentally relevant concentrations (40 mg kg-1 for each metal). Heterotrophic microbial community responses to metals were evaluated both in terms of genetic structure (using ARISA analysis) and functional potential (using exoenzymatic, metabolic and functional genes analyses). Exposure to Cu had rapid marked effects on the structure and most of the functions of the exposed communities. Exposure to As had almost undetectable effects, possibly due to both lack of As bioavailability or toxicity toward the exposed communities. However, when the two metals were combined, certain functional responses suggested a possible interaction between Cu and As toxicity on heterotrophic communities. We also observed temporal dynamics in the functional response of sediment communities to chronic Cu exposure, alone or in mixture, with some functions being resilient and others being impacted throughout the experiment or only after several weeks of exposure. Taken together, these findings reveal that metal contamination of sediment could impact both the genetic structure and the functional potential of chronically exposed microbial communities. Given their functional role in aquatic ecosystems, it poses an ecological risk as it may impact ecosystem functioning.

Evaluation of microbial shifts caused by a silver nanomaterial: comparison of four test systems

“…Based on the investigation of eight exoenzymes involved in various transformation steps (acid phosphatase, arylsulfatase, catalase, dehydrogenase, fluorescein diacetate hydrolase, protease, urease, and β-glucosidase), Chae et al [55] recommended β-glucosidase for the measurement of soil ecosystem health. The different temporal profiles of three enzymes (leucine aminopeptidase, phosphatase, and β-glucosidase) in the presence of metals during an incubation period of 21 days [56] and of four enzymes (acid phosphatase, arylsulfatase, fluorescein diacetate hydrolase, and urease) affected by fluorine [57] indicate that more than one enzyme is required for risk assessment applications.…”

Effectiveness of Dunaliella salina Extracts against Bacillus subtilis and Bacterial Plant Pathogens

“…Nowadays, recent European restrictions on the use of chemicals and antibiotics for the management of bacterial diseases in agriculture have been enacted [ 14 ]. Copper-based treatments, despite being non-environmentally friendly and having a negative impact on microorganisms in soil, phyllosphere, and rhizosphere, are principally adopted to control bacterial plant diseases [ 15 , 16 ], while host resistance and appropriate agronomic practices, such as seeds certification, irrigation, and fertilization, are the principal strategies for integrated control of bacterial diseases in fields. During post-harvest, the more effective solutions to prevent bacterial diseases are proper storage conditions and good handling practices such as cleaning and disinfestations of equipment [ 17 ].…”

Changes in sediment microbial diversity following chronic copper-exposure induce community copper-tolerance without increasing sensitivity to arsenic

“…Microorganisms are highly abundant in sediments, where they contribute to many ecological functions including the recycling of autochthonous and allochthonous organic matter (Schwarz et al, 2007), the production of greenhouse gas through anaerobic processes such as denitrification (de Klein et al, 2017) and methanogenesis (Billard et al, 2015), and the biodegradation of organic contaminants (Ghattas et al, 2017). Recently, Mahamoud Ahmed et al (2018) showed that environmental concentrations of Cu (i.e. about 40 mg kg−1 dw), alone or in a mixture with As at about the same concentration, can quickly impact the structure and a large set of functions of river benthic heterotrophic microbial communities.…”

“…Research is needed to characterize the mechanisms that drive metal-induced tolerance and cotolerance in sediment microbial communities. Testing a 21-day realistic scenario for exposure to Cu (nominal concentration of 40 mg kg−1 dw, which is representaMve of high levels of Cu contaminaMon in French freshwater sediments (INERIS, 2010)), we recently showed in a laboratory channel experiment that natural river sediment microbial communities were structurally and functionally impaired by Cu (Mahamoud Ahmed et al, 2018). In the present study, we sought to expand these findings by characterizing changes in diversity, resistance and tolerance of sediment microbial communities subjected to chronic Cu exposure, and the resulting sensitivity to exposure to another metal.…”