Abstract
Copper (Cu) pollution in coastal areas is a worldwide threat for aquatic communities. This study aims to demonstrate the usefulness of the DNA metabarcoding analysis in order to describe the ecotoxicological effect of Cu at environmental concentrations on marine periphyton. Additionally, the study investigates if Cu-induced changes in community structure co-occurs with changes in community functioning (i.e., photosynthesis and community tolerance to Cu). Periphyton was exposed for 18 days to five Cu concentrations, between 0.01 and 10 μM, in a semi-static test. Diversity and community structure of prokaryotic and eukaryotic organisms were assessed by 16S and 18S amplicon sequencing, respectively. Community function was studied as impacts on algal biomass and photosynthetic activity. Additionally, we studied Pollution-Induced Community Tolerance (PICT) using photosynthesis as the endpoint. Sequencing results detected an average of 9,504 and 1,242 OTUs for 16S and 18S, respectively, reflecting the high biodiversity of marine periphytic biofilms. Eukaryotes represent the most Cu-sensitive kingdom, where effects were seen already at concentrations as low as 0.01 μM. The structure of the prokaryotic part of the community was impacted at slightly higher concentrations (0.06 μM), which is still in the range of the Cu concentrations observed in the area (0.08 μM). The current environmental quality standard for Cu of 0.07 μM therefore does not seem to be sufficiently protective for periphyton. Cu exposure resulted in a more Cu-tolerant community, which was accompanied by a reduced total algal biomass, increased relative abundance of diatoms and a reduction of photosynthetic activity. Cu exposure changed the network of associations between taxa in the communities. A total of 23 taxa, including taxa within Proteobacteria, Bacteroidetes, Stramenopiles, and Hacrobia, were identified as being particularly sensitive to Cu. DNA metabarcoding is presented as a sensitive tool for community-level ecotoxicological studies that allows to observe impacts simultaneously on a multitude of pro- and eukaryotic taxa, and therefore to identify particularly sensitive, non-cultivable taxa.
Highlights
Copper (Cu) pollution in coastal areas is mainly associated with domestic and industrial activities (Parks et al, 2010; Oursel et al, 2013; Misson et al, 2016), and the use of Cu-based antifouling paints on ship hulls (Yebra et al, 2004; Thomas and Brooks, 2010), especially after the ban of tributyltin (TBT) in the late 1980s in France (Alzieu, 2000) and from 2003 to the rest of Europe (Yebra et al, 2004)
Cu exposure lasted 18 days, which is much longer than the generation time of studied microorganisms
Effects on community composition and function were observed at a Cu concentration of 0.06 μM, which is known to occur in the Swedish coastal environment (Egardt et al, 2018)
Summary
Copper (Cu) pollution in coastal areas is mainly associated with domestic and industrial activities (Parks et al, 2010; Oursel et al, 2013; Misson et al, 2016), and the use of Cu-based antifouling paints on ship hulls (Yebra et al, 2004; Thomas and Brooks, 2010), especially after the ban of tributyltin (TBT) in the late 1980s in France (Alzieu, 2000) and from 2003 to the rest of Europe (Yebra et al, 2004). Concentrations as high as 0.33 μM have been detected in San Diego Bay, USA (Schiff et al, 2007) or up to 0.41 μM in Toulon Bay, France (Briand et al, 2017). On the west cost of Sweden, Cu levels have been detected at concentrations up to 5 μg/L (0.08 μM) (Egardt et al, 2018), exceeding the environmental quality standard (EQS) for this region, i.e., the Kattegat sea where an EQS of 4 μg/L (0.07 μM) has been established (HVMFS 2015:4). Cu affects species composition in microbial communities, leading to a replacement of sensitive taxa with tolerant ones (Gustavson et al, 1999; Serra et al, 2009; Ancion et al, 2010). Detailed descriptions of Cu-sensitive and -tolerant taxa in environmental communities are currently lacking
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