Short-term arsenic exposure reduces diatom cell size in biofilm communities

Abstract

Arsenic (As) pollution in water has important impacts for human and ecosystem health. In freshwaters, arsenate (As(V)) can be taken up by microalgae due to its similarity with phosphate molecules, its toxicity being aggravated under phosphate depletion. An experiment combining ecological and ecotoxicological descriptors was conducted to investigate the effects of As(V) (130 μg L(-1) over 13 days) on the structure and function of fluvial biofilm under phosphate-limiting conditions. We further incorporated fish (Gambusia holbrooki) into our experimental system, expecting fish to provide more available phosphate for algae and, consequently, protecting algae against As toxicity. However, this protection role was not fully achieved. Arsenic inhibited algal growth and productivity but not bacteria. The diatom community was clearly affected showing a strong reduction in cell biovolume; selection for tolerant species, in particular Achnanthidium minutissimum; and a reduction in species richness. Our results have important implications for risk assessment, as the experimental As concentration used was lower than acute toxicity criteria established by the USEPA.

Potential effects of sediment contaminants on diatom assemblages in coastal lagoons of New Jersey and New York States

“…While the traditional tests typically measured growth or survival rates of various species depending on the dosage and length of the exposure to contaminants, a number of recent studies attempted to investigate mechanisms of toxicity by estimating gene expression (Kim Tiam et al, 2012;Moisset et al, 2015) and enzyme activities indicating which cell functions are affected Crespo et al, 2013). Laboratory and field experiments were also crucial for investigating effects of contaminants on the composition (Morin et al, 2010;Ricart et al, 2010) and diversity (Ricciardi et al, 2009) of algal communities and the function of the river biofilm ecosystems (Barral-Fraga et al, 2015). Several researchers used mesocosms and artificial streams to study freshwater diatom community composition changes in response to contaminant exposure (Pérès et al,1997;Gold et al, 2003;Kim Tiam et al, 2015).…”

The impacts of century-old, arsenic-rich, mine tailings on multitrophic level biological assemblages in lakes from the Cobalt, Ontario, Canada region

“…Of the diatom species analyzed in this study, Caloneis silicula, Tabellaria flocculosa, and observed, coinciding with the decline of mining pollutant levels in the lake back towards preindustrial levels (Cattaneo et al 2004). This current study, as well as both Barral-Fraga et al (2016) and Cattaneo et al (2004), therefore suggest that T. flocculosa is sensitive to increases in arsenic contamination, specifically.…”

River water quality assessment based on a multi-descriptor approach including chemistry, diatom assemblage structure, and non-taxonomical diatom metrics

“…Biodiversity descriptors such as Shannon's diversity index and species richness are regularly used as tools for investigating the biological integrity status of an ecosystem. For example, Verb and Vis (2000) reported significantly lower species richness and Shannon's diversity index at acid mine drainage sites than at reclaimed sites, while Barral-Fraga et al (2016) reported lower values for these metrics in diatom-dominated biofilms contaminated with arsenic. Similarly, the diatom assemblages collected in the present study showed lower species richness (10-23) and/or Shannon's diversity index (1.6-2.0) at polluted sites Ayang, Dalseo, Keumho, GJ-2, Soyo and Daejeon, but also at sites Gwangjugong and Gwangju-1.…”

“…It has been shown in numerous studies that small-sized species tend to dominate in metal-contaminated environments (Ivorra et al, 1999;Morin et al, 2008Morin et al, , 2012Tlili et al, 2011;Barral-Fraga et al, 2016). Decrease in diatom frustule size within a given species has also been reported as a response to metal stress.…”