Use of polar organic chemical integrative samplers to assess the effects of chronic pesticide exposure on biofilms

Abstract

The responses of aquatic organisms to chronic exposure to environmental concentrations of toxicants, often found in mixtures, are poorly documented. Here passive sampler extracts were used in experimental contamination of laboratory channels, to investigate their effects on natural biofilm communities. A realistic mixture of pesticides extracted from Polar Organic Chemical Integrative Samplers was used to expose biofilms in laboratory channels to total pesticide concentrations averaging 0.5 ± 0.1 μg l⁻¹. The level of exposure was representative of field conditions in terms of relative proportions of the substances but the exposure concentration was not maintained (decreasing concentrations between contamination occasions). The impact on the structural as well as the functional characteristics of the autotrophic and heterotrophic components was determined, using biofilm grown in uncontaminated conditions (reference site) and in sites exposed to pesticides (contaminated site). The exposure imposed did not significantly modify the structure or functions of reference biofilms, nor did it modify tolerance as measured by mixture EC₅₀ (EC₅₀ mix). In contrast, the communities from the more contaminated downstream section lost tolerance following decreased dose exposure, but community composition remained fairly stable. Overall, these results indicate that low levels of contamination did not lead to strong changes in community structure, and 14-day changes in tolerance seemed to depend mainly on physiological adaptation, suggesting that other environmental factors or longer-lasting processes prevailed. This study reports the first attempt to use passive sampler extracts as a realistic composite contaminant for experimental exposure of biofilms, with promising perspectives in further ecotoxicology studies.

Herbicide toxicity on river biofilms assessed by pulse amplitude modulated (PAM) fluorometry

“…In particular, high concentrations of the herbicides diuron, its main biodegradation product, 1-(3,4-dichlorophenyl)-3-methyl urea (DCPMU) and norflurazon (NFZ) have been recorded over several years at the downstream site on the river (Montuelle et al, 2010;Rabiet et al, 2010;Morin et al, 2012). Photosynthetic processes are highly sensitive to the presence of toxicants leading to an increase in their use as ecotoxicological endpoints in particular through the measurement of fluorescence parameters (Corcoll et al, 2012).…”

Effects of mixtures of dissolved and particulate contaminants on phototrophic biofilms: new insights from a PICT approach combining toxicity tests with passive samplers and model substances

“…Most of these studies were performed using extracts of POCIS that trap, among other organic substances, the most hydrophilic pesticides (for a review see Harman et al 2012). More recently, it has been shown that the combination of POCIS and bioassays could be used to assess the short-term effects of extracted pesticide mixtures on phototrophic biofilm communities, opening new perspectives to implement PICT-based approaches on pesticide mixtures (Pesce et al 2011a;Morin et al 2012;Kim-Tiam et al 2014a). One advantage of such an approach, besides considering mixtures, is that there is no need to make an a priori selection of the pesticides tested, thus giving an estimation of an integrative measure of the toxic potential of a group of compounds including unknown toxicants and metabolites, which are usually overlooked in ecotoxicological studies, especially when assessing effects at the community level (Pesce et al 2010b).…”

“…Pesticide mixture was extracted as previously described (Pesce et al 2011a) from six "Accumulative" POCIS (Morin et al 2012). Metal mixture was extracted from the resin-gel layer of 24 DGTs with 1 M HNO 3 (Suprapur, Merck), and DGT acid extracts were neutralized with NaOH (Suprapur, Merck) prior to assessing its toxicity as in Roig et al (2011).…”

Improving Toxicity Assessment of Pesticide Mixtures: The Use of Polar Passive Sampling Devices Extracts in Microalgae Toxicity Tests

“…POCIS extracts were used to assess the impacts of environmental pesticide mixtures with ecologically relevant bioassays with biofilms (Pesce et al, 2011; Morin et al, 2012c; Kim Tiam et al, 2014b). Toxicity testing of pesticide extracted from POCIS was recently performed on biofilms originated from different French rivers subjected to agricultural pressure (Table 4).…”

“…The works based on the PICT concept, using PE considered as a “blackbox” of contaminants, allowed to highlight previous exposure of the biofilms, or not, to these cocktails. The ecological significance of combined PICT and PE approaches proved to be relevant, for biofilms sampled from rivers presenting different contamination profiles in term of concentrations and/or nature of compounds detected (Pesce et al, 2011; Morin et al, 2012c; Kim Tiam et al, 2014b; Foulquier et al, 2015). The PICT responses of field biofilms were compared in three study sites subjected to distinct kinds of agricultural pressure (increasing vineyard occupation from upstream to downstream in Morcille river, distinct land use along the Ruiné river and growing cereal crops at the Trec river; Table 4).…”