Does climate change enhance the nanoparticle toxicity of freshwater biofilms?

Periodic Reporting for period 1 - NanoToX (Does climate change enhance the nanoparticle toxicity of freshwater biofilms?)

Okres sprawozdawczy: 2017-01-09 do 2019-01-08

Aquatic ecosystems are threatened by multiple environmental stressors including pollutants and climate change. Considerable progress has been made in understanding the environmental impact of many stressors in recent years, yet new, potentially powerful toxicants such as engineered nanoparticles (ENPs) continue to emerge and their widespread use ensures they reach aquatic systems wherein their effects remain poorly understood. The release of ENPs into the environment is accelerating, and as the global climate warms, the combined effects of both stressors (ENP + temperature increase) could have significant consequences for aquatic life. As a major step towards understanding the climate change-enhanced environmental impacts of ENPs in aquatic ecosystems, the NanoToX project focused on investigating the responses of fluvial biofilms - microbial communities that drive aquatic primary production and respiration and thus, control nutrient conditions and water quality - as key points of ENP entry into aquatic food webs.

The goal of the NanoToX project was to elucidate how much river warming will affect fluvial biofilms at molecular, functional and structural levels, and how the presence of environmental concentrations of ENPs may further stress the communities. This objective was achieved through an innovative, interdisciplinary approach using an array of methods from the fields of ecotoxicology (ecology and toxicology), molecular, functional ecology and nanotechnology.

Project results are providing and will provide valuable information to underpin current updates to European legislation, ENP industry and will address social challenges relating to water security and climate change. Importantly, the research outputs are also contributing to one of the major priorities of the European research agenda, which, focuses on understanding interactions between climate, emergent pollutants (ENP), fluvial ecosystems and human activities in order to address environmental change issues in an integrated way (WFD 2000/60/EC). European society will benefit from new and relevant information regarding aquatic systems health (currently and in the future) through detecting the potential combined risk of ENP and TºC, and improving risk assessment/management and water quality of our rivers from where water is taken for several activities (e.g. drinking-water and industrial activities) and where a large number of recreational activities occur (e.g. fishing, sports).

To achieve the aim of the project, different work packages were designed: to develop and/or adapt biological methodology for biofilm (WP1), to study the biofilm responses to temperature (TºC) increase (WP2), to assess ENP impact on biofilms under current climate conditions (WP3) and the impact of warming on AgNP properties and toxicity to biofilms (WP4), and finally, to perform molecular analyses to get the broad biofilm microorganisms diversity (WP5).

Throughout a huge mesocosms experiment, the first of its kind at the University of Birmingham, biofilms were exposed to low concentration of ENPs with current and expected TºC (18ºC vs. 25ºC). The experiment involved 40 flumes of 60 L each, 20 set at 18ºC and 20 set at 25ºC, with 4 different pollutant treatments each: (i) control, (ii) silver ENPs (AgNP, pristine ENP), (iii) silver sulphide ENM (Ag2SNP, aged ENP) and (iv) silver nitrate (AgNO3, ionic control Ag+). To assess differences in temporal scales, water and biofilm samples were sampled just before adding the toxicants (0h) and after 1 and 3 days (acute effects), and after 14 and 30 days (chronic effects). Functional and structural analyses were performed according to the protocols stablished in the framework of the project. ENP ageing and characterisation were done in the University laboratories.

Project results highlight the ENP particulate effects compared to those from dissolved ions (AgNP vs. Ag+), despite the ENPs being agglomerated in the systems (e.g. ENP long term effects vs. Ag+ ephemeral effects on algal diversity). AgNPs cause negative effects on biofilm respiration and on all diatoms forms. However, AgNP kept or increased algal biomass and photosynthetic activity. Phosphatase activity (related with phosphate degradation) was affected by Ag2SNP. These results are important since in theory these aged and unreactive ENP “should not cause” any biological effects.

An increase of 6ºC caused an enhancement of algal biomass, photosynthetic activity, and some enzyme activities while others decreased. Microscopic images showed a homogenisation of biofilm community composition. These shifts should be taken seriously by river managers since they can modify the nutrient cycle in the freshwater systems and other ecosystem services, affecting the quality of water for the organisms who are living there but also for human health.

Finally, it is emphasised the need to review freshwater monitoring guidelines. It is extremely important to monitor water physicochemistry jointly with biological analyses to see if a system is polluted and how it is affected. For instance, biofilm is a powerful bioindicator of ecosystem health and can detect the bioaccumulation of metals even when levels are under the detection limit in water.
The plan for the dissemination of results included the publication of 3 research papers in international high impact journals. One will be submitted for publication soon. Results will continue to be disseminated in forthcoming conferences (i.e. SFS 2020), specific workshops (i.e. Biofilm workshop 2020) and public enjoyments activities organised (e.g. University Open days, Pint of Science, UoB Green Heart festival).

Without a doubt, this interdisciplinary project is a major first step in opening a new research line in climate-ecotoxicology, focussing specifically on biofilms as entry points to the food web and assessing ENP impacts under current and future climate scenarios. With all project results, the aim is to inform on-going policy debates in urban river management, responsible implementation of nanotechnologies and the Water Framework Directive (WFD), and will support the further development of WFD ecological assessment and revisions of regulatory frameworks.

The experimental results will be used to develop predictive tools/models for end-users to assess biofilm impacts and resilience and thus develop strategies to maintain ecosystems services now and under future climate and pollution scenarios. NanoTOX project results therefore are providing valuable information to underpin current updates to European legislation about this class of emerging chemicals and to help prevent higher ecosystem effects (e.g. loss of genetic, functional and structural biofilm diversity leading a loss of ecosystem services like nutrient and carbon recycling and thus water quality). It is furthermore providing the ENP industry with valuable information and a new set of biological tools to test ENP toxicity in order to ensure the safety of its products and thus facilitate their commercialization in a safe and responsible manner, underpinning European competitiveness. Finally, NanoTOX has addressed societal challenges relating to water problems in Europe, since the Eurobarometer on water shows that almost 75% of Europeans consider that the EU should propose additional measures to address water problems in Europe with the main focus of such measures on water pollution from industry and agriculture.

NanoTox project picture. Includes microcosms systems and biological approaches

Periodic Reporting for period 1 - NanoToX (Does climate change enhance the nanoparticle toxicity of freshwater biofilms?)

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