Combined effects of stress posed by global climate change and chemicals on aquatic ecosystems

Freshwater ecosystems may be affected by direct and indirect alterations of temperature and partial pressure of CO2 among other environmental variables associated with a global changing climate, henceforth Global Climate Change (GCC). Next to increasing mean temperatures, increased severity and frequency of extreme weather events, including heatwaves and warm spells are coherent findings for the end of this century. In addition to these natural, GCC-induced effects on aquatic ecosystems, variables like temperature can also interact with other existing anthropogenic stressors, such as chemicals. Modified temperature regimes are expected to modify the environmental fate of these compounds e.g. through manipulated compound properties.

Today, the joint effects of non-chemical GCC-related stressors (i.e. temperature, CO2) and chemicals on freshwater ecosystems continue to be understudied. Multiple stressor studies observe mostly effects on single species but population or community-level approaches that include ecological complexity and reality are rather rare.

We are interested in the effects of chemicals in the aqueous environment facing GCC. In our approach, we want to consider current and future temperature variability (i.e. daily temperature fluctuations) and extreme events instead of constant temperature regimes by applying the innovative transportable temperature and heat wave control engine (TENTACLE). Outdoor- and indoor-cosms together with the applied TENTACLE in distinct study regions of ECORISK2050 include high environmental realism and will provide new scientific insights and a better understanding of chemical effects on aquatic ecosystems within Europe in the light of GCC.

Establishing relationships between biological community composition and vulnerability to chemical

I am Francesco Polazzo, born in Italy and now placed in Spain at the IMDEA Water Institute (Alcalà de Henares, Madrid). During my PhD project I will be studying how chemical pollution together with Global Change related variables (temperature, eutrophication, hydrological fluctuations) impact freshwater communities and populations. I will do so by performing several micro- and mesocosm experiments, simulating lotic as well as lentic ecosystems.
How does community structure changes under multiple stressors? Which recovery trajectories do populations show? What are the consequences for ecosystem functioning? Which features confer stability to communities under multiple stress sources? Those are some of the questions I will try to address during my PhD. Alongside with experiments, I will develop a modelling framework aiming to understand how aquatic invertebrates’ vulnerability to chemicals will change due to climate change in the next 30 years at the European level.

Using chemical activity to understand effects of chemical mixtures on microbial communities in aquatic sediments

Organic chemical substances occurring in various mixture combinations are ubiquitous in the environment. Whereas most environmental assessments focus mainly on single compound´s effects which have been studied intensively, assessment methods of detecting impacts and risks of chemical mixtures in aquatic systems are still scarce [1]. The lack of knowledge is mainly due to the facts that it is 1) impossible to measure all chemicals´ concentrations in the environment due to technical limitations and costs, and 2) measuring all concentrations does not supply any information about the total concentration of mixtures, as concentrations are compound-specific and cannot be added up. Under these circumstances, risk and exposure assessment of toxic chemicals in the environment are exceedingly demanding [2]. The “chemical activity” approach provides a solution to master these confinements for chemical mixtures that are below their specific toxic concentration, by construing the concentration of various chemicals into a common, unitless currency [2]. We will expose Daphnia magna and microbial communities to chemical mixtures to understand how the concept of chemical activity can be used to assess chemical mixtures and therefore, help provide a new framework to evaluate chemical mixtures in areas with no point sources.

References
[1] Sobek A, Undeman E. 2019. Tunnel vision in current chemicals management cannot deal with the unknown risk of synthetic chemicals in aquatic systems. Acta Limnol. Bras. 31.
[2] Gobas FAPC, Mayer P, Parkerton TF, Burgess RM, van de Meent D, Gouin T. 2018. A chemical activity approach to exposure and risk assessment of chemicals. Environ. Toxicol. Chem. 37:1235–1251.

Modelling the interaction between climate change and chemical effects at different levels of biological organization

The future perspective of climate change demands an update for chemical risk assessment and highlights the urgent need to understand the effects caused by multiple stressors. In this research, effect mechanisms of chemicals and global climate change-related stressors will be investigated at different levels of biological organization (e.g., individual, population, community) of freshwater ecosystems. Starting with a literature review on both, experimental and modelling assessments, we will gather state-of-the-art data and methods studying the combined effects of temperature and chemicals in freshwater systems to inform subsequent investigations. To update effect modelling at the individual level, we will extend existing toxicokinetic-toxicodynamic modelling frameworks (e.g., GUTS1 and DEBtox2) with the ability to assess combined effects of pesticides and temperature for freshwater invertebrates. Subsequently, we will translate these individual responses to population and community levels using individual based models, like ChimERA3. For proper calibration and validation of these modelling exercises, we will use existing data gathered in the literature review, exposure studies conducted as part of this PhD project, as well as data produced in mesocosm experiments performed by researchers from the ECORISK2050 project. Additionally, theoretical modelling approaches will be explored, to investigate the role of intra- and inter-species relationships in the response to environmental changes at higher levels of biological organization. Finally, this research aims to support future ecological risk assessment with the development of advanced modelling tools enabling realistic assessment of combined effects of chemicals and global climate change on freshwater ecosystems in the future.

[1] General Unified Threshold Model of Survival
[2] Dynamic Energy Budget Theory
[3] De Laender, F. et al 2014. The ChimERA project: coupling mechanistic exposure and effect models into an integrated platform for ecological risk assessment. Environ Sci Pollut Res 21, 6263–6267