When I’ve talked about anthropogenic effects, I’ve been guilty of focussing far too much on climate change and land use. But our dependence on toxicants like pesticides also has a profound impact on ecosystems, freshwater ecosystems in particular. On her recent visit to NTN in Trondheim, I spoke to ecotoxicologist Dr. Marie-Agnes Coutellec about her research group’s work with pesticides, and the likely future for much of Europe’s aquatic life.

Sam Perrin (SP): As an ecotoxicologist, what are some of the more alarming trends you’ve seen in Europe recently?

Dr. Marie-Agnès Coutellec, Head of Ecotoxicology and Quality of Aquatic Environments Research Group, French National institute for Agricultural Research (M-AC): I believe that more than 50% of water bodies in Europe are contaminated with chemical toxicants. A lot of this is the result of exposure to chemicals typically used in agriculture, pesticides and so on. The trend here is that it’s not getting better, these environments are degrading, and we need to find solutions to protect these areas. It’s really a challenge, and a huge objective for scientists. We need to protect these environments and the services they provide to humanity.

SP: What is the focus of your lab?

M-AC: We work with pesticides. We want to protect natural systems against the potential effects of pesticides, that we predict by looking at toxicity testing in a lab. It’s essentially risk assessment, we try to forecast how chemicals will behave in nature and how they will affect natural populations.

SP: How does genomics help analyse these trends?

M-AC: We look at genomic markers to detect changes in gene expression brought on by exposure to toxicants. Thanks to new technologies in high throughput sequencing, we can access important genetic information that we couldn’t before. So changes in gene expression induced by toxicants, we can study this in the lab, but we can also now characterise populations by their genomics and identify biomarkers to test in the field. So genomics is used as a tool to see how a population will evolve with exposure to toxicants.

SP: What are some of the problems with assessing impacts?

M-AC: There are a lot. One way to assess the ecological risk associated with the use of chemicals is a prospective assessment. It’s done from a laboratory, using standardised testing which follows guidelines from the Organisation for Economic Co-operation and Development (OECD). But this is unrealistic and not ecologically relevant, because it doesn’t account for many things. Starting with genetic variation. We use for example, a daphnia clone and we extrapolate the answer from this clone to the whole list of invertebrates. It’s really not realistic.

We also have a retrospective way of assessing risk. That’s based on monitoring natural environments which are exposed already, in agricultural areas for example. The difficulty is to assess the cause and effect relationship, with correlational data. It’s observational data, so you measure toxicants and you measure typical phenotypic traits related to population fitness, with some ecological or evolutionary meaning. And you correlate responses to the level of various toxicants. But first we only measure what we are looking for. If you don’t think that it might be important to measure for a certain chemical, you will forget them and not account for them in your analysis. Especially for evolutionary biology or processes, what genetic markers tell you is the result of many combining factors and processes, evolutionary forces, natural selection, random genetic drift, maybe the effect of inbreeding for some species. So we miss the combined effect of many many factors. It’s not honest to always link changes to the presence of chemicals in a regressive manner.

SP: But new guidelines and increased concern are a good step forward, surely?

M-AC: Well yes, and all population level processes are notoriously difficult to assess and to determine in nature. You have to use a model, and a model is a simplification. And depending on the model you use you will have different outcomes, and so you will propose different predictions for the effect of your toxicants.

But it’s a good step forward to integrate more ecology into risk assessment. It’s a research area that is very interesting at the moment. And yet the question might be, do we have time to develop such research, considering the speed of the degradation of the environment.

SP: Do you have a best and worst case scenario for Europe’s aquatic environments in 20 years?

M-AC: The worst case would be that degradation continues to the point that the exposed environments cannot be recolonised by their native species. So the problem of habitat fragmentation may be added to the local contamination. It has to do with recovery. When a place is hardly contaminated, if it is alleviated then it can be recolonised by individuals from surrounding areas. This tends to mitigate the problem. But if this is made impossible because of other forces related to human activities, any structures which impede connectivity between habitats will lead to the worst case scenario.

Combinations of these toxicants are also a problem. We test toxicants one at a time, in our risk assessment. We know we shouldn’t exceed certain thresholds of some toxicants. But when you mix a lot of chemicals below the threshold of effect, that mixture can also have a negative effect. This is typically the case for endocrine receptors. When you have a mixture of these, even if they’re below a certain threshold, they can have uncontrollable effects on ecosystems.

The best case would be more careful ways of using toxicants. Pesticides for instance, we know that they are made to kill, so their use and effects should perhaps be monitored the most intensely.

Powai_Lake_Summer
Huge algal blooms such as this one are the result of increased use of fertilisers and pesticides. But ecological systems should be able to recover, given appropriate action and time. The question is, can we curtail our use of these chemicals? (Image Credit: Packerworld, CC BY SA 3.0)

SP: Do you think we should be hopeful that these ecosystems could be restored?

M-AC: The only questions is whether action is taken. That’s the main problem, the political part of the decision making. We scientists can help the decision making, but often we cannot go beyond this step. And it’s particularly important, because all these chemicals are released in the environment on purpose. It’s a side effect of industry, of human activity. We inject pesticides directly into the environment.

We also really need to take climate change when assess risk, because chemicals don’t act in nature like they do in the lab. Of course if we can reduce the use of pesticides, that would be the best thing we can do.

SP: You mentioned responsibility science, and the role that scientists play in affecting government policy. What advice would you give young scientists to orient them towards policy-shaping?

M-AC: My advice would be to develop models and approaches that are pragmatic and can lead to answers and results in the short-term, and that can convince politicians and policy makers. That might be tricky, because you have to keep scientific integrity. But I think we should be conscious that the environment is always changing and we cannot test for effects of an environment in 20 or 30 years. We have to keep in mind that environmental fluctuation and change is the rule now. That might be one perspective to develop and find pragmatic answers for.

We should also be communicating to the whole population, because people are more and more conscious that toxicants are everywhere, in everything we touch, eat, use. It all exposes us to toxicants.