Surprisingly, low concentration of toxic chemical products in rivers –from fungicides to antidepressants- can change the swimming and feeding behaviours in some creatures, according to a new research study led by experts from the University of Barcelona and the University of Portsmouth (United Kingdom). Also, the effects can be unexpected depending on the kind of toxin mix, according to this study published in the journal Environmental Pollution.
The new study is signed by the experts Isabel Muñoz, Nuria de Castro-Català and Juan Luis Riera, from the Faculty of Biology of the University of Barcelona, and Alex Ford, from the Institute of Marine Sciences of the University of Portsmouth, and it puts emphasis on the need to consider both low doses and mixed toxicity tests in the chemical risk evaluation of products that enter aquatic ecosystems.
A cocktail of pollutants in rivers: a risk for life and health
It is known that in Europe, Asia, Australia and South America, water courses have high levels of fungicide compounds that are spread in agricultural areas (rice, oat, wheat, potato, garlic and citrus, etc.). However, antidepressants are also found in urban rivers worldwide, and marine freshwater environments. These chemical products get to the water environment –they are not completely cleaned in waste water treatment plants- and can pile up in some fish’s brains. Although toxicity tests for new chemicals are common, so far the effect of the combination of different toxins was not well known.
“Most world urban waterways receive a cocktail of pollutants –from agriculture runoffs to human sewage- with high drug concentrations (antidepressants, etc.)” says Professor Alex Ford. “These cocktails might not kill marine species, but we are worried about the sub-lethal effects of some of these pollutants. There can be thousands of different chemical products in our rivers and seas, and even though they might not be lethal, these pollutants can damage the aquatic ecosystems’ health”.
“These results show the importance of understanding and knowing about the impact of complex pollutant mixes. One of the big enigmas for environmental toxicologists is how to determine or predict the effects of each combination of chemical products when thousands are released to the environment and many had a limited toxicity assessment” warns Professor Alex Ford.
The long journey of antidepressants and fungicides in the environment
In the study, researchers analysed in the laboratory, the effect of two pollutants –an antidepressant and a fungicide- in amphipods, shrimp-like crustaceans. According to the lecturer Isabel Muñoz, from the Department of Evolutionary Biology, Ecology and Environmental Sciences of the University of Barcelona, “this study shows the effects of pollutants (fungicides and antidepressants) -found in river waters, mixed and in low concentrations- on the behaviour of the freshwater shrimp (Gammarus pulex). This crustacean, common around the aquatic systems, reduces food intake (leaf litter) and speeds up its swimming when in presence of toxins. Although effects are not lethal, they can be significant in the food web and the ecosystem functioning”.
According to Professor Ford, “what shocked us was to verify the effects on feed and swimming speed in amphipods, even at low pollution levels. The experiment with fungicides is interesting because many are used in agriculture and in our shampoos and lotions. In particular, freshwater shrimps prefer to eat leaf litter in river beds after those being occupied by fungus. In this situation, with all fungicides in the water, leaves would be less tasty to the amphipods, and that was the case, since they ate less. However, antidepressants made them eat less, which is an effect we had not predicted”.
“The study on swimming behaviour –says Ford- proved that animals swam faster after being exposed to fungicides and antidepressants. However, when they were exposed to both elements, like it usually happens in the natural environment, the cocktail made them to swim slower. The alteration of swimming or feeding behaviours can have important effects on growth, breeding and survival of these creatures which are important in the food chain”. Previously, other studies by Professor Ford had showed that antidepressants made small crustaceans to swim for a longer time to increase their predation chances.
“The way in which an animal eats and moves is a sensitive indicator to detect the sub-lethal impact on organisms that are probably important in other areas of the food chain and our ecosystem” warn the authors.
Globaqua project: improving water management practices
This new study published in the journal Environmental Pollution was funded by the EU Seventh Program through Globaqua project, a multidisciplinary consortium of twenty-one organization in which experts on the fields of hydrology, chemistry, ecology, ecotoxicology, economy, sociology, engineering and modelling take part. The University of Barcelona is participating in this project funded by the EU under the supervision of the lecturer Isabel Muñoz.