In the first study of its kind, scientists have shown that climate change could amplify the negative effects of pollution from endocrine disrupting chemicals (EDCs) on aquatic wildlife. Climate change is seen globally as a major environmental risk, and when combined with chemical pollution and habitat loss, it has the potential to have a severe impact on wildlife populations.
The research, carried out by scientists from Bangladesh and the UK, including Professor Charles Tyler, an expert in EDCs, studied zebrafish (Danio rerio), which are a freshwater species native to the Indian subcontinent. Like many fish, reptiles and amphibians, the sex-determining mechanism in zebrafish is known to be modified by environmental factors, such as the temperature at which the egg develops. The study took place in a laboratory setting, with the zebrafish in the experiment representative of both outbred healthy populations and inbred endangered populations that lack genetic diversity.
Clotrimazole is a commonly used anti-fungal medication— used to treat conditions like athletes foot, but it also has endocrine disrupting properties, blocking oestrogen production. The researchers added clotrimazole to the tanks in high and low concentrations in order to represent high and low levels of EDC pollution respectively.
In order to replicate the effects that climate change, some of the zebrafish were kept at 28°C— the temperature currently found in wild zebrafish spawning ponds, and others were kept at 33°C— the average temperature predicted for the year 2100.
Results show that when conditions represented a warmer climate, high EDC pollution levels and inbred zebrafish, a huge 97% of zebrafish developed into males, with 82% of the outbred population developing into males. Even at lower concentrations of EDC pollution, when temperatures were high, the inbred fish still developed with more males (82%) than females. At current normal temperatures, the percentage of eggs developing into males when exposed to high EDC pollution were lower, being 81% and 60% for inbread and outbread populations respectively. Population modelling showed that population growth rates declined sharply at the higher temperature and high EDC pollution levels in response to more males, with a greater effects seen in inbred populations.
The results indicate that higher temperatures associated with climate change can amplify the effects of EDCs. The effects are likely to be most problematic in small, inbred populations whose sex is determined by environmental factors. This means that many endangered species are likely to be particularly under threat.
Though this is the first study to take into account the combined impact of climate change and EDCs, there is a vast amount of information on the effects of EDCs on wildlife, for more in-depth information see our wildlife publications.