Interactions between a persistent organic pollutant (chlordecone) and earthworms

Chlordecone (C10Cl10O, CLD) is an organochlorine insecticide used between 1972 and 1993 in the French West Indies to control the banana weevil Cosmopolites sordidus. As it can remain in soil for decades or centuries depending on the soil type and is hardly degraded, CLD is considered as a persistent organic pollutant by the Stockholm Convention in 2009. This insecticide is known to cause health (e.g. increasing frequency of prostatic cancer), economic (e.g. some agricultural land are too highly contaminated with CLD to be used for cropping) and environmental problems (e.g. soil and water pollution). Then, it is essential to study its impact on functional biodiversity and to found mechanisms to degrade it.

My PhD about chlordecone – earthworms interactions started in November 2023 and takes place partly at the EMMAH unit, INRAE Avignon, partly in the GECO unit, CIRAD Martinique, supervised by Céline Pelosi and Mathieu Coulis, respectively. The aim is to characterise the effects of CLD and its transformation products on earthworms and to determine if earthworms can affect the fate of CLD, through its activity and interactions with microbial communities.

The impacts of CLD on earthworms has never been studied but based on the scientific literature on the effects of organochlorine pesticides on earthworms, we assume that earthworms can bioaccumulate CLD and at least some of its transformation products (according to their lipophile characteristic). We also hypothesise that this bioaccumulation can impact earthworms, especially some functional traits linked to their reproduction. Moreover, recent studies showed that soil bacteria cultivated in lab can degrade CLD into some of its transformation products. Then, we can hypothesise that earthworms can promote CLD degradation if they are in symbiosis with these bacterial populations.

In order to test these hypotheses, fields measurements and experiments under controlled conditions will be carried out in Martinique and in Avignon to study the relationships between the various components of bioavailability as well as the role of interactions between earthworms, CLD and microorganisms in the fate of CLD.