Microplastics are transferred in a trophic web between zooplankton and the amphibian Axolotl (Ambystoma mexicanum): Effects on their feeding behavior

Abstract

Microplastics are contaminants that are often ingested, bioaccumulated, and transferred through food chain, affecting aquatic ecosystems. Zooplankton is susceptible to ingesting microplastics, so it is probably a vector that transfers microplastics to higher trophic levels. Cladocerans are a diet of amphibian larvae. Amphibians' survival is under threat worldwide due to their sensitivity to pollution. This work aimed to determine the transfer of zooplankton microplastics to Ambystoma mexicanum larvae (known as axolotl), for which we evaluated two responses in the first five weeks of development: 1) functional response of the larvae and 2) examination of their feces. Cladocerans were exposed to a diet of phytoplankton and microplastics to use them as food for axolotl larvae. Five axolotl larvae were randomly selected each week, each fed with a different concentration of cladocerans, and prey consumption was recorded for each larva. Finally, all the feces of the axolotls expelled after feeding were digested and examined under a light microscope. We found that microplastics were transferred from the cladocerans to A. mexicanum. Microplastics negatively affected the larval feeding behavior since the axolotls fed zooplankton exposed to microplastics consumed less prey than those of the control group. We also observed that microplastics were present in 78% of the feces. Microplastics reduce the feeding of juvenile A. mexicanum, an endemic amphibian of Mexico, in critical danger of extinction.