We can't find the internet
Attempting to reconnect
Something went wrong!
Hang in there while we get back on track
Microplastic ingestion by an aquatic ciliate: Functional response, modulation, and reduced population growth
Summary
Researchers exposed a freshwater ciliate to varying microplastic concentrations and found that uptake followed a saturating feeding pattern, with a maximum rate of 22 particles per individual per hour. Interestingly, microplastic uptake decreased over time as egested particles aggregated into clumps too large for re-consumption, though ciliate population growth still declined by 43% across the concentration range. The study demonstrates that single-celled organisms can play a meaningful role in microplastic fate in freshwater environments while also being harmed by the exposure.
Microplastic particles are ubiquitous in aquatic environments and are considered a major threat to the large range of heterotrophic organisms that involuntarily consume them. However, there is current uncertainty around the mechanisms underpinning microplastic uptake by aquatic consumers and the consequences for both the fate of the microplastics and the growth potential of consumer populations. We performed a feeding experiment, exposing a model freshwater ciliate, Tetrahymena pyriformis, to six different microplastic concentrations and measured microplastic uptake and population growth over the course of several generations. Microplastic uptake increased in a saturating fashion with concentration, consistent with a Type II functional response, with a maximum feeding rate of 22 microplastic particles individual-1 h-1. Interestingly, microplastic uptake decreased through time and we observed that, after egestion, microplastic particles aggregated, rendering them too large for re-consumption. We built and tested a simulation model which matched rates of microplastic uptake when incorporating functional response parameters and assuming 50 % immobilisation of microplastics after egestion. Nevertheless, ciliate population growth was compromised by the presence of microplastics, decreasing by 43 % over the full microplastic concentration range. Taken together, our results demonstrate the potential for aquatic ciliates to play an important role in the uptake, transfer, and modification of microplastics in freshwater environments with associated negative impacts on population fitness.