Functional response quantifies microplastic uptake by a widespread African fish species

Ecological impacts of microplastic remain poorly understood, despite their ubiquity across all habitat types globally. Microplastic concentrations vary significantly across spatiotemporal gradients, however we lack quantitative methodologies to predict species-level responses to differential environmental concentrations. In the present study, we expose a key species, the banded tilapia Tilapia sparrmanii Smith, 1940, to different concentrations of microplastic particles. We apply and develop the functional response approach for quantifications of microplastic uptake by the fish across different environmental densities. Tilapia consumed microplastic even when relatively rare in their environment, and consumption rates related negatively to concentrations supplied, conducive with a saturating Type II (i.e., inversely-density-dependent) functional response. Attack rate (i.e., search efficiency), handling time and maximum feeding rate estimates towards microplastic were estimated, providing key information on feeding behaviour in relation to exposure concentrations. We propose the utility of functional response approaches for predictive quantifications of microplastic uptake rates. In turn, this can better-link laboratory exposure studies to environmental concentrations which are known to cause ecological impact, and provide a means of comparing uptakes among species and across environmental contexts.