Microplastic pollution in Canadian freshwater ecosystems: First insights into contamination of British Columbia lakes and implications for Canadian freshwater biodiversity

Background/Question/Methods

Microplastics have emerged as a global contaminant of concern due to their widespread distribution, persistence, and demonstrated potential to cause adverse effects upon ingestion. Less is known about microplastics in freshwater compared to marine environments, and this is evident in British Columbia (BC) and across Canada. Furthermore, although it has been established that freshwater biodiversity is facing a crisis caused by a myriad of anthropogenic disturbance and pressures, the contribution of microplastics as a threat has been overlooked. Despite having vast ecological and cultural value, data on microplastic contamination in BC lakes is scarce. We provide the first documentation of microplastics in BC lakes by quantifying and characterizing contamination in eight lakes. Lakes were selected to span a gradient of urbanization to investigate sources of pollution and if proximity to urbanization affected types or quantities observed. By sampling water and zooplankton, we provide insight into the fraction of microplastics entering the food web. To broaden the scope of our empirical work, we formed a working group with early career microplastics researchers and asked what is known about freshwater microplastic pollution in Canada, how are different organisms affected, and how can we use this evidence to inform decisions to protect biodiversity.

Results/Conclusions

Microplastics were found in all water samples and most zooplankton samples. The concentration of suspected microplastics in water samples ranged from 0.4-2.0 microplastics per L, with a mean of 0.8 (+/-0.25 S.D). There were no significant differences between lakes, but urbanized lakes contained more microplastics than rural lakes. The incidence of ingestion for zooplankton ranged from 0-0.1, with a mean of 0.03 (+/-0.01 S.D) microplastics per individual. There were no significant differences between lakes, however consistent with our water samples, zooplankton from urban lakes contained more microplastics. Our results align with current literature and illustrate that microplastics are bioavailable to freshwater organisms, however zooplankton ingestion and retention appears low. As zooplankton are the conduit of energy through freshwater environments, this result may indicate that the potential for trophic transfer of microplastics is low. However, our study results are reflective of a snapshot of contamination in eight lakes and further sampling is needed to better characterize microplastics in freshwater environments and food webs. We identified microplastics as a threat to Canadian freshwater biodiversity, however as research efforts are disproportionately focused on certain geographic areas and taxa, more data is needed to understand the magnitude of this threat to biodiversity.