Microfiber uptake by freshwater mussels in tributaries of the Saint John River Watershed, New Brunswick

Abstract

Recognized as a potential novel environmental stressor, microfibers are a widespread contaminant of anthropogenic origin. Many enter aquatic systems through wastewater treatment plant (WWTP) effluent and may persist in the environment indefinitely. Although the environmental impacts of microfibers are not well-understood, they are suspected to play a role in the dispersal of chemicals and other contaminants throughout aquatic systems and may impair feeding and respiration of aquatic filter-feeding organisms due to their tendency to accumulate on digestive and respiratory tissues. This study aimed to determine whether freshwater mussels in the Saint John River watershed acquire microfibers on or within their tissues, and if so, whether microfiber abundance was related to WWTP discharge points and other potential diffuse microfiber sources. Microfiber abundance was assessed in mussels of the species Margaritifera margaritifera L., which were collected both upstream and downstream of WWTP discharge points and at intermediate sampling points along the Kennebecasis and Tobique rivers. No spatial trends were observed in microfiber abundance in relation to WWTP discharge on either river. Mussels from the Tobique River had significantly (p < 0.01) more microfibers per gram of soft tissue than those from the Kennebecasis. These results help reveal a potential pathway through which microfibers may be entering aquatic food webs and addresses the plausibility of using mussels as bioindicators of microfiber contamination.