Microplastic abundances in Craig Bay, British Columbia

Abstract

Microplastics are primarily produced from the fragmentation of larger plastic materials via physical, chemical, or biological means to eventually be carried by wind and water to marine environments, such as estuaries. As a result, in these microplastic sinks, the concentration of microplastics accumulated in sediments depends on grain size, such that microplastics are deposited with similarly sized grains. Ultimately, sampling in microplastic sinks provides information about microplastic retention. Samples were collected from Craig Bay, British Columbia, Canada, to determine if different energy levels within depositional environments affect the accumulation and retention of microplastics. Samples were split into three subsets: one subset was sifted through various sieves to determine grain size distributions and dominant grain size; a second subset was used to determine organic matter content; and, the third was used for microplastic extraction using density floatation and enzyme digestion. Although the study showed no relationship between grain size and microplastic concentration, samples closest to the tidal channel contained fewer microplastics, suggesting that higher energy environments may be less likely to retain microplastics. Although the sample size was insufficient to confirm whether a correlation between microplastics and sediment exists, this study evaluated two analytical methods and developed a workflow that can be applied to future sample sets. A larger sample size from various locations may provide insight into other factors that affect microplastic retention and quantity, such as energy levels and proximity to urban areas. This research is part of a new and emerging research area within sedimentology that focuses on the correlation between sediments and microplastics.