The impact of extreme weather events on microplastics in intertidal sediments within a coastal embayment.

Although it is known that microplastics (MPs) can fluctuate temporally, most studies to date have focused on examining MP levels at a single time-point, thus providing a limited estimate of MP abundance in aquatic ecosystems. The goal of this preliminary research was to investigate the fluctuation of MP abundance in the marine environment and determine maximum MP loading following an extreme weather event. This type of investigation is critical for understanding how MPs can fluctuate temporally in the marine environment and predicting when the MP loading is at its maximum. This is particularly important in relation to commercial and locally harvested fish and shellfish species that may accumulate high MP levels and thereby have a negative effect on human health.

This study sampled intertidal sediments in close proximity to a fresh-water source in a coastal embayment on the west coast of Ireland. Intensive sampling was carried out over a five-week period. The first sampling took place two days before two extreme weather events, Storm Dudley and Storm Eunice in February 2022, with subsequent sampling taking place on a weekly basis for four weeks following the event. Both the high water and low water mark were sampled, with 4 replicates randomly retrieved from a transect at each tidal level.  MPs were extracted from the sediments using density separation techniques.

Analysis on the type, quantification, colour, and length of MPs was carried out using light microscopy with standardised contamination control methods.  Micro-FTIR techniques will be used to identify a subsample of the polymers from each time point. Finally, modelling software will be used to determine the maximum loading of MPs to the marine environment using this data. It is anticipated that the results from this research will help to pinpoint critical periods of MP pollution in the aquatic environment and highlight the importance of developing mitigating measures for such events.