Mesoplastics on Joaquina beach, Santa Catarina Island, Brazil: sources, characterization and temporal trend

, Camila Andreussi, Zanetti Daniela, Leonel Juliana.

The quality of sandy beaches is at risk because of the incidence of plastic, a contaminant of great concern due to their impacts to the ecosystem. The temporal variability of mesoplastics (5 to 25mm) at Joaquina beach, from July/2018 to January/2020, was analyzed aiming to evaluate which factors, natural and/or anthropic, are the main responsible for its occurrence. Monthly samplings were carried out in 2 transects (strandline x backshore) at 12 fixed points. Items sampled were counted, measured, photographed and characterized. In the total 284 items were sampled with density varying from 0 to 24 items m-2 (average=6.4); lower than those reported for other parts of the world (i.e. India and Korea). As expected, higher concentrations of mesoplastics were found in the backshore region highlighting its importance for trapping litter. Fragments were the predominant type of plastic found (76%), which sources are not traceable, followed by Styrofoam (17%), which is associated with fishing since its incidence was higher in the months of less use of the beach by tourists. Occurrence of mesoplastic showed no relation with seasonal use of the beach suggesting that their presence may be related to meteorological and oceanographic conditions. For example, the highest amount of plastic was found when strong winds blowing in the southwest direction were registered, whereas the lower amount was found collected concomitant to north winds. The lowest occurrence of items was observed in May, which also had the highest precipitation in the sampling period (196.60 mm), implying that rainwater runoff can remove particles from the beach. The influence of storm events, such as cold fronts and meteorological tides, and how they can generate an increase in the number of items were also reported.

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