Macro and mesoplastics at Joaquina Beach, southern Brazil: a case study

Abstract Sandy beaches are ecologically important coastal ecosystems that are increasingly threatened by plastic pollution. This pollution disrupts their ecological balance and reduces their ability to provide ecosystem services. This study case at Joaquina Beach, Santa Catarina Island, southern Brazil, aimed to assess the spatiotemporal contamination by macro and mesoplastics concerning meteorological and anthropogenic variations, and to identify potential plastic sources for the region. Over 18 months (December 2018 to March 2020), monthly collections of macroplastics and mesoplastics were performed at 12 fixed sampling points. The amount of mesoplastics found was 216 items, with an average of 2.18 items m-2 (range: 0-17.33 items m-2), a higher density than that of macroplastics, of which, 1069 items were found, at an average of 0.32 items m-2 (range: 0-2.2 items m-2). Fragments were the predominant plastic type in both size categories. The region was assessed as “very clean” only once during the monitoring, with the Clean-Coast Index classifying it as “clean” in 59% of the months. March 2019 had the highest macroplastic amount, followed by April 2019 and February 2020. Meanwhile, mesoplastic quantity was highest in April 2019, December 2018, and January 2019. For both categories, beach users were identified as the main possible source of plastic litter, with a smaller contribution from fishing activities. However, meteorological conditions, like wind direction, can also contribute to plastic accumulation in the area. The months with the highest concentration of macro and meso occurrences had a prevailing pattern of southern winds. This study contributes to the knowledge addressing macro and mesoplastics, providing useful information to bridge scientific and management gaps regarding the distribution of different plastic sizes.