Extreme Storm Surge Events and the Deposition of Plastic Pellets on Beaches of Todos os Santos Bay, Bahia, Brazil

Extreme positive storm surge events, often followed by storms, are referred to as storm surges. In Brazil, the informal term ressaca is commonly used to describe these events. The occurrence of ressacas in coastal regions can lead to flooding, destruction of urban infrastructure, and beach erosion. Coastal erosion is a natural process resulting from a negative sediment balance, leading to beach narrowing, habitat degradation or loss, increased frequency and intensity of ressacas, destruction of man-made structures, and the decline of tourism potential. Between June and September of 2023, fieldwork was conducted to assess the presence of plastic pellets on beaches within the Todos os Santos Bay/Bahia. This assessment involved the observation of beach morphodynamics, the presence of ordinary and recent storm surge strandlines, and the identification of preserved strandlines that had not been subjected to anthropogenic disturbances—such as beach cleaning via tractor or rake, recreational activities, or boat traffic. Following these observations, sand samples containing pellets were collected from two specific zones: the Current Strandline Zone (ZDD), typically associated with the swash zone, and the Post-Storm Strandline Zone (ZDPP), often linked to the most recent high-energy storm surge events. Across the eight beaches studied, 74 sampling points were marked, and a total of 203 pellets were found. The majority of these pellets were located in the higher beach zones, i.e., within the ZDPP. These findings indicate that extreme storm surge events are the primary drivers of plastic pellet distribution on beaches.