Can microplastic pollution be affected by beach nourishment? Assessment in intertidal sediment and bivalves

Several methods can be used to mitigate coastal erosion, and one of the leading solutions is known as beach nourishment (BN), which involves using dredged material for nourishment, adding sand to extend an eroding beach. Although it has many advantages, the environmental impacts of BN remain poorly understood, especially on plastic pollution, which had not been investigated until this study. We aimed to compare the abundance and distribution of microplastics (MPs) found in intertidal sediments and specimens of the bivalve mollusks Crassostrea brasiliana, Mytella strigata, Perna perna, and Tivela mactroides, collected in two beaches of Vitoria, Southeast of Brazil (da Costa et al., 2023), immediately after a BN process. We collected three replicates of intertidal sediment samples at each one of the five sampling points and 20 individuals of each species at two sampling points. This study found 9057 microplastics, of which 1960 were present in the sediment samples and 7097 in the set of bivalves analyzed, giving a frequency of occurrence of 100 %. The results show an increase of 171 % in the total number of MPs analyzed after the BN process. This significant increase in MPs after the BN indicates that this type of action can lead to a drastic increase in the MPs available in the local marine environment, further increasing the risk of contamination of the regional biota.