Microbial pollution on microplastic, beach sand and coastal sea water in Aydın-Kuşadası coasts in Turkey

Microplastics constitute a new ecological niche for microorganisms. The colonization of microplastics by pathogenic bacteria poses significant risks to both human and environmental health. In our study, we aimed to isolate and identify culturable bacteria from microplastic, beach sand and coastal seawater samples collected from 10 different stations in 4 different seasons in the Aydın-Kuşadası coastal areas and to determine the microbial load in the samples. To our knowledge, this is the first study to seasonally examine microbial contamination in microplastics, beach sand, and coastal seawater in Turkey, contributing with valuable data to global research. During, it is expected that the findings of this study will contribute to future research. In the study, a total of 120 bacteria were isolated and identified from microplastic surfaces, beach sand and coastal seawater. A total of 58 different bacterial species belonging to 27 different genera, including Staphylococcus , Pantoea , Micrococcus , Priestia , Stutzerimonas , Bacillus , Rhizobiu m, Exiguobacterium , Sphingomonas , Cronobacter , Pseudomonas , Alkalihalobacillus , Arthrobacter , Enterobacter , Brevibacterium , Shigella , Klebsiella , Vibrio , Aeromonas , Acinetobacter , Escherichia , Zobellella , Listeria , Kocuria , Kluyvera , Planococcus and Proteus , beach sand and coastal seawater samples. Bacterial loads of the samples were determined and compared seasonally. The highest bacterial counts were found in microplastics and beach sand in May. Furthermore, the highest bacterial counts in seawater were found in February and May. Interactions were also observed between bacterial groups cultured from microplastics, beach sand, and seawater. • In 10 different sampling stations (1: Güzelçamlı Beach, 2: Venus Beach 1, 3: Venus Beach 2, 4: Davutlar Youth Camp Beach, 5: Sevgi Beach, 6: Davutlar Beach, 7: Nazilli Site, 8: Kuşadası Central Public Beach, 9: Kadınlar Beach, 10: Long Beach) and 4 seasons, the highest number of bacteria as CFU/mL was found in UTIC Agar, R2A Agar and Zobell Marine Agar media on microplastic, beach sand and coastal sea water. • There were similarities found between bacteria cultured from beach sand and seawater and bacteria isolated from microplastics. • Bacteria have been observed using microplastics as a niche. • Microplastic pollution may threaten public health because microplastics harbor opportunistic pathogenic bacteria.