Microplastic pollution and risk assessment in selected beaches in Lagos State, Nigeria and degradation using associated microbial assemblages

Microplastics are ubiquitous and a threat to global ecosystems causing serious environmental crisis. This study investigated the microbial assemblages associated with microplastics distributed in selected beaches in Lagos State, Nigeria. Sediment samples were aseptically collected, and bacterial species were isolated and identified. Bacteria isolated from the sediment area were screened for microplastic utilization and those with potential to degrade were selected for degradation studies. Degradation was quantified by weight loss (%). Surface morphology and structural changes were analysed using Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) respectively. A total of 1,846 items/kg of microplastics were extracted from all four beach sites. Fragments were the most prevalent (868 items/kg), and the least was pellets (221 items/kg). The most frequently observed microplastic colour was white (495 items). The Pollution Load Index (PLI) values ranged from 1.0 to 2.8. Bacteria isolated included Pseudomonas aeruginosa , Bacillus subtilis , Bacillus polymyxa , Alcaligenes faecalis , Micrococcus luteus , Staphylococcus aureus , and Proteus vulgaris . For the 30-day degradation studies, Treatment A demonstrated the highest % weight loss (28.0%) for PET, while Treatment B recorded a weight loss of 20.0%. FTIR analysis confirmed biodegradation of PET and PP by both Treatments. SEM analysis revealed a compromised polymer matrix in the degraded microplastics, characterized by increased surface roughness, visible pits, cracks, and erosion patterns, all indicative of enzymatic or physical microbial activity. The study showed the potential of bacteria consortia from beach sediments to breakdown PET and PP, offering an environmentally friendly solution to address plastic contamination. • Microplastics are widespread in the four beach sites. • Fragment, with 863 item/g, was the most abundant microplastic shape. • The pollution load index (PLI) values ranged from 1.00 to 2.17. • Treatment A demonstrated highest weight loss of 28% for PET and 20% for PP.