Microplastics pollution in the sediments of creeks and estuaries of Kenya, western Indian Ocean

Microplastic pollution has been recognised as a global threat in marine environments and a danger to prey, predators and humans. Yet, there have been few studies in the western Indian Ocean, specifically along the Kenyan coast, which makes it difficult to estimate the extent of such pollution in the region. This is the first study on microplastics (MPs) in the sediments within creeks and estuaries (Tudor, Port Reitz and Mida creeks) on the Kenyan coast. In January/February and September 2018 sediment samples were collected for MPs analysis. The concentration of MPs differed between the sampling seasons and was distinctively higher in the second sampling season across particle sizes, suggesting that there were more MPs from larger terrestrial discharges due to increased runoff. The concentrations of total MPs, and the occurrence of different sizes, shapes and colours, were established under a microscope. The overall mean concentration was highest for the large size category of MPs (500–4 999 µm) at 9.1 (SE 0.8) particles cm−2, with Tudor Creek being more polluted with MPs than Port Reitz and Mida creeks. We recommend formulation of policies on proper plastic waste management and disposal to protect nearshore ecosystems which are rich in marine biodiversity.