Microplastics (MPs) are plastics less than 5 mm in diameter. Due to their small size, they are easily mistaken for food by sea fauna, particularly the filter and deposit feeders. Ingestion of microplastics may cause poisoning, infertility, gene disruption, gut blockage or damage of the digestive tracts of organisms resulting to reduced feeding. The aim of this study was to determine the type and abundance of microplastics in macro-invertebrates (oysters, jellyfish, and crabs) along the Kenyan Coast (Tudor, Port Reitz and Mida Creeks). Sampling was done during low spring tide in January/February 2018. A total of n = 285 individuals comprising crabs, oysters and crabs were collected from eight stations. Identified species were: Uca dussumieri (Milne Edwars, 1882), Uca inversa (Hoffman, 1874) and Uca vocans (Linnaeus, 1758) for crabs, Saccostrea cucullata (Born, 1758) for oysters while jellyfish belonged to the genus Crambionella. Crabs occurred in seven stations while oysters and jellyfish were encountered in three stations only. U. dussumieri was the dominant species of crabs occurring in six out of the stations. Samples were digested using 10 % KOH at 60 ºC for 24hrs. Digested samples were sieved using 38 µm sieves then filtered through Whatman filter membranes (0.8µ). The filters were viewed under a dissecting microscope and suspected microplastics isolated and tested using a hot needle test. All the samples contained microplastics, mainly fibres that were of different lengths and colours. Colourless fibres were the dominant fibres accounting for 60% of all the fibres. Mean (± SE) lengths of microplastics ranged from 0.1 mm to 4.2 mm. Blue fibres ingested by crabs were the longest at 4.2 mm. Mean (± SE) concentration of microplastics per gram of tissue for the three organisms were: 0.65 ± 0.131 in crabs, 3.36 ± 0.53 in oysters and 0.03 ± 0.01 in jellyfishes. These means were compared using a repeated independent t-test, and were found to be statistically different: crabs and oysters (t= 5.61, df =14, p = 0.01), jellyfish and oysters (t = 5.28, df = 10, p = 0.01) crabs and jellyfish (t= -3.45, df = 12, p = 0.002). Oysters had the highest concentration of microplastics which was attributed to their filter feeding habits which generates a lot of currents and concentrates more particles in the water including microplastics. This study provides evidence of microplastics pollution in waters along the Kenyan coast and their ingestion by filter and deposit feeding fauna which are important as food for humans or fish of economic importance. Consumption of these organisms therefore, could lead to the transfer of microplastics in their tissues into human diet with implications on human health. This study hence, recommends proper plastic waste management to reduce their accumulation in the marine environment and eliminate any possible threat to the economically important sea fauna that ingest them.

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