Regional Studies in Marine Science 38 (2020) 101365 Contents lists available at ScienceDirect Regional Studies in Marine Science journal homepage: www.elsevier.com/locate/rsma Microplastics distribution and characterization in epipsammic sediments of tropical Atlantic Ocean, Nigeria Omowunmi H. Fred-Ahmadu a , Olusegun O. Ayejuyo b , Nsikak U. Benson a,∗ a Department of Chemistry, Covenant University, Km 10 Idiroko Road, Ota, Nigeria b Department of Chemistry, University of Lagos, Akoka, Nigeria article info Article history: Received 3 February 2020 Received in revised form 23 April 2020 Accepted 15 July 2020 Available online 18 July 2020 Keywords: Microplastic pollution Tidal waterline Hydrodynamic conditions Gulf of Guinea Fragments ATR-FTIR abstract Recent reports indicate that microplastics (MPs) show both temporal and spatial variations therefore, regional data collection and environmental dynamics are vital aspects of understanding the underlying sources and factors that influence the abundance and dispersion of the plastic particles. This paper presents a baseline report on the abundance of microplastics across three tidal waterlines (high, drift and current) of the tropical Atlantic ecosystem. Microplastics (1 – 5 mm) occurrence and distribution in epipsammic sediments of five beaches in Lagos, Nigeria (Gulf of Guinea) were assessed. The microplastics were extracted by density flotation using saturated solution of NaCl and the identification of polymer types was done by attenuated total reflectance Fourier transform infra-red spectroscopy, ATR-FTIR. Results showed significant variations in the population of MPs in the three tidal waterlines with the high and drift waterlines accounting for 58.83% and 41.16% of the total MPs, respectively while no MPs were detected in the current waterline sediment. Polyethylene, polystyrene and polypropylene were the most abundant polymers recorded. Fragments were predominantly detected and pre- production pellets formed only 5.27% of total microplastics. Polymer risk index calculations showed low to medium risk of the microplastics found and local hydrodynamic conditions such as Ocean surges and current intensity were observed to influence the distribution and dispersion of microplastics. Continuous monitoring of MPs abundance is necessary to minimize the polymers’ risk to the ecosystem. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Microplastic pollution has gained increasing global attention due to the potential threat to both terrestrial and aquatic life. Microplastics (MPs) are manufactured directly in sizes < 5 mm in diameter (primary microplastics) or formed as a result of the fragmentation of larger plastics due to environmental expo- sure and abrasion (secondary microplastics) (Fred-Ahmadu et al., 2020; Thompson, 2016). The most commonly identified plas- tic polymers in environmental samples are polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyvinylchloride (PVC) (GESAMP, 2015; Ogata et al., 2009). Some of the sources of microplastics in the aquatic ecosystem include loss of pellets dur- ing transportation, wastewater effluent, fishing ropes and gears, cigarette butts, abrasion from sandblasting at shipyards, plastic waste carried by wind or run-off water, and so on (Rochman, 2013). Plastic wastes are generally non-biodegradable, persistent and pervasive in the environment. While many beaches are reg- ularly cleaned to increase their face value and attract tourists, the cleaning rarely takes care of microplastic particles. Sandy ∗ Corresponding author. E-mail address: nsikak.benson@cu.edu.ng (N.U. Benson). beaches, therefore, become sinks for micro-sized plastics and other kinds of debris. Microplastics are regarded as multiple stressors of the aquatic ecosystem because they present considerable risks in various ways: (a) by direct toxicity posed by plastics particles causing oxidative stress, inflammation and cell damage in organisms, (b) chemical toxicity due to the effects of additives such as plasticizers, biocides, flame retardants and UV stabilizers which may contain toxic trace metals, (c) as vectors of pathogens and parasites like Escherichia coli; and (d) as vectors of persistent organic pollutants (POPs) including phthalate esters (Benson and Fred-Ahmadu, 2020; Zhang et al., 2019; Li et al., 2017; Vethaak and Leslie, 2016; Leslie and Vethaak, 2014). In addition, spatial and temporal variations do occur with field sampled microplas- tics in terms of their abundance, types, shapes, colour and the distribution and limited studies are available on the distribu- tion of microplastics along depositional lines of beaches. Here, this study presents a snapshot and baseline data of the abun- dance, types and variations of microplastics in five sandy beaches, namely Badagry (BG), Oniru (OR), Elegushi (EG), Atican (AC) and Eleko (EK). Our aim was to study the depositional variations of microplastics along the coastline of the tropical Atlantic ecosys- tem, Nigeria and to evaluate the influence of local hydrodynamic https://doi.org/10.1016/j.rsma.2020.101365 2352-4855/© 2020 Elsevier B.V. All rights reserved.