Marine Pollution Bulletin 79 (2014) 278–283

Contents lists available at ScienceDirect

Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul

Microplastics in Singapore’s coastal mangrove ecosystems Nur Hazimah Mohamed Nor, Jeffrey Philip Obbard ⇑ National University of Singapore, Block E1A, #07-03, No. 1 Engineering Drive 2, Singapore 117576, Singapore

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Keywords: Microplastic Mangrove Singapore ATR–FTIR spectroscopy

a b s t r a c t The prevalence of microplastics was studied in seven intertidal mangroves habitats of Singapore. Microplastics were extracted from mangrove sediments via a floatation method, and then counted and categorized according to particle shape and size. Representative microplastics from Berlayar Creek, Sungei Buloh, Pasir Ris and Lim Chu Kang were isolated for polymer identification using Attenuated Total Reflectance–Fourier Transform Infrared (ATR–FTIR) spectroscopy. Microplastics were identified in all seven habitats, with the highest concentration found in sediments at Lim Chu Kang in the northwest of Singapore. The majority of microplastics were fibrous and smaller than 20 lm. A total of four polymer types were identified, including polyethylene, polypropylene, nylon and polyvinyl chloride. The relationship between abundance of microplastics and sediment grain size was also investigated, but no relationship was apparent. The presence of microplastics is likely due to the degradation of marine plastic debris accumulating in the mangroves. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction Worldwide plastic production has dramatically risen to about 280 million tonnes, as of 2011 (PlasticsEurope, EuPC, EuPR, & EPRO, 2012). Global consumption is expected to grow by about 4% each year up to 2016 (PlasticsEurope et al., 2012). Plastics are widely used because they are lightweight, durable and inexpensive. Low recovery rates and improper disposal of plastic waste has resulted in the accumulation of plastics in the environment. This has led to the emergence of a new type of contaminant in the environment, referred to as microplastic. Microplastic has been defined by the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) to have an upper size of 5 mm (Bowmer and Kershaw, 2010). Microplastics (1.6 lm) were prevalent in Singapore’s coastal beach sediments (Ng and Obbard, 2006). Thus, it is plausible that microplastics will be abundant in a range of coastal sites, such as coastal mangrove habitats, which serve as a natural biological filter to debris derived from both land and marine-based sources. As such, a study has been conducted to determine the prevalence of microplastics in the coastal mangroves of Singapore. The aim of this study was to investigate the occurrence and distribution of microplastics in Singapore’s coastal mangroves sediments, as collected from seven separate mangrove habitats across the island-state nation. The extracted microplastics were counted and grouped according to particle shape, size and polymer type. The different polymer types were identified using Attenuated Total Reflectance–Fourier Transform Infrared (ATR–FTIR) spectroscopy. Results have been compared against available data from other similar studies conducted elsewhere. Sediment grain size distribution was also measured to determine the presence of any relationship between sediment size and microplastic concentration in the mangrove habitats. 2. Materials and methods 2.1. Sample collection Samples were collected between August and November 2012 from seven mangrove habitats located around Singapore’s coastline. The seven sites are Pasir Ris (N01°220 39.400 ), Changi (N01°230 24.500 ), Lim Chu Kang (N01°260 47.700 ), Pulau Ubin (N01°240 09.300 ), Pulau Semakau (N01°120 33.800 ), Sungei Buloh (N01°260 46.000 ) and Berlayar Creek (N01°160 05.800 ). The locations of the habitat sampling sites are shown in Fig. 1. Sediment samples were collected from the top 3–4 cm (oxygenated zone) at low tide using a clean stainless steel spatula. Sediments were taken from three separate 1.5 m  1.5 m quadrats in an area of 2.25 m2, located 2–3 m apart in undisturbed areas. Wet sediment samples were homogenized and dried in the oven at a temperature of 60 °C, for an average of 24 h, or until complete dryness. Sediments were then gently ground using a mortar and pestle. The ground samples were then stored at 4 °C prior to analysis. 2.2. Analysis Microplastics were extracted from sediment samples using a modified flotation method (Claessens et al., 2011; Martins and Sobral, 2011; Ng and Obbard, 2006; Norén, 2007; Thompson et al., 2004). Concentrated saline solution was added during the extraction process to allow low-density microplastic particles to float to the surface of the solution, and then be subsequently collected via filtration. 500 ml of 1.18 g/l concentrated saline solution was added to 250 g (dry weight equivalent) of sediment in a 1 l con-

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ical flask. Tween-80 was added to samples with a finer sediment particle size (

Microplastics in Singapore's coastal mangrove ecosystems.

The prevalence of microplastics was studied in seven intertidal mangroves habitats of Singapore. Microplastics were extracted from mangrove sediments ...
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