Microplastics in Marine Sediments and Rabbitfish (Siganus Fuscescens)
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Marine Pollution Bulletin 150 (2020) 110685 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Baseline Microplastics in marine sediments and rabbitfish (Siganus fuscescens) from selected coastal areas of Negros Oriental, Philippines T ∗ Lilibeth A. Bucola, , Edwin F. Romanob, Sherlyn M. Cabcabana, Lyca Mae D. Siplona, Gianni Coleen Madrida, Abner A. Bucolc, Beth Polidorod a Biology Department, Negros Oriental State University, Dumaguete City, Negros Oriental, Philippines b Chemistry Department, Negros Oriental State University, Dumaguete City, Negros Oriental, Philippines c Silliman University-Angelo King Center for Research and Environmental Management, Dumaguete City, Negros Oriental, Philippines d School of Mathematics and Natural Sciences, Arizona State University, 4701, W. Thunderbird, Rd, Glendale, AZ, USA ABSTRACT The Philippines is currently ranked as the third top producer of plastic wastes, yet little research has been conducted on marine plastic pollution in this fishery- dependent, developing country. This study is the first in the nation to quantify and characterize microplastics ingested by a commercially important fish, the rabbitfish (Siganus fuscescens), in the coastal areas of Negros Oriental, central Philippines. Across all sites, the diversity of microplastic polymer types was highest in the guts of S. fuscescens from Dumaguete, a densely populated city. Microplastic particles extracted from subtidal sediment samples from Silliman Beach in Dumaguete were dominated by semi-synthetic microfibers (rayon), probably from clothing and textiles. However, these microplastic types were absent in the guts of fish, likely due to the different location and character of their feeding habitats. This study confirms for the first time the presence and diversity of microplastics in an edible finfish in the Philippines. Plastics are synthetically produced from polymerization of mole- The presence of microplastics in the marine environment increases cular monomers, derived from extraction of oil or gas, to form macro- their bioavailability potential to marine organisms (Van Cauwenberghe molecules with infinite ways of utilization for human society (North et al., 2015), while at the same time enhancing the risk of bioaccu- and Halden, 2013; Mahat, 2017). The majority of the advances of mulation of chemical substances found in or adsorbed to microplastics, mankind over the past century have been facilitated by the use of since the particles can be ingested by living organisms (Koelmans, plastics (North and Halden, 2013). However, the accumulation of 2015). Humans can be exposed to the negative effects of microplastics plastics in the form of litter in the marine environment has become a when consuming seafood products (Smith et al., 2018). Negative phy- pervasive pollution problem affecting all of the worlds’ oceans (Frias sical effects of accumulated microplastics in human bodies include et al., 2010). Furthermore, it has been well-documented that degrada- enhanced inflammatory response, size-related toxicity of plastic parti- tion and fragmentation of plastic debris present in the ocean leads to cles, chemical transfer of adsorbed chemical pollutants, and disruption the formation of minute particulates of plastic or “microplastics of the gut microbiome while microplastics and their chemical con- (Browne et al., 2011). stituents may cause localized particle toxicity (Wright and Kelly, 2017; Microplastics are of two forms, primary and secondary. Primary Smith et al., 2018). microplastics are produced intentionally at a microscopic size while The Philippines generates 0.28–0.75 million metric tons of marine secondary microplastics are formed from mechanical and chemical plastic per year which makes it as the 3rd largest contributor of plastic degradation of microplastics, resulting in fragments and fibers leaking into the ocean (Jambeck et al., 2015). Most Filipinos depend on (Mathalon and Hill, 2014; Masura et al., 2015; Nadal et al., 2016). The fish as a main source of food (e.g. for fatty acids, proteins and other most common plastic polymers found in the environment include micro-nutrients) and for their livelihood. One of the most important polystyrene (used in packaging and industrial insulation), acrylic, fishes for local consumption are rabbitfishes (Family Siganidae) be- polyethylene (PE) (used in facial scrubs), polypropylene (PP) (used in cause of their meaty, tasty flesh and high concentration of protein fishing gear), polyamide (PA) (nylon), polyvinyl chloride (PVC), poly- (Wahyuningtyas et al., 2017). However, there is paucity of information styrene (PS), polyethylene terephthalate (PET), polyvinyl alcohol (PVA) on the presence of microplastics in fishery resources in the Philippines and polyester fragments (Mathalon and Hill, 2014; Avio et al., 2017). (Abreo, 2018). Studies have been done in the Philippines on the ∗ Corresponding author. E-mail addresses: [email protected] (L.A. Bucol), [email protected] (E.F. Romano), [email protected] (S.M. Cabcaban), [email protected] (L.M.D. Siplon), [email protected] (G.C. Madrid), [email protected] (A.A. Bucol), [email protected] (B. Polidoro). https://doi.org/10.1016/j.marpolbul.2019.110685 Received 28 May 2019; Received in revised form 21 October 2019; Accepted 23 October 2019 Available online 06 November 2019 0025-326X/ © 2019 Elsevier Ltd. All rights reserved. L.A. Bucol, et al. Marine Pollution Bulletin 150 (2020) 110685 Fig. 1. Location of sampling sites in Negros Oriental, Philippines (https://maps-for-free.com/). microplastics found in beach sediments (e.g. Kalnasa et al., 2019; Paler dry sample weight. To remove organic matter, the procedures by et al., 2019) and mussels (Argamino & Janairo, 2016) but none on in- Karami et al. (2017) were followed with modifications. To remove or- gestion by fishes. In other parts of the world, fishes have been shown to ganic material, 150 g of sediment was soaked with 150 ml of 10% KOH ingest microplastics (e.g. Neves et al., 2015; Hastuti et al., 2019; Tanaka solution and heated in an oven for 40 h at 40 °C. After which, the 10% and Takada, 2016). KOH solution was drained and the sediment samples were washed with This study aimed to provide the first characterization and quanti- distilled water and oven-dried at 90 °C for 40 h for extraction of mi- fication of microplastics in marine subtidal sediments and a commer- croplastic particles. cially exploited fishery resource from selected coastal waters of Negros To extract microplastic particles, a 150 g of dried sediment sample Oriental, central Philippines. In four selected localities in Negros was subjected to zinc chloride extraction. Each dried sediment sample Oriental, rabbitfish (Siganus fuscescens) were sampled from October was divided into three sub-samples (50 g each) to facilitate faster se- 2018 to January 2019 in areas where there are existing fisheries paration process. Each sub-sample was mixed with 100 ml of ZnCl2 − (Dumaguete, Bais, Manjuyod, and Ayungon; Fig. 1). Subtidal marine solution (p = 1.52 g cm 3) in a 250-ml beaker. The resulting solution sediments were sampled off Silliman Beach in Dumaguete from October was stirred at 1000 rpm for 2 min and settled for 6 min. After settling to December 2018. time, the solution was filtered with the aid of a syringe, metal spoon Based on 2015 population data, two of the sites are densely popu- and Whatman filter no. 2 (pore size 8 μm). This process was repeated lated cities (Dumaguete = 131,377 residents; Bais = 76,291) while the twice to ensure complete extraction of microplastics. The filter paper other two sites (Manjuyod = 42,332 and Ayungon = 46,303) are small was washed with distilled water. The washed filter paper was dried in town rural municipalities. In Dumaguete, a 1.8 ha municipal dumpsite an oven and placed in a clean petri dish for optical microscopy analysis. located about 6.86 km upstream of the Banica River is likely a major With the use of clean forceps, the suspected microplastics particles, source of microplastics, aside from a number of small creeks and under the view of a stereomicroscope (magnification 40x), were drainage canals that directly discharge untreated domestic sewage transferred in a clean Whatman filter paper no. 2 to measure the par- wastes. Bais is also traversed by a major river system that drain do- ticles shape and size. mestic wastes. Manjuyod and Ayungon are located north of Bais Bay. To account for possible laboratory contamination, blanks (Petri Although the latter two sites are considered rural areas, plastic wastes dishes with distilled water to serve as controls) were prepared for every were also observed along the beaches of these coastal communities. observation. Particles that were highly similar to those found in these Samples of S. fuscescens (n = 30 per site) were obtained directly controls were excluded from analyses. Throughout the course of the from fishermen (caught by gillnets, spears, and corrals) operating study, only two microplastic types (fine fibers of cellulose acetate and within each of the four sites (Dumaguete, Bais, Manjuyod, and rayon) were detected from the blanks. Ayungon). Among fishes, rabbitfishes are known to have high site fi- After preliminary microscopy, all extracted microplastic (e.g. from delity with very restricted home ranges (Fox, 2012; Bellwood et al., fish GI tracts and marine sediments), were identified to polymer type 2016), which make them good indicators for the