Philippine Journal of Science RESEARCH NOTE 147 (4): 597-600, December 2018 ISSN 0031 - 7683 Date Received: 14 Feb 2018

Survey of Subtidal Anthropogenic Marine Debris (AMD) in Mayo Bay, Mati City, Oriental,

Neil Angelo S. Abreo1,2,4*, Edison D. Macusi2,3,5, and Lea A. Jimenez2,3

1Senior High School Department, Malayan Colleges , , Philippines 2Regional Integrated Coastal Resource Management Center (RIC–XI), State College of Science and Technology, Mati City, Davao Oriental, Philippines 3Institute of Agriculture and Life Sciences, Davao Oriental State College of Science and Technology (DOSCST), Guang-Guang, Dahican, Mati City, Davao Oriental, Philippines 4Institute of Aquatic and Applied Sciences, State College, City, Davao del Norte, Philippines 5Aquaculture and Fisheries Group, Wageningen University & Research P.O. Box 338, 6700 AH, Wageningen, The Netherlands

Anthropogenic marine debris (AMD) is considered a global threat to the marine environment. Mortality from ingestion or entanglement in AMD is widely reported from marine animals and has harmful impacts on seagrass and corals. The distribution of AMD plays a vital role in its interaction with marine organisms. However, there is little information on AMD distribution in the Philippines – a country ranked as the third most significant contributor of AMD in the ocean. During the monitoring of dugong (Dugong dugon) feeding trails in Mati City, Davao Oriental, Philippines, AMD was recorded at one of the sites surveyed. Plastic debris was the most dominant in number and weight of total AMD collected. Here we present the first quantification, characterization, and distribution of AMD in a shallow subtidal area in Mati City, Philippines. More studies are needed to assess the impacts of AMD on the marine environment and organisms, particularly within the Philippines.

Key words: AMD, marine debris, Mayo Bay, Philippines, solid waste management

The threat of anthropogenic marine debris (AMD) to when data from stranding events and necropsies reveal marine biodiversity is a global problem. Plastic, the their presence. Reports on AMD ingestion rely on post- most dominant type of AMD, reportedly affects marine mortem examinations (e.g., Abreo et al. 2016) and not all organisms at different trophic levels and coastal habitats strandings are examined. (Kühn et al. 2015) . Given the ubiquity of plastic usages in society (e.g., food The full extent of AMD is still unknown, possibly wrappers, plastic bags, and decorations), some eventually because of the “cryptic” nature of the problem (Williams ends up in the marine environment and impacts marine et al. 2011). Impacts of AMD may only become evident organisms (Kühn et al. 2015). Coastal areas are often densely populated by people contributing to the entry of *Corresponding author: [email protected] disposable plastics to the marine habitat.

597 Philippine Journal of Science Abreo et al.: Survey of Subtidal AMD Vol. 147 No. 4, December 2018

In Mati City, the habitat of sea turtles and dugong were established as part of the dugong feeding trail overlaps with coastal communities. This overlap may monitoring conducted by the Regional Integrated Coastal lead to interactions between AMD and marine organisms, Resource Management Center XI (RIC XI). resulting to their mortality (Hardesty & Wilcox 2017). During the monitoring of dugong feeding trails, it was In the Philippines, the negative impacts of AMD on observed that benthic AMD was present in the sampling marine organisms have been previously investigated area within Mayo Bay but not in Pujada Bay. The survey and (Abreo et al. 2016). The current study investigates AMD collection of AMD was performed by a single SCUBA diver in subtidal areas in a shallow embayment in Mati City, for 20 min in each of the 20 m x 20 m quadrat. All collected Davao Oriental, Philippines. debris were washed with tap water and air-dried in a room. The sites sampled for AMD were located at Mayo Sorting and classification of AMD was done using the Bay (N06°55’25.9”; E126°16’51.0”) and Pujada Bay UNEP/IOC guidelines on survey and monitoring of (coordinate N06°50’ 45.9”; E126°17’18.3”) in Mati City, marine litter (Cheshire et al. 2009). In this study, this Davao Oriental, Philippines (see Figure 1). Pujada Bay is classification was modified to three broad categories an area of approximately 168 km2 declared as Protected (see Table 1). Count and dry weight of the collected Landscape/Seascape under Republic Act 7586 or the AMD were recorded. Each category was presented as National Integrated Protected Areas System (NIPAS). a percentage of the total number of AMD. Only weight Meanwhile, Mayo Bay is not a protected area but is (grams) of AMD was used in statistical analyses. Count important for dugongs (Mizuno et al. 2017). data were used for descriptive statistics, mainly to calculate means and standard deviations for the various On 7–10 Jun 2016, three (3) 20 m x 20 m quadrats were categories. For the statistical analyses – since only three randomly placed on the seafloor within seagrass beds in 20 x 20 m quadrats were measured – results from all each of the two sites at a depth of 4–6 m. The quadrats quadrats were pooled and categorized as either plastic bags, other plastics, or cloth and others. For combined data, the sample size was n=75 (plastic bags, n=58; other plastics, n=12; cloth and others, n=4). Data were tested for normality using graphical means [Probability Plots (PP plots) and box plots]. When normality was violated, the data were log10 transformed. Post-hoc analyses were done using Tukey tests to check which means among the

Table 1. Classification of anthropogenic marine debris found in feeding areas of dugongs in Davao Oriental, Philippines. Group Composition Plastic bags (PL) freezer bagsa, food packetsb, supermarket plastic bags ropes, rice sack fragments, plastic Other plastics bottles, plastic twine, plastic spoon, (OP) adhesive tapes Cloth and others (CL) sanitary diaper, garments anot classified under the UNEP/IOC classification for Marine Debris (freezer bags are plastic bags commonly used for making ice in the Philippines) bnot classified under the UNEP/IOC classification for Marine Debris (food packets are chips bags, vinegar sachet packs).

different categories differed significantly. All analyses were done using Minitab version 17 (Minitab Inc., State College, PA, USA). The study site in Mayo Bay was littered with AMD, with Figure 1. Map of the study sites in Mayo and Pujada Bay, Davao a total of 75 items collected (Table 2). The average density Oriental, Philippines. of AMD was 0.06 ± 0.06 items m-2 or 0.344 ± 0.32 g·m-2 [lowest density: 0.015 items m-2 (0.15 g·m-2); highest

598 Philippine Journal of Science Abreo et al.: Survey of Subtidal AMD Vol. 147 No. 4, December 2018 density: 0.133 items m-2 (0.718 g·m-2)]. The density of subtidal AMD in Mayo Bay was lower compared to studies in Curaçao (36.5 ± 41.0 items 100 m-2) (Nagelkerken et al. 2001) and the Caribbean (lowest density recorded at 0.26 items m-2) (Debrot et al. 2013). The lower densities could be attributed to reduced sampling effort and smaller area covered in the present study. However, both Nagelkerken et al. (2001) and Debrot et al. (2013) indicated that plastic was the most common AMD in their study areas – similar to the current study. Plastic was the most common AMD found, the mean count of plastic bags was 19, followed by other plastics at 4, and cloth and other debris at 0.61 (see Table 2). In contrast, the results of the one-way ANOVA of the three categories of AMD by weight showed highly significant difference (P=0.000, df=74, MS=2.24, F=8.93, R2=20) and the post-hoc test of the means reveals that plastic was less than compared to the weight of the other plastics and cloth but the other plastics and cloth were not significantly different from each other (PL= 1.91 g, OP= 5 g, CL=15.49 g). These data show that while plastic bags and wrappers are ubiquitous, they weigh less compared to other categories. The low weight of plastic bags and wrappers may downplay the perceived threat. However,

Table 2. Descriptive statistics of the total anthropogenic marine debris found in Mayo Bay, Davao Oriental, Philippines. Category Count Percent Mean SE STDEV Figure 2. Marine plastics partially buried in the sand littering Plastic bags 58 77.33 18.85 7 185 the shallow coastal area in Mayo Bay, Davao Oriental, (PL) Philippines (watch diameter 3.8 cm for size reference). Other plastics 13 17.33 3.87 14 133 (OP) Verlis 2017). The study site in Mayo Bay was adjacent to Cloth and 4 5.33 0.61 4.61 133 others (CL) Dahican beach, a tourist spot in Mati City. Moreover, a large river – the Mayo River – drains into the Mayo Bay. Rivers are a significant source of AMD (Lebreton et al. 2017). Direct disposal of household waste in the marine only one-tenth (0.5g) of a typical plastic bag (4–5g) can environment is still widely practiced in some parts of the potentially kill a juvenile marine turtle (Santos et al. country (Orale & Fabillar 2011) and a possible source of 2015). The types of plastic (single use, sheet-like plastics) AMD. Although Pujada Bay is similar to Mayo Bay in dominant in this study are commonly ingested especially being an open access, multiple use marine environment, by marine turtles (Campani et al. 2013). the absence of large rivers draining in Pujada is one Plastic bags are prone to become marine debris since these possible explanation for the lack of AMD in the site. materials are disposable (Newman et al. 2015). Although Another possible explanation could be the presence a law was passed to promote solid waste management of mangrove forests in Pujada Bay. Mangoves have (Republic Act 9003 or the Solid Waste Management Act the capacity to retain floating AMD, at least trapping of 2000) in the Philippines, a fondness for single-dose macroplastic debris for long periods (Ivar do Sul et al. sachets (e.g., shampoo sachet, toothpaste sachet) and 2013). These factors, along with wind (Kulkulka et al. excessive packing of goods in local sari-sari stores is a 2012) and currents (Thiel et al. 2003), could influence the major contributor to plastic waste. Plastic bags, although distribution of subtidal AMD in the study sites. buoyant, through time can settle to the seafloor due to This study demonstrated the presence of AMD in shallow biofouling (see Figure 2) (Fazey & Ryan 2016). coastal areas of Mayo Bay. Furthermore, it shows The mechanisms of AMD deposition vary. Tourism that plastic is the most common anthropogenic debris contributes AMD in the marine environment (Wilson & in the marine environment. The presence of AMD in

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