Microplastics in Sumba waters, East Nusa Tenggara

Abstract

The accumulation of plastic debris in the oceans has been widely recognized as a threat to marine environment. A recent study estimated that Indonesia is one of the biggest sources of plastic wastes in the ocean, but directly-measured abundance data from the seawater in Indonesia is lacking. We documented the abundance and distribution of microplastics (size <5mm) in sub-surface seawaters of Sumba, a pristine region in Indonesia. Water samples were collected from 5 m, 50 m, 100 m, 300 m depth and near the sea bottom. Samples were examined for microplastics using flotation and filtration methods. We found microplastic in all sampling locations, consisting of fibers (45.45%), granules (36.36%) and other plastic form (18.18%). Most of microplastic particles were found at water depths less than 100 m (81.82%), which was the thermocline area. Our finding corroborates the believe that plastics has widely invaded marine environment in different parts of the seas and oceans, including pristine, remote, and unknown areas.

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Microplastics in Sumba waters, East Nusa Tenggara
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Microplastics in Sumba waters, East Nusa Tenggara
M R Cordova and U E Hernawan
Research Center for Oceanography, Indonesian Institute of Science (LIPI). JL. Pasir
Putih 1, Ancol, Jakarta Utara, Jakarta, 14430, Indonesia
E-mail: muhammad.reza.cordova@lipi.go.id
Abstract. The accumulation of plastic debris in the oceans has been widely recognized as a
threat to marine environment. A recent study estimated that Indonesia is one of the biggest
sources of plastic wastes in the ocean, but directly-measured abundance data from the seawater
in Indonesia is lacking. We documented the abundance and distribution of microplastics (size
<5mm) in sub-surface seawaters of Sumba, a pristine region in Indonesia. Water samples were
collected from 5 m, 50 m, 100 m, 300 m depth and near the sea bottom. Samples were examined
for microplastics using flotation and filtration methods. We found microplastic in all sampling
locations, consisting of fibers (45.45%), granules (36.36%) and other plastic form (18.18%).
Most of microplastic particles were found at water depths less than 100 m (81.82%), which was
the thermocline area. Our finding corroborates the believe that plastics has widely invaded
marine environment in different parts of the seas and oceans, including pristine, remote, and
unknown areas.
1. Introduction
Plastics are a successful story with regard to their characteristics that make them suitable for a wide
variety of products [1]. By 2014 the total plastic production reached 311 million tons [2]. High
consumption rate but low recovery rates has driven plastics to be a potential threat to the environment.
[3] reported that most of plastic packaging is not recovered, of which 40% goes landfilled and 32% leaks
to the environment including marine ecosystem. Plastic pieces that ended up in the environment remain
still with very slow degradation (up to 100 years). Recent studies estimated that plastic debris in the
ocean are between 7,000 – 250,000 metric tons [4,5]; land based input to the oceans are between 4.8 -
12.7 metric tons; and Indonesia was listed as one of the top sources of land based input [6]. This
estimation, however, lacks real abundance data in the ocean since it used mathematical model based on
solid waste production, population density and economic status of the countries.
Plastic pollution was initially seen as an aesthetic problem [7,8], however recent studies have shown
that marine animals can be negatively affected by the presence of plastics. Threats posed by plastics
with large size are obvious, clear environmental risks by physical impairment after swallowing,
entanglement [9]. [10] stated that from the 1960s to 1990s, physical impairment caused by plastics had
increased almost three times (267 to 693 species). Furthermore, [9] reported that all seabird species
(395 species) contained plastics in their digestive systems.
Plastic waste can be degraded by UV thermal oxidation or mechanic processes up to the microscopic
size [11,12]. Microplastics (<5mm) are formed by the physical, chemical and biological fragmentation
of larger items of plastics. Besides commonly-used plastics, microplastic may originate from cosmetic
or fabric, in the form of microbeads [13,14]. The impact of microplastics in the marine environment are

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not clearly known. Studies in the last decade have indicated potential environmental risks from
microplastics, but real consequences are mostly unknown. Microplastics accumulation in
gastrointestinal on marine organism has been reported [15–19], but the impact of the accumulation to
the organisms are not known. Microplastics could enter the food web by organism ingestion [20], could
interference digestive tract function [17], and may act as a carrier for organic material and heavy metals
[21–23].
Sumba, located in East Nusa Tenggara, Indonesia, is a pristine region in the outlet of Indonesian
Through Flow (ITF) connecting the Pacific Ocean and the Indian Ocean. It is in the southern part of the
Wallacea transition zone, where Indo-Malaya and Australasian biogeographic characteristics meet. It
has unique marine ecosystems and high biodiversity. This area is an important migration corridor to
many marine megafaunas and pelagic fishes. Here, we documented the abundance and distribution of
microplastics (size <5mm) in sub-surface seawaters of Sumba.
2. Introduction
2.1. Study area
Sumba is located in East Nusa Tenggara, eastern Indonesia (Figure 1). Sumba waters area is believed to
have high marine life, but minimal scientific information. From the perspective of oceanography, this
area is also believed to be unique because of the interaction between Indonesian Through Flow
(ITF/Arlindo). The presence of four water masses on the western side, north and south of Sumba Island
(Northern Pacific Subtropical Water-NPSW, North Pacific Intermediate Water-NPIW, Northern Indian
Subtropical Water-NISW and Northern Indian Intermediate Water-NIIW), proves that this area is an
outlet of ITF [24–26]. A front near the western tip of Sumba Island potentially trigger an eddy and might
be influenced by the South Java Current (SJC) [24–26]. This current is believed to trigger upwelling
which is important for fishery resources. In addition, oceanographic process also believed to be
important in Sumba region is mixing, that is the mixing of water masses that can occur due to tidal
currents, bathymetry, and internal waves.
2.2. Sample collection
Sampling was conducted during the 9th Ekspedisi Widya Nusantara (EWIN IX) in August 2016 using
RV Baruna Jaya VIII. Sampling sites are shown in Figure 1. Water samples (10 liters per depth per site)
were collected using Rosette Water Sampler at 5 m, 50 m, 100 m, 300 m and near the sea bottom, then
were filtered using a sterile Whatman® cellulose nitrate filter papers (diameter 47 mm; pore size
0.45µm). To accelerate filtration process, we used Gast vacuum DOA-P504-BN. All samples in the
filter papers were stored at 4±2 °C before analysis in sterile Petri dish and covered with ParaFilm®
sealing film. To prevent samples from being contaminated, we wore laboratory latex gloves and
eyeglasses for filtering, sorting and counting. All sterile glassware were used and filters were stored in
Petri dishes, sealed with Para Film.
2.3. Sample analysis
Microscope Leica M205C was used to examine microplastics particles on the filters. We were using the
following characteristics [17,27,28] to identify microplastics, namely (1) particle size ≤ 5mm, (2)
homogeneous colour, not shiny or sparkling and no cellular or organic structure, (3) fiber particles are
unbranched and not segmented. The microplastics identified were counted and measured. The types of
microplastic then were classified as fibers, granule, fragment, and foam; and were categorized to the
size of <300µm; 300-500µm; 500-1000µm; >1000µm. We analyzed microplastics with sizes more than
250µm using Fourier Transform Infrared (FT-IR). FT-IR can be used to analyze microplastics samples
directly [29]. Polymer analysis was done using Nicolet™ iS5 FT-IR Spectrometer, equipped with a
laminated diamond crystal Thermo Scientific™ iD5 attenuated total reflectance (ATR) accessory, and
corrected using Omnictm Software. The instrument was operated based on [30] at a range of 600 and
3800 cm-1, a resolution 8 cm and at a rate of 16 scans per analysis, in single reflection mode. Before
we analyzed using FT-IR, all potentially plastic particles were rinsed with ethanol 96%. To prevent

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samples from airborne contamination, we analyzed all particles based on a report by [31]. Afterwards,
we did not quantify the fiber particle of the same polymer type as the lab clothes we have worn.
Microplastics concentration are presented as n/m3 unit (Table 1) to compare with other research result,
simple statistical tests were performed on the data collected using Microsoft Excel are presented mean
values ± standard deviations (SDs).
Figure 1. Sampling sites and average abundance of microplastics particles in five different depth (5 m,
50 m, 100 m, 300 m depth and near the sea bottom)
3. Results and discussion
3.1. Study area
Plastic particles were found in all sampling location (10 sampling locations). Average microplastics
concentration per station in five different depth were 44 ± 24.59 n/m3. The highest concentration of
microplastics was observed in Sumba Strait (St-8 and St-10). At 5m depth, microplastics particles were
found in all sampling locations (Figure 2). However, microplastics was not observed at 100m depth.
This might be related to the presence of thermocline zone, ranging from 53m to 144m depth.

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Figure 2. Average of microplastics abundance (n particles/m3) in all station at
five different depth in Sumba Sea
Microplastics abundance at 5m depth was nearly similar with that of the coastal area in Yangtze
estuary China [32,33]. The abundance in this area was higher than that of other open oceans, for example
North East Atlantic Ocean (2.46 n/m3; [34]), East China Sea (0-1.44 n/m3; [33]), and North West
Mediterranean (0.116 n/m3; [35]. The wide variety of microplastic abundance in different oceans might
be related with the fact that microplastics tend to be heterogeneously distributed in a water mass [36].
Because Sumba region is one of the ITF outlets [24–26], characterized by four water masses (NPSW,
NPIW, NISW, NIIW), we believe that microplastics observed in Sumba might not only come from
anthropogenic activities around [28] Sumba, but also from other parts of the oceans in the Pacific.
Table 1. Microplastics occurrence, characteristic and polymer composition
Size
Form
Percentage
(%)
Polymer
Percentage
(%)
Fibers
Granule
Other
PE
PS
PA
PP
<300µm
1
1
0
9.09
1
0
0
0
4.55
300-500µm
3
2
4
40.91
4
2
1
1
36.36
500-1000µm
4
5
0
40.91
5
0
0
4
40.91
>1000µm
2
0
0
9.09
4
0
0
0
18.18
Percentage (%)
45.45
36.36
18.18
63.64
9.09
4.55
22.73
PE- Polyethylene; PS- Polystyrene; PA- Polyamide; PP- Polypropylene
3.2. Microplastics occurrence, characteristic and polymer composition
We classified microplastics from Sumba into four size categories: <300µm, 300-500µm, 500-1000µm,
and >1000µm; and into three forms: fibers, granule, and other type (fragment, foam) (Table 1). In all
sampling stations, microplastic size ranges from 280µm to 1120µm. Most of identified microplastics
(81.82%) were 300-1000µm in size. Fibers were the most abundant form (45.45%), followed by granule
(36.36%) and other type (18.18%). We identified four dominated categories of plastic polymers:

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Polyethylene (PE), Polystyrene (PS), Polyamide (PA) and Polypropylene (PP). PE was the most
common dominated polymer type, followed by PP, PS, and PA (Table 2).
Figure 3. Example of comparison of the spectrum of polypropylene polymer standard from Thermo-
scientific (red) and a spectrum obtained from the measurement of a dominated polypropylene fragment
particle found in Sumba waters (blue) by ATR-based FTIR spectroscopy
Figure 3 shows examples of the polymers found, which dominated with Polypropylene (PP). From
fragment particle sample, prominent presence peak at wavenumber 2950 cm-1, 2916 cm-1, 2837 cm-1 and
2868 cm-1. Similar observation by [37] for PP samples indicated peak at 2951 cm-1, 2911 cm-1 and 2844
cm-1 indicating an asymmetrical type of vibration (ⱱa-CH2) [38]. Those were similar displayed vibration
bands of polymer standard at 2950 cm−1, 2917 cm-1, 2869 cm-1 and 2837 cm-1. In this study, fragment
particle found in Sumba waters and polypropylene polymer standard (Figure 3) showed an absorption
band at 1375 cm-1 and at 1454 cm-1. Spectrum of PP showed symmetrical deformation vibrations (δs–
CH3) at 1372 cm−1 and asymmetrical deformation vibrations (δa-CH3) at 1458 cm−1[37,38].
Size of microplastics could determine the potential impact to the organisms [28]. Smaller size
increase the possibility of microplastics ingested by the organisms [33,39]. This situation may pose
potential negative impacts to various marine megafauna and important pelagic fishes. Microplastics with
size <1000 µm frequently founded on marine organism digestive tract [16,18,19,40], suggesting that
marine organisms likely mistake microplastics as their food [41]. Microplastics could disrupt digestive
tract function [17] and could also act as a vector for organic and heavy metal pollutants [21–23,42,43].
The most common form was fiber microplastics, similar to the findings by [28,33,44,45]. Fibrous plastic
particles in Sumba might derive from fishing nets and rope materials; granule comes from hard plastics
and granulated cleaner [45]. Based on FTIR analysis, most polymers identified were dominated
polyethylene, followed by dominated polypropylene and dominated polystyrene. The primary use of
polyethylene is packaging materials, e.g. food and beverage containers, geomembrane plastic bags and
film. Polypropylene is widely used in food and beverage containers, clothing industry, ropes, and re-
usable containers [46–48]. Surprisingly, polyamide fiber was also found in Sumba. This fiber might
-0,005
0,000
0,005
0,010
0,015
0,020
0,025
0,030
0,035
0,040
0,045
0,050
Absorbance
500 100 0 150 0 2000 250 0 300 0 3500 40 00 Wav enu mbers ( cm-1 )

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derived from fishing nets and rope material [49,50]. Despite the fact that plastics are newly developed
materials (early nineteen centuries made), our finding, that microplastics was found in seawater of
Sumba at all surveyed depth, indicated that plastic has invaded marine areas, including pristine areas. It
confirms the common believe that plastic waste has spread widely to different parts of the seas and
oceans, including remote and unknown areas [51].
4. Conclusion
Our study reports that microplastics were found in all sampling locations, in the form of fibers (45.45%),
granules (36.36%) and other form (18.18%). Most of the microplastic particles (81.82%) were found at
water depths less than 100m, which were thermocline area. However, no microplastics was observed at
100m depth. Most of identified microplastics (81.82%) were in 300-1000µm in size. Dominated plastics
polymers identified were polyethylene, followed by polypropylene, polystyrene, and polyamide. Further
studies are planned to examine microplastic distribution in the region where ITF presence and to
investigate the potential impact of microplastics in that area.
Acknowledgement
This study was part of Ekspedisi Widya Nusantara IX (EWIN-IX) funded by DIPA LIPI from the
Government of Indonesia. We would like to thank the support from all the crews of RV. Baruna Jaya
VIII during the EWIN-IX cruise. We also thank to Mr. Sumijo Hadi Riyono for the sample collection.
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