Using citizen science to investigate the spatial-temporal distribution of floating marine litter in the waters around Taiwan

https://doi.org/10.1016/j.marpolbul.2020.111301Get rights and content

Highlights

  • The first citizen-science survey of floating marine litter in Taiwan

  • The marine litter density ranged from 0 to 4895 items/km2.

  • The sighting rate of marine litter was 69.1% of all transects.

  • Mean density of floating marine litter was 90.10 ± 8.60 items/km2.

Abstract

Marine litter is currently one of the most widespread pollutants. However, monitoring the spatial-temporal changes of floating marine litter remains challenging. In this study, with data collected by citizen scientists, we investigated the distribution and density of floating marine litter in the waters around Taiwan. With 40 volunteers surveying 978 transects in 410 cruises from December 2017 to December 2018, the overall survey area was approximately 121.26 km2 (5455 km in length). We found that the mean density of floating marine litter was 90.10 ± 8.60 items/km2 and that the majority was plastic (63.2%). Nearly 70% of the litter was found in 30% of the surveyed area. We also identified hotspots of floating marine litter, which are at the Northwestern and Southeastern regions of Taiwan. Our study highlights the contribution of citizen science to monitor floating marine litter and provides insight into the management of marine litter.

Introduction

Marine litter is considered one of the most severe pollutants in marine environments and is found in almost all marine environments, from the Arctic and Antarctic sea surfaces (Bergmann et al., 2016; Ryan et al., 2014) to the Mariana Trench (Chiba et al., 2018), which has a depth of 10,898 m. Marine litter is scattered on seashores, the sea surface, and the bottom of the ocean. Its distribution and accumulation are affected by hydrology, topography, prevailing wind and human activities (Pham et al., 2014). Marine litter is mainly concentrated near densely populated coastal areas and submarine canyons (Pham et al., 2014). In addition, the monitoring, prevention and removal of marine litter generate tremendous ecological, economic and social costs (NOAA/UNEP, 2011; Pham et al., 2014; Suaria and Aliani, 2014).

Understanding the causes and sources of floating marine litter is critical for marine litter reduction. The spatial distribution and density of floating marine litter may be related to the climate, environment, human population density, human activities, waste management systems, economic development and education level of the populations around an area (Díaz-Torres et al., 2017; Hidalgo-Ruz et al., 2018; Ourmieres et al., 2018). Investigation of the composition and characteristics of floating marine litter can help to identify its sources and related industries (e.g., fishery, marine aquaculture, and shipping industries) for the purposes of prevention and control (Díaz-Torres et al., 2017; Gutow et al., 2018; Hinojosa and Thiel, 2009). For example, with the identification of the country of origin, the paths of floating litter and even illegal disposal and illegal fisheries may be detected (Edyvane and Penny, 2017; Fujieda, 2003; Ko et al., 2018; Smith et al., 2018; Yoon et al., 2010). Understanding the sources of floating marine litter and identifying its potential threats can help to establish prevention and cleanup strategies (Arcangeli et al., 2018; Di-Méglio and Campana, 2017; Willis et al., 2017). Floating marine litter is also time dependent (Arcangeli et al., 2018; Thiel et al., 2003). Therefore, long-term monitoring of floating marine litter can help understand the seasonal and regional characteristics of and changes in litter density (Arcangeli et al., 2018; Hidalgo-Ruz et al., 2018; Thiel et al., 2003).

However, floating marine litter is difficult to monitor because of its wide distribution. Monitoring floating marine litter is often labor intensive and expensive. With limited resources, changes in the distribution of floating marine litter can be investigated using simulations based on hydrological conditions (Maximenko et al., 2012) or data collected by volunteers and ships of opportunity. Similar methods have been used for monitoring physical marine environmental variables (e.g., temperature) (Balfour et al., 2007; Emery et al., 1997; Robert Williams and Aiken, 1990) and marine pollution (Arthur et al., 2011; Brumovský et al., 2016). Compared to other marine environmental factors, marine litter is relatively easy to identify and measure. A little training is required to obtain quantitative information about marine litter (Bergmann et al., 2017). Thus, many studies have demonstrated that citizen scientists can increase the knowledge regarding marine litter (Nelms et al., 2017; Matsumura and Nasu, 1997; Richardson et al., 2017; TPMDS, 2017). However, the use of citizen science for investigating marine litter is more focused on coastal areas and beaches. The use of citizen science to investigate floating marine litter has been rare (Hidalgo-Ruz and Thiel, 2015).

Locating in the path of the Kuroshio Current, floating marine litter in the waters surrounding Taiwan not only affects the local marine ecology but is also likely to spread to the Pacific Ocean. Past studies have shown that the floating marine litter around Taiwan enters the North Pacific Gyre through the main Kuroshio Current and that the minimum time to reach the Great Pacific Garbage Patch is 250 days (Maximenko et al., 2012). A study at the Midway Atoll also showed that 18.8% of 325 lighters removed from the stomach contents of albatross chicks came from China and Taiwan (Fujieda, 2003).

Understanding the floating marine litter in the waters around Taiwan can help to identify the severity of litter pollution and its possible sources and to develop management and monitoring plans. However, the existing studies regarding the monitoring of marine litter in Taiwan are relatively inadequate; only surveys of coastal and regional marine litter density have been conducted (Kunz et al., 2016; Kuo and Huang, 2014; Walther et al., 2018). In this study, we used citizen science to investigate the types and amount of floating marine litter in the waters adjacent to Taiwan to understand the spatial-temporal distribution of floating marine litter and identify hotspots. This study supports the long-term and large-scale monitoring of floating marine litter. The outcome of this study will also assist in developing strategies to identify, monitor, and clean up hotspots of floating marine litter.

Section snippets

Study area

Our study area was the waters around Taiwan. Taiwan is an island country located in the western Pacific; the Kuroshio flows northeastward along eastern Taiwan year-round, and the Kuroshio Branch Current intrudes into the Taiwan Strait on the western side. The monsoon system is the driving force that changes the currents around the Taiwan Strait. In winter, the China Coastal Current is driven by the northeast monsoon entering the Taiwan Strait, and in summer, the South China Sea is affected by

Data collected by citizen scientists

From December 2017 to December 2018, the total survey time was 381 h 31 min. The survey distance was 5455 km, and the area surveyed was 121.26 km2.

The northernmost data were obtained from the Northeastern Taiwan, and the southernmost data came from the waters around the Spratly Islands. The highest number of surveys was conducted in Eastern Taiwan (297 surveys) and Northwestern Taiwan (272 surveys) (Fig. 3). A total of 4660 litter items were recorded, and the sighting rate was 69.1%. Except for

Factors affecting the density of floating marine litter

The highest density of floating marine litter (>316.64 items/km2) and floating marine litter accumulation zones in this study were mainly concentrated in the inshore waters between Cape Fugui and Cape Santiago on the northern coast of Taiwan. This pattern was consistent with a previous survey of beach litter in Taiwan, which also found that the highest accumulation of marine litter was in the northeastern corner (Greenpeace, 2019). The aggregation of marine litter in that area might be because

Conclusion

This study was the first large-scale survey of floating marine litter in the waters around Taiwan. We successfully constructed the spatial-temporal distribution and density of floating marine litter in the waters surrounding Taiwan with support from citizen scientists and limited time and resources for extensive surveys. Our study indicated that floating marine litter was abundant in the waters around Taiwan and that the majority of litter was plastic. We also identified the hotspots of

CRediT authorship contribution statement

Ching-Chun Chiu: Methodology, Software, Data curation, Writing - original draft. Chun-Pei Liao: Methodology, Data curation, Writing - review & editing. Ting-Chun Kuo: Methodology, Software, Writing - review & editing. Hsiang-Wen Huang: Conceptualization, Methodology, Resources, Supervision, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This study was supported by the Ministry of Science and Technology, Taiwan (MOST 106-2221-E-019-020). We thank the Taiwan Cetacean Society, TURUMOAN Whale-Watching Entertainment Co., Ltd., Kuroshio Ocean Education Foundation, Fisheries and Fishing Port Affairs Management Office, New Taipei City Government, Hiin Studio, and Blue Hole Dive Center for conducting ocean surveys and providing venues for volunteer meetings. The participation of all volunteers is sincerely appreciated.

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