Food-web transfer of microplastics between wild caught fish and crustaceans in East China Sea

Highlights

• MP pollution is ubiquitous marine fish and crustacean species in the East China Sea.

• MPs were predominantly fiber-shaped, blue, and composed of polyester.

• Marine organisms which occupy higher trophic levels are suitable MP indicator species.

Abstract

Plastic pollution, including microplastics (MPs), poses a global threat to environmental and human health. Studies on the transference of MPs along marine food webs are limited. In the present study, we investigated MP pollution in 11 wild fish species (193 individuals) and 8 wild crustacean species (136 individuals) captured from the Zhoushan fishing ground, off the East China Sea. The average abundance of MPs found in two main tissues, the gill and gastrointestinal (GI) tract, were 0.77 ± 1.25 and 0.52 ± 0.90 items/individual, respectively. The MPs we found were predominantly fiber-shaped, blue, and composed of polyester polymers. Our results suggest that MP pollution is ubiquitous in the East China Sea. We suggest that MPs are likely aggregated in the higher trophic level fish species throughout the marine food web. Furthermore, we suggest that marine organisms which occupy higher trophic levels might be suitable MP indicator species.

Introduction

Marine plastic pollution poses a considerable threat to marine ecosystems across the globe (Dubaish and Liebezeit, 2012; Collignon et al., 2012; Desforges et al., 2014), from the tropical equator to the poles (Obbard et al., 2014; Lusher et al., 2015; Bergmann et al., 2017; Tekman et al., 2016). Microplastics (MPs) are plastics <5 mm in diameter (Andrady, 2011). Primary microplastics are manufactured as microbeads, fragments, fibers or pellets, and secondary microplastics was derived from the breakdown of macroplastics, which are retained in a range of marine and freshwater ecosystems, and from inter-tidal to abyssal environments (Andrady, 2011; Cole et al., 2011; Ja and Costa, 2014). Previous field studies have reported severe plastic pollution in seas and oceans around the world, such as the Pacific Ocean (Hipfner et al., 2018), Amazon River estuary (Pegado et al., 2018), Mediterranean Sea (Bellas et al., 2016; Güven et al., 2017; Romeo et al., 2015; Romeo et al., 2016), and the Arctic Ocean (Morgana et al., 2018). Peng et al. (2017) reported a concentration of up to 121 ± 9 MP items per kg of dry weight in the sedimentary environment of the Changjiang Estuary. In addition, Xu et al. (2018) recorded an average concentration of 23.1 ± 18.2 MP items/100 L in surface waters of the East China Sea. MPs are commonly entangled and ingested by plankton, crustaceans, fish, turtles and seabirds, leading to physical injury (including internal and/or external abrasions and ulcers, starvation, and smothering) (Gassel et al., 2013) and physiological effects (including reduced growth rates, blockage of enzyme production, diminished feeding stimulus, and reproductive failure) (Lusher et al., 2013). Boerger et al. (2010) reported an average abundance of 2.1 ± 5.78 MP items per fish among six fish species collected in the North Pacific Central Gyre. Comparatively, Cannon et al. (2016) recorded low MP contamination in 21 fish species from the Southern Hemisphere, two acrylic resins were identified. Ingestion of MPs was also identified in a study of Norway lobsters; plastic pollution was recorded in up to 83% of the stomachs of studied animals (Murray and Cowie, 2011). However, investigations into the abundance of MPs in wild fish species along Chinese coastal areas remain scarce. Jabeen et al. (2017) examined fish samples purchased from a local fishery market in Shanghai and found an abundance of 1.1–7.2 MP items/individual. It is difficult to ascertain whether these samples were contaminated by MPs before being purchased, and the data may therefore not reflect actual pollution exposure in the ocean. Given the potential threat of MPs to the health of the marine environment, information regarding the abundance of MPs ingested by marine organisms is required urgently.

A few studies that are available show that marine MPs are ubiquitous in the East China Sea. Hence, we investigated MPs in wild caught fish and crustacean from the Zhoushan fishing ground to add our understanding of the abundance of MPs in wild marine organisms. Zhoushan fishing fround was the largest fishing ground in China, where occupied frequent fishing activity. Data recorded by continuous plankton recorders demonstrated fisheries played a major part in plastic pollution (Ostle et al., 2019). In addition, we hypothesized that MPs may be transferred up the marine food chain through different trophic levels (TLs) (Setälä et al., 2014; Farrell and Nelson, 2013). Commonly, producers (green plants) are the first TL, followed by herbivores, primary carnivores, secondary carnivores, and top carnivores. Several controlled-feeding studies have been conducted that demonstrate the trophic transfer of MPs along artificial food chains in laboratory settings (Santana et al., 2017; Farrell and Nelson, 2013). Many harmful chemical substances or phycotoxins can leak from MPs as they are transferred through the marine food web (Lithner et al., 2009), and studies that investigate TLs are highly valued (Pauly et al., 2001).

Our study aimed to increase knowledge regarding the distribution of MPs and to quantify variability among different species. We measured the potential of different marine organisms to ingest MPs and evaluated the potential for MPs to enter the marine food chain. Overall, we aimed to ascertain the relationship between MP abundance and TL in marine organisms from the East China Sea.