Microplastics in fecal samples of whale sharks (Rhincodon typus) and from surface water in the Philippines

Abstract

Marine plastic abundance has increased over the past 60 years and microplastics (< 5 mm) constitute a primary component of such litter. Filter-feeding megafauna, such as the whale shark, might be particularly affected by microplastic pollution as their feeding mode requires filtration of up to thousands of cubic meters of water. In addition, the habitat range of whale sharks intersects with several recognized microplastic pollution hotspots, among which is the Coral Triangle. Direct evidence for microplastic ingestion in whale sharks however, has not yet been presented. Here we show that whale shark scat collected in the Philippines from 2012 to 2019 contained a mean of 2.8 microplastics g− 1. Contrary to our expectations, the microplastic concentration in the scat remained consistent from 2012 to 2019. Water samples from the study site in 2019 indicated that the local microplastic pollution (5.83 particles m− 3) was higher than in surface waters in other whale shark habitats, but well below other pollution hot-spots found in Southeast Asia and China (range: 100–4100 particles m− 3). With the predicted growth in plastic use, leading to increased plastic marine pollution, whale sharks are expected to become more exposed to this form of pollution. To what extent microplastic ingestion impacts the overall health status of this endangered species remains an open question.

Cyto–Genotoxic Effect Causing Potential of Polystyrene Micro-Plastics in Terrestrial Plants

“…Micro-sized plastic particles can more easily absorbed and mobilized, and their bio-accumulation may result in toxic effects [15]. Ps-MP accumulation in aquatic ecosystems has been shown to cause slower growth and disrupted reproduction in marine gastropod Crepidula onyx [16], smaller sized eggs and reduced hatching in species of copepod (Calanus helgolandicus) [17], and physical damage to zooplanktons [18,19]. A reduced number of larvae and smaller size adults in water flea (Ceriodaphnia dubia), due to MP fibers interference in swimming, was observed by Ziajahromi et al [20], while a shorter lifespan in adult Pacific mole crabs (Emerita analoga) was reported by Horn et al [21].…”

Interactions between marine megafauna and plastic pollution in Southeast Asia

“…On the other hand, cartilaginous fishes remain particularly understudied at the family and species level for both ingestion (Provencher et al, 2017) and entanglement (Parton et al, 2019). While cartilaginous fishes appear to show the lowest frequency occurrence of plastic ingestion compared to the other taxonomic groups investigated here, this likely, is at least in part, resultant of the scarcity of studies published (Kühn and van Franeker, 2020), rather than their lack of interaction with marine plastics (Abreo et al, 2019a;Haetrakul et al, 2009;Parton et al, 2019;Yong et al, 2021). Although not always lethal, ingested plastics are known to impact physiological functioning and can lead to reduced body condition, through reduced growth or energy assimilation efficiency linked to the satiating impacts of plastics (Marn et al, 2020;Puskic et al, 2020).…”

“…It transpired through the expert elicitation that cases exist as unpublished for far more species than is currently described in the published literature, although new publications filling in those gaps have emerged since our literature search was performed (e.g. Gajanur and Jaafar, 2022;Ng et al, 2022;Prampramote et al, 2022;Yong et al, 2021). Green and leatherback turtles were the only two species for which published cases of both entanglement and ingestion were available from the SE Asian countries.…”

“…Hamza et al, 2016), making their montoring logistically challenging, which has led to considerable knowledge gaps existing in multiple areas of research in SE Asia, including in global studies on biologging (Bernard et al, 2021) and bycatch in fisheries (Pott and Wiedenfeld, 2017), for example. For cartilaginous fishes, whale sharks appear to be the main species of interest, with published and unpublished cases of entanglement and ingestion being available for the species in the region (Germanov et al, 2019;Yong et al, 2021). However, unlike marine mammals, dead stranded cartilaginous fishes are almost never necropsied in the Philippines, for example (Jo Marie Acebes, pers.…”

Field measurements reveal exposure risk to microplastic ingestion by filter-feeding megafauna

“…More research is needed to understand the risk of plastic ingestion to other ram-feeding megafauna including mobulid rays, and basking ( Cetorhinus maximus ) and megamouth sharks ( Megachasma pelagios ). Whale shark ( Rhincodon typus ) fecal samples have recently been shown to contain microplastics (mean: 2.8 microplastics g −1 feces) 77 . This, along with previous work that detected microplastic-derived contaminants in whale shark skin 78 , indicates that microplastic ingestion can be tracked using numerous techniques that when analyzed holistically, can clarify both the rate and the long-term effects of ingestion.…”