Evaluating the Presence of Marine Litter in Cetaceans Stranded in the Balearic Islands (Western Mediterranean Sea)

Abstract

The global distribution and presence of plastic, at all levels of the water column, has made plastic debris one of today’s greatest environmental challenges. The ingestion and entanglement of plastic-containing marine debris has been documented in more than 60% of all cetacean species. In light of the increasing pressure on cetaceans, and the diversity of factors that they face, the aim of this work is to provide evidence of the impact of plastic debris on stranded cetaceans, in terms of ingestion and entanglement, in the Balearic Islands for the first-time. Detailed examinations, necropsies, and plastic debris analysis were performed on 30 of the 108 cetaceans stranded between 2019 and 2022. Specimens belonging to five different species, Stenella coeruleoalba, Tursiops truncatus, Grampus griseus, Balaenoptera physalus, and Physeter macrocephalus, were evaluated. Ten percent of the cetaceans (N = 3) presented plastic debris in their stomach, with one case of obstruction and perforation. Fishery gear fragments (ropes and nets) were found in two adults of T. truncatus, whereas packaging debris (plastic bag, packing straps, and plastic sheets) were found in a juvenile P. macrocephalus. Plastic items analysed by Fourier transform infrared spectroscopy (FT-IR) reported three polymer types: polypropylene, polyamide, and high-density polypropylene. A total of seven cases of entanglement were recorded during the study, affecting four different species (S. coeruleoalba, T. truncatus, P. macrocephalus, and Megaptera novaeangliae). Only two individuals were freed from the nets, although one died after a week, whereas the rest were already found dead. In conclusion, data collected in the present study provided evidence of plastic ingestion and entanglement in cetaceans of the Balearic Islands for the first-time, thus highlighting the need for the regular examination of stranded cetaceans (as they are top predators) in future research to better understand the effects of these pollutants.

Monitoring of seafloor litter on the Dutch Continental Shelf : International Bottom Trawl Survey 2023, Dutch Beam Trawl Survey 2022

“…According to Meijer et al (2021) between 0.8 to 2.7 million metric tonnes of postconsumer plastics enter the oceans solely by rivers every year. This has an impact on all groups of marine wildlife through effects such as ingestion, entanglement and interactions (Valderrama-Herrera et al 2023;Kühn et al 2022;Solomando et al 2022;Freitas et al 2023). Entanglement may limit movement and inflict injury, thus reducing an animal's ability to avoid predators, acquire food or increase the potential for drowning.…”

Impact of Plastic Pollution on Marine Biodiversity in Italy

“…Sperm whale, common bottlenose dolphin, and striped dolphin were the impacted cetacean species in Italian waters. The sperm whale is listed as a vulnerable species [55], for which entanglement and plastic ingestion have often been reported in the scientific literature [6,8]. P. macrocephalus has been proposed as an indicator of ocean health, showing the impact of macro-and micro-litter at the global scale [76].…”

“…The impact of plastic debris on marine fauna is growing in marine ecosystems, with adverse effects being documented for over 900 species [3,4] and across food webs [5]. The ingestion of plastic can lead to numerous adverse effects, including physical blockage or perforation of the gastrointestinal tract, a reduction in growth, and mortality [6][7][8]. The presence of plastic pollution in the marine ecosystem may result in the entanglement of wild species, potentially causing physical deformities in juvenile animals due to prolonged entanglement or leading to death in cases where individuals are unable to eat or breathe [9,10].…”

Identifying Potential High-Risk Zones for Land-Derived Plastic Litter to Marine Megafauna and Key Habitats within the North Atlantic

“…Most entanglement of cetaceans occurs in ALDFG (Simmonds, 2012;Solomando et al, 2022), although there have been incidences of entanglement in land-based litter including a plastic bag (Kelly, 2022), frisbees (Milman, 2020), synthetic clothing (Wells et al, 2008) and bailing twine (Balmer et al, 2019).…”