Exploring the pathology of liver, kidney, muscle, and stomach of fledgling seabirds associated with plastic ingestion.

There remain significant gaps in knowledge about 'sub-lethal' impacts of plastic ingestion, particularly chronic impacts on cells, tissues, or organs. Few studies have applied traditional animal health tools, such as histopathology, to assess physiological damage to wildlife, with fewer still providing information on the dosage or exposure to plastics needed to elicit negative effects. Our study seeks to investigate a common hypothesis in plastic pollution research; that an increasing plastics burden will have an impact on an animal's health, examining two wild species with high levels of environmental exposure to plastic through their diet. Here we assess the histopathology of the muscle, upper digestive tract, liver and kidney of two seabird species that are known to be commonly exposed to plastic, comparing exposed and non-exposed individuals. Fledgling seabirds showed histopathological evidence of cumulative pressures such as starvation, disease, and endoparasite burden. However, we observed no evidence of chronic harm that could be explicitly linked to the plastics. We found one case of haemorrhage, reaffirming that large/sharp plastic foreign bodies may cause acute physical damage. Given the numerous interacting pressures on the health of fledging seabirds, including exposure to plastic, this study highlights the need to scrutinise plastic-animal interactions and research though a One Health lens.

Cleaner seas: reducing marine pollution.

In the age of the Anthropocene, the ocean has typically been viewed as a sink for pollution. Pollution is varied, ranging from human-made plastics and pharmaceutical compounds, to human-altered abiotic factors, such as sediment and nutrient runoff. As global population, wealth and resource consumption continue to grow, so too does the amount of potential pollution produced. This presents us with a grand challenge which requires interdisciplinary knowledge to solve. There is sufficient data on the human health, social, economic, and environmental risks of marine pollution, resulting in increased awareness and motivation to address this global challenge, however a significant lag exists when implementing strategies to address this issue. This review draws upon the expertise of 17 experts from the fields of social sciences, marine science, visual arts, and Traditional and First Nations Knowledge Holders to present two futures; the Business-As-Usual, based on current trends and observations of growing marine pollution, and a More Sustainable Future, which imagines what our ocean could look like if we implemented current knowledge and technologies. We identify priority actions that governments, industry and consumers can implement at pollution sources, vectors and sinks, over the next decade to reduce marine pollution and steer us towards the More Sustainable Future. Supplementary Information: The online version contains supplementary material available at 10.1007/s11160-021-09674-8.

Minimal meso-plastics detected in Australian coastal reef fish.

Recording plastic ingestion across various species and spatial scales is key to elucidating the impact of plastic pollution on coastal and marine ecosystems. The effect of plastic ingestion on the diets, physiologies, and behaviors of selected fish species are well documented under laboratory settings. However, prevalence of plastic ingestion in wild fish across latitudinal gradients is yet to be widely documented; with a substantial lack of research in the Southern Hemisphere. We analyzed the gut content of reef fish across ~30o latitude of the east coast of Australia. Of 876 fish examined from 140 species (83 genera and 37 families), 12 individuals had visible (meso-plastics detectable to the naked eye) plastics present in the gut. Here, we present a first-look at plastic ingestion for coastal species with this region.

Seasonal ingestion of anthropogenic debris in an urban population of gulls.

Gulls are generalist seabirds, increasingly drawn to urban environments where many species take advantage of abundant food sources, such as landfill sites. Despite this, data on items ingested at these locations, including human refuse, is limited. Here we investigate ingestion of prey and anthropogenic debris items in boluses (regurgitated pellets) from Pacific Gulls (Larus pacificus). A total of 374 boluses were collected between 2018 and 2020 in Tasmania. Debris was present in 92.51% of boluses (n = 346), with plastic (86.63%, n = 324) and glass (64.71%, n = 242) being the most prominent types. An abundance of intact, household items (e.g., dental floss, food wrappers) suggest the gulls regularly feed at landfill sites. In addition, the boluses are deposited at a roosting site located within an important wetland, thus we propose that the gulls may be functioning as a previously unrecognised vector of anthropogenic debris from urban centres to aquatic environments.

A critical review of harm associated with plastic ingestion on vertebrates.

Studies documenting plastic ingestion in animals have increased in recent years. Many do not describe the less conspicuous, sub-lethal impacts of plastic ingestion, such as reduced body condition or physiological changes. This means the severity of this global problem may have been underestimated. We conducted a critical review on the sub-lethal impacts of plastic ingestion on marine vertebrates (excluding fish). We found 34 papers which tried to measure plastics' impact using a variety of tools, and less than half of these detected any impact. The most common tools used were visual observations and body condition indices. Tools that explore animal physiology, such as histopathology, are a promising future approach to uncover the sub-lethal impacts of plastic ingestion in vertebrates. We encourage exploring impacts on species beyond the marine environment, using multiple tools or approaches, and continued research to discern the hidden impacts of plastic on global wildlife.

Ingested plastic and trace element concentrations in Short-tailed Shearwaters (Ardenna tenuirostris).

Pollution of marine environments is concerning for complex trophic systems. Two anthropogenic stresses associated with marine pollution are the introduction of marine plastic and their associated chemicals (e.g., trace elements) which, when ingested, may cause harm to wildlife. Here we explore the relationship between plastic ingestion and trace element burden in the breast muscle of Short-tailed Shearwaters (Ardenna tenuirostris). We found no relationship between the amount of plastic ingested and trace element concentration in the birds' tissues. Though the mass and number of plastic items ingested by birds during 1969-2017 did not change significantly, trace element concentrations of some elements (Cu, Zn, As, Rb, Sr and Cd), appeared to have increased in birds sampled in 2017 compared to limited data from prior studies. We encourage policy which considers the data gleaned from this sentinel species to monitor the anthropogenic alteration of the marine environment.

Uncovering the sub-lethal impacts of plastic ingestion by shearwaters using fatty acid analysis.

Marine plastic pollution is increasing exponentially, impacting an expanding number of taxa each year across all trophic levels. Of all bird groups, seabirds display the highest plastic ingestion rates and are regarded as sentinels of pollution within their foraging regions. The consumption of plastic contributes to sub-lethal impacts (i.e. morbidity, starvation) in a handful of species. Additional data on these sub-lethal effects are needed urgently to better understand the scope and severity of the plastics issue. Here we explore the application of fatty acid (FA) analysis as a novel tool to investigate sub-lethal impacts of plastic ingestion on seabird body condition and health. Using gas chromatography-mass spectrometry, we identified 37 individual FAs within the adipose, breast muscle and liver of flesh-footed (Ardenna carneipes) and short-tailed (Ardenna tenuirostris) shearwaters. We found high amounts of FA 16:0, 18:0, 20:5n3 (eicosapentaenoic acid), 22:6n3 (docosahexaenoic acid) and 18:1n9 in both species; however, the overall FA composition of the two species differed significantly. In flesh-footed shearwaters, high amounts of saturated and mono-unsaturated FAs (needed for fast and slow release energy, respectively) in the adipose and muscle tissues were related to greater bird body mass. While total FAs were not related to the amount of plastic ingested in either species, these data are a valuable contribution to the limited literature on FAs in seabirds. We encourage studies to explore other analytical tools to detect these sub-lethal impacts of plastic.