Leatherback turtles: the menace of plastic

A best practice framework for assessing plastic ingestion in marine turtles

The ingestion of plastic debris has been reported in all seven marine turtle species, affecting vital processes throughout their entire life cycle and key habitats. Consequently, this emerging threat has been recognized as a priority conservation concern. The potential health impacts range from cryptic sublethal effects to severe injury and death. A comprehensive understanding of these impacts and the processes involved, at both the individual and population levels, is crucial for evaluating the vulnerability of marine turtles to plastic pollution. Aiming to guide researchers and stakeholders from the initial stages of project development, this study discusses essential components for establishing and achieving research on plastic ingestion in marine turtles. Drawing on diverse efforts globally, this manuscript compiles the most common approaches and established methodologies, while evaluating resource availability and capabilities, to outline a globally applicable best practice framework for designing and implementing research and monitoring initiatives on plastic ingestion impacts to marine turtles.

Long-term observations of microplastic and mesoplastic distribution on sandy beaches in north-east Taiwan: Impact of typhoons on spatial and temporal variability

Plastic pollution in coastal environments poses ecological risks, yet long-term monitoring data and insights into the impacts of extreme weather events remain limited. This study examines the spatiotemporal distribution of microplastics and mesoplastics on sandy beaches, with a focus on long-term trends and the influence of typhoons. Samples were collected from two beaches in northern Taiwan over a 20-month period, spanning 8-9 sampling sessions per site. A dense grid sampling approach (50 × 50 cm quadrats) was used across three transects. Post-typhoon microplastic abundances peaked at 5080.6 pcs/kg dry weight (d.w.) at Xialiao Beach, where the average concentration was 115.3 pcs/kg d.w., compared to 18.1 pcs/kg d.w. at Longmen Beach. Typhoon events increased plastic particle accumulation, primarily along storm lines and backshore areas, but long-term accumulation was not observed, indicating dynamic deposition and removal processes. These findings emphasize the need for long-term monitoring through repeated sampling campaigns conducted over an extended period, and high-resolution monitoring using a dense sampling grid, to accurately assess plastic pollution. Single-event studies risk misrepresenting pollution levels due to spatial and temporal variability.

Further characterization of adrenocortical and thyroid hormone concentrations of leatherback turtles (Dermochelys coriacea) under various stressors, including validation of a plasma aldosterone assay

Leatherback turtles (Dermochelys coriacea) are endangered by anthropogenic threats. Characterizing the physiologic response of leatherback turtles under various stressors may inform conservation strategies. In this study, a commercially available enzyme immunoassay for aldosterone was validated for leatherback turtle plasma, and it was used with previously validated assays for corticosterone and free thyroxine (fT4) to evaluate the physiologic status of leatherback turtles that were entangled in fishing gear, stranded on shore, nesting or intentionally captured at sea during ecologic studies. Mean aldosterone concentrations were significantly higher in entangled turtles (156 ± 102 pg/ml), stranded turtles (274 ± 165 pg/ml) and intentionally captured turtles (457 ± 464 pg/ml) than in nesting females (23 ± 16 pg/ml). In contrast, nesting females had higher fT4 (2.9 ± 0.6 pg/ml) compared to entangled turtles (0.8 ± 0.9 pg/ml), stranded turtles (0.7 ± 0.8 pg/ml) and intentionally captured turtles (0.3 ± 0.2 pg/ml). Corticosterone concentrations were significantly higher in stranded individuals (10.9 ± 6.6 ng/ml) compared with nesting (3.8 ± 2.0 ng/ml) and intentionally captured turtles (3.6 ± 2.5 ng/ml), with intermediate levels in entangled turtles (5.1 ± 2.8 ng/ml). This study provides additional insight into the variable physiologic status of leatherback turtles under the influence of different anthropogenic and natural stressors, and it provides an additional tool to evaluate the role of aldosterone in the acute stress response and health of endangered sea turtle species.

Little change in plastic loads in South Atlantic seabirds since the 1980s

Despite growing concern about the large amounts of waste plastic in marine ecosystems, evidence of an increase in the amount of floating plastic at sea has been mixed. Both at-sea surveys and ingested plastic loads in seabirds show inconsistent evidence of significant increases in the amount of plastic since the 1980s. We use 3727 brown skua Catharacta antarctica regurgitations, each containing the remains of a single seabird, to monitor changes in plastic loads in four seabird taxa breeding at Inaccessible Island, Tristan da Cunha in nine years from 1987 to 2018. Frequency of occurrence in plastic ingestion and types were compared across four near-decadal time periods (1987-1989; 1999-2004; 2009-2014 and 2018) while loads were compared among years. The number and proportions of industrial pellets among ingested plastic decreased consistently over the study period in all four taxa, suggesting that industry initiatives to reduce pellet leakage have reduced the numbers of pellets at sea. Despite global plastic production increasing more than four-fold over the study period, there was no consistent increase in the total amount of ingested plastic in any species. Plastic loads in great shearwaters Ardenna gravis, which spend the austral winter in the North Atlantic Ocean, increased in 2018, but the proportion of shearwaters containing plastic decreased. We conclude that the density of plastic floating at sea has not increased in line with global production over the last 30 years.

The impact of chronic and acute problems on sea turtles: The consequences of the oil spill and ingestion of anthropogenic debris on the tropical semi-arid coast of Ceará, Brazil

Sea turtle mortality is often related to materials that reach the coast from different anthropic activities worldwide. This study aimed to investigate whether sea turtle mortality was related to older marine problems, such as solid waste, or one of the largest oil spill accidents on the Brazilian coast, that occurred in 2019. We posed three questions: 1) Are there solid residues in the digestive tract samples, and which typology is the most abundant? 2) Can meso‑ and macro-waste marine pollutants cause mortality? 3) Is the dark material found really oil? A total of 25 gastrointestinal content (GC) samples were obtained, of which 22 ingested waste of anthropogenic origin and 18 were necropsied. These 22 samples were obtained during or after the 2019 oil spill, of which 17 specimens were affected, making it possible to suggest oil ingestion with the cause of death in the animals that could be necropsied. Macroscopic data showed that the most abundant solid waste was plastic (76.05 %), followed by fabrics (12.18 %) and oil-like materials. However, chemical data confirmed only three specimens with oil levels ranging from remnants to high. It was possible to infer possible causes of death in 16 of the total 18 necropsied cases: Most deaths were due to respiratory arrest (62.5 %), followed by pulmonary edema (12.5 %), cachexia syndrome (12.5 %), circulatory shock (6.25 %), and head trauma (6.25 %), which may have been caused by contact with solid waste, oil, or both. The study showed that not all dark material found in the GCs of turtles killed in oiled areas is truly oil, and in this sense, a chemical analysis step to prove the evidence of oil must be added to international protocols.

Marine turtles as bio-indicators of plastic pollution in the eastern Mediterranean

The loggerhead turtle (Caretta caretta) has been suggested as a bio-indicator species for plastic pollution. However, detailed investigations in the eastern Mediterranean are limited. Here, we present data from loggerhead turtles (2012-2022; n = 131) of which 42.7 % (n = 57) had ingested macroplastic (pieces ≥ 5 mm). Frequency of occurrence (%) was not found to have changed over time, with body size (CCL cm), between stranded or bycaught turtles, or with levels of digesta present. The characteristics of ingested plastic (n = 492) were largely sheetlike (62 %), clear (41 %) or white (25 %) and the most common polymers identified were Polypropylene (37 %) and Polyethylene (35 %). Strong selectivity was displayed towards certain types, colours and shapes. Data are also presented for posthatchling turtles (n = 4), an understudied life stage. Much larger sample sizes will be needed for this species to be an effective bio-indicator, with the consideration of monitoring green turtles (Chelonia mydas) for the eastern Mediterranean recommended allowing a more holistic picture to be gathered.

First successful head-start program of leatherback sea turtles (Dermochelys coriacea) in Thailand and proposed dietary strategy

Leatherback sea turtle (Dermochelys coriacea) hatchlings have previously been kept alive for over a year in captive conditions but these were the few survivors of initially larger groups. In this report, newly hatched leatherback sea turtles were randomly harvested from two nests in Thailand and successfully reared before release back to the wild. In captivity, the survival of the turtles decreased sharply during the first 4 or 5 months, and then steadied until the end of the 12-month trial. The survival of yearlings from one nest was 13.3% and from the other nest 46.7%. Their growth was exponential, reaching 1.36-3.35 kg (n = 9) at the end of program. The causes of death of the reared turtles were accidents (25.0-38.5%) and infections from water and live food (61.5-75.0%). The dietary requirements of the turtles were investigated by determining the digestibility of protein and carbohydrate in vitro, using enzymes from the digestive tracts of hatchlings that had died in an accident (70.1-92.9 g body weight). The results indicated that the most suitable source of protein was wheat gluten, followed by soybean meal, nonruminant meat and bone meal, fish meal, nonruminant meat meal, pork meal, and skimmed milk, while suitable carbohydrate sources were mashed cassava, corn, wheat flour, and alpha starch, followed by cereal meal and rice flour. Findings from the current report provide a practical protocol for head-starting leatherback sea turtles, and indicate the possible basis of an effective artificial diet for this species.

A critical review on the evaluation of toxicity and ecological risk assessment of plastics in the marine environment

The increasing production of plastics together with the insufficient waste management has led to massive pollution by plastic debris in the marine environment. Contrary to other known pollutants, plastic has the potential to induce three types of toxic effects: physical (e.g intestinal injuries), chemical (e.g leaching of toxic additives) and biological (e.g transfer of pathogenic microorganisms). This critical review questions our capability to give an effective ecological risk assessment, based on an ever-growing number of scientific articles in the last two decades acknowledging toxic effects at all levels of biological integration, from the molecular to the population level. Numerous biases in terms of concentration, size, shape, composition and microbial colonization revealed how toxicity and ecotoxicity tests are still not adapted to this peculiar pollutant. Suggestions to improve the relevance of plastic toxicity studies and standards are disclosed with a view to support future appropriate legislation.

The microscopic threat with a macroscopic impact: Microplastics along the southeast Florida reef tract

Microplastics decrease oceanic water quality and negatively impact marine life. This research quantified and classified marine plastic pollution along the Southeast Florida Reef Tract (SEFRT) to estimate the risk of microplastic damage to corals in this region. Surface and bottom water samples were collected at seven sites along the SEFRT over the course of six months and were analyzed for microplastic content. FTIR spectrophotometry was used to evaluate microplastic composition. Overall, seven plastic polymers were found across a total of 1204 microplastic items. Five contaminants were also identified, indicating that microplastics may be congregators of these hazardous contaminants. Significantly more total plastics were found in surface samples than in bottom samples, but plastic quantities were not significantly different when month, depth, and location were combined. Plastics were determined to have entered the ocean from multiple sources; in order to protect vulnerable reef ecosystems in this area, a two-factor approach is necessary to halt the release of microplastics into the ocean, including widespread plastic clean-up efforts and improvements to plastic waste management.

Review of microplastics in museum specimens: An under-utilized tool to better understand the Plasticene

This study summarises the status of microplastic research in marine and freshwater specimens in natural museum collections around the world. Abundances, distributions, and types of microplastics in the archived collections are discussed. Museum collections can fill knowledge gaps on evolution of microplastic pollution before and during the Plasticene era. The specimens in these studies, ranging from plankton to vertebrates, were collected and archived between 1900 and 2019, and are dominated by specimens from marine ecosystems. All the specimens included in this review were preserved by freezing or in ethanol/formaldehyde except for specimens in one study that were preserved via cryomilling. Microfibers were the most common microplastics in the reviewed studies. We recommend more microplastic studies over a wider taxonomic range of species and across a longer span of years utilizing archival specimen collections around the world in order to establish reference points and develop temporal trends for microplastic pollution of the environment.

Natal Origin and Spatiotemporal Distribution of Leatherback Turtle (Dermochelys coriacea) Strandings at a Foraging Hotspot in Temperate Waters of the Southwest Atlantic Ocean

Leatherback turtles migrate long distances between nesting beaches and distant foraging areas worldwide. This study analyzes the genetic diversity, life history stage, spatiotemporal distribution, and associated threats of a foraging aggregation in the Southwest Atlantic Ocean. A total of 242 leatherbacks stranded or bycaught by artisanal fisheries were recorded from 1997 to 2021 in Uruguay, with sizes ranging from 110.0 to 170.0 cm carapace lengths, indicating that the aggregation is composed of large juveniles and adults. Results of Bayesian mixed-stock analysis show that leatherbacks come primarily from the West African rookeries, based on mitochondrial DNA sequences obtained from 59 of the turtles representing seven haplotypes, including a novel one (Dc1.7). The main threat identified in the area is the fisheries bycatch but most of the carcasses observed were badly decomposed. There was significant seasonal and interannual variability in strandings that is likely associated with the availability of prey and the intensity of the fishing effort. Taken together, these findings reinforce the importance of these South American foraging areas for leatherbacks and the need to determine regional habitat use and migratory routes across the broader Atlantic region, in order to develop effective conservation measures to mitigate threats both at nesting beaches and foraging areas.

Laboratory simulated aging methods, mechanisms and characteristic changes of microplastics: A review

Microplastics (MPs) aging occurs in all environmental medias and affects the environmental behaviour and toxicity of MPs. Due to the extremely slow process of aging, laboratory simulated aging methods have had to be used to research the properties, behaviour, toxicity and effects of aged MPs. However, multiple laboratory aging methods with different mechanisms have led to divergent viewpoints on the characteristics, behavior and toxicity of aged MPs. Therefore, this paper reviewed the main laboratory MPs aging methods and mechanism, including those that involve UV, advanced oxidation processes (AOPs), sunlight or simulated sunlight, chemical treatment, heat, plasma radiation, etc. As a technology with a low time cost, AOPs have potential and are recommended. Physical, chemical, and coupled aging significantly alter MPs surface topography and functional groups, which affect MPs adsorption, migration and toxicity. However, the effects of aging on environmental behaviour and toxicity are highly uncertain. The carbonyl index (CI) and O/C ratio are generally applied to evaluate the MPs aging degree. This review highlights the need to provide adequate information on coupled simulated aging methods to allow better elucidation of the underlying mechanisms of aging and its effect on MPs environmental behaviour and toxicity.

The leatherback turtle (Dermochelys coriacea) and plastics in the Northwest Atlantic ocean: A hazard assessment

Atlantic leatherback turtles are faced with multiple threats, such as ship strikes, pollution and predation, throughout their annual migratory routes in the Northwest (NW) Atlantic. The risks associated with encounters with floating and submerged plastic debris are currently unknown. This study is a hazard assessment of plastics for this turtle's sub-population, using 2010-2019 data from the national Great Canadian Shoreline Cleanup (GSCS) program, therefore potential exposure, and published evidence on the interactions of plastics and leatherbacks, hence potential effects. The type of plastic items and their abundance along shorelines of three Atlantic Provinces - Nova Scotia (NS), Prince Edward Island (PEI), Newfoundland and Labrador (NL) - were evaluated and compared to plastic items known to interact with leatherbacks. During the 2010-2019 period, a total of 220,590 plastic items were collected from 578 sites, representing 1264 km of shoreline. Plastic bags and rope are in the top ten most common items found on shorelines of NS, PEI, and NL. Pot gear and trap nets are in the top ten for PEI and are the 14th most common plastic item found on all shorelines. Cigarette debris is also commonly found. From the literature, plastic bags, pot gear and trap nets, and rope are known to adversely affect leatherbacks. Assuming that a large proportion of the shoreline debris comes in from the sea, after being in coastal waters for unknown periods, the study shows that such items pose a hazard to leatherbacks through ingestion and entanglement, based on published studies. Evidence is now needed on actual exposure at sea to the most common items to establish the ecological risk of plastics to these turtles in NW Atlantic waters.

Junk food: Polymer composition of macroplastic marine debris ingested by green and loggerhead sea turtles from the Gulf of Oman

Pollution of the marine environment by plastic marine debris has become one of the most pervasive threats impacting marine environments. In this study, for the first time, we evaluate the polymer types of the plastic marine debris ingested by 49 green and 14 loggerhead sea turtle strandings in the Gulf of Oman. Plastic marine debris was ingested by 73.5% of green and 42.9% of loggerhead sea turtles in this study. Overall, evidence suggested that green sea turtles from the Gulf of Oman coast of the United Arab Emirates ingested high levels of plastic marine debris, predominantly Polypropylene (PP) & Polyethylene (PE), followed by Nylon, PP-PE mixture, Polystyrene (PS), Poly vinyl chloride (PVC) and Ethylene vinyl acetate (EVA), respectively. Loggerhead sea turtles also ingested high levels of plastic marine debris, which also predominantly consisted of PP & PE, followed by PP-PE mixture, Nylon and PS. While recent studies were directed into polymer characterization of micro-plastics in aquatic life, our study focuses on macro-plastics which impose significantly greater risks.

30 years trends of microplastic pollution: Mass-quantitative analysis of archived mussel samples from the North and Baltic Seas

Microplastics (MP) are ubiquitous throughout the environment as a result of an ongoing, increasing, but also lavish use, of plastics over time and its inherent persistence. In contrast, there are almost no data that allow drawing conclusions about the evolution of plastic pollution in the environment over the past decades. This study investigates the MP load in blue mussels from the North and Baltic Sea archived by the German Environmental Specimen Bank in a time series covering almost 30 years. Samples were enzymatically and chemically oxidative digested for MP extraction and subsequent analyzed mass-quantitatively for nine common polymer clusters by pyrolysis gas chromatography-mass spectrometry. Seven polymer clusters were detected in mussel tissue. Summed MP levels were at ppm levels (<20 μg/g mussel, dry weight). North Sea samples reflected a gradual increase from the 1980s/90s to the 2000s whereas those from Baltic Sea showed consistently higher, rather constant MP levels similar to the North Sea site later than 2000. Polymer composition of both sites stood out by cluster (C) of C-PVC and C-PET at both sites. Mussels from Baltic Sea site had larger C-PE and C-PP proportions. Opposed polymer- and site-specific trends indicated both regional and trans-regional MP sources for different polymer clusters. The MP composition of mussels showed strong similarities with adjacent sediment and water samples. The study introduces a relevant dataset addressing the temporal development of MP pollution. It emphasizes a high indicative potential of environmental MP composition/loads received by mussels but raises the necessity on adequate control materials accompany such kind of studies.

Ingestion and characterization of plastic debris by loggerhead sea turtle, Caretta caretta, in the Balearic Islands

Plastic waste has become ubiquitous pollutants in seas and oceans and can affect a wide range of species. For some marine species, plastic debris could pose a considerable threat through entanglement, ingestion, and habitat degradation and loss. Sea turtles are one of the most sensitive species, as their migratory behaviour and multifaceted life cycles make these reptiles especially vulnerable to the negative effects of plastic debris. The present study aimed to assess the amount and composition of plastic debris ingested by loggerhead turtles (Caretta caretta, Linnaeus, 1758) in the Balearic Islands Sea, thusly providing new information to complete the knowledge for this topic. In this work, 45 stranded dead C. caretta specimens were necropsied, and their digestive tract content analysed for the presence of plastic debris. Plastic objects were observed in 27 individuals (60.0%), with an average of 12.7 ± 4.7 plastic items per turtle. Litter in the faecal pellet was also monitored in 67 living individuals, observing plastic elements in 46 (68.7%) of the specimens, reporting an average of 9.7 ± 3.3 plastic elements per individual. Overall, 785 plastic items were found, measured, weighed and categorized according to size, colour, shape, and type of polymer. The main elements ingested were plastic sheets that were found in 65.3% of the turtles analysed, being white (42.7%) and transparent (29.2%) the most predominant colours. Most elements were macroplastics (59.3%), while microplastics were not found. Fourier Transform Infrared Spectrometry (FT-IR) analysis showed that high-density polyethylene and polypropylene were the main polymer plastics, representing 42.3% and 33.8% of the total, respectively. In conclusion, the high occurrence of plastic debris determined in the present study evidenced for the first time plastic ingestion in loggerhead turtles in the Balearic Islands, and highlights C. caretta as a bioindicator organism for marine pollution.

Litter ingestion and entanglement in green turtles: An analysis of two decades of stranding events in the NE Atlantic

Survivorship of early life stages is key for the well-being of sea turtle populations, yet studies on animals that distribute around oceanic areas are very challenging. So far, the information on green turtles (Chelonia mydas) that use the open NE Atlantic as feeding grounds is scarce. Strandings occurring in oceanic archipelagos can provide relevant information about the biology, ecology and current anthropogenic pressures for megafauna inhabiting the open ocean. In this study, we analysed stranding events of green turtles found in the Azores archipelago to investigate interactions with marine litter. In addition, we quantified and characterized litter items stranded on beaches to provide a direct comparison between the ingested items with the debris found in the environment. A total of 21 juvenile green turtles were found stranded in the region between 2000 and 2020 (size range: 12-49 cm, CCL). Overall, 14% of the animals were entangled in marine litter and 86% of the turtles necropsied had ingested plastic. The mean abundance of items ingested was 27.86 ± 23.40 and 98% were white/transparent. Hard plastic fragments between 1 and 25 mm were the most common shape recovered in the turtles, similarly to what was found on the coastline. All of the litter items analysed with pyrolysis GC-MS revealed to be polyethylene (PE). This study provides the first baseline assessment of interactions of plastic litter with juvenile green turtles found at the east edge of the North Atlantic Subtropical Gyre. The combination of these results supports the hypothesis that migratory megafauna that use remote oceanic islands as a feeding ground are exposed to anthropogenic litter contamination dominated by plastics, even when these regions are located far away from big industrial centers or populated cities.

First evidence of presence of plastic debris in digestive system of Mola mola (L.) from western Mediterranean Sea

Ingestion of marine debris by ocean sunfishes is not very well documented. As the feeding behaviour of these giants of the seas is very similar to marine turtles, it is expected that the accidental ingestion of plastics could be registered in these species of fish. With this work it is noticed for the first time the presence of a blue plastic fragment, classified by its size as a mesoplastic, in the digestive system of Mola mola (L.) (Molidae) from western Mediterranean Sea.

Junk food: Interspecific and intraspecific distinctions in marine debris ingestion by marine turtles

The pervasiveness of marine debris is now considered one of the most persistent changes in marine environments. This study reports marine debris ingested by green sea turtles Chelonia mydas and loggerhead sea turtles Caretta caretta that stranded along the eastern coast of the Sharjah Emirate in the United Arab Emirates. We observed that both green and loggerhead sea turtles frequently ingest (Frequency of Occurrence: 75.0% and 57.1% respectively) high quantities of marine debris, particularly plastics. The results suggest that green sea turtles are more likely to ingest soft items such as threads and sheets while loggerheads are more likely to ingest hard items. When considering the quantity, frequency and nature of ingested marine debris as well as the physiology of specific species and age classes, green sea turtles, particularly younger specimens, ingest the greatest amount of marine debris.

Plastic ingestion by green turtles (Chelonia mydas) over 33 years along the coast of Texas, USA

Despite exponential growth of anthropogenic marine debris in recent decades, plastic ingestion by marine turtles in the Gulf of Mexico is not well understood. Gastrointestinal tracts were examined from 464 green turtles that stranded in Texas between 1987 and 2019, and 226 turtles ingested plastic (48.7%). This number doubled from 32.5% in 1987-1999 to 65.5% in 2019, but mass of ingested items was lowest in 2019. No turtles showed evidence of death directly related to plastic ingestion. Compared to other regions, plastic ingestion was low. Small turtles (<25 cm straight carapace length) ingested plastic more frequently and in greater amounts than larger turtles. Small turtles also ingested more hard plastic while larger turtles ingested more sheet-like and thread-like plastics, which may correspond to size-based habitat shifts. This is among the largest marine turtle ingestion studies to date and demonstrates an increasing prevalence of plastic ingestion.

Comparison of the polarization contrast of gelatinous zooplankton and a transparent single-use plastic bag-Implications for marine animals

Plastic pollution in the ocean is an increasingly detrimental issue for marine organisms. As a form of polarized light pollution, transparent plastic debris may be more visible and pose additional threats to organisms that can detect and interpret polarized light. Plastic can mimic the visual features of common marine prey items, such as transparent gelatinous zooplankton, which may lead to more significant plastic ingestion. We measured, in situ, the polarization and radiance contrast between a transparent plastic bag and gelatinous zooplankton with an underwater video polarimeter. The plastic bag had significantly higher polarization contrast than the gelatinous zooplankton, yet both shared similar radiance contrasts. This higher polarization contrast may contribute to the observed high ingestion rates of transparent plastic by marine organisms. Further study into the connection between polarization-sensitive organisms and plastic ingestion is recommended.

Postmortem investigations on leatherback sea turtles (Dermochelys coriacea) stranded in the Canary Islands (Spain) (1998-2017): Evidence of anthropogenic impacts

Opportunities for postmortem studies on leatherback sea turtles (Dermochelys coriacea) are infrequent due to their predominantly pelagic life history. In this study, the pathological findings and causes of mortality of 13 leatherback turtles stranded in the Canary Islands, Spain, from 1998 to 2017, are described. In addition, concentrations of Se, As, Cd, Pb, Hg, 15 rare earth elements (REE) and other 4 minor elements (ME), 41 persistent organic pollutants, and 16 polycyclic aromatic hydrocarbons in hepatic samples from 5 leatherbacks were determined. 84.62% of the turtles died possibly due to anthropogenic causes (entanglement/fishing interaction - 46.15%; boat strike - 23.07%; plastic ingestion - 15.38%). Although Se, As, and Cd were found at higher hepatic concentrations than those reported for leatherbacks from other locations, no acute lesions were detected. This is the first report of exposure to REE-ME in sea turtles. Organic contaminant hepatic concentrations were generally low or undetectable.

An ecotoxicological approach to microplastics on terrestrial and aquatic organisms: A systematic review in assessment, monitoring and biological impact

Marine and land plastic debris biodegrades at micro- and nanoscales through progressive fragmentation. Oceanographic model studies confirm the presence of up to ∼2.41 million tons of microplastics across the Atlantic, Pacific, and Indian subtropical gyres. Microplastics distribute from primary (e.g., exfoliating cleansers) and secondary (e.g., chemical deterioration) sources in the environment. This anthropogenic phenomenon poses a threat to the flora and fauna of terrestrial and aquatic ecosystems as ingestion and entanglement cases increase over time. This review focuses on the impact of microplastics across taxa at suggested environmentally relevant concentrations, and advances the groundwork for future ecotoxicological-based research on microplastics including the main points: (i) adhesion of chemical pollutants (e.g., PCBs); (ii) biological effects (e.g., bioaccumulation, biomagnification, biotransportation) in terrestrial and aquatic organisms; (iii) physico-chemical properties (e.g., polybrominated diphenyl ethers) and biodegradation pathways in the environment (e.g., chemical stress, heat stress); and (iv) an ecotoxicological prospect for optimized impact assessments.

Plastic ingestion by freshwater turtles: a review and call to action

Plastic pollution, and especially plastic ingestion by animals, is a serious global issue. This problem is well documented in marine systems, but it is relatively understudied in freshwater systems. For turtles, it is unknown how plastic ingestion compares between marine and non-marine species. We review the relevant turtle dietary literature, and find that plastic ingestion is reported for all 7 marine turtle species, but only 5 of 352 non-marine turtle species. In the last 10 years, despite marine turtles representing just 2% of all turtle species, almost 50% of relevant turtle dietary studies involved only marine turtles. These results suggest that the potential threat of plastic ingestion is poorly studied in non-marine turtles. We also examine plastic ingestion frequency in a freshwater turtle population, finding that 7.7% of 65 turtles had ingested plastic. However, plastic-resembling organic material would have inflated our frequency results up to 40% higher were it not for verification using Raman spectroscopy. Additionally, we showcase how non-native turtles can be used as a proxy for understanding the potential for plastic ingestion by co-occurring native turtles of conservation concern. We conclude with recommendations for how scientists studying non-marine turtles can improve the implementation, quality, and discoverability of plastic ingestion research.

Microplastics in the environment: Occurrence, perils, and eradication

Microplastics (MPs) with sizes < 5 mm are found in various compositions, shapes, morphologies, and textures that are the major sources of environmental pollution. The fraction of MPs in total weight of plastic accumulation around the world is predicted to be 13.2% by 2060. These micron-sized MPs are hazardous to marine species, birds, animals, soil creatures and humans due to their occurrence in air, water, soil, indoor dust and food items. The present review covers discussions on the damaging effects of MPs on the environment and their removal techniques including biodegradation, adsorption, catalytic, photocatalytic degradation, coagulation, filtration and electro-coagulation. The main techniques used to analyze the structural and surface changes such as cracks, holes and erosion post the degradation processes are FTIR and SEM analysis. In addition, reduction in plastic molecular weight by the microbes implies disintegration of MPs. Adsorptive removal by the magnetic adsorbent promises complete elimination while the biodegradable catalysts could remove 70-100% of MPs. Catalytic degradation via advanced oxidation assisted by S O 4 • - or O H • radicals generated by peroxymonosulfate or sodium sulfate are also adequately covered in addition to photocatalysis. The chemical methods such as sol-gel, agglomeration, and coagulation in conjunction with other physical methods are discussed concerning the drinking water/wastewater/sludge treatments. The efficacy, merits and demerits of the currently used removal approaches are reviewed that will be helpful in developing more sophisticated technologies for the complete mitigation of MPs from the environment.

Online media reveals a global problem of discarded containers as deadly traps for animals

The widespread occurrence of litter is a severe threat to global ecosystems. We have analyzed online media, to assess the diversity of animals that are prone to getting trapped in discarded containers and check which kind of containers is the most common trap for animals. A total of 503 records from around the world (51 countries, 6 continents) have been found. These include invertebrates (17 taxa, ca.1050 dead individuals), and vertebrates (98 taxa, 496 individuals including 44 carcasses). The latter group was most frequently represented by mammals (78.5% of all cases), then reptiles (15.3%), birds (1.2%), fish (1.0%) and amphibians (0.4%). Nearly 12.5% of the determined vertebrates are classified as vulnerable, endangered or critically endangered, according to the IUCN. Although most trapped individuals were smaller animals, bigger ones such as monitor lizards (Varanus spp.) or large carnivores were also recorded. In most cases, animals were trapped in glass or plastic jars (32.4%), drink cans (16.5%), and steel cans (16.3%). Our results demonstrate that discarded containers can be a threat to all major groups of animals. In order to address this phenomenon, it is necessary to decrease a global production of debris, implement container deposit legislation and organize repeatable cleanup actions.

Leatherback sea turtle (Dermochelys coriacea) hatch success and essential and nonessential metals in eggs and embryos from nests in St. Kitts (2015)

Northwest Atlantic leatherback sea turtles (Dermochelys coriacea) are endangered and low hatch success limits potential for population recovery. We examined essential and nonessential metal concentrations in 43 eggs from nests on St. Kitts to determine if there was a relationship with hatch success. Whole homogenized embryos and undeveloped eggs contained detectable concentrations of arsenic, barium, copper, iron, selenium, vanadium, and zinc, but not beryllium, cadmium, chromium, cobalt, lead, mercury, molybdenum, and thallium. Of detected metals, only vanadium concentrations negatively correlated with hatch success (P = 0.01). Manganese and vanadium were associated with pneumonia occurring in the nest, and arsenic with renal mineralization. This study adds to the knowledge regarding baseline values for environmental contaminants in sea turtles, supporting the trend that leatherback eggs have relatively low concentrations of toxic metals, lacking a strong relationship with hatch success, and normally contain the essential elements copper, iron, selenium, and zinc.

Understanding individual and population-level effects of plastic pollution on marine megafauna

Plastic pollution is increasing rapidly throughout the world’s oceans and is considered a major threat to marine wildlife and ecosystems. Although known to cause lethal or sub-lethal effects to vulnerable marine megafauna, population-level impacts of plastic pollution have not been thoroughly investigated. Here, we compiled and evaluated information from peer-reviewed studies that reported deleterious individual-level effects of plastic pollution on air-breathing marine megafauna (i.e. seabirds, marine mammals, and sea turtles) worldwide, highlighting those that assessed potential population-level effects. Lethal and sub-lethal individual-level effects included drowning, starvation, gastrointestinal tract damage, malnutrition, physical injury, reduced mobility, and physiological stress, resulting in reduced energy acquisition and assimilation, compromised health, reproductive impairment, and mortality. We found 47 studies published between 1969 and 2020 that considered population-level effects of plastic entanglement (n = 26), ingestion (n = 19), or both (n = 2). Of these, 7 inferred population-level effects (n = 6, entanglement; n = 1, ingestion), whereas 19 lacked evidence for effects (n = 12, entanglement; n = 6, ingestion; n = 1, both). However, no study in the past 50 yr reported direct evidence of population-level effects. Despite increased interest in and awareness of the presence of plastic pollution throughout the world’s oceans, the extent and magnitude of demographic impacts on marine megafauna remains largely unassessed and therefore unknown, in contrast to well-documented effects on individuals. Addressing this major assessment gap will allow researchers and managers to compare relative effects of multiple threats—including plastic pollution—on marine megafauna populations, thus providing appropriate context for strategic conservation priority-setting.

Insights into catalytic removal and separation of attached metals from natural-aged microplastics by magnetic biochar activating oxidation process

Natural-aged microplastics with changed surface properties accumulate, redistribute and spread in all water fields as carriers of hazardous substances. The combined hazard of co-contamination of microplastics and hazardous substances expands the ecological risks, which urgently needs to design treatment schemes for pollutant removal from microplastics. In this paper, a facile and applicable magnetic biochar with porosity and graphitization (PGMB) was prepared for realizing the goal of metal removal from the microplastics. Heterogeneous catalysis of persulfate (PS) activated by PGMB achieved the decomposition of organics, with the decrease of more than 60% of the attached Pb on the surface of microplastics, and the adsorbed metal amount by PGMB in this system (31.29 mg/g) is much higher than that by the individual PGMB group (7.07 mg/g). Analysis demonstrated that the organic layer covered on the microplastic surface over the long-term weathering provided the key sites for metal sorption, whose decomposition and peeling were the critical steps in whole process. The prepared PGMB was responsible for activating PS to produce reactive species for decomposing the organic matter accompanied with detaching metals from microplastic surface, also would keep the role for re-adsorption of the released metals and separation from aqueous phase by magnetic force. The influences of natural environmental factors including salinity, common matrix species, and temperature on the performance of PGMB/PS system for metal removal from microplastics were discussed to illustrate the universality of the scheme in saline or organic-rich waters. The results of this study provided underlying insights for removing metals from microplastic surface, and decreasing the harm risks in the co-contamination of microplastics and hazardous substances.

Plastic pellets trigger feeding responses in sea anemones

Multiple mechanisms for plastic consumption by marine animals have been proposed based on the feeding cues and behavior of the animal studied. We investigated plastic consumption in sea anemones. We found that anemones readily consumed pristine National Institute of Standards and Technology low-density polyethylene and high-density polyethylene II and III pre-production pellets. Anemone weight, crown area, and number of tentacles were measured before and after 12 days of daily pellet consumption. Crown area significantly increased for control anemones only. Fresh anemones were then sequentially fed consumed and egested pellets from two of the earlier daily trials to measure feeding retention time, which decreased over three to four feedings. The concentrations of elements in anemones (zinc, iron, arsenic, manganese, chromium, copper, vanadium, selenium, nickel, cadmium, and cobalt) were similar to control anemones that were not exposed to pellets. Lead concentrations were significantly higher in anemones fed HDPE III pellets as compared to control. Plastic consumption by marine animals might be reduced by reducing the amount of plastic that enters the ocean and understanding the chemical triggers underlying plastic consumption.

Heavy metals contamination of sedimentary microplastics in Hong Kong

This is the first study of heavy metals (As, Zn, Cd, Ni, Fe, Mn, Cu) contamination of microplastics on sandy beaches in Hong Kong. Three study sites are located in the eastern waters (Pak Lap Wan, Stanley Bay, Tung Lung Chau) and the other three in the western waters (Tai Pai Tsui, Ha Pak Nai, Shui Hau Wan). The three most abundant types of microplastics were polyethylene (42.2%), polypropylene (23.3%) and polystyrene (19.5%). The median concentration of Fe (302 mg kg^-1) was the highest and followed by Zn (19.6 mg kg^-1) and Mn (18.6 mg kg^-1). Very low concentrations of Cu (0.89 mg kg^-1), Ni (0.15 mg kg^-1), As (<LOD) and Cd (<LOD) were measured. The western sites have significantly higher concentrations of Ni, Fe, Mn and Cu than the eastern sites, indicating that Pearl River was likely to be a major source of heavy metals on microplastics. In view of a continual increase in the abundance of microplastics in the marine environment and its potential impacts on marine organisms, immediate actions should be taken in establishing long term monitoring programs for heavy metals associated with microplastics. In-depth research on the mechanisms of adsorption and desorption processes between metals and microplastics will help assess the associated risks to both human health and the environment.

A preliminary study of the interactions between microplastics and citrate-coated silver nanoparticles in aquatic environments

Microplastics and silver nanoparticles (AgNPs) are considered two emerging environmental contaminants that have adverse effects on aquatic environments. Knowledge on the interactions between AgNPs and microplastics may improve our understanding of these pollutants, posing to surrounding environments and public health. However, current knowledge regarding this issue is limited. Here, we investigate, for the first time, the interactions between AgNPs and the microplastics polyethylene (PE), polypropylene (PP), and polystyrene (PS) in aquatic environments. Results showed no significant interactions between AgNPs and PE or PP microplastics. However, AgNPs were efficiently removed by PS microplastics. These differences are mainly attributed to the presence of π-π interactions. Meanwhile, AgNPs aggregations were generated due to higher concentrations of leaching additives derived from PS microplastics. Interestingly, AgNPs are significantly captured on PS microplastic surfaces in the form of Ag⁰ rather than Ag⁺. The capture process is a monolayer adsorption and influenced greatly by the mass ratio of AgNPs and PS microplastics. These observations may provide a novel environmental fate of AgNPs, and indicate a new potential method for their removal to some degree. These findings demonstrate the complexities of AgNPs absorption onto microplastics and enhance present understanding of interactions between nanoparticles and microplastics in aquatic environments.

The potential of microplastics as carriers of metals

Microplastics can adsorb chemical pollutants such as metals or pharmaceuticals, and transferred them along the food chain. In this work, an investigation of the adsorption of Cd, Co, Cr, Cu, Ni, Pb and Zn by five different types of microplastics was performed in Milli-Q water and natural waters (seawater, urban wastewater and irrigation water) via a series of batch adsorption experiments. The effects of concentration of metals and physicochemical characteristics of polymers were particularly studied. Results revealed a significant adsorption of lead, chromium and zinc on microplastics, especially on polyethylene and polyvinyl chloride. In the case of polyethylene terephthalate, it showed little adsorption capacity. Specific surface, porosity and morphology are characteristics that affect the molecular interactions. The adsorption isotherms were better described by Langmuir model, which indicates that the main adsorption mechanism might be chemical adsorption. Finally, results obtained in natural waters indicated that dissolved organic matter may play a major role on metal adsorption on microplastics. Results showed an enhancement of metal adsorption in waters with high chemical and biological oxygen demands as urban wastewater and irrigation water.

In Vitro Genotoxicity of Polystyrene Nanoparticles on the Human Fibroblast Hs27 Cell Line

Several studies have provided information on environmental nanoplastic particles/debris, but the in vitro cyto-genotoxicity is still insufficiently characterized. The aim of this study is to analyze the effects of polystyrene nanoparticles (PNPs) in the Hs27 cell line. The viability of Hs27 cells was determined following exposure at different time windows and PNP concentrations. The genotoxic effects of the PNPs were evaluated by the cytokinesis-block micronucleus (CBMN) assay after exposure to PNPs. We performed ROS analysis on HS27 cells to detect reactive oxygen species at different times and treatments in the presence of PNPs alone and PNPs added to the Crocus sativus L. extract. The different parameters of the CBMN test showed DNA damage, resulting in the increased formation of micronuclei and nuclear buds. We noted a greater increase in ROS production in the short treatment times, in contrast, PNPs added to Crocus sativus showed the ability to extract, thus reducing ROS production. Finally, the SEM-EDX analysis showed a three-dimensional structure of the PNPs with an elemental composition given by C and O. This work defines PNP toxicity resulting in DNA damage and underlines the emerging problem of polystyrene nanoparticles, which extends transversely from the environment to humans; further studies are needed to clarify the internalization process.

Diet-related selectivity of macroplastic ingestion in green turtles (Chelonia mydas) in the eastern Mediterranean

Understanding the drivers of key interactions between marine vertebrates and plastic pollution is now considered a research priority. Sea turtles are primarily visual predators, with the ability to discriminate according to colour and shape; therefore these factors play a role in feeding choices. Classification methodologies of ingested plastic currently do not record these variables, however here, refined protocols allow us to test the hypothesis that plastic is selectively ingested when it resembles the food items of green turtles (Chelonia mydas). Turtles in the eastern Mediterranean displayed strong diet-related selectivity towards certain types (sheet and threadlike), colours (black, clear and green) and shapes (linear items strongly preferred) of plastic when compared to the environmental baseline of plastic beach debris. There was a significant negative relationship between size of turtle (curved carapace length) and number/mass of plastic pieces ingested, which may be explained through naivety and/or ontogenetic shifts in diet. Further investigation in other species and sites are needed to more fully ascertain the role of selectivity in plastic ingestion in this marine vertebrate group.

Fatal Photobacterium damselae-induced enteritis in a leatherback turtle Dermochelys coriacea

Stranded leatherback turtle Dermochelys coriacea complete pathology reports are rare, and the cause of mortality is difficult to determine in many cases. We conducted a complete pathological study of a stranded leatherback turtle from the western Mediterranean. The main finding was a fibrino-necrotizing enteritis with associated bacteria which were identified as Photobacterium damselae subsp. damselae according to biochemical and phenotypical characteristics. This report provides evidence of the pathogenic effect of this bacterium in wild sea turtles.

The rise in ocean plastics evidenced from a 60-year time series

Plastic production has increased exponentially since its use became widespread in the 1950s. This has led to increased concern as plastics have become prevalent in the oceanic environment, and evidence of their impacts on marine organisms and human health has been highlighted. Despite their prevalence, very few long-term (>40 years) records of the distribution and temporal trends of plastics in the world's oceans exist. Here we present a new time series, from 1957 to 2016 and covering over 6.5 million nautical miles, based on records of when plastics have become entangled on a towed marine sampler. This consistent time series provides some of the earliest records of plastic entanglement, and is the first to confirm a significant increase in open ocean plastics in recent decades.

Ingestion of plastic marine litter by sea turtles in southern Brazil: abundance, characteristics and potential selectivity

The ingestion of plastic marine litter (PML) by sea turtles is widespread and concerning, and the five species that occur in the southwestern Atlantic - green, loggerhead, olive ridley, leatherback and hawksbill - are vulnerable to this pollution. Here, we quantified and characterized PML ingested by these species in southern Brazil, and observed PML ingestion in 49 of 86 sampled individuals (~57.0%). Green turtles presented the highest rates and variety of ingested plastics, and such ingestion has been high at least since 1997. Omnivorous turtles presented higher PML ingestion than carnivorous ones. Loggerheads displayed a negative correlation between body size and number of ingested items. Green turtles ingested mostly flexible transparent and flexible/hard white plastics; loggerheads ate mainly flexible, hard and foam fragments, in white and black/brown colors. These results help us better understand PML ingestion by sea turtles, highlighting the seriousness of this threat and providing information for prevention and mitigation strategies.

Modeling the active dispersal of juvenile leatherback turtles in the North Atlantic Ocean

BACKGROUND

The Northwest Atlantic (NWA) leatherback turtle (Dermochelys coriacea) subpopulation is one of the last healthy ones on Earth. Its conservation is thus of major importance for the conservation of the species itself. While adults are relatively well monitored, pelagic juveniles remain largely unobserved. In an attempt to reduce this knowledge gap, this paper presents the first detailed simulation of the open ocean dispersal of juveniles born on the main nesting beaches of French Guiana and Suriname (FGS).

METHODS

Dispersal is simulated using STAMM, an Individual Based Model in which juveniles actively disperse under the combined effects of oceanic currents and habitat-driven movements. For comparison purposes, passive dispersal under the sole effect of oceanic currents is also simulated.

RESULTS

Simulation results show that oceanic currents lead juveniles to cross the Atlantic at mid-latitudes. Unlike passive individuals, active juveniles undertake important north-south seasonal migrations while crossing the North Atlantic. They finally reach the European or North African coast and enter the Mediterranean Sea. Less than 4-year-old active turtles first arrive off Mauritania. Other productive areas on the eastern side of the Atlantic (the coast of Galicia and Portugal, the Gulf of Cadiz, the Bay of Biscay) and in the Mediterranean Sea are first reached by 6 to 9-year-old individuals. This active dispersal scheme, and its timing, appear to be consistent with all available stranding and bycatch data gathered on the Atlantic and Mediterranean coasts of Europe and North Africa. Simulation results also suggest that the timing of the dispersal and the quality of the habitats encountered by juveniles can, at least partly, explain why the NWA leatherback subpopulation is doing much better than the West Pacific one.

CONCLUSION

This paper provides the first detailed simulation of the spatial and temporal distribution of juvenile leatherback turtles dispersing from their FGS nesting beaches into the North Atlantic Ocean and Mediterranean Sea. Simulation results, corroborated by stranding and bycatch data, pinpoint several important developmental areas on the eastern side of the Atlantic Ocean and in the Mediterranean Sea. These results shall help focus observation and conservation efforts in these critical areas.

Pressure and impact of anthropogenic litter on marine and estuarine reptiles: an updated "blacklist" highlighting gaps of evidence

We report an arrangement on the effect of anthropogenic litter on marine and estuarine reptiles, checking for evidence about different types of impact (ingestion vs. entanglement) and pressure (three size-based categories). From 1976 to 2018, we obtained a "blacklist" of 11 species impacted by marine litter (about 13% of 85 species of marine and estuarine reptiles), belonging to three orders (Testudines, Squamata, and Crocodilia). We obtained only occasional evidence of an impact for Squamata (Hidrophis elegans, Disteira major) and Crocodilia (Crocodylus porosus). Regarding the different types of pressure, the highest number of evidence has been obtained for macro-litter (10 species) and the lowest for micro-litter (4 species, all Chelonidae). Among Testudines, Lepidochelys kempii and Natator depressus evidenced a lack of data for micro-plastic. In Squamata, information is lacking for micro-plastic with only occasional references for meso-plastic (in Hydrophis elegans) and macro-plastic (Disteira major and Crocodylus porosus). We obtained a direct correlation between the research effort and the number of citations regarding different types of pressure and impact of marine litter: therefore, our blacklist of impacted species could be increased, carrying out further research focused on other poorly studied marine and estuarine reptiles. We suggest the use of a standardized nomenclature to reduce the amount of lost information.

Levels of trace metals on microplastic particles in beach sediments of the island of Vis, Adriatic Sea, Croatia

The aim of this study was to determine the levels of trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in plastic pellets collected from two sandy beaches on the island of Vis, Croatia. A total of 92 pellets in a sediment volume of 3965 mL were collected at the investigated sampling sites. Concentrations of pellets in sediment samples ranged from 6 to 36 particles dm^-3 of wet sediment. Mean particle weight of the collected beached pellets ranged from 17 mg to 31 mg. Trace metal concentrations in plastic pellets were greater than the concentrations reported for seawater in the investigated area, which indicates that plastic pellets sorb metals from the marine environment. The adsorbed trace metals may enter the food chain due to incidental ingestion of microplastic particles by marine animals, which presents a potential human health risk due to consumption of seafood.

Quantities of Marine Debris Ingested by Sea Turtles: Global Meta-Analysis Highlights Need for Standardized Data Reporting Methods and Reveals Relative Risk

Because of their propensity to ingest debris, sea turtles are excellent bioindicators of the global marine debris problem. This review covers five decades of research on debris ingestion in sea turtles from 131 studies with a novel focus on quantities. Previous reviews have focused solely on presence/absence data. Past reviews have called for standardization and highlight biases in the literature, yet none thoroughly describe improvements needed at the data reporting stage. Consequences of three reporting choices are discussed: not reporting quantities of ingested debris (32% of sea turtle studies reported only frequency of occurrence), excluding animals that did not ingest debris (64%), and not normalizing quantities to animal size (95%). Ingestion quantities, corrected for these factors, allowed a first-ever global meta-analysis on the units of grams/kilogram, revealing that hawksbill and green turtles rank highest among sea turtle species, and that the Central and Northwest Pacific and Southwest Atlantic Oceans are hotspots. Furthermore, this review discovered that monitoring efforts are disproportionate to the magnitude of the problem. Large efforts are focused in the Mediterranean Sea where international policies are hotly discussed versus the Central Pacific that has 5-fold greater debris ingestion quantities but represents only 3% of the global research effort. Future studies are recommended to report quantities of ingested debris using units described herein and make use of the pilot database provided.

Distribution and composition of floating macro litter off the Azores archipelago and Madeira (NE Atlantic) using opportunistic surveys

The distribution and composition of macro litter floating around oceanic islands is poorly known, especially in the North Atlantic. Due to its isolated location at the fringe of the North Atlantic subtropical gyre, the Azores archipelago has recently been proposed as a potential retention zone for floating litter. To further investigate this assumption, opportunistic surveys from pole-and-line tuna fishing boats were performed from 2015 to 2017 to document (1) the distribution and (2) the composition of the floating macro litter present off the Azores and Madeira islands. Among the 2406 visual transects, 482 floating debris were recorded and were mainly composed of general plastic user items (48%), plastic packaging (21%) and derelict fishing gears (18%). Average number of debris per transect was 0.19 ± 0.5, with a total number ranging between 0 and 5 items per transect. For the majority of transects (84%), no debris was observed, 13% of the transects contained a single item, and only 3% contained more than one item. Although debris between 2.5 and 5 cm were recorded, 93% of the debris were larger than 5 cm. The GLMs showed strong effect of the observer (p < 0.001) and the standardized densities accounting for the observer bias were higher (1.39 ± 0.14 items.km^-2) than the observed densities (0.78 ± 0.07 items.km^-2). Debris densities were however relatively low and tended to aggregate around the Central group of the Azores (standardized mean: 0.90 ± 0.20 items.km^-2). Our findings therefore suggest that most of the debris might originate from far away land-based sources and from fishing activities. This study highlights the potential of fisheries observer programs to obtain cost-effective information on floating macro debris that are essential to support the implementation of the European Marine Strategy Framework Directive.

Ingested Micronizing Plastic Particle Compositions and Size Distributions within Stranded Post-Hatchling Sea Turtles

From July 2015 to November 2016, 96 post-hatchling sea turtles were collected from 118 km of the Atlantic coastline in Florida, USA, including loggerhead, green, and hawksbill sea turtle species. Forty-five of the recovered turtles were rehabilitated and released, but the remaining 52 died and were frozen. At necropsy, the gastrointestinal tracts of most the turtles contained visible plastic, and collected particles of 27 individuals were chemically characterized by Raman microscopy as polyethylene, polypropylene, polyethylene terephthalate, and polystyrene. Mesoparticle plastic fragments 1.0-8.7 mm, microparticle fragments 20-1000 μm, and nanoparticles 5-169 nm were identified in the turtles. Polyethylene and polypropylene were the most common plastics ingested from specimens representing 54.1 and 23.7% of the total observed mesoparticles and 11.7 and 21.0% of the total observed microparticles, respectively. A plastic-to-body mass ratio of 2.07 mg/g was determined for this group. The authors suggest that ingestion of micronizing plastic by post-hatchling sea turtles is likely a substantial risk to survival of these endangered and threatened species. This study also provides some of the first evidence for the formation of nanoscopic plastic particles that we theorize forms in the post-hatchling and juvenile environment and are present post-ingestion.