Exposure to microplastics affects fatty acid composition in the Japanese quail depending on sex and particle size

Plastic ingestion in birds is a widespread phenomenon of increasing concern. However, little is known about how exposure to microplastics (MP) affects the health of birds. In other organisms, MP exposure alters lipid metabolism and composition. If also true in birds, this could affect their fitness, especially since birds heavily rely on lipids during migration and egg production. Therefore, the aim of this study was to determine if ingestion of MP (polypropylene and polyethylene collected in nature) in two size ranges, large (3 mm) and small (<125 μm), affects lipid metabolism in the Japanese quail (Coturnix japonica). We orally exposed 55 one-week-old quail during 5 weeks to a total of 600 mg of MP in sizes of either large, small, or a mixture of both. After the exposure period, females fed small MP had higher liver masses compared to control females (on average ± SD, 8.95 ± 2.3 g vs. 6.34 ± 1.0 g), while liver lipid content did not differ in either males or females. The levels of monounsaturated fatty acids were lower in females exposed to large MP and the mixture of both MP sizes compared to controls. Females exposed to MP also had different levels of oleic- (18:1) and palmitoleic (16:1) acid compared to controls dependent on MP size. Exposure to small MP increased levels of palmitic- (16:0) and palmitoleic (16:1) acid in both males and females suggesting a possible increase in de novo fatty acid synthesis. Taken together, our results point towards a sex-specific sensitivity to MP as well as size-dependent MP effects on lipid metabolism in birds. Disruption of fatty acid composition could affect important life stages in female birds, such as migration and egg-laying. We stress the importance of further research focused on determining the mechanisms of action of MP on lipid metabolism.

A deuterium tracer experiment for simulating accumulation and elimination of organically bound tritium in an edible flatfish, olive flounder

Tritium (3H, T) is discharged by nuclear facilities into coastal oceans as tritiated water (HTO). When the concentration of HTO in seawater increases, the accumulation of organically bound tritium (OBT) in edible fish becomes a concern because of its longer residence time than HTO. To evaluate the accumulation potential of OBT in olive flounder (Paralichthys olivaceus), a commercially important edible fish in northeast Asia, we experimentally exposed the fish to seawater enriched with deuterium (2H, D) as a substitute for tritium. Progressive increases and decreases in the concentration of organically bound deuterium (OBD) were observed in the edible part (i.e., muscle) of the fish during the period of exposure to 2H (161 days) and the subsequent period of elimination of OBD (196 days). The measured concentration of OBD was analyzed using a newly developed single-compartment model to describe the metabolism of OBD in muscle via the following three transfer pathways: formation of OBD from 2H in water, elimination of OBD by catabolism, and ingestion of feed with natural abundance of OBD. The model estimates were in good agreement with the measured muscle OBD concentrations. The formation and elimination rate constants for OBD in the muscle were estimated by fitting our model to the measured data. The biological half-life of OBT in the muscle, estimated from the elimination rate constant, was 133 days, which was far longer than that of HTO in the free water of the muscle. Our model facilitates the estimation of OBT accumulation potential in olive flounder inhabiting coastal areas near nuclear facilities, and thus, will help to assess the radiation dose that humans are exposed to from ingesting seafood.

The significance of trophic transfer of microplastics in the accumulation of plastic additives in fish: An experimental study using brominated flame retardants and UV stabilizers

Marine organisms ingest microplastics directly from water and indirectly from food sources. Ingesting microplastics can lead to the accumulation of plastic-derived chemicals. However, the relative contributions of the two exposure routes to the accumulation of plastic-derived chemicals in organisms are unknown. Using microplastics containing two brominated flame retardants (BFRs; BDE209 and DBDPE) and three UV stabilizers (UVSs; UV-234, UV-327, and BP-12), we performed exposure experiments to compare chemical accumulation patterns in fish (Myoxocephalus brandti) between exposure from water and prey (Neomysis spp.). We found significantly higher concentrations of BFRs in fish fed microplastic-contaminated prey than fish exposed to microplastics in the water. However, we observed similar concentrations of UVSs in fish exposed to both sources. As BFRs are more hydrophobic than UVSs, the differences may reflect the hydrophobic nature of the additives. Our findings indicate that both exposure routes are crucial to understanding the accumulation of plastic additives in fish.

In situ experimental exposure of fruit-bearing shoots of apple trees to 13CO2 and construction of a dynamic transfer model of carbon

Evaluating the transfer and metabolism of carbon (C) in apple fruit is key to estimating the potential accumulation of atmospheric ¹⁴C in fruit near and around nuclear facilities. We developed a dynamic compartment model for apple fruit-bearing shoots, assuming that the shoots are a simple unit of source and sink for photoassimilates. Fruit-bearing shoots of Malus domestica "Fuji" at different fruit growth stages were exposed to ¹³CO₂in situ, followed by sampling at 72 h after exposure or at harvest. The ¹³C/(¹³C+¹²C) mole ratio in fruits, leaves, and current branch were measured to construct a five-compartment model of ¹³C (fruit, each fast and slow component of leaves, and current branch). The C inventories in the compartments were presented in accordance with the measured growth curves of C in the organs. The model simulated the ¹³C dynamics in plant tissues well. Simulation results of photoassimilate distribution using the model indicated that the retention of photoassimilated C at the harvest depended on the growth rate of C in the organs at the exposure.

Biological effects of marine diesel oil exposure in red king crab (Paralithodes camtschaticus) assessed through a water and foodborne exposure experiment

Shipping activities are expected to increase in the Arctic Seas. Today, the majority of vessels are using marine diesel oil (MDO) as propulsion fuel. However, there is a general lack of knowledge of how cold-water marine species respond to acute exposures to MDO. Arctic red king crabs (Paralithodes camtschaticus) were exposed to mechanically dispersed MDO in a flow-through exposure system for one week followed by three weeks of recovery. Observations of increased movements in exposed crabs were interpreted as avoidance behaviour. Further, glutathione peroxidase activity increased in high exposed crab, the catalase activity showed an insignificant increase with exposure, while no differences between groups were observed for lipid peroxidation and acetylcholinesterase activity. After three weeks of recovery in clean seawater, polycyclic aromatic hydrocarbons concentrations in the crabs were significantly reduced, with no specific biomarker responses in exposed groups compared to the control. The results suggest that effects from instantaneous MDO spill only will have short-term effects on the red king crab.