Radioactive impacts of the Fukushima Dai-ichi Nuclear Power Plant Accident on blue sharks in the Northwest Pacific

The Fukushima Dai-ichi Nuclear Power Plant Accident (FDNPPA) derived ¹³⁴Cs, ¹³⁷Cs and ^110mAg in blue sharks captured in the Northwest Pacific during 2011-2018 were assessed for the first time in the aspects of radioactive contamination, temporal variation, maternal-to-fetus transfer, tissue distribution and radiation dose, to demonstrate the impacts of the FDNPPA on blue sharks. The contribution of the FDNPPA derived radiocesium in blue sharks (>52%) was estimated based on ¹³⁴Cs/¹³⁷Cs_{activity ratios}. The effective and ecological half-lives of the FDNPPA derived ¹³⁴Cs (270 d, 410 d), and ¹³⁷Cs (430 d, 450 d) were calculated. These contaminations decreased with time and returned to the level before the FDNPPA during the period of Sep. 2017-Sep. 2018.¹³⁴Cs and ¹³⁷Cs tended to distribute in muscles, while ^110mAg mainly distribute in their guts. ¹³⁴Cs and ¹³⁷Cs were also transferred to fetuses and the activities were up to ~30% of the maternal activities. Dose assessment demonstrated that the highest FDNPPA derived dose rate in blue sharks (~0.42 nGy/h) was far below the ERICA ecosystem screening benchmark of 10 μGy/h and the committed effective dose in humans from ingesting blue shark meat (0.06-0.90 μSv) was far less than that from annual consumption of food and water. It was far from causing radiation harm to blue sharks and humans, suggesting that the impacts of the FDNPPA on blue sharks were not significant.

Plastic ingestion by blue shark Prionace glauca in the South Pacific Ocean (south of the Peruvian Sea)

The present study documented for the first time data on plastic ingestion by Prionace glauca in the South Pacific Ocean, south of the Peruvian Sea. In total, 136 individuals were studied between 2015 and 2016. Their size ranged from 61.5 to 255.0 cm TL. Pieces of plastic bags were found in the stomach contents, corresponding to the 2.2% of the individuals. The mean number of ingested plastics was 0.02. The polymer type identified by FT-IR for the pieces of plastics bags was polyethylene.

First data on plastic ingestion by blue sharks (Prionace glauca) from the Ligurian Sea (North-Western Mediterranean Sea)

Few studies have focused so far on plastic ingestion by sharks in the Mediterranean Sea. The aim of this paper was to determine, for the first time, the plastic litter ingested by blue sharks (Prionace glauca), categorized as "Critically Endangered" in the Mediterranean Sea by IUCN, caught in the Pelagos Sanctuary SPAMI (North-Western Mediterranean Sea). The analysis of the stomach contents was performed following the MSFD Descriptor 10 standard protocol implemented with FT-IR spectroscopy technique. The results showed that 25.26% of sharks ingested plastic debris of wide scale of sizes from microplastics (<5 mm) to macroplastics (>25 mm). The polyethylene sheetlike user plastics, widely used as packaging material, are the most ingested debris. This research raises a warning alarm on the impact of plastic debris on a threatened species, with a key role in the food web, and adds important information for futures mitigation actions.