Distribution and risk assessment of microplastics in water, sediment and brine shrimps in a remote salt lake on the Tibetan Plateau, China.

Microplastics (MPs) are pervasive environmental contaminants that have infiltrated even the most remote ecosystems. Despite their widespread distribution, the transfer patterns and impacts of MPs in remote lakes remain poorly understood. This study aimed to address the knowledge gap regarding the pathways and consequences of MP pollution in these isolated environments. Focusing on Kyêbxang Co, a remote salt lake in Tibet, this study investigated the transfer patterns, sources and ecological impacts of MPs, providing insights into their mobility and fate in pristine ecosystems. Water, sediment and biota (brine shrimp) samples from Kyêbxang Co, collected during the summer of 2020, were analyzed using µ-Raman spectroscopy to determine MP abundances, polymer types and potential sources. Findings indicated significant MP contamination in all examined media, with concentrations highlighting the role of runoff in transporting MPs to remote locations. The majority of detected MPs were small fragments (<0.5 mm), constituting over 93 %, with polypropylene being the predominant polymer type. The presence of a halocline may slow the descent of MPs, potentially increasing the exposure and ingestion risk to brine shrimp. Despite the currently low ecological risk estimated for MPs, this study underscores the need for long-term monitoring and development of a comprehensive ecological risk assessment model for MPs.

Distribution and potential sources of microplastics in sediments in remote lakes of Tibet, China.

The prevalence of microplastics in water bodies such as oceans and rivers has received considerable attention in recent years. The present study contributes to this research effort by assessing microplastics in 12 remote lakes on the Tibetan Plateau, China. Despite the limited extent of human activities, at least 17 items and up to 2644 items of microplastics were found per kg of dried sediments collected from the lakes in Tibet. These values were considered high compared to the levels of microplastics reported in other lake areas worldwide. Our results showed that the most prevailing types of microplastics in the sediments were black or transparent fibers in the size range of 0.05-0.5 mm, which were mainly identified to be polyamide and polyethylene terephthalate using Fourier-transform infrared microspectroscopy. The number of microplastics found appeared to be higher in sediments with a higher silt and clay content. Atmospheric long-range transport, glacial meltwater and surface runoff represent potential pathways to carry microplastics from elsewhere to the remote lakes in Tibet. This study shall be of great significance in understanding the transport and distribution of microplastics in the environment at regional or global scale.

Morphological and molecular study on Yininemertespratensis (Nemertea, Pilidiophora, Heteronemertea) from the Han River Estuary, South Korea, and its phylogenetic position within the family Lineidae.

Outbreaks of ribbon worms observed in 2013, 2015, and 2017-2019 in the Han River Estuary, South Korea, have caused damage to local glass-eel fisheries. The Han River ribbon worms have been identified as Yininemertespratensis (Sun & Lu, 1998) based on not only morphological characteristics compared with the holotype and paratype specimens, but also DNA sequence comparison with topotypes freshly collected near the Yangtze River mouth, China. Using sequences of six gene markers (18S rRNA, 28S rRNA, histone H3, histone H4, 16S rRNA, and COI), the phylogenetic position of Y.pratensis was inferred among other heteronemerteans based on their sequences obtained from public databases. This analysis firmly placed Y.pratensis as a close relative to Apatronemertesalbimaculosa Wilfert & Gibson, 1974, which has been reported from aquarium tanks containing tropical freshwater plants in various parts of the world as well as a wild environment in Panama.