First evaluation of legacy persistent organic pollutant contamination status of stranded Yangtze finless porpoises along the Yangtze River Basin, China

Spatial distribution, trophic magnification, and risk assessment of per- and polyfluoroalkyl substances in Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis): Risks of emerging alternatives

The Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) is the only freshwater cetacean found in China. However, per- and polyfluoroalkyl substances (PFASs) risks in YFPs remain unclear. In this study, legacy PFASs, their precursors and alternatives, were determined in YFP muscles (n = 32), liver (n = 29), kidney (n = 24), skin (n = 5), and blubbers (n = 25) collected from Poyang Lake (PL) and Yangtze River (YR) between 2017 and 2023. Perfluorooctane sulfonic acid (PFOS) was the predominant PFAS in all YFP tissues, with a median hepatic concentration of 1700 ng/g wet weight, which is higher than that in other finless porpoises worldwide. PFOS, chlorinated polyfluorinated ether sulfonates (Cl-PFESAs), and perfluoroalkane sulfonamides concentrations in YFP livers from PL were significantly higher than those from YR (p < 0.05); however, the opposite was observed for hexafluoropropylene oxide acids. Biomagnification and trophic magnification factors (BMF and TMF, respectively) of most PFASs in the YFP food web were > 1. Perfluoroheptane sulfonic acid had the highest BMF value (99), followed by 6:2 Cl-PFESA (94) and PFOS (81). The TMFmuscle and TMFliver values of the total PFASs were 3.4 and 6.6, respectively, and were significantly positively correlated with the fluorinated carbon chain length (p < 0.01). In addition, up to 62 % of the hazard quotients for 6:2 Cl-PFESA were > 1, which was higher than that of PFOS (48 %), suggesting a high hepatotoxicity of 6:2 Cl-PFESA to YFPs. Bioaccumulation and biotoxicity of legacy and emerging alternatives in aquatic organisms continue to be a concern, especially for underscoring the vulnerability of the long-lived and endangered species.

Concentration of polychlorinated biphenyls and risk assessment in finless porpoises from the East China Sea

Polychlorinated biphenyls (PCBs) are bioaccumulative persistent organic pollutants with a great impact on cetaceans. To examine the content of PCBs and their risks to finless porpoises, this study determined the concentrations of seven typical PCB congeners in 56 tissue samples of East Asian finless porpoises (EAFPs) sampled in 2009-2012 from Ningbo (29.8835° N, 122.0644° E), Pingtan (25.5133° N, 119.8172° E) and Lvsi (32.1035° N, 121.6078° E). PCB138, PCB153 and PCB101 were the predominant congeners, accounting for 31.15%, 18.59% and 15.75%, respectively, of all PCBs detected. The content of PCBs increased with age in males but decreased from juveniles to adults in females due to transfer to calves by reproduction and lactation. EAFPs in Ningbo and Pingtan accumulated more PCBs than those in Lvsi Port. The trophic positions of EAFPs from Lvsi, Pingtan and Ningbo were 9.41, 8.95 and 9.43, respectively. PCB concentrations did not accumulate significantly with increasing trophic levels. The risk quotient index indicated that the risk of trichlorobiphenyl (3-PCB), tetrachlorobiphenyl (4-PCB), pentachlorobiphenyls (5-PCB), and hexachlorobiphenyls (6-PCB) to EAFPs in the East China Sea was generally low and within safe limits thus far.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-023-00221-0.

Fatty acids and organohalogen contaminants in seafood from the Pearl River Estuary, China: Risk-benefit analyses of seafood consumption

Seafood has long been considered a healthy food choice, but it is also an exposure source of contaminants that may bring potential health risks to humans. Here, 80 organohalogen contaminants (OHCs) and 36 fatty acids (FAs) were analyzed in 22 (n = 211) and 19 fishery species (n = 176) from the eastern- and western Pearl River Estuary (PRE), respectively, for risk-benefit analysis. The average concentrations of total FAs in seafood from the eastern- and western PRE were 26.0 ± 2.14 and 21.3 ± 1.66 mg g-1 wet weight, respectively. Seafood from the eastern PRE exhibited higher levels of OHCs than those from the western PRE, highlighting the spatial heterogeneity of OHC contamination within the PRE. Species occupying higher trophic levels (TLs) typically demonstrated higher levels of OHC accumulation, indicating the biomagnification potential of these contaminants in the PRE ecosystem. Significant negative correlations were observed between TLs and the proportions of monounsaturated fatty acids and polyunsaturated fatty acids, presumably attributed to the ability of fish to synthesize these FAs decreases with increasing TLs. Our benefit-risk quotient (BRQ) analyses revealed that, as far as OHCs are concerned, all seafood species had a BRQ∑OHCs value <1, except for one-spot snapper and daggertooth pike conger, which had BRQ values of 1.03 and 1.14, respectively. The findings indicate that most marine species here analyzed may not pose significant health risks to consumers as a result of OHC exposure. However, considering that many other pollutants and nutrients are not analyzed here, the results of our risk assessments should be treated as preliminary, not final. Future data collection is essential to enhance the comprehensiveness of this type of analysis.

Legacy persistent organic pollutants (POPs) in eggs of night herons and poultries from the upper Yangtze Basin, Southwest China

Black-crowned night heron (Nycticorax nycticorax) eggs have been identified as useful indicators for biomonitoring the environmental pollution in China. In this study, we investigated thirty eggs of black-crowned night heron collected from the upper Yangtze River (Changjiang) Basin, Southwest China, for the occurrence of legacy persistent organic pollutants (POPs), including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Our results showed a general presence of POPs in night heron eggs with OCPs being the dominant contaminants, having a geometric mean concentration of 22.2 ng g-1 wet weight (ww), followed by PCBs (1.36 ng g-1 ww), PBDEs (0.215 ng g-1 ww), and PCDD/Fs (23.0 pg g-1 ww). The concentration levels were found to be significantly higher in night heron eggs than in poultry eggs by one or two magnitude orders. Among OCP congeners, p,p'-DDE was found to be predominant in night heron eggs, with a geometric mean concentration of 15.1 ng g-1 ww. Furthermore, species-specific congener patterns in eggs suggested similar or different sources for different POPs, possibly associated with contaminated soil and parental dietary sources. Additionally, estimated daily intakes (EDIs) were used to evaluate non-carcinogenic and carcinogenic risk associated with consumption of bird eggs. Our results revealed non-negligible non-cancer and cancer risk for humans who consume wild bird eggs as a regular diet instead of poultry eggs.

Long-Term Monitoring of Polybrominated Diphenyl Ethers (PBDEs) in Indo-Pacific Humpback Dolphins (Sousa chinensis) from the Pearl River Estuary Reveals High Risks for Calves due to Maternal Exposure

Although many studies have documented the wide occurrence of polybrominated diphenyl ethers (PBDEs) in cetaceans, little evidence exists regarding the detrimental effects of PBDE exposure on calf death rates for free-ranging cetaceans. This study analyzed life-history-associated PBDE bioaccumulation patterns in 128 stranding Indo-Pacific humpback dolphin (Sousa chinensis) samples over an 18-year timespan from the Pearl River Estuary (PRE). In comparison to the records of PBDE levels in cetaceans worldwide, the median levels of PBDEs (median = 10600 ng g^-1 lw, range = 721-50900 ng g^-1 lw) in all samples were the highest to date. One-way analysis of variance (ANOVA) showed that adult males (median = 16100 ng g^-1 lw, range = 4070-50900 ng g^-1 lw) and calves (12000 ng g^-1 lw, range = 1250-35300 ng g^-1 lw) both had the highest levels of PBDEs compared to the rest of the age/sex groups (p < 0.05). Concentrations of PBDEs in noncalves significantly decreased over the studied period, while those in calves had a slightly increasing trend, which may be due to different exposure routes via fish or milk, respectively. A significant and positive relationship was found between annual calf stranding death rates and body-length-adjusted PBDE concentrations in calves (r = 0.62, p < 0.05), suggesting that maternal exposure of calves to elevated levels of PBDEs may have contributed to the high annual stranding death rates of calves in the last two decades.

Blood Transcriptome Analysis Reveals Gene Expression Differences between Yangtze Finless Porpoises from Two Habitats: Natural and Ex Situ Protected Waters

The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis, YFP) is a critically endangered small odontocete species, mainly distributed in the middle and lower reaches of the Yangtze River, Poyang Lake, and Dongting Lake. Under the influence of human activities, many factors are threatening the survival and reproduction of YFPs in their natural habitat. Ex situ conservation is of great significance to strengthen the rescuing conservation of YFPs by providing suitable alternative habitats and promoting the reproduction and growth of the ex situ population. To reveal the differences in gene expression of YFPs in natural and ex situ protected waters, and to investigate the effects of environmental factors on YFPs and their mechanisms, we performed transcriptome sequencing for blood tissues of YFPs collected from natural waters and ex situ protected waters. Using RNA-seq we identified 4613 differentially expressed genes (DEGs), of which 4485 were up-regulated and 128 were down-regulated in the natural population. GO analysis showed that DEGs were significantly enriched in entries related to binding, catalytic activity, and biological regulation; KEGG analysis showed that DEGs were enriched mainly in signal transduction, endocrine system, immune system, and sensory system-related pathways. Further analysis revealed that water pollution in natural waters may affect the hormone secretion of YFPs by altering the expression pattern of endocrine genes, thus interfering with normal endocrine activities; noise pollution may induce oxidative stress and inflammatory responses in YFPs, thus impairing the auditory function of YFPs. This study provides a new perspective for further research on the effect of habitat conditions on the YFPs and suggests that improving the habitat environment may help in the conservation of YFPs.

Comparative Analysis of Blood Transcriptome in the Yangtze Finless Porpoise (Neophocaena asiaeorientalis)

The Yangtze finless porpoise (Neophocaena asiaeorientalis) is the sole freshwater subspecies of Neophocaenaphocaenoides, and there is a lack of data on its transcriptome. In this study, we applied RNA-seq technology to assemble, de novo, a transcriptome and analyzed differential expressed genes (DEGs). About 6 Gb of clean data was generated for the Yangtze finless porpoise blood (n = 6) through de novo sequencing. In total, 151,211 unigenes were generated and a total of 119,039 of these unigenes (78.72%) were functionally annotated when searched for within the NCBI Nr, SwissProt, GO, COG, and KEGG databases. Diverse and extensive expressed gene catalogs were sampled for the Yangtze finless porpoise. DESeq2 was used to analyze the differential expression genes (DEGs) obtained from the assembled transcriptome. The results indicated that DEGs have close relationships with the Yangtze finless porpoise’s development, evolution and adaptation. Further, we found that genes involved in cetacean TAG synthesis might directly explain the molecular basis of cetacean blubber thickening. These transcriptome data will assist in understanding molecular mechanisms of Yangtze finless porpoise adaptation.