Utilization of black-tailed gull (Larus crassirostris) eggs for monitoring of mercury levels in coastal areas of South Korea: Preliminary study

The relationship between mercury and selenium in the eggshell and egg content of the Whiskered tern (Chlidonias hybridus)

Mercury and its compounds do not have beneficial biological roles in living organisms. In contrast, selenium, within permissible limits, is an essential micronutrient and antioxidant. There is an antagonistic relationship between mercury and selenium. Therefore, the molar ratio of selenium to mercury is used as an appropriate index. Measuring the mercury in the environment without considering the protective effects of selenium does not accurately reflect the risks posed by mercury. This study aimed to measure the mercury, selenium, and the molar ratio Se:Hg in the shell and content of the eggs of the Whiskered Tern (Chlidonias hybridus) in northern Iran. After the onset of egg laying, one egg was collected from each nest (38 eggs in total). The results showed that the concentration of mercury in the eggshell was higher, while the concentration of selenium and the molar ratio Se:Hg were higher in the egg content. A molar ratio Se:Hg in both the eggshell and the egg content indicates a positive effect of selenium in reducing the risks associated with mercury toxicity. The parameters of egg shape index, egg weight, and clutch size did not have a significant effect on the concentrations of mercury, selenium, and the molar ratio Se:Hg in the eggshell and egg content. There was a significant negative correlation between the concentration of mercury in the eggshell and the molar ratio Se:Hg in both the eggshell and egg content. The lack of a positive correlation between the concentrations of mercury or selenium in the eggshell and egg content suggests that the transferability of heavy metals from the egg to the embryo in the egg content cannot be confirmed.

Innovative approach for environmental pollution assessment using seabird eggs: mercury in black-tailed gull (Larus crassirostris) eggs from the Korean islands (2012-2021)

Since black-tailed gulls derive energy for egg production around their habitat, analyzing concentration of chemicals in the eggs reveals the local environmental pollution. This is, however, complex due to the diversity of seabird diets across multiple ecosystems. This study determined the influence of food source and trophic position (TP) on the mercury concentration ([Hg]) in eggs and subsequently mitigated these influences by adjusting through [Hg]-TP relationship, thereby enabling spatial and temporal comparisons among individuals. Following TP adjustment, the [Hg] that previously exhibited significant regional differences no longer displayed such a variation. Moreover, by normalizing to trophic level 4, as suggested by the European Union (EU), the total [Hg] was standardized from 1001 ± 415 ng g-1 to 1347 ± 516 ng g-1 in all the egg samples, far exceeding the EU criteria. These two approaches provide valuable insights for the effective monitoring of marine pollution and past environmental reconstruction by adjusting/normalizing [Hg] in seabird eggs.

Integrated approach for the isotope trophic position of black-tailed gull (Larus crassirostris) eggs over a decade: Combining stable isotopes of amino acids and fatty acids composition

Recently, compound-specific isotope analysis (CSIA) using the amino acid nitrogen stable isotope ratio (δ15NAAs) has been widely used for accurate estimation of trophic position (TP). In addition, a quantitative fatty acid signature analysis (QFASA) offers insights into diet sources. In this study, we used these techniques to estimate the TP for seabirds that rely on diverse food sources across multiple ecosystems. This allows for the proper combination of factors used in TP calculation which are different for each ecosystem. The approach involved the application of a multi-mixing trophic discrimination factor (TDF) and mixing β which is a Δδ15N between trophic and source amino acid of primary producer. Since the black-tailed gulls (BTGs) are income-breeding seabirds, which rely on energy sources obtained around their breeding sites, they and their eggs could be useful bioindicators for environmental monitoring. However, the ecological properties of BTGs such as habitats, diets, and TP are not well known due to their large migration range for wintering or breeding and their feeding habits on both aquatic and terrestrial prey. In this study, the eggs were used for estimating TP and for predicting TP of mother birds to overcome difficulties such as capturing birds and collecting non-invasive tissue samples. Eggs, sampled over a decade from three Korean islands, showed spatial differences in diet origin. Considering both the food chain and physiology of BTG, the TP of eggs was estimated to be 3.3-4.0. Notably, the TP was significantly higher at site H (3.8 ± 0.1) than at site B (3.5 ± 0.2), which indicated a higher contribution of marine diet as confirmed by QFASA. Using a reproductive shift of δ15NAAs, the TP of the mother birds was predicted to be 3.6-4.3, positioning them as the top predator in the food web. The advanced integration of multiple approaches provides valuable insights into bird ecology.

Quantitative analysis and contamination profiles of PCBs, OCPs, and PAHs in black-tailed gull eggs in the Republic of Korea

The simultaneous determination of 8 polychlorinated biphenyls (PCBs), 23 organic chlorine pesticides (OCPs), and 35 polycyclic aromatic hydrocarbons (PAHs) in black-tailed gull eggs was described using ultrasound-assisted extraction and gas chromatography-tandem mass spectrometry (GC-MS/MS). The ranges of the lower limits of detection for PCBs, OCPs, and PAHs were 0.006-0.029, 0.01-0.10, and 0.01-0.20 μg kg^-1, respectively. The intraday precision was in the range of 0.650-12.9% and the intraday accuracy was in the range of 86.6-113%. When the proposed method was used to analyze the target compounds in gull eggs collected from six sites in the Republic of Korea, the analytical results demonstrated concentration ranges of 113.32-394.07 µg kg^-1 for total PCBs, 422.92-1082.09 µg kg^-1 for total OCPs, and 134.50-231.27 µg kg^-1 for total PAHs in the samples. The PCA results for PAHs and OCPs were well differentiated by sampling site, whereas those for PCBs differed little by sampling site. There were more pyrogenic PAHs in the West Sea and the South Sea with many industrial areas than in the East Sea with few industrial areas. Differences in the OCP patterns of samples from the West Sea close to China were considered to be related to the use of DDT in China until recently. PCBs were accumulated in the samples regardless of region, so there was no significant difference in the PCB patterns between the samples obtained from the three Seas.

Temporal and spatial trends of chlorinated paraffins and organophosphate flame retardants in black-tailed gull (Larus crassirostris) eggs

In this study, eggs of black-tailed gull (Larus crassirostris), a top trophic level predator of marine ecosystem were, for the first time, monitored to assess the temporal and spatial trends of emerging pollutants in South Korea. Two Island regions, namely, Baekryeong-do (Site A) and Hong-do (Site B) were investigated from 2012 to 2018, and the total levels of short chain chlorinated paraffins (SCCPs), medium chain CPs (MCCPs), and organophosphate flame retardants (OPFRs) for both Site A and B were 1180-2931 and 694-2023 ng/g lipid weight (lw), 1287-4898 and 1034-3075 ng/g lw, and 203-499 and 233-409 ng/g lw, respectively. The time-trends of the concentration of pollutants showed an increasing tendency from 2012 to 2018, with the levels predicted to be doubled within three years, following the results of regression analysis. A shift in temporal-trends from shorter to longer chain CPs was noted, suggesting the effect of industrial-related contamination. Especially, significantly high levels of CPs and OPFRs were found in the site adjacent to China, which is reasonable as China is the largest producer and consumer of FRs and plasticizers worldwide. This study is valuable to understand the temporal increment of emerging pollutants as the alternatives of phased-out FRs and plasticizers, while raising the need for continuous environmental management.

Ecosystem services and impact of industrial pollution on urban health: evidence from Durgapur, West Bengal, India

Industrialization, urbanization, and rapid socioeconomic growth are the prime factors regarding development of an urban city. These activities deteriorate the environment slowly by increasing harmful pollutants and the impact of which will be observed in near future in terms of several natural calamities, disease, and ecological consequences. Various urban ecosystems like urban forestry, wetland, grassland, parks/gardens etc. are the main criteria of urban health in respect to delivering multiple of benefits to the surrounding biota. But these regulatory systems have been affected severely through different industrial pollution stresses resulting into deterioration of their physicochemical quality and biotic diversity. The study revealed that the annual average air pollution index (API) exceeded the higher threshold value (i.e. >100) during the study period and recognized Durgapur as the severely polluted region in West Bengal, India. The characteristics of major air pollutants like SO₂, NOx, and suspended particulate matter (SPM) and their temporal trends have been evaluated. The objective of this study was to detect the effect of industrial pollution on the aforesaid urban ecosystems in terms of variable ecological services such as purification of polluted air, atmospheric regulation, reduction of noise, proper drainage of rainwater, and sewage treatment. The outcome of this review work was to evaluate thoroughly the physiological, biochemical, and morphological symptoms of plant species under air pollution stress. On the other hand, the effect of air pollution on human and animal populations regarding various diseases (like bronchitis, cardiopulmonary arrest, cancer, liver and kidney dysfunction) has also been discussed.

Non-invasive biomonitoring of mercury in birds near thermal power plants: lessons from Maharashtra, India

Thermal power plants (TPPs) have emerged as a major source of air, water, and soil pollution because of the presence of many toxic metals. The presence of mercury (Hg) in fly ash has proven to be toxic in nature because of its tendency to get bioaccumulated and biomagnified in the food chain. The aim of the present study was to understand the presence of toxic Hg in the feathers of wetland birds undertaking the study around a TPP located in Nagpur, India. Local wetland birds especially cattle egrets, heron, and Moorhen were commonly observed dwelling close to fly ash ponds for various purposes (roosting, breeding, feeding, etc.). Samples of fly ash, soil, water, plants, and bird feather were collected, cleaned, and processed for Hg analysis. A mercury analyzer was used to assess the concentration of toxic levels of Hg in samples. Our results reflect leaching of Hg in soil and uptake by plant samples, whereas in water, ash, and bird feather samples concentrations of Hg were fairly below the prescribed limits (World Health Organization). A non-invasive method for understanding the mercury concentration in wetland birds has been established as a potential important monitoring tool to track the fate of toxic metal Hg in the food chain. In summary, our results indicate fairly low Hg levels in feather samples projecting non-invasive biomonitoring as a promising strategy. The study also suggests that a comprehensive monitoring action plan in place for Hg and other toxic metals in the food chain that comes from TPP will be efficient to avoid any pitfalls. Graphical abstract.