From wetlands to landfills: white stork (Ciconia ciconia L., 1758) as a reliable bioindicator of ecosystem health

White storks (Ciconia ciconia L., 1758) and their nestlings have emerged as valuable bioindicators of environmental pollution, particularly in ecosystems affected by human activities. This review explores the role of white storks in biomonitoring, focusing on the use of biomarkers and pollutant analysis to understand the physiological consequences of environmental stressors. Key biomarkers, such as oxidative stress markers, immune responses, and hormonal alterations provide insight into the effects of pollutants like heavy metals, pesticides, and other toxic compounds. The biomarkers are typically measured in matrices such as blood, feathers, eggs, and tissues, each offering unique advantages in assessing pollutant exposure. However, ethical concerns regarding wildlife monitoring and the potential harm caused by invasive sampling techniques call for non-invasive methods. Future research should explore novel non-invasive techniques and employ long-term monitoring programmes to understand the cumulative effects of pollution. Despite challenges such as biological variability and environmental factors, white storks remain reliable indicators of ecological change and pollutant burden, providing critical data that can guide pollution management policies, inform conservation strategies, and protect both wildlife and human health from current environmental threats.

Heavy metal(loid) effect on multi-biomarker responses in apex predator: Novel assays in the monitoring of white stork nestlings

The goal of the present study was to investigate differences in biomarker responses related to metal(loid)s in white stork (Ciconia ciconia) nestling's blood from continental Croatia. To achieve this, a battery of biomarkers that can be affected by environmental pollutants, including metal(loid)s, was assessed (esterase activity, fluorescence-based oxidative stress biomarkers, metallothionein levels, glutathione-dependent enzyme activity). The research was conducted during the white stork breeding season in diverse areas (a landfill, industrial and agricultural sites, and an unpolluted area). White storks' nestlings near the landfill exhibited reduced carboxylesterase (CES) activity, elevated glutathione (GSH) concentration, as well as high Pb content in the blood. Increased As and Hg concentrations in blood were attributable to environmental contamination in agricultural area and an assumed unpolluted area, respectively. Furthermore, agricultural practices appeared to affect CES activity, as well as elevate Se levels. In addition to the successful implementation of biomarkers, present research showed that agricultural areas and a landfill are areas with increased metal(loid) levels possibly causing adverse effects on the white storks. This first-time heavy metal and metalloid analyses in the white stork nestlings from Croatia point to the necessary monitoring and future assessments of pollution impact to prevent irreversible adverse effects.

Blood biomarkers in white stork (Ciconia ciconia) nestlings show different responses in several areas of Croatia

White stork nestlings can provide quantitative data on the quality of the environment, as they are dependent on their parents that provide locally foraged food. Blood was sampled from the brachial vein (n = 109) and the sampling was performed in parallel with ringing during breeding season 2020 from five areas in eastern Croatia: Lonjsko polje, Jelas polje, Slavonski Brod-east, Podunavlje, and Donje Podravlje. In the present study, for the first time in Croatia, the following enzymatic biomarkers were assessed in white stork nestlings: activities of acetylcholinesterase (AChE), carboxylesterase (CES), glutathione S-transferase (GST), and glutathione reductase (GR), as well as nonenzymatic biomarkers: levels of glutathione (GSH) and reactive oxygen species (ROS). All endpoints were measured in two blood fractions: plasma and a postmitochondrial fraction (S9). Nestlings from Podunavlje and Donje Podravlje, areas known for intensive agriculture, showed lower AChE and CES activity when compared to the other investigated areas, indicating the presence of inhibitory xenobiotics. Higher oxidative stress was observed in Slavonski Brod-east, an area surrounded by metal and engineering industry, and Podunavlje compared to the other sampling areas. Hence, this study shows the impact of pollutants from the surrounding metal, petroleum, and agricultural industry might have on the biomarkers in white stork nestlings, which are often seen as early-warning signals.

Effects of Cu, Zn and their mixtures on bioaccumulation and antioxidant enzyme activities in Galleria mellonella L. (Lepidoptera: Pyralidae)

The effects of Cu, Zn and their mixture on bioaccumulation and antioxidant enzyme activities of midgut and fat body of Galleria mellonella larvae were investigated. Exposure to mixtures of both metals showed a synergistic effect and the accumulation levels were increased in both tissues. When the metals were exposed separately the concentration of Zn increased in both tissues, whereas the concentration of Cu increased in midgut and decreased in fat body. Also, it was determined that, oxidative stress occurred in the midgut and fat body when G. mellonella larvae were fed singly and in a mixture with different concentrations of Cu and Zn. In addition, significant changes were observed in antioxidant and detoxification enzyme activities, which are an indicator of oxidative stress. Larvae of G. mellonella showed immune responses similar to vertebrates, and could be used as bioindicator species due to being grown easily in the laboratory and reduced research costs Understanding the detoxification mechanism in insects is an important parameter for future ecotoxicological studies on the genotoxic, cytotoxic and physiological effects that different environmental pollutants such as heavy metals can cause.

Habitat-, age-, and sex-related alterations in oxidative stress biomarkers in the blood of mute swans (Cygnus olor) inhabiting pomeranian coastal areas (Northern Poland)

The mute swan (Cygnus olor) can be considered a representative species of birds associated with the aquatic environment and responding very clearly to changes in the environment. Assuming that the condition of the mute swan population well reflects the state of the environment, this species was used in our research as a bioindicative species. Thus, the aim of our study was to elucidate the association between metal contents in soil samples collected from a habitat of mute swans and element contents in their feathers as well as the levels of biomarkers of lipid peroxidation, oxidatively modified proteins, and total antioxidant capacity in the blood of mute swans living in three agglomerations in coastal areas in the southern part of the Baltic Sea (Pomeranian region, northern Poland). We compared the effects of inhabitation, age, and sex on the ecophysiological accumulation of metals in three wintering populations of the mute swan from coastal areas of northern Poland, i.e., Słupsk, Gdynia, and Sopot. In Słupsk, the anthropogenic pressure was related predominantly to the level of Al and, to a lesser extent, to the content of Rh and Ru. We found maximum levels of lipid peroxidation biomarkers in the blood of the mute swans from Gdynia (38.20 ± 6.35 nmol MDA·mL^-1). At the same time, maximum levels of aldehydic and ketonic derivatives of oxidatively modified proteins were noted in the blood of swans from Sopot compared to the values obtained in mute swans from Słupsk and Gdynia. This trend suggesting high levels of oxidative stress biomarkers was also confirmed by a decrease in the total antioxidant capacity in these groups.

Eusociality is linked to caste-specific differences in metabolism, immune system, and somatic maintenance-related processes in an ant species

The social organization of many primate, bird and rodent species and the role of individuals within that organization are associated with specific individual physiological traits. However, this association is perhaps most pronounced in eusocial insects (e.g., termites, ants). In such species, genetically close individuals show significant differences in behavior, physiology, and life expectancy. Studies addressing the metabolic changes according to the social role are still lacking. We aimed at understanding how sociality could influence essential molecular processes in a eusocial insect, the black garden ant (Lasius niger) where queens can live up to ten times longer than workers. Using mass spectrometry-based analysis, we explored the whole metabolome of queens, nest-workers and foraging workers. A former proteomics study done in the same species allowed us to compare the findings of both approaches. Confirming the former results at the proteome level, we showed that queens had fewer metabolites related to immunity. Contrary to our predictions, we did not find any metabolite linked to reproduction in queens. Among the workers, foragers had a metabolic signature reflecting a more stressful environment and a more highly stimulated immune system. We also found that nest-workers had more digestion-related metabolites. Hence, we showed that specific metabolic signatures match specific social roles. Besides, we identified metabolites differently expressed among behavioral castes and involved in nutrient sensing and longevity pathways (e.g., sirtuins, FOXO). The links between such molecular pathways and aging being found in an increasing number of taxa, our results confirm and strengthen their potential universality.

Application of Non-Destructive Methods: Biomarker Assays in Blood of White Stork (Ciconia ciconia) Nestlings

White stork (Ciconia ciconia) nestlings can provide quantitative information on the quality of the surrounding environment by indicating the presence of pollutants, as they depend on locally foraged food. This study represents the first comparison of biomarkers in two fractions of white stork nestling blood: plasma and S9 (the post-mitochondrial fraction). The aim of this study was to evaluate acetylcholinesterase (AChE), carboxylesterase (CES), glutathione S-transferase (GST), and glutathione reductase (GR), as well as to establish a novel fluorescence-based method for glutathione (GSH) and reactive oxygen species (ROS) detection in plasma and S9. Considering the enzymatic biomarkers, lower variability in plasma was detected only for AChE, as CES, GST, and GR had lower variability in S9. Enzyme activity was higher in plasma for AChE, CES, and GST, while GR had higher activity in S9. Regarding the fluorescence-based method, lower variability was detected in plasma for GSH and ROS, although higher GSH detection was reported in S9, and higher ROS was detected in plasma. The present study indicated valuable differences by successfully establishing protocols for biomarker measurement in plasma and S9 based on variability, enzyme activity, and fluorescence. For a better understanding of the environmental effects on nestlings' physiological condition, biomarkers can be measured in plasma and S9.

A multidisciplinary approach to the evaluation of the effects of foraging on landfills on white stork nestlings

The use of landfills as foraging areas by white storks (Ciconia ciconia) is a recent well-known behaviour. While several studies have highlighted positive effects at a populational level others suggest that the presence of pollutants, pathogens and the lower presence of antioxidants in the food could pose a health risk for individuals. The objective of this study was to evaluate potential effects of the use of landfills as a food resource on the physiology and health of white stork nestlings, by a multidisciplinary approach based on the analysis of nutritional status, body condition, blood parameters, oxidative stress balance and the presence of pathogens. Results showed better body condition in individuals associated with landfills compared to the ones feeding on natural resources, as well as better nutritional status, as indicated by higher levels of albumin, cholesterol, and triglycerides in plasma. As many pollutants have a pro-oxidant effect, we evaluated oxidative stress balance, with no differences in the indicators of damage except for methaemoglobin (metHb), significantly higher in nestlings associated with landfill-origin food. Regarding antioxidants, GSH was higher in nestlings associated with landfills, which may suggest a hormetic response induced potentially by the presence of pollutants in waste. Nestlings fed food from landfills also had a higher presence of Escherichia coli with a multiresistant phenotype to antibiotics. In conclusion, our results show that nestlings fed with a higher proportion of food from landfills present a better nutritional status and body condition than those fed with a higher proportion of natural diet, being the only indicators of negative effects of the use of this food resource the higher percentage of metHb in the peripheral blood and the presence of antibiotic-resistant E. coli.

Assay optimisation and age-related baseline variation in biochemical markers in Lesser Black-backed gulls

Free-ranging animals are often used as bioindicators of both short- and long-term changes in ecosystem health, mainly to detect the presence and effects of contaminants. Birds, and gulls in particular, have been used as bioindicators over a broad range of marine and terrestrial ecosystems. In this study, we standardise the conditions for the use of a suite of biochemical markers in non-destructive matrices of Lesser Black-backed Gull (Larus fuscus) to facilitate future biomonitoring of marine and terrestrial contaminants. We characterized cholinesterase (ChE) in plasma and optimized assay conditions for ChE activity as a marker of neurotoxic damage. Moreover, we quantified variation in activity of ChE, lactate dehydrogenase (LDH), glutathione-S-transferase (GST) and catalase (CAT) as well as variation ranges of lipid peroxidation (LPO), in free-ranging adults and captive chicks. The main ChE form present in plasma of both adults and chicks was butyrylcholinesterase (BChE) followed by acetylcholinesterase (AChE), whose relative proportion in plasma tended to decrease with increased chick age. LPO levels and GST activity in blood cells (BCs) decreased significantly with increasing chick age, while BChE and LDH activity in plasma were not age-dependent. CAT in BCs tended to decline non-significantly in older chicks. Results of this study underscore the importance of standardising assay conditions and assessing intrinsic baseline variation in biochemical markers, before biochemical quantification. Data presented here provide a foundation for future use of BChE and LDH activity in plasma, as well as oxidative stress markers (LPO, CAT and GST) in BCs, to monitor environmental stress effects in Lesser Black-backed gulls.

Evaluation of acute and sublethal effects of chloroquine (C18H26CIN3) on certain enzymological and histopathological biomarker responses of a freshwater fish Cyprinus carpio

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Chloroquine (CQ) toxicity on fresh water fingerlings Cyprinus carpio was studied.

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Median lethal concentration (96 h) was noted.

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Acute (96 h) and sub-lethal (35 days) treatments was performed.

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Enzymological activity and histological alteration was analysed.

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Drug CQ has a toxic effect on non-target organism.

In this study the toxicity of antimalarial drug chloroquine (CQ) on certain enzymological (GOT, GPT and LDH) and histopathological alterations (Gill, liver and kidney) of a freshwater fish Cyprinus carpio was studied after acute (96 h) and sublethal (35 days) exposure. The median lethal concentration (96 h) of CQ was 31.62 mg/ml. During acute treatment (CQ at 31.62 mg/ml) the treated fish groups showed a significant increase in GOT and GPT activities in blood plasma; whereas LDH activity was decreased when compare to control groups. To analyse the effects of drug at the lowest concentration, the fish were exposed to 3.16 mg/ml (1/10th of 96 h LC50 value) for 96 h. In sublethal treatment (3.16 mg/ml) GOT activity increased up to 14th day and decreased during the rest of the exposure period (21, 28 and 35th day). A biphasic response in GPT activity was observed. LDH activity was found to be increased throughout the study period (35 days) compare to control groups. The alterations in enzyme activities in blood plasma were found to be significant at p < 0.05 (DMRT). Many histopathological changes in vital organs such as gill, liver and kidney of fish were observed in CQ treated group (acute and sub-lethal) compare to normal group. The alterations in the enzymological and histopathological study in the present investigation indicate that the drug CQ has toxic effects on non-target organisms. We conclude that the alterations in enzymological parameters and histopathological changes can be used as biomarker to assess the health of the aquatic organism/environment. Further data on molecular studies are needed to define the mode of action and toxicity of these emerging pollutants.

Concentration of 12 Metals and Metalloids in the Blood of White Stork (Ciconia ciconia): Basal Values and Influence of Age and Gender

The white stork (Ciconia ciconia) is being increasingly used in biomonitoring programmes of environmental contaminants due to its growing population in Europe; however, studies on inorganic elements are scarce. The blood of 70 white storks was collected and analysed by inductively coupled plasma mass spectroscopy (ICP-MS) to determine the presence of the following elements: lead (Pb), mercury (Hg), arsenic (As), nickel (Ni), iron (Fe), zinc (Zn), copper (Cu), selenium (Se), manganese (Mn), chromium (Cr), cobalt (Co), and cadmium (Cd). Our main goals were to determine the mean concentrations of these elements in the blood and to study its association with age and gender. Mean concentrations were highest for Fe, followed by Zn, and lowest for Co and Cd. The metal levels were similar to the values referred in the literature for the same species from different locations. No statistically significant differences were found between males and females. Regarding age, statistically significant differences were observed for Ni, Cu, Se, Hg, and Pb between young and adult animals (except for Pb, values in adults were higher than in fledglings). Many element concentrations were correlated, with the strongest correlations between the pairs Hg-Se, Hg-As, and Fe-Zn, mainly in adults. This study provides the baseline data for a monitoring program based on white stork blood as a nondestructive sample.

Detection and drivers of exposure and effects of pharmaceuticals in higher vertebrates

Pharmaceuticals are highly bioactive compounds now known to be widespread environmental contaminants. However, research regarding exposure and possible effects in non-target higher vertebrate wildlife remains scarce. The fate and behaviour of most pharmaceuticals entering our environment via numerous pathways remain poorly characterized, and hence our conception and understanding of the risks posed to wild animals is equally constrained. The recent decimation of Asian vulture populations owing to a pharmaceutical (diclofenac) offers a notable example, because the exposure route (livestock carcasses) and the acute toxicity observed were completely unexpected. This case not only highlights the need for further research, but also the wider requirement for more considered and comprehensive 'ecopharmacovigilance'. We discuss known and potential high risk sources and pathways in terrestrial and freshwater ecosystems where pharmaceutical exposure in higher vertebrate wildlife, principally birds and mammals, may occur. We examine whether approaches taken within existing surveillance schemes (that commonly target established classes of persistent or bioaccumulative contaminants) and the risk assessment approaches currently used for pesticides are relevant to pharmaceuticals, and we highlight where new approaches may be required to assess pharmaceutical-related risk.

Breeding near a landfill may influence blood metals (Cd, Pb, Hg, Fe, Zn) and metalloids (Se, As) in white stork (Ciconia ciconia) nestlings

Cadmium, lead, mercury, selenium, iron, zinc and arsenic levels were measured in blood samples from 59 free-ranging white stork nestlings from colonies located in three different environmental conditions in Western Spain. The reference colony was situated in "Llanos de Cáceres y Sierra de Fuentes", an Area of Special Interest for Bird Protection. A second colony was located close to (4.9 km) an urban landfill and a third one was close to both an intensive agricultural area and an urban landfill (1.5 km). Blood samples were diluted and elemental analysis was performed using inductively coupled plasma mass spectrometer. In all cases, the essential metals zinc and iron were found at the highest mean concentrations followed by lead > selenium > mercury > arsenic > cadmium. Regarding toxic metals, the highest concentrations were found for lead (ranging from 23.27 to 146.4 µg/L) although in all cases the concentrations were lower than those considered to cause subclinical effects. The metals levels detected in the chick's blood were not related to the previously reported levels in the soil next to the colonies, which may indicate that landfills are the main source of metals in white stork nestlings. The present data showed that metal levels in white stork chicks may be influenced by the use of landfills as feeding areas by the parents. However, more studies on the metal content in the feed of white stork and the influence of the distance to the landfill are necessary to establish the causality of these findings.