Mercury in Feathers of Little Egret Egretta garzetta and Night Heron Nycticorax nycticorax Chicks and in Their Prey in the Axios Delta, Greece
01 Feb 1997-Archives of Environmental Contamination and Toxicology (Springer-Verlag)-Vol. 32, Iss: 2, pp 211-216
TL;DR: Night heron chick feathers, freshwater fish and dragonfly larvae could be used to monitor mercury contamination in this region, but use of bird feathers alone could give misleading results if changes in diet occurred.
Abstract: Mercury concentrations were measured in feathers of little egret and night heron chicks and in their prey in the Axios Delta, Greece. Significantly higher concentrations occurred in night heron than in little egret in 1993. In the night heron the mercury content of feathers was negatively correlated to the size of chicks, possibly due to inhibition of growth. Mercury concentrations were higher than reported for heron feathers in seriously polluted sites in North America and Japan, but the toxic hazard is unclear. Diets differed considerably between the two species due to use of different foraging habitats and this seems responsible for different mercury contents of feathers. Mercury concentrations in the pumpkinseed sunfish Lepomis gibbosus, goldfish Carrassius auratus, and in dragonfly Odonata larvae were the highest among the prey categories. Frogs and water beetles Dytiscidae had moderate concentrations whereas saltwater fish and terrestrial prey had very low mercury concentrations. The implication is that the deltaic marshes are the habitat most polluted with mercury. Night heron chick feathers, freshwater fish and dragonfly larvae could be used to monitor mercury contamination in this region, but use of bird feathers alone could give misleading results if changes in diet occurred.
Citations
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TL;DR: Results show that most of heavy metals detected in water and sediments are lower than that in Yangtze River Delta and Pearl River Delta, and the biomagnification of the selected nine heavy metals in the food webs is not significant.
Abstract: Nine heavy metals sampled from water, sediments, and aquatic organisms in the newly-formed wetlands of the Yellow River Delta (YRD) of China were analyzed to evaluate their concentrations and trophic transfer in food webs. The stable carbon (δ13C) and nitrogen (δ15N) isotopes were used to investigate trophic interactions. Results show that most of heavy metals detected in water and sediments are lower than that in Yangtze River Delta and Pearl River Delta. The longest food web is approximately 4 with the highest trophic level of birds. The difference of heavy metal concentrations between endangered Saunders's Gull and other three kinds of protected birds is not obvious. Cd, Zn, and Hg were identified to have an increase with the trophic level (TL), while As, Cr, Cu, Mn, Ni and Pb show an opposite trend, however, the biomagnification of the selected nine heavy metals in the food webs is not significant.
160 citations
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TL;DR: A Utility Index that ranks terrestrial vertebrate species as potential sentinels of contaminants in a region and a Vulnerability Index that assesses the threat of specific groups of contaminants to these species, have been developed to assist decision makers in risk assessments of persistent organic pollutants, cholinesterase-inhibiting pesticides, petroleum crude oil, mercury, and lead shot.
Abstract: It has long been recognized that biota can be good indicators of environmental health and pollution. From the ancient Greek maxim “a bad crow lays a bad egg” to the coal miners’ caged canary as a sentinel of noxious gas, the link between contaminants in the environment and their effect on its inhabitants has been acknowledged. However, as the severity of man’s impact on the environment worsened, it became clear that more sophisticated efforts were needed to systematically monitor the extent and effects of this input. In the modern era, widespread recognition of the effects of contaminants upon wildlife can be traced back to the beginning of the twentieth century, as oil spills resulting from the oceanic transport of large quantities of crude oil claimed the lives of seabirds and other marine species (Albers 1995). In the early 1950s, anthropogenic contaminants were first linked to population-level effects, as ingestion of spent lead shot from hunting was found to be a contributing factor in annual declines in North American waterfowl populations (Bellrose 1959; Sanderson and Bellrose 1986). Although isolated efforts to monitor lead shot ingestion in waterfowl began during this time, it was not until the realization of the devastating effects of DDT on avian reproduction (most notably the bald eagle, Haliaeetus leucocephalus) that large-scale monitoring efforts were undertaken by government natural resource management agencies.
92 citations
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TL;DR: Assessment of trace element contamination at three wetlands in Pakistan used as indicators the eggs and the feathers of colonial waterbirds, particularly Little Egrets, their prey, and the sediments collected within their foraging areas found feathers of predatory birds such as the egrets are the best indicators of environmental contamination.
Abstract: Environments in Pakistan are subject to increasing pollution, but previous studies were very scanty. During 1999 and 2000, we assessed trace element contamination at three wetlands, Karachi Harbour (with presumed industrial-urban pollution), Taunsa Barrage (agricultural pollution), and Haleji Lake (relatively unpolluted), using as indicators the eggs and the feathers of colonial waterbirds, particularly Little Egrets, their prey, and the sediments collected within their foraging areas. The concentrations of As, Cd, Cr, Pb, Hg, Mn, Se, and Zn were generally within the normal background level, and mostly below the threshold that may affect bird survival or reproduction. However, somewhat high concentrations were found in fish from Karachi, for Pb that was at levels that may harm fish reproduction, and for Hg that was at limit concentration for human consumption. Alarming concentrations were found for Cr and Se in sediments from Karachi, that were above the critical levels for contaminated soil, and Se in eggs, that may affect egret reproduction. The differences among the three wetlands were less marked than hypothesized. The egret species within the same area differed in the concentration of certain elements in their eggs, possibly because females may have foraged in different habitats before breeding, whereas no interspecies difference was found in chick feathers, presumably because their food had been collected in similar habitats around the colony. High bioaccumulation from sediments to organic samples occurred for Hg, while Cd, Se, and Zn exhibited low accumulation; for all these elements, feathers of predatory birds such as the egrets are the best indicators of environmental contamination. On the other hand, As and Cr did not bioaccumulate, and the sediments, or the organisms low in the food chain, like fish or crustaceans, are better indicators of their presence in the environment than predatory birds.
79 citations
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TL;DR: This review is a synthesis of pertinent literature on this topic, with specific reference to contaminant residues in various tissue types, relationship between body burden and reproductive success, and the use of biomarkers to predict more serious adverse affects.
Abstract: Predatory waterbirds, such as ardeids, are susceptible to bioaccumulation of pollutants through the ingestion of contaminated food sources. High body burdens of contaminants, including PCBs, PAHs, cadmium, mercury, lead, copper, zinc and arsenic have been detected in many bird species worldwide. There is a paucity of literature, however, linking contaminant body burden and effects on reproductive success in waterbirds. This review is a synthesis of pertinent literature on this topic, with specific reference to contaminant residues in various tissue types, relationship between body burden and reproductive success, and the use of biomarkers to predict more serious adverse affects. The impetus for this review was the development of a conservation strategy and management plan (commissioned by the Agriculture, Fisheries and Conservation Department of Hong Kong Special Administrative Region (SAR)) for an important wetland in Hong Kong that supports many threatened waterbirds, including ardeids.
65 citations
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TL;DR: A probabilistic risk assessment of the possible adverse effects of mercury on the breeding success of the Little Egret and the Black-crowned Night Heron was carried out, finding there was no evidence of adverse effects at other egretries, but there may possibly be adverse effects with lead but not cadmium.
Abstract: The feathers of two Ardeid species, the Little Egret (Egretta garzetta) and the Black-crowned Night Heron (Nycticorax nycticorax) were collected from six egretries and two egretries respectively, located in different areas in the New Territories of Hong Kong, including the Mai Po Marshes (within a Ramsar site). These feathers were digested and concentrations (µg/g dry weight) of copper (4.6–19.4), iron (8.1–641.3), manganese (0.4–19.4), zinc (51.3–183.5), lead (0.1–5.1), cadmium (0.01–0.15), chromium (0.06–1.7) and mercury (0.0–7.1) were determined by ICP-AES, ICP-MS and CVAAS. The levels of manganese, mercury and lead found were equal to or less than the concentrations found in previous investigations, reflecting a slight downward trend most apparent with lead. As a general rule, the levels of lead and mercury were higher in the egretries close to the polluted Deep Bay. A probabilistic risk assessment of the possible adverse effects on the breeding success of the Little Egret was carried out with respect to mercury, lead and cadmium. It was concluded that mercury (0.5–7.1 µg/g dry weight feathers) probably has had adverse effects at the Au Tau egretry of the Little Egrets, but there was no evidence of adverse effects at other egretries. The probabilistic analysis also indicated a low likelihood of adverse effects of mercury on the breeding of the Black-crowned Night Herons at A Chau (0.3–1.2 µg/g) and Mai Po Village (0.0–1.4 µg/g). The evidence for the effects of lead and cadmium was limited but suggested there may possibly be adverse effects with lead but not cadmium.
61 citations
References
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TL;DR: A review of the available information on global Hg cycling shows that the atmosphere and surface ocean are in rapid equilibrium; the evasion of Hg0 from the oceans is balanced by the total oceanic deposition of hg(II) from the atmosphere as mentioned in this paper.
Abstract: A review of the available information on global Hg cycling shows that the atmosphere and surface ocean are in rapid equilibrium; the evasion of Hg0 from the oceans is balanced by the total oceanic deposition of Hg(II) from the atmosphere. The mechanisms whereby reactive Hg species are reduced to volatile Hg0 in the oceans are poorly known, but reduction appears to be chiefly biological. The rapid equilibrium of the surface oceans and the atmosphere, coupled with the small Hg sedimentation in the oceans makes deposition on land the dominant sink for atmospheric Hg. About half of the anthropogenic emissions appear to enter the global atmospheric cycle while the other half is deposited locally, presumably due to the presence of reactive Hg in flue gases. We estimate that over the last century anthropogenic emissions have tripled the concentrations of Hg in the atmosphere and in the surface ocean. Thus, two-thirds of the present Hg fluxes (such are deposition on land and on the ocean) are directly or indirectly of anthropogenic origin. Elimination of the anthropogenic load in the ocean and atmosphere would take fifteen to twenty years after termination of all anthropogenic emissions.
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TL;DR: It is concluded that significant physiological and biochemical responses to such exposure conditions occur at dietary metal concentrations insufficient to cause signs of overt toxicity, particularly important are reproductive effects which include decreased egg production, decreased hatchability, and increased hatchling mortality.
Abstract: The toxicity of chronic dietary metal exposure in birds is reviewed. It is concluded that significant physiological and biochemical responses to such exposure conditions occur at dietary metal concentrations insufficient to cause signs of overt toxicity. Particularly important are reproductive effects which include decreased egg production, decreased hatchability, and increased hatchling mortality. Young, growing birds are typically more sensitive to the toxic effects of chronic metal exposure than adults, and altricial species are often more sensitive than precocial species. Factors which modify the absorption and toxicity of heavy metals, such as Se for the case of Hg, and Ca for the case of Pb and Cd, are discussed. Monitoring strategies for assessing environmental metal exposure in birds are evaluated.
747 citations
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01 Jan 1993
TL;DR: In this paper, birds are used as indicators of change in water quality and change in marine prey stocks in the tropics of the world, and as monitors of radionuclide contamination.
Abstract: Can birds be used to monitor the environment? Environmental change. Birds as monitors of radionuclide contamination. Birds as indicators of change in water quality. Birds as monitors of pollutants. Seabirds as indicators of change in marine prey stocks. Migrants as monitors of change in the tropics. An integrated approach to assessing environmental changes affecting birds. Synthesis and future prospects.
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