Pattern of mercury accumulation in different tissues of migratory and resident birds: Western reef heron (Egretta gularis) and Siberian gull (Larus heuglini) in Hara International Wetland—Persian Gulf

Abstract

The Hara Mangrove Forest of the Persian Gulf is undergoing increasing pollution from industrial, municipal, and petroleum sources; however, little research in ecotoxicology has been carried out in this ecosystem. In the present study, mercury distribution and accumulation were investigated in muscle, liver, kidney, and feather of the resident Western reef heron (n = 15) and the migratory Siberian gull (n = 15). We also evaluated the relation between Hg concentrations, sex, and age (juvenile vs. adult). Results showed that the highest concentrations of Hg were recorded in the feather (35 ± 0.14-3.0 ± 0.27 mg kg(-1) dw) and at 3.7-, 1.6-, and 1.3-fold in muscle, kidney, and liver, respectively. Concentrations of mercury in tissues of migratory birds were two times higher than in resident birds; geographical differences and feeding habits were used to explain these variations. We found a weak relationship between Hg concentrations in feathers and internal tissues (r ≤ 0.50); conversely, liver presented strong positive correlations with other soft tissues, especially kidney (p > 0.05; r = 0.82). Results showed that sex and age have no significant effects on T-Hg accumulation in these birds (p > 0.05; r < -0.01). Based on these findings, Hg concentrations were low in both species. Therefore, Hg contamination of this aquatic ecosystem is not a threat. Accordingly, we recommend the use of the Western reef heron as a bioindicator of mercury pollution in this region.

Heavy metals and metalloid levels in the tissues of yellow-legged gulls (Larus michahellis) from Spain: sex, age, and geographical location differences

“…In this sense, in wild birds living in environments with little or no industrial activities, the threshold reported for Hg levels in the liver was 10 mg/kg (Fimreite 1974 ). Even when some animals surpassed this threshold, our results (mean and median) of Hg in liver and kidney were below the mentioned threshold and were in accordance with those found by Leonzio et al ( 1986 ) in L. ridibundus in Italy (2.58 ± 1.37 and 2.49 ± 1.71 mg/kg) and Majidi et al ( 2015 ) in L. heuglini in Iran (1.87 ± 0.18 and 1.97 ± 0.21 mg/kg). However, these levels are lower than those found by Leonzio et al ( 1986 ) in liver and kidney of L. argentatus in Italy (13.30 ± 9.25 mg/kg in liver; 10.65 ± 7.82 mg/kg in kidney), who suggested that the food source (marine areas) was responsible for the high Hg levels.…”

Genomic data reveal international lineages of critical priority Escherichia coli harbouring wide resistome in Andean condors (Vultur gryphus Linnaeus, 1758)

“…Metals such as arsenic (As), mercury (Hg), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), iron (Fe), manganese (Mn) and zinc (Zn) do not degrade and these metals could easily accumulate throughout the trophic chain and persist in nature (Borchert, Leaphart, Bryan, & Beasley, 2019; Burger, Mizrahi, Tsipoura, Jeitner, & Gochfeld, 2018; Vizuete et al, 2018); at the same time, As, Cd, Pb and Hg have no established biological functions and are considered as contaminants (Hejna et al., 2018). The presence of HMs has been registered in tissues of wild birds (Bond & Robertson, 2015; Burger et al., 2018; Majidi, Bahramifar, & Ghasempouri, 2015; Sepúlveda & Gonzalez‐Acuña, 2014), including the Andean condor (Di Marzio et al., 2018; Plaza et al, 2019; Wiemeyer et al., 2017). Due to the HM toxicity to different organisms, bacteria have developed some resistance mechanisms and have managed to persist in various highly contaminated locations, constituting possible biomarkers of environmental contamination (Di Cesare, Eckert, & Corno, 2016; Martins, Zanetti, Pitondo‐Silva, & Stehling, 2014; Paul, Chakraborty, & Mandal, 2019; Raychaudhuri et al., 2007).…”