Feather mercury concentrations and physiological condition of Great Egret and White Ibis nestlings in the Florida Everglades

Department of Biological Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA
Science of The Total Environment (Impact Factor: 4.1). 02/2009; DOI: 10.1016/j.scitotenv.2008.12.043
Source: PubMed


Mercury contamination in the Florida Everglades has reportedly played a role in the recent decline of wading birds, although no studies have identified a mechanism leading to population-level effects. We assessed feather mercury levels in great egret (Ardea alba; n = 91) and white ibis (Eudocimus albus; n = 46) nestlings at breeding colonies in the Florida Everglades during a year (2006) with excellent breeding conditions (characterized by hydrology leading to concentrated prey) and a year with below average breeding conditions (2007). We also assessed the physiological condition of those nestlings based on levels of plasma and fecal corticosterone metabolites, and stress proteins 60 and 70. Mercury levels were higher in both species during the good breeding condition year (great egret = 6.25 μg/g ± 0.81 SE, white ibis = 1.47 μg/g ± 0.41 SE) and lower in the below average breeding year (great egret = 1.60 μg/g ± 0.11 SE, white ibis = 0.20 μg/g ± 0.03 SE). Nestlings were in better physiological condition in 2006, the year with higher feather mercury levels. These results support the hypothesis that nestlings are protected from the harmful effects of mercury through deposition of mercury in growing feathers. We found evidence to suggest shifts in diets of the two species, as a function of prey availability, thus altering their exposure profiles. However, we found no evidence to suggest they respond differently to mercury exposure.

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Available from: Darren G. Rumbold, Oct 06, 2015
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    • "Stress responses on HSPs have been shown to be induced by cold and a range of other stresses (Sorensen et al., 2003; Herring et al., 2009). During the present study on dermal fibroblasts of Tharparkar and Karan-Fries cattle, a non-significant increase in the HSP70 gene expression (HSPA8, HSPA1A and HSPA2) was observed on mild cold exposure (25 1C) as compared to control (37 1C) (Figs. "
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    ABSTRACT: The present studies were conducted to investigate the difference response of dermal fibroblasts to heat stress in Tharparkar and Karan-Fries cattle. Skin is the important environmental interface providing a protective envelope to animals. In skin, dermal fibroblasts are the most regular cell constituent of dermis that is crucial for temperature homeostasis. The study aimed to examine the reactive oxygen species (ROS) formation, cytotoxicity (%) and heat shock protein 70 (HSP70) genes expression in dermal fibroblast of Tharparkar and Karan-Fries cattle and to assess whether resistance of dermal fibroblast to heat stress is breed specific. Dermal fibroblasts from ear pinna of Tharparkar and Karan-Fries cattle were exposed at 25 °C, 37 °C, 40 °C and 44 °C for 3 h to measure the ROS, cytotoxicity (%) and HSP 70 (HSPA1A, HSPA2 and HSPA8) genes expression. The results showed that ROS formation at low temperature (25 °C) decreased in both breeds as compared to control (37 °C) and the differences were significant (P<0.0001). Heat stress of 40 °C did not increase ROS formation significantly in Tharparkar but increased significantly (P<0.001) in Karan-Fries cattle. The overall cytotoxicity (%) was also found to be significantly different (P<0.001) between Tharparkar and Karan-Fries cattle, and on exposure to different temperature (P<0.001). The cytotoxicity (%) in dermal fibroblast cells of Karan fries cows were more than Tharparkar. The expression studies indicated that all HSP70 genes (HSPA8, HSPA1A and HSPA2) were up regulated at different temperature in both breeds. In Tharparkar, relative mRNA expression of HSPA8 gene was higher but HSPA1A and HSPA2 genes were low as compared to Karan-Fries cattle. At 40 and 44 °C, the relative expressions of inducible HSP 70 genes (HSPA1A and HSPA2) were higher in Karan-Fries than Tharparkar. In summary, dermal fibroblasts resistance to heat shock differed between breeds. Dermal fibroblasts of Tharparkar were observed to be more heat tolerant than crossbred Karan-Fries cattle. Study concludes that Zebu cattle (Tharparkar) dermal fibroblasts are more adapted to tropical climatic condition than crossbreed cattle (Karan-Fries). Differences exist in dermal fibroblasts of heat adapted and non-adapted cattle.
    Journal of Thermal Biology 05/2014; 43:46–53. DOI:10.1016/j.jtherbio.2014.04.006 · 1.51 Impact Factor
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    • "Besides nutrients , wading birds in the Everglades may transport Hg to their nesting site via guano. This is because wading birds in the Everglades prey on invertebrates and fish from the marsh and accumulate high Hg concentrations in their feathers and eggs (Herring et al., 2009). However, Hg deposition from wading bird guano in the Everglades tree island soils has not been reported. "
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    ABSTRACT: Tree islands are habitat for wading birds and a characteristic landscape feature in the Everglades. A total of 93 surface soil and 3 soil core samples were collected from 7 degraded/ghost and 34 live tree islands. The mean Hg concentration in surface soils of ghost tree islands was low and similar to marsh soil. For live tree islands, Hg concentrations in the surface head region were considerably greater than those in mid and tail region, and marsh soils. Hg concentrations in bird guano (286 μg kg(-1)) were significantly higher than those in mammal droppings (105 μg kg(-1)) and plant leaves (53 μg kg(-1)). In addition, Hg concentrations and δ(15)N values displayed positive correlation in soils influenced by guano. During 1998-2010, estimated annual Hg deposition by guano was 148 μg m(-2) yr(-1) and ∼8 times the atmospheric deposition.
    Environmental Pollution 09/2013; 184C:313-319. DOI:10.1016/j.envpol.2013.08.037 · 4.14 Impact Factor
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    • "However, dry-out conditions can occur due to water availability at which time THg and MeHg hotspots within the storm water treatment areas and fluxes in both THg and MeHg surface water concentrations can occur (Fink 2000). Increased ecological exposure to mercury has adversely affected wildlife species within the greater everglades ecosystem, potential causing a significant decline in biota, especially wading bird species due to bioaccumulation of Hg through consumption of Hg laden fish (Herring, Gawlik, and Rumbold 2009 "
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    ABSTRACT: Significant amount of science and effort has been placed on understanding the bio-geochemical cycle of mercury within the Florida everglades. The range of resolution for these studies include regional (Everglades Protection Area) and site specific scales, with very little attention being given to the landscape scale. However a lot of questions still exist regarding methyl mercury (MeHg) synthesis, bioaccumulation and environmental accumulation. I used the Geti-Ord Gi* spatial clustering statistic to describe and evaluate soil total mercury (THg) and MeHg data collected by U.S. Environmental Protection Agency Regional Environmental Monitoring and Assessment Program between 1995 and 2005. Soil mercury (total and methyl) displayed distinct spatial clustering within Water Conservation Area 3 (WCA3) and was dependant on canal density, water control structure density and hydroperoid. Total mercury hotspots were identified consistently within the southern portion of WCA3A and WCA3B in areas with prolonged hydroperiods (360.9 ± 0.7 days), low canal densities (0.064 ± 0.008 canals/km2) and low structure densities (0.008 ± 0.001 structures/km2). MeHg hotspots consistently occurred within the northern portion of WCA3A, and during the last year of sampling in WCA3B. MeHg hotspots occurred in areas with shorter hydroperiods (282.0±8.8 days), lower canal density (0.109 ± 0.013 canals/km2) and higher structure density (0.029 ± 0.005 structures/km2). Results presented in this study provide further understanding to Hg hotspot dependence on hydrological factors and potentially help guide water management decisions.
    Annals of GIS 06/2013; 19(2):79. DOI:10.1080/19475683.2013.782469
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