Distribution of the mass (mg) of carcass bullet fragments extracted from Belding’s ground squirrel carcasses.

<p>Distribution of the mass (mg) of carcass bullet fragments extracted from Belding’s ground squirrel carcasses.</p

Bullet fragment numbers and mass of Pb fragments associated with known and unknow bullet types used for shooting Belding's ground squirrels in California and Oregon, USA during 2014 and 2015.

<p>Mean and standard error (SE) are back-transformed model derived estimates controlling for the mass of ground squirrels being shot.</p

Radiograph of Belding’s ground squirrel carcass shot with a 20 grain .17 Super Mag bullet.

<p>Bullet fragments appear as white flecks throughout the carcass. Total number of fragments recovered from the carcass was 156; 97% (n = 151) consisted strictly of Pb with a total mass of 61 mg of Pb. Dashed horizontal and vertical lines illustrate how the maximum distribution of bullet fragments was measured relative to the length of carcass (base of the tail to most distal portion of the head) illustrated by the solid lines. White scale object in lower right of image is 12.6 mm in width.</p

Daily cumulative Pb exposure (mg/kg body mass) for nestling golden eagles, red-tailed hawks, and Swainson’s hawks.

<p>Cumulative exposure thresholds for physiology, growth, and survival effects are shown as horizontal lines. </p

Correlation between the estimated mass (mg) of bullet fragments in ground squirrel carcass and estimated total fragment numbers from shot Belding’s ground squirrel carcasses.

<p>Correlation between the estimated mass (mg) of bullet fragments in ground squirrel carcass and estimated total fragment numbers from shot Belding’s ground squirrel carcasses.</p

Ground Squirrel Shooting and Potential Lead Exposure in Breeding Avian Scavengers - Fig 3

<p>Relationship between numbers of bullet fragments in ground squirrel carcasses (A) and partial residuals for mass of bullet fragments (B) and mass of Belding’s ground squirrel carcasses. </p

Mercury Bioaccumulation in Estuarine Fishes: Novel Insights from Sulfur Stable Isotopes

Estuaries are transitional habitats characterized by complex biogeochemical and ecological gradients that result in substantial variation in fish total mercury concentrations (THg). We leveraged these gradients and used carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S) stable isotopes to examine the ecological and biogeochemical processes underlying THg bioaccumulation in fishes from the San Francisco Bay Estuary. We employed a tiered approach that first examined processes influencing variation in fish THg among wetlands, and subsequently examined the roles of habitat and within-wetland processes in generating larger-scale patterns in fish THg. We found that δ³⁴S, an indicator of sulfate reduction and habitat specific-foraging, was correlated with fish THg at all three spatial scales. Over the observed ranges of δ³⁴S, THg concentrations in fish increased by up to 860% within wetlands, 560% among wetlands, and 291% within specific impounded wetland habitats. In contrast, δ¹³C and δ¹⁵N were not correlated with THg among wetlands and were only important in low salinity impounded wetlands, possibly reflecting more diverse food webs in this habitat. Together, our results highlight the key roles of sulfur biogeochemistry and ecology in influencing estuarine fish THg, as well as the importance of fish ecology and habitat in modulating the relationships between biogeochemical processes and Hg bioaccumulation

Supplement 1. Limnological and chemical data for surface water and bottom water from seven stations at Clear Lake over 22 potential sampling dates from May 1994 through May 1997.

<h2>File List</h2><blockquote> <p><a href="limno-chem-data.txt">limno-chem-data.txt</a> -- ASCII file. </p> </blockquote><h2>Description</h2><blockquote> <p>The file limno-chem-data.txt contains limnological and chemical data for surface water and bottom water from 7 stations at Clear Lake over 22 potential sampling dates from May 1994 through May 1997. Data for each station include: temperature (°C), pH, specific conductivity (mS/cm), total dissolved solids (Km/L), dissolved oxygen (mg/L), turbidity (NTU), reduction/oxidation potential (mV), total organic carbon (mg/L), dissolved organic carbon (mg/L), humic acids (mg/L), total suspended solids (mg/L), sulfate (mg/L), total mercury - filtered water (ng/L), methyl mercury - unfiltered water (ng/L), methyl mercury - filtered water (ng/L). Minimum, maximum, and mean values for each parameter at each station/depth are provided at the bottom of each of the 14 data tables. Also included in the last column on each data table is a ROW SUM value (cumulative sum of values for each data row) to assis in QA/QC of downloaded data.</p> </blockquote

Mercury Exposure Associated with Altered Plasma Thyroid Hormones in the Declining Western Pond Turtle (<i>Emys marmorata</i>) from California Mountain Streams

Mercury (Hg) is a global threat to wildlife health that can impair many physiological processes. Mercury has well-documented endocrine activity; however, little work on the effects of Hg on the thyroid hormones triiodothyronine (T3) and thyroxine (T4) in aquatic wildlife exists despite the fact that it is a sensitive endpoint of contaminant exposure. An emerging body of evidence points to the toxicological susceptibility of aquatic reptiles to Hg exposure. We examined the endocrine disrupting potential of Hg in the western pond turtle (<i>Emys marmorata</i>), a long-lived reptile that is in decline throughout California and the Pacific Northwest. We measured total Hg (THg) concentrations in red blood cells (RBCs) and plasma T3 and T4 of turtles from several locations in California that have been impacted by historic gold mining. Across all turtles from all sites, the geometric mean and standard error THg concentration was 0.805 ± 0.025 μg/g dry weight. Sampling region and mass were the strongest determinants of RBC THg. Relationships between RBC THg and T3 and T4 were consistent with Hg-induced disruption of T4 deiodination, a mechanism of toxicity that may cause excess T4 levels and depressed concentrations of biologically active T3

Appendix A. Habitat-specific designations for fish prey items.

Habitat-specific designations for fish prey items