Defense Date

4-21-2023

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Amy C. Hirons

Second Advisor

Dimitri Giarikos

Third Advisor

Michael Adkesson

Fourth Advisor

David Kerstetter

Fifth Advisor

Matthew Allender

Keywords

Heavy metals, Humboldt penguin, eggshell, yolk, albumen, serum, SECLER maternal offloading

Abstract

The Humboldt penguin, Spheniscus humboldti, has been recognized as a Vulnerable species (IUCN) for nearly two decades, with annual population declines of more than 10% largely attributed to pervasive anthropogenic activity occurring throughout the species’ range of Peru and Chile. Due to recent mining expansions near the species’ largest Peruvian rookery, located at the Punta San Juan (PSJ) reserve, the exposure of breeding individuals to elevated concentrations of trace elements (e.g., heavy metals) in the marine environment is a preeminent concern. While heavy metal toxicity is dependent on metal species, dose, route of exposure, and the physiologic parameters of exposed individuals (sex, age, body condition, immune status), chronic exposure can cause severe detriment, including endocrine dysfunction, neurological disruption, and immunohematological complications. Maternal offloading of contaminants into eggs is a mechanism of toxin elimination in birds, and the present study aimed to quantify heavy metal concentrations in egg components as a potential indication of this process in the Humboldt penguin. The presence of sixteen heavy metals, with emphasis on metals found in mine efflux (arsenic, cadmium, copper, lead, mercury, selenium, and zinc), was assessed via inductively-coupled plasma mass spectrometry (ICP-MS) in eggshells collected from wild Humboldt penguin rookeries at PSJ and whole eggs (eggshell, yolk, and albumen) from Humboldt penguins under professional care at the Brookfield Zoo. Serum samples from Humboldt penguins at the Brookfield Zoo were also assessed to determine circulating heavy metal levels in the adult birds. Data analyses indicate a clear delineation between egg constituents, with lipid-rich components (i.e., yolk) displaying notably higher concentrations of As (0.20 ± 0.064), Co (0.01 ± 0.003), Cr (0.086 ± 0.03), Fe (238.65 ± 54.72), Mn (2.71 ± 0.66), Mo (0.57 ± 0.14), Pb (0.32 ± 0.97), Sn (3.29 ± 0.99), and Zn (64.03 ± 13.01), than other components (albumen, carbonate shell, and serum). Wild eggshells had the highest concentrations of Al (9.28 ± 5.22), Cd (0.016 ± 0.02), and V (0.041 ± 0.03), while captive eggshells exhibited the highest concentration of Ni (0.31 ± 1.29). Albumen had the highest concentrations of Cu (4.02 ± 1.22), Hg (0.62 ± 0.22), and Se (1.52 ± 0.45). Significant differences in heavy metal concentrations between egg component types and wild vs. captive specimens were identified. Serum collection, out of sequence relative to egg production and laying, precluded quantification of maternal offloading, but these data provided valuable baseline heavy metal values for adult birds during the non-breeding season. By determining the extent of heavy metal offloading that occurs via egg production in Humboldt penguins, linkages between contaminants, embryo viability, and the likelihood of post-hatch chick mortality may be established using existing avian toxicity literature, which will further efforts to conserve wild populations in Peru.

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