Natalie Stark presents 'Northern sea otters (Enhydra lutris kenyoni) as indicators of changing mercury dynamics in Kachemak Bay, Alaska', Feb. 20

Natalie Stark, a master's candidate in biology, will defend the thesis "Northern sea otters (Enhydra lutris kenyoni) as indicators of changing mercury dynamics in Kachemak Bay, Alaska" on Feb. 20.

Abstract

Mercury (Hg) is a naturally occurring heavy metal that has adverse health effects at high concentrations in various species. Upper trophic level predators in aquatic ecosystems, such as marine mammals, are more vulnerable to higher concentrations of Hg due to bioaccumulation and biomagnification processes. In Alaska, changes in the physical and biological characteristics of marine ecosystems are expected to affect the transport and fate of Hg in the environment, which could pose significant risks to wildlife and coastal communities that rely on healthy natural resources. Northern sea otters (Enhydra lutris), a keystone species for the health and diversity of nearshore ecosystems, have small home ranges and localized foraging behavior, making them an effective sentinel for identifying the presence of contaminants and pathogens in the local environment. This study quantified total Hg concentrations ([THg], µg/g) in hair (n=24), muscle (n=50), liver (n=58), kidney (n=60), and heart (n=59) tissues from stranded Northern sea otters (n=72) in Kachemak Bay, Alaska, from 2004 to 2024. Among paired tissues, [THg] varied significantly, with hair and liver showing the highest values. Age class and sex were relevant factors in tissues such as hair and kidney. Hair [THg] ranged from 0.19 - 6.25 µg/g dry weight and liver from 0.02 - 1.93 µg/g wet weight, consistent with previously reported values for sea otters within Southcentral and Southeast Alaska, as well as the Commander Islands. Muscle [THg] (0.01-1.04 µg/g wet weight) was comparatively low to other marine mammals, helping to address a key data gap for this species. No significant associations were detected between [THg] and confirmed Streptococcus infections or cause of death. Findings from this study fill critical data gaps in contaminant surveillance for Southcentral Alaska sea otters and provide a baseline for evaluating and monitoring spatiotemporal trends, climate change impacts, and potential interactions between contaminants and pathogen dynamics in nearshore ecosystems.

Event details

Event location - The Rae Building, Seward, Alaska and Zoom
Event date - Feb. 20. 2026
Event start time - 1 p.m.
Event end time - 2 p.m.

Zoom link