Tracking Fish Lifetime Exposure to Mercury Using Eye Lenses.

Area of Science:

• Environmental Science
• Ecotoxicology
• Aquatic Ecology

Background:

• Mercury (Hg) bioaccumulation in fish is influenced by diet, growth, and environmental factors.
• Traditional fish Hg exposure assessment uses muscle or whole fish, reflecting lifetime averages.
• Tracking chronological Hg exposure in individual fish offers novel insights into bioaccumulation processes.

Purpose of the Study:

• To introduce and validate a novel method for assessing annual-scale mercury (Hg) uptake in fish using eye lenses.
• To investigate age-dependent Hg exposure trends in round goby (Neogobius melanostomus) across different aquatic ecosystems.
• To evaluate the potential of eye lens chronology for understanding Hg bioaccumulation dynamics in relation to environmental change.

Main Methods:

• Aging of individual fish eye lenses using otolith length-age relationships.
• Quantification of mercury (Hg) concentrations in eye lens layers via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).
• Analysis of Hg bioaccumulation trends in round goby from the Baltic Sea, Lake Erie, and the St. Lawrence River.

Main Results:

• Eye lens Hg content demonstrated age-dependent exposure patterns: increasing in Lake Erie and the Baltic Sea, decreasing in the St. Lawrence River.
• These temporal trends in Hg exposure were not discernible using traditional muscle tissue analysis.
• The study successfully established a chronological record of Hg uptake within individual fish.

Conclusions:

• Fish eye lens chronology provides a powerful tool for reconstructing historical Hg exposure at an annual resolution.
• This novel methodology can reveal complex Hg bioaccumulation dynamics not captured by conventional methods.
• The approach holds significant potential for assessing the impact of global change factors, such as hypoxia, on fish Hg exposure.