Mercury in fish in Swedish lakes

Area of Science:

• Environmental Science
• Ecotoxicology
• Aquatic Chemistry

Background:

• Mercury contamination in fish is a significant environmental concern.
• Swedish lakes face challenges with mercury pollution impacting aquatic ecosystems.
• Historical industrial activities continue to influence current mercury levels.

Purpose of the Study:

• To assess the past, present, and future mercury situation in Swedish lake fish.
• To estimate the number of lakes at risk of 'blacklisting' due to mercury.
• To investigate the impact of liming on mercury content in pike.

Main Methods:

• Analysis of a comprehensive dataset from 1456 Swedish lakes.
• Trend analysis of mercury content in 1-kg pike over time.
• Correlation analysis linking mercury levels to various environmental parameters.

Main Results:

• Mercury content in pike shows an increasing trend despite decreased industrial mercury emissions.
• High mercury levels correlate with specific emission sources, historical pollution ('Swedish sins'), and environmental factors like sediment mercury, pH, and water chemistry.
• A predictive formula (r2 = 0.78) was developed to explain mercury levels.
• The number of lakes requiring 'blacklisting' may be significantly higher than currently identified (at least 9400 vs. 250).

Conclusions:

• Past mercury pollution continues to impact Swedish lakes significantly.
• Environmental factors, including sediment contamination and water chemistry, are critical in mercury bioaccumulation.
• Liming operations show potential for reducing mercury content in fish, necessitating further research into its effectiveness and mechanisms.