Soil Mercury Accumulation Delays Fish Recovery from Atmospheric Deposition Declines

Area of Science:

• Environmental Science
• Ecotoxicology
• Biogeochemistry

Background:

• US mercury emissions have decreased significantly over 30 years due to air quality management.
• Limited data exists on ecosystem and biota responses to declining mercury deposition.
• Long-term mercury cycling data from Arbutus Lake, NY, provides a valuable case study.

Purpose of the Study:

• To synthesize long-term mercury cycling data at Arbutus Lake.
• To evaluate brook trout responses in regional lakes to changing watershed mercury inputs.
• To understand the impact of legacy mercury and climate change on ecosystem recovery.

Main Methods:

• Synthesized long-term data on mercury cycling (2003-2021).
• Analyzed watershed mercury inputs (dry/wet deposition, litterfall).
• Monitored tributary mercury fluxes and lake mercury loading.
• Assessed fish mercury concentrations in regional lakes.

Main Results:

• Watershed mercury inputs decreased, yet the watershed accumulated mercury (25.2 ± 2.8 μg m⁻² yr⁻¹).
• Tributary mercury fluxes showed initial decline followed by recent increase, possibly due to climate factors.
• No significant trends were found in net mercury loading or fish mercury concentrations.

Conclusions:

• Legacy mercury in soils may impede lake biota response to reduced deposition.
• Climate change and altered soil chemistry can influence mercury cycling in forested ecosystems.
• Ecosystem recovery from historical mercury contamination may be a slow, complex process.