Mercury bioaccumulation factors and spurious correlations

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Aquatic Ecology

Background:

• Bioaccumulation factors (BAF) are used to assess contaminant accumulation in aquatic organisms.
• The ratio of biota contaminant concentrations (Cbiota) to aqueous concentrations (Cw) simplifies complex relationships.
• Previous studies have highlighted risks associated with using BAF, including spurious correlation.

Purpose of the Study:

• To identify and explain errors in recent publications using mercury (Hg)-related BAFs.
• To demonstrate how spurious correlation leads to unsupported conclusions.
• To advocate for direct analysis of Cbiota-Cw relationships over BAF ratios.

Main Methods:

• Review and analysis of recent publications on Hg-BAF relationships.
• Examination of statistical significance in Cbiota-Cw relationships.
• Illustrative examples of errors in BAF calculations and interpretations.

Main Results:

• Recent studies incorrectly interpret Hg-BAF relationships due to spurious correlation.
• Misleading conclusions arise from regressing ratios or variables correlated with Cw.
• "Inverse" BAF-Cw relationships often reflect statistical artifacts, not biological mechanisms.

Conclusions:

• Direct analysis of Cbiota-Cw relationships is less ambiguous and prone to error.
• Direct analysis leads to more interpretable and supportable conclusions in aquatic ecosystems.
• Avoiding BAF ratios prevents misinterpretation of contaminant accumulation and uptake mechanisms.