Toxic Burdens of Freshwater Biofilms and Use as a Source Tracking Tool in Rivers and Streams

Area of Science:

• Environmental Science
• Ecotoxicology
• Aquatic Ecology

Background:

• Biofilms form the base of riverine food webs, comprising periphyton, bacteria, and detritus.
• Biofilms actively adsorb and sequester organic and inorganic contaminants from the water column.
• Understanding contaminant uptake by biofilms is crucial for assessing ecological impacts.

Purpose of the Study:

• To demonstrate the utility of biofilm contaminant concentrations for source tracking.
• To understand the biological impacts of contaminants at higher trophic levels.
• To investigate the partitioning of organic chemicals and metals onto biofilms.

Main Methods:

• Analyzing contaminant concentrations (PCBs, PBDEs, metals) within the biofilm matrix.
• Correlating biofilm contaminant levels with physical partitioning and bioaccumulation factors (log Kow).
• Comparing biofilm data with bed sediments and water samples for metal input delineation.

Main Results:

• Physical partitioning dominates the uptake of PCBs and PBDEs into biofilms, with uptake near equilibrium for log Kow 5-7.
• Biofilm metal concentrations effectively delineate spatial and temporal variations in metal inputs, outperforming sediments and water.
• Biofilm metal burden correlated with adverse impacts on periphyton metrics and macroinvertebrate ecological integrity.

Conclusions:

• Biofilm contaminant concentrations serve as a valuable environmental medium for source tracking and impact assessment.
• Biofilms provide insights into the partitioning of organic chemicals and act as indicators of metal pollution.
• A clear link exists between metals in biofilms and the ecological health of dependent invertebrates.