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Influence of forest fire on methyl mercury in macroinvertebrate and fish communities on the boreal plain

Author(s): Allen, E. W.

Year: 2003

Recent studies suggest that logging can increase methyl mercury (MeHg) concentrations in aquatic biota. To determine if forest fire has a similar effect, I studied MeHg in macroinvertebrates and fish from 5 burned and 7 reference lakes on Alberta's Boreal Plain. Two years post-fire, MeHg concentrations in aquatic biota were similar between burned and reference lakes. MeHg concentrations were inversely correlated with lake water pH, total phosphorus concentration, and hardness, reflecting an elevational gradient in lake productivity. A second study was initiated when fire interrupted a logging experiment in a reference watershed. Three months post-fire, MeHg concentrations in biota decreased by 1.3- to 1.5-fold from pre-disturbance concentrations. Lake water concentrations of dissolved organic carbon and inorganic nitrogen increased by 1.2- and 10-fold respectively. Over the short-term, forest fire does not appear to increase MeHg concentrations in aquatic biota on the Boreal Plain.