Role of terrestrial carbon and base cations in the recovery of damaged aquatic systems

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Clean water and diverse communities of aquatic biota are so dependent on watershed processes that they can be considered "products" of healthy forests in the Boreal Shield Ecozone. Carbon inputs from the terrestrial watershed are key determinants of productivity of dilute lakes, with both particulate and dissolved (DOC) carbon contributing heavily to the foodwebs of receiving lakes and streams. Base cations from forest soils also affect a vast array of aquatic processes, including the toxicity of introduced metals, but base cations are exhibiting depletions across much of the Shield region, while showing enrichment near many urban areas. Better understanding of terrestrial/aquatic linkages is therefore needed before we can predict the single or combined effects of various watershed disturbances or predict the likely trajectories that recovery or recolonization will take after stressors have been removed. The severely impacted watersheds surrounding the metal mining and smelting complex in Sudbury, Canada are classic examples of the protracted effects of multiple stressors in Boreal watersheds. Here, even after more than $1B investment in air pollution control and extensive land reclamation work, recovery of sensitive species of invertebrates in nearshore environments lags decades behind the cleanup efforts. Our study uses a combination of spatial surveys and field and laboratory experiments to detect, measure and evaluate the importance of terrestrial/aquatic linkages in relation to the recovery of invertebrate communities. We also compare and contrast the effects of different disturbance types (forestry, fire, mining) at study sites across Ontario and examine the role of landscape and local habitat factors in shaping benthic invertebrate communities. Our studies are designed to improve our understanding of the fundamental process of recovery from disturbance and to help ecological risk managers design more effective