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Kristy HogsdenCompensatory Species Dynamics and Grazing in Recovering Acidified Lakes: Regulation of Biological Recovery Responses

There was no significant difference between consumer treatment levels on the development of periphyton in either stressed or recovered lakes. For example, the open treatment when all consumers had access had almost the same impact on periphyton as the fine treatment restricted to only small consumers. These results may be the first indication that chlorophyll a is not a precise measure of grazing pressure. This suggests that finer scale responses, such as algal biovolume and taxonomic analyses, may reveal differences between consumer size treatments.

Chlorophyl a measurements in stressed lakes, which measure the development of periphyton
Grazing did not suppress chlorophyll a inferred
development of periphyton in stressed (a) or recovered (b) lakes.
Chlorophyl a measurements in recovering lakes, which measure the development of periphyton
Why is this important?

If grazing is an important regulator of algal communities while acidity changes, recovery may not closely track chemical recovery. Since boreal ecosystems are naturally species-poor and communities rely on only a few species to perform ecological processes, the impacts of delayed recovery could be considerable. The effects of sustained losses in biodiversity in boreal ecosystems are currently unknown. Knowledge of differential recovery rates of biological communities can be used to determine appropriate timing for species re-introductions which have been proposed to facilitate recovery in stressed lake ecosystems.

Future Research

Current research involves collecting algal taxonomic and biovolume data, which will be used to identify compensatory species dynamics and determine if benthic consumers selectively change algal assemblages during acidity changes.

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