Impacts of atmospheric nitrogen and phosphorous deposition on the alpine ponds of Banff National Park: The effects on aquatic biodiversity & ecosystem functioning

Background/Question/Methods Nitrogen deposition has doubled in the Canadian Rocky Mountains over the past 20 years due to the increasing use of fertilizers and combustion of fossil fuels. Similarly, phosphorous deposition has also increased in mountainous areas due to expansions in human land-use. Currently, there is no monitoring or active management in Banff National Park for alpine ponds, despite the fact that 44% of the park is categorized as an Alpine Eco-region, and there are 3000 alpine ponds in the park. Increases in atmospheric pollution can result in increased populations of inedible algae, resulting in a loss of species diversity in the zooplankton and periphyton. We used a novel replicated whole-ecosystem approach to determine the effects of the increasing nitrogen and phosphorous deposition on the pond communities. The objectives of the study were to asses nutrient limitations in the ponds, as well as quantify and explain the changes occurring at the benthic and planktonic level. The study was comprised of four parts: A survey of aquatic diversity, a nutrient limitation experiment, a grazing experiment, and a policy recommendation for management strategies. Sixteen alpine ponds located on Snow Pass in the Cascade Valley in Banff National Park were surveyed in the summer of 2008. Results/Conclusions Results show the ponds seem to be more reactive to nitrogen additions, with significant increases in periphyton abundance. Results also indicate that periphyton growth was co-limited by nitrogen and phosphorous, but this does not occur until later in the growing season. We think grazing pressure from benthic invertebrates and large, abundant fairy shrimp may have masked the increases in primary production we expected to see, and my have been the reason the phytoplankton did not show any significant responses to nutrient additions. This research is highly significant because most of the world's water bodies are small, with small ponds representing over 190,000 km2 in surface area worldwide. It is suspected that the changes in the aquatic communities in our alpine ponds due to increasing levels of nutrients means a large number of water bodies in the Canadian Rockies are likely also changing.