The combined impact of land use change and aquaculture on sediment and water quality in oligotrophic Lake Rupanco (North Patagonia, Chile, 40.8°S)

• Published in: Journal of environmental management 2013-10, Vol.128, p.283-291
• Main Authors: León-Muñoz, Jorge, Echeverría, Cristian, Marcé, Rafael, Riss, Wolfgang, Sherman, Bradford, Iriarte, Jose Luis
• Format: Article
• Language: English
• Subjects: Agriculture; Animal and plant ecology; Animal aquaculture; Animal productions; Animal, plant and microbial ecology; Animals; Applied ecology; Aquaculture; Biological and medical sciences; Chile; Conservation, protection and management of environment and wildlife; decision making; Environment; Farming; fish culture; forests; Fresh water ecosystems; Fundamental and applied biological sciences. Psychology; General aspects; Geologic Sediments; industry; Lakes; Land use; Land use change; Nitrogen; Nitrogen - analysis; nitrogen content; Nitrogen load; Nutrients; pastures; planning; pollution load; Rivers; Salmon; Salmon farming; Salmonidae; Sediment; Sediments; subwatersheds; surface water; Synecology; Water Quality
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2013.05.008

Water and sediment quality in North Patagonia's large, oligotrophic lakes are expected to suffer as native forest continues to be fragmented and degraded by its conversion to cropping and pasture land uses. These changes in land use are expected to increase diffuse nutrient loads to the region's lakes. In addition, these lakes are home to the world's second largest salmon aquaculture industry which provides additional point sources of nutrients within the lakes. We studied the combined influences of land use change and salmon farming on the nutrient concentrations in a North Patagonian lake (Lake Rupanco, 233 km2 water surface, 163 m average depth) in four sub-watersheds ranging in disturbance from near-pristine forest to 53% converted to cropping and pasture. Nitrogen exports from the tributary sub-watersheds increased from 33 kg TN/km2/y to 621 kg TN/km2/y as the proportion of crop and pasture land increased. The combined nutrient load from land use change and salmon farming has led to significant differences in the nitrogen concentrations of the lake's water column and sediments in the near-shore zones across the lake. Total nitrogen concentrations in the sediments varied from 37 ± 18 mg/kg in near-pristine sub-watersheds without salmon farming to 6400 ± 698 mg/kg where the sub-watershed was dominated by crop and pasture lands combined with the presence of salmon farming. These results demonstrate the importance of considering the impacts of both salmon farming and land use on water and sediment quality for future environmental planning, management and decision making. •We studied how the land use and aquaculture influence the nutrient load in a lake.•The North Patagonian lakes show an expansion of lands for livestock.•Salmon farming increases load of nutrient in North Patagonian lakes.•Both uses influence the water and sediment quality of the near-shore zones.•Their joint effect on environment should not be ignored.