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Modelling the response of a highly eutrophic lake to reductions in external and internal nutrient loading

Abstract
The reduction of macronutrients to levels that limit primary production is often a critical element of mitigating eutrophication and reducing the potential for algal blooms. Lake Okaro has remained highly eutrophic despite an intensive catchment and in-lake restoration programme, including implementation of a constructed wetland, riparian protection, an alum application and application of a modified zeolite mineral (Z2G1) to reduce internal nutrient loading. A one-dimensional process-based ecosystem model (DYRESM-CAEDYM) was used in this study to investigate the need for further nutrient loading reductions of both nitrogen (N) and phosphorus (P). The model was calibrated against field data for a 2-year period and validated over two separate 1-year periods. Model simulations suggest that the trophic status of the lake, measured quantitatively with the Trophic Level Index (TLI), could shift from highly eutrophic to mesotrophic with external and internal loads of both N and P reduced by 75-90%. The magnitude of the nutrient load reductions is indicative of a major challenge in being able to effect transitions across trophic state categories for eutrophic lakes.
Type
Journal Article
Type of thesis
Series
Citation
Özkundakci, D., Hamilton, D.P. & Trolle, D. (2001). Modelling the response of a highly eutrophic lake to reductions in external and internal nutrient loading. New Zealand Journal of Marine and Freshwater Research, 45(2), 165-185.
Date
2011-06
Publisher
Taylor & Francis
Degree
Supervisors
Rights
This article has been published in New Zealand Journal of Marine and Freshwater Research. © 2011 The Royal Society of New Zealand. Used with permission.