Changes in algal bloom dynamics in a regulated large river in response to eutrophic status

Sunim Bae and Dongil Seo

Ecological Modelling, 2021, vol. 454, issue C

Abstract: This study aims to analyze the factors affecting algal growth due to hydrologic and hydrodynamic changes resulting from eight weir constructions along a length of 207 km on the Nakdong River. Nutrients for algal growth, light intensity, water temperature, and hydrodynamic conditions were examined to study their relationships with algal blooms. A three-dimensional hydrodynamic and water quality model was calibrated based on data from 2006 to 2008 and verified against data from 2013 to 2015. Four statistics (i.e., R2, ME, Pbias, and CF) were used for the model performance assessment. Changes in algal bloom were not significant in the upper stream area because the nutrient level for algal growth was insufficient compared to that at other locations. On the other hand, as the nutrient concentration increased in the middle stream area, algal blooms increased significantly. The upper and middle streams showed increases in algal growth after the construction of weirs. However, hypereutrophic downstream area locations showed contrasting results, showing an overall reduction in algal growth after the construction of weirs, except for winter, which showed the largest increase in hydraulic residence time. These results seem to have positive and negative effects on algal blooms due to the construction of weirs. The negative effects seem to be greater in hypereutrophic areas because of the decreased average light effect as a result of increased water depth created through the weir constructions, playing a dominant role over the level of nutrients. The impacts of the construction of weirs on the occurrence of algae in the Nakdong River were as follows: 1) As the hydraulic residence time increased, the algal bloom increased where the nutrients were sufficient; 2) when the nutrients were more than sufficient, the average light availability became the dominant factor for algal growth; 3) the temperature effect was not a significant algal-growth-limiting factor for hydrodynamic changes in the river. However, these results have limitations in terms of the model and data accuracy. In order to use them for water resource management, additional field experiments are required for confirmation and verification.

Keywords: Harmful algal blooms; Algal growth-limiting factors; Hydrodynamic and water quality model; Weir construction; Eutrophication; Water quality management (search for similar items in EconPapers)
Date: 2021
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Citations: View citations in EconPapers (4)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:ecomod:v:454:y:2021:i:c:s0304380021001551

DOI: 10.1016/j.ecolmodel.2021.109590

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