University of Twente Student Theses


Exploring impact of temperature and precipitation on cyanobacteria in Lake Naivasha

Pande, Shruti (2022) Exploring impact of temperature and precipitation on cyanobacteria in Lake Naivasha.

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Abstract:Fresh water lakes are an important for society. They a major source of drinking water in many regions. Farmers use lake water for irrigation. Many local communities are dependent on the lake for the fish stock for livelihood as well as for food. Lake water is used by industries for their functioning. In some regions the lake water contributes towards the electricity generation. Lakes enhance the natural beauty which leads development of tourism and water sports activities such as water skiing, adventure boating, fishing. In current scenario, due to increase in these activities the water quality of lake is deteriorating due to eutrophication or addition of nutrients in the lake water. The eutrophication in lake is causing uncontrolled growth of cyanobacteria leading to blooms. Certain species cyanobacteria produce toxins that harm the lake water ecosystems as well as the human welfare by contaminating the drinking water supplies. Therefore, it is important to monitor them. In addition to eutrophication, increase in lake surface water temperature and changes in precipitation pattern due climate change are enhancing the bloom intensity as well as the frequency of cyanobacterial blooms events. Cyanobacteria thrive in warm water temperature with high concentration of nutrients especially nitrogen and phosphorous. To understand the weather increase in lake surface water temperature or changes in precipitation patterns are the cause for cyanobacterial bloom in freshwater lakes, Lake Naivasha was selected as study area. To understand the relationship, first trends in surface water temperature and precipitation derived from satellite data were investigated. Next presence of photosynthetic pigment phycocyanin and chlorophyll-a present in cyanobacteria was detected by using remote sensing reflectance and analyzed. Later the growth window for cyanobacteria bloom was determined and bloom indices such as bloom intensity, bloom extend, and bloom severity were estimated during the growth windows. The study concluded that the lake surface water temperature is stable and not increasing. The lake surface water temperature does not have any effect on cyanobacterial growth, but it is at ideal temperature for certain species of cyanobacteria to thrive on. The Precipitation patterns have not changed drastically but it seems to have a stronger influence than lake surface water temperature on the bloom indices, but the results may be inconclusive probably due to overestimation of precipitation, shorter time series, issues retrieval of chlorophyll-a and phycocyanin by using lake water-leaving reflectance. For future estimation of cyanobacterial bloom over lake Naivasha, satellite data providing longer time series is recommended. The algorithm used by this study to detect cyanobacteria could not determine its presence for some years therefore using a different algorithm might help in better understanding blooms. Understanding the nutrient inputs in lake Naivasha will further strengthen the results.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Subject:43 environmental science
Programme:Geoinformation Science and Earth Observation MSc (75014)
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