The Effects of Irradiance Intensity and Nutrient Concentration on Microcystis Nutrient Uptake
Date Issued
2011
Date
2011
Author(s)
Chuang, Pei-Chia
Abstract
The algal bloom is a serious problem in reservoirs, not only would increase the cost of water treatment, but also result in various problems due to different algal species. Blue-green algae are often the dominant species. Microcystis is one of blue-green algae, and often dominates in reservoirs. We are also concerned about on Microcystis due to some species of Microcystis is able to produce toxins which pose serious health risks to human and animals.
Microcystis is dominant algae in stratified lakes from late spring to early autumn. There are two mechanisms help the Microcystis dominance. The first mechanism is buoyancy regulation which allows Microcystis to overcome the vertical separation of light and nutrients in a stratified lake. The second mechanism is that Microcystis uptakes and stores nutrients more than the amount needed for growth. Therefore, Microcystis can stay in sufficiency of light in surface water for photosynthesis, and uptake nutrient in lower water. Microcystis overcomes the problem of light and nutrient separation, and blooms in stratified subtropical reservoirs.
In this study, we sampled Microcystis from Hsin-Shan reservoir. In order to deplete the intracellular polyphosphate storage, we put change in nutrient free water under light with 14 : 10-h light :dark cycle for 3days. When the experiment began, we added nutrients in water under different irradiance intensities, and measured the changes of nutrient concentrations in water. The amounts of changes were used to calculate the N and P cell quota and uptake rates. The results show that Microcystis has the ability which can uptake and store nutrient in cells. The uptake rate is increases with light intensity, increases with external nutrient concentration and decreases with cell quota. We use Morel model and Okada and Sudo model to simulate the uptake under different irradiance intensity (I), external nutrient concentration(S) and nutrient concentration.
The best fitting parameters in Morel model are：maximum allowed uptake , Qmax-Qmin=27 P-μg‧SS-mg-1, helf saturated nutrient concentration , Ks=0.847 P-mg‧L-1. The best fitting parameters in Okada and Sudo model are： maximum allowed uptake , Qmax-Qmin=23.5 P-μg‧SS-mg-1, helf saturated cell quota , Kq=10.8 P-μg‧SS-mg-1, helf saturated nutrient concentration , Ks=0.3863 P-mg‧L-1. Morel model has R=0.82 , slope=0.805； Okada and Sudo model has R=0.84 , slope=0.645.
Subjects
Microcystis
light intensity
nutrients
buoyancy regulation
vertical movement
phosphorus uptake
P cell quota
SDGs
Type
thesis
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