After water storage in the Three Gorges Reservoir Region,there are no outbreaks of algal blooms in the main stream of the reservoir region,but the density of algae increases obviously. Outbreaks of algal blooms mainly...After water storage in the Three Gorges Reservoir Region,there are no outbreaks of algal blooms in the main stream of the reservoir region,but the density of algae increases obviously. Outbreaks of algal blooms mainly appeared in the tributaries of the reservoir region such as the Xiangxi River,Daning River,Shennong River and Xiaojiang River,but they did not occur every year. The reasons for outbreaks of algal blooms in the tributaries are shown as follows: the existence of sources of algae(blue-green algae) in the Three Gorges Reservoir is the root cause,and the sources include sources existing and being produced in the reservoir and sources from upstream main stream and its tributaries and other related lakes and reservoirs,of which the sources are mainly from the Dianchi Lake; slight or moderate eutrophication of water is the basic condition;hydrologic and hydrodynamic conditions and suitable temperature are conducive to proliferation and aggregation of algae(blue-green algae) after the operation of the Three Gorges Reservoir until outbreaks of algal blooms appear. Outbreaks of algal blooms in the tributaries of the Three Gorges Reservoir Region mainly appear in backwater reaches; they mainly occur in the tributaries in the north of the reservoir region and near to the dam;they mainly appear from March to July; the dominant species of algae( blue-green algae) in the Three Gorges Reservoir are Pyrrophyta,Bacillariophyta and Chlorophyta,but they tend to change into blue-green algae and other algae. To control outbreaks of algal blooms in the tributaries of the Three Gorges Reservoir Region,it is needed to prevent water containing blue-green algae collected from the Dianchi Lake and other lakes and reservoirs from being input into the lower reaches,reduce pollution load flowing into the Three Gorges Reservoir,use enclosures to change hydrodynamic conditions of backwater reaches of the tributaries appropriately,and adopt biological measures such as culturing fish and planting plants to improve ecosystem of the tributaries and other measures to inhibit and eliminate algae and decrease eutrophication level.展开更多
Harmful Algal Blooms (HAB) were investigated to prevent the outbreak of HAB in both freshwater and seawater. Parameters inducing HAB were volcanic eruption, sunlight, aeolian dust, environmental factors (current, pH, ...Harmful Algal Blooms (HAB) were investigated to prevent the outbreak of HAB in both freshwater and seawater. Parameters inducing HAB were volcanic eruption, sunlight, aeolian dust, environmental factors (current, pH, dissolved oxygen, food web, turbulence, growth phase), enzyme, iron, nutrients (carbon, nitrogen, phosphorus, sulfur, silicon, minerals) while the critical growth parameter for the outbreak of HAB was iron (Fe). HAB development was halted in freshwater and seawater due to the sulfur compounds (H2S, sulfates) inducing the deficiency of the dissolved Fe in the water. The atomic ratio of N/P is commonly known to be 16/1 in freshwater and 176/1 in seawater for HAB. Therefore, nitrogen can be a relatively limiting factor in seawater while phosphorus in freshwater. HAB could be prevented by control of growth parameters such as pH, temperature, sunlight, turbulence, nitrogen, phosphorus, iron, and sulfur compounds prior to reaching the early exponential phase of algal growth.展开更多
Denitrification plays an important role in nitrogen(N) removal in freshwater ecosystems.This internal process regulates the fluctuations of N concentration, especially for lakes with high nutrients concentrations and ...Denitrification plays an important role in nitrogen(N) removal in freshwater ecosystems.This internal process regulates the fluctuations of N concentration, especially for lakes with high nutrients concentrations and long residence time. Lakes in Yunnan plateau(southwestern China) provide typical cases, while studies in this region have been rare.Therefore, we studied denitrification of two lakes(Lake Dianchi in hypereutrophic state and Lake Erhai in mesotrophic) in this region. We used acetylene inhibition technique to quantify potential denitrification rate(PDR) of these lakes in April and August, 2015 and 2016. PDR of the sediments ranged 0–1.21 μmol/(N·m^2·hr), and that of overlying water ranged 0–0.24 μmol/(N·L·hr). Then, we used Least Angle Regression to determine the controlling factors for denitrification. Nutrients controlled PDR from two aspects: providing essential nitrogen sources; and affecting the richness and metabolism of denitrifying bacteria. In April, both aspects limited PDR; while only nitrogen sources limited PDR in August, due to depleted nitrate and enhanced denitrifying bacteria activity. Ammonia was most significant to denitrification, indicating that nitrate from nitrification transported to the bottom of wellmixed lake provide major N source by denitrification. The high PDR and low nitrate concentrate in August were evidence of an enhanced internal N cycling by algal blooms.展开更多
Since 2007,the world's largest transregional green tides caused by Ulva prolifera have periodically occurred in China.The morphology of U.prolifera drastically changes during the drifting period,but the reason for...Since 2007,the world's largest transregional green tides caused by Ulva prolifera have periodically occurred in China.The morphology of U.prolifera drastically changes during the drifting period,but the reason for this phenomenon has still been under debate.Our results showed that temperature partly explained the changes in the morphology of U.prolifera,with a determining factor of 0.498.The ratio of highly branched thalli decreased as the temperature increased from around 25 to 30℃.Because morphological changes and physiological acclimation synergistically occurred in floating macroalgae,we hypothesized that if the morphology of U.prolifera is also determined by its development state,and the U.prolifea thalli with different development states should have distinct morphological and physiological traits even under the same environmental conditions.To test the hypothesis,we investigated the photosynthesis of U.prolifera and found a higher photosynthetic capacity but lower photoprotective capacity in algae that grew in the branched development state compared to those in the unbranched development state.Combined with other field observations and lab experiments,we suggest that both temperature and development state contribute to the morphological changes of U.prolifera.Given the varying trends of temperature during U.prolifera blooms in past eleven years and the initial occurrence of U.prolifera thalli in the branched development state in the source of algal bloom,we emphasize the need for source management of green tides.展开更多
文摘After water storage in the Three Gorges Reservoir Region,there are no outbreaks of algal blooms in the main stream of the reservoir region,but the density of algae increases obviously. Outbreaks of algal blooms mainly appeared in the tributaries of the reservoir region such as the Xiangxi River,Daning River,Shennong River and Xiaojiang River,but they did not occur every year. The reasons for outbreaks of algal blooms in the tributaries are shown as follows: the existence of sources of algae(blue-green algae) in the Three Gorges Reservoir is the root cause,and the sources include sources existing and being produced in the reservoir and sources from upstream main stream and its tributaries and other related lakes and reservoirs,of which the sources are mainly from the Dianchi Lake; slight or moderate eutrophication of water is the basic condition;hydrologic and hydrodynamic conditions and suitable temperature are conducive to proliferation and aggregation of algae(blue-green algae) after the operation of the Three Gorges Reservoir until outbreaks of algal blooms appear. Outbreaks of algal blooms in the tributaries of the Three Gorges Reservoir Region mainly appear in backwater reaches; they mainly occur in the tributaries in the north of the reservoir region and near to the dam;they mainly appear from March to July; the dominant species of algae( blue-green algae) in the Three Gorges Reservoir are Pyrrophyta,Bacillariophyta and Chlorophyta,but they tend to change into blue-green algae and other algae. To control outbreaks of algal blooms in the tributaries of the Three Gorges Reservoir Region,it is needed to prevent water containing blue-green algae collected from the Dianchi Lake and other lakes and reservoirs from being input into the lower reaches,reduce pollution load flowing into the Three Gorges Reservoir,use enclosures to change hydrodynamic conditions of backwater reaches of the tributaries appropriately,and adopt biological measures such as culturing fish and planting plants to improve ecosystem of the tributaries and other measures to inhibit and eliminate algae and decrease eutrophication level.
文摘Harmful Algal Blooms (HAB) were investigated to prevent the outbreak of HAB in both freshwater and seawater. Parameters inducing HAB were volcanic eruption, sunlight, aeolian dust, environmental factors (current, pH, dissolved oxygen, food web, turbulence, growth phase), enzyme, iron, nutrients (carbon, nitrogen, phosphorus, sulfur, silicon, minerals) while the critical growth parameter for the outbreak of HAB was iron (Fe). HAB development was halted in freshwater and seawater due to the sulfur compounds (H2S, sulfates) inducing the deficiency of the dissolved Fe in the water. The atomic ratio of N/P is commonly known to be 16/1 in freshwater and 176/1 in seawater for HAB. Therefore, nitrogen can be a relatively limiting factor in seawater while phosphorus in freshwater. HAB could be prevented by control of growth parameters such as pH, temperature, sunlight, turbulence, nitrogen, phosphorus, iron, and sulfur compounds prior to reaching the early exponential phase of algal growth.
基金supported by the National Basic Research Program (973) of China (No.2015CB458900)the National Natural Science Foundation of China (No.51779002)
文摘Denitrification plays an important role in nitrogen(N) removal in freshwater ecosystems.This internal process regulates the fluctuations of N concentration, especially for lakes with high nutrients concentrations and long residence time. Lakes in Yunnan plateau(southwestern China) provide typical cases, while studies in this region have been rare.Therefore, we studied denitrification of two lakes(Lake Dianchi in hypereutrophic state and Lake Erhai in mesotrophic) in this region. We used acetylene inhibition technique to quantify potential denitrification rate(PDR) of these lakes in April and August, 2015 and 2016. PDR of the sediments ranged 0–1.21 μmol/(N·m^2·hr), and that of overlying water ranged 0–0.24 μmol/(N·L·hr). Then, we used Least Angle Regression to determine the controlling factors for denitrification. Nutrients controlled PDR from two aspects: providing essential nitrogen sources; and affecting the richness and metabolism of denitrifying bacteria. In April, both aspects limited PDR; while only nitrogen sources limited PDR in August, due to depleted nitrate and enhanced denitrifying bacteria activity. Ammonia was most significant to denitrification, indicating that nitrate from nitrification transported to the bottom of wellmixed lake provide major N source by denitrification. The high PDR and low nitrate concentrate in August were evidence of an enhanced internal N cycling by algal blooms.
基金supported by the National Key Research and Development Program of China(No.2022YFC3106000)the major innovation project for the science education industry integration pilot project of Qilu University of Technology(Shandong Academy of Sciences)(No.2023JBZ03)+1 种基金the talent research projects of Qilu University of Technology(Shandong Academy of Science)(No.2023RCKY039)the open funding project of Key Laboratory of Marine ecological monitoring and restoration technologies,MNR,China(No.MEMRT202301)。
文摘Since 2007,the world's largest transregional green tides caused by Ulva prolifera have periodically occurred in China.The morphology of U.prolifera drastically changes during the drifting period,but the reason for this phenomenon has still been under debate.Our results showed that temperature partly explained the changes in the morphology of U.prolifera,with a determining factor of 0.498.The ratio of highly branched thalli decreased as the temperature increased from around 25 to 30℃.Because morphological changes and physiological acclimation synergistically occurred in floating macroalgae,we hypothesized that if the morphology of U.prolifera is also determined by its development state,and the U.prolifea thalli with different development states should have distinct morphological and physiological traits even under the same environmental conditions.To test the hypothesis,we investigated the photosynthesis of U.prolifera and found a higher photosynthetic capacity but lower photoprotective capacity in algae that grew in the branched development state compared to those in the unbranched development state.Combined with other field observations and lab experiments,we suggest that both temperature and development state contribute to the morphological changes of U.prolifera.Given the varying trends of temperature during U.prolifera blooms in past eleven years and the initial occurrence of U.prolifera thalli in the branched development state in the source of algal bloom,we emphasize the need for source management of green tides.
