Based on the remote sensing images of algae, the present work analyzes the horizontal distribution characteristics of algal blooms in Chaohu Lake, China, which also reveals the frequency of algal blooms under differen...Based on the remote sensing images of algae, the present work analyzes the horizontal distribution characteristics of algal blooms in Chaohu Lake, China, which also reveals the frequency of algal blooms under different wind directions. Further, an unstructured-grid, three-dimensional finite-volume coastal ocean model （FVCOM） is applied to investigate the wind-induced currents and the transport pro- cess to explain the reason why algal blooms occur at the detected places. We first deduce the primary distribution of biomass from overlaid satellite images, and explain the formation mechanism by analyzing the pollution sources, and simulating the flow field and transportation process under prevailing wind over Chaohu Lake. And then, we consider the adjustment action of the wind on the corresponding day and develop a two-time scale approach to describe the whole formation process of algae horizontal distribution in Chaohu Lake. That is, on the longer time scale, i.e., during bloom season, prevailing wind determines the primary distribution of biomass by inducing the characteristic flow field; on the shorter time scale, i.e., on the day when bloom occurs, the wind force adjusts the primary distribution of biomass to form the final distribution of algal bloom.展开更多
In order to protect the city of New Orleans from the Mississippi River flooding, the Bonnet Carré Spillway (BCS) was constructed from 1929 to 1936 to divert flood water from the river into Lake Pontchartrain and ...In order to protect the city of New Orleans from the Mississippi River flooding, the Bonnet Carré Spillway (BCS) was constructed from 1929 to 1936 to divert flood water from the river into Lake Pontchartrain and then into the Gulf of Mexico. During the BCS opening for flood release, large amounts of freshwater, nutrients, sediment, etc. were discharged into Lake Pontchartrain, and caused a lot of environmental problems. To evaluate the environmental impacts of the flood water on lake ecosystems, a two-dimensional numerical model was developed based on CCHE2D and applied to simulate the flow circulation, sediment transport and algal biomass distribution in Lake Pontchartrain. The effect of sediment concentration on the growth of algae was considered in the model. The numerical model was calibrated using field measured data provided by USGS, and then it was validated by the BCS Opening Event in 1997. The simulated results were generally in good agreement with filed data and satellite imagery. The field observation and numerical model show that during the spillway opening for flood release, the sediment concentration is very high, which greatly restricts the growth of algae, so there is no algal bloom observed in the lake. After the closure of BCS, the sediment concentration in the lake reduces gradually, and the nutrient concentration of the lake is still high. Under these conditions, numerical results and satellite imagery showed that the chlorophyll concentration was high and algal bloom might occur.展开更多
水生植被和藻类作为湖泊生态系统的主要初级生产者,对湖泊生态系统具有重要作用。在气候变化和人类活动的双重作用下,湖泊富营养化加剧,水生植被退化,藻类水华频发。开展湖泊水生植被群落和藻类水华的长期观测可为湖泊生态系统水生植被...水生植被和藻类作为湖泊生态系统的主要初级生产者,对湖泊生态系统具有重要作用。在气候变化和人类活动的双重作用下,湖泊富营养化加剧,水生植被退化,藻类水华频发。开展湖泊水生植被群落和藻类水华的长期观测可为湖泊生态系统水生植被修复和藻类水华管控提供决策依据。本研究以太湖流域浅水湖泊长荡湖为研究区,基于1985-2021年的Landsat 5和8卫星数据,利用VBI(vegetation and bloom indices)草藻分类算法,开展了浮叶/挺水植被、沉水植被和藻类水华长时序时空演变分析。结果表明:36年来,长荡湖水生植被(包括浮叶/挺水植被和沉水植被)都呈现显著下降趋势,其中沉水植被下降趋势尤为明显,沉水植被从湖中心向岸边逐步退化,其覆盖度从1985年的75%下降至2021年的不足21%;自2011年起,长荡湖水生植被优势生活型从沉水植被转变为浮叶/挺水植被;2010年首次监测到水华发生,2020年和2021年连续两年均监测到湖中心有大面积水华。基于湖泊围网面积和气象数据分析发现,围网拆除是水生植被退化和优势生活型转变的主要因素。展开更多
An unusual feature of the saline stratified lakes that were formed due to ongoing postglacial uplift on the White Sea coast is the presence of several differently colored thin layers in the zone with sharp gradients. ...An unusual feature of the saline stratified lakes that were formed due to ongoing postglacial uplift on the White Sea coast is the presence of several differently colored thin layers in the zone with sharp gradients. Colored layers in five lakes at various stages of separation from the sea were investigated using optical microscopy, spectrophotometry, spectrofluorimetry, and photobiology. The upper greenish colored layer located in the aerobic strata of all lakes near the compensation depth of 1% light penetration contains green algae. In the chemocline, another layer, brightly green, red or pink, is dominated by mixotrophic flagellates. Despite the very low light intensities and the presence of H 2 S, active photosynthesis by these algae appears to be occurring, as indicated by high values of the maximum quantum yield of primary photochemistry, electron transport activity, photosynthetic activity of photosystem II, the fraction of active centers, and low values of heat dissipation. In the reduced zone of the chemocline, a dense green or brown suspension of anoxygenic phototrophs(green sulfur bacteria) is located.展开更多
Harmful algal blooms (HABs) in freshwater ecosystems, especially of cyanobacterial species, are becoming more frequent and expanding geographically, including in Lake Erie in North America. HABs are the result of comp...Harmful algal blooms (HABs) in freshwater ecosystems, especially of cyanobacterial species, are becoming more frequent and expanding geographically, including in Lake Erie in North America. HABs are the result of complex and synergistic environmental factors, though N or P eutrophication is a leading cause. With global mean temperatures expected to increase an additional 2°C - 5°C by 2100, cyanobacterial blooms are predicted to increase even more, given their typically-high temperature optimum for growth. We investigated how increases in temperature and nitrogen, singly or in combination, affect the growth, food quality, and herbivory of Lake Erie cyanobacteria. Algal community samples collected from Lake Erie, and isolated non-N-fixing (Microcystis aeruginosa) and N-fixing (Anabaena flos-aquae) cyanobacterial species, were cultured at 20°C, 25°C, or 30°C, and at 5, 50, 150, or 250 μM N, and then analyzed for growth and (for isolates) content of total protein and non-structural carbohydrates (NSC). Temperature and N both affected algal growth, and there were temperature × N interactions, which were sometimes affected by presence/absence of zooplankton. For example, cyanobacteria (but not green algae) growth increased with both temperature and N, especially from 25°C to 30°C, but N and herbivore presence increased cyanobacterial growth primarily only at 30°C. In general, temperature and N had little consistent effect on NSC, but increasing temperature and N tended to increase protein content in Microcystis and Anabaena (temperature effects mostly at higher N levels). In Anabaena, increases in N did not increase growth or protein at 20°C or 25°C, but did increase both at 30°C, indicating that N fixation is damaged at high temperatures and that high NO3 can overcome this damage. These results indicate that future global warming and continued eutrophication will increase cyanobacterial growth, as well influence algal herbivory and competition between N-fixing and non-N-fixing cyanobacteria.展开更多
Carbon resources play an important role in affecting the benthic bacterial community in shallow lakes. In this study, pyrosequencing was applied to compare bacteria phylogenic profile in incubated sediments with norma...Carbon resources play an important role in affecting the benthic bacterial community in shallow lakes. In this study, pyrosequencing was applied to compare bacteria phylogenic profile in incubated sediments with normal and exchanged organic detritus in macrophyte-dominated East Lake Taihu and algal-dominated Meiliang Bay. We observed significant bacteria species variations in sediments from two bays, regardless of treatments. RDA (Redundancy Analysis) analysis showed that sediment characteristics, especially concentrations of total nitrogen might account for this differentiation. Besides, algal-dominated Meiliang Bay sediment with addition of Vallisneria detritus exhibited higher bacterial species variations than the sediment amended with Microcystis detritus. To the contrary, sediments from macrophyte-dominated East Lake Taihu shared similar bacteria profile at all taxonomic levels and grouped together in MDS (multidimensional scaling) plots over the treatments with Vallisneria or Microcystis detritus addition into the sediment. We speculated that the different degradability of macrophyte detritus and algal detritus led to varied bacterial responses to exchanged organic resources and ultimately, the amounts, nutrient availability and degradability of organic resources may be main reasons for benthic bacteria community structure differentiation between the two states in shallow lakes.展开更多
Exposure to microcystin poses a potential health hazard to humans and other living organisms. This results from eutrophication and warrants an investigation into the problem of microcystin toxicity in Lake Victoria. T...Exposure to microcystin poses a potential health hazard to humans and other living organisms. This results from eutrophication and warrants an investigation into the problem of microcystin toxicity in Lake Victoria. This study was conducted in Homa Bay, Kisumu, Siaya and Busia counties to understand the effects of microcystin toxicity among fisherfolk and lake riparian communities. Data collection involved 90 semi-structured questionnaires, 11 key informant interviews and seven focus group discussions. Water samples were also collected and analysed for algal toxins. Data were analysed using Stata version 13 (Stata Corp, College Station, Texas, USA) and SPSS version 18.0. Majority (73.3%) of the fisherfolk were aware of microcystin toxicity in the lake with no significant difference in the awareness of microcystin toxicity between men and women (χ<sup>2</sup> = 1.1, df = 1, p = 0.293). Most of the respondents relied on lake (48.9%) and tap water (47.8%) with paltry sourcing water from borehole (16.8%) and rain (7.8%). There was no association between level of education and water source (lake;χ<sup>2</sup> = 1.61, df = 3, p = 0.656) and (tap;χ<sup>2</sup> = 2.23, df = 3, p = 0.527). Fisherfolk was cognizant of the need to curb microcystin toxicity. There was a significant difference (p < 0.05) in the occurrence of microcystin during the wet season compared to the dry season. Cyanophytes were the most significant (p < 0.001) group of phytoplankton. When ingested, microcystin has a long-term effect and therefore pollution control is crucial.展开更多
Growing trends in industrialization in Ethiopia have raised concerns about pollution of water bodies particularly of lakes. This study was therefore conducted to 1) characterize the chemical contents of major industri...Growing trends in industrialization in Ethiopia have raised concerns about pollution of water bodies particularly of lakes. This study was therefore conducted to 1) characterize the chemical contents of major industrial effluents (namely textile ceramic and soft drink factories) that reached Lake Hawassa and 2) investigate the effects of the above mentioned factory effluents on survival of larvae fish and growth of algae. Effluent samples were collected from the outlet lagoons of each factory in December, 2009. Then, effluent samples were analyzed for total N, NO3-N, NH4-N, S2-, , , COD, total dissolved solids (TDS) and heavy metals at the federal Environmental Protection Agency (EPA) Laboratory, Addis Ababa. The experiments on the impact of effluents on survival of fish larvae and growth of algae were conducted using six concrete paved ponds (with different concentration of effluent). The results of chemical analysis showed that textile effluent had high COD (nearly 3 times higher), TDS (19 times higher) as well as (39 times higher) than the maximum permissible limits (MPL) set by Environmental Protection Authority (EPA). Among heavy metals, Zn and Fe of textile effluent were much higher (41 and 1.5 times higher, respectively) than the MPL set by EPA. Ceramic effluent also contained high concentration of (24.5 times), S2-, (2 times) and Zn (14 times) exceeding the limit of EPA. Regarding soft drink factory, high values of COD, and Zn were found in the effluent than the limit specified by EPA. The biological treatment lagoons of the respective source were not effective since the effluents were taken from the last treatment lagoon (outlet lagoon) and some of the measured parameters were higher than MPL. Results of the pond experiment showed that 5%, 10% and 20% concentration levels of the HTF effluent killed significantly high proportion of the fry (65%, 86.8% and 88.7%, respectively). In contrast, fry mortality in ceramic and soft drink effluent treatments, even at 10 and 20% concentration levels, stayed nearly below 10%, which were not far off from the mortality of the control groups. Algal biomass in the treated ponds varied with the type of effluent treatment and concentration level. Compared with the first day, chlorophyll “a” concentration measured on the 7th day had increased by 51%, 48%, 74%, 27% and 31% at 0%, 1%, 5%, 10% and 20% concentrations, respectively of textile effluent. The 5% treatment level of textile effluent caused the highest rate of algal growth above the growth rate observed in the control pond, but further increased in concentration to 10% and 20% resulted in a lower growth of algae than in the control pond. Therefore, textile effluent may boost up algae growth at lower concentrations (~5%) but at higher concentration levels its toxic effect may become inhibitory. Regarding the effluent of soft drink factory, algal growth progressively diminished with increasing concentration of the effluent. The overall change (between initial and day 7) in chlorophyll “a” concentration was highest in the control pond (36.2%) and decreased with increasing effluent concentration (1% to 20%) from 21.7% to -9.4%. On the other hand, algal growth under ceramic effluent treatment was comparable with that observed in the control pond.展开更多
基金supported by the Hundred Talents Program of Chinese Academy of Sciencesthe National Natural Science Fundation of China for Distinguished Young Scholar(10825211)
文摘Based on the remote sensing images of algae, the present work analyzes the horizontal distribution characteristics of algal blooms in Chaohu Lake, China, which also reveals the frequency of algal blooms under different wind directions. Further, an unstructured-grid, three-dimensional finite-volume coastal ocean model （FVCOM） is applied to investigate the wind-induced currents and the transport pro- cess to explain the reason why algal blooms occur at the detected places. We first deduce the primary distribution of biomass from overlaid satellite images, and explain the formation mechanism by analyzing the pollution sources, and simulating the flow field and transportation process under prevailing wind over Chaohu Lake. And then, we consider the adjustment action of the wind on the corresponding day and develop a two-time scale approach to describe the whole formation process of algae horizontal distribution in Chaohu Lake. That is, on the longer time scale, i.e., during bloom season, prevailing wind determines the primary distribution of biomass by inducing the characteristic flow field; on the shorter time scale, i.e., on the day when bloom occurs, the wind force adjusts the primary distribution of biomass to form the final distribution of algal bloom.
文摘In order to protect the city of New Orleans from the Mississippi River flooding, the Bonnet Carré Spillway (BCS) was constructed from 1929 to 1936 to divert flood water from the river into Lake Pontchartrain and then into the Gulf of Mexico. During the BCS opening for flood release, large amounts of freshwater, nutrients, sediment, etc. were discharged into Lake Pontchartrain, and caused a lot of environmental problems. To evaluate the environmental impacts of the flood water on lake ecosystems, a two-dimensional numerical model was developed based on CCHE2D and applied to simulate the flow circulation, sediment transport and algal biomass distribution in Lake Pontchartrain. The effect of sediment concentration on the growth of algae was considered in the model. The numerical model was calibrated using field measured data provided by USGS, and then it was validated by the BCS Opening Event in 1997. The simulated results were generally in good agreement with filed data and satellite imagery. The field observation and numerical model show that during the spillway opening for flood release, the sediment concentration is very high, which greatly restricts the growth of algae, so there is no algal bloom observed in the lake. After the closure of BCS, the sediment concentration in the lake reduces gradually, and the nutrient concentration of the lake is still high. Under these conditions, numerical results and satellite imagery showed that the chlorophyll concentration was high and algal bloom might occur.
文摘水生植被和藻类作为湖泊生态系统的主要初级生产者,对湖泊生态系统具有重要作用。在气候变化和人类活动的双重作用下,湖泊富营养化加剧,水生植被退化,藻类水华频发。开展湖泊水生植被群落和藻类水华的长期观测可为湖泊生态系统水生植被修复和藻类水华管控提供决策依据。本研究以太湖流域浅水湖泊长荡湖为研究区,基于1985-2021年的Landsat 5和8卫星数据,利用VBI(vegetation and bloom indices)草藻分类算法,开展了浮叶/挺水植被、沉水植被和藻类水华长时序时空演变分析。结果表明:36年来,长荡湖水生植被(包括浮叶/挺水植被和沉水植被)都呈现显著下降趋势,其中沉水植被下降趋势尤为明显,沉水植被从湖中心向岸边逐步退化,其覆盖度从1985年的75%下降至2021年的不足21%;自2011年起,长荡湖水生植被优势生活型从沉水植被转变为浮叶/挺水植被;2010年首次监测到水华发生,2020年和2021年连续两年均监测到湖中心有大面积水华。基于湖泊围网面积和气象数据分析发现,围网拆除是水生植被退化和优势生活型转变的主要因素。
基金Supported by the RFBR(Nos.16-05-00548-a,16-05-00502-a)
文摘An unusual feature of the saline stratified lakes that were formed due to ongoing postglacial uplift on the White Sea coast is the presence of several differently colored thin layers in the zone with sharp gradients. Colored layers in five lakes at various stages of separation from the sea were investigated using optical microscopy, spectrophotometry, spectrofluorimetry, and photobiology. The upper greenish colored layer located in the aerobic strata of all lakes near the compensation depth of 1% light penetration contains green algae. In the chemocline, another layer, brightly green, red or pink, is dominated by mixotrophic flagellates. Despite the very low light intensities and the presence of H 2 S, active photosynthesis by these algae appears to be occurring, as indicated by high values of the maximum quantum yield of primary photochemistry, electron transport activity, photosynthetic activity of photosystem II, the fraction of active centers, and low values of heat dissipation. In the reduced zone of the chemocline, a dense green or brown suspension of anoxygenic phototrophs(green sulfur bacteria) is located.
文摘Harmful algal blooms (HABs) in freshwater ecosystems, especially of cyanobacterial species, are becoming more frequent and expanding geographically, including in Lake Erie in North America. HABs are the result of complex and synergistic environmental factors, though N or P eutrophication is a leading cause. With global mean temperatures expected to increase an additional 2°C - 5°C by 2100, cyanobacterial blooms are predicted to increase even more, given their typically-high temperature optimum for growth. We investigated how increases in temperature and nitrogen, singly or in combination, affect the growth, food quality, and herbivory of Lake Erie cyanobacteria. Algal community samples collected from Lake Erie, and isolated non-N-fixing (Microcystis aeruginosa) and N-fixing (Anabaena flos-aquae) cyanobacterial species, were cultured at 20°C, 25°C, or 30°C, and at 5, 50, 150, or 250 μM N, and then analyzed for growth and (for isolates) content of total protein and non-structural carbohydrates (NSC). Temperature and N both affected algal growth, and there were temperature × N interactions, which were sometimes affected by presence/absence of zooplankton. For example, cyanobacteria (but not green algae) growth increased with both temperature and N, especially from 25°C to 30°C, but N and herbivore presence increased cyanobacterial growth primarily only at 30°C. In general, temperature and N had little consistent effect on NSC, but increasing temperature and N tended to increase protein content in Microcystis and Anabaena (temperature effects mostly at higher N levels). In Anabaena, increases in N did not increase growth or protein at 20°C or 25°C, but did increase both at 30°C, indicating that N fixation is damaged at high temperatures and that high NO3 can overcome this damage. These results indicate that future global warming and continued eutrophication will increase cyanobacterial growth, as well influence algal herbivory and competition between N-fixing and non-N-fixing cyanobacteria.
文摘Carbon resources play an important role in affecting the benthic bacterial community in shallow lakes. In this study, pyrosequencing was applied to compare bacteria phylogenic profile in incubated sediments with normal and exchanged organic detritus in macrophyte-dominated East Lake Taihu and algal-dominated Meiliang Bay. We observed significant bacteria species variations in sediments from two bays, regardless of treatments. RDA (Redundancy Analysis) analysis showed that sediment characteristics, especially concentrations of total nitrogen might account for this differentiation. Besides, algal-dominated Meiliang Bay sediment with addition of Vallisneria detritus exhibited higher bacterial species variations than the sediment amended with Microcystis detritus. To the contrary, sediments from macrophyte-dominated East Lake Taihu shared similar bacteria profile at all taxonomic levels and grouped together in MDS (multidimensional scaling) plots over the treatments with Vallisneria or Microcystis detritus addition into the sediment. We speculated that the different degradability of macrophyte detritus and algal detritus led to varied bacterial responses to exchanged organic resources and ultimately, the amounts, nutrient availability and degradability of organic resources may be main reasons for benthic bacteria community structure differentiation between the two states in shallow lakes.
文摘Exposure to microcystin poses a potential health hazard to humans and other living organisms. This results from eutrophication and warrants an investigation into the problem of microcystin toxicity in Lake Victoria. This study was conducted in Homa Bay, Kisumu, Siaya and Busia counties to understand the effects of microcystin toxicity among fisherfolk and lake riparian communities. Data collection involved 90 semi-structured questionnaires, 11 key informant interviews and seven focus group discussions. Water samples were also collected and analysed for algal toxins. Data were analysed using Stata version 13 (Stata Corp, College Station, Texas, USA) and SPSS version 18.0. Majority (73.3%) of the fisherfolk were aware of microcystin toxicity in the lake with no significant difference in the awareness of microcystin toxicity between men and women (χ<sup>2</sup> = 1.1, df = 1, p = 0.293). Most of the respondents relied on lake (48.9%) and tap water (47.8%) with paltry sourcing water from borehole (16.8%) and rain (7.8%). There was no association between level of education and water source (lake;χ<sup>2</sup> = 1.61, df = 3, p = 0.656) and (tap;χ<sup>2</sup> = 2.23, df = 3, p = 0.527). Fisherfolk was cognizant of the need to curb microcystin toxicity. There was a significant difference (p < 0.05) in the occurrence of microcystin during the wet season compared to the dry season. Cyanophytes were the most significant (p < 0.001) group of phytoplankton. When ingested, microcystin has a long-term effect and therefore pollution control is crucial.
文摘Growing trends in industrialization in Ethiopia have raised concerns about pollution of water bodies particularly of lakes. This study was therefore conducted to 1) characterize the chemical contents of major industrial effluents (namely textile ceramic and soft drink factories) that reached Lake Hawassa and 2) investigate the effects of the above mentioned factory effluents on survival of larvae fish and growth of algae. Effluent samples were collected from the outlet lagoons of each factory in December, 2009. Then, effluent samples were analyzed for total N, NO3-N, NH4-N, S2-, , , COD, total dissolved solids (TDS) and heavy metals at the federal Environmental Protection Agency (EPA) Laboratory, Addis Ababa. The experiments on the impact of effluents on survival of fish larvae and growth of algae were conducted using six concrete paved ponds (with different concentration of effluent). The results of chemical analysis showed that textile effluent had high COD (nearly 3 times higher), TDS (19 times higher) as well as (39 times higher) than the maximum permissible limits (MPL) set by Environmental Protection Authority (EPA). Among heavy metals, Zn and Fe of textile effluent were much higher (41 and 1.5 times higher, respectively) than the MPL set by EPA. Ceramic effluent also contained high concentration of (24.5 times), S2-, (2 times) and Zn (14 times) exceeding the limit of EPA. Regarding soft drink factory, high values of COD, and Zn were found in the effluent than the limit specified by EPA. The biological treatment lagoons of the respective source were not effective since the effluents were taken from the last treatment lagoon (outlet lagoon) and some of the measured parameters were higher than MPL. Results of the pond experiment showed that 5%, 10% and 20% concentration levels of the HTF effluent killed significantly high proportion of the fry (65%, 86.8% and 88.7%, respectively). In contrast, fry mortality in ceramic and soft drink effluent treatments, even at 10 and 20% concentration levels, stayed nearly below 10%, which were not far off from the mortality of the control groups. Algal biomass in the treated ponds varied with the type of effluent treatment and concentration level. Compared with the first day, chlorophyll “a” concentration measured on the 7th day had increased by 51%, 48%, 74%, 27% and 31% at 0%, 1%, 5%, 10% and 20% concentrations, respectively of textile effluent. The 5% treatment level of textile effluent caused the highest rate of algal growth above the growth rate observed in the control pond, but further increased in concentration to 10% and 20% resulted in a lower growth of algae than in the control pond. Therefore, textile effluent may boost up algae growth at lower concentrations (~5%) but at higher concentration levels its toxic effect may become inhibitory. Regarding the effluent of soft drink factory, algal growth progressively diminished with increasing concentration of the effluent. The overall change (between initial and day 7) in chlorophyll “a” concentration was highest in the control pond (36.2%) and decreased with increasing effluent concentration (1% to 20%) from 21.7% to -9.4%. On the other hand, algal growth under ceramic effluent treatment was comparable with that observed in the control pond.
