Lake Dianchi has undergone accelerated alternations resulting from human activities during the last 50 years, and provides an exceptional example for the study of regime shift in a shallow lake. Focusing on regime shi...Lake Dianchi has undergone accelerated alternations resulting from human activities during the last 50 years, and provides an exceptional example for the study of regime shift in a shallow lake. Focusing on regime shift, we systematically studied and analysed alternations of key components of its ecosystem, including water parameters, phytoplankton and zooplankton biomass, macrophyte composition and fish populations. We found that the shifting course of Lake Dianchi went through three major phases, corresponding to three distinct states: Phase I clean, stable state during the 1950 s; Phase II transitional state during the 1970 s–1980 s; and phase III stable, turbid state since 1993. We analysed all data and samples, identifying the threshold concentrations at which regime shift occurred: total nitrogen(TN) and phosphorus(TP) reaching 1.2 mg/L and 0.13 mg/L, respectively. Results from this study strongly suggest that the increasing input of external nutrients, reclaiming land from the lake and foreign fish invasion were major inducements to the accelerated shift of Lake Dianchi to its turbid, stable state. These findings provide valuable guidelines for potential efforts to reverse this unnatural process in Lake Dianchi. The restoration may need to:(1) thoroughly and accurately identify pollution sources to control and reduce excessive external nutrients flowing into the lake;(2) return reclaimed land to the lake and recover the littoral zone to its natural state to facilitate increased restoration of macrophytes; and(3) strategically adjust fish populations by reducing benthivorous and filter-feeding fish populations that prey on zooplankton, while enlarging zooplankton populations to control phytoplankton biomass.展开更多
34-, 17-, 4-, 1.5-year old natural algal crusts were collected from Shapotou Scientific Station of the Chinese Academy of Sciences, 40-day old field and greenhouse artificial algal crusts were in situ developed in the...34-, 17-, 4-, 1.5-year old natural algal crusts were collected from Shapotou Scientific Station of the Chinese Academy of Sciences, 40-day old field and greenhouse artificial algal crusts were in situ developed in the same sandy soil and the same place (37°27’N, 104°57’E). Their different cohesions both against wind force and pressure were measured respectively by a sandy wind-tunnel experiment and a penetrometer. On the basis of these algal crusts, the cementing mechanism was revealed from many subjects and different levels. The results showed that in the indoor artificial crusts with the weakest cohesion bunchy algal filaments were distributed in the surface of the crusts, produced few extracellular polymers (EPS), the binding capacity of the crusts just accomplished by mechanical bundle of algal filaments. For field crusts, most filaments grew toward the deeper layers of algal crusts, secreted much more EPS, and when organic matter content was more than 2.4 times of chlorophyll a, overmuch organic展开更多
In arid and semiarid areas,water uptake (non-rainfall water) serves as an important water source for plants,biological soil crusts,insects and small animals.In this study,a measurement program was undertaken to invest...In arid and semiarid areas,water uptake (non-rainfall water) serves as an important water source for plants,biological soil crusts,insects and small animals.In this study,a measurement program was undertaken to investigate water uptake and its changes during formation of man-made algal crusts in the Qubqi Desert.In the study region,water uptake from the atmosphere accounted for 25.07%-39.83% of the total water uptake,and was mainly taken up by a water vapor adsorption mechanism;the proportion of water uptake from the soil substrate was much higher (60.17%-74.93%).The formation of crusts promoted water uptake,but the increased uptake did not occur immediately after inoculation or crusts formation.The water taken up from the atmosphere increased significantly from day 15 after inoculation,and the soil water content was markedly enhanced from day 20 after inoculation.It is considered that the growth of algal filaments and their secretions were the main factors increasing the amount of water uptake and water content in the crusts,and these variables increased even during dry periods when some algae are likely to have died.展开更多
Changing the ratio of light-harvesting pigments was regarded as an efficient way to improve the photosyn-thesis rate in microalgae, but the underlying mechanism is still unclear. In the present study, a mutant of Anab...Changing the ratio of light-harvesting pigments was regarded as an efficient way to improve the photosyn-thesis rate in microalgae, but the underlying mechanism is still unclear. In the present study, a mutant of Anabeana simensis (called SP) was selected from retrieved satellite cul-tures. Several parameters related with photosynthesis, such as the growth, photosynthesis rate, the content of photosyn-thetic pigment, low temperature fluorescence spectrum (77K) and electron transport rate, were compared with those of the wild type. It was found that the change in the ratio of light-harvesting pigments in the mutant led to more efficient light energy transfer and usage in mutant than in the wild type. This may be the reason why the mutant had higher photosynthesis and growth rates.展开更多
Microcystins are a kind of cyclic hepatoxins produced by many species of cyanobacteria.Most previous work have been done on the toxic effects of microcystins on animals and plants.However,the reports about the effect ...Microcystins are a kind of cyclic hepatoxins produced by many species of cyanobacteria.Most previous work have been done on the toxic effects of microcystins on animals and plants.However,the reports about the effect of microcystins on microbial cells are very limited.In this work,the permeability of MC-RR on the cell outer membrane of Escherichia coli(E.coli) and Bacillus subtilis(B.subtilis) was discussed.The permeability effect of MC-RR on the cell outer membrane of E.coli and B.subtilis under different concentrations was demonstrated by a rapid and sustained reduction in the A675 values of lysozyme-treated cells.The decrease of the absorbance values showed a time-and dose-effect.The extravasations of protein and carbonhydrate increased with the increment of the treated-concentration of MC-RR.The results showed that MC-RR could increase the permeability of cell outer membranes of E.coli and B.subtilis.The synergistic effects of MC-RR and lysozyme on bacteria indicated that MC-RR might play an ecological role in bacteria in combination with other substances in some aquatic environments.展开更多
基金Supported by the National Key Technology R&D Program of China(No.2011BAC12B01)
文摘Lake Dianchi has undergone accelerated alternations resulting from human activities during the last 50 years, and provides an exceptional example for the study of regime shift in a shallow lake. Focusing on regime shift, we systematically studied and analysed alternations of key components of its ecosystem, including water parameters, phytoplankton and zooplankton biomass, macrophyte composition and fish populations. We found that the shifting course of Lake Dianchi went through three major phases, corresponding to three distinct states: Phase I clean, stable state during the 1950 s; Phase II transitional state during the 1970 s–1980 s; and phase III stable, turbid state since 1993. We analysed all data and samples, identifying the threshold concentrations at which regime shift occurred: total nitrogen(TN) and phosphorus(TP) reaching 1.2 mg/L and 0.13 mg/L, respectively. Results from this study strongly suggest that the increasing input of external nutrients, reclaiming land from the lake and foreign fish invasion were major inducements to the accelerated shift of Lake Dianchi to its turbid, stable state. These findings provide valuable guidelines for potential efforts to reverse this unnatural process in Lake Dianchi. The restoration may need to:(1) thoroughly and accurately identify pollution sources to control and reduce excessive external nutrients flowing into the lake;(2) return reclaimed land to the lake and recover the littoral zone to its natural state to facilitate increased restoration of macrophytes; and(3) strategically adjust fish populations by reducing benthivorous and filter-feeding fish populations that prey on zooplankton, while enlarging zooplankton populations to control phytoplankton biomass.
基金This work was supported by The Key Project of The Chinese Academy of Sciences (Grant No. KZ952-51-207)the National Natural Science Foundation of China (Grant No. 30070154, 30170022) Mid-youth Natural Science Foundation of Gansu (Grant No.YS-011-A25-0
文摘34-, 17-, 4-, 1.5-year old natural algal crusts were collected from Shapotou Scientific Station of the Chinese Academy of Sciences, 40-day old field and greenhouse artificial algal crusts were in situ developed in the same sandy soil and the same place (37°27’N, 104°57’E). Their different cohesions both against wind force and pressure were measured respectively by a sandy wind-tunnel experiment and a penetrometer. On the basis of these algal crusts, the cementing mechanism was revealed from many subjects and different levels. The results showed that in the indoor artificial crusts with the weakest cohesion bunchy algal filaments were distributed in the surface of the crusts, produced few extracellular polymers (EPS), the binding capacity of the crusts just accomplished by mechanical bundle of algal filaments. For field crusts, most filaments grew toward the deeper layers of algal crusts, secreted much more EPS, and when organic matter content was more than 2.4 times of chlorophyll a, overmuch organic
基金supported by the National Natural Science Foundation of China (Grant Nos. 30770395 and 30870470)partly by the Wuhan Science and Technology Bureau and the Inner Mongolia Planning Committee on high-tech industrialization
文摘In arid and semiarid areas,water uptake (non-rainfall water) serves as an important water source for plants,biological soil crusts,insects and small animals.In this study,a measurement program was undertaken to investigate water uptake and its changes during formation of man-made algal crusts in the Qubqi Desert.In the study region,water uptake from the atmosphere accounted for 25.07%-39.83% of the total water uptake,and was mainly taken up by a water vapor adsorption mechanism;the proportion of water uptake from the soil substrate was much higher (60.17%-74.93%).The formation of crusts promoted water uptake,but the increased uptake did not occur immediately after inoculation or crusts formation.The water taken up from the atmosphere increased significantly from day 15 after inoculation,and the soil water content was markedly enhanced from day 20 after inoculation.It is considered that the growth of algal filaments and their secretions were the main factors increasing the amount of water uptake and water content in the crusts,and these variables increased even during dry periods when some algae are likely to have died.
基金The work was supported by the Chinese Academy of Sciences(Grant No.KSCX-SW-322)Project of Chinese Manned Spaceflight.
文摘Changing the ratio of light-harvesting pigments was regarded as an efficient way to improve the photosyn-thesis rate in microalgae, but the underlying mechanism is still unclear. In the present study, a mutant of Anabeana simensis (called SP) was selected from retrieved satellite cul-tures. Several parameters related with photosynthesis, such as the growth, photosynthesis rate, the content of photosyn-thetic pigment, low temperature fluorescence spectrum (77K) and electron transport rate, were compared with those of the wild type. It was found that the change in the ratio of light-harvesting pigments in the mutant led to more efficient light energy transfer and usage in mutant than in the wild type. This may be the reason why the mutant had higher photosynthesis and growth rates.
基金supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (KZCX2-YW-Q07-04)the Foundation of Key Laboratory of Marine Spill Oil Identification and Damage Assessment Technology, SOA (200713)Open Research Fund Program of Shandong Key Laboratory for Eco-Environmental Science of Yellow River Delta, Binzhou China (2007KFJJ04)
文摘Microcystins are a kind of cyclic hepatoxins produced by many species of cyanobacteria.Most previous work have been done on the toxic effects of microcystins on animals and plants.However,the reports about the effect of microcystins on microbial cells are very limited.In this work,the permeability of MC-RR on the cell outer membrane of Escherichia coli(E.coli) and Bacillus subtilis(B.subtilis) was discussed.The permeability effect of MC-RR on the cell outer membrane of E.coli and B.subtilis under different concentrations was demonstrated by a rapid and sustained reduction in the A675 values of lysozyme-treated cells.The decrease of the absorbance values showed a time-and dose-effect.The extravasations of protein and carbonhydrate increased with the increment of the treated-concentration of MC-RR.The results showed that MC-RR could increase the permeability of cell outer membranes of E.coli and B.subtilis.The synergistic effects of MC-RR and lysozyme on bacteria indicated that MC-RR might play an ecological role in bacteria in combination with other substances in some aquatic environments.
