The Niyang River, a main tributary of the Yarlung Zangbo River, is an important and typical plateau fiver ecosystem in Tibet, China. At present, few studies have focused on its aquatic living resources and fiver ecolo...The Niyang River, a main tributary of the Yarlung Zangbo River, is an important and typical plateau fiver ecosystem in Tibet, China. At present, few studies have focused on its aquatic living resources and fiver ecology. In this study, the composition, abundance, and diversity of periphytic protozoa were investigated across four seasons from 2008 to 2009 to better understand their spatio-temporal patterns and relationship to the environment. Our investigation shows that periphytic protozoa in the Niyang River contained 15 genera, belonged to Tubulinea, Alveolata, Discosea and Rhizaria, Alveolata possessed most genera, up to nine, with highest share in abundance, exceeding 50%, Difflugia and Glaucoma were dominant genera. Moreover, four diversity indices of periphytic protozoa, including species richness, total abundance, Shannon-Wiener diversity index and Pielou＇s evenness index, displayed a significant descending trend as the seasons continued, in the order of winter, spring, summer and autumn; with a significant difference existing between winter and summer （or autumn） for Shannon-Wiener diversity index and species richness （P〈0.05）. Four of these diversity indices also presented a V-shaped pattern between the upper middle course of the Niyang River and the confluence of the Niyang River and Yarlung Zangbo River, with the lowest value occurred in the middle course of the Niyang River. However, no significant variation was found through the Niyang River （P〉0.05）. In addition, canonical correlation analysis （CCA） shows that the densities of Difflugia, Glaucomais, Enchelydium, Cyphoderia, and Enchelys correlate with water temperature, alkalinity, hardness, pH, and dissolved oxygen, respectively. Lastly, the relationship between periphytic protozoa diversity and the environmental factors of the Niyang River can be predicted using classification and regression trees （CART） annalysis, which suggests that the total abundance and Shannon-Wiener diversity index would be higher when the elevation is above 3 308 m. On the other hand, the Shannon-Wiener diversity index and Pielou＇s evenness index would be lower when pH and ammoniacal nitrogen have lower or higher values. Finally yet importantly, close attention should be paid to periphytic protozoa and its environment to ensure sustainable development of the Niyang River ecosystem.展开更多
On the Morrocan Atlantic coast, the estuary of the Bouregreg was submitted to many anthropic effects. After the dam Sidi Mohammed ben Abdellah was built in 1974, the flow became almost null. The waters of the estuary ...On the Morrocan Atlantic coast, the estuary of the Bouregreg was submitted to many anthropic effects. After the dam Sidi Mohammed ben Abdellah was built in 1974, the flow became almost null. The waters of the estuary are meant for recreational activities, fishing, but at the same time they receive water collecting domestic and industrial wastewater. The waste in old landfills was not treated and leaked into the river water. The matter gets worse with the action of tides which make it difficult to escape the pollution load （physicochemical, bacteriological, heavy metals, etc.）. The concentrations of heavy metals （Pb, Fe, Cu and Cr） recorded in the sediments are higher than those found in the two molluscs. However, we have found out that Mytilus has accumulated more heavy metals （Cr, Pb and Zn） than Solen marginatus. The Zn makes an exception： It presents a greater concentration in the molluscs （63.015 mg/kg dry weight for Mytilus and 232.736 mg/kg dry weigh for Solen） than in the sediments （57.639 mg/kg）. The amount of these metals exceeds the standard values. The impact of the marine pollution on human health derives from the consumption by humans of heavy-metal polluted molluscs. The detected concentrations of these pollutants are superior to the permissible maximum amounts.展开更多
The timing of river entry in the Atlantic salmon is known to depend on genetic, demographic and environmental factors, but little is known about the relative magnitude of among population and among year variation and ...The timing of river entry in the Atlantic salmon is known to depend on genetic, demographic and environmental factors, but little is known about the relative magnitude of among population and among year variation and covariation in this respect in natural state Atlantic salmon rives. To investigate this, variability in the timing of river entry in three historical Finnish Atlantic salmon populations were analyzed using salmon trap data collected during 1870- 1902. The analyses reveled that 1 ） the timing of river entry differed substantially and consistently among the rivers, and that 2） variation among the rivers was much larger than variation among years. Annual variations were not explained by regional environmental conditions, whereas in one river the timing of the local flood peak was a significant predictor of the timing of river entry. Differences in the timing of salmon entry to geographically closely situated rivers suggests that a regionally fixed opening date for coastal fisheries might not be the best management strategy as it may lead to uneven exploitation of salmon populations from different rivers [ Current Zoology 55 （5） ： 342 - 349, 2009] .展开更多
基金Supported by Regional Fund Key Projects from Technology Gallery in Tibet,Agro-Technical Popularization from Finance Department in Tibet,the National Special Research Fund for Non-Profit Sector(Agriculture)(No.201403012)the National Natural Science Foundation of China(No.31560144)the State Key Laboratory of Freshwater Ecology and Biotechnology(No.2011FBZ28)
文摘The Niyang River, a main tributary of the Yarlung Zangbo River, is an important and typical plateau fiver ecosystem in Tibet, China. At present, few studies have focused on its aquatic living resources and fiver ecology. In this study, the composition, abundance, and diversity of periphytic protozoa were investigated across four seasons from 2008 to 2009 to better understand their spatio-temporal patterns and relationship to the environment. Our investigation shows that periphytic protozoa in the Niyang River contained 15 genera, belonged to Tubulinea, Alveolata, Discosea and Rhizaria, Alveolata possessed most genera, up to nine, with highest share in abundance, exceeding 50%, Difflugia and Glaucoma were dominant genera. Moreover, four diversity indices of periphytic protozoa, including species richness, total abundance, Shannon-Wiener diversity index and Pielou＇s evenness index, displayed a significant descending trend as the seasons continued, in the order of winter, spring, summer and autumn; with a significant difference existing between winter and summer （or autumn） for Shannon-Wiener diversity index and species richness （P〈0.05）. Four of these diversity indices also presented a V-shaped pattern between the upper middle course of the Niyang River and the confluence of the Niyang River and Yarlung Zangbo River, with the lowest value occurred in the middle course of the Niyang River. However, no significant variation was found through the Niyang River （P〉0.05）. In addition, canonical correlation analysis （CCA） shows that the densities of Difflugia, Glaucomais, Enchelydium, Cyphoderia, and Enchelys correlate with water temperature, alkalinity, hardness, pH, and dissolved oxygen, respectively. Lastly, the relationship between periphytic protozoa diversity and the environmental factors of the Niyang River can be predicted using classification and regression trees （CART） annalysis, which suggests that the total abundance and Shannon-Wiener diversity index would be higher when the elevation is above 3 308 m. On the other hand, the Shannon-Wiener diversity index and Pielou＇s evenness index would be lower when pH and ammoniacal nitrogen have lower or higher values. Finally yet importantly, close attention should be paid to periphytic protozoa and its environment to ensure sustainable development of the Niyang River ecosystem.
文摘On the Morrocan Atlantic coast, the estuary of the Bouregreg was submitted to many anthropic effects. After the dam Sidi Mohammed ben Abdellah was built in 1974, the flow became almost null. The waters of the estuary are meant for recreational activities, fishing, but at the same time they receive water collecting domestic and industrial wastewater. The waste in old landfills was not treated and leaked into the river water. The matter gets worse with the action of tides which make it difficult to escape the pollution load （physicochemical, bacteriological, heavy metals, etc.）. The concentrations of heavy metals （Pb, Fe, Cu and Cr） recorded in the sediments are higher than those found in the two molluscs. However, we have found out that Mytilus has accumulated more heavy metals （Cr, Pb and Zn） than Solen marginatus. The Zn makes an exception： It presents a greater concentration in the molluscs （63.015 mg/kg dry weight for Mytilus and 232.736 mg/kg dry weigh for Solen） than in the sediments （57.639 mg/kg）. The amount of these metals exceeds the standard values. The impact of the marine pollution on human health derives from the consumption by humans of heavy-metal polluted molluscs. The detected concentrations of these pollutants are superior to the permissible maximum amounts.
基金supported by Academy of Finland and the University of Helsinki
文摘The timing of river entry in the Atlantic salmon is known to depend on genetic, demographic and environmental factors, but little is known about the relative magnitude of among population and among year variation and covariation in this respect in natural state Atlantic salmon rives. To investigate this, variability in the timing of river entry in three historical Finnish Atlantic salmon populations were analyzed using salmon trap data collected during 1870- 1902. The analyses reveled that 1 ） the timing of river entry differed substantially and consistently among the rivers, and that 2） variation among the rivers was much larger than variation among years. Annual variations were not explained by regional environmental conditions, whereas in one river the timing of the local flood peak was a significant predictor of the timing of river entry. Differences in the timing of salmon entry to geographically closely situated rivers suggests that a regionally fixed opening date for coastal fisheries might not be the best management strategy as it may lead to uneven exploitation of salmon populations from different rivers [ Current Zoology 55 （5） ： 342 - 349, 2009] .
