Antarctic continental lakes and ponds are among the most impoverished aquatic environments on earth but many of them support flourishing populations of cyanobacteria,eukaryotic algae,protozoans,and some multicellular ...Antarctic continental lakes and ponds are among the most impoverished aquatic environments on earth but many of them support flourishing populations of cyanobacteria,eukaryotic algae,protozoans,and some multicellular animals.In this study,we present results of a microscopic analysis of cyanobacteria and eukaryotic algae from nine diverse types of Antarctic continental water bodies during one austral summer.The results supplement and enlarge our previous studies on the limnological characteristics of the epiglacial and supraglacial lakes and ponds in Dronning Maud Land,an area that has received little attention from limnologists.The taxon with highest frequency among the samples(n=79)was Mesotaenium cf.berggrenii,a eukaryotic Zygnematophyceae,which occurred in 82%of the samples with a maximum cell density of 68 cells·mL^(-1).The taxa with second and third highest frequency were the prokaryotes Gloeocapsopsis(60%)and Leptolyngbya(41%),followed by Chlamydomonas(34%)and Cyanothece(29%).The number of taxa varied between 7-21 among the lakes and ponds,being highest in a supraglacial lake,and lowest in an epiglacial lake.The results did not reveal any obvious correlation between the abundance of any taxa and the water chemistry,but water bodies with inorganic sediments had higher cell densities and biomasses than those without sediment.This suggests the importance of sediment in supporting biological diversity in these ultraoligotrophic lakes and ponds.展开更多
The surface water quality of some stagnant water bodies (ponds and lakes—Obi Lake, Usede pond, Oguta lake, Omuku pond, Ugheghe pond, Karabodone lake, Abua lake, Ikarama lake, Tenmako lake, and Adiegbe lake) in the Ni...The surface water quality of some stagnant water bodies (ponds and lakes—Obi Lake, Usede pond, Oguta lake, Omuku pond, Ugheghe pond, Karabodone lake, Abua lake, Ikarama lake, Tenmako lake, and Adiegbe lake) in the Niger Delta area of Nigeria have been investigated experimentally by analysing the physico-chemical and biological characteristics of the surface water samples. Results show: pH (5.10 - 7.40), temperature (26.4°C - 31.0°C), turbidity (7.83 - 27.7NTU), electrical conductivity (13.5 - 34.8 μS/cm), biochemical oxygen demand (BOD) (1.07 - 19.5 mg/l), chemical oxygen demand (COD) (1.90 - 21.5 mg/l), suspended solids (SS) (9.70 - 37.3 mg/l), dissolved oxygen (DO) (2.7 - 8.7 mg/l), total dissolved solids (TDS) (33.8 - 187.0 mg/l), total phosphorus (0.73 - 2.47 mg/l), ammoniacal nitrogen (AN) (0.018 - 4.70 mg/l) and total fecal coliform count (TFCC) (nil - 2175 cfu/ml). Results on the water quality using Malaysian Water Quality Index (WQI) show that Usede pond and Obi Lake belong to Class II with values that are 75.24 and 76.73 respectively. The WQI of Oguta lake, Omuku pond, Ugheghe pond, Karabodone lake and Abua lake are 67.46, 65.64, 65.87, 50.77, and 67.01 respectively and belongs to class III. The WQI of Ikarama lake, Tenmako lake, and Adiegbe lake are 43.38, 37.60, and 41.40, respectively and belongs to class IV and is described as fair.展开更多
Permafrost thickness under identical climates in cold regions can vary significantly because it is severely affected by climate change, topography, soil physical and thermal properties, and geothermal conditions. This...Permafrost thickness under identical climates in cold regions can vary significantly because it is severely affected by climate change, topography, soil physical and thermal properties, and geothermal conditions. This study numerically in- vestigates the response of ground thermal regime and talik development processes to permafrost with different thicknesses under a thermokarst lake on the Qinghai-Tibet Plateau. On the basis of observed data and information from a representative monitored lake in the Beiluhe Basin, we used a heat transfer model with phase change under a cylindrical coordinate system to conduct three simulation cases with permafrost thicknesses of 45 m, 60 m, and 75 m, respectively. The simulated results indicate that increases in permafrost thickness not only strongly retarded the open talik formation time, but also delayed the permafrost lateral thaw process after the formation of open talik. Increasing the permafrost thickness by 33.3% and 66.7% led to open talik formation time increases of 83.66% and 207.43%, respectively, and resulted in increases in the lateral thaw duration of permafrost under the modeled thermokarst lake by 28.86% and 46.54%, respectively, after the formation of the open taliks.展开更多
On the northern coast of the Cape Verde peninsula, Lake Retba is one of the few depressions that have preserved its water body due to the drought that plagued the Sahel in the 1960s. The aim of this article is to unde...On the northern coast of the Cape Verde peninsula, Lake Retba is one of the few depressions that have preserved its water body due to the drought that plagued the Sahel in the 1960s. The aim of this article is to understand the resilience of the lake to the drought. For this purpose, a deep knowledge of interactions between the different components of the hydro-system, namely: lake, dune tablecloth, ponds and ocean is necessary. The use of electrical resistivity tomography (ETR) and chemical and isotopic tools yielded conclusive results. Electrical tomography of resistivity (ETR) shows throughout the coastal dune a superposition between fresh and salt water, with even a predominance of salt water at the level of the old canal. The chemistry of the major ions and isotopes confirms this contact between the saltwater bison of the sea and the lake by showing a superposition of the fresh/brackish waters on the salty waters of the bevel, which, in turn, are found in the very salty waters influenced by the lake. This translates a feeding of the lake by the sea through the bevel. At the canal level, this feeding is done, on the surface, by means of ponds whose water characteristics show that they constitute an outcrop of the bevel. The freshwater body of the coastal dune that floats on salt water in the form of a lens also flows into the lake. The feeding of the lake, by the sea through the bevel and the ponds, and by the water table, is therefore effective and attested by all the methods used in this work. It allowed the resilience of the lake against the drought. This inflow of seawater into the lake is at the origin of its salinization and therefore of the salt that settles on the bottom. This study shows that the survival of the lake also depends on safeguarding the ponds located in the north of the lake.展开更多
Understanding lake ice growth and its sensitivity to climate change is vital to understand the thermal regime of thaw lake systems and predict their response to climate change. In this paper, a physically-based, two-d...Understanding lake ice growth and its sensitivity to climate change is vital to understand the thermal regime of thaw lake systems and predict their response to climate change. In this paper, a physically-based, two-dimensional, non-steady mathematical model is developed for studying the role of shallow tundra lakes in the Alaskan Arctic. Both the radiation absorption in lake water and the phase change in permafrost are considerd in the model. The materials the model includes are snow, ice, water, unfrozen and frozen soil (peat, silt, sand and gravel). The basic inputs to the model observed mean daily air temperature and snow depth. The ability of this model to simulate lake ice growth and thickness variation, lake water temperature distribution, the thermal regime of permafrost and talik dynamics beneath lakes, and thawing rate of permafrost below and adjacent to shallow thaw lakes offers the potential to describe the effects of climate change in the Alaskan Arctic.展开更多
The carbon isotopic composition of organic matter （δ^13Corg） was determined in two sediment cores （IIL1 and IIL9） recovered from Inexpressible Island, Ross Sea, Antarctica, and analyzed to identify the sources of...The carbon isotopic composition of organic matter （δ^13Corg） was determined in two sediment cores （IIL1 and IIL9） recovered from Inexpressible Island, Ross Sea, Antarctica, and analyzed to identify the sources of that organic matter. The δ^13Corg values of sediments of IIL9 were found to vary between -14.6‰ and -11.6‰, with a mean of-13.4‰ （n=48）. These values were significantly higher than those of IIL1 sediments which varied between -23.2‰ and -20.4‰, with a mean of-21.8%o （n=55）. The variation in δ^13Corg values in these two sediment cores indicate different sources of organic matter, The relatively high 6~3Corg values in IIL9 are in accordance with a source from algae, while the low δ^13Corg values in IIL1 evince significant influence from penguin guano with algae as the secondary source. Compared with the reference data from other high-latitude lake sediments and plants, the δ^13Corg values in IIL9 were extremely high, a result likely related to intense competition for CO2 assimilation among algal species during the growing season in this relatively shallow pond. These results indicate that sedimentary δ^13Corg is a reliable proxy for paleo-primary productivity in ponds at Inexpressible Island.展开更多
Climate warming rates in the Arctic are far greater than the global average,exerting stronger impacts on permafrost degradation and thermokarst landform development.Thermokarst lakes and ponds(TLPs),which are widely d...Climate warming rates in the Arctic are far greater than the global average,exerting stronger impacts on permafrost degradation and thermokarst landform development.Thermokarst lakes and ponds(TLPs),which are widely distributed in the Lena Basin in the Russian Arctic,play a vital role in altering local ecosystem.However,the detailed distribution of TLPs in the Lena Basin still remains poorly known.In this study,we built the first 10 m resolution TLP dataset for the Lena Basin in the 2020 thawing season by utilizing 4902 Sentinel-2 images.A robust mapping workflow was developed and implemented in the Google Earth Engine(GEE)platform.The accu-racy assessment demonstrates a satisfactory accuracy(93.63%),and our results exhibit a better consistency with real TLPs than global water body products.A total of 380,477 TLPs(~0.53%of the total surface area of the Lena Basin)were identified,showing an uneven distribution in the five sub-basins.The TLPs were found to be mainly located within plain areas,with an active layer thickness in the range of 80-100 cm.The higher ground ice content and mean annual ground temperature were favorable for TLP development.This dataset will be valuable for investigating the complex interac-tion between TLPs and permafrost.It will also serve as a baseline product for better incorporating thermokarst processes into perma-frostclimate models.展开更多
Objective:To determine the occurrence of Cryptosporidium species in catfish(Clarias gariepinus)harvested from two lakes and ponds in Zaria,Kaduna State,Nigeria.Methods:Catfish samples(n=200)from two lakes and(n=200)fr...Objective:To determine the occurrence of Cryptosporidium species in catfish(Clarias gariepinus)harvested from two lakes and ponds in Zaria,Kaduna State,Nigeria.Methods:Catfish samples(n=200)from two lakes and(n=200)from two private fish ponds were collected and their gills and gastrointestinal tract samples were analysed for Cryptosporidium oocysts using modified Ziehl-Neelsen staining technique was used,followed by microscopy.Results:Oocysts of Cryptosporidium species were found in all the sampling sites with an overall positivity rate of 49.75%.A comparison between the lakes and ponds as sampling sites revealed a statistically significant(P<0.05)higher percentage of occurrence of Cryptosporidium oocyst from the lakes(39.25%)than from the ponds(10.50%).Conclusions:These findings document for the first time the natural occurrence ofCryptosporidium sp.in catfish intended for human consumption and therefore,underlines the need for public enlightenment to guard against any possible zoonotic transmission.展开更多
The Japanese pond smelt (Hypomesus nipponensis) stock has been observed to fluctuate quite rigorously over the years with sustained periods of low catch in Lake Kasumigaura and Kitaura of the Ibaraki prefecture, Japan...The Japanese pond smelt (Hypomesus nipponensis) stock has been observed to fluctuate quite rigorously over the years with sustained periods of low catch in Lake Kasumigaura and Kitaura of the Ibaraki prefecture, Japan which would adversely affect the socioeconomic livelihood of the local fishermen and fisheries industry. This study was aimed at determining the factors affecting the stock fluctuation of the pond smelt through the different years in the two lakes. Through exploratory analysis it was found that the pond smelt had significant relationship with total phosphorus (TP) level in both lakes. The global mean land and ocean temperature index (LOTI) was also found to be indirectly related to the pond smelt stock in lake Kasumigaura and Kitaura at the latitude band of 24°N to 90°N (l). Both TP and LOTI had inverse relationship with pond smelt trajectory in both lakes. For both Lake Kasumigaura and Kitaura, TP for the individual lakes and LOTI (l) were used as independent variables using generalized linear model and response surface methods for modeling the stock dynamics of the pond smelt in the two lakes. Model selection was based on significant parameter estimates (p < 0.05), Akaikes Information Criterion and R2 values. Phosphorus loading is an indication of increasing anthropogenic activities in the surrounding area having negative impact on the pond smelt population. When management decisions are being made regarding pond smelt fishery and sustainability plans in the Ibaraki prefecture, the effects of TP and LOTI should be taken into account. Future research needs to be directed towards deeper understanding the mechanisms by which TP and LOTI affect pond smelt population in Lake Kasumigaura and Kitaura for more effective management.展开更多
Objective:To evaluate the difference in physico-chemical characteristics,composition and abundance of plankton communities owing to the supplementary feed added in fish ponds as compared to Lake Tana.Methods:Physico-c...Objective:To evaluate the difference in physico-chemical characteristics,composition and abundance of plankton communities owing to the supplementary feed added in fish ponds as compared to Lake Tana.Methods:Physico-chemical and biological data of plankton were collected from 3 studied sites from November 2008 to October 2009.Data were compared using One-way ANOVA to see the difference among sites.Diversity indices such as Margalef's index,Shannon-Wiener index,and evenness index were employed to describe the distribution of plankton community among the studied sites.Results:The pH value was remarkably higher in ponds water.However,conductivity and total dissolved solids were the highest in lake water.Nitrate concentration was relatively high in ponds.Zooplankton species richness was higher in lake water than ponds.The lake also had the highest mean value of both Shannon-Wiener index and evenness index in phytoplankton.Conclusions:The results revealed that the supplementary feed added to each pond had influence on nutrient content which enhanced algal biomass and productivity of the ponds.However,the pond water has to be regularly refreshed to control eutrophication.展开更多
基金supported by AF-NSFC mobility program from the Academy of Finland(Grant no.333170)National Natural Science Foundation of China(Grant no.52211530038).
文摘Antarctic continental lakes and ponds are among the most impoverished aquatic environments on earth but many of them support flourishing populations of cyanobacteria,eukaryotic algae,protozoans,and some multicellular animals.In this study,we present results of a microscopic analysis of cyanobacteria and eukaryotic algae from nine diverse types of Antarctic continental water bodies during one austral summer.The results supplement and enlarge our previous studies on the limnological characteristics of the epiglacial and supraglacial lakes and ponds in Dronning Maud Land,an area that has received little attention from limnologists.The taxon with highest frequency among the samples(n=79)was Mesotaenium cf.berggrenii,a eukaryotic Zygnematophyceae,which occurred in 82%of the samples with a maximum cell density of 68 cells·mL^(-1).The taxa with second and third highest frequency were the prokaryotes Gloeocapsopsis(60%)and Leptolyngbya(41%),followed by Chlamydomonas(34%)and Cyanothece(29%).The number of taxa varied between 7-21 among the lakes and ponds,being highest in a supraglacial lake,and lowest in an epiglacial lake.The results did not reveal any obvious correlation between the abundance of any taxa and the water chemistry,but water bodies with inorganic sediments had higher cell densities and biomasses than those without sediment.This suggests the importance of sediment in supporting biological diversity in these ultraoligotrophic lakes and ponds.
文摘The surface water quality of some stagnant water bodies (ponds and lakes—Obi Lake, Usede pond, Oguta lake, Omuku pond, Ugheghe pond, Karabodone lake, Abua lake, Ikarama lake, Tenmako lake, and Adiegbe lake) in the Niger Delta area of Nigeria have been investigated experimentally by analysing the physico-chemical and biological characteristics of the surface water samples. Results show: pH (5.10 - 7.40), temperature (26.4°C - 31.0°C), turbidity (7.83 - 27.7NTU), electrical conductivity (13.5 - 34.8 μS/cm), biochemical oxygen demand (BOD) (1.07 - 19.5 mg/l), chemical oxygen demand (COD) (1.90 - 21.5 mg/l), suspended solids (SS) (9.70 - 37.3 mg/l), dissolved oxygen (DO) (2.7 - 8.7 mg/l), total dissolved solids (TDS) (33.8 - 187.0 mg/l), total phosphorus (0.73 - 2.47 mg/l), ammoniacal nitrogen (AN) (0.018 - 4.70 mg/l) and total fecal coliform count (TFCC) (nil - 2175 cfu/ml). Results on the water quality using Malaysian Water Quality Index (WQI) show that Usede pond and Obi Lake belong to Class II with values that are 75.24 and 76.73 respectively. The WQI of Oguta lake, Omuku pond, Ugheghe pond, Karabodone lake and Abua lake are 67.46, 65.64, 65.87, 50.77, and 67.01 respectively and belongs to class III. The WQI of Ikarama lake, Tenmako lake, and Adiegbe lake are 43.38, 37.60, and 41.40, respectively and belongs to class IV and is described as fair.
基金supported by the National Natural Science Foundation of China (NSFC) (No.41271076)the National Key Basic Research Program of China (No.2010CB951402)the Open Fund Project of the Institute of Plateau Meteorology, China Meteorological Administration (No.LPM2008019)
文摘Permafrost thickness under identical climates in cold regions can vary significantly because it is severely affected by climate change, topography, soil physical and thermal properties, and geothermal conditions. This study numerically in- vestigates the response of ground thermal regime and talik development processes to permafrost with different thicknesses under a thermokarst lake on the Qinghai-Tibet Plateau. On the basis of observed data and information from a representative monitored lake in the Beiluhe Basin, we used a heat transfer model with phase change under a cylindrical coordinate system to conduct three simulation cases with permafrost thicknesses of 45 m, 60 m, and 75 m, respectively. The simulated results indicate that increases in permafrost thickness not only strongly retarded the open talik formation time, but also delayed the permafrost lateral thaw process after the formation of open talik. Increasing the permafrost thickness by 33.3% and 66.7% led to open talik formation time increases of 83.66% and 207.43%, respectively, and resulted in increases in the lateral thaw duration of permafrost under the modeled thermokarst lake by 28.86% and 46.54%, respectively, after the formation of the open taliks.
文摘On the northern coast of the Cape Verde peninsula, Lake Retba is one of the few depressions that have preserved its water body due to the drought that plagued the Sahel in the 1960s. The aim of this article is to understand the resilience of the lake to the drought. For this purpose, a deep knowledge of interactions between the different components of the hydro-system, namely: lake, dune tablecloth, ponds and ocean is necessary. The use of electrical resistivity tomography (ETR) and chemical and isotopic tools yielded conclusive results. Electrical tomography of resistivity (ETR) shows throughout the coastal dune a superposition between fresh and salt water, with even a predominance of salt water at the level of the old canal. The chemistry of the major ions and isotopes confirms this contact between the saltwater bison of the sea and the lake by showing a superposition of the fresh/brackish waters on the salty waters of the bevel, which, in turn, are found in the very salty waters influenced by the lake. This translates a feeding of the lake by the sea through the bevel. At the canal level, this feeding is done, on the surface, by means of ponds whose water characteristics show that they constitute an outcrop of the bevel. The freshwater body of the coastal dune that floats on salt water in the form of a lens also flows into the lake. The feeding of the lake, by the sea through the bevel and the ponds, and by the water table, is therefore effective and attested by all the methods used in this work. It allowed the resilience of the lake against the drought. This inflow of seawater into the lake is at the origin of its salinization and therefore of the salt that settles on the bottom. This study shows that the survival of the lake also depends on safeguarding the ponds located in the north of the lake.
基金US National Science Foundation through the NSP OPP-9907541 and China Postdlctoral Science Foundation
文摘Understanding lake ice growth and its sensitivity to climate change is vital to understand the thermal regime of thaw lake systems and predict their response to climate change. In this paper, a physically-based, two-dimensional, non-steady mathematical model is developed for studying the role of shallow tundra lakes in the Alaskan Arctic. Both the radiation absorption in lake water and the phase change in permafrost are considerd in the model. The materials the model includes are snow, ice, water, unfrozen and frozen soil (peat, silt, sand and gravel). The basic inputs to the model observed mean daily air temperature and snow depth. The ability of this model to simulate lake ice growth and thickness variation, lake water temperature distribution, the thermal regime of permafrost and talik dynamics beneath lakes, and thawing rate of permafrost below and adjacent to shallow thaw lakes offers the potential to describe the effects of climate change in the Alaskan Arctic.
基金the Chinese Arctic and Antarctic Administration of the State Oceanic Administration for project supportthe United States Antarctic Program (USAP)+2 种基金Antarctic Support Contract and Italian Mario Zucchelli Station for logistical support. R. Murray and A. Mc Kenzie provided valuable assistance in the fieldsupported by the National Natural Science Foundation of China (Grant nos. 41576183 and 41376124)National Science Foundation (Grant no. ANT 0739575)
文摘The carbon isotopic composition of organic matter （δ^13Corg） was determined in two sediment cores （IIL1 and IIL9） recovered from Inexpressible Island, Ross Sea, Antarctica, and analyzed to identify the sources of that organic matter. The δ^13Corg values of sediments of IIL9 were found to vary between -14.6‰ and -11.6‰, with a mean of-13.4‰ （n=48）. These values were significantly higher than those of IIL1 sediments which varied between -23.2‰ and -20.4‰, with a mean of-21.8%o （n=55）. The variation in δ^13Corg values in these two sediment cores indicate different sources of organic matter, The relatively high 6~3Corg values in IIL9 are in accordance with a source from algae, while the low δ^13Corg values in IIL1 evince significant influence from penguin guano with algae as the secondary source. Compared with the reference data from other high-latitude lake sediments and plants, the δ^13Corg values in IIL9 were extremely high, a result likely related to intense competition for CO2 assimilation among algal species during the growing season in this relatively shallow pond. These results indicate that sedimentary δ^13Corg is a reliable proxy for paleo-primary productivity in ponds at Inexpressible Island.
基金supported by the National Science Fund for Distinguished Young Scholars[41925027].
文摘Climate warming rates in the Arctic are far greater than the global average,exerting stronger impacts on permafrost degradation and thermokarst landform development.Thermokarst lakes and ponds(TLPs),which are widely distributed in the Lena Basin in the Russian Arctic,play a vital role in altering local ecosystem.However,the detailed distribution of TLPs in the Lena Basin still remains poorly known.In this study,we built the first 10 m resolution TLP dataset for the Lena Basin in the 2020 thawing season by utilizing 4902 Sentinel-2 images.A robust mapping workflow was developed and implemented in the Google Earth Engine(GEE)platform.The accu-racy assessment demonstrates a satisfactory accuracy(93.63%),and our results exhibit a better consistency with real TLPs than global water body products.A total of 380,477 TLPs(~0.53%of the total surface area of the Lena Basin)were identified,showing an uneven distribution in the five sub-basins.The TLPs were found to be mainly located within plain areas,with an active layer thickness in the range of 80-100 cm.The higher ground ice content and mean annual ground temperature were favorable for TLP development.This dataset will be valuable for investigating the complex interac-tion between TLPs and permafrost.It will also serve as a baseline product for better incorporating thermokarst processes into perma-frostclimate models.
基金Supported by Ahmadu Bello University,Zaria,Nigeria with Grant No.ABU/P16945.
文摘Objective:To determine the occurrence of Cryptosporidium species in catfish(Clarias gariepinus)harvested from two lakes and ponds in Zaria,Kaduna State,Nigeria.Methods:Catfish samples(n=200)from two lakes and(n=200)from two private fish ponds were collected and their gills and gastrointestinal tract samples were analysed for Cryptosporidium oocysts using modified Ziehl-Neelsen staining technique was used,followed by microscopy.Results:Oocysts of Cryptosporidium species were found in all the sampling sites with an overall positivity rate of 49.75%.A comparison between the lakes and ponds as sampling sites revealed a statistically significant(P<0.05)higher percentage of occurrence of Cryptosporidium oocyst from the lakes(39.25%)than from the ponds(10.50%).Conclusions:These findings document for the first time the natural occurrence ofCryptosporidium sp.in catfish intended for human consumption and therefore,underlines the need for public enlightenment to guard against any possible zoonotic transmission.
文摘The Japanese pond smelt (Hypomesus nipponensis) stock has been observed to fluctuate quite rigorously over the years with sustained periods of low catch in Lake Kasumigaura and Kitaura of the Ibaraki prefecture, Japan which would adversely affect the socioeconomic livelihood of the local fishermen and fisheries industry. This study was aimed at determining the factors affecting the stock fluctuation of the pond smelt through the different years in the two lakes. Through exploratory analysis it was found that the pond smelt had significant relationship with total phosphorus (TP) level in both lakes. The global mean land and ocean temperature index (LOTI) was also found to be indirectly related to the pond smelt stock in lake Kasumigaura and Kitaura at the latitude band of 24°N to 90°N (l). Both TP and LOTI had inverse relationship with pond smelt trajectory in both lakes. For both Lake Kasumigaura and Kitaura, TP for the individual lakes and LOTI (l) were used as independent variables using generalized linear model and response surface methods for modeling the stock dynamics of the pond smelt in the two lakes. Model selection was based on significant parameter estimates (p < 0.05), Akaikes Information Criterion and R2 values. Phosphorus loading is an indication of increasing anthropogenic activities in the surrounding area having negative impact on the pond smelt population. When management decisions are being made regarding pond smelt fishery and sustainability plans in the Ibaraki prefecture, the effects of TP and LOTI should be taken into account. Future research needs to be directed towards deeper understanding the mechanisms by which TP and LOTI affect pond smelt population in Lake Kasumigaura and Kitaura for more effective management.
基金Supported by Amhara Regional Agricultural Research Institute,Host Institute of Bahir Dar Fishery and Other Aquatic Life Research Center(Grant No.10/26/BD/2009).
文摘Objective:To evaluate the difference in physico-chemical characteristics,composition and abundance of plankton communities owing to the supplementary feed added in fish ponds as compared to Lake Tana.Methods:Physico-chemical and biological data of plankton were collected from 3 studied sites from November 2008 to October 2009.Data were compared using One-way ANOVA to see the difference among sites.Diversity indices such as Margalef's index,Shannon-Wiener index,and evenness index were employed to describe the distribution of plankton community among the studied sites.Results:The pH value was remarkably higher in ponds water.However,conductivity and total dissolved solids were the highest in lake water.Nitrate concentration was relatively high in ponds.Zooplankton species richness was higher in lake water than ponds.The lake also had the highest mean value of both Shannon-Wiener index and evenness index in phytoplankton.Conclusions:The results revealed that the supplementary feed added to each pond had influence on nutrient content which enhanced algal biomass and productivity of the ponds.However,the pond water has to be regularly refreshed to control eutrophication.
