The sergestid shrimp Acetes vulgaris has long been an important fishery species in estuaries and coastal waters along the Pang-Rad River, Rayong province, Thailand. In nature, this shrimp feeds on a wide range of food...The sergestid shrimp Acetes vulgaris has long been an important fishery species in estuaries and coastal waters along the Pang-Rad River, Rayong province, Thailand. In nature, this shrimp feeds on a wide range of food items, such as phytoplankton, zooplankton, algae, plant matter, debris, sand, and mud. The objective of this study was to compare different feeds on growth and survival of A. vulgaris reared in fiberglass tanks containing 70 m<sup>3</sup> of seawater salinity 25 ppt over a period of 70 days. Individual shrimps were fed with four different types of feeds i.e., newly hatched Artemia (Ar), rotifer (Ro), newly hatched Artemia + rotifer (ArRo) and shrimp larvae commercial feed (SF). Results suggested that specific growth rates (both for body weight and body length) of shrimps reared with SF were not significantly different with treatment feed with Ar, ArRo and Ro (p ≥ 0.05). The survival rate of A. vulgaris did not vary significantly (p ≥ 0.05) among the Ar, Ro and ArRo treatments. However, the highest survival rate of shrimp (81.78% ± 3.08%) was observed in SF treatment and the percentage of survival rate was significantly different with treatment feed with Ar, Ro and ArRo (p ≤ 0.05). The findings reflected the ability of Acetes shrimps to consume diverse food types including both live feed and pelleted feed. Insights obtained from this research suggested that artificial feed can be as efficient as live feeds. This new knowledge is a needed addition to a currently lacking knowledge base for aquaculture of this Acetes species.展开更多
Freshwater habitats and organisms are among the most threatened on Earth, and freshwater ecosystems have been subject to large biodiversity losses. We developed a Climate Change Sensitivity （CCS） indicator based on ...Freshwater habitats and organisms are among the most threatened on Earth, and freshwater ecosystems have been subject to large biodiversity losses. We developed a Climate Change Sensitivity （CCS） indicator based on trait information for a selection of stream- and lake-dwelling Ephemeroptera, Plecoptera and Trichoptera taxa. We calculated the CCS scores based on ten species traits identified as sensitive to global climate change. We then assessed climate change sensitivity between the six main ecoregions of Sweden as well as the three Swedish regions based on lilies. This was done using biological data from 1,382 stream and lake sites where we compared large-scale （ecoregional） patterns in climate change sensitivity with potential future exposure of these ecosystems to increased temperatures using ensemble-modelled future changes in air temperature. Current （1961-1990） measured temperature and ensemble-modelled future （2100） temperature showed an increase from the northernmost towards the southern ecoregions, whereas the predicted temperature change increased from south to north. The CCS indicator scores were highest in the two northernmost boreal ecoregions where we also can expect the largest global climate change-induced increase in temperature, indicating an unfortunate congruence of exposure and sensitivity to climate change. These results are of vital importance when planning and implementing management and conservation strategies in freshwater ecosystems, e.g., to mitigate increased temperatures using riparian buffer strips. We conclude that traits information on taxa specialization, e.g., in terms of feeding specialism or taxa having a preference for high altitudes as well as sensitivity to changes in temperature are important when assessing the risk from future global climate change to freshwater ecosystems [Current Zoology 60 （2）： 221-232, 2014].展开更多
Estuarine ecosystems in SE Asia have been poorly studied when compared to other tropical environments. Important gaps exist particularly in the understanding of their biogeochemical function and contribution to global...Estuarine ecosystems in SE Asia have been poorly studied when compared to other tropical environments. Important gaps exist particularly in the understanding of their biogeochemical function and contribution to global change. In this work we looked into N-turnover in the water column and sediments of the Bangpakong estuary（13°N）. A seasonal sampling program was performed along the salinity gradient covering different stretches of the estuary（68 km）.Key physical and chemical characteristics were also monitored in order to unravel possible environmental controls. Results showed the occurrence of active denitrification in sediments（5.7–50.9 nmol N-N2/（cm3·hr））, and water column（3.5–1044 pmol N-N2/（cm3·hr））. No seasonal or spatial variability was detected for denitrification potential in sediment samples. However, in the water column, the denitrification activity peaked during the transition season in the downstream sites coinciding with high turbidity levels. Therefore, in that period of the year, the water column compartment may be an important contributor to nitrate reduction within the estuary. The rather low nitrification rates detected were not always measurable, probably due to the reduced oxygen content and high siltation. This study is one of the few dealing simultaneously with sediments and water column processes in a highly turbid tropical estuary.Therefore, it emerges as a valuable contribution for the understanding of the dynamics of the nitrogen cycle in tropical environments by exploring the role of estuarine N microbial activity in reducing the effects of increased nitrogen loads.展开更多
The devastating 2004 tsunamis that hit the southwestern coast of Thailand pose a serious threat to people along the coastal zone. A major aim for the tsunami hazard prediction is better prediction of the next tsunamis...The devastating 2004 tsunamis that hit the southwestern coast of Thailand pose a serious threat to people along the coastal zone. A major aim for the tsunami hazard prediction is better prediction of the next tsunamis and their impacts. In this paper, we present the first implications of recent slope failure events of the Andaman outer shelf and upper slope based on a new detailed bathymetric data and subbottom profiler records acquired during two cruises of the MASS project in 2006 and 2007. Morphometric analysis reveals a variety of anomalous features,including: three large plateaus surrounded by moats, ruggedness and unevenness of slope morphology, and two translational submarine landslides. Two submarine landslides are studied from the detailed bathymetric data and subbottom profiler record covering the upper slope of the Andaman Sea shelf break within Thai exclusive economic zone. Maximum approximated volumes of both displaced masses are 4.8×10~7 m~3 and 2.2×10~7 m~3.Considering the data, there is no evidence that landslides have been the sources for tsunami hazard potential in recent geological time. These prerequisites will allow better study of slope failure events in the area. Further investigation is required to better understand obvious geotectonic phenomena.展开更多
Amphioxus, Branchiostoma belcheri, a closest relative of vertebrates, is at a high risk of extinction due to a combination of low effective population size, altered native habitats and environmental pollution, yet lit...Amphioxus, Branchiostoma belcheri, a closest relative of vertebrates, is at a high risk of extinction due to a combination of low effective population size, altered native habitats and environmental pollution, yet little is known about cryopreservation of its gametes. This study deals with the cryopreservation of amphioxus senlen. The main findings are that （1） the extender of Yao et al. is the best one among the four extenders examined; （2） the appropriate ratio of semen to extender of Yao et al. plus cryoprotectant is from 1：5 to 1：7; （3） dimethyl sulfoxide （DMSO） and methanol are the better cryoprotectants than glycerol, with DMSO giving the best results; （4） the eggs fertilized with post-thaw spermatozoa are capable of developing to at least hatching stage, and the highest hatching rate is （12.4±3.0）%. This is the first report on freezing and thawing of amphioxus spermatozoa, providing a simple and practical protocol for cryopreservation of amphioxus spermatozoa and laying a foundation for safeguarding this endangered species.展开更多
The concentrations of heavy metals （As, Hg, Cr, Pb and Zn） were measured in the macroalgae, macrobenthos and fish from the Tanzanian coastal marine environment in order to ascertain the biomagnification using stable...The concentrations of heavy metals （As, Hg, Cr, Pb and Zn） were measured in the macroalgae, macrobenthos and fish from the Tanzanian coastal marine environment in order to ascertain the biomagnification using stable isotopes of C and N. Macroalgae samples from the central marine areas of the Tanzanian coast had higher mean concentrations of Hg （0.17 ± 0.01 μg/g） and Cr （23.7 ± 4.15 μg/g） compared to other locations. Higher concentration of Hg （0.06 ±0.02 μg/g） was detected in the Ulva fasciata close to the Msimbazi Creek in Dares Salaam, whereas the highest concentration of Cr （45.5 ± 6.83 μg/g） was found in Ulva petrusa near Dares Salaam port. The crab Portunus pelagicus collected from Pangani river estuary contained 411.5 ± 13.04 μg/g of Zn. The other metals were uniformly distributed in macrobenthos from the entire coast. Mercury and lead in the biota were found to biomagnify along the Arius dussumieri and Lethrinus lentjan food chains as suggested by the significant positive relationships between log-pollutant concentrations in fish muscle tissues vs. 615N signatures. Zinc in muscle tissues was found to be transferred along the food webs although no biomagnification was observed. Arsenic and chromium were found to decrease with the rise of the trophic position. Metal concentrations in macroalgae, macrobenthos and fish were compared with quality guidelines values by FAO （Food and Agricultural Organization） in 1983 and they all were below permissible limits for human consumption.δ展开更多
Quantitative variations in parasites were investigated with respect to sex and size of Clarias gariepinus, season and localities sampled. Parasitic infection in male and female fish was not significantly different;pre...Quantitative variations in parasites were investigated with respect to sex and size of Clarias gariepinus, season and localities sampled. Parasitic infection in male and female fish was not significantly different;prevalence (Man-Whitney paired sample test, U = 135.5, p = 0.7697), mean intensity (U = 136, p = 0.7829). Based on Kruskal-Wallis test analysis, the prevalence and mean intensity of five parasite species varied significantly among the three localities sampled. Adult parasites in Clarias gariepinus showed high abundance during the dry season while the larval forms showed high abundance in the wet season. In most of the parasite species analyzed the abundance varied significantly with host size. The abundance of Dolops ranarum, Paracamallanus cyatopharynx and Eumasenia bangweulensis for instance, increased with fish size, while that of Diplostomum mashonense, Tylodelphys species, Astiotrema reniferum, piscicolid leeches and Monobothrioides woodlandi increased initially but decreased as fish length reached 31 - 40 cm. Total parasite burden increased in fish of 20 - 40 cm standard length. Generally, most parasites were highly overdispersed and the negative binomial model described their distribution.展开更多
Six hundred and fifty-eight specimens of the Clariidae were collected from seven localities in the Lake Victoria basin and the Malagarasi wetland, Tanzania. A total of three hundred unadjusted morphometric measurement...Six hundred and fifty-eight specimens of the Clariidae were collected from seven localities in the Lake Victoria basin and the Malagarasi wetland, Tanzania. A total of three hundred unadjusted morphometric measurements and meristic counts were analysed with the aim of assessing the adequacy of morphometric technique to delineate the clariid species occurring in theLake Victoriabasin. Results showed that morphometrics augmented by multivariate analysis (PCA, DCA and cluster analysis) amalgamated the clariid fishes into three groups, the?Clarias alluaudi/C. werneri,?C. gariepinus/C. liocephalus?andClariallabes petricola. Although other workers have used this technique, the present study concluded that, standing alone morphometrics is not a substitute for external morphology in the identification of clariid fish species, as it failed to separate the clariids into their respective taxonomic species. The technique, however, insinuates the regressional morphological relationships among the clariids occurring in the Lake Victoria basin.展开更多
A total of 32 parasite species were documented from 658 clariid fishes examined. Thirteen species were nematodes, eleven digeneans, three cestodes, two crustaceans, and the Monogenea, Acanthocephala and Hirudinea were...A total of 32 parasite species were documented from 658 clariid fishes examined. Thirteen species were nematodes, eleven digeneans, three cestodes, two crustaceans, and the Monogenea, Acanthocephala and Hirudinea were each represented by one species. Of the parasites recovered 16 were identified to species level, 12 to genus and 4 parasites were not identified. Most of the parasites recorded in the present study have been reported in fish ofTanzaniaand elsewhere, however, there were a few first records, and these included Neogoezia sp., Comephoronema sp., Travnema sp., Quimperia sp. and Gendria tilapiae. It is stipulated that these parasites represent the original fauna of the lake prior to introduction of the alien species. The clariid fish species investigated were a good model for studying the parasites of fish in the lake because of having a variety of parasites some of which being specific to certain clariid fishes, for instance Diplostomum and Tylodelphys species infecting only C. gariepinus and the camallanids being typical of the clariid fishes.展开更多
Estimating magnetic properties of water samples by first measuring the Anhysteretic Remanent Magnetization (ARM) before Isothermal Remanent Magnetization (IRM) is induced has been costly due to the discard of samples ...Estimating magnetic properties of water samples by first measuring the Anhysteretic Remanent Magnetization (ARM) before Isothermal Remanent Magnetization (IRM) is induced has been costly due to the discard of samples measured by staring with the latter before the former. However, no clear understanding exists on the effect of measuring magnetic properties values by first inducing IRM before ARM. This study explored the effect of measuring concentration related parameters (χlf, χfd and χARM), a mineral related parameter (S-300) and grain size parameters (χfd% and χARM/SIRM ratio) fromwater samples by starting with IRM before ARM. Forty three surface water samples were collected from the estuarine of Yangtze River (China) with the aim of measuring magnetic characteristics by starting with IRM before ARM. The results indicated that, measuring magnetic properties by either starting with ARM or IRM led to similar values for χlf, χfd, χfd%, χARM, S-300 and χARM/SIRM ratio (p > 0.05). These results imply that, measuring concentrationrelated parameters does not necessarily require measuring ARM first and then IRM. Researchers can start by measuring any parameter between ARM and IRM without affecting the final results of the water samples, but with proper demagnetization when started with IRM.展开更多
From 2012 to 2015, we measured surface ozone, NOx, NO2, and NO levels at three urban sites (Mapipa, Ubungo, and Posta) and two suburban sites (Kunduchi and Vijibweni) in the city of Dar es Salaam and in the village of...From 2012 to 2015, we measured surface ozone, NOx, NO2, and NO levels at three urban sites (Mapipa, Ubungo, and Posta) and two suburban sites (Kunduchi and Vijibweni) in the city of Dar es Salaam and in the village of Mwetemo, a rural area of Bagamoyo, Tanzania. The average hourly O3 concentrations at all sites were between 9 ppb and 30 ppb during our sampling periods. O3 levels at suburban sites were generally higher than at urban sites. The average hourly concentrations in Dar es Salaam were 10 - 32 ppb, while in Bagamoyo they were 9 - 15 ppb. We observed a strong diurnal variation in Dar es Salaam while measurements from Bagamoyo showed little variation. At Dar es Salaam, the surface O3 concentrations increased from their minimum level at sunrise (around 6:00 a.m.) to a maximum in the late afternoon (around 4:00 p.m.), and then decreased toward 11:00 p.m. Another secondary ozone peak appeared between midnight and ~4:00 a.m., after which the surface ozone concentrations decreased to a minimum around 7:00 a.m. NO2 concentrations were higher at the urban sites of Ubungo and Posta, and their weekly average NO2 concentrations were 246 ppb and 118 ppb, respectively. Weekly average NOx concentrations ranged from 39.4 ppb at the Kunduchi site (suburban) to 738 ppb at the Ubungo site (urban). To our knowledge, there were few continuous measurements of ozone and nitrogen oxides concentrations in Tanzania. Since high NOx concentrations were observed, continuous air quality monitoring and effective air pollution control measures are required in Dar es Salaam to prevent further deterioration of air quality and limit the possible negative impacts on humans and vegetation.展开更多
The present study investigated the concentration and species of heavy metals As, Hg, Cr, Pb and Zn in water and As, Hg, Cr, Pb and Zn in sediments collected along the coastal marine areas of Tanzania so as to determin...The present study investigated the concentration and species of heavy metals As, Hg, Cr, Pb and Zn in water and As, Hg, Cr, Pb and Zn in sediments collected along the coastal marine areas of Tanzania so as to determine their behaviour and remobilization potential in the environment and the degree of their availability to edible aquatic biota for monitoring purposes. Sequential extraction revealed the presence of a significant proportion of heavy metals Cr, Pb and Zn bound to available fractions of sediments. Arsenic had the highest concentration in non available residual fractions. PCA analysis found that As-Hg, Cr-Pb were strongly correlated and that the two may be derived from the same source most likely from storm water drainage of waste water discharges, while Zn may have come from the different source like watershed erosion. Further, PCA clearly confirms the same. Generally, Zn among all heavy metals analysed was the most available to aquatic biota due to its higher average concentrations in the acid soluble fraction, followed by chromium. However, high percentages of metal species studied in Tanzania coastal marine areas were found in non available fractions which indicated that the edible aquatic biota was safe for human consumptions.展开更多
浙江瓯江口及邻近水域是东海诸多经济鱼类的重要栖息地。本研究对采自瓯江口6个地点,34尾玻璃鳗样本进行遗传鉴定。通过对线粒体D-loop 800 bp DNA序列分析,共检测得到34个不同单倍型,这些单倍型与GenBank中的日本鳗鲡D-loop序列相似度...浙江瓯江口及邻近水域是东海诸多经济鱼类的重要栖息地。本研究对采自瓯江口6个地点,34尾玻璃鳗样本进行遗传鉴定。通过对线粒体D-loop 800 bp DNA序列分析,共检测得到34个不同单倍型,这些单倍型与GenBank中的日本鳗鲡D-loop序列相似度最高(>99%),说明这些鳗鲡为日本鳗鲡。瓯江口鳗鲡群体的单倍型多态性(Hd)为1.0±0.007,核苷酸多态性(π)为0.011±0.000 8,说明该群体的遗传变异水平较高。各采样点之间没有显著的遗传差异(FST=-0.028)。根据Tajima’s D中性检验(D=-1.982 96,P<0.01)和核苷酸错配分布结果,推测这些日本鳗鲡可能在近期发生过种群爆发性扩张。展开更多
This pilot study intended to investigate the application of Mixing Zone Guidelines in northern Sweden. The EC （European Commission）-Mixing Zone Guidelines were applied to seven effluent discharges. The effluents wer...This pilot study intended to investigate the application of Mixing Zone Guidelines in northern Sweden. The EC （European Commission）-Mixing Zone Guidelines were applied to seven effluent discharges. The effluents were from industrial processes used in the Ronnskar smelter, in northern Sweden. Each outlet in the smelter area discharges water into the Bothnian bay of the Baltic Sea. Cadmium （Cd）, mercury （Hg）, nickel （Ni） and lead （Pb） were the primary substances present in the effluents. A ＂Tiered Approach＂ was followed for mixing zone assessments in each of the discharge points. Discharge Test was used at Tier 2 and CORMIX （Cornell Mixing Zone Expert System model）, version 7, at Tier 3. At each discharge point, the AA-EQS （annual average-environmental quality standard） for each metal was met within a distance of 500 m from the outfalls. This distance was exceeded to meet the MAC-EQS （maximum allowable concentration-environmental quality standard） criteria at points 1 and 3 for total Hg concentrations. However, for the proper application of Mixing Zone Guidelines, a version of the Discharge Test for coastal waters should be developed and used. The decision at which tier the dissolved metal concentration should be compared with EQS values could depend on the effluent characteristics. For Swedish coastal waters, some consideration should be given to the background concentration of metals.展开更多
The phylogenetic relationships among “Barbus” species (Barbus jacksonii, B. paludinosus and B. trimaculatus) from Malagarasi and Pangani River systems were examined by partial mitochondrial cytochrome b (cyt.b) gene...The phylogenetic relationships among “Barbus” species (Barbus jacksonii, B. paludinosus and B. trimaculatus) from Malagarasi and Pangani River systems were examined by partial mitochondrial cytochrome b (cyt.b) gene. Sequences of the same samples from elsewhere in Africa obtained from the South African Institute of Aquatic Biodiversity (SAIAB’s) collection were also included in the analysis. Molecular technique was necessary due to phenotypic plasticity and extensive overlap of morphological features among the “Barbus species”. The findings of this study revealed that B. paludinosus from hale and Pangani populations occurred in two distinct genetic lineages though separated by a distance of approximately 10 km apart. Similar results were also noted amongst the population of B. paludinosus in Songati and Muumbara located on Lake Sagara in Malagarasi River basin. B. trimaculatus and B. jacksonii were indistinguishable such that it is envisaged that the two species are one and the same. The Barbus spp. from Africa included in the current study showed genetic affinity to neither European Barbus spp. nor South African redfins of the Pseudobarbus to conclude that the studied species of barbs are taxonomically quite different that needs further investigation to warrant renaming.展开更多
Estuaries are usually characterized by strong spatial and temporal variability in water physicochemical conditions and are often largely affected by human activities.One important source of variability is caused by ti...Estuaries are usually characterized by strong spatial and temporal variability in water physicochemical conditions and are often largely affected by human activities.One important source of variability is caused by tides that can swiftly alter not only physicochemical conditions but also the abundance and composition of the biota.The effect of the diurnal tidal cycle on microbial community composition during different seasons remains uncertain,although this knowledge underlies having effective monitoring programs for water quality and potential identification of health risk conditions.In this study,we assessed the bacterioplankton community composition and diversity across four tidal water levels in a tropical estuary characterized by a mixed semidiurnal tide regime(i.e.,two high and two low tides of varying amplitudes)during both dry and wet seasons.The bacterial community composition varied significantly among the four tidal levels,but only during the dry season,when the influence of the seawater intrusion was largest.Bacterial indicators’taxa identified using the Indicator Value Index were found within Cyanobacteria,Actinobacteriota,Bacteroidota,and Proteobacteria.The indicator taxon Cyanobium sp.had a prominent presence across multiple tidal levels.The main predicted phenotypes of the bacterial communities were associated with potential pathogenicity,gram-negative,and biofilm formation traits.While there were no marked predicted phenotypic differences between seasons,pathogenic and gram-negative traits were more prevalent in the dry season,while biofilm formation traits dominated in the wet season.Overall,our findings underscore the intricate relationship between river hydrodynamics and bacterial composition variability and hint a significant human impact on the water quality of the Bangpakong River.展开更多
The culture of African sharptooth catfish(Clarias gariepinus)in most developing countries lacks suitable diets for semi-intensive production.The present study evaluated the growth performance,survival,nutrient utiliza...The culture of African sharptooth catfish(Clarias gariepinus)in most developing countries lacks suitable diets for semi-intensive production.The present study evaluated the growth performance,survival,nutrient utilization,hepatosomatic index(HSI),body composition,yield and feeding cost of African catfish fed on semi-intensive feeds 1(SMF1)and semi-intensive feed 2(SMF2)produced on-farm and an industrially manufactured(IM)feed as a control.Two hundred fish(14.95±0.24 g)were stocked in triplicate earthen ponds and fed the three diets at 5%of the body weight for eight weeks.The final weight,specific growth rate and yield of fish fed the SMF2 diet was significantly lower than SMF1 and IM diets.However,no significant differences were revelead in final weight,specific growth rate and yield between fish fed SMF1 and IM diets.The survival rate,feed conversion ratio and protein efficiency ratio of fish did not differ among the diets.Apparent net protein utilization was significantly higher on fish fed the SMF2 and SMF1 diets than IM diet.The HSI of fish fed the IM diet was significantly higher and the livers were yellow-coloured compared to smaller and brownish/reddish livers of fish fed the SMF1 and SMF2 diets.The fish fed the IM diet had statistically lower ash content than SMF1 diet.The incidence cost of fish fed the IM diet was 35%higher,while its profit index was 31%lower than fish fed the SMF1 and SMF2 diets.Taken together,African catfish farmers can reduce feed cost up to 30%by using on-farm produced feeds when formulated properly and blended without affecting fish growth performance,survival and yield while obtaining better protein retention and healthier fish.展开更多
Lipophagy is a form of autophagy in mammals.In this cellular process,lipid droplets(LDs)are degraded through the lysosomal degradative pathway[1].During lipophagy,LDs sequestrated in autophagosomes are delivered to ly...Lipophagy is a form of autophagy in mammals.In this cellular process,lipid droplets(LDs)are degraded through the lysosomal degradative pathway[1].During lipophagy,LDs sequestrated in autophagosomes are delivered to lysosomes,which fuse to form autophagosomes and then develop into autophagolysosomes,leading to LDs degradation of[1].A number of studies have demonstrated that lipophagy play important roles in lipid展开更多
Atmospheric emission and deposition of mercury(Hg),a toxic metal of global concern,has been long considered to control environmental Hg levels in water,soil,sediment,and ultimately fish,which is the major exposure sou...Atmospheric emission and deposition of mercury(Hg),a toxic metal of global concern,has been long considered to control environmental Hg levels in water,soil,sediment,and ultimately fish,which is the major exposure source for humans.In the last two decades,a number of studies of varying spatiotemporal scales and approaches have shown that fish Hg,particularly in lakes and open oceans,is positively and linearly correlated with atmospheric Hg deposition through both dry and/or wet deposition[1-3].展开更多
文摘The sergestid shrimp Acetes vulgaris has long been an important fishery species in estuaries and coastal waters along the Pang-Rad River, Rayong province, Thailand. In nature, this shrimp feeds on a wide range of food items, such as phytoplankton, zooplankton, algae, plant matter, debris, sand, and mud. The objective of this study was to compare different feeds on growth and survival of A. vulgaris reared in fiberglass tanks containing 70 m<sup>3</sup> of seawater salinity 25 ppt over a period of 70 days. Individual shrimps were fed with four different types of feeds i.e., newly hatched Artemia (Ar), rotifer (Ro), newly hatched Artemia + rotifer (ArRo) and shrimp larvae commercial feed (SF). Results suggested that specific growth rates (both for body weight and body length) of shrimps reared with SF were not significantly different with treatment feed with Ar, ArRo and Ro (p ≥ 0.05). The survival rate of A. vulgaris did not vary significantly (p ≥ 0.05) among the Ar, Ro and ArRo treatments. However, the highest survival rate of shrimp (81.78% ± 3.08%) was observed in SF treatment and the percentage of survival rate was significantly different with treatment feed with Ar, Ro and ArRo (p ≤ 0.05). The findings reflected the ability of Acetes shrimps to consume diverse food types including both live feed and pelleted feed. Insights obtained from this research suggested that artificial feed can be as efficient as live feeds. This new knowledge is a needed addition to a currently lacking knowledge base for aquaculture of this Acetes species.
文摘Freshwater habitats and organisms are among the most threatened on Earth, and freshwater ecosystems have been subject to large biodiversity losses. We developed a Climate Change Sensitivity （CCS） indicator based on trait information for a selection of stream- and lake-dwelling Ephemeroptera, Plecoptera and Trichoptera taxa. We calculated the CCS scores based on ten species traits identified as sensitive to global climate change. We then assessed climate change sensitivity between the six main ecoregions of Sweden as well as the three Swedish regions based on lilies. This was done using biological data from 1,382 stream and lake sites where we compared large-scale （ecoregional） patterns in climate change sensitivity with potential future exposure of these ecosystems to increased temperatures using ensemble-modelled future changes in air temperature. Current （1961-1990） measured temperature and ensemble-modelled future （2100） temperature showed an increase from the northernmost towards the southern ecoregions, whereas the predicted temperature change increased from south to north. The CCS indicator scores were highest in the two northernmost boreal ecoregions where we also can expect the largest global climate change-induced increase in temperature, indicating an unfortunate congruence of exposure and sensitivity to climate change. These results are of vital importance when planning and implementing management and conservation strategies in freshwater ecosystems, e.g., to mitigate increased temperatures using riparian buffer strips. We conclude that traits information on taxa specialization, e.g., in terms of feeding specialism or taxa having a preference for high altitudes as well as sensitivity to changes in temperature are important when assessing the risk from future global climate change to freshwater ecosystems [Current Zoology 60 （2）： 221-232, 2014].
基金the support of the Portuguese Foundation for Science and Technology through a Pos Doc fellowship (No. SFRH/BPD/110730/2015)partially supported by the Strategic Funding (No. UID/Multi/ 04423/2013) through national funds provided by Portuguese Foundation for Science and Technology and European Regional Development Fund, in the framework of the program PT2020
文摘Estuarine ecosystems in SE Asia have been poorly studied when compared to other tropical environments. Important gaps exist particularly in the understanding of their biogeochemical function and contribution to global change. In this work we looked into N-turnover in the water column and sediments of the Bangpakong estuary（13°N）. A seasonal sampling program was performed along the salinity gradient covering different stretches of the estuary（68 km）.Key physical and chemical characteristics were also monitored in order to unravel possible environmental controls. Results showed the occurrence of active denitrification in sediments（5.7–50.9 nmol N-N2/（cm3·hr））, and water column（3.5–1044 pmol N-N2/（cm3·hr））. No seasonal or spatial variability was detected for denitrification potential in sediment samples. However, in the water column, the denitrification activity peaked during the transition season in the downstream sites coinciding with high turbidity levels. Therefore, in that period of the year, the water column compartment may be an important contributor to nitrate reduction within the estuary. The rather low nitrification rates detected were not always measurable, probably due to the reduced oxygen content and high siltation. This study is one of the few dealing simultaneously with sediments and water column processes in a highly turbid tropical estuary.Therefore, it emerges as a valuable contribution for the understanding of the dynamics of the nitrogen cycle in tropical environments by exploring the role of estuarine N microbial activity in reducing the effects of increased nitrogen loads.
基金The Financial Support Jointly by the National Research Council of Thailand and the German Research Foundation。
文摘The devastating 2004 tsunamis that hit the southwestern coast of Thailand pose a serious threat to people along the coastal zone. A major aim for the tsunami hazard prediction is better prediction of the next tsunamis and their impacts. In this paper, we present the first implications of recent slope failure events of the Andaman outer shelf and upper slope based on a new detailed bathymetric data and subbottom profiler records acquired during two cruises of the MASS project in 2006 and 2007. Morphometric analysis reveals a variety of anomalous features,including: three large plateaus surrounded by moats, ruggedness and unevenness of slope morphology, and two translational submarine landslides. Two submarine landslides are studied from the detailed bathymetric data and subbottom profiler record covering the upper slope of the Andaman Sea shelf break within Thai exclusive economic zone. Maximum approximated volumes of both displaced masses are 4.8×10~7 m~3 and 2.2×10~7 m~3.Considering the data, there is no evidence that landslides have been the sources for tsunami hazard potential in recent geological time. These prerequisites will allow better study of slope failure events in the area. Further investigation is required to better understand obvious geotectonic phenomena.
基金The Ministry of Science and Technology (MOST) of China
文摘Amphioxus, Branchiostoma belcheri, a closest relative of vertebrates, is at a high risk of extinction due to a combination of low effective population size, altered native habitats and environmental pollution, yet little is known about cryopreservation of its gametes. This study deals with the cryopreservation of amphioxus senlen. The main findings are that （1） the extender of Yao et al. is the best one among the four extenders examined; （2） the appropriate ratio of semen to extender of Yao et al. plus cryoprotectant is from 1：5 to 1：7; （3） dimethyl sulfoxide （DMSO） and methanol are the better cryoprotectants than glycerol, with DMSO giving the best results; （4） the eggs fertilized with post-thaw spermatozoa are capable of developing to at least hatching stage, and the highest hatching rate is （12.4±3.0）%. This is the first report on freezing and thawing of amphioxus spermatozoa, providing a simple and practical protocol for cryopreservation of amphioxus spermatozoa and laying a foundation for safeguarding this endangered species.
文摘The concentrations of heavy metals （As, Hg, Cr, Pb and Zn） were measured in the macroalgae, macrobenthos and fish from the Tanzanian coastal marine environment in order to ascertain the biomagnification using stable isotopes of C and N. Macroalgae samples from the central marine areas of the Tanzanian coast had higher mean concentrations of Hg （0.17 ± 0.01 μg/g） and Cr （23.7 ± 4.15 μg/g） compared to other locations. Higher concentration of Hg （0.06 ±0.02 μg/g） was detected in the Ulva fasciata close to the Msimbazi Creek in Dares Salaam, whereas the highest concentration of Cr （45.5 ± 6.83 μg/g） was found in Ulva petrusa near Dares Salaam port. The crab Portunus pelagicus collected from Pangani river estuary contained 411.5 ± 13.04 μg/g of Zn. The other metals were uniformly distributed in macrobenthos from the entire coast. Mercury and lead in the biota were found to biomagnify along the Arius dussumieri and Lethrinus lentjan food chains as suggested by the significant positive relationships between log-pollutant concentrations in fish muscle tissues vs. 615N signatures. Zinc in muscle tissues was found to be transferred along the food webs although no biomagnification was observed. Arsenic and chromium were found to decrease with the rise of the trophic position. Metal concentrations in macroalgae, macrobenthos and fish were compared with quality guidelines values by FAO （Food and Agricultural Organization） in 1983 and they all were below permissible limits for human consumption.δ
文摘Quantitative variations in parasites were investigated with respect to sex and size of Clarias gariepinus, season and localities sampled. Parasitic infection in male and female fish was not significantly different;prevalence (Man-Whitney paired sample test, U = 135.5, p = 0.7697), mean intensity (U = 136, p = 0.7829). Based on Kruskal-Wallis test analysis, the prevalence and mean intensity of five parasite species varied significantly among the three localities sampled. Adult parasites in Clarias gariepinus showed high abundance during the dry season while the larval forms showed high abundance in the wet season. In most of the parasite species analyzed the abundance varied significantly with host size. The abundance of Dolops ranarum, Paracamallanus cyatopharynx and Eumasenia bangweulensis for instance, increased with fish size, while that of Diplostomum mashonense, Tylodelphys species, Astiotrema reniferum, piscicolid leeches and Monobothrioides woodlandi increased initially but decreased as fish length reached 31 - 40 cm. Total parasite burden increased in fish of 20 - 40 cm standard length. Generally, most parasites were highly overdispersed and the negative binomial model described their distribution.
文摘Six hundred and fifty-eight specimens of the Clariidae were collected from seven localities in the Lake Victoria basin and the Malagarasi wetland, Tanzania. A total of three hundred unadjusted morphometric measurements and meristic counts were analysed with the aim of assessing the adequacy of morphometric technique to delineate the clariid species occurring in theLake Victoriabasin. Results showed that morphometrics augmented by multivariate analysis (PCA, DCA and cluster analysis) amalgamated the clariid fishes into three groups, the?Clarias alluaudi/C. werneri,?C. gariepinus/C. liocephalus?andClariallabes petricola. Although other workers have used this technique, the present study concluded that, standing alone morphometrics is not a substitute for external morphology in the identification of clariid fish species, as it failed to separate the clariids into their respective taxonomic species. The technique, however, insinuates the regressional morphological relationships among the clariids occurring in the Lake Victoria basin.
文摘A total of 32 parasite species were documented from 658 clariid fishes examined. Thirteen species were nematodes, eleven digeneans, three cestodes, two crustaceans, and the Monogenea, Acanthocephala and Hirudinea were each represented by one species. Of the parasites recovered 16 were identified to species level, 12 to genus and 4 parasites were not identified. Most of the parasites recorded in the present study have been reported in fish ofTanzaniaand elsewhere, however, there were a few first records, and these included Neogoezia sp., Comephoronema sp., Travnema sp., Quimperia sp. and Gendria tilapiae. It is stipulated that these parasites represent the original fauna of the lake prior to introduction of the alien species. The clariid fish species investigated were a good model for studying the parasites of fish in the lake because of having a variety of parasites some of which being specific to certain clariid fishes, for instance Diplostomum and Tylodelphys species infecting only C. gariepinus and the camallanids being typical of the clariid fishes.
文摘Estimating magnetic properties of water samples by first measuring the Anhysteretic Remanent Magnetization (ARM) before Isothermal Remanent Magnetization (IRM) is induced has been costly due to the discard of samples measured by staring with the latter before the former. However, no clear understanding exists on the effect of measuring magnetic properties values by first inducing IRM before ARM. This study explored the effect of measuring concentration related parameters (χlf, χfd and χARM), a mineral related parameter (S-300) and grain size parameters (χfd% and χARM/SIRM ratio) fromwater samples by starting with IRM before ARM. Forty three surface water samples were collected from the estuarine of Yangtze River (China) with the aim of measuring magnetic characteristics by starting with IRM before ARM. The results indicated that, measuring magnetic properties by either starting with ARM or IRM led to similar values for χlf, χfd, χfd%, χARM, S-300 and χARM/SIRM ratio (p > 0.05). These results imply that, measuring concentrationrelated parameters does not necessarily require measuring ARM first and then IRM. Researchers can start by measuring any parameter between ARM and IRM without affecting the final results of the water samples, but with proper demagnetization when started with IRM.
文摘From 2012 to 2015, we measured surface ozone, NOx, NO2, and NO levels at three urban sites (Mapipa, Ubungo, and Posta) and two suburban sites (Kunduchi and Vijibweni) in the city of Dar es Salaam and in the village of Mwetemo, a rural area of Bagamoyo, Tanzania. The average hourly O3 concentrations at all sites were between 9 ppb and 30 ppb during our sampling periods. O3 levels at suburban sites were generally higher than at urban sites. The average hourly concentrations in Dar es Salaam were 10 - 32 ppb, while in Bagamoyo they were 9 - 15 ppb. We observed a strong diurnal variation in Dar es Salaam while measurements from Bagamoyo showed little variation. At Dar es Salaam, the surface O3 concentrations increased from their minimum level at sunrise (around 6:00 a.m.) to a maximum in the late afternoon (around 4:00 p.m.), and then decreased toward 11:00 p.m. Another secondary ozone peak appeared between midnight and ~4:00 a.m., after which the surface ozone concentrations decreased to a minimum around 7:00 a.m. NO2 concentrations were higher at the urban sites of Ubungo and Posta, and their weekly average NO2 concentrations were 246 ppb and 118 ppb, respectively. Weekly average NOx concentrations ranged from 39.4 ppb at the Kunduchi site (suburban) to 738 ppb at the Ubungo site (urban). To our knowledge, there were few continuous measurements of ozone and nitrogen oxides concentrations in Tanzania. Since high NOx concentrations were observed, continuous air quality monitoring and effective air pollution control measures are required in Dar es Salaam to prevent further deterioration of air quality and limit the possible negative impacts on humans and vegetation.
文摘The present study investigated the concentration and species of heavy metals As, Hg, Cr, Pb and Zn in water and As, Hg, Cr, Pb and Zn in sediments collected along the coastal marine areas of Tanzania so as to determine their behaviour and remobilization potential in the environment and the degree of their availability to edible aquatic biota for monitoring purposes. Sequential extraction revealed the presence of a significant proportion of heavy metals Cr, Pb and Zn bound to available fractions of sediments. Arsenic had the highest concentration in non available residual fractions. PCA analysis found that As-Hg, Cr-Pb were strongly correlated and that the two may be derived from the same source most likely from storm water drainage of waste water discharges, while Zn may have come from the different source like watershed erosion. Further, PCA clearly confirms the same. Generally, Zn among all heavy metals analysed was the most available to aquatic biota due to its higher average concentrations in the acid soluble fraction, followed by chromium. However, high percentages of metal species studied in Tanzania coastal marine areas were found in non available fractions which indicated that the edible aquatic biota was safe for human consumptions.
文摘This pilot study intended to investigate the application of Mixing Zone Guidelines in northern Sweden. The EC （European Commission）-Mixing Zone Guidelines were applied to seven effluent discharges. The effluents were from industrial processes used in the Ronnskar smelter, in northern Sweden. Each outlet in the smelter area discharges water into the Bothnian bay of the Baltic Sea. Cadmium （Cd）, mercury （Hg）, nickel （Ni） and lead （Pb） were the primary substances present in the effluents. A ＂Tiered Approach＂ was followed for mixing zone assessments in each of the discharge points. Discharge Test was used at Tier 2 and CORMIX （Cornell Mixing Zone Expert System model）, version 7, at Tier 3. At each discharge point, the AA-EQS （annual average-environmental quality standard） for each metal was met within a distance of 500 m from the outfalls. This distance was exceeded to meet the MAC-EQS （maximum allowable concentration-environmental quality standard） criteria at points 1 and 3 for total Hg concentrations. However, for the proper application of Mixing Zone Guidelines, a version of the Discharge Test for coastal waters should be developed and used. The decision at which tier the dissolved metal concentration should be compared with EQS values could depend on the effluent characteristics. For Swedish coastal waters, some consideration should be given to the background concentration of metals.
文摘The phylogenetic relationships among “Barbus” species (Barbus jacksonii, B. paludinosus and B. trimaculatus) from Malagarasi and Pangani River systems were examined by partial mitochondrial cytochrome b (cyt.b) gene. Sequences of the same samples from elsewhere in Africa obtained from the South African Institute of Aquatic Biodiversity (SAIAB’s) collection were also included in the analysis. Molecular technique was necessary due to phenotypic plasticity and extensive overlap of morphological features among the “Barbus species”. The findings of this study revealed that B. paludinosus from hale and Pangani populations occurred in two distinct genetic lineages though separated by a distance of approximately 10 km apart. Similar results were also noted amongst the population of B. paludinosus in Songati and Muumbara located on Lake Sagara in Malagarasi River basin. B. trimaculatus and B. jacksonii were indistinguishable such that it is envisaged that the two species are one and the same. The Barbus spp. from Africa included in the current study showed genetic affinity to neither European Barbus spp. nor South African redfins of the Pseudobarbus to conclude that the studied species of barbs are taxonomically quite different that needs further investigation to warrant renaming.
基金supported by Burapha University through the National Research Council of Thailand(Grant number:53/2562)to CPfunding from ANID-Millennium Science Initiative Pro-gram-NCN2021-056,RS and CP received funding from the Aus-trian Agency for International Cooperation in Education and Research through the ASEA-UNINET Program(MPC-2022-04066).
文摘Estuaries are usually characterized by strong spatial and temporal variability in water physicochemical conditions and are often largely affected by human activities.One important source of variability is caused by tides that can swiftly alter not only physicochemical conditions but also the abundance and composition of the biota.The effect of the diurnal tidal cycle on microbial community composition during different seasons remains uncertain,although this knowledge underlies having effective monitoring programs for water quality and potential identification of health risk conditions.In this study,we assessed the bacterioplankton community composition and diversity across four tidal water levels in a tropical estuary characterized by a mixed semidiurnal tide regime(i.e.,two high and two low tides of varying amplitudes)during both dry and wet seasons.The bacterial community composition varied significantly among the four tidal levels,but only during the dry season,when the influence of the seawater intrusion was largest.Bacterial indicators’taxa identified using the Indicator Value Index were found within Cyanobacteria,Actinobacteriota,Bacteroidota,and Proteobacteria.The indicator taxon Cyanobium sp.had a prominent presence across multiple tidal levels.The main predicted phenotypes of the bacterial communities were associated with potential pathogenicity,gram-negative,and biofilm formation traits.While there were no marked predicted phenotypic differences between seasons,pathogenic and gram-negative traits were more prevalent in the dry season,while biofilm formation traits dominated in the wet season.Overall,our findings underscore the intricate relationship between river hydrodynamics and bacterial composition variability and hint a significant human impact on the water quality of the Bangpakong River.
基金funded by the World Bank through the University of Dar es Salaam,under the project“Higher Education Science and Technology(HEST)”component CIA:5.1.
文摘The culture of African sharptooth catfish(Clarias gariepinus)in most developing countries lacks suitable diets for semi-intensive production.The present study evaluated the growth performance,survival,nutrient utilization,hepatosomatic index(HSI),body composition,yield and feeding cost of African catfish fed on semi-intensive feeds 1(SMF1)and semi-intensive feed 2(SMF2)produced on-farm and an industrially manufactured(IM)feed as a control.Two hundred fish(14.95±0.24 g)were stocked in triplicate earthen ponds and fed the three diets at 5%of the body weight for eight weeks.The final weight,specific growth rate and yield of fish fed the SMF2 diet was significantly lower than SMF1 and IM diets.However,no significant differences were revelead in final weight,specific growth rate and yield between fish fed SMF1 and IM diets.The survival rate,feed conversion ratio and protein efficiency ratio of fish did not differ among the diets.Apparent net protein utilization was significantly higher on fish fed the SMF2 and SMF1 diets than IM diet.The HSI of fish fed the IM diet was significantly higher and the livers were yellow-coloured compared to smaller and brownish/reddish livers of fish fed the SMF1 and SMF2 diets.The fish fed the IM diet had statistically lower ash content than SMF1 diet.The incidence cost of fish fed the IM diet was 35%higher,while its profit index was 31%lower than fish fed the SMF1 and SMF2 diets.Taken together,African catfish farmers can reduce feed cost up to 30%by using on-farm produced feeds when formulated properly and blended without affecting fish growth performance,survival and yield while obtaining better protein retention and healthier fish.
基金supported by the National Basic Research Program of China(2014CB138603)
文摘Lipophagy is a form of autophagy in mammals.In this cellular process,lipid droplets(LDs)are degraded through the lysosomal degradative pathway[1].During lipophagy,LDs sequestrated in autophagosomes are delivered to lysosomes,which fuse to form autophagosomes and then develop into autophagolysosomes,leading to LDs degradation of[1].A number of studies have demonstrated that lipophagy play important roles in lipid
文摘Atmospheric emission and deposition of mercury(Hg),a toxic metal of global concern,has been long considered to control environmental Hg levels in water,soil,sediment,and ultimately fish,which is the major exposure source for humans.In the last two decades,a number of studies of varying spatiotemporal scales and approaches have shown that fish Hg,particularly in lakes and open oceans,is positively and linearly correlated with atmospheric Hg deposition through both dry and/or wet deposition[1-3].
