Water and sediment quality parameters in the Chalan Beel, the largest wetland of Bangladesh

A study was conducted to investigate the status of the water and sediment quality in the Chalan Beel——a major fresh water fish reservoir of the country for a period of one year from July 2007 to June 2008. The mean values of water quality parameters(depth: 214.73±152.22 cm, temperature 27.68±4.26℃, transparency 123±82 cm, p H 9.7±0.47, total alkalinity 137±42 mg/L, conductivity 307±147 μs/cm, total dissolved solids 183±89 mg/L, ammonia-N 0.27±0.39 mg/L, nitrate-N 0.09±0.07 mg/L, phosphate-P 2.01±2.53 mg/L) and sediment quality parameters(p H 7.21±0.35, organic matter 2.59±0.52%, total nitrogen 0.09±0.04%, available phosphorus 5.4±3.6 Meq./100 g and exchangeable potassium 0.43±0.14 Meq./100 g) were within the range recommended for most of the inland fishes of Bangladesh. Although the water and sediment quality parameters except ammonia and phosphate are in the suitable range, the overall results suggest that better management techniques should be practiced in order to overcome the declining trend of associated aquatic life(fauna and flora) of this important fresh water body of Bangladesh.

Spatio-temporal Evolution of Landscape Pattern and Habitat Quality in Yunnan Province

[Objectives]The paper was to explore the spatio-temporal evolution of habitat quality in inland ecosystem.[Methods]Using landscape pattern analysis and InVEST habitat quality model,the land use change,landscape pattern and habitat quality change in Yunnan Province from 1980 to 2020 were studied.[Results]The land use change in Yunnan Province was relatively stable,and the forest land area accounted for 57.2%of the total area.The landscape fragmentation index caused by artificial surface encroachment on ecological land was increased by 6.33%,and the landscape heterogeneity was enhanced to varying degrees.The mean patch area was decreased by 5.83%,the number of patches was increased by 6.29%,and the degree of fragmentation was deepened.The habitat quality in Yunnan Province showed a"high-low-high"distribution from northwest to southeast,and the overall habitat quality was above the average.It is necessary to formulate optimization strategies to improve the regional ecological environment and realize the ecological system protection and rational land use in Yunnan Province.[Conclusions]The results will provide a scientific reference for regional ecological protection construction and land use planning in Yunnan Province.

增加紫外辐射对海洋生态的影响

环境科学家面临的一项挑战性任务是如何根据各种生物和生物过程的研究来确定外部环境变化对自然生态系统的影响。评价紫外辐射大量增加对海洋环境产生的潜在影响是具有挑战性的任务。大量的紫外线辐射对海洋生态系统影响范围很广,并涉及难于观察的细微变化。特别引人注意的是由于长时间的辐射使许多海洋生物过程可能持续发生变化。另外,由于对海洋生态系统缺少缓冲辐射的措施和方法,使辐射的压力和影响范围正在加剧。如果承认上述推断,那么重要的问题就是用实验来验证这种推断。在本文中。

Effects of temperature and diet on length-weight relationship and condition factor of the juvenile Malabar blood snapper(Lutjanus malabaricus Bloch & Schneider, 1801)

In this study we aimed to analyze the effects of water temperature and diet on the length-weight rela- tionship and condition of juvenile Malabar blood snapper Lutjanus malabaricus over a 30-d experimental period. The experiment was conducted in the laboratory using a flow-through-sea-water system. The fish were subjected to four different temperatures （22, 26, 30, and 34 ℃） and two diets （commercial pellet and natural shrimp）. Fish were fed twice daily. L. malabancus exhibited negative allometric growth （b〈3） at the beginning of the experiment （Day 0） at all temperatures and both diets except for 22 ℃ fed with shrimp, which showed isometric growth （b=3）. Conversely, at the end of the experiment （Day 30） fish showed isometric growth （b=3） at 30 ℃ fed with the pellet diet, indicating that the shape of the fish did not change with increasing weight and length, and a positive allometric growth （b〉3） at 30 ℃ fed with shrimp diet, which indicated that fish weight increases faster than their length. The rest of the temperatures represented negative allometric growth （b〈3） on both diet, meaning that fish became lighter with increasing size. The condition factors in the initial and final measurements were greater than 1, indicating the state of health of the fish, except for those fed on a pellet diet at 34 ℃. However, the best condition was obtained at 30 ℃ on both diets. Nev- ertheless, diets did not have a significant effect on growth and condition of juvenile L. malabaricus. The data obtained from this study suggested culturing L. malabaricus at 30 ℃ and feeding on the pellet or shrimp diet, which will optimize the overall production and condition of this commercially important fish species.

Exogenous nitrogen input skews estimates of microbial nitrogen use efficiency by ecoenzymatic stoichiometry

Background Ecoenzymatic stoichiometry models(EEST)are often used to evaluate microbial nutrient use efficiency,but the validity of these models under exogenous nitrogen(N)input has never been clarified.Here,we investigated the effects of long-term N addition(as urea)on microbial N use efficiency(NUE),compared EEST and^(18)O-labeling methods for determining NUE,and evaluated EEST’s theoretical assumption that the ratios of standard ecoenzymatic activities balance resource availability with microbial demand.Results We found that NUE estimated by EEST ranged from 0.94 to 0.98.In contrast,estimates of NUE by the^(18)O-labeling method ranged from 0.07 to 0.30.The large differences in NUE values estimated by the two methods may be because the sum ofβ-N-acetylglucosaminidase and leucine aminopeptidase activities in the EEST model was not limited to microbial N acquisition under exogenous N inputs,resulting in an overestimation of microbial NUE by EEST.In addition,the acquisition of carbon by N-acquiring enzymes also likely interferes with the evaluation of NUE by EEST.Conclusions Our results demonstrate that caution must be exercised when using EEST to evaluate NUE under exogenous N inputs that may skew standard enzyme assays.