Contribution of benthic microalgae to the whole water algal biomass and primary production in Suo Nada,the Seto Inland Sea,Japan

Biomass and primary productivity of benthic microalgae (BMA) and planktonic algae in Suo Nada, the western part of the Seto Inland Sea, Japan were compared in terms of unit area with regard to their seasonal and spatial distribution in 2002. Judging from light compensation depth and water depth, the southwestern part of Suo Nada was considered to be a potential habitat for BMA. Whereas the contribution of sedimented planktonic algae was high in biomass at the sediment surface, BMA was obviously significant both in biomass and primary production in the shallow southwestern part. However, the contribution of BMA to the total biomass in the entire water column was 7% in winter and 2% in summer. The primary production of BMA varied between 4.0 and 74.0 mg C m⁻² d⁻¹ in the southwestern part, accounting for 2–12% of the whole water column primary production. The ecological roles of BMA in the Suo Nada ecosystem are discussed, such as reduction of benthic nutrient flux, oxidation of surface sediments and feed for higher animals.     

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.     

Groundwater scenario in Lakshadweep Islands

There are 36 islands in Lakshadweep archipelago, of which 10 are inhabited. The study focuses on the hydrogeological conditions prevailing in nine of these inhabited islands. Groundwater is the major source of fresh water and the well density is high in the range of 296 to 620 per km². The aspect ratios of these islands indicate that the shape of the islands have significant role on the stability of fresh water lens. The changes in water level do not reflect the real changes in the water resources as it is greatly influenced by tides. Moreover, the Ghyben-Herzberg relation in its ideal form does not hold good in these tiny oceanic islands. Hence, the rainfall recharge in the islands was assessed based on daily water budgeting. A relation between water surplus and annual rainfall could be established. This approach of recharge estimation could be applied for similar oceanic islands.     

The tectonic stress field and deformation pattern of northeast India,the Bengal basin and the Indo-Burma Ranges: A numerical approach

We performed numerical simulations to determine the contemporary maximum horizontal compressive stress (σ_Hmax) in the northeast India region, the Bengal basin (Bangladesh), and the adjoining Indo-Burma Ranges, with different boundary conditions. The regional tectonic stress was simulated using the finite element method (FEM) under the plane stress condition. Most of the study areas show NE–SW regional stress orientation, which is consistent with other stress indicators, such as earthquake focal mechanism solutions. The E–W trending Dauki fault, which separates the Shillong plateau to the north from the Bengal basin to the south, plays a major role in the stress distribution and regional deformation. This fault alone accommodates ～25% of the regional surface displacement rate of the study area. The fault pattern of the study area was also simulated using rheological parameters and the Mohr–Coulomb failure criterion. The simulated results reproduce the observed tectonic state of the area, including a strike-slip regime along the Dauki fault, in the southwestern part of the Bengal basin, and in the Tripura fold belt areas. The modeling indicates that the Brahmaputra valley to the north of the Shillong plateau and to the south of the Himalayan frontal thrust exhibits thrust/reverse faulting with a strike-slip component, and in the Indo-Burma Ranges, strike-slip faulting is predominant with a reverse fault component.     

Equivalent granular state parameter and undrained behaviour of sand�Cfines mixtures

State parameter defined using void ratio, e, and the steady-state line has been shown to be effective in predicting the undrained behaviour of sand. However, steady-state line for sand with fines is dependent on fines content. To overcome this problem, the concept of equivalent granular void ratio, e*, has been well investigated. However, the conversion from e to e* has been essentially a back-analysis process. A methodology for converting e to e* without the need of a back-analysis process was first presented. The concept of equivalent granular state parameter, ψ*, defined in terms of e*, and equivalent granular steady-state line was then developed. An extensive experimental study was conducted to investigate whether ψ* can capture the effects of fines content, and thus can be used to correlate undrained behaviour of sand–fines mixtures without the need of separately considering the effects of fines content. This study suggested that the effective stress path and deviatoric stress–strain responses in undrained shearing can be correlated with the ψ* value at the start of undrained shearing irrespective of fines content.     

Suspended sediment yield modeling in Mahanadi River,India by multi-objective optimization hybridizing artificial intelligence algorithms

River sediment produced through weathering is one of the principal landscape modification processes on earth.Rivers are an integral part of the hydrologic cycle and are the major geologic agents that erode the continents and transport water and sediments to the oceans.Estimation of suspended sediment yield is always a key parameter for planning and management of any river system.It is always challenging to model sediment yield using traditional mathematical models because they are incapable of handling the complex non-linearity and non-stationarity.The suspended sediment modeling of the river depends on the number of factors such as rock type,relief,rainfall,temperature,water discharge and catchment area.In this study,we proposed a hybrid genetic algorithm-based multi-objective optimization with artificial neural network(GA-MOO-ANN)with automated parameter tuning model using these factors to estimate the suspended sediment yield in the entire Mahanadi River basin.The model was validated by comparing statistically with other models,and it appeared that the GA-MOO-ANN model has the lowest root mean squared error(0.009)and highest coefficient of correlation(0.885)values among all comparative models(traditional neural network,multiple linear regression,and sediment rating curve)for all stations.It was also observed that the proposed model is the least biased(0.001)model.Thus,the proposed GA-MOOANN is the most capable model,compared to other studied models,for estimating the suspended sediment yield in the entire Mahanadi river basin,India.The results also suggested that the proposed GA-MOO-ANN model is unable to estimate suspended sediment yield satisfactorily at gauge stations having very small catchment areas whereas performing satisfactorily on locations having moderate to the large catchment area.The models provide the best result at Tikarapara,the gauge station location in the extreme downstream,having the largest catchment area.     

Impacts of pollution on coastal and marine ecosystems including coastal and marine fisheries and approach for management: a review and synthesis

The history of aquatic environmental pollution goes back to the very beginning of the history of human civilization. However, aquatic pollution did not receive much attention until a threshold level was reached with adverse consequences on the ecosystems and organisms. Aquatic pollution has become a global concern, but even so, most developing nations are still producing huge pollution loads and the trends are expected to increase. Knowledge of the pollution sources and impacts on ecosystems is important not only for a better understanding on the ecosystem responses to pollutants but also to formulate prevention measures. Many of the sources of aquatic pollutions are generally well known and huge effort has been devoted to the issue. However, new concepts and ideas on environmental pollution are emerging (e.g., biological pollution) with a corresponding need for an update of the knowledge. The present paper attempts to provide an easy-to-follow depiction on the various forms of aquatic pollutions and their impacts on the ecosystem and organisms.