The shells of freshwater snails are discarded as waste, which qualify as biological materials with prospective multiple uses. To substantiate this proposition, an attempt was made to elucidate the physical and chemical properties of the shells of three freshwater snails, namely, Bellamya bengalensis , Pila globosa , and Brotia costula . The shells were prepared for electron microscopy and assessment of the calcium carbonate content, apart from the Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and nanoindentation studies. The results indicated that the calcium carbonate content ( y ) of the shells ranged between 87 and 96% of the total weight ( x ) and complied with a power regression equation: y = 0.801 x 1.016 ; R 2 = 0.994; r = +0.998; P < 0.001. Observations through SEM depicted different snail species-specific arrangement patterns of calcium carbonate crystals in the diverse layers of shells. The XRD, FTIR, and EDS observations revealed the dominance of the aragonite form of the calcium carbonate crystal in the microstructures of each snail shell with the occurrence of different shell surface functional groups. The Brunauer–Emmett–Teller analysis elucidated the surface textures of shell dust taken from each snail species; in addition, the nanohardness properties indicate the shells as a tough biocomposite exoskeleton. Species-specific variations in the shell morphology, microstructure, and calcium carbonate content were prominent for the three freshwater snails considered for the study. Nonetheless, the physical and chemical properties substantiate that the shells of B. bengalensis , P. globosa , and B. costula qualify as biological materials for sustainable use in various fields including bioremediation, biocatalyst, biomedical applications, and a source of lime. Since the shells of the freshwater snails are discarded as aquaculture waste, subsequent use as a biological material will support the “waste made useful” paradigm in sustainability, both from ecological and economic perspectives.
Freshwater mussel shells: prospects as multifunctional biological material.
Waterbirds constitute a prominent biota and reflect the ecosystem health and functionality of the freshwater wetlands. Documentation of the bird species assemblages of wetlands is therefore carried out as a part of monitoring of wetlands from a sustainability viewpoint. Using the emerging wetland of Purbasthali, West Bengal, India, as a model study area, the diversity of the associated bird species was estimated to supplement necessary information for conservation management of birds and ecosystems. The point count method was applied to count the waterbirds from each sighting location with a 25 m radius covering 360° arc and the counting period lasted 10 min for each site, and counts were made in the winter of 2016/2017. The data on the waterbirds encountered were recorded and subjected to diversity analysis, including the residential status, global population trend and feeding guilds. Apparently, the wetland was considered as suitable habitat for 27 waterbird species, which could be grouped under 24 genera, 10 families and 5 orders. Among these, the family Anatidae with maximum relative density and abundance dominated in the wetland. Out of the 27 recorded species, 5 species were widespread winter visitors, 3 species widespread resident, as well as, widespread winter visitors and 2 species were sparse local winter visitors. A globally near threatened species, the Black-headed Ibis (Threskiornis melanocephalus) was very common in the sampling sites. The waterbird assemblage in the wetland was dominated by carnivores followed by omnivores and herbivores. The abundance of the waterbirds with considerable variations in the foraging guild reflects availability and exploitation of multiple resources of the Purbasthali wetlands. Prominence in the differences in relative abundance of the different waterbirds could be linked with the heterogeneity in the habitat quality. The present information on waterbird assemblage calls for appropriate measures for conservation of the species and appropriate management of Purbasthali wetlands.
The transportation infrastructures like railway tracks and roads bear negative impacts on natural environment. However, the opposite effects are also true in some instances where the man-made constructions have positive effect on faunal assemblages. This proposition was justified through the assessment of bird species using railway stations as model man-made structures in an urban-rural gradient, in the suburbs of Kolkata, India. During the entire study period along nine different railway stations, a total of 43 bird species belonging to 12 orders and 26 families were observed. Among these, the order Passeriformes was predominant in its species composition having 18 different species from 11 different families. In urban railway stations, a total of 23 bird species under 22 genera and 14 families were observed. In suburban railway stations, a total of 35 bird species under 32 genera and 22 families were documented. The railway stations from rural region showed the maximum number of species and abundance of bird families, where a total of 36 bird species under 32 genera and 23 families were observed. The railway stations from the suburban and rural regions were more similar in species composition. Irrespective of the locations, during the entire study period, the House Crow (Corvus splendens) was the dominant species followed by the Common Myna (Acridotheres tristis). About 18 bird species exhibited a decreasing population trend observed through the global population trend analysis. In all the railway stations, the abundance of omnivores were dominant while, the number of granivores were higher in the rural regions and the nectarivores were absent in the urban regions. It was apparent that the railway stations bear a positive effect on the bird species assemblages, which can be sustained through proper environmental management planning inclusive of urban greening.
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