Search

Bangladesh is a deltaic country in Asia, and its riverine systems ultimately drain into the Bay of Bengal. Plastic is a severe environmental issue for coastal-marine ecosystems due to the indiscriminate usage and discarding of plastic items in the upstream river that eventually find their route into the Bay of Bengal. Microplastics (MPs) are widespread pollutants in almost all environmental compartments, including aquatic environments. This study aimed to quantify and understand the distribution of microplastics in surface water and sediments of the river Karnaphuli, a tidal confluence river adjacent to the Chattogram seaport city of Bangladesh, a highly inhabited and industrial area on the southeast coast of the Bay of Bengal. A manta trawl net (300-µm mesh size) was used to collect surface water samples, while an Ekman dredge was used to collect sediment samples. The concentrations of microplastics in the surface water of the river Karnaphuli during late monsoon, winter, and early summer were recorded to be 120,111.11, 152,222.22, and 164,444.44 items/km2, respectively, while in sediments, those were recorded to be 103.83, 137.50, and 103.67 items/kg, respectively. A higher abundance of microplastics was observed in downstream surface water (228,888.88 items/km2) and sediments (164.17 items/kg). Smaller sizes (0.3 to 0.5 mm) of microplastics were predominant, fibers or threads were the frequent types, and black was the most common color in the river Karnaphuli. The Fourier transform infrared analysis revealed that polyethylene terephthalate (surface water: 22%, sediments: 19%), polyamide (surface water: 15%, sediments: 13%), polyethylene (surface water: 12%, sediments: 18%), polystyrene (surface water: 13%, sediments: 11%), and alkyd resin (surface water: 13%, sediments: 10%) were the most prevalent polymers in the river Karnaphuli. Moreover, there was a moderate positive correlation between MPs abundance in surface water and sediments. Therefore, improved long-term research (in different seasons with horizontal and vertical monitoring) is necessary in order to accurately determine the flux of microplastics from the river Karnaphuli to the Bay of Bengal. [ABSTRACT FROM AUTHOR]

This study examines the online niches of English-language newspapers in Bangladesh by analyzing stories and user engagement on the Facebook pages of five highest circulated newspapers. Based on the theory of the niche, this study analyzed data on 17,687 Facebook posts downloaded programmatically. Results indicate that users read these newspapers for in-depth news stories and features on diplomacy, national security, lifestyle, science, technology, and international events. The study identified a gap between what these newspapers offer and what their users want. [ABSTRACT FROM AUTHOR]

The purpose of this research was to analyze the underlying mechanisms and contributing factors related to the seasonal dynamic of harmful algal blooms in a shallow eutrophic pond, Bangladesh during September 2005-July 2006. Two conspicuous events were noted simultaneously throughout the study period: high concentration of phosphate-phosphorus (>3.03; SD 1.29 mg l) and permanent cyanobacterial blooms {>3,981.88 × 10 cells l (SD 508.73)}. Cyanobacterial blooms were characterized by three abundance phases, each of which was associated with different ecological processes. High nitrate-nitrogen (>2.35; SD 0.83 mg l), for example, was associated with high cyanobacterial abundance, while low nitrate-nitrogen (0.36; SD 0.2 mg l) was recorded during moderate abundance phase. Extremely low NO-N/PO-P ratio (>3.55, SD 2.31) was recorded, and all blooming taxa were negatively correlated with this ratio. Cyanobacterial blooms were positively correlated with temperature ( r = 0.345) and pH (0.833; p = 0.05) and negatively correlated with transparency ( r = − 0.956; p = 0.01). Although Anabaena showed similar relationship with water quality parameters as cyanobacteria, the co-dominant Microcystis exhibited negative relationship with temperature ( r = − 0.386) and nitrate-nitrogen ( r = − 0.172). This was attributed to excessive growth of Anabaena that suppressed Microcystis's growth. Planktothrix was the third most dominant taxa, while Euglena was regarded as opportunistic. [ABSTRACT FROM AUTHOR]

Worldwide the quality and high price of fish feed are an important issue for sustainable aquaculture that warranted the development of low-cost culture systems utilizing natural resources. An experiment was conducted in a tidally inundated wetland in the coastal region of Bangladesh utilizing naturally grown floating grass, Hygroryza aristata as a fish feed. The experiment was conducted under three treatments each with three replications for one year. In treatment one, the grass was planted and grown on the bottom soil before stocking of fish (T1; in-situ grass); in treatment two, the grass grown elsewhere was collected and supplied as fish feed in raw condition (T2; ex-situ grass); and in treatment three, the fishes were fed with commercial floating fish feed (T3; control). Grass carp, common carp, black carp and tilapia were reared at the ratio of 6:1:1:2 with a total stocking density of 12,350 fish ha−1. The survival rate, growth (weight gain, % weight gain and specific growth rate, SGR), production and cost and benefit of fish production were calculated. The survival of the fish varied from 76.00% to 85.14% irrespective of species. The weight gain, % weight gain and SGR of grass carp and common carp were highest in in-situ grass, followed by ex-situ grass and control, whereas tilapia showed the highest growth in control, followed by in-situ and ex-situ grass. The total production of fish was highest in in-situ grass (9060.70 kg ha−1 year−1), followed by control (8469.70 kg ha−1 year−1) and ex-situ grass (8001.23 kg ha−1 year−1). The net economic benefit and benefit-cost ratio were also highest in in-situ grass (US$ 17,994.96 ha−1 and 4.52), followed by ex-situ grass (US$ 14,278.30 ha−1 and 2.78) and control (US$ 4818.63 ha−1 and 0.32). The present findings indicate that coastal wetlands of Bangladesh can be used for commercial aquaculture using the H. aristata floating grass as fish feed, which may play an important role in the livelihood development of the people living in the coastal areas of the country. • Coastal tidal wetlands can be used for commercial aquaculture using Hygroryza aristata floating grass as fish feed. • H. aristata floating grass plantation as feed before fish stocking reduced production cost 3.82 times and achieved BCR of 4.52. • H. aristata floating grass may be an alternative important plant protein source in the feed industry formulating fish feed in near future. [ABSTRACT FROM AUTHOR]

In Bangladesh the exposure of millions of inhabitants to water from (shallow) tube wells contaminated with high geogenic loads of arsenic is a major concern. As an alternative to the costly drilling of deep wells, the return to the use of surface water as a source of drinking water is considered. In addition to the well-known hazards of water borne infectious diseases associated with the use of surface water, recently the potential public health implications of toxic cyanobacteria have been recognized. As a first step towards a risk assessment for cyanotoxins in Bangladesh surface waters, seston samples of 79 ponds were analysed in late summer 2002 for the presence of cyanobacteria and microcystins (MCYST), the most frequently detected cyanobacterial toxins worldwide. Microcystins could be detected in 39 ponds, mostly together with varying abundance of potentially microcystin-producing genera such as Microcystis, Planktothrix and Anabaena. Total microcystin concentrations ranged between <0.1 and > 1,000 microg l(-1), and more than half of the positive samples contained high concentrations of more than 10 microg l(-1). The results clearly show that concentrations of microcystins well above the provisional WHO guideline value of 1 microg l(-1) MCYST-LR can be frequently detected in Bangladesh ponds. Thus, an increasing use of surface water for human consumption introduces a risk of replacing one health hazard by another and therefore needs to be accompanied by cyanotoxin hazard assessments.