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Contamination of aquatic ecosystems by various sources has become a major worry all over the world. Pollutants can enter the human body through the food chain from aquatic and soil habitats. These pollutants can cause various chronic diseases in humans and mortality if they collect in the body over an extended period. Although the phytoremediation technique cannot completely remove harmful materials, it is an environmentally benign, cost-effective, and natural process that has no negative effects on the environment. The main types of phytoremediation, their mechanisms, and strategies to raise the remediation rate and the use of genetically altered plants, phytoremediation plant prospects, economics, and usable plants are reviewed in this review. Several factors influence the phytoremediation process, including types of contaminants, pollutant characteristics, and plant species selection, climate considerations, flooding and aging, the effect of salt, soil parameters, and redox potential. Phytoremediation’s environmental and economic efficiency, use, and relevance are depicted in our work. Multiple recent breakthroughs in phytoremediation technologies are also mentioned in this review.

In this study, the nutritional and phytochemical components of red seaweed, Gracilariopsis longissima, were assessed in relation to the effects of various drying methods (freeze, oven, and sun). Gracilariopsis longissima’s proximate composition differed significantly (P < 0.05) among the three drying techniques, with freeze-dried samples having significantly greater protein (30.63 ± 0.90% dry weight) and lipids (1.49 ± 0.05% dry weight) contents. Except for phosphorus and sulfur, the mineral concentrations were likewise considerably greater in the freeze-dried samples. The total amino acids (30.48 ± 0.06% dry weight) and fatty acids contents were substantially greater (P < 0.05) in the freeze-dried samples. In freeze-dried samples, the levels of essential amino acids (18.92 ± 0.02% dry weight) and unsaturated fatty acids (54.08 ± 0.07%) were substantially greater (P < 0.05). When compared to oven- and sun-dried samples, the total phenolic content (88.70 ± 2.19 mg GAE/g dry weight) and the flavonoid content (71.46 ± 2.17 mg QE/g dry weight) of freeze-dried samples was also substantially higher. Among the three distinct drying techniques used, the freeze-drying technique kept G. longissima’s higher nutritional and phytochemical components.

Seaweed is known to empower a mass embodiment of bioactive compounds with potent health convenience. Current perusals intended to explore the total phenolic content (TPC), total flavonoid content (TFC), and antioxidant dynamism of red seaweed, Gracilariopsis longissima as pervaded by different solvents and solvent fractions (methanol, ethanol, acetone, and water). The extracts dynamism to antioxidant were assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH), and 2, 2 ’ -Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Here, 100% methanolic and acetonic extract asserted maximal extent of total phenolic and flavonoid content (88.70 mg of gallic acid/g and 75.06 mg of quercetin/g respectively) in a sufficiently great way. However, 50% methanolic DPPH and ABTS solution (74.32%, IC 50  = 0.027 mg/ml and 70.51%, IC 50  = 0.033 mg/ml) significantly demonstrated the highest percentage of inhibition and antioxidant activity compared to other solvents. Gracilariopsis longissima also contains a high amount of protein (30.63%) and minerals especially potassium (4.47%) and calcium (2.54%). According to the results of this study, G. longissima extracts prepared using 100% methanol as a solvent showed higher total phenolic and total flavonoid quantity and 50% methanol as a solvent showed higher antioxidant potential. These properties will be valuable for nutritional food and medicinal uses.

Seasonal changes in feeding habits of hilsa (Tenualosa ilisha) were studied monthly in 2019 in the upper Meghna estuary, Bangladesh, through gut content analyses. Tychoplanktonic diatoms followed by copepods were abundant in all months and size groups of hilsa. The inverse relationship between niche breadth and relative length of the gut revealed hilsa consume a variety of food at their early stages while their feeding habit changes towards diatoms during the adult stage with the development of gill rakers. Young hilsas prefer mostly tychoplanktonic diatoms (Aulacoseira sp., Triceratium sp., Nitzschia sp., Synedra sp., and Coscinodiscus sp.) and copepods (Pseudodiaptomus sp.). However, adult hilsas rejected Aulacoseira sp. during their spawning season. Ingested sand grains correlated with tychoplankton, revealing their food value from epipelic microalgae and bacteria clinging to them and epibenthic foraging by young hilsas. Thus, this study revealed that young hilsas primarily feed on tychoplanktonic diatoms and copepods from water and near bottom of the upper Meghna estuary during January to June while later stages with the development of gill rakers allow hilsas to feed on planktonic diatoms. Epibenthic feeding needs to be considered more fully in evaluating the biology of hilsa and, perhaps, other clupeids, and in evaluating possible human impacts on this foraging habitat.

In the Sandha river of Bangladesh, we investigated the temporal and geographical fluctuation in species of fish composition and diversity. The extent of our understanding of the fish variety in this river varies greatly on both a temporal and a geographical scale. From July 2021 to June 2022, fish specimens were gathered from five stations using various conventional fishing methods. During the study period, 5118 individuals from 67 species were collected which include 8 orders, 24 families, and 54 genera. Cypriniformes made up the majority of the order (32.84%), whereas Beloniformes and Tetraodontiformes made up the least number of species (1.49% each). Six species were listed as endangered (8.96%), seven as vulnerable (10.45%), nine as near threatened (13.43%), forty-three as least concern (64.18%), one with data deficient (1.49%), and one as not evaluated (1.49%) in Bangladesh. In order to quantify the temporal and geographical changes in community composition, diversity indices were calculated and put to use. Three (temperature, humidity, and rainfall) out of the four environmental factors (temperature, humidity, rainfall, and photoperiod) had a big impact on how species were distributed. At a similarity level of 79% and 75.5% separation, 2 substantial clusters were seen in the case of stations and 2 large clusters were detected in the case of months, respectively. However, at a similarity threshold of 20% separation, three different groups of fish species were found. Our research offers the most recent status data on fish distribution in the Sandha river. The knowledge acquired from this research is crucial for creating protection and management plans that will promote the long-term viability of fishery resources in the Sandha river and its nearby coastal tributaries.

Homestead ponds are small seasonal ponds that are rarely utilized for fish farming. Culturing fish in these small ponds can boost household fish consumption and cash inflow. The availability of nutrients in the water and sediment, however, plays a significant role in the pond’s natural productivity. This study was conducted to assess nutrient contents and some key physical parameters in the bottom sediments of 30 homestead ponds from the central coast along the Northern Bay of Bengal. Analyses of results showed the average values (±SD) of temperature, pH, electrical conductivity, organic matter (OM), organic carbon (°C), nitrogen (N), phosphorus (P) and sulphur (S) were 17.8 ± 1.12 °C, 7.29 ± 0.11, 0.41 ± 0.09 mS/cm, 29,615.48 ± 10,528.9 mg kg−1, 11,958 ± 6107 mg kg−1, 1030.6 ± 252 mg kg−1, 17.1 ± 13.5 mg kg−1 and 32.6 ± 19.7 mg kg−1 during winter and 27.2 ± 1.81 °C, 6.73 ± 0.12, 0.38 ± 0.17 mS/cm, 19,100.01 ± 13,739.07 mg kg−1, 11,079 ± 7969 mg kg−1, 955 ± 229.4 mg kg−1, 26.6 ± 20.2 mg kg−1 and 23.4 ± 15.9 mg kg−1 during pre-monsoon, respectively. One-way ANOVA revealed no significant differences in the mean value of sediment quality parameters among the selected ponds (p > 0.05) except for phosphorus in the winter season (p < 0.05). The sediment quality variables were found to be in the suitable range for fish culture. Pearson’s correlation coefficient values (r) showed that only organic carbon and nitrogen had a strong significant correlation with organic matter (p < 0.05). Based on Cluster Analysis (CA), two major associations among the nutrients were attained at a 15% similarity level: C, OM, and N in one cluster and P and S in another. The findings showed that the parameters were within the preferable range for aquaculture, and the homestead ponds are average productive ponds.

This study investigates the influence of water physicochemical properties on the growth, production, nutritional composition, and antioxidant properties of Gracilaria tenuistipitata , cultivated at two different sites (Gangamati and Hazipur) along the northern Bay of Bengal, Bangladesh. The water quality parameters were monitored weekly. Results revealed that the Gangamati site is characterized by significantly higher ( p < 0.05) salinity (14.75 ± 4.89 ppt), transparency (60.50 ± 9.57 cm), and total dissolved solids (6154.90 ± 1492.50 mg/L) compared to the Hazipur site. The Gangamati site significantly ( p < 0.05) outperformed the Hazipur site in terms of daily growth rate and production. Furthermore, proximate composition analysis indicated significantly higher ( p < 0.05) protein (25.06 ± 0.90% DW), lipid (1.22 ± 0.05% DW), fiber (7.03 ± 0.76% DW), and carbohydrate (38.41 ± 0.80% DW) contents in seaweed from the Gangamati site. The mineral content of G. tenuistipitata was also influenced by the culture site significantly ( p < 0.05). Amino acid analysis demonstrated superior protein quality in Gangamati seaweed, with significantly higher levels of essential (77.286 ± 0.06 mg/g) and nonessential (95.243 ± 0.07 mg/g) amino acids than the Hazipur site. The fatty acid profiles varied significantly between the two sites, with seaweed from the Gangamati site exhibiting higher levels of unsaturated fatty acids (41.27 ± 0.05%) compared to Hazipur, indicating superior nutritional lipid quality indices. Bioactive compounds were significantly higher ( p < 0.05) in Gangamati seaweed, along with higher antioxidant activity. Overall, these results indicate that the Gangamati estuary provides a better environment for the cultivation of G. tenuistipitata , resulting in seaweed with superior nutritional and bioactive properties.

The studied area is the single largest fishery in Bangladesh. The present work was conducted at two points of the Padma River (Sureshwar and Tarabunia) from July 2019 to June 2021 to monitor the efficiency of the 5 Hilsa sanctuary. Proportion of spent rate, length frequency, larvae and Jatka abundance, CPUE of larvae, the length-weight relationship of Jatka, plankton composition, and physico-chemical parameters of water were assessed and found adequate in the Hilsa sanctuary.

The Meghna River, vital for Bangladesh’s ecosystems and livelihoods, faces threats from urbanization, agriculture, industrialization, pollution, and climate change. This study examines the basin’s spatio-temporal dynamics, focusing on hydro-physico-chemical properties (temperature, pH, dissolved oxygen, salinity) and bio-resources (phytoplankton, zooplankton, and benthic macroinvertebrates). Field surveys, laboratory analyses, and satellite imagery revealed consistent patterns, highlighting the ecosystem’s vulnerability and the urgent need for conservation strategies to sustain ecological balance and livelihoods.

Plankton is essential to estuarine food webs, providing key food for species like fish larvae, and understanding their dynamics helps us comprehend ecological interactions and energy transfer in aquatic ecosystems. This study examined the plankton community structure, diversity, variability and the environmental variables of water that influenced these communities in a freshwater-dominated estuary along the Northern Bay of Bengal during the dry season. A variety of tools were employed, including a dissecting microscope, a Sedgwick-Rafter cell, and a Hanna multi-parameter meter, to obtain detailed and comprehensive data. From the analyses, in total 37 genera of phytoplankton belonging to 11 classes such as Bacillariophyceae (66%), Coscinodiscophyceae (28%), Fragilariophyceae (1%), Euglenophyceae (1%), Cyanophyceae (1%), others (3%) were recorded. Zooplankton, consisting of multicellular organisms, was represented by 11 genera across five classes, with Monogononta (53%) and Insecta (29%) being the most prevalent. Phytoplankton exhibited a mean abundance of 180,000 ± 20,200 cells l −1 whereas zooplankton showed a mean abundance of 3,000 ± 200 cells l −1 . The diversity indices (H′), evenness (J′) and dominance (D) ranged from 1.188 ± 0.015 to 0.19 ± 0.006, 0.9377 ± 0.002 to 0.5118 ± 0.006, 0.365 ± 0.001 to 0.143 ± 0.002 respectively, suggested low to moderate plankton diversity with a suppressed community and moderate to high dominance in the river water. Based on the similarity percentage (SIMPER) and analysis of similarity (ANOSIM), Phytoplankton and zooplankton varied significantly between stations while non-metric multi-dimensional scaling (nMDS) indicated greater consistency in phytoplankton communities across stations compared to zooplankton. Furthermore, Pearson’s correlation coefficient (rs) and canonical correspondence analysis (CCA) identified transparency, sulfates, dissolved oxygen, conductivity, TDS, pH, and salinity as major influencers of plankton abundance; nitrate had a moderate effect. Spearman’s rank correlations showed significant positive (p < 0.05) correlations between diversity indices and environmental variables. Future research should focus on long-term monitoring and the potential impacts of environmental changes on plankton communities.