Biodiversity of commercially important finfish species caught by mid-water and bottom trawls from two different coasts of Arabian Sea: Threats and conservation strategies

This study was conducted to estimate the diversity and the occurrence of commercially important finfish species collected by twenty fish sampling site of Sindh and Baluchistan coasts of the Arabian Sea in Pakistan from January to December 2019. Additionally, physicochemical characteristics of seawater were analyzed from these selected sites and found to be within suitable ranges required for fish growth and survive. A total of 81287 fish individuals were collected and identified as 49 species belonging to 26 families in our study. The most diversified family was Sparidae (13 species) followed by Carangidae and Lutjanidae (4 species), Mullidae, Serranidae, Ariidae (3 species), and Sciaenidae (2 species). The remaining 20 families were represented by only one species. The values of Shannon diversity index calculated for the four selected habitats revealed that high fish diversity was reported at Sonmiani Coast (H'=1.81), while less at Ormara Coast (H'=0.23). Likewise, Evenness index (E) was high at Sonmiani Coast (E=0.50) and less fish diversity was reported at Ormara Coast (E=0.06). Reducing risks to threatened marine species in coastal habitats also requires conservation actions at multiple scales. Thus, it was concluded that our study could be valuable in providing the more information’s regarding to the diversity of finfish species and their occurrence along the Pakistan Coast. Further, to better understand the effects, regular monitoring and conservation measures should be taken to mitigate the influence of anthropogenic activities and protect finfish diversity from further decline

Adsorption of Cationic Contaminants by Cyclodextrin Nanosponges Cross-Linked with 1,2,3,4-butanetetracarboxylic Acid and Poly(vinyl alcohol)

Cationic organic pollutants (dyes and pesticides) are mainly hydrosoluble and easily contaminate water and create a serious problem for biotic and abiotic species. The elimination of these dangerous contaminants from water was accomplished by adsorption using cyclodextrin nanosponges. These nanosponges were elaborated by the cross-linking between 1,2,3,4-butanetetracarboxylic acid and β-cyclodextrin in the presence of poly (vinyl alcohol). Their physicochemical characteristics were characterized by gravimetry, acid-base titration, TGA, 13C NMR, ATR-FTIR, Raman, X-ray diffraction, and Stereomicroscopy. The BP5 nanosponges displayed 68.4% yield, 3.31 mmol/g COOH groups, 0.16 mmol/g β-CD content, 54.2% swelling, 97.0% PQ removal, 96.7% SO removal, and 98.3% MG removal for 25 mg/L of initial concentration. The pseudo-second-order model was suitable for kinetics using 180 min of contact time. Langmuir isotherm was suitable for isotherm with the maximum adsorption of 120.5, 92.6, and 64.9 mg/g for paraquat (PQ), safranin (SO), and malachite green (MG) adsorption, respectively. Finally, the reusability performance after five regeneration times reached 94.1%, 91.6%, and 94.6% for PQ, SO, and MG adsorption, respectively.

Microbiome Development of Seawater-Incubated Pre-production Plastic Pellets Reveals Distinct and Predictive Community Compositions

Plastics of various chemistries pollute global water bodies. Toxic chemicals leach with detrimental and often unpredictable impacts on the surrounding ecosystems. We found that seawater leachates of plastic pre-production pellets from 7 recycle categories are acutely toxic to stage II barnacle nauplii; lethal concentration 50 (LC50s) were observed in 24-h leachates from dilutions ranging from 0.007 to 2.1 mg/mL of seawater. Based on previous observations that macro-organismal settlement on fouling management coatings of various toxicities can be used to predict the toxicity of the coating, we hypothesized that interaction of plastic pre-production pellets with emerging microbiomes would exhibit patterns indicative of the chemistry at the pellet surface. We used amplicon sequencing of bacterial 16S ribosomal RNA genes to characterize the microbiomes that developed from 8 through 70 days on pellets exposed to the same flowing ambient seawater. Diversity and composition of the microbiomes colonizing plastic pellets changed over time and varied with plastic type. Microbial taxa belong to taxonomic groups known to consume hydrocarbons, to be prevalent following marine oil spills, or to live on fouling management surfaces. Microbiomes were still distinct between plastic types at Day 70, suggesting that differences in the physicochemical characteristics of the underlying plastics continue to exert variable selection of surface microbial communities. A random forest-based sample classifier correctly predicted 93% of plastic types using microbiome compositions. Surface microbiomes have promise for use in forensically identifying plastic types and potential toxicities.

Assessment of faecal contamination in selected concrete and earthen ponds stocked with Clarias gariepinus

Background This study was carried out to monitor the levels of faecal pollution markers in catfish (Clarias gariepinus) and their growing waters in selected earthen and concrete ponds. Water and catfish samples were collected weekly in the months of February, March, April, May, June and July, 2019. The concentrations of enteric bacteria in the water and catfish samples were determined using membrane filtration and pour plate methods, respectively. The rate of bioaccumulation of faecal indicator bacteria was obtained by dividing the log concentration of each organism in catfish by the corresponding log concentration in the growing waters. Result The concentration of faecal coliforms in catfish samples from concrete and earthen ponds ranged from 1.41 to 2.28 log10 CFU/100 ml and 1.3 to 2.47 log10 CFU/100 ml respectively and in growing waters from the concrete and earthen ponds; 1.43 to 2.41 log10 CFU/100 ml and 1.50 to 2.80 log10 CFU/100 ml respectively. Faecal coliforms exhibited positive relationships with alkalinity in water samples from the earthen (r = 0.61) and concrete ponds (r = 0.62). Salmonella and faecal coliforms had the highest and least bioaccumulation in catfish raised in earthen pond, respectively, whereas Salmonella and enterococci had the highest and least bioaccumulation in catfish raised in concrete pond, respectively. Faecal coliforms and E. coli had the highest and least counts in water samples from the earthen pond during the dry and wet months, Salmonella and E. coli had the highest and least counts in water samples from the concrete pond during the dry and wet months. Conclusion There were high levels of bacterial faecal pollution markers in water and C. gariepinus from the earthen and concrete ponds. Physicochemical characteristics of the water and seasonality played major roles in the rate of bioaccumulation of the faecal pollution markers in C. gariepinus raised in the earthen and concrete ponds.

An in-situ conductometric apparatus for physicochemical characterization of solutions and in-line monitoring of separation processes at elevated temperatures and pressures

Specific conductance and frequency-dependent resistance (impedance) data are widely utilized for understanding the physicochemical characteristics of aqueous and non-aqueous fluids and for evaluating the performance of chemical processes. However, the implementation of such an in-situ probe in high-temperature and high-pressure environments is not trivial. This work provides a description of both the hardware and software associated with implementing a parallel-type in-situ electrochemical sensor. The sensor can be used for in-line monitoring of thermal desalination processes and for impedance measurements in fluids at high temperature and pressure. A comparison between the experimental measurements on the specific conductance in aqueous sodium chloride solutions and the conductance model demonstrate that the methodology yields reasonable agreement with both the model and literature data. A combination of hardware components, a softwarebased correction for experimental artifacts, and computational fluid dynamics (CFD) calculations used in this work provide a sound basis for implementing such in-situ electrochemical sensors to measure frequency-dependent resistance spectra.