Vertical profile of dissolved oxygen and associated water variables in the Pasur-Rupsha estuary of Bangladesh

Vertical profile of dissolved oxygen (DO) and associated water variables were measured in the head of the Pasur-Rupsha estuary of Bangladesh. Water samples were collected from two stations at 0.60 m depth intervals during high and low tides from July, 2016 to January, 2017. DO concentration was ranged from 6.0 to 8.6 mg/l with maximum two units of variation in the profiles of the stations and demonstrated an inconsistent stratification pattern. The observed stratification pattern was remarkably triggered by a relatively high concentration of DO in the bottom layer than that of the surface layer during both the high and low tides in most of the study periods. High rate of freshwater flow at the surface; existence of estuarine gravitational circulation with 5-15 m depth profile; and lack of consumers in the bottom due to the high deposition of sediment particles were found responsible for the relatively high concentration of DO at bottom and low in surface layer of the estuary. Water temperature, salinity, pH, phytoplankton density and transparency were ranged from 22 to 32 °C, 0-6 ppt, 7.0 to 8.5, 1000-23000 ind/l and 13-17 cm respectively considering the depth profiles in the study periods. Temperature and plankton density were found significantly (P < 0.000) correlated with DO while the pH and salinity did not show any significant (P > 0.3) correlation. The ecosystem process associated with the vertical profile of DO explained in this study will provide considerable advances in understanding the ecosystem dynamics of the Pasur-Rupsha Estuary of Bangladesh.

Quality of sources of drinking water and health among the hill tribe people of northern Thailand

Poor-quality drinking water can cause numerous health problems, particularly for people who are living with poor economic conditions, have a low educational status and have limited access to safe drinking water, such as the hill tribe people in Thailand. This study aimed to assess the quality of different sources of natural drinking water from the hill tribe villages in northern Thailand. Seventy-two drinking water samples from the hill tribe villages were collected and tested for biological, chemical and physical qualities, which were compared with the standard parameter values for safe drinking water according to the World Health Organization. Total coliform bacteria and fecal coliform bacteria, which represented the biological parameters, were detected in all samples. The physical parameters, which consisted of turbidity (36.1%), iron content (5.5%), color (2.7%) and pH (2.7%), exceeded the standard indications. However, the hazard quotient and hazard index values were less than 1. The hill tribe people are facing the problem of poor-quality drinking water, particularly in terms of biological and physical parameters that exceed the standard values. An effective program for improving access to safe water for the hill tribe people should be developed and implemented immediately.

Assessment of the surface water quality improvement during pandemic lockdown in ecologically stressed Hooghly River(Ganges) Estuary, West Bengal, India

The countrywide COVID-19 pandemic lockdown accomplished what aggressive plans could not do throughout the long-term cleaning of the Ganga River. Here, we illustrated Hooghly River surface water quality [physico-chemical parameters, biological parameters, dissolved heavy metals] improvement by analyzing eight sampling station before and during the lockdown. Because of shutdown of industrial units and individuals staying at home, a complete decrease in industrial wastes, contaminants, and self-purging of the stream improved significantly water quality by about 40% to 50%. Among dissolved heavy metals, the concentrations of Cd (50%), Pb (53%), demonstrated noteworthy variations during the lockdown. Diminishing trends were also observed for TDS (62%), and BOD (52%), with significant reduction in the total coliform (63%), faecal coliform (61%), notably. Principal component analysis and paired t-test signify the alteration of water quality. The study concludes that the aquatic ecosystem can be revived if wastewater, and anthropogenic activities are properly managed by environmental surveillance.

Influence of environmental conditions on the mercury levels of the sediment along the Balbina Reservoir, Brazilian Amazon

Mercury dynamics in hydroelectric reservoirs have been studied worldwide. In tropical reservoirs, especially in those of the Amazon, the influence of geochemistry on Hg levels along this aquatic system is not well understood. The main objective of the present study was to assess the influence of environmental conditions (physical and chemical water parameters, trace element concentrations of sediment and sediment geochemistry) on mercury levels of sediment along the Balbina Reservoir (Amazon basin, Brazil). Sediment was collected along the reservoir and in the main tributaries in May 2015 (n = 10). These samples were assessed for labile iron (LFe), manganese (LMn), aluminum (LAl) and mercury (LHg) concentrations, total mercury (THg) concentrations, organic matter (OM) content, and granulometry. Concentrations in the sediment were 4-212 (LFe), 2-460 (LAl), 180-613 (LMn), < detection limit-256 (LHg), and 12-307 μg kg^-1 dry weight (THg). In general, these concentrations decreased along the reservoir from upstream to downstream, reaching the lowest concentrations in the middle of the lake, and they increased in the sampling points near the dam. The lability and concentrations of mercury were influenced by the concentrations of LFe, LMn, LAl, and the granulometry and OM content of the sediment. Altogether, THg concentrations of sediments of the Balbina Reservoir encompass the range of concentrations of other reservoirs or natural lakes in the Amazon basin (from ten to a few hundred μg kg^-1 dry weight).

Prevalence, site and tissue preference of myxozoan parasites infecting gills of cultured fingerlings of Indian major carps in District Fatehgarh Sahib, Punjab (India)

A study was undertaken to investigate the prevalence rate, site preference and extent of damage caused by myxosporidian parasites in Punjab, India. During the 6 months study, 600 carp fingerlings belonging to 4 genera i.e. Labeo rohita Hamilton, Cirrhinus mrigala Hamilton, Catla catla Thail and Carassius carassius were randomly collected from the polyculture nursery ponds located in different villages District Fatehgarh Sahib, Punjab. Organs such as fins, scales, gills, intestine, kidney, and eye-ball were examined for the presence of myxozoan parasites. In this study, gills of 321 (53.50%) were found to be infected with as many as 10 species of myxosporean parasites belonging to the genus Myxobolus. Gills were examined for the presence of plasmodia and infected organs were processed for histology. The gill plasmodial index (GPI) was counted for all the 10 species and this revealed a mild to severe infection was recorded. M. knobii, M. majraiensis, M. markiwi, M. naini, M. rocatlae, M. vascularis and M. venkateshi formed intralamellar vascular type of plasmodia (LV₁), M. nanokiensis formed (LV₃) and M. potularis and M. slendrii formed intrafilamental type of plasmodium (FV₂). Out of 231 infected fishes, mixed infection was recorded in 44 fishes (13.70%), which exhibited biparasitism and polyparasitism. No infection was recorded in exotic carp i.e. C. carassius. Physicochemical parameters of water were also recorded for the period of 6 months comprising 4 months of winter and 2 months of spring. The present study indicated that the prevalence of myxozoan parasite was 43% in November (24.0 °C) and increased to 54% with the decrease in temperature (22.65 °C).

Comparative study of the effects of a small-scale trout farm on the macrozoobenthos, potamoplankton, and epilithic diatom communities

Trout farms are one of the major sources of pollution of highland streams and rivers, which are very sensitive ecosystems otherwise scarcely influenced by human activities. A trout farm with low annual production was chosen for comparative monitoring of its effects on the macrozoobenthos, epilithic diatom, and potamoplankton communities in the receiving stream. Research was conducted every 2 months during a period of 1 year (one control point and three localities downstream from the farm). The fish farm discharge induced moderate alteration of environmental factors in the receiving watercourse, viz., significant increase of the ionized and un-ionized ammonia fraction, dissolved oxygen concentration, and biological oxygen demand. Species richness and Simpson's diversity index did not change in any of the communities. Correspondent analysis of potamoplankton community composition clearly showed trout farm effects, thereby indicating the need for reevaluation of saprobic valence values for potamoplankton species. The complete lack of influence of the trout farm discharge on the epilithic diatom community is probably due to absence of significant changes of phosphorus concentration in the receiving stream. Effects of the trout farm on the macrozoobenthos community were further characterized by 14 additional indices. The percentages of Chironomidae larvae, shredders, and total collectors; ratio of shredders to collectors; and the family biotic index are suggested as candidates for future multimetric index for measuring of trout farm influence.

Effects of Clove Oil and Lidocaine-HCl Anesthesia on Water Parameter during Simulated Transportation in the Marine Medaka, Oryzias dancena

Optimum concentrations of anesthetic clove oil and anesthetic lidocaine-HCl were determined for a species of adult marine medaka, Oryzias dancena, over a range of salinity conditions, and investigated in a transport simulation experiment by analyzing various water and physiological parameters. Research indicated that the higher the concentration of anesthetic at each salinity, the shorter the anesthesia time at each salinity. At each concentration, fish were anesthetized slower at water salinities over 10 ppt (P<0.05). Anesthesia time at 10 ppt was faster than any other salinity. In 10 ppt salinity, the dissolved oxygen (DO) concentrations and respiratory frequencies of the clove-oil-administered groups decreased until 48 hours (P<0.05), whereas the NH₄⁺ and CO₂ concentrations increased until 48 hours (P<0.05). In same period, the DO, NH₄⁺, and CO₂ concentrations and respiratory frequencies all decreased as the clove oil concentration increased (P<0.05). The trends in the DO, NH₄⁺, and CO₂ concentrations and respiratory frequencies in the lidocaine-HCl-administered groups were similar to those in the clove-oil-administered groups. In conclusion, clove oil and lidocaine-HCl are effective anesthetics, improving the transportation of the marine medaka. The results from this study will contribute to safe laboratory handling of the marine medaka, which are commonly required by many research studies and experiments.

Anesthetic Effect and Physiological Response in Olive Flounder (Paralichthys olivaceus) to Clove Oil in a Simulated Transport Experiment

The optimum concentrations of clove oil as an anesthetic for olive flounder (Paralichthys olivaceus) and the stress response of the fish to clove oil anesthesia were determined over a range of water temperatures, and investigated in a simulated transport experiment using analysis of various water and physiological parameters. While the time for induction of anesthesia decreased significantly as both the concentration of clove oil and water temperature increased, the recovery time increased significantly (P<0.05). The plasma cortisol concentration in fish at each temperature increased significantly up to 12 h following exposure (P<0.05), then decreased to 48 h (P<0.05). The DO dissolved oxygen concentrations, pH values, and the fish respiratory frequencies decreased over 6 h following exposure to clove oil in all experimental groups (P<0.05), whereas the NH₄⁺ and CO₂concentrations in all experimental groups increased up to 6 h (P<0.05). The pH values and DO concentrations increased with increasing clove oil concentration (P<0.05) in the 6 h following exposure, and the CO₂ and NH₄⁺ concentrations and the respiratory frequencies decreased with increasing clove oil concentration (P<0.05). The results of this experiment suggest that clove oil reduced the metabolic activity of olive flounder, thus reducing NH₄⁺ excretion and O₂ consumption. In conclusion, clove oil appears to be a cost-effective and efficient anesthetic that is safe for use and non-toxic to the fish and users. Its use provides the potential for improved transportation of olive flounder.