Reduction In Water pH Research Articles

Metals and biogenic substances’ migration ability in the «bottom sediments – water» system under natural and experimental conditions


 
 
 The paper considers the results of long-term studies on some chemical elements’ migration (Al, Fe, Ti, Mn, Cu, Zn, Pb, N, P, Si) in the «bottom sediments – water» system of surface water bodies under the effect of different aquatic environment factors. The greatest effect is made by water bodies’ oxygen regime, pH, and presence of dissolved organic substances, in particular humic substances. The migration of manganese, iron, inorganic nitrogen and phosphorus from bottom sediments is controlled mostly by oxygen regime. Migration of these chemical elements significantly increases, when there is oxygen deficiency and anaerobic conditions are formed in the bottom water layer. It has been observed in both natural and experimental conditions. Man- ganese concentration increases in bottom water in 25–50 times, iron – in 1.3–13, inorganic nitrogen – in 5.3–19.3, and inorganic phosphorus – in 2.8–23 times. The dissolved oxygen concentration hardly has any effect on the migration of aluminium, titanium, copper, zinc, lead, and silicon from bottom sediments into the water. The chemical elements’ migration is significantly affected by a decrease in pH of water contacting with bottom sediments and the presence of humic substances in it. High humic substances concentrations promote a reduction in water pH and oxygen content, which is consumed for their oxidation. A case study of several water bodies illustrates the cumulative effect of water pH lowering, anaerobic conditions at the solid and liquid phases’ interface, as well as complexation with humic substances on chemical elements’ migration from bottom sediments. Experimental modeling has shown that the metal migration from bottom sediments occurs both due to their labile fractions and complex compounds with dissolved organic matter, especially with humic substances of low molecular weight (≤2.0 kDa). The share of the metal labile fraction gets higher, when water pH decreases. Under recent climate change, the probability of water’s secondary pollution with different chemicals increases significantly in summer. This is mainly caused by oxygen deficiency, water pH lowering, and reducing conditions at the «bottom sediments – water» interface with hydrogen sulphide being formed. This is especially true for highly eutrophic water bodies subject to human impact. The aquatic environment toxicity can get considerably higher due to the migration of chemicals with strong toxic properties from bottom sediments, as well as labile metal fractions, marked by higher bioavailability for hydrobionts.
 
 

The impact of water pH on association preferences in fish

AbstractAcidification of lakes and rivers, as a consequence of anthropogenic interference, can cause fundamental changes to biological and ecological processes. One of the main consequences of a reduction in water pH for aquatic organisms is the disruption of their chemosensory abilities, as the detection of chemical cues underpins a wide range of decision‐making processes; for example, a reduction to low pH has been shown to interfere with predator avoidance and the detection of foraging cues. Moreover, aquatic organisms are known to make widespread use of chemical information to inform their social behaviour, although we have a comparably poor understanding of how this is impacted by water acidification, especially their shoaling behaviour. Using a standard behavioural assay, we therefore investigated the impact of low water pH on the social interactions mediated by diet‐derived chemical cues in three‐spined sticklebacks (Gasterosteus aculeatus), by quantifying social behaviour in water that varied either experimentally or naturally in pH. In both cases, we predicted that association patterns would be disrupted by low pH conditions, as reduced pH has shown to interfere with the perception of chemical cues in other non‐social contexts. Consistent with this prediction, our results demonstrate that an acute, short‐term reduction in water pH caused a breakdown in the diet‐mediated social interaction patterns seen in more alkaline water, although, interestingly, the pattern of associations for fish tested in naturally acidic water was both more complex and in a direction that was precisely contrary to our predictions. Overall, the findings provide insights into the potential effects of an acute reduction in water pH on fish communication and social interaction patterns, which may have implication for various individual, group, population and community‐level processes.

Effect of Carbon Dioxide-Induced Water Acidification on the Physiological Processes of the Baltic Isopod Saduria entomon

Survival, behavior, hemolymph pH, osmolality, and chloride ion concentration as well the total metabolic rate (heat dissipation rate) of the isopod Saduria entomon from the brackish Baltic Sea were investigated after exposure to carbon dioxide-induced water acidification (pH, 7.5, 7.0, and 6.5; control pH, 8.2) keeping other parameters constant (temperature, 10°C; salinity, 7). The short-term (12 h per each pH treatment) exposure to carbon dioxide-induced water acidification did not cause significant changes (P < 0.05) in the resting metabolic rate or the scope of activity in S. entomon; however, high interindividual variability was observed. The 2-wk exposure to lowered pH values did not affect either the activity of the isopods or their survival rate significantly (P > 0.05), which was greater than 90% in all pH treatments. The hemolymph pH increased significantly (P < 0.05) with a decrease of water pH from a control pH of 8.2 down to a pH of 7.0. Hemolymph osmolality increased significantly (P < 0.05) at pH 7.5, but exposure to pH 7.0 did not cause further increase in this parameter. Reduction of water pH did not affect the hemolymph chloride ion concentration. Obtained results indicated that S. entomon is adapted to large fluctuations of carbon dioxide levels in the water primarily to compensate for acid—base disturbances without additional energetic costs.

Detrimental effects of reduced seawater pH on the early development of the Pacific abalone

The hatching process of the Pacific abalone Haliotis discus hannai was prolonged at a pH of 7.6 and pH 7.3, and the embryonic developmental success was reduced. The hatching rate at pH 7.3 was significantly (10.8%) lower than that of the control (pH 8.2). The malformation rates at pH 7.9 and pH 8.2 were less than 20% but were 53.8% and 77.3% at pH 7.6 and pH 7.3, respectively. When newly hatched larvae were incubated for 48h at pH 7.3, only 2.7% of the larvae settled, while more than 70% of the larvae completed settlement in the other three pH treatments. However, most 24h old larvae could complete metamorphosis in all four pH treatments. Overall, a 0.3-unit reduction in water pH will produce no negative effect on the early development of the Pacific abalone, but further reduction in pH to the values predicted for seawater by the end of this century will have strong detrimental effects.

Effects of Formic Acid Administration in the Drinking Water on Performance, Intestinal Microflora and Carcass Contamination in Male Broilers under High Ambient Temperature

In this study, we examined the effects of formic acid administration to the drinking water on performance, intestinal microflora and carcass contamination in male broilers. A total of 312 day-old male broiler chicks were allocated to two groups with three replicates. The first group (control) received normal drinking water (pH 7.4) during the experiment. The second group consumed acidified drinking water (pH 4.5) after 5 d of age. At 43 d of age, twelve birds were randomly selected from the control group to determine the effect of acidified drinking water on carcass contamination. These birds were only given normal or acidified (pH 3) drinking water for 8 h prior to slaughter. The reduction of water pH from 7.4 to 4.5 significantly decreased body weights of male broilers at 21 and 42 d of age. However, no differences were observed between male broilers given normal and acidified drinking water in terms of feed intake, feed conversion ratio and mortality. The pH value of the gizzard contents was not significantly affected by acid water treatment. There were no significant differences in the intestinal population of E. coli, total organism and Salmonella between the groups. The total organism and E. coli counts of the carcass slightly decreased in the acidified group. No Salmonella was identified in carcass samples of any of the treatment groups. The results showed that drinking water acidification did not provide beneficial effects on performance, intestinal microflora and carcass contamination in male broilers.

Cytotoxicity as a marker of mussel health status

Cytotoxic activity of the mollusc Mytilus galloprovincialis haemolymph was considered as a possible marker of mussel health status. An easy-to-use and low-cost cytotoxicity test was set up to assess whether cytotoxicity is influenced by environmental stress such as an increase in water temperature or a reduction in water pH or salinity. Experiments demonstrated that, despite great variability in cytotoxic activity among the mussel populations, changes in the water physical conditions reduce mussel cytotoxicity, making animals more vulnerable to pathogen aggression.

Ion and Acid‐Base Balance in Three Species of Amazonian Fish during Gradual Acidification of Extremely Soft Water

Sensitivity to acid water was assessed in three species of Amazonian fish that encounter naturally acidic blackwaters to differing degrees in the wild: tambaqui (Colossoma macropomum), matrincha (Brycon erythropterum), and tamoatá (Hoplosternum littorale), in decreasing order of occurrence in blackwater. Fish were exposed to a graded reduction in water pH, from pH 6 to 5 to 4 to 3.5, followed by return to pH 6. Fish were exposed to each new pH for 24 h. During these exposures, net transfers of ions (Na+, K+, Cl-, and Ca2+) and acid-base equivalents to and from the external water were used as physiological indicators of acid tolerance. Exposure to pH 5 had a minimal effect on net ion fluxes. Significant net losses of all ions (except Ca2+) were recorded in all three species during the first few hours of exposure to pH 4. However, ion balance was usually restored within 18 h at pH 4. Exposure to pH 3.5 caused even greater ion losses in all three species and proved to be acutely lethal to tamoatá. Matrincha sustained irreversible physiological damage at pH 3.5, as ion fluxes did not recover following return to pH 6 and there was some mortality. Tambaqui suffered the least ionoregulatory disturbances at pH 3.5 and was the only species to make a full recovery on return to pH 6. In all species, there was a tendency for ammonia excretion to increase at low water pH, but even at pH 3.5, there was no significant net uptake of acid from the water. Overall, there was a strong relationship between the magnitude of ionic disturbances and the lethality of exposure to low pH. The relative insensitivity of the ionoregulatory system of tambaqui to low pH indicates that this is a feature of fish native to blackwater systems rather than one that is common to all Amazon fish.

The ultrastructure of chloride cells in the gills of the teleostOreochromis mossambicus during exposure to acidified water

Branchial chloride cells, which actively take up ions in the gills of freshwater fish, were studied in tilapia (Oreochromis mossambicus) exposed to sublethally acidified freshwater. Structural damage of cells, resulting in cell death by necrosis, only occurred transiently, when the reduction of water pH was acute rather than gradual. The most prominent effects of water acidification were the rapid increase in the number of chloride cells and the changes in frequency of the different stages of the chloride cell cycle. In the opercular inner epithelium, a twofold increase in cells occurred 48 h after gradual acidification. Cell density stabilized after 4 weeks at a level 5 times that of control fish. Four transitory stages were distinguished in the chloride cell cycle: accessory or replacement cells, immature, mature, and degenerating (apoptotic) cells. In control fish, mature chloride cells dominated (over 50%) with immature and apoptotic cells totalling about 40%. After 4 weeks in acid water, only 13% of the cells were mature. Immature and apoptotic cells dominated, each representing about 40% of the total number of chloride cells. Mature cells apparently age rapidly under these conditions. Thus, chloride cells turn over quickly in acid water, with a minor increase in ion transport capacity of the gills. This conclusion is supported by the observation that opercular and branchial Na+/K+ ATPase activities in treated fish are only 40%–50% higher than in controls.

Effects of Chemical Clogging on Drip-Tape Irrigation Uniformity

ABSTRACT The following four management schemes were evaluated for lessening the chemical clogging effects of high calcium content water in drip-tape: 1) above ground day-time water application, 2) above ground night-time water application, 3) subsurface placement of drip-tape, and 4) lowering the pH of the irrigation water. Calcium, magnesium and bicarbonate ions were injected into the water source to evaluate water qualities with electrical conductivities of 0.59, 1.12, and 2.02 dS/m. Irrigation duration for each management scheme was four hours daily over the 100-day investigation. Volumetric flow rate and emission uniformity were monitored. Partial and full clogging due to chemical precipitation occurred in all management schemes for the water with the highest salt content. By the end of the study, daily flow values in the laterals had decreased between 20 and 40% for this water. Corresponding flow reductions for the lowest salt content water varied between 3 and 15%. Of the management modes evaluated, reduction of water pH from 7.6 to 6.8, by sulfuric acid injection, provided the least clogging for all three water qualities.

Effects of Aluminum and Low pH on Net Ion Fluxes and Ion Balance in the Brook Trout (Salvelinus fontinalis)

Adult brook trout (Salvelinus fontinalis) were exposed for up to 11 d to one of a matrix of 18 Al, low pH, and Ca2+ combinations, chosen as representive of acidified softwater environments in the wild. Reduction in water pH led to pH-dependent net losses of Na+ and Cl− exacerbated by the presence of Al in the water and reduced by elevating Ca2+. Any animal losing more than 4% of its total body Na+ over the first 24 h of Al exposure had a greater than 90% likelihood of eventual mortality. Na+ losses arose from inhibition of influx and stimulation of efflux. The inhibition was persistent and pH dependent. Addition of Al to acidified water had a slight further inhibitory effect on Na+ influx and a large stimulatory effect on efflux. The latter was dependent on Al concentration, was the main cause of initial ion losses and mortality, and declined with time in surviving animals. All Al-exposed fish accumulated Al on their gills, but this was apparently mainly surface or subsurface bound, since no internal Al (plasma or liver) could be detected. Nonsurviving fish had substantially higher gill Al levels than survivors.