Acid and aluminum effects on the survival of littoral macro-invertebrates during acute bioassays

Six common macro-invertebrates were exposed to soft water at pH 4.5, with or without 200 microg liter(-1) Al added. Survivals were determined at 6, 12, 24 and 48 h and compared with neutral pH, Al-free controls. The order of acid-sensitivity among the test animals, from greatest to least (with mean 24/48 h survivals in the pH 4.5, low Al treatment in parentheses), was: Caenis sp. (2%) > Hyalella azteca (12%) > Enallagma sp. (20%) > Gyraulus sp. (55%) > Chironomidae (94%) > Hydracarina (99%). Aluminum significantly reduced the survivals of Gyraulus, Hyalella and Chironomidae. The latter group experienced no significant mortality at pH 4.5 except when Al was present. In contrast, the Hydracarina were unaffected by both acid and acid plus Al exposure, and the survivals of Enallagma and Caenis at low pH were enhanced by Al. These differential responses to the treatments indicate that both acid and Al stress may control the structure of the littoral macroinvertebrate community in acid lakes.     

Mortality, growth, swimming activity and gill morphology of brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) exposed to low pH with and without aluminum

Measurements were made of mortality, growth, swimming activity, and gill morphology of young-of-the-year brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar), exposed for 30 days to pH 5.6 +/- 0.5 (mean +/- 1 standard deviation) with and without addition of 107 +/- 57 microg liter(-1) exchangeable (labile monomeric) aluminum. The experiment was conducted in artificial stream channels adjacent to a natural stream and subject to daily and seasonal changes in temperature, light, and chemical conditions. There were no differences in survival or growth for brook trout in any treatment; Atlantic salmon survival and growth were significantly decreased in the acid + Al treatment. Scanning electron microscopy showed no damage to gills of either species in the acid treatments, but the acid + Al treatment caused slight swelling of brook trout gills near the filament tips and significant swelling and fusion of secondary lamellae of Atlantic salmon gills. The acid treatment increased swimming activity in brook trout, but both the acid and acid + Al treatments reduced activity in Atlantic salmon.     

The significance of water ionic strength on aluminium toxicity in brown trout (Salmo trutta L.)

The toxicity of aluminium to fish is related to interactions between aluminium and the gill surface. We investigated the possible effect of water ionic strength on this interaction. The mortality of brown trout (Salmo trutta L.) exposed to three different degrees of Al polymerisation was compared in water with increased ionic strength (mean 7.31 x 10(-4) M) after additions of the base cations Ca2+, Mg2+, Na+ or K+, and in water with no such addition (mean ionic strength 5.58 x 10(-4) M). Only a very slight ameliorating effect of increased ionic strength was observed, while the degree of Al polymerisation was of major importance in fish mortality. In addition, it was observed that smaller fish survived the Al exposures for a longer time than larger fish. We hypothesise that this is because larger fish are more susceptible to hypoxia than smaller fish.     

Effects of aluminium ion on root growth, cell division, and nucleoli of garlic (Allium sativum L.)

The effects of different concentrations of aluminium chloride on root growth, cell division, chromosome morphology and nucleoli in root tip cells of garlic (Allium sativum L.) were studied. The concentrations of aluminium chloride (AlCl(3)) used were 10(-5), 10(-4), 10(-3), 10(-2) and 10(-1) m. Aluminium chloride inhibited root growth and caused mitotic irregularities, including c-mitosis, anaphase bridges, and chromosome stickiness. Nucleolar material was extruded from the nucleus into the cytoplasm. Extrusion was observed in inner root meristem and root cap cells. The poisoning by Al(3+) of the root tip cells of Allium sativum may result from the uptake and accumulation of Al and inhibition of Ca uptake, distribution of physiological activities of calmodulin (CaM) and the inhibition of some enzyme reactions.     

The effects of fenvalerate on different tissues of freshwater fish Cirrhinus mrigala

The histopathological changes of fenvalerate on the gill, kidney, liver and intestine tissues of the Cirrhinus mrigala were determined by light microscopy. The fish were exposed to two sub-lethal concentrations of fenvalerate (1.5-3.0 ppb). The most common gill changes at all concentrations of fenvalerate were epithelial hyperplasia, epithelial necrosis, desquamation and lamellar fusion. Besides, epithelial lifting, oedema, swelling at the tips of secondary lamellae and curling of secondary lamellae were other histopathological changes. Necrosis of tubular epithelium, pycnotic nuclei in the hematopoietic tissue, hypertrophied epithelial cells of renal tubules, narrowing of the tubular lumen, expansion of space inside the Bowman's capsule and contraction of the glomerulus were observed in kidney tissues of fish. Hepatic lesions in the liver tissues of fish exposed to fenvalerate were characterized by congestion, cloudy swelling of hepatocytes and focal necrosis. Atrophy of epithelial cells, necrosis of epithelial cells, desquamation of mucosal epithelium and infiltration of lymphocytes into the lamina propria were detected in intestine tissues of fish after exposure to fenvalerate.     

Histopathology of gills in mosquitofish,Gambusia affinis after long-term exposure to sublethal concentrations of malathion

The histopathological effects of malathion, an organophosphate pesticide, on the gill tissues in mosquitofish, Gambusia affinis, were determined by light microscope. The fish were exposed to sublethal concentrations (0.01 and 0.02 mg/L) of malathion for 10, 20 and 30 days. Histological examination of the gills treated with malathion showed a variety of histopathological effects. The gill lesions included necrosis and desquamation of secondary lamellar epithelium, lifting up of epithelium, intraepithelial oedema, fusion of adjacent secondary lamellae, haemorrhage at primary lamellae, disorganization and rupture in seconder lamellae, hypertrophy and hyperplasia of epithelial cells. These alterations were time- and dose-dependent.     

Effects of experimental terbuthylazine exposure on the cells of Dicentrarchus labrax (L.)

The effects of acute exposure to the herbicide terbuthylazine (3.55, 5.01 and 7.08 mg l(-1)) on the cells of farmed European sea bass, Dicentrarchus labrax L., were investigated by means of light and electron microscopy. In gills of treated fish, the number of chloride cells (CCs) and rodlet cells (RCs) increased significantly within 24 h and 48 h, respectively; the intestine showed the largest increase in RCs linked to treatment and exposure time. In kidney, 24 h exposure induced a significant increase in RCs and the number and global area of macrophage aggregates (MAs). Treated fish displayed cellular and/or ultrastructural alterations in all the organs examined. In the gills necrosis, lamellar and cellular oedema, epithelial lifting, telangectasia, and fusion of secondary lamellae were encountered. The liver presented myelin-like figures, cytoplasmic rarefaction and acute cell swelling of hepatocytes. In both organs, the severity of damage was dose-dependent. In RCs of gills, the intestine and kidney of exposed sea bass, high cytoplasmic vacuolization, myelin-like figures, cristolysis and varying degrees of rodlet degeneration were observed. Extensive rodlet expulsion occurred in the gut lumen. Exposure to terbuthylazine also affected the renal tubular epithelial cells, which exhibited 'blebs'. Damage to the intestinal epithelial cells was also observed.     

Endosulfan acute toxicity and histomorphological alterations in Jenynsia multidentata (Anablepidae, Cyprinodontiformes)

Toxicity tests using adult specimens of Jenynsia multidentata were carried out during 96 hours in order to determine the lethal concentration (LC50) of endosulfan. Histological alterations were determined in gills and liver. Gill damage was quantified as secondary lamellae thickness. The 96 hr LC50 values were significantly different between males (0.719 microg x L(-1)) and females (1.317 microg x L(-1)). The sex difference was attributed to the dimorphism in the lipid content in females (2.16%) and males (1.79%). Histological alterations in gills included hypertrophy and lifting of the epithelium of the secondary lamellae and aneurisms. These alterations caused a significant increase of the secondary lamellae thickness in treatment versus control fish. Finally, reversible histological alterations (such as hydropic degeneration and dilation of sinusoids) were observed in the liver of exposed fish as well as an irreversible change such as necrosis at the highest concentrations.     

Metal bioavailability and toxicity to fish in low-alkalinity lakes: A critical review

Fish in low-alkalinity lakes having pH of 6.0-6.5 or less often have higher body or tissue burdens of mercury, cadmium, and lead than do fish in nearby lakes with higher pH. The greater bioaccumulation of these metals in such waters seems to result partly from the greater aqueous abundances of biologically available forms (CH(3) Hg(+), Cd(2+), and Pb(2+)) at low pH. In addition, the low concentrations of aqueous calcium in low-alkalinity lakes increase the permeability of biological membranes to these metals, which in fish may cause greater uptake from both water and food. Fish exposed to aqueous inorganic aluminum in the laboratory and field accumulate the metal in and on the epithelial cells of the gills; however, there is little accumulation of aluminum in the blood or internal organs. In low-pH water, both sublethal and lethal toxicity of aluminum has been clearly demonstrated in both laboratory and field studies at environmental concentrations. In contrast, recently measured aqueous concentrations of total mercury, methylmercury, cadmium, and lead in low-alkalinity lakes are much lower than the aqueous concentrations known to cause acute or chronic toxicity in fish, although the vast majority of toxicological research has involved waters with much higher ionic strength than that in low-alkalinity lakes. Additional work with fish is needed to better assess (1) the toxicity of aqueous metals in low-alkalinity waters, and (2) the toxicological significance of dietary methylmercury and cadmium.     

Role of exogenous and endogenous silicon in ameliorating behavioural responses to aluminium in a freshwater snail

Aluminium accumulation by the freshwater snail Lymnaea stagnalis is correlated with behavioural depression which is ameliorated by addition of orthosilicic acid. We hypothesised that Si is relocated to the digestive gland in response to Al, leading to the formation of non-toxic hydroxyaluminosilicates (HAS). Exposure to 500 microg l(-1) Al for 30 days was associated with an initial period of behavioural depression, followed by apparent tolerance and subsequent depression, suggesting saturation of the cellular detoxification pathway during prolonged exposure. Exogenous Si (7.77 mg l(-1)) completely ameliorated all behavioural effects of Al but did not prevent its accumulation. In the presence of added Al, significantly more of this Si was accumulated by the tissues, compared to controls and snails exposed to Si alone. In snails exposed to Al plus Si, Al and Si concentrations were significantly correlated, with a ratio around 3:1 Al:Si, consistent with the presence of the non-toxic HAS protoimogolite.     

Littoral zooplankton responses to acid and aluminum stress during short-term laboratory bioassays

During autumn 1990, littoral zooplankton were collected from three alkaline lakes in Ohio, USA. Toxicity tests were performed, in which animals were placed into treatments of pH 4.5, with or without 500 microg litre(-1) Al added. Percentage survival after 24 h was determined for each test species, and compared to survival in controls (pH roughly 8.0). Three distinct responses were observed: (1) Four cladocerans, Simocephalus serrulatus, Diaphanosoma birgii, Acantholeberis curvirostris and Chydorus sphaericus, were tolerant of both acid and Al, with no significant reductions in survival in the treatments. (2) The cladoceran Eurycercus lamellatus and the capepod Acanthocyclops vernalis were sensitive to both acid and Al, and suffered 100% mortality in both treatments. (3) The cladocerans Camptocercus rectirostris, Alona costata and Pleuroxus denticulatus, and the copopod Mesocyclops edax showed decreased survival in the acid treatment, and a significantly greater decrease in the acid plus Al treatment. For nine of the ten test species, the results were consistent with previous survey and paleolimnological studies. The results indicate that direct toxic effects of H+ and Al ions largely determine the responses of these common littoral species to acidification.     

Acid and aluminum effects on freshwater zooplankton: an in situ Mesocosm study

An in situ mesocosm experiment was performed to evaluate the role of aluminum toxicity in determining zooplankton community responses to take acidification. Large plastic enclosures were suspended in East Twin Lake, Ohio, USA, and duplicates were either untreated controls (pH 8.8), acidified to pH 4.5 over a 23 day period, or acidified and also spiked with incremental additions of Al, to produce a final inorganic monomeric Al level of 180 microg/liter at pH 4.5. Zooplankton abundance and species richness declined in both acid treatments, relative to the control, as numerous acid-sensitive species were eliminated. All of the acid-sensitive species were also Al-sensitive, declining in abundance more rapidly in the acid plus Al treatment than in the acid-alone treatment. Only two small cladocerans (Bosmina longirostris and Chydorus sphaericus) were acid tolerant. Both were also tolerant of elevated Al levels.     

Accumulation of aluminium by the freshwater crustacean Asellus aquaticus in neutral water

This study examined the accumulation of aluminium (Al), mostly as the insoluble (Al(OH)(3)) species, by the freshwater crustacean Asellus aquaticus at neutral pH. Animals were exposed to a range of Al concentrations (5-356 microg l(-1)) in three experiments. The first two were of 30 and 50 days duration, respectively, followed by transfer of the A. aquaticus to water containing no Al for 20 days. The third used live and dead animals in order to investigate the contribution made by surface adsorption of Al to the total accumulated. Significant accumulation of Al in the whole tissues occurred by day 10 in all animals in the 30- and 50- day experiment. Peak concentrations of Al were measured in animals between days 10 and 20 with high concentration factors ranging from 1.4 x 10(4) to 5.5 x 10(3). By day 30, accumulated Al had fallen but was still significantly greater than the control in the 50- day exposure experiment. This 30- day increase followed by decreased accumulation of Al was repeated over the remaining exposure period (i.e. 30-50 days) although rates of uptake and loss and peak tissue levels of Al were higher. Proportionality between environmental (water) and tissue concentrations of Al occurred at day 20 but not at day 45. Significantly more Al was accumulated by dead animals than live animals at all Al exposure concentrations. These results suggest that Al is available to the crustacean at neutral pH and that the cuticle may provide an important site of uptake.     

Kinetics and mechanism of oxidation of tetrachloroethylene with permanganate

The kinetics, reaction pathways and product distribution of oxidation of tetrachloroethylene (PCE) by potassium permanganate (KMnO4) were studied in phosphate-buffered solutions under constant pH, isothermal, completely mixed and zero headspace conditions. Experimental results indicate that the reaction is first-order with respect to both PCE and KMnO4 and has an activation energy of 9.3+/-0.9 kcal/mol. The second-order rate constant at 20 degrees C is 0.035+/-0.004 M(-1) s(-1), and is independent of pH and ionic strength (I) over a range of pH 3-10 and I approximately 0-0.2 M, respectively. The PCE-KMnO4 reaction may proceed through further oxidation and/or hydrolysis reaction pathways, greatly influenced by the acidity of the solution, to yield CO2(g), oxalic acid, formic acid and glycolic acid. Under acidic conditions (e.g., pH 3), the further oxidation pathway will dominate and PCE tends to be directly mineralized into CO2 and chloride. Under neutral (e.g., pH 7) and alkaline conditions (e.g., pH 10), the hydroxylation pathway dominates the reaction and PCE is primarily transformed into oxalic acid prior to complete PCE mineralization. Moreover, all chlorine atoms in PCE are rapidly liberated during the reaction and the rate of chloride production is very close to the rate of PCE degradation.     

The mixing zone between limed and acidic river waters: complex aluminium chemistry and extreme toxicity for salmonids

When liming running waters, dosers must compensate for different flow and water qualities and for the downstream inflow from acid tributaries which creates mixing zones. At a certain point in the mixing zone, a constant or fluctuating chemical disequilibrium will appear due to transformation processes. In laboratory assays, over-saturated solutions of aluminium with ongoing active precipitation of aluminium have been found to be especially toxic to fish. Recent experiments in a mixing zone in the limed River Audna, Norway, have confirmed this phenomenon. Atlantic salmon (Salmo salar L.) and sea trout (Salmo trutta L.) smolts were exposed to acid and limed waters and mixtures of the two waters downstream from the point of connection. In the acid tributary (mean values: pH=4.8, Ca=1.3 mg litre (-1)), Ali 236 microg litre(-1)=), LT5) was 22 and 40 h for Atlantic salmon and sea trout, respectively. In the mixing zone (pH=4.8-6.5, Ca=1.2-3.2 mg litre(-1), Ali=50-240 microg litre(-1)), LT50 was 7 h for both species, masking the normal species difference in tolerance. Osmoregulatory failure and rapid gill lesions occurred in the mixing zone as an effect of the transformation of Al into high molecular weight precipitating species. This is the first documentation of the existence of such highly toxic mixing zones in nature, and the results clearly show that the mixing zone is even more toxic to fish than acid aluminium-rich waters.     

Ultrastructural changes in the respiratory lamellae of the catfish, Heteropneustes fossilis after sublethal exposure to malathion

Transmission electron microscopy study of the gills of Heteropneustes fossilis, exposed to 4 mg/liter of malathion (1/3 of LC50) for 24, 48, 72, and 96 h showed significant changes in its ultrastructures. Exposure to the pesticide after 24 h caused a slightly disarrayed condition in the double layered epithelial structure. Lymphatic spaces became more apparent, and a few chloride cells appeared which protruded toward the peripheral margin of the secondary lamellae. Chloride cells were exposed to the exterior by an apical pit. Pinocytosis was observed with marginal folds (MF) originating from the pillar and epithelial cells. Some vascular constrictions were also seen in the capillaries with erythrocytes. After 48 h exposure, the outer epithelial cells were stretched into a thin boundary wall and lymphatic spaces were engorged with plasma exudate. Chloride cells transversed the whole epithelium of the lamella and came into direct contact with lymphoid space and exterior to epithelial lining. Basement membrane of the capillaries became thicker. After 72 h a distorted lamellar epithelium ruptured in a few places allowing many spheroid bodies and some chloride cells come out. Marginal folds of pillar cells migrated into vascular spaces. Basement membrane of capillaries became thicker and blood channels were constricted causing vascular stasis. No erythrocytes were visible. Blood channels were filled with leukocytes and amoebocytes. After 96 h exposure to malathion narrowing of lymphatic spaces, proliferation of epithelial cells and development of pinocytotic vesicles from marginal folds of pillar cell flanges were observed. Only marginal blood channels maintained normal configuration. Vascular stasis due to thickening of the basal lamina were still evident in centrally located blood channels filled with leukocytes. Vascular stasis would likely cause a decrease in respiratory efficiency. This study has revealed that the gills of H. fossilis were affected by a sublethal dose of malathion. The ultrastructural damages to the gills were observed as early as at 24 h exposure, but the most severe damage occurred at 72 h exposure. However, signs of gill structure regeneration were seen in malathion-exposed fish after 96 h.     

Water quality and fish size affect toxicity of endosulfan, an organochlorine pesticide, to rainbow trout

The acute toxicity of endosulfan in juvenile rainbow trout (Oncorhynchus mykiss, 10.61+/-1.69 g) was evaluated in glass aquaria under static conditions. Nominal concentrations of endosulfan in the toxicity test ranged from 1.3 microg l(-1) to 29 microg l(-1). The concentrations of endosulfan that killed 50% of the rainbow trout within 24-h (24-h LC50), 48-h LC50, 72-h LC50, and 96-h LC50 were 19.78, 8.89, 5.28, and 1.75 microg l(-1), respectively. None of the unexposed control fish died, and the first fish died 4 h after exposure to 26.3 microg l(-1) of endosulfan. Survival of fish was significantly increased with increasing fish size and decreased with decreased fish size at the same temperature (p<0.001). Temperature also had a significant effect on survival of fish. Alkalinity at levels above 20 mg l(-1) as CaCO3 significantly increased survival of fish at 19.78 microg l(-1) of endosulfan. Increasing alkalinity from 20 mg l(-1) as CaCO3 to 42 or higher concentrations tested in this study (121 mg l(-1) as CaCO3) significantly increased survival of fish (p<0.01). Total hardness ranging from 55 mg l(-1) as CaCO3 to 126 mg l(-1) as CaCO3 did not affect survival of fish exposed to endosulfan. Endosulfan toxicity was found to be irreversible when fish were exposed to minimum concentrations of endosulfan tested. Histologically, fish gills had lamellar edema, separation of epithelium from lamellae, lamellar fusion, and swelling of the epithelial cells. Melanomacrophage centers were scattered throughout the trunk kidney, head kidney, and spleen. The liver of endosulfan-exposed fish had severe focal necrosis. None of these lesions were seen in unexposed control fish. Results indicate that alkalinity, temperature, and fish size affect endosulfan toxicity of rainbow trout.     

Correlations between toxic Pb effects and production of Pb-induced thiol peptides in the microalga Stichococcus bacillaris

Comparing Pb toxicity to the green alga Stichococcus bacillaris and production of Pb-induced thiol peptides in 24-h exposed cells made it possible to show the level of these peptides to reflect Pb availability to algal cells. LC-ESI/MS analysis of these peptides confirmed that they are phytochelatins PC2-PC4 and their des-Gly derivatives. Studies were carried out at environmentally relevant pH values (5-8.5) and various concentrations of hardness cations (Ca, Mg) and orthophosphate: (0-0.1 mM), chloride (0-100 mM), citrate (0-1 mM), and humic acids (0-10 mg/l). It has been stated, on the basis of the level of Pb-induced thiol peptides, that Pb availability to algae changed significantly within the range of the pH values studied, and was limited in the presence of calcium and of some complexing ligands like orthophosphate, chloride and citrate; it did not decrease in the presence of magnesium or humic acid.     

Short chain fatty acids influence virulence properties of Salmonella enterica serovar Typhimurium

The present study investigated SCFA exposed Salmonella enterica serovar Typhimurium for its virulence characteristics such as mouse lethality adhesion, surface hydrophobicity, phagocytic uptake, intracellular survival within the murine peritoneal macrophages, induction of acid tolerance response (ATR), and the expression of outer membrane proteins (OMPs). Lethal dose (LD50) for mice was found to be more for SCFA exposed cells as compared to the normal cells. In vitro adherence to murine intestinal epithelial cells as well as surface hydrophobicity of SCFA exposed cells were found to be lower than the normal cells. Though the phagocytic uptake of normal cells and SCFA exposed cells was similar, the SCFA exposed cells exhibited increased intracellular survival as compared to the normal cells, which were completely killed after 4 h. Moreover, SCFA exposed cells also survived exposure to extremely low pH (3.0). Outer membrane proteins extracted from SCFA exposed cells revealed an enhanced expression of proteins (porins) at 4% SCFA concentration. Thus, SCFA exposure may contribute to enhanced virulence of Salmonella enterica serovar Typhimurium by increased intracellular survival, induction of acid tolerance response, and the enhanced expression of outer membrane matrix proteins (porins).     

Endosulfan acute toxicity and histomorphological alterations in Jenynsia multidentata (Anablepidae,Cyprinodontiformes)

Toxicity tests using adult specimens of Jenynsia multidentata were carried out during 96 hours in order to determine the lethal concentration (LC50) of endosulfan. Histological alterations were determined in gills and liver. Gill damage was quantified as secondary lamellae thickness. The 96 hr LC50 values were significantly different between males (0.719 μ g.L^{? 1}) and females (1.317 μg.L^{? 1}). The sex difference was attributed to the dimorphism in the lipid content in females (2.16%) and males (1.79%). Histological alterations in gills included hypertrophy and lifting of the epithelium of the secondary lamellae and aneurisms. These alterations caused a significant increase of the secondary lamellae thickness in treatment versus control fish. Finally, reversible histological alterations (such as hydropic degeneration and dilation of sinusoids) were observed in the liver of exposed fish as well as an irreversible change such as necrosis at the highest concentrations.