In the present study, the two lakes, Vengaiah lake (Lake A-Sewage polluted receiving discharge from storm water drain) and Yellamallappa Chetty lake (Lake B-Industrially polluted) situated near Krishnarajpuram-Hoskote taluk, Bangalore, Karnataka were selected for analysis of trace metals viz., arsenic, aluminium, cadmium, lead, mercury, iron, copper and zinc in water samples. Muscle and gill tissues of freshwater fish Labeo rohita reared in these water bodies were analysed for bioaccumulation of trace metals. Hebbal fish farm was considered as a reference site (Control site) for water and fish samples. Trace metals were analysed by atomic absorption spectroscopy and values were compared with those recommended by FAO/WHO in water and fish samples. Trace metals such as Al, As and Hg were detected in the water sampled from lake B which is attributed to the differences in the sources of pollutants. Fish tissues viz., muscle and gills sampled from Lake B exhibited high concentration of Al, Pb and Cd content showing a positive correlation with their concentration in water samples. The remaining metals as Cu, Zn and Fe were detected in water sampled from all water bodies and also in the fish tissues. Gills exhibited higher concentration of metals in fish from lake B. Bioaccumulation of these trace metals in fish tissues may cause potential danger to human health when consumed on regular basis. Thus necessary remedial measures are required to combat water contamination and its management keeping in view the aquatic ecosystem and public health. Values were statistically significant at P < 0.0001.
Heavy metals are natural trace components of the aquatic environment, causing threat to the health of Indian ecosystem. High concentration of these metals is released into the aquatic environment as a result of leaching from bed rocks, atmospheric decomposition, water drainage, run off from river banks and discharge of urban and industrial waste waters [
In recent years fish consumption has increased many folds due to its nutritional and therapeutic benefits. Fish are at the top level of aquatic food chain and are good indicators of heavy metal contamination because they accumulate metals in their tissues [
According to Storelli [
Fish kill had been reported in number of lakes in Bangalore city during the past few years due to sudden discharge of effluents from various point and non-point sources into these lakes. There is a lacunae on the assessment of bioaccumulation potential of persistent organic pollutants and trace metals in the tissues of non-target animal, the fish reared in the directly affected water body. The present study was conducted to determine levels of heavy metals accumulated in water and muscle and gill tissue of L. rohita reared in lakes of Bangalore polluted by various sources; which were compared against the recommended BIS and PTWI by FAO/WHO to assess the quality of fish for human consumption. Muscle being an important tissue of nutritive value and gill- which is a vital respiratory organ with their extensive surface area is directly in contact with water and xenobiotics present in water [
Bangalore also called as Bengaluru is the capital of Karnataka state in South India (
Water samples were collected in the morning (8.00 to 9.00 am) in acid washed and dried water sampling glass bottles from control site, lake A and lake B for a period of one year (2013-2014). Trace metal such as As, Cu, Zn, Al, Cd, Fe, Pb and Hg was analysed by Atomic Absorption Spectrometeric method [
precipitation of metals. All the samples were concentrated to tenfold on a water bath and subjected to nitric acid digestion. Trace metal analyses were carried out using flame atomic absorption spectrophotometer (Model: Perkin Elmer 3100). The calibration curves were prepared separately for all the metals by running different concentrations of standard solutions. The instrument was set to zero by running the respective reagent blanks. Average values of six replicates were taken for each determination [
Fish were anaesthetized using MS222 (Ethyl m-amino-benzoate methane sulphate) and dissected at the site itself. After dissecting, the tissues were excised, washed and preserved in 10% formalin for detection of accumulated trace metal by following the standard method [
Statistical analysis was carried by using MS Excel and statistical software-Graphpad prism to evaluate the metal content with respect to three water bodies and tissues of fish. Mean of the water and tissue sample size (n = 6) and standard deviation (mean ± SD) was conducted to quantify their variability which was followed by one way ANOVA to compare significant mean differences of the above mentioned groups. This was followed by Tukey’s post-hoc test to compare pair of groups mean of each metal in water and with its bioaccumulation in fish tissue of control group, lake A and lake B. p value at a significant level of p < 0.05 or less indicated significant relationship within variables. Pearson’s correlation coefficient between metal concentration in lake water (A & B) and muscle and gill tissue of fish were also studied.
Analyses of trace metals content in the three water bodies―Hebbal Fishfarm (control), Vengaiah Lake (A) and Yellamallappa Chetty Lake (B) during the period of study are shown in
Water samples from control site was analysed for the presence of trace metals. The results showed the presence of Cu, Zn and Fe within BIS limits whereas, As, Al, Cd, Pb and Hg were not detected. The concentration of trace metals such as Cu, Zn and Fe showed higher levels (0.25 ± 0.01, 3.12 ± 0.01 and 3.02 ± 0.006 respectively) in lake B when compared to those of lake A (0.03, 1.67 ± 0.01 and 0.11 ± 0.008 respectively) and control. Fe content was recorded above BIS limits in lake B. Hg was observed below detectable limits in water sampled from lake A but showed its presence of 0.023mg/l in lake B which was above BIS limit (0.001 mg/l). Trace metals viz., As, Al, Cd and Pb were recorded below detectable level in water sampled from control site but they were within BIS limits in lake A (As―0.001; Cd―0.04 ± 0.01; Pb―0.04 ± 0.008) with the exception of Al (0.067 ± 0.001) which was above BIS limits. The concentration of these groups of trace metal was recorded higher in water sampled from Lake B when compared to those of lake A. The concentration of Al, Cd and Pb (3.7 ± 0.089, 0.124 and 0.23 respectively) were above BIS limits in lake B.
The presence of these metals in water beyond BIS limits as in the present work might affect the general metabolism and enzyme activity in fish as was recorded by various scientists. Therefore, in the present investigation, analyses of heavy metals were conducted in muscle and gill tissues sampled from control site, lake A and lake B (
Parameters | BIS: 10500-1991 (Revised 2012) | Control site | Lake A | Lake B |
---|---|---|---|---|
Arsenic | 0.05 | 0 | 0.001 | 0.003a |
Mercury | 0.001 | 0 | 0 | 0.023 |
Aluminium | 0.03 - 0.2 | 0 | 0.067 ± 0.001a | 3.7 ± 0.089a |
Cadmium | 0.01 | 0 | 0.04 ± 0.01d | 0.124 a |
Lead | 0.05 | 0 | 0.04 ± 0.008d | 0.23a |
Copper | 0.05 - 1.5 | 0.01 | 0.03a | 0.25 ± 0.01a |
Zinc | 5 - 15 | 0.54 ± 0.02 | 1.67 ± 0.01a | 3.12 ± 0.01a |
Iron | 0.3 - 1 | 0.04 ± 0.01 | 0.11 ± 0.008a | 3.02 ± 0.006a |
Values are expressed in mg/l. Values are expressed as mean ± SD where, n = 6 and “0” indicates BDL. The superscripts a, b, c and d indicate statistical mean differences at p < 0.0001, 0.001, 0.01 and 0.05 respectively.
Parameters | Muscle | Gill | ||||
---|---|---|---|---|---|---|
Control site | Lake A | Lake B | Control site | Lake A | Lake B | |
Arsenic | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
Mercury | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
Aluminium | 0.00 | 0.00 | 2.18 ± 0.14a | 0.00 | 0.00 | 3.81 ± 0.17a |
Cadmium | 0.00 | 0.00 | 0.41 ± 0.50a | 0.00 | 0.00 | 0.24 ± 0.02 |
Lead | 0.00 | 0.00 | 0.15 ± 0.04a | 0.00 | 0.00 | 0.26 ± 0.02a |
Copper | 1.13 ± 0.12 | 1.40 ± 0.29 | 2.89 ± 0.12a | 2.10 ± 0.08 | 3.62 ± 0.16a | 5.02 ± 0.18a |
Zinc | 4.22 ± 0.21 | 6.32 ± 0.39a | 13.65 ± 0.30a | 16.30 ± 0.49 | 19.78 ± 0.32a | 43.71 ± 0.42a |
Iron | 21.59 ± 0.51 | 28.91 ± 0.40a | 73.01 ± 0.52a | 61.65 ± 1.03 | 66.02 ± 0.82a | 93.71 ± 0.63a |
Values are expressed in µg/g dry weight of tissues and as mean ± SD where, n = 6. “0” indicates BDL. The superscripts a, b, c and d indicate statistical mean differences at p < 0.0001, 0.001, 0.01 and 0.05 respectively.
Trace metals including both essential and non-essential elements have a particular significance in eco-toxicology, since they are highly persistent having potential to be toxic to living organisms [
Presence of cadmium in water and its significant levels in fish tissues (muscle & gills) from lake B may cause disturbances in respiration as was also observed in tuna exposed for a short term period to cadmium by Witeska et al. [
In the present study bioaccumulation of lead was detected in muscle and gill tissue of fish sampled from lake B since lead was recorded in significantly high concentration in lake B. Pb, and Cd are not nutrients at trace levels and are non-essential, so they are recognized as important industrial hazards, causing severe toxic effects in higher animals upon acute or chronic exposure. Stomiñska and Jezierska [
Copper, Zinc and Iron was detected in the water sampled from control site as well as lake A & B but was well within the BIS desired range. Even though these metals are essential element in low concentrations but when discharged into the freshwater environments in higher concentrations, copper is reported to cause severe effects on the freshwater fauna, especially fishes [
In the present study, variation in trace metals content is attributed to the differences in the sources of pollutants discharged into the lakes and statistical mean differences were significant at p < 0.0001. Trace metal content in the tissues studied exhibited a positive correlation with their concentration in water samples. Although the values of bioaccumulated trace metals in fish tissues were not high but they may pose a potential danger to the public health in future depending on sources of pollution and its exposure time period. The extent of bioaccumulation of metals in tissues of fish is dependent on its total amount and bioavailability of each metal in the environmental medium, the route of uptake, storage and excretory mechanisms [
A number of serious health problems can develop as a result of excessive uptake of dietary heavy metals. The Joint FAO/WHO expert committee on food additives established a PTWI for aluminium of 1 mg/kg /body- weight/week, for cadmium as 0.007 mg/kg body weight and for lead as 0.025 mg/kg body weight [
With respect to the human health, Al was recorded to be poisonous if it crossed the permissible limits causing various ailments such as Alzheimer’s disease [
It has been predicted that fish consumption in developing countries will increase by 57 percent, from 62.7 million tons in 1997 to 98.6 million in 2020 [
On the basis of present investigation of two lakes, the metal content was higher than standard BIS and WHO limits in the water sampled from Lake B since toxins and trace metals were drained into this lake from the adjacent pharma company and thus can be considered as the more polluted site. The results also revealed that metals were absorbed by the fish showing varied accumulation between two tissues of fish sampled from Lake B. Comparatively higher values were exhibited in gills than muscles which can be attributed to their physiological functioning. Muscle, an edible part of the fish indicated safe levels for human consumption and such concentrations were less than the PTWI as suggested by Joint FAO/WHO Expert Committee on Food Additives. However the trace metals load should be continuously monitored in this lake as it can result in potential damage in the form of toxicological effect on aquatic and human health in the near future.
Nazima Noor,Bela Zutshi, (2016) Bioaccumulation of Trace Metals in Tissues of Rohu Fish for Environmental Risk Assessment. Journal of Water Resource and Protection,08,472-481. doi: 10.4236/jwarp.2016.84040