Abstract

The paper investigates a comparative assessment of water quality of Ikop Lake which is a fresh water lake of Manipur and its peripheral fish farms.Rapid population expansion and corresponding anthropogenic activities of the surrounding villages of Ikop lake play crucial role in contamination of water. It enhances degradation of water quality of this fresh water lake. The level of contamination can be evaluated either from physical and chemical or from biochemical attributes. Present study was undertaken to assess the water quality status of Ikop lake and its peripheral fish farms during June to September, 2022 by using different physiochemical parameters such as, temperature, pH, free carbon dioxide (CO₂), dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), total hardness, total alkalinity, chloride, conductivity, turbidity, sodium, potassium, phosphate, total coliform etc. The result values of different parameters showed variations in lake water and farm water. It also indicated deteriorating quality of both water bodies.

1. Introduction

Wetlands or lakes are the main source of livelihood for the nearby inhabitants since time immemorial.About 0.3% of our fresh-water are found in the lakes, rivers and swamps ¹. The water bodies like rivers, lakes, and estuaries are continuously subject to a dynamic state of change with respect to their geological age and geochemical characteristics ². Bio-diversity within such places play major role in sustainable ecological balance. However anthropogenic changes have ensured a great loss of habitat and diversity over earth. The lakes and reservoirs all over the country without exception are in facing varying degrees of environmental degradation due to encroachment and eutrophication from domestic and industrial effluents and silts ³. Manipur one of the seven sister states of North- East India is blessed with many enticing freshwater lakes. At present there are 17 lakes and 2-ox bow lakes in Manipur ⁴. Ikop lake is one among the important lakes of Manipur. This freshwater lake had been degraded its pristine nature due to excessive influx of sediments formed by Heirok-Wangjing river, Arong river and Khelakhong canal. Previous physicochemical analysis revealed highly polluted water condition of the lake ⁵. Main feeder streams of the lkop lake are Arong river and Heirok-Wangjing river. This lake was home to various kinds of migratory birds and wild animals which can fascinate the viewers. However, this enchanted lake is right now in the midst of heavy anthropogenic activities after the construction of ring road between Athokpam and Leishangthem.Over the past few decades many fish species are not appeared and some are declining their numbers. Earlier there were large areas of wetland surrounding the lake. Gradually these wetlands were converted into agricultural land by the surrounding inhabitants. More than one-third of agricultural lands around the lake were converted into fish farms by the farmers. These farms are ponds surrounded by thick earthen wall of about 3m in height and 2m wide at the top. The main sources of water for the farms are rain water, the lake through small canals and from rivers. Rearing of cattle, piggery and poultry are done in farms as well as the peripheral areas of the lake.During rainy season waste water from farms discharged into the lake.Exotic fish species like exotic Grass carp (Ctenopharyngodon Idella), Rohu (Labeo rohita), Tilapia(Oreochromis mosambicus),Scale carp (Cyprinus carpio) are commonly cultured in the fish farms. The fishes are cultured using artificial and natural feeds.

For finding a solution of management strategy to protect and conserve the biodiversity of the lake, it is important to investigate physiochemical parameters of water body of the lake and its peripheral fish farms. Consequently, this study was undertaken to determine water quality status of Ikop lake and its peripheral firms.

In Section 2, the sampling area, materials and methods of the study are given. In Section 3, the parameter values of each month and relevant graphs are shown. Using one- tail t-test, the parameter values of the lake and its peripheral farms are compared with the corresponding WHO recommended parameter values and a conclusion is given in section 4.

2. Description of the Study Area

Ikop lake is situated in Thoubal district, Manipur at a distance of 40 km. in the south-eastern direction from Imphal. The lake is situated in between latitudes 24⁰ 35’36”N and 24⁰59’32”N, and longitudes 93⁰ 52’E and 93⁰ 94’E. This lake is 772m above the sea level, the maximum depth is about 1.59m and an area of 13.5km2(7.5km length and 1.8 km in breadth). Total area of the lake was around 166.95 km2 based on 1989- 1990 survey data. This lake is surrounded by the villages, viz.:Leishangthem, Khekman, Moijing and Thoudam on the Northern side; Athokpam, Khangabok, Tentha on the Eastern side; Khelakhong on the Southern side; and Irong Thokchom and Maibam on the Western side. This lake is seasonally flooded by Arong river, Heirok-Wangjing river and occasionally flooded due to breakage of Thoubal river bank.

Materials and Methods

This study was conducted during monsoon season (June to September, 2022). Surface water samples of the lake and its peripheral firms were collected from different five (5) sites of the lake and five (5) sites of peripheral fish farms. The names of the sites with their code numbers (code numbers are for convenience only) are given below (Table 1):

Fifteen physico-chemical parameters such as, temperature, pH, free carbon dioxide (CO₂), dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), total hardness, total alkalinity, chloride, conductivity, turbidity, sodium, potassium, phosphate and total coliform were considered for the water quality analysis. Analysis was carried out using standard methods and techniques described by Trivedi and Goel (1984) and APHA (2005). Water samples were collected in one-litre bottles which were de-ionized with distilled water before using them.Water temperature was determined using digital thermometer and electrical conductivity was determined using a portable pen type pH meter. Parameters like Temperature, pH, dissolved oxygen (DO), free CO₂, electrical conductivity was determined in-situ while other parameters were determined in the laboratory.

The results of analysis of the parameters of the water samples collected from the sites (Table 1) during June to September, 2022 are given below:

pH

pH measures the intensity of acidity or alkalinity and also measures the concentration of hydrogen ion in water ⁶. The value of pH indicates quality of water and also determines the sustainability of water for intended purposes, drinking, suitability to support aquatic life ⁷. The lowest pH value (5.8) in the lake was recorded in L5 (June2022) and highest value (7.3) in L1 (September2022) (Figure 2). On the other hand, the minimum pH value (6.0) in the farm water was recorded inF3 (June 2022) and the highest (8.1) in F1 (September 2022). The mean pH values of both lake and farm water were within the permissible range of WHO (Table2&3). However, its value below neutral level (7) shows slightly acidic condition of both water bodies during study period. A pH between about5 and 6.5, sub lethal effects on many streams species may result in reduced fecundity, growth and population size ⁸.

Water Temperature

Water temperature is one of the important factors for aquatic life. Temperature influences several parameters and can alter the physical and chemical properties of water ⁹. The mean water temperature of lake and farm water were ranged from 25⁰C to 27⁰C.The highest temperature value (29.5⁰C) in the farm was recorded in F3(July 2022). The water temperature recorded in the farms were generally higher than the lake water temperature (Table2&3). This is because of stagnant condition of farm water coupled with low concentration of dissolved oxygen.Since the concentration of dissolved oxygen is inversely related to water temperature ¹⁰, the amount of dissolved oxygen thus affects water temperature.

Free CO₂

Free CO₂ is an essential gas for macrophytes. It is present in water as dissolved form, which is derived from different sources such as atmosphere, respiration by the organisms and bacterial decomposition of organic matter etc. ¹¹. The average values of CO₂ in both farm water and lake were negligibly different from the WHO standard value (Table 2&3). Even though the highest value of the CO₂were recorded in the L3 (88.mg/l) and F4(110 mg/l) both in September 2022.High carbon dioxide in water indicates higher microbial pollution rate ¹². This high value of CO₂ (>35mg/l)in L3 and F4 water shows the highly polluted condition of water especially in these sites. The value of CO₂ may inversely related to pH value since higher amount of free CO₂ in water may decrease the pH value due to the formation of carbonic acid.

Dissolved Oxygen

Dissolved oxygen indicates quality and sustainability of aquatic life. The average dissolved oxygen value of lake(4.04mg/l) was below the WHO standard value (Table 2&3)). It shows the stressful condition of fish ¹³. Moreover, L2 had the lowest DO value (1.62mg/l) in June 2022 which was less than permissible limit while L1 and F1 recorded highest values (8.91mg/l) in September 2022 and (8.74mg/l)in June 2022 respectively. The low level of dissolved oxygen in water is a sign of contamination and is an important factor in determining water quality, pollution control and treatment process ¹⁴. Due to influx of organic waste, especially domestic sewage from nearby inhabitants and livestock might be one of the important factors for low level of DO in L2 site.

BOD

Biological oxygen Demand (BOD) is the amount of oxygen required by bacteria and other micro organisms to break down organic materials under aerobic condition ¹⁵. F5 and L2 had the highest BOD values of 17.63mg/l and 10.95mg/l respectively in September 2022. Water with BOD less than 4mg/l is considered as unpolluted, while, more than 10mg/l regarded as polluted ¹.The average BOD of farm water(6.47mg/l) during study period was above the standard value of WHO(Table 2&3).The observed increase in BOD value in monsoon season might be due to biological activities at elevated temperatures in rainy season ¹⁶. Allochthonous input from surface runoff during rainy season might be key factor for high level BOD in lake water and farm water.

COD

Chemical Oxygen Demand (COD) is an indicative measurement of the amount of oxygen that can be consumed by chemical pollutants or compounds in a measured solution ¹⁷. COD detection can be used to easily quantify the amount of organic matter. The mean COD values of farm (12.89mg/l) and lake (9.35mg/l) were about standard value of WHO (Table 2&3). However, F5 and L2 had the highest value of 22.36mg/l (September 2022) and 22.21mg/l (August 2022) respectively. F2 and L4 had the lowest value of 1.21 mg/l and 3.30 mg/l respectively in the monsoon season.The COD values of F5 and L2 were above permissible limit (20mg/l).

Total Hardness

Total hardness is the measurement of the mineral content in water sample that is irreversible by boiling ¹⁸. It is caused due to dissolved calcium, magnesium and other ions such as iron and manganese ¹⁹. L1 and F2 had highest values of 250 mg/l in September and F2 had the highest value of 198 mg /l in June. However, the average total hardness value of both lake water and farm water were within the standard value of WHO (Table 2 & 3).

Total Alakalinity

Total alkalinity is the measure of water’s ability to neutralize acids. Alkalinity in freshwater is mainly derived from the dissolution of limestone, calcium silicate and feldspar minerals ²⁰. The mean values of total hardness in lake and farm water were within the standard value of WHO(Table 2&3). However, value of alkalinity was highest in site L1(215mg/l) and F2(250 mg/l) both in June .Higher alkalinity in lake water may result due to waste discharge, microbial decomposition of organic matter in the waterbody ²¹.

Chlorides

Chloride is one of the major inorganic anions which is found in both fresh water and saltwater ²². Chloride in water generally due to sodium, potassium and calcium salts ²³.Chlorides can also be found when chloride salts dissolved in an aqueous solution ²⁴. The highest value of chloride was recorded in L1 and F2 with 95.14mg/l and 85.2mg/l respectively. However, the average value of chloride in farm and lake water were within the standard value (Table 2&3). Increased salinization and chloride concentrations can induce a variety of ecological effects within both aquatic and terrestrial eco systems ²⁵. Chlorides have mild effect on living organisms, however values higher than recommended limit (<250mg/l) may cause some serious damage or poisoning to living body [34]

Electrical Conductivity

Electrical conductivity (EC) is a measure of water’s ability to pass electric current ¹³. The average conductivity values of both water bodies were within the standard value of WHO (Table 2&3). Water temperature can cause conductivity to fluctuate daily ²⁶. L1 and F2 had the highest conductivity value 446mS/cm and 424mS/cm in September and June respectively. The high value of conductivity indicates higher amount of impurities (dissolved substances, chemicals, and minerals) are in the water ²⁷.

Turbidity

Turbidity is the measurement of water clearness (transparency). Turbidity in natural water is caused by clay, silt, fine organic and inorganic compounds, algae and other microscopic substances ²⁸. The F2 and L1 had the highest values of 150.4 NTU and 34.8 NTU respectively in September. However, the average values of turbidity in lake water(19.26mg/l) and farm water(38.13mg/l), which is beyond permissible limit of WHO (Table2&3) indicates low water clarity. The high value of turbidity decreases the photosynthetic activity of macrophytes resulting into low level of oxygen concentration in water. This high value of turbidity in lake water in monsoon may be considered due to soil erosion, surface run off, waste discharge from surrounding inhabitants and muddy water from eroded banks of Arong river and Heirok-Wangjing river.

Sodium

Sodium is one of the important naturally occurring cation which is abundant in industrial waste, domestic sewage and its concentration increased in natural water after disposal ⁶. The average value of sodium in lake water and farm water were found as 14.95 mg/l and 15.95mg/l respectively. But highest values were recorded in L1 and F2 with 32.80mg/l and 31.7mg/l respectively in June. This higher value at L1 might be due to dissolved fertilizers and pesticides from agricultural catchment fields, domestic waste and sewage from inhabitants at periphery site of the lake.

Potassium

Potassium is the fourth naturally occurring anion in freshwater ecosystem and is always recorded in lesser value than sodium, calcium, magnesium ²⁹. The average values of potassium in lake water(2.17mg/l) and farm water(6.07mg/l) were within the permissible limits of WHO ((Table 2&3). The highest values were recorded in L1 and F2 with7.9mg/l and 36.9mg/l in June. The potassium losses from agro ecosystem led to an increasing K+concentration in the surface water ³⁰.

Phosphate

Phosphate is charged ion particle that contain mineral phosphorous. Itis a vital nutrient for both plants and animals for growth and development, but too much phosphorous in water leads to excessive growth of algae and aquatic plants leading to eutrophication state of water ¹³. The average phosphate values of farm water (0.mg/l) and lake water (0.3mg/l), were within the acceptance range of WHO (Table 2&3).The values of phosphate was highest in L1and F3 with 0.34mg/l and 33mg/l in June and July respectively. Agricultural runoff and organic sewage from nearby inhabitants are the source of phosphate in lake water ¹⁰.

Total Coliform.

Total coliform includes all kinds of coliform bacteria that are found in our surroundings. Coliform bacteria are present in the faeces of all warm-blooded animals and humans ³¹.It is also found in the environment (nutrient-rich waters, soil and decaying plant material) as well as in the drinking water with relatively high concentration ³². The average value of total coliform in farm water and lake water were ranged from 442 MPN to 470 MPN. The highest values were recorded in L3 with 1600 MPN/100ml in September and L5 with 774.19 MPN/100ml in August. The presence of total coliform in water sample indicates the environmental contamination ³³. The elevated values of total coliform in lake water and farm water suggested that disease-causing organisms might also be present

3. Result of t-test

For each site of the Ikop lake the ‘mean’ of the values of each physiochemical parameter of the water samples collected during the period from June to September,2022 were calculated.Corresponding to each physiochemical parameter value, there were fifteen (15) sample spaces each having five(5) sample points. Then the Mean and Standard Deviation (SD) of each parameter corresponding to the sample points are calculated. Then (using one-tail t-test) the t- score and critical t-score at a 95% confidence level for each sample parameter are also calculated. All those results including the WHO recommended standard Physiochemical parameter values of water quality are shown in Table 2.

Similarly, the results of ‘mean’, Standard Deviation, t-scoreand critical t-score at a 95% significance level and WHO recommended standard Physiochemical parameter values of water quality for each parameter of the peripheral fish firms are also calculated and shown in Table 3.

The observed absolute value of t- score (Table 2)&(Table3) of the parameters: Free CO₂, DO,BOD, Conductivity and Turbidity were found less than the critical t-score, indicating that they belonged to Null Hypothesis, that is, they were not statistically different from the corresponding WHO recommended water parameter values. The absolute t- score of other parameters, viz. pH, Temperature, COD, T. Hardness, T. Alkalinity, Chloride, Sodium, potassium, Phosphate and Total coliform were found greater than the critical t-score and hence, they belonged to Alternate Hypothesis, and statistically different from the corresponding WHO recommended water parameter values.

Moreover, the absolute values of t-score of the parameters of the lake such as pH, DO, COD, Turbidity, and Potassium were found greater than those of corresponding parameters of the peripheral farms. The other remaining ten parameters, viz. water Temperature, Free CO₂,BOD, Hardness, Alkalinity, Chloride, Conductivity, Sodium, Phosphate and Total-coliform were less than those value of corresponding parameters of the peripheral firms (Table 4).

4. Conclusion

The result shows that the parameters for both the lake and its peripheral fish farms which are not statistically different from the WHO recommended quality standards for various purposes are Free CO₂, DO,BOD, Conductivity and Turbidity while those that have exceeded the quality standards are pH, Temperature, COD, T. Hardness, T. Alkalinity, Chloride, Sodium, potassium, Phosphate and Total coliform. The increase in parameters that have exceeded the maximum quality standard derived from natural resources, agricultural fertilizers, inappropriate fisheries management and an increasing human population using more fish and domestic waste from community activities is quite high.

Further seasonal studies on the water quality of the lake as well as the peripheral farms will supplement the present findings and give clear status of the contamination level of Ikop lake which is also one of the important wetlands of Manipur.

References