The growing global population and corresponding rise in food consumption required the search for innovative methods to boost agricultural productivity. Man uses chemicals extensively to preserve crops from pests in an effort to boost agricultural yield. These chemicals are used mostly for controlling weeds and other pests in the field. While there are numerous advantages to using pesticides in agriculture, one significant issue associated with their use is environmental pollution and degradation [1]. Humans and other species in the environment have been in competition for existence since the dawn of time. Cultivated crops and their growing environs have become highly attractive to pests such as insects, rats, and other vermin [2]. The invention of pesticides allowed for the creation of an ordered pattern of pest management. As a result of this, competition became more severe as people proceeded to alter the environment [3]. In reality, the development of pesticides was sluggish and had a limited range of uses in the beginning. In many cases, its use was severely limited to a narrow area, such that the environmental effects were negligible.

The usage of pesticides increased in response to the growing global population, which had greater and more noticeable effects on the environment [4]. Since pesticides are widely used worldwide and can pose risks to human health and the environment, as well as easily contaminate waterways and cause extensive harm to non-target species like fish, their presence in the environment has caused significant anxiety in social and scientific development worldwide [5]. Water can get contaminated by direct application into the aquatic system, drifting during spraying, atmospheric fallout as rain and dust, soil erosion, sewage, industrial effluent, and occasionally by spilling, whether intentionally or inadvertently [6]. Since the aquatic environment is where pollutants end up because of basin drainage, it is a particularly vulnerable area. Many different types of contaminants have been shown to enter aquatic habitats, either directly or indirectly. Aquatic production has been drastically reduced as a result of the careless application of chemicals. Pesticides affect aquatic fauna in a variety of ways, particularly fish, which are very valuable from a biological conservation standpoint and have significant economic significance [7]. Pesticide-related environmental pollution is now a major concern for animal and human health as well as worldwide conservation [8,9].

The charged minerals and ions that are present in living things are known as electrolytes. Sodium, potassium, calcium, bicarbonates, and chloride are some of these electrolytes. The main anions in intracellular fluids are bicarbonates and chloride, whereas the main cations in extracellular fluids are sodium and potassium. Based on their activities and ionic capacities, they are divided into divalent and monovalent ions. The divalent ions, magnesium and calcium, are crucial for enzymatic processes, membrane permeability retention, and neuromuscular excitability [10]. The electrolyte balance in an organism is essential for the proper operation of cells and organs because electrolytes are required for osmo-regulatory functions in the bodily systems of living things [10]. According to Gabriel et al. [11], the primary roles of electrolytes in the body are to maintain the appropriate osmotic pressure of bodily fluids, normal neuro-muscular irritability, and control fluid distribution and intracellular and extracellular acido-basic balance. Consequently, changes to an organism's electrolyte balance would have a negative impact on it. Fish living in freshwater environments retain blood ionic concentrations far greater than those of the surrounding water. As a result, they must continually contend with osmotic water inflow and ion diffusion losses over their body's surface and gill epithelium. Since the bodily fluids of fish and the surrounding water are intimately related, one of the most noticeable effects of stress is a disturbed hydro-mineral balance of the body fluids [12].

Moreover, atrazine has been linked to harmful consequences for human health. In human ovarian cancer cells, it enhances aromatase activity [13], and it raises infant mortality and birth abnormalities [14,15]. Both short-term and long-term fish exposure to atrazine concentrations less than 2 mg/L may have sub-lethal effects with biochemical and histological changes in fish tissues [16]. Furthermore, in alkaline soils, atrazine does not decompose easily. It exhibits a carryover effect, which is a generally undesirable herbicide characteristic. Fish are commonly utilized as indicators of environmental pollution, and biochemical changes seen in fish are used to assess the health of aquatic ecosystems [17]. Since fish respond to low concentrations of mutagens, accumulate toxic substances, and play a variety of roles in the trophic web, they are frequently used as sentinel organisms in ecotoxicological studies [18,19]. As a result, the use of fish biomarkers as indices of the effects of pollution is becoming more and more important. The purpose of this study is to assess how atrazine affects a few electrolytes in African catfish juveniles, Clarias gariepinus.

Experimental Location

The experiment was carried out at the Wet Laboratory in the Department of Fisheries and Aquaculture Management, Faculty of Agriculture, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria.

Source of Experimental Fish

One hundred and fifty (150) Clarias gariepinus of equal size (mean length 11.74±2.64cm and mean weight 256.68±1.81g) were sourced from House Tully Fish Farms, Okpuno, Awka, Anambra State, Nigeria. They were transferred in two 50-liter plastic tanks to the laboratory for the acclimation process.

Acclimation and Feeding of Fish

The experimental fish were acclimated in four 150-liter circular plastic tanks containing 150 liters of dechlorinated water for 7 days under experimental conditions at room temperature. Netted materials with central slits were tied to the tops of the tanks to prevent the escape of fish. Water renewal was done every two days.  The fish were fed with a commercial feed at 5% body weight throughout this period.

Experimental Design

The experimental design was a completely randomized design (CRD) with four treatment levels and a control, with each level having three replicates.

Procurement of Test Solutions

A commonly used selective herbicide, Vestrazine (Atrazine 100.0%), was purchased off-shelf from the “Analytical” chemical shop, Eke-Akwa Market, Akwa, Anambra State, Nigeria.

Preparation of a Test Solution

The solution of the chemical in water was prepared by serial dilution using the dilution formula described by Gabriel et al. [20].

Exposure of Fish to Atrazine

Ten C. gariepinus each were introduced individually into 15 aquaria tanks of 1.5m x 1m x 0.5m dimensions, containing 0.00 (control), 0.05, 0.10, 0.15, and 0.20 of atrazine.  Each treatment and control were replicated three times, and the experimental duration lasted for 96 hours. The tank was covered with netted materials and supported with heavy objects to prevent the fish from escaping.

Physico-Chemical Parameters of Water

During the experiment, the following water quality parameters, namely: temperature, pH, dissolved oxygen, nitrate, and ammonia levels of control and other treatment exposures, were determined, and the readings were taken at 0, 24, 48, 72, and 96-hour intervals in three replicates.

The temperature was determined using the mercury-in-glass thermometer, which was inserted in water, and the temperature (°C) reading was taken after four minutes.

pH was determined using a Jenway®-type pH meter (Model 3015). The probe was first inserted in the buffer for 5 minutes to standardize the meter to pH 7. Subsequently, it was dipped into the water, and the static pH was read 60 seconds later. The values of dissolved oxygen (DO), nitrate, and ammonia in experimental tanks during exposure were determined with the standard laboratory method described by APHA [21].

Blood Sample Collection and Preservation

The blood was drawn from a caudal vein known as the vena cava (Clark et al., 1979). Fish were caught individually with a hand net. Blood samples were obtained with 5 ml disposable syringes and a 21-gauge hypodemic needle. During collection, the head of each fish was covered with a piece of cloth for physical restriction with minimal stress [22]. The needle was inserted perpendicularly into the vertical surface of the fish at a point slightly above the openings in the genital papilla. As the needle pierced the vein, blood flowed easily into the syringe, and 3 ml of blood was taken before the needle was withdrawn. The needle was then detached from the syringe, and the 3 ml of blood was transferred into labeled, herparinized bottles. The blood was collected at 0, 24, 48, 72, and 96 hours of the experiment. The blood samples were analyzed at the Lively Stones Medical Laboratory, Rumukparali-Choba Road, Uniport, Choba, Port Harcourt.

Analysis of Electrolytes in C. Gariepinus Exposed to Atrazine

In the laboratory, plasma was separated by centrifugation at 10,000 rpm for 5-8 minutes in the TG20-WS Tabletop High Speed Laboratory Centrifuge. Plasma electrolytes such as Na⁺, K⁺, Ca2+, HCO3-, and Cl^- were determined by using the Hitachi 902 automatic analyzer (Japan), following the method described by Gabriel et al. [20]. All the tests were performed in triplicates.

Statistical Analysis

Dates obtained from the experiments were collated and subjected to ANOVA using Statistical Package for the Social Sciences (SPSS) version 22, and differences among means were separated by the Turkeys Comparative Test at 0.05%. 

Physico-chemical Parameters of Water in the Experimental Tanks  

Table 1 shows the results for the physiochemical parameters of water in tanks of C. gariepinus exposed to different concentrations of vestrazine (0.00, 0.05, 0.10, 0.15, and 0.20 mg/l), respectively, for 96 hours. The results indicated a significant reduction (p<0.05) in the values of dissolved oxygen from 6.67±0.25 in the control to 4.03±0.99 at a 0.20 mg/l concentration of the chemical. Also, significant (p<0.05) increases with increasing concentrations of the chemical were recorded in the values of nitrite and ammonia. While other parameters such as temperature and pH were within the same range comparable to the control in all concentrations of the chemical.

Changes in Electrolyte Levels in the Plasma of C. Gariepinus Exposed to Different Concentrations of Atrazine for 96 Hours

The electrolytes in the plasma of C. gariepinus exposed to acute concentrations of atrazine for 0 hours are presented in Table 2. Generally, the values of all the electrolytes (Na⁺, K⁺, Ca²⁺, Cl^- and HCO₃^-) in the plasma of the exposed C. gariepinus were within the same range, with no significant differences in all concentrations. At 24 hours of exposure (Table 3), a slight increase was observed in the values of Na⁺, K⁺, and Cl^- while the values of HCO₃^- were slightly reduced. However, the values of Ca²⁺ were within the same range, with no significant difference (p > 0.05) in all concentrations. At 48, 72, and 96 hours of exposure of C. gariepinus to varying concentrations of atrazine (Tables 4, 5, and 6), there was a significant increase in the values of Na⁺, K⁺, and Cl^- while the values of HCO₃^- and Ca²⁺ reduced significantly with increasing concentrations of the chemical.

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