Impact of Copper Toxicity on Oxygen Consumption in Pangasius Fry
Introduction
Oxygen consumption is a key indicator of physiological health in
aquatic organisms. When fish are exposed to environmental pollutants like heavy metals, especially copper, their metabolic responses offer valuable clues about the stress inflicted upon them.
The freshwater edible fish Pangasianodon hypophthalmus, commonly known as striped catfish, is widely cultivated and studied due to its economic and ecological importance.
This blog post delves into a detailed study examining how sublethal concentrations of copper affect the oxygen consumption and metabolic rate in Pangasius fry.
The excerpt is taken directly from a zoology thesis and presents rigorous experimental observations.
Understanding these toxicological responses is crucial for fishery managers, aquaculture researchers, and environmental scientists striving to ensure sustainable fish health and water quality.
The focus keyword — “copper toxicity” — is central to this investigation and recurs throughout the excerpt.
OXYGEN CONSUMPTION IN FRY OF PANGASIANODON HYPOPHTHALMUS EXPOSED TO COPPER
Water can hold a limited amount of oxygen. This is determined by atmospheric pressure, temperature and salinity.
In a natural setting, oxygen is added to water by atmospheric diffusion at the surface by wind circulation (augmented surface diffusion) and by photosynthesis (oxygen is also produced by phytoplankton or algae). Photosynthesis accounts for most of the oxygen in water.
The oxygen content of water increases with increasing atmospheric pressure and decreases with increase in temperature and salinity. The amount of oxygen in water is measured as milligrams per liter [mg/L) and is called dissolved oxygen (DO).
Pollution of aquatic ecosystem with wide array of xenobiotic compounds has become a big problem to the aquatic flora and fauna and this menace is of a great concern to mankind.
The contaminants let out into the water bodies from industrial and agricultural areas are highly persistent and their levels fast reach to life threatening in terms of both space and time (Brack et al., 2002; Diez et al, 2002).
Depletion of oxygen content occurs in the water medium when pesticides, sewage, chemicals and other effluents containing organic matter are discharged into water bodies.
In the aquatic medium the most important manifestation of the toxic action of chemical is the over depression or stimulation of respiratory activity.
Causes of Oxygen Depletion in Water
According to Wynne and Wurts [2011], naturally a number of conditions may develop which result in oxygen depletion and dissolved oxygen at levels less than 3 mg/L is insufficient to support aquatic life [e.g. fish).
Oxygen depletions are typically associated with:
- Hot, cloudy, still weather
- Sudden death of phytoplankton or algal bloom, “bloom crash”
- Stratification and mixing in deep ponds
- High fish biomass and organic waste
Measuring Oxygen Consumption
Living organisms are distinguished from non-living things by the process of respiration. It is a vital process to generate energy.
The rate at which oxygen is used by the tissue (micro liters) or oxygen used per milligram of tissue per hour is called unit oxygen consumption or metabolic rate.
The term fish kill, known also as fish die-off, is often due to reduced oxygen in water. Toxicity is a real but far less common cause.
According to Skidmore [1970], cannulating the blood system of fishes helps measure pollutant concentrations and understand their mode of action.
All toxicants especially heavy metals alter the oxygen consumption rate at a particular concentration.
Measurement of oxygen consumption has been used to determine the effects of toxicants on overall metabolism.
Literature and Previous Studies
Oxygen consumption and energy utilization are directly proportional.
Monitoring oxygen consumption is one of the sensitive bioassay techniques. Abel and Garner (1986) reported that animals in polluted waters are often exposed to sublethal levels of toxicants.
Studies by Houlihan et al. (1995) showed protein synthesis can account for up to 79% of oxygen consumption during rapid growth in herring larvae.
According to Rafia Sultana and Uma Devi (1995), studies on oxygen consumption help assess toxicant stress.
Several studies (Jezierska & Sarnowski, 2002; Fafioye et al., 2008; Andre et al., 2008; Ololade & Oginni, 2009; Eyckmans et al., 2011) have reported oxygen consumption variations in fish exposed to heavy metals like copper, nickel, mercury, and cadmium.
Experimental Setup
Fish were collected and acclimatized in lab conditions.
Oxygen consumption (routine rate) was measured using a respiratory chamber equipped with an oxygen electrode. The temperature was kept constant at 29 ± 2° C.
The present experiment was carried out subjecting the fish fry to a sublethal concentration of copper [0.0915 ppm].
Oxygen measurements were made at intervals of 24 hrs, 48 hrs, 96 hrs, 10 days, 20 days and 30 days.
Results Summary
A percent decrease in oxygen consumption on exposure to copper over controls was 6.55%, 15.18%, 14.07%, 18.48%, 24.56%, and 36.57% respectively. Metabolic rate also decreased significantly over time.
Interpretation and Discussion
Results clearly depict inhibition in oxygen consumption and metabolic rate in fish fry exposed to copper. Similar results have been observed by other researchers in different fish species.
Causes include impaired ion regulation, biochemical disturbances, and direct respiratory distress.
Copper interacts with the mitochondria, affecting energy metabolism.
These findings underscore oxygen consumption as a reliable physiological indicator of toxic stress in fish.
Source Citation
Researcher: Pratima Kumari, S
Thesis Title: Copper toxicity on fry of fresh water edible fish pangasianodon hypophthalmus
Supervisor: Prabhakara Rao, Y
University: Andhra University
Year of Completion: 2012
Exit Page Number: 85
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