Last Updated: November 25, 2025
Estimated reading time: ~7 minutes
To understand the biological potential of any aquatic ecosystem, one must first master its chemistry. This post shifts focus from the organisms themselves to the environment they inhabit, presenting a rigorous physico-chemical water analysis of four distinct water bodies in the Gujranwala district. By examining detailed datasets on Temperature, pH, Dissolved Oxygen (DO), Conductivity, and Total Dissolved Solids (TDS), we can diagnose the health of these ecosystems. The findings paint a picture of water bodies under significant anthropogenic stress, exhibiting clear signs of eutrophication and chemical volatility that directly impact aquatic life.
Search intent: This post satisfies the user intent to analyze limnological data tables, evaluate water quality based on standard parameters, and interpret the correlation between chemical variables.
Key Takeaways
- Oxygen Dynamics: A strong inverse correlation exists between Temperature and Dissolved Oxygen, with critical lows occurring in June.
- Salinity Stress: High electrical conductivity values (>800 µS/cm) in village ponds indicate significant ion accumulation and potential sewage contamination.
- Alkaline Trend: The water bodies maintained a consistently alkaline pH (7.1–8.9), favoring specific zooplankton communities.
- Monsoon Impact: Turbidity spiked dramatically during the rainy season, altering the light environment and suppressing photosynthetic activity.
Thermal Regulation of Oxygen Regimes
The most fundamental relationship in limnology is the interaction between water temperature and Dissolved Oxygen (DO). The study provides a textbook example of this inverse relationship. Across all stations, the highest temperatures were recorded in June (reaching ~37°C), coinciding with the lowest levels of Dissolved Oxygen (~6–7 mg/L). Conversely, January saw the lowest temperatures (~9–11°C) and the highest oxygen saturation (~11–12 mg/L).
“The highest mean value of DO (11.2±0.01) mg/L was observed in January while the lowest mean value of DO (7.31±0.01) mg/L was found in June… ANOVA showed a significant difference… in value of DO” (Maqbool, 2012, p. 26).
This physico-chemical water analysis confirms that as water warms, its capacity to hold dissolved gas decreases. For students, this is critical: in summer, aquatic organisms face a “double bind”—their metabolic rate increases due to heat (requiring more oxygen), just as the oxygen available in the water decreases. The study’s statistical analysis (Pearson Correlation) quantified this relationship, showing a strong negative correlation (e.g., r = -0.974 at Station 1) between temperature and DO.
Student Note: Biological Oxygen Demand (BOD) often rises in summer due to increased bacterial decomposition, further depleting the limited oxygen available.
Professor’s Insight: If you observe fish gasping at the surface in early morning during summer, it is often due to this thermal suppression of oxygen combined with nighttime algal respiration.
Conductivity and TDS: Markers of Anthropogenic Load
Electrical Conductivity (EC) and Total Dissolved Solids (TDS) are excellent proxy measures for the total burden of dissolved ions, salts, and pollutants in the water. Pristine freshwater typically has lower conductivity. However, the village ponds in this study (Stations 2, 3, and 4) exhibited remarkably high values compared to the flowing Nandipur Canal (Station 1).
At Station 2 (Pipnakha), conductivity peaked at 891.33 µS/cm in August. This is significantly higher than typical freshwater baselines, suggesting “cultural eutrophication”—the enrichment of water by human activity, likely domestic runoff or agricultural drainage. The canal, being a lotic system, had lower maximums (~689 µS/cm) due to constant flushing. The study noted a positive correlation between these parameters and copepod density, implying that the specific species found here (like Mesocyclops) are adapted to high-ion environments.
“Conductivity increased from February to June with increase in temperature… This might be due to organic and inorganic material dissolved in water after decomposition and decreased water volume in summers due to evaporation” (Maqbool, 2012, p. 118).
Student Note: Conductivity measures how well water passes electricity; pure water is a poor conductor. High conductivity = High dissolved ions (salts, nutrients, or heavy metals).
| Parameter | Station 1 (Canal) Peak | Station 2 (Pond) Peak | Interpretation |
|---|---|---|---|
| Conductivity | 689 µS/cm | 891 µS/cm | Ponds act as “sinks” for pollutants. |
| TDS | 448 mg/L | 579 mg/L | High solids indicate eutrophication risk. |
| Turbidity | 158 FTU | 254 FTU | Ponds retain more suspended matter. |
Fig: Comparative peak values for pollution indicators in lotic vs lentic systems (Data source: Maqbool, 2012).
Professor’s Insight: When TDS values exceed 500 mg/L in freshwater ponds, we must investigate potential sewage ingress or excessive fertilizer runoff from nearby fields.
The Optical Environment: Turbidity and Transparency
Light is the energy source for the entire aquatic food web. The physico-chemical water analysis tracked Turbidity (cloudiness) and Transparency (Secchi disk depth) throughout the year. A dramatic “Monsoon Spike” was observed. In July and August, turbidity values soared (e.g., 320 FTU at Station 4), while transparency plummeted (Secchi depth <10 cm).
“Highest turbidity was recorded in summer being maximum in August… while lowest turbidity was noted in winter… This might be due to entrance of muddy water from surrounding areas” (Maqbool, 2012, p. 119).
This seasonal turbidity has two major ecological effects:
- Light Limitation: It blocks sunlight, preventing phytoplankton photosynthesis. This explains the dip in zooplankton numbers during the monsoon (the “starvation effect”).
- Mechanical Interference: Suspended clay and silt can clog the feeding apparatus of filter-feeding organisms.
The inverse relationship between Transparency and Turbidity was statistically significant (ANOVA p < 0.05). For aquatic management, this indicates that during the monsoon, the system shifts from being “nutrient-limited” to “light-limited.”
Student Note: Secchi Disc is a simple black-and-white disk lowered into water. The depth at which it disappears is the “Transparency” value. It is a crude but effective proxy for turbidity.
Professor’s Insight: High turbidity doesn’t always mean pollution; in the monsoon context, it’s often natural soil erosion. However, it temporarily crashes the ecosystem’s productivity.
pH Profiles and Alkalinity
The pH of water determines the solubility of nutrients and heavy metals. Throughout the study period (2011–2012), the waters remained consistently alkaline, with pH values ranging from roughly 6.6 to 8.9. The highest pH values were generally recorded in early summer (June).
“An alkaline trend in pH of all stations was observed… This increase in pH in summer was might be due to the high amount of carbohydrates… [and] photosynthetic activity” (Maqbool, 2012, p. 118).
This alkaline trend is biologically favorable for many freshwater organisms, buffering against rapid chemical changes. The rise in pH during summer is often a biological signature: rapid photosynthesis by algae removes Carbon Dioxide ($CO_2$) from the water. Since $CO_2$ acts as an acid (carbonic acid) in water, its removal causes the pH to rise (become more basic). The drop in pH during winter and monsoon suggests a slowdown in photosynthesis and an increase in decomposition, which releases $CO_2$.
Student Note: Photosynthesis raises pH (consumes $CO_2$). Respiration/Decomposition lowers pH (releases $CO_2$).
Professor’s Insight: A pH above 9.0 can be lethal to fish fry. The values here (max ~8.9) are borderline, suggesting intense algal blooms that could stress sensitive fish species.
The content presented here is an original educational synthesis, reviewed and refined by the Professor of Zoology editorial team. Direct citations from the thesis represent the only non-original text.
Real-Life Applications
Understanding water chemistry is the foundation of environmental engineering and public health.
- Water Treatment Design: The high turbidity data (300+ FTU) during monsoons informs engineers that simple filtration will fail; coagulation and sedimentation tanks are necessary for treating such water for human use.
- Fisheries Viability: The low DO values (~6 mg/L) in summer suggest that these ponds are risky for sensitive fish like Trout but acceptable for hardy species like Tilapia or Catfish (which tolerate low oxygen).
- Pollution Tracing: High conductivity readings serve as a “red flag.” Environmental agencies can map conductivity to trace the source of illegal industrial dumping or leaking sewage lines in village areas.
Exam Relevance: You may be asked to “Calculate the correlation between Temp and DO.” Knowing it is negative and explaining the solubility mechanism is key.
Key Takeaways
- Solubility Law: Oxygen solubility decreases as temperature increases, creating a hypoxic risk in summer.
- Pollution Indicators: High Conductivity and TDS are proxies for pollution; village ponds showed signs of cultural eutrophication.
- Light Limitation: Monsoon rains cause turbidity spikes that suppress primary productivity (algae), rippling up the food chain.
- Biological Buffering: Summer algal blooms raise water pH by consuming acidic $CO_2$.
- Habitat Stability: The canal (Station 1) showed more stable chemical parameters than the volatile, stagnant ponds.
MCQs
1. A strong negative correlation (r ≈ -0.9) was observed between which two parameters in the study?
A. Turbidity and TDS
B. Temperature and Dissolved Oxygen
C. pH and Temperature
D. Conductivity and Copepod Density
Correct: B
Difficulty: Easy
Explanation: The study confirms the standard limnological principle that as water temperature rises, its ability to hold dissolved oxygen decreases significantly (Maqbool, 2012, p. 26).
2. Which event caused the transparency (Secchi depth) to reach its minimum value during the year?
A. Winter fog
B. Summer algal bloom
C. Monsoon rainfall and runoff
D. Industrial discharge
Correct: C
Difficulty: Moderate
Explanation: The “Monsoon Spike” brings soil and silt into the water bodies, causing turbidity to rise and transparency to fall drastically in July/August (Maqbool, 2012, p. 119).
3. What does a pH rise during the summer day typically indicate in a pond?
A. Acid rain
B. High rate of Decomposition
C. High rate of Photosynthesis
D. Release of industrial acids
Correct: C
Difficulty: Challenging
Explanation: Photosynthesis consumes $CO_2$. Since dissolved $CO_2$ forms carbonic acid, removing it makes the water less acidic (more alkaline/basic), raising the pH.
FAQs
Q: What is Eutrophication?
A: It is the enrichment of a water body with nutrients (like nitrates and phosphates), leading to excessive plant growth (algae), high conductivity, and eventual oxygen depletion. The high TDS values in this study suggest eutrophication.
Q: Why is Conductivity higher in summer?
A: Evaporation removes pure water, leaving salts behind and concentrating them. Additionally, warmer water dissolves salts from the sediment more effectively than cold water.
Q: Is alkaline water bad for fish?
A: Mildly alkaline water (pH 7.5–8.5) is usually ideal for freshwater fish. However, extreme alkalinity (>9.0) can damage gills and eyes. The values in this study were generally within safe limits.
Lab / Practical Note
Calibration: Before measuring pH or Conductivity in the field, always calibrate your meters using standard buffer solutions (e.g., pH 4.0, 7.0, 10.0). Temperature Compensation: Ensure your DO meter automatically corrects for temperature, or your oxygen readings will be inaccurate in the summer heat.
External Resources
- Dissolved Oxygen and Water Quality (ScienceDirect Overview)
- Interpretation of Water Quality Parameters (Springer Reference)
Sources & Citations
Thesis Citation:
Studies on Abundance and Diversity of Copepods from Fresh waters, Asma Maqbool, Supervisor: Dr. Abdul Qayyum Khan Sulehria, GC University Lahore, Pakistan, Session 2009-2012 (Submitted ~2017).
Corrections:
If you are the author of this thesis and wish to submit corrections, please contact us at contact@professorofzoology.com.
Note: Placeholder tokens and formatting artifacts from the PDF conversion process were removed for clarity.
Author: Asma Maqbool, Ph.D. Scholar, Department of Zoology, GC University Lahore.
Reviewer: Abubakar Siddiq
Note: This summary was assisted by AI and verified by a human editor.
Disclaimer: This analysis is intended for academic reference; environmental data reflects specific conditions of the study year and location.
Invitation: We welcome contributions from environmental chemistry labs to expand our database of regional water quality profiles.
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