Oil slick causes mass scale death of fish due to

Options

A. Clogging of gills
B. Non-availability of oxygen in water
C. Non-availability of food
D. Disruption of food chain.

Answer

### Step-by-Step Solution:

1. **Understanding Oil Slick**:
- An oil slick refers to the layer of oil that spills over a water body, such as a sea, ocean, or pond. This spillage often occurs due to accidents involving ships or oil tankers.

2. **Impact on Water**:
- Oil is not soluble in water, which means it floats on the surface. This creates a barrier between the water and the atmosphere, affecting the oxygen levels in the water.

3. **Fish Respiration**:
- Fish breathe by taking in water through their mouths. This water passes over their gills, where oxygen dissolved in the water is extracted and absorbed into their bloodstream.

4. **Clogging of Gills**:
- When an oil slick occurs, the water that fish intake is contaminated with oil. The oil can enter the gills of the fish, where it can clog the gill structures.

5. **Consequences of Clogged Gills**:
- The clogging of gills prevents fish from effectively extracting oxygen from the water. Without sufficient oxygen, the fish cannot survive, leading to their death.

6. **Conclusion**:
- Therefore, the primary reason for mass scale death of fish due to oil slick is the clogging of gills, which inhibits their ability to respire.

### Final Answer:
Oil slick causes mass scale death of fish due to **clogging of gills**.

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