"Gas bubble disease" is caused by:

Correct option is B

The correct answer is (b) Excess dissolved oxygen in drinking water.
Gas Bubble Disease (GBD) occurs when water is supersaturated with dissolved gases, particularly oxygen or nitrogen. When this happens, excess gas forms bubbles in the tissues or bloodstream of aquatic organisms, leading to severe health issues and even death.
Mechanism of Gas Bubble Disease:
· When water contains more dissolved gas than it can normally hold under standard conditions (i.e., supersaturation), aquatic organisms can absorb the excess gas.
· These gases come out of solution inside the organism, forming bubbles in the gills, bloodstream, eyes, and other tissues.
· These bubbles disrupt normal body functions and can lead to tissue damage, impaired circulation, and death.
Symptoms of Gas Bubble Disease in Fish:
· Bubbles in the fins, eyes, and gills
· Buoyancy issues (swimming upside-down or erratically)
· Bleeding or tissue damage
· Lethargy and reduced feeding behavior
Why Other Options Are Incorrect 1. (a) Excess nitrite in drinking water:
· High nitrite levels cause methemoglobinemia or "blue baby syndrome" in humans, not gas bubble disease.
2. (c) Excess carbon dioxide in drinking water:
· High levels of CO₂ lead to respiratory acidosis in aquatic organisms but do not cause gas bubble disease.
3. (d) Excess chlorine in drinking water:
· Chlorine exposure can cause chemical burns and damage to gills in fish, but it is unrelated to gas bubble disease.
Information Booster 1. Causes of Supersaturation:
· Rapid temperature changes in water.
· Leaking or malfunctioning pumps in aquariums or aquaculture systems.
· Water flowing over high waterfalls or turbulent water surfaces.
2. Prevention of Gas Bubble Disease:
· Aerate water properly to release excess dissolved gases.
· Monitor dissolved gas levels using appropriate sensors.
· Avoid sudden pressure changes in water systems.
3. Impacted Organisms:
· Fish, amphibians, and aquatic invertebrates are susceptible to gas bubble disease.
Additional Knowledge · Supersaturation occurs when the concentration of dissolved gases exceeds the water's normal capacity due to changes in pressure, temperature, or turbulence.
· Dissolved Oxygen (DO) Levels:
· Normal levels in healthy aquatic systems: 5-10 mg/L.
· Supersaturation occurs when DO exceeds 110% saturation.