What does super-saturation of water body with DO cause ?

ANS:A - Eutrophication

Answer : (B) Gas Bubble disease in fish.

Supersaturated water can cause gas bubble disease in fish and invertebrates. Significant death rates occur when dissolved oxygen remains above 115%-120% air saturation for a period of time. Total mortality occurs in young salmon and trout in under three days at 120% dissolved oxygen saturation. Invertebrates, while also affected by gas bubble disease, can usually tolerate higher levels of supersaturation than fish.