1 -

Occurs - happens

2 -

Coral goes white because humans throw bleach into the ocean because of the bleaching event. Corals can survive bleaching but suffer mortality.

3 - 

4 -when carbon dioxide from factories go in the ocean the coral die because the water gets warmer. also from gas and coal.

5 - Layers of the Ocean

Twilight Zone - 3,300 ft deep 

Midnight Zone - 13,00 ft deep

Abyss Zone - 20,00 ft deep

Trench Zone - 24 to 36 ft deep

6 -

If plankton died the food  web would all die, e.g. above.