Low dissolved oxygen concentrations that occur in many bodies of water when nutrients stimulate the growth of algae that subsequently die and are decomposed by oxygen-using bacteria.
Answer:
I think its Global Climate / Global Warming
Explanation:
This is because glaciers and ice sheets worldwide are melting and adding water to the ocean. And the volume of the ocean is expanding as the water warms.
Answer:
Krakatau volcano on 27 August 1883
