How is oxygen important underwater?

Question

I'm doing this project for bio using the aquatic plant of elodea densa and we're comparing oxygen production with different pollutants, and I just need to know how oxygen is important to an underwater ecosystem.

Answer 1

The project Is that you again Annie?

and will not give up??

The project is done!! You didn' hear?

JonJohn is that correct????? Done!!!

Answer 2

There is a short answer and pretty long answer for this. Right now, I think I will stick to the short answer.

Animals (and plants also) need to breathe underwater. And the source of oxygen underwater is either what comes from atmosphere through water mixing and gas diffusion or photosynthesis. In a balanced system, you can assume that you need oxygen needs to come from both sources (as this is a short answer, I will leave out the details). So, if the oxygen content goes down, the plants die eventually and animals definitely die pretty quickly. That is one reason it is important.

Second is about decomposing plant or animal matter. There are two kinds of bacterias that decompose dead matter - one kind breaks down stuff using oxygen (kind of like we use energy) and output is pretty healthy for the ecosystem - releases the nutrients fully and properly and carbon dioxide. The other kind uses methanisis (oxygenless) and will prevail when there is lack of oxygen, releasing methane and other outputs are more complicated, like for example, can increase acidity etc. That is the second reason.

Other important point to remember is, the time you get into a low oxygen situation, the healthy balance (if that's what you call healthy) is probably lost. The less there is oxygen, the more the above two things I mentioned, and becomes a feedback mechanism, making things worse - eventually, the water body becomes eutrophic, basically lot of nutrients but not a lot of life. A different ecology evolves that can work with these conditions.