Ways to decrease Ocean Acidity:
How can we grow plants or algae in the ocean?
Can we dump the a chunk load of algae into different parts of the ocean?
Is this how we could decrease the acidity of the oceans or we have to wait till some more algae or plants evolve so that there is a greener ocean.
Is there any other natural ways?

The acidity of oceans has increased in the last few years. This is due to change in the climate. The best way to decrease it is to find a solution for climate change. Limiting the use of fossil fuels (to reduce global warming), preventing the harmful outflows from industries into the oceans directly etc. are some of the measures we can take.

When the aquatic environment receives large amounts of rich nutrients, dense growth of plants and algae occurs in the water body.

Algae photosynthetic in nature. In presence of light, algae give off more oxygen and absorb carbon dioxide (which is acidic), thereby decreasing the acidity of ocean water. In absence of light, algae respire more and release carbon dioxide, thereby increasing the acidity of the ocean.

So, dumping a little number of algae can help in reducing the acidity of the ocean because if it increases in number, the ocean will get depleted of many resources.

Hope this helps.
Regards.