A Only one variable changed
Abiotic factors are factors that include non-living parts of the environment which could be significant or essential to living organisms. Water is a non-living environment and it helps in giving life to plants and other organisms. Thus deemed abiotic.
Fishing I think would be onw
The ocean acidification is generally caused by the vast amounts of carbon dioxide that humans release in the air gettting absorbed into the ground, causing the PH of the water to rise.
Hopefully this helps!