What would be a negative impact on the environment from a large-scale mining effort in the ocean?

The offshore mining or the mining in the ocean has a great negative impact on the surrounding environment. Some of the impacts are as follows-

It can cause damage to the existing ecosystem, including the fishes, corals and other marine organisms.Any leakage in the pipelines, will pollute the oceanic water, thereby contaminating and releasing different harmful toxic chemicalsCatastrophic oil spills and blow out in the oil wells could take place.If accident happens, then a lot of people would die.