when an accident happens in the sea due to collision of ships, there is a huge amount of oil spill in the sea .how does this affect of eco system?what spices of the marine life are affected by it and how?
Do you mean species?
There are many resour4cesw you can find by Googling "oil spill". For example:
http://www.evostc.state.ak.us/recovery/status.cfm