What are the two major concerns over using fossil fuels for energy?

They cause pollution and are nonrenewable.

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Answerair masses develop near the equator are warm; tropical air mass

When a lake, river or other aquatic  system  becomes  eutrophic, it can have serious negative effects on other organisms like fish, birds and even people.if an algal bloom is so bad that it causes wide-spread death  in  the  water, the organisms that die will all sink to the bottom and start to decompose.