The answer that will complete the sentence is lack of eutrophication. It is because eutrophication is considered to be important for marine animals as this provides the bodies of water nutrients in which the marine animals need and if they are lacking, the species composition may change, the coral reefs may be destroyed, the oxygen that are dissolved are at low level and what is more serious, dead zones can be formed in which the ecosystem in the marine life may be destroyed or collapse.
