Zebra mussels can be a nuisance in novel ecosystems. When introduced in a non-native ecosystem with no natural predators, they reproduce rapidly displacing native mussels. Zebra mussels take up much of the algar that feeds the other native species hence starving them to death and causing their numbers to plummet. In addition, they attach to the other mussels and clog up power plants, that use the local water, water intakes.
Today, the atmosphere holds about 21 per cent oxygen. ... When the first simple organisms appeared in the oceans more than 3.5 billion years ago, the atmosphere was mostly nitrogen, hydrogen, water vapor, and carbon dioxide
