Answer to Question 1
In the United States alone, more than 7000 introduced species (not counting microorganisms) have been documented, of which about 15 cause ecological and economic damage. Invasive species cause an estimated 137 billion in loss and damages in the United States each year. Examples of non-native marine species that are causing problems In the United States include the seaweed Caulerpa taxifolia, European zebra mussels, Atlantic cordgrass, and the European green crab. The seaweed Caulerpa taxifolia, which is native in tropical waters, is used as a decorative alga in salt-water aquariums because it is hardy, fast growing, and not edible by most fish. When it is introduced into suitable new habitats (most likely as a result of the dumping of household saltwater aquariums), it becomes a dominant and persistent species that displaces native seaweeds and other marine life. California has passed a law forbidding the possession, sale, or transport of Caulerpa taxifolia within the state. European zebra mussels probably entered North America in the ballast water of a freighter from Europe and have since proliferated rapidly in waters of eastern Canada and the United States. They have driven out native mussels, altered the ecology of fresh-water lakes and streams, and blocked the water-carrying pipes of power plants and many other industrial facilities. The Atlantic cordgrass has invaded soft-bottom Pacific coasts of California and Washington. The European green crab has invaded the U. S. Pacific Coast and is altering coastal food webs.
Answer to Question 2
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