INVASION OF THE ALIEN CREATURES

摘要

Ecologists estimate that every six months a new invasive species begins carving out a spot for itself in the Great Lakes ecosystem. Many arrive as stowaways on shipping vessels that travel up the St Lawrence Seaway, hiding out in ballast water until it's discharged for cargo-leaving the aquatic invaders free to move about the continent. In 2006, one of the most lethal infectious diseases affecting fish populations, viral hemorrhagic septicemia, killed tens of thousands of fish in Lake Erie. Scientists believe it might have arrived in ballast water.