Source: Conservation Magazine online. Illustration courtesy of University of Michigan.The introduction of exotic species into new environments can pose a major threat to the integrity of natural communities, the existence of rare and endangered species, the viability of living resource-based industries and pose risks to human health.
In the marine environment, any mechanism that can rapidly transport organisms from shallow coastal waters across natural oceanic barriers has the potential to help exotic marine organisms invade new environments. International shipping provides such a mechanism . Modern international shipping practices transport marine and estuarine organisms faster and over longer distances than ever before. Marine pests are regularly transported via ballast water, or the hulls or anchor ropes of these vessels. Now, University of Michigan naval architect Michael Parsons has designed a ballast-free cargo ship that would stop most aquatic species from hitching rides around the world.
Ships take on ballast water for stability when they're not carrying cargo. When a vessel loads ballast water, it also takes up all minute the organisms contained in that water which may include planktonic species, the larvae of bottom dwelling invertebrates and fish, and pathogens. These organisms are released with the ballast water at another port when the vessel loads more cargo. It has been estimated that world-wide, over 3,000 species are transported in ballast water every day.
Instead of hauling contaminated water across the ocean, then dumping it in a foreign port, a ballast-free ship would create a constant flow of seawater through a network of large pipes running from the bow to the stern, below the waterline.
"In some ways, it's more like a submarine than a surface ship," Parsons said. "We're opening part of the hull to the sea, creating a very slow flow through the trunks from bow to stern. You're continuously sweeping water through the ship and out," he said. "So you're always filled with local sea water, not hauling water from one part of the world to the other."