Stopping Invasive Species in Ballast Water

Green Mussels in Tampa Bay

Green Mussels in Tampa Bay. Sea Grant photo.

Nearly a century after the first documented introduction of an alien species via ballast water, national and international agencies are finally firming up new regulations to reduce the potential for other invasive species to be transferred.

The U.S. Coast Guard, the U.S. Environmental Protection Agency and the International Maritime Organization — all have proposals on the table that would require ballast water to meet certain standards before discharge. Ballast water can contain many living creatures, including larval forms. Therefore they can be a major avenue for introducing foreign species.

The challenge has been the fact that ballast water is critical to the safety of a ship. The weight of the ballast (placed below the ships waterline) keeps the ship from turning over in rough seas. Exchanging it at sea can be dangerous. Treating ballast water to kill stowaways is technically challenging and new technologies are just beginning to become available.

“Ballast is not really optional, it’s essential to maintaining stability,” notes Bill Richardson, research associate at the Florida Fish and Wildlife Research Institute who conducted a series of tests on ballast water between 2003 and 2006. Ballast has been used for hundreds of years, he adds. “The rocks at Ballast Point were discharged from ships in the early 1800s when Ballast Point was a prominent port for shipping cattle. The accumulated ballast is said to include rock from almost every seacoast in the world.

With the advent of large metal ships, water became the preferred form of ballast and it’s used in nearly every cargo ship. Ballast water is discharged into Tampa Bay at an average rate of a gallon per minute, day in and day out, Richardson notes. Scientists estimate that 65 non‐native plant and animal species have been established in the Tampa Bay estuary, with ballast water considered a possible route of introduction.

Asian green mussels, the fastest‐growing mussel in the world, probably entered Tampa Bay in ballast water in a ship from Trinidad. When they were first discovered blocking an intake valve at a TECO power plant in 1999, experts feared the worst. As it turned out, the mussels are surviving in Tampa Bay but not creating the environmental disaster caused by the zebra and quagga mussels in the Great Lakes where they have consumed so much of the algae that the base of the food web has shifted.

New technology on the horizon. While it’s clear that invasive organisms travel in ballast water, killing all the organisms found in ballast water, in a cost‐effective manner, has been a daunting challenge. However, now there are many new systems that use diverse technology ranging from filtration and deoxygenation to environmentally friendly biocides that are produced onboard from seawater without the addition of chemicals. As of 2011, 34 ballast water management systems have received basic approval and 20 systems have received final approval. Over time, as the technology continues to improve, the Coast Guard expects to implement standards that are 10 times stricter.

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