Ships' ballast water - one new alien species enters the Med every nine days

Mediterranean states have started discussing measures to control the discharging of ship's ballast after scientists found that one alien species enters the Med every nine days, mostly with the water which the ships discharge after arriving from other regions.

“The Mediterranean Sea is a world’s major shipping area with more than 300,000 port calls per annum and more than 10,000 ships transiting this busy highway every year. Ballast water discharges by ships can have a negative impact on the marine environment,” said Fréderic Hébert, Director of the Regional Marine Pollution Emergency Response Centre (REMPEC).

“Large tankers and bulk cargo carriers, commonly operating in the Mediterranean, use a large amount of ballast water, which is often taken on in the coastal waters in one region after ships discharge wastewater or unload cargo, and discharged at the next port of call, wherever more cargo is loaded”.

There are hundreds of organisms carried in ballast water, including plants, animals, viruses and bacteria. These materials often include non-native, nuisance, exotic species that can cause extensive ecological and economic damage to the aquatic ecosystem – generally referred to as alien or invasive species.

Invasive alien species have serious economic, environmental and human health impacts and are now recognized as one of the greatest threats to biodiversity globally. In marine and coastal environments, invasive species have been identified as one of the four greatest threats to the world’s oceans.

In particular, they can have economic impacts on fisheries by smothering or killing fish and other species, tourism (jellyfish), destruction of facilities, settling on buoys, vessels and ropes, and aquaculture harvests. They also have negative impacts on the ecosystem, competing with Mediterranean native species for food and space and modifying the habitat.

Others can also have health impacts due to their toxicity, like the micro-algae Alexandrium acatenella responsible for creating "red tides", which is a species known for producing paralytic shellfish poisoning (PSP) toxins. The toxins can affect humans, other mammals, fish and birds. It is responsible for numerous human illnesses and several deaths after consumption of infected shellfish.

“Ships’ ballast water is of particular concern as a vector of introduction of invasive alien species in the Mediterranean”, said Maria Luisa Silva, Officer-in-Charge of the UNEP Mediterranean Action Plan. “Research shows that the Mediterranean marine ecosystem and resources have been and continue to be severely compromised by invasive species, and remain at high risk of further invasion as maritime traffic escalates. Scientists estimate the rate of biological invasions in the Mediterranean to be one new species entry every nine days”.