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Luis Herrera Mesa, Full Professor of Zoology
Spread of invasive alien species through ballast water
Identified as a major threat to the world's oceans and biodiversity conservation. A large issue of marine species identified as invasive species are transported via ballast water from ships or ship hulls.
In order to prevent the spread of IAS through ballast water the International Maritime Organization agreed in 2004 on the international agreement for the control and management of ships' ballast water and sediments, which aims to prevent the spread of harmful aquatic organisms from one sea to another by establishing standards and procedures for the management and control of ships' ballast water and sediments. The agreement to which numerous countries have acceded or ratified entered into force last September 8, 2017.
The problem of the spread of IAS by ships has intensified in recent decades due to the volume of maritime traffic that continues to increase. The effects in many areas of the world have been devastating. Quantitative data show that the rate of invasions continues to increase at an alarming rate. The spread of invasive species is recognized as one of the greatest threats to the ecological balance and economic well-being of the planet. These species are causing enormous damage to biodiversity and to the valuable natural wealth of the seas and oceans on which we depend. In the Mediterranean, more than half (54%) of marine alien species are thought to have been introduced via ships' ballast water or embedded in hulls. Macrophytes account for 30% in the western Mediterranean and only 10% in the eastern Mediterranean. Some researchers estimate that about 300 species have been introduced through ballast water, about 100 species through the Suez Canal, about 50 species of macroalgae through oyster farming, about 20 species through aquaculture and about 18 species through the aquarium trade.
The direct and indirect effects and the damage to the environment are often irreversible. In fact, ballast water carries a multitude of bacteria, small invertebrates, algae, eggs, cysts and larvae of different species that cause serious ecological effects and health problems. For example, certain cholera epidemics appear to be directly associated with ships' ballast water. The cholera bacterium (Vibrio cholerae) is found in marine ecosystems in phytoplankton and zooplankton.