13 September 2007
Ships as a Cause of Non-Indigenous Species Introduction
Researchers from New Zealand have recently demonstrated that ships' sea-chests, the
intake areas for ballast water in the hulls of large ships, are responsible for introducing nonindigenous species into the world's seas. As might be expected, international vessels pose
the greatest threat. The researchers call for more effective treatment of sea-chests, in order
to limit the biological risks posed by non-indigenous species.
The sea-chests of a ship are small underwater compartments in the hulls through which sea water is drawn in
(or discharged) for ballast, engine cooling and fire fighting. In recent years, the potential of sea-chests for the
introduction of Non-Indigenous Marine Species (NIMS) has been highlighted by several scientists. A nonindigenous species (also known as alien, exotic, invasive or non-native) is an organism that did not formally
evolve in a particular geographic location. Non-indigenous species can be introduced in new locations either
intentionally or accidentally. International shipping is generally considered to be responsible for the majority of
accidental NIMS introductions (e.g. by ballast discharges, hull fouling or anchors). However, this mechanism of
NIMS introduction is poorly understood.
In this regard, researchers from New Zealand have performed a vessel sea-chest study in order to assess
their role as a dispersal mechanism for marine species. To this end, they surveyed 53 sea-chests from 42
vessels (a vessel may have more than one sea-chest) at 3 maintenance facilities in New Zealand. These seachests were sampled between May 2002 and November 2004 after an average in-service period of about 2.5
years.
Their analysis reveals that:
• For the 53 sea-chests sampled, 150 different organisms were identified. Between 1 and 33
organisms were recorded per sea-chest.
• 40% of the organisms found in sea-chests were indigenous, 15% introduced, 10% non-indigenous
and 35% of unknown origin.
• Compared to domestic or coastal vessels, international vessels show the highest proportion of non-
indigenous species.
• Longer in-service periods and older anti-fouling paints are correlated with greater numbers of
organisms.
The authors conclude that the diversity of organisms accumulated in sea-chests can be explained by several
factors. The first factor is that various sessile, sedentary and mobile organisms are likely to be involuntarily
vacuumed inside sea-chests during ballasting operations. Secondly, anti-fouling paints which are intended to
limit the presence of organisms are not completely efficient due to the extreme water flows occurring in seachests. Overall, they highlight that, internationally, sea-chests present a risk of transfer of NIMS and may be
responsible for the spread of both indigenous and introduced species to new locations in New Zealand.
They suggest that this issue could be overcome by treating sea-chests more effectively, using thermal
treatments to limit the accumulation of unwanted organisms in sea-chests. Furthermore, they point out that
vessels should be managed as a whole rather than managing different mechanisms (e.g. ballast water, hull
fouling, sea-chests) in isolation to limit the biosecurity risk posed by NIMS.
In Europe, shipping is the primary vector for introducing NIMS. Thus, the results of this study provide new
insights into how to further reduce this phenomenon.
Source: Coutts, A. D. M. and Dogshun T. J. (2007) “The nature and extent of organisms in vessel sea-chests: a protected mechanism
for marine bioinvasions”, Marine Pollution Bulletin 54:875-886.
Contact: [email protected]
Theme(s): Marine ecosystems.
Opinions expressed in this News Alert do not necessarily reflect those of the European Commission
To cite this article/service: "Science for Environment policy": European Commission DG Environment News Alert Service, edited by
BIO Intelligence Service.
European Commission DG ENV
News Alert issue 77
September 2007
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