Environmental Engineering Reference
In-Depth Information
results at more than 12 billion Euros annually (Shine et al. 2010 ). However, this cost
includes terrestrial impacts on habitats and on services. For the aquatic sector the
costs are thought to be 10-15 % of this amount.
Transfer and Impacts of Potentially Harmful
Phytoplankton Species
Ballasted seawater may contain 30->100 phytoplankton species including those
being potentially toxic or others forming harmful algal blooms. These are unicel-
lular microalgae, most usually these are diatoms and dinofl agellates, and may occur
at levels of a thousand to a million or more cells per litre (Hallegraeff 1993 , 1995 ,
1998 ). As a result these have great potential for global transfer and 'successfully'
introduction of these species.
Over 100 years ago it was claimed that the centric diatom Odontella sinensis ,
known from tropical and subtropical coasts of the Indo-Pacifi c, had arrived in the
ballast water of a merchant vessel, and had spread to become suffi ciently abundant
in the North Sea to result in plankton blooms in 1903 (Ostenfeld 1908 ). These
blooms had no known harmful effects. It was not until the 1970s, the introduction
of further centric diatom, Coscinodiscus wailesii , to the North Sea which clogged
fi shing nets due to extensive mucilaginous accretions (Boalch and Harbour 1977 ;
Laing and Gollasch 2002 ). For many other phytoplankton species their origin is
unknown which is also due to the taxonomic uncertainties with many phytoplankton
species (see cryptogenic species below).
In Australia, an investigation found that 80 % of vessels contained approximately
30 culturable diatom species, including the potentially toxic Pseudonitzschia spe-
cies that can cause Amnesic Shellfi sh Poisoning (ASP) (Forbes and Hallegraeff
1998 ) which can debilitate humans following consumption of contaminated shell-
fi sh. Further, cultures of viable dinofl agellates Alexandrium catenella , A. tamarense
and Gymnodinium catenatum , all known for the toxins they can produce and conse-
quent impacts on human health, were extracted from the ballast water of 5 % of the
vessels arriving from Japan and Korea (Hallegraeff and Bolch 1992 ). Studies of
vessels entering British ports confi rmed the presence of A. minutum , A. catenella
and A. tamarense in 17 % of ballast water samples (Hamer et al. 2001 ). In one case, a
single ballast tank contained as many as 300 million viable Alexandrium tamarense cysts
(Hallegraeff and Bolch 1992 ). The occurrence of such numbers in ballast water
discharges may well have contributed to the widespread distribution of this species.
In addition, the potentially ichthyotoxic dinofl agellate Pfi esteria piscicida has been
confi rmed using molecular probes in ballast water entering US ports (Doblin et al.
2002 ). In conclusion, the presence of potentially harmful marine microalgae in bal-
last water has been fi rmly established.
Dinofl agellates do not always need to form blooms in order to result in toxic
events. They can occur at comparatively low densities suffi cient to render cultured
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