Environmental Engineering Reference
In-Depth Information
2000; Godwin 2003; Hewitt
et al
. 2004). The nature and magnitude of many of
these pathways are primarily shaped by commerce and trade patterns across glo-
bal, regional, and local scales. Depletion of resources, exploitation of new reserves,
and advances in technology may all result in changes to patterns of trade. The
establishment of new source regions of goods and commerce has the potential to
greatly increase and change invasion regimes within recipient locations (Taylor
et al
. 1999; Meyerson and Mooney 2007). Since the majority of world trade relies
on ship transport (Minchin and Gollasch 2003), the primary pathways for marine
AIS introduction are those associated with international and domestic shipping,
via ballast water discharge (Carlton and Geller 1993; Ruiz
et al
. 2000), and fouling
on vessel hulls (Gollasch 2002; Godwin 2003) and other submerged areas such as
sea-chests (Coutts and Dodgshun 2007).
Ballast water is used in commercial vessels to stabilize the vessel en route, and is
uploaded or discharged depending on the amount of cargo onboard (Fig. 14.2).
Ballast water can contain an assortment of organisms at various stages of devel-
opment, including plankton, crustaceans, fi sh, larvae, eggs, or cysts (Williams
et al
. 1988; Carlton and Geller 1993). h e uptake and release of ballast water (and
its associated biota) has the potential to transport and introduce entire assem-
blages of marine organisms from one bioregion to another (Carlton and Geller
1993). Ballast water may also include sediments that accumulate in the bottom
of the tanks, providing a suitable habitat for the survival of species with resistant
life stages or resting cysts (e.g. dinofl agellates) as well as adult stages of benthic
organisms. Transfer via ballast water has been implicated in the introduction and
Fig. 14.2
Ballast water overfl owing from inspection ports on a tanker vessel
undertaking mid-ocean ballast water exchange. Photo: T. Dodgshun, Cawthron
Institute.
