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Biological Invasions by Marine Jellyfish 249
14.7 Transport of Invasive Marine Jellyfish
The primary vector for the introduction of non-indigenous species into
marine ecosystems is widely perceived to be shipping traffic, which enables
organisms to cross natural oceanic barriers (Carlton and Geller 1993; Holland
2000; Chap. 4). Over the past 20–30 years, increases in the speed, size, and volume
of shipping traffic on a global scale, along with stricter regulation of the
use of anti-fouling paints, have resulted in concomitantly accelerating rates of
non-indigenous species introductions into marine ecosystems (Ruiz et al.
1997, and references therein). In addition, oil and gas drilling platforms are
routinely moved over large distances, sometimes between ocean basins, as
new fields or markets emerge for exploration. In terms of the total number of
fixed platforms in the sea, individual drill platform movements are extremely
small. Still, the relocation of even a single platform via ocean towing will
transport not only individuals, but perhaps entire exotic populations or
mature communities.
Both ballast water and hull fouling are plausible mechanisms of jellyfish
introductions. While ships carry large volumes of ballast water containing an
enormous variety of potentially invasive organisms (Carlton and Geller
1993), only the holoplanktonic ctenophores appear suited to ballast watermediated
introduction. By contrast, hull fouling transport, either by ships or
on drill platforms, is more likely for the hydrozoans and scyphozoans, owing
to their bipartite life-histories that include a sessile polypoid stage. Despite
the early observations described by Galil et al. (1990) of C. andromeda
medusae swimming into the Mediterranean through the Suez Canal, it is more
likely that translocation occurs not by the medusa stage, but rather by the sessile
polyps, a counterintuitive argument supported by recent molecular
genetic research (Dawson et al. 2005).
The aquarium trade has also received extensive attention as an important
mode of marine introductions of ornamental fish and invertebrates. Recently,
Bolton and Graham (2006) reported on incipient introductions resulting from
the transport of ‘live rock’ materials associated with the aquarium trade.‘Live
rock’, either naturally collected or artificially cultured, refers to rock coated
with algae, invertebrates, and microorganisms that is used for the purpose of
increasing the aesthetics of home aquaria. Live rock became apparent as a
potential vector of invasive organisms when material collected in the Indo-
Pacific (likely Indonesia or Fiji) was imported to a local pet store in Florida
(USA). Several weeks after purchase, a home aquarium enthusiast reported
the appearance of numerous small jellyfish that ultimately were identified as
‘upside-down’ jellyfish Cassiopea spp., a recognized globally invasive genus
(Sect. 14.3.2). The fact that the live rock trade in the United States receives little
attention, much less appropriate quarantine measures, makes it a concern
for aquatic invasive research (Bolton and Graham 2006).