Environmental Engineering Reference
In-Depth Information
Seemingly similar habitats may be differently impacted by invaders. For
example, manipulating the densities of the non-indigenous snail
Littorina
littorea
in two Gulf of Maine salt-marshes with diverging physical conditions
(e.g., with reference to inundation, elevation, drainage and sediment
characteristics), Tyrrell et al. (2008) found that stressing environments
for
Spartina alternifl ora
favored grazing by the snail, resulting in declined
cordgrass productivity.
Cordell et al. (2008) reported the introduction of nine Asian calanoid
and cyclopoid copepods into the Northeast Pacifi c, some of which moved
upstream and invaded the Columbia-Snake River system (USA), illustrating
the potential of some species to colonize new areas, against environmental
gradients (see Byers and Pringle 2008).
A study by Orensanz et al. (2002), presented the fi rst exhaustive review
of marine NIS for the SW Atlantic Ocean (particularly Argentina and
Uruguay). Considered at a regional scale, these authors cited the occurrence
of 31 introduced and 46 cryptogenic species in coastal and shelf areas. Some
of the latter are currently considered as IAS (S. Obenat, pers. comm.). It is
noteworthy that some of the introductions are relatively recent (~ 30 years),
but nonetheless showed striking ecological impacts in the area. For example,
the barnacle
Balanus glandula
developed calcareous belts on rocky intertidals;
Limnoperna fortunei
(a macrofouling bivalve) and
Ficopomatus enigmaticus
(a reef-building polychaete) strongly modifi ed estuarine ecosystems; while
the Pacifi c oyster
Crassostrea gigas
established well-developed reefs which
rapidly expanded along shallow confi ned bays. The case of the Asian kelp
Undaria pinnatifi da
is remarkable. This phaeophyte
modifi ed the benthic
communities and signifi cantly changed the seascape of the Patagonian
coasts where it became established, within a few years. Its fi rst record dates
back to the mid-1990s (Piriz and Casas 1994). A decade ago, Orensanz et
al. (2002) reported its distributional range from northern Peninsula Valdés
(42°05'S) to Camarones (44°48'S). However it has recently been recorded
in Mar del Plata harbor (38º02'S; Meretta et al. 2012), expanding its range
in 4 degrees of latitude in 10 years. The above-mentioned
F. enigmaticus
also deserves a special mention for the area. This highly successful invader
currently dominates the benthos of Mar Chiquita coastal lagoon, a UNESCO
MAB Reserve. Within this lagoon, the polychaete builds calcareous reefs that
range in size from a few cm to ~ 7 m in diameter (Schwindt and Iribarne
2000), and accordingly it has impacted the system by modifying circulation
patterns and sedimentation rates (Schwindt et al. 2001, 2004). By becoming
the dominant suspension feeder, it also plays a signifi cant role in benthic-
pelagic coupling, with the capacity to drive changes in plankton community
structure through selective grazing (Pan and Marcoval 2012).
Summarily, IAS represent one of the primary threats to biodiversity, and
the risks of potential invasions may be increasing due to increasing global