Biology Reference
In-Depth Information
related aspects, such as temperature rise (see also Chap.
18
by Bartsch et al.), ocean
acidification (see also Chap.
19
by Roleda and Hurd.), stratospheric ozone depletion
and solar UV-B radiation (see also Chap.
20
by Bischof and Steinhoff), marine
eutrophication and pollution (see also Chap.
21
by Teichberg.), as well as invasive
seaweed species (see also Chap.
12
by Andreakis and Schaffelke.) and aquaculture
(see also Chap.
22
by Buchholz et al.), are addressed in more detail in separate
chapters throughout this topic.
One of the most important issues is the scarce basic knowledge on the seaweeds
communities over large areas. Although advances have been made in some regions,
such as central/southern Chile, southern Australia, and New Zealand, seaweed
communities of, e.g., the fjord region of southern Chile, the Argentinean region,
and many sub-Antarctic islands are poorly known, partly due to their remoteness.
The lack of studies on species diversity, community structure, and function of
seaweeds in these locations impede suitable estimations on their contribution to
the global geochemical fluxes, the potential genetic loss due to environmental
shifts, and, in general, their conservation status. These are basic elements to
understand the potential for tolerance and resilience in scenarios of global change
(Harley et al.
2006
).
Due to the closeness of the Antarctic ozone hole, the increase of solar UV-B
radiation and resulting adverse effects on the biota of the cold-temperate region in
the southern hemisphere is of a concern. Considering the latitudinal gradients of
UV radiation and episodes of stratospheric ozone depletion reaching latitudes as
low as 40
S (Orce and Helblin
1997
), it is reasonable to argue that this factor can
impose geographical barriers to species exhibiting low stress tolerance capacity.
Recently, the potential effects of enhanced ultraviolet radiation on seaweed physi-
ology have been examined in the context of adaptations to the intertidal life both in
the Pacific and Atlantic coasts of Patagonia (Hader et al.
2003
;G
´
mez et al.
2004
;
Huovinen et al.
2006
; Rautenberger et al.
2009
; Huovinen and G
´
mez
2011
).
In some islands of the Southern Ocean, especially in Marion, Kerguelen, and
Macquarie Island, a marked climate change, expressed as increases in temperature
and declines of precipitation, has begun to be examined in the context of global
warming. Because of the closeness of these islands to the APF, a relatively mobile
climatic boundary, the impact of these climate shifts and its relation with, e.g.,
invasion of species in these islands has drawn attention, hitherto for terrestrial
ecosystems (Bergstrom and Chown
1999
). In Tasmania, intensification of south-
ward intrusions of warmer, nutrient-poor East Australian Current waters has been
reported to cause ocean warming and transport of biota to eastern Tasmania. The
shift in large-scale oceanography has been related with a decline in the extent of the
giant kelp beds. Furthermore, overgrazing of seaweeds by a recently established sea
urchin species is affecting fundamentally the rocky reef systems in Tasmania
(Johnson et al.
2011
).
As seaweed communities of the cold-temperate region in the southern hemisphere
are relatively isolated and thus, their structure, function, and biogeographic processes
are strongly dependent on the environmental context, the direct impact of human
activities requires urgent attention. Important questions related with impact of fish
