Benthic Community and Climate Change - Marine Ecology in a Changing World - page 130

conditions change (Helmuth et al . 2006b). The impact of climate change on
intertidal invertebrate distribution has been the focus of a growing number
of recent studies. For instance, the blue mussel Mytilus edulis has been
reported to have extended its distribution north by 1000 km between 1977
and 2002, from the Norwegian mainland to Svalbard Island (Salvigsen et
al . 1992, Weslawski et al . 1997, Berge et al . 2005), possibly as a consequence
of the dispersal of planktonic larvae from a source population on the
Norwegian mainland by a northward transport of warm Atlantic water
into the Greenland Sea region in recent years (Berge et al . 2005).
Hawkins et al . (2008) have reported a general polewards retreat and
decrease in the abundance of cold water-adapted species and an advance
and increase in the abundance of warm water species. Although climate
change has quite clearly had and will continue to have a large impact on at
least some species in rocky intertidal ecosystems, this impact is not likely
to be evident everywhere (Helmuth et al . 2006b). For example, in a study
conducted along the Chilean coast, where the last 57 years have evidenced
a weak warming trend, the range boundaries of species did not change
beyond chance expectation (Cane et al . 1997). These fi ndings suggest the
impossibility of making generalizations about poleward shifts in species'
ranges because of differences in regional warming trends (Rivadeneira
and Fernandez 2005). Responses to climate change are also species specifi c
and depend upon life history and other ecological traits (Hawkins et
al . 2008). As underlined by Helmuth et al . (2006b), ecological responses
to climatic variability within the intertidal ecosystem can only be fully
elucidated through an integrated approach linking changes in a variety of
environmental parameters to the physiological and ecological responses of
organisms over a range of temporal and spatial scales and within a hierarchy
of biological organization.
Can Climate Change Trigger Biological Invasions?
Marine ecosystems have been subject to changes in species composition;
many of the species moved by humans—deliberately or otherwise—beyond
their native range become established and spread in their new habitat
(Vitousek et al. 1997). Some species have been introduced accidentally
via ballast water, soil, or as crop seed “contaminants” and others have
been intentionally introduced as ornamentals, food, or fi ber products
(Vilà et al . 2007). Intercontinental shipping and the commercial transport
of aquaculture products from one coast to another have also played an
important role (Wolff and Reise 2002). However when they are introduced,
only about 10% of these species actually become established and spread
in their new environments, and only a small fraction are likely to induce
changes to the recipient ecosystem (Williamson and Fitter 1996). Nowadays,