Raul A Ugarte1 James S Craigie2 And Alan T Critchley1

'Acadian Seaplants Limited, 30 Brown Avenue,

Dartmouth B3B1X8, Nova Scotia, Canada

2National Research Council of Canada,

Institute for Marine Biosciences, '4'' Oxford Street, Halifax

Climate is recognized as a key driver in determining the distribution and ultimate geographical boundaries for both terrestrial and marine plant species. The western north Atlantic environment encompasses the Arctic, cold temperate, and the warm temperate Carolina regions, the first two of which influence and control the species distribution of marine flora in the Canadian Maritime Provinces. The southern limit for the Arctic and cold temperate seaweeds is along the coastline from Cape Cod, MA, to Long Island Sound. Luning (1990) presented an extensive analysis and discussion of the limits of both intertidal and sublittoral seaweed speciation and distribution in the north Atlantic in relation to ecophysiological factors such as temperature, degree of exposure, salinity, and available light.

Fluctuations in the surface temperature of the Earth over the last 250,000350,000 years have been reflected in cyclic changes in the greenhouse gases such as methane and carbon dioxide trapped in glacial ice (Ruddiman, 2005). Approximately 5,000 years ago, the cyclic decline in methane concentration expected for the present interglacial period was interrupted leading Ruddiman to suggest that human activity may have begun to influence the climate much earlier than had been generally considered. With the improved records over the past 150 years, trends showing increases in both atmospheric and water temperatures that correlate to human activities during the industrial age are developing (Collins et al., 2007). According to the International Panel on Climate Change - IPCC (2007), the temperature of the planet has increased 0.65 ± 0.15°C between 1956 and 2005, and the ecological impact of such a climate change is already being documented worldwide in every ocean and in most major terrestrial and aquatic taxonomic groups (Parmesan, 2006). Although early in the projected trends of global warming, ecological responses to recent climate change are already clearly visible (Gian-Reto et al., 2002), meta-analyses of studies done for more than 1,400 marine and terrestrial species have demonstrated that the current increased temperature is already affecting 40% of them and that 82.3% of these species are shifting in the direction expected according to their physiological constraints (Root et al., 2003). An increase in the species diversity of the fish fauna has been already detected in the North Sea and has been related to climate change (Hiddink and Hofstede, 2008). These kinds of changes would not only impact the marine biodiversity but are expected to produce local extinctions in the subpolar regions, the tropics, and semi-enclosed seas (Cheung et al., 2008a, b ).

Few reports on the effects of current climate change on macroalgae have been found in the literature, but these describe significant changes in the distribution and abundance of algae. For example, Pedersen et al. (2008) documented a significant change in seaweed community structure and related this to an increase in seawater temperature during a 28-month study in the littoral zone in Long Island Sound. Sagarin et al. (1999) reported a massive decline in Pelvetia compressa cover by revisiting a location in Baja California that was well monitored 60 years earlier. Simkanin et al. (2005), who revisited 63 locations along the coast of Ireland after a lapse of 45 years, also reported significant changes in the abundance of several seaweed species in the sublittoral zone. Although they were cautious about associating these changes with climate change, long-term trends seen in these kinds of surveys can be obscured by short-term fluctuations in species composition. However, Berecibar et al. (2004), by revisiting several locations after 45 years, clearly demonstrated that the phytogeographic regions of the intertidal seaweed community along the Portuguese coast have shifted northward in concert with an observed increase in surface seawater temperature (SST).

If such changes are now being detected when the global climate has warmed by an estimated average of 0.65°C in the last half-century, the effects on species and ecosystems will be obviously more drastic in response to a change in temperature as high as 6°C by 2100 as predicted (IPCC1, 2007).

Fucoid species, particularly the brown seaweed Ascophyllum nodosum (rock-weed), are key habitat formers and energy producers, and their responses to climate change can have significant population, community, and even ecosystem consequences in the Canadian Maritime Provinces. From the economic point of view, these changes could seriously affect a 50-year-old seaweed industry that currently provides hundreds of jobs and injects millions of dollars into the local economy.

The objective of this chapter is to outline the potential changes in the fucoid flora of the Maritime Provinces that could result from the predicted increases in air and SST due to future climate change. The predictions take into consideration the current biological and ecological information of these species in the region.

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