Environmental Engineering Reference
In-Depth Information
published in recent years that study the genetic structure and diversity in
different species of marine mammals and discuss its fi ndings in relation to
the potential direct or indirect effects of climate change on the conservation
of genetic resources. Finally, we will review recent genetic studies in the
Steller sea lion,
Eumetopias jubatus
, possibly the marine mammal species for
which more genetic data are available, which highlight the importance that
effective population size has on how species respond to climate change.
Direct impacts—reduced sea ice cover and rising sea levels
Ringed seals,
Phoca hispida
, have a circumpolar distribution from
approximately 35°N to the North Pole (King 1983). The species depend upon
snow and sea ice to breed. In recent years, ringed seals face a rapid alteration
of their habitat as Arctic sea ice and snow, for which the species depend to
breed, responds to climate warming. Early snow melts have been associated
with increased mortality from premature exposure to severe weather and
predators (Ferguson et al. 2005). Moreover, ringed seals population level
effects of habitat change will depend upon its population structure. The
potential for local depletions or extinctions is increased if ringed seals are
distributed in many demographically independent subpopulations. Thus,
knowing how the populations are structured is important to understand
the likely impacts of the rapidly changing sea ice cover. Kelly et al. (2009)
investigated the population structure of the ringed
seal in 11 locations along
the northern coast of Alaska, western Canada, the Bay of Bothnia in the
Baltic Sea, and the Lake Saimaa, in Finland. They sampled 354 individuals
that were analyzed with 9 microsatellite loci and a 359 bp segment of the
mitochondrial Cytochrome Oxidase I gene. Their nuclear and mtDNA
data were consistent in suggesting little divergence among sample sites in
the Arctic Ocean. However, they found evidence of genetic differentiation
or isolation between the Arctic Ocean and Baltic Sea seals. The authors
conclude that the rapidly changing snow and ice cover of the Arctic will
inevitably force changes in habitat use and in the patterns of gene fl ow and
that the degree to which genetic diversity will be lost will depend upon
current population structure and the rate of environmental changes.
Another pinniped species that would suffer the direct impact of global
warming is the South American sea lion,
Otaria fl avescens
. The species is
distributed along the Atlantic and Pacifi c coasts of South America (King
1983). In its Atlantic distribution, breeding colonies are located in three
different areas: the coast of Uruguay, north-central Patagonia and southern
Tierra del Fuego (Túnez et al. 2008a). In north-central Patagonia, the segment
of coast with the highest number of sea lions in Argentina, distribution of
colonies is associated with islands availability, and at a local scale, breeding
colonies are positively associated with slight slope coasts (Túnez et al. 2008a).
