Environmental Engineering Reference
In-Depth Information
In the last 5 years, three genetic studies analyzed the genetic structure and
historical population dynamics of the species in the Atlantic coast. Túnez
et al. (2007) and Feijoo et al. (2011), analyzing respectively cytochrome b
and D-loop sequences, found that Uruguayan and Patagonian colonies are
genetically different and should be considered as different conservation
units. However, this population structure was not found when microsatellite
markers were used (Feijoo et al. 2011). The authors interpret this result as a
consequence of female phylopatry and high male dispersion. Three years
later of the fi rst work, Túnez et al. (2010), using mitochondrial D-loop
sequences, found that the historical population dynamics of
O. fl avescens
in north-central Patagonia appears to be closely related with the dynamics
of the Late Pleistocene glaciations. The genetic analyses suggested that sea
lions population in Patagonia suffered a demographic contraction during
the glacial period, followed by a population expansion when the glaciers
retracted. Northern Patagonian colonies, as Punta Norte or Puerto Pirámide,
which did not show clear evidence of any expansion at that moment, could
have acted as refugia during glaciations, and individuals coming from these
colonies would have recolonized southern colonies during the posterior
interglacial period. As was stated, predicted impacts of climate change
on the marine environment include a rise in sea levels (Learmonth et al.
2006). In this context, it is possible that future rises in sea levels would act
as glaciations in the past, making some regions of the coasts of southern
Argentina and Tierra del Fuego uninhabitable by coastal breeding animals.
Beaches with slight slope coasts and islands currently occupied by sea lion
colonies genetically distinct from other colonies would be covered by the
sea or drastically altered by changing sea levels, resulting in the loss of an
important genetic resource and increasing the degree of isolation between
remaining colonies. Another example of possible consequences of rising sea
levels is provided by the Mediterranean monk seal,
Monachus monachus
,
a critically endangered species of which only two genetically different
populations remain (Pastor et al. 2007). In this case, rising sea levels could
also eliminate already scarce haul-out sites of the species, especially by the
fl ooding of caves that provide the only refuges for some groups (Harwood
2001).
Indirect impacts—changes in prey availability
Recent climate change has triggered profound reorganization in northern
latitude ecosystems, with substantial impact on the distribution of marine
assemblages from plankton to fi shes (Richardson and Schoeman 2004, Perry
et al. 2005). These shifts in marine habitat and community structure are
expected to drive major changes in the distribution, density and dispersal
of predators such as marine mammals (Learmonth et al. 2006, Marx and
