Effects of global warming on marine mammals
The global warming is having severe effects on all wildlife, including the
human population. These effects, however, are quite complex. Most
consequences involve the interrelation between species (foodweb) but also
direct effect are noticed.
The consequences on marine mammals can be resumed as followed:
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Effects of changes in temperature:
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Most toothed whales are limited in the range of water temperature that
they inhabit. E.g. species of the cold polar regions (like the beluga)
are restricted to cold waters and cannot survive in warm water.
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For other species there will be a shift in geographic ranges (although
several species are physically limited to change their ranges e.g.
river dolphins).
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Effects of changes in temperature on prey species (e.g. fish,
cephalopods, etc.) have indirect effect on marine mammals like:
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A rising sea level has effects on marine mammals that depend on the land
for their reproduction (like e.g. sea lions, seals, ice bears, etc.).
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A change in the ocean currents has effects on
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the oceanic fronts and consequently on the distribution of marine
mammals associated with these fronts.
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the sustainability, productivity and biodiversity of the whole marine
ecosystem, affecting distribution,
abundance and migration of plankton, fish, cephalopods, etc. which in
turn affect marine mammals.
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Change in sea-ice cover has a direct effect
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on the animals depending on the sea-ice for breeding like e.g. seals,
ice bears, etc. (habitat loss).
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biomass, distribution, migration, nutrition, reproduction and
abundance of species associated with the sea-ice like phytoplankton,
zooplankton, fish,
crustaceans and consequently marine mammals (e.g. baleen whales will
need to travel greater distances due to the retreat of sea-ice and
consequently a change in distribution of their prey).
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Change in water salinity will alter the distribution and abundance of
prey due to their limited salinity tolerance.
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Increase of El Niño events will have a severe impact on all marine life.
(Source:
Learmonth, J.A., Macleod, C.D., Santos, M.B., Pierce, G.J., Crick, H.Q.P.,
Robinson, R.A., 2006. Potential effects of climate change on marine
mammals. Oceanography and Marine Biology: An Annual Review, 44,
431-464)
The most rapid climate change is to be seen in the polar regions. There
is growing evidence that the maximum extend of winter sea ice is declining
and several areas of the polar regions are warming at a rate of 2 to 3
times the global average, causing parts to break and melt down, with
severe consequences (in the past 50 years, an increase of 2,5°C was
measured on the Antarctic Peninsula).
The polar regions contain unique ecosystems. Moreover, the relationship
between ice and seawater is the main factor driving the ocean’s currents
which pump oxygen and nutrient-rich waters thousands of kilometers into
both hemispheres, fertilizing the surface waters.
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