Marine Mammals in a Changing World

Abstract

Planet Earth is a most unusual one among the known planets since 71% of its surface is covered by oceans full of life. Life originated and diversified in the oceans along millions of years. At present, the oceans are largely responsible for sustaining planet life and in regulating the climate. Climate change is thoroughly accepted as a global concern (IPCC, 2007). Rising atmospheric gas concentrations had increased global average temperatures by approximately 0,2 centigrade per decade over the past 30 years (Hansen et al, 2006) with most of this added energy bein absorbed by the world's oceans (Hoegh-Gouldberg and Bruno 2010). And in addition, to acting as the planet's heat sink, the ocean had absorbed aprox one-third of the carbon dioxide produced by human activities. Increases in the heat content of the ocean have driven other changes. Thermal expansion of the oceans as well as increased meltwater and discharged ice from terrestrial glaciers and ice sheets has increased ocean volume and hence sea level (Rahmstorf et al, 2007). The earth`s climate is changing, the planet is warming, sea ice and glaciers are in retreat, sea level is rising, and pollutants are accumulating in the environment and within organisms (Moore, 2008). The severity of damaging human-induced climate change that takes place due to increase in carbon dioxide concentration is largely irreversible (Solomon et al, 2009) All these changes affect marine ecosystem and the different marine species suffer the consequences. All those species that depend on the ice, such polar bear (Ursus maritimus) and the ringed seal (Phoca hispida) are good examples of these changes and they are very sensitive at population level to climate change. The use of marine mammals as ecosystem sentinels is a function of their ecological diversity and the variability that present the marine ecosystem (Moore 2008). This Chapter will approach the challenge for Marine Mammals in a changing world. The objective is walk the natural history of marine mammals and how they were affected by climate change-related reasons, considering anthropogenic causes.