Temperature and the Amount of Sea Ice Present

Between the years of 1880-2012, the Earth’s combined land and sea temperature has seen a rise of approximately 0.85 degrees centigrade (International Panel on Climate Change, 2013), with the later time period displaying an increased rate of warming (Walther et al., 2002). Although organisms are seen to possess a variety of mechanisms in order to maintain function and constrain damage during extreme conditions, these changes in climate regimes have been seen to alter a multitude of species distributions and life histories (Chown et al., 2010).

The habitat of Antarctic krill is exceptionally sensitive to the effects of global warming. Accordingly, slight variations in water temperature will have notable effects on the population dynamics observed within an area (Figure 10). Subsequently, the current and projected future climate change will have a recurrent negative effect on the krill populations (Hill et al., 2013). This consequently will cause a cascade of outcomes on the entire ecosystem due to the krill being a keystone species, at trophic levels above and also those below them, whether the effects are direct or indirect (Moline et al., 2004).

Figure 10:
Figure 10: Showing the fluctuations in surface air temperature over the past 50 years (Antarctica) http://www.discoveringantarctica.org.uk/12_using_data.html

The embryonic development of Euphausia superba has been seen to be affected by temperature, with fluctuations in temperature affecting the efficiency of development, as well as the depth of hatching for embryonic larvae (Hofmann et al., 1992; Ross et al., 1988).

Sea ice extent has a dominant effect in determining the structure of the marine ecosystem, with the annual development and retreat of sea ice of foremost importance to many organisms (Mackintosh, 1972). Oscillations in the extent of ice present are reflected in the overall outcome of sea-surface and air temperatures (Fedoulov et al., 1996). E. superba are particularly associated with sea ice, primarily during feeding regimes, chiefly during larval stages, whereby they feed on the under-ice microbial communities (Quetin & Ross, 2001). The fluctuations seen in levels of see ice affects the level of primary production within the region and consequently alters the level of the krill’s key food source. Not only does the sea-ice harbour food sources for the krill but also, the extent of ice is suggested to have a direct effect on the survival rate of larval and juvenile stages (Daly, 1990).