User:Jusssty/sandbox/oaweek2022

Animals
The marine food web in Antarctica is characterized by few trophic components and low prey diversity. The predator-prey dynamics depend on fluctuations in the relative short food chains. A few key species dominate the marine ecosystems. Antarctic krill (Euphasia superba) and ice krill (Euphasia crystallorophias) are examples of key species. They feed on phytoplankton and are the main food for fish and penguins. Shifts in the periodicity of sea ice cycles because of climate change cause mismatches between earlier phytoplankton blooms, krill development, and availability for penguins. The consequences for many penguins are increase in foraging trips and reduced breeding success. Absence of krill leads to increased population fluctuations and diet switches for penguins.

As penguins are highest in the Antarctic food web, they will be severely affected by climate change, but they can respond by acclimation, adaptation, or by range shift. Range shift through dispersal leads to colonization elsewhere, but it leads local extinction. Microevolution is difficult to find for climate change because it is too slow. The most important responses to climate change in Antarctica are poleward shifts, expansion, and range contraction. Ice-obligate penguins are the most affected species, but the near threatened and ice-intolerant gentoo penguin (Pygoscelis papua) has been benefitted. In maritime Antarctica the population of gentoo penguins is rapidly increasing. Due to regional climate changes, they have moved southwards. Now they colonise previously inaccessible territories. Gentoo penguins use mosses as nesting material. This nesting behaviour is new for southern penguin colonies in Antarctica. By dispersal and adaptive nesting behaviour, gentoo penguins have been remarkably successful in population growth. At the borders of the current geographic distributions, the most obvious responses to climate change occur. There the most likely response to climate change is range shift because adaptation and evolution in penguins are too slow.

In birds phenological responses are commonly observed, for example shifts in return to breeding places and timing of egg laying. For penguins shift in penguin phenology in response to prey phenology is important. Often common environmental drivers determine the predator-prey synchrony. Climate driven fluctuations that reduce krill availability also reduce the penguin breeding success. Although gentoo penguins share their prey resource with Adélie penguins (Pygoscelis adeliae) during the breeding season, there is no resource competition between the two species. This implies that current population trends in this region are governed by other factors than competition. The emperor penguin (Aptenodytes forsteri), which has a long breeding season, is constrained in space and time. In the future phenological changes in penguins are likely to be limited by their genotypes. Possible ecological traps might attract ice-intolerant species to ice-free areas without foraging grounds. In the future fitness will decrease if there are no favourable conditions for life cycle events and no adaptive response.