What we call “frozen seas” is usually meant areas of water mostly covered by ice that varies different thickness seasonally. On our planet these are the Arctic Ocean and the Southern Ocean, which together comprise a little under one-fifth of the world’s oceans (John Steele 2010)1. As we know these lands have been at extreme temperature for around 20 million years giving a lot of time for living organisms that live there to adapt for the life, which for most of creatures would be inadaptable.
Antarctica is harsh and extreme environment, considered as the coldest, windiest, and driest places on Earth with temperature that vary from to -2 to 10oCelsius; although; it has very rich wildlife due to the high productivity of the Antarctic Ocean during the summer months; that is, long days supply plenty of light and abundant nutrients brought to all layers by ocean upwelling along the Antarctic Convergence, which fertilize the growth of phytoplankton2.Despite this, cyclonic storms travel eastward around the continent and often they become intense because of the difference between ice and open water temperature. The Arctic Ocean is located in a polar climate and surrounded by continental land mass. The Arctic basin receives about 11% of freshwater from the rivers (mainly the MacKenzie in Canada and the Yenisey, and the Lena in Siberia) and the inflow of saline water comes from Bering Strait, Fram Strait and Canadian Archipelago3.
Figure 1: Food web of frozen seas
Food web in frozen seas isn’t very complicated and is very similar to each other having little differences in some species. However, the Arctic food web is concerned to be relatively young, as it is likely that very little Planktonic fauna was present at the height of the last glaciation. The Antarctic has a mirror image of the Arctic, most likely being in existence for many millions of years and having one of the richest benthic habitats elsewhere (John Steele 2010)1.
Knowing the fact that these places have very harsh environment, we could assume that animals living there need to have some specializations to be able to take advantages of these conditions. We can differentiate these adaptations in three different categories:
• Anatomical – Structure of the body.
• Behavioural – The attitude in which animal acts and moves.
• Physiological – Inner functions of the animal.
There are few commonly found characteristics amongst marine animals, both Arctic and Antarctic. First one is gigantism of benthic organisms; that is, they are larger than their counterparts in other parts of the world. The reason is that the cold waters are high in dissolved oxygen and as an animal increases size its surface area to volume ratio decreases, so there is comparatively less gas exchange to supply the tissues with oxygen. Besides this, benthos metabolic process is slower due to water temperature and there is more opportunity for growing large4. Other characteristic that closely connected to the one before is longevity and the main reason is cold temperature where they live. For them everything could take from three to seven times longer than for similar organisms from warmer waters. That is why they are very vulnerable to some big changes in population. Few more adaptations that are noticed in polar fish are an antifreeze and icefish. The antifreeze are proteins and glycoproteins (protein + sugar) that bind to ice crystals preventing the freezing of cells and they work like safety guards on the ends of sharp stabby ice crystal, preventing growing and the damage it might cause5. Despite this, the icefish are lacking of haemoglobin, which in the result prevent the blood become red, but they do have a lot of blood. The icefish benefits of this fact in the way of saving energy from making red blood cells, which require iron.
Animals Anatomical Adaptations Behavioural Adaptations Physiological Adaptations
(Aptenodytes forsteriaa and Pygoscelis adeliae) Shot stiff tail gives the least contact area to prevent heat loss Due too extreme conditions they are not aggressively territorial. High with myoglobin in muscles to held more oxygen for diving
Black above and white underneath makes them less noticeable in the sea and helps warming on land Tobogganing to save a lot of energy during long journeys. Male can provide milk for chicks while female is fishing
(Pygoscelis adeliae) Under skin lies blubber layer, which allow seals to swim in Antarctic waters Rasping their teeth in the ice, helps them to open breathing holes
The “cost” of diving in terms of extra oxygen consumption is about 1.5 x the sleeping rate2
Fore and hind limbs evolved into flippers for swimming Using high pitched sound can help them to find next hole High haemoglobin concentration allow them to carry 1.6 times more oxygen than human
(Euphausia superba) Bioluminescent organs play a role in mating or schooling the krill at night6 Swarm behaviour to protect themselves from the predators Muscles serve as reserve, to survive cold winter months under ice with almost no photosynthesis process
Figure 2: Examples of specific adaptations of some animals
Summing up, everything was mentioned in the essay, is only small part of life adaptation in frozen seas. Although, such ecosystem could seem simple, in reality it is not. Loosing on part of the chain would cause significant changes because each organism is highly relied on each other. That is why these basins should be explored more and it would open new view on such ruthless, but at the same time virgin environment.