coastal land areas that would be flooded as result of sea level 

 rise. One the other hand, the acceleration of biodegradation 

 processes in the higher latitudes would preclude any marked 

 increases in biosedimentary fluxes. 



In addition to rising temperature, another factor that would 

 affect the formation of new organic matter in the ocean would 

 be the further intensification of ocean pollution due to human 

 activities. According to present estimates, pollutant levels in 

 the euphotic layer of the ocean by the middle of the next century 

 can be expected to rise from 25% to 30% above current values 

 (Izrael & Tsyban, 1989). Moreover, warming of water masses 

 coupled with the acceleration of chemical reaction could increase 

 the toxicity of pollutants for marine biota. This would necessarily 

 have an adverse effect on the productivity of polar oceanic 

 ecosystems (Patin, 1979; Tsyban et al.. 1985). 



It should be noted in conclusion that primary production 

 values for a region do not constitute an adequate yardstick for 

 assessing commercial fish resources. What is more important, 

 as far as the fishing industry is concerned, would be the shifting 

 of the most productive zones of the World Ocean, and especially 

 of upwelling areas, as this would be fraught with serious 

 repercussions in terms of the distribution of commercial fish 

 stocks and fish resources replenishment. 



The Role of Ice in Sustaining Marine Polar Ecosystems 



Ice plays an important role in the development and 

 sustenance of marine polar ecosystems for the following reasons: 

 /. it is extremely important to the growth of the marine algae 

 that are the primary food source in marine ecosystems; 2. it 

 creates conditions conducive to primary-production synthesis 

 at the ice-water interface, allowing plants to bloom, thus 

 maintaining the abundance and species diversity of biological 

 communities; i. it is extremely important to the vital activity of 

 the organisms that ensure energy transfer from the primary- 

 production level ( algae and phytoplankton ) up to higher trophic 

 levels (fishes, marine birds and mammals); and 4. the latter 

 factor in turn operates to maintain existent numbers of marine 

 communities. 



One of the possible consequences of global warming 

 might be the shrinkage and diminished stability of marine ice, 

 which would directly affect the productivity of polar ecosystems. 

 For example, the absence of ice over the continental shelf of the 

 Arctic Ocean would produce a sharp rise in the productivity of 

 this region, provided sufficient biogenic elements are available. 



Polar mammals need ice to obtain their food and to 

 reproduce. For example, the extent of the polar bear's habitat 

 is determined by the maximum seasonal surface area of marine, 

 ice in a given year. This means that the disappearance of ice 

 would threaten the very survival of the polar bear and of certain 

 marine seals. Similarly, a reduction of ice cover would reduce 

 food supplies for penguins and walruses and increase their 

 vulnerability to natural predators and human hunters and 

 poachers. Should the ice cover shrink, animals such as the sea 

 otter would have to migrate to new territories. Furthermore, it 

 remains unclear how the contraction of ice cover would affect 

 the migration routes of animal (such as whales) that follow the 

 ice front. 



Changes in water temperature and wind patterns as a result 

 of global warming would almost certainly affect the distribution 

 and size of the polynyas (unfrozen patches of water surrounded 

 by ice ), which are so vital to the maintenance of polar ecosystems. 

 In addition, changes in the extent and persistence of marine ice, 

 combined with changes in the characteristics of currents such 

 as the circumpolar current in the southern latitudes, could 

 influence the distribution, biomass, and volume of available 

 krill. Krill is an important link in the food chain of Antarctic 

 Ocean fauna and is also of great importance for commercial 

 fisheries. A proper understanding of the way in which the 

 productivity of the Antarctic Ocean would change under new 

 climatic conditions is essential in assessing the consequences 

 of global warming for the World Ocean environment. 



Effects on Fish Stocks oi 



Climate change is one of the paramount factors that 

 determine the fish reserves of the World Ocean, even though 

 the sensitivity to this factor of particular stocks varies 

 considerably from population to population and from region to 

 region. 



Each population of a given species community is fitted to 

 a particular hydrody namic structure with definite temporal and 

 spatial characteristics. Given this fact, changes in ocean 

 circulation could lead to the disappearance of certain populations 

 or to the appearance of new ones. Most seriously affected 

 would be the populations localized in habitat boundary waters 

 (Troadec. 1989). 



One of the promising avenues for predicting the possible 

 consequences of climate warming on the status offish fauna is 

 the method of historical analogies. This method involves 

 isolating salient features in the distribution and biomass offish 

 stocks over a number of past intervals such that each interval is 

 associated with specific climatic, and therefore environmental, 

 characteristics, the purpose being to draw further analogies. 

 The application of this method for describing the state of fish 

 resources over the present century has made it possible to 

 discern certain essential features. The warming that occurred 

 in the first half of the 20th century was accompanied by the 

 penetration of northern fish species into subarctic and arctic 

 seas, something that was observed both in the North Pacific and 

 the North Atlantic. Thus, a favorable change in environmental 

 conditions as a result of warming can generate new commercial 

 fish stocks. Moreover, the warming of the 1940"s and 1950"s 

 showed that warming of the marine environment can have 

 quite different consequences even for a single fish species, 

 depending on specific features of habitat. For example, this 

 period saw the most sizeable generations of 

 Atlantic-Scandinavian herring, while the number of North Sea 

 herring plummeted. 



Recent studies in the North Atlantic have brought to light 

 a direct link between climatic variation on the one hand and the 

 distribution and replenishment of fish resources on the other. 

 Particularly noteworthy in this connection is the so-called 

 "1970's anomaly" (Jenkins & Ephraums, 1990), remarkable 

 for the concurrent effects it involved for several commercial 

 stocks. Originating off the coast of eastern Greenland in the 



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