PART VIII — AQUATIC ECOSYSTEMS 



development of life, and the antarctic 

 seas are rich and immensely produc- 

 tive, at least near the surface and at 

 shallow depths. 



Marine Life of Special 

 Interest to Man 



Oxygen and nutrients are high in 

 these cold waters, as might be ex- 

 pected from the abundance of life in 

 them. Two centuries ago man drew 

 heavily on the stocks of seals of the 

 sub-antarctic islands; more recently, 

 he has reduced the stocks of blue 

 whales to such low levels that it is 

 no longer economical to pursue them. 



Recently there have been discus- 

 sions of utilizing the vast populations 

 of the krill, Enphausia superba, which 

 are the principal food of the blue 

 whales, the Adelie penguins, and 

 several kinds of fishes. It is esti- 

 mated that the total populations of 

 krill are equal to all the rest of the 

 fisheries of the world, at least in gross 

 tonnage, or about 60 million metric 

 tons. However, the krill occurs in 

 patches and the small size of the 

 individuals poses difficult processing 

 problems. Also, the animals are 

 "tender" — that is, they must be 

 processed immediately. For these 

 reasons, immediate extensive use of 

 this resource appears unlikely. Among 

 other significantly abundant fishes 

 are representatives of the family 

 Nototheniidae; these are currently 

 being fished on an experimental basis 

 by the Soviet Union. 



There seems to be less fisheries 

 potential in the shallow-water or sea- 

 bottom life, which is often abundant 

 and varied but lacks the extensive 

 beds of large bivalves found in arctic 

 waters. Large seaweeds are abundant 

 around the sub-antarctic islands and 

 near the shores of the Antarctic 

 Peninsula, and invertebrate popula- 

 tions are large in the vicinity of 

 McMurdo Sound and the Soviet base 

 in the Davis Sea. Most of the as- 

 semblage consists of such organisms 

 as sponges, bryozoa, and echino- 



derms, of little potential commercial 

 value. The bottom fauna is of con- 

 siderable theoretical interest because 

 of its apparently stable or slowly 

 changing composition, at the same 

 time combined with a diversity of 

 components comparable to that of 

 the Indo-Pacific coral reef environ- 

 ment. 



The rates of turnover or replace- 

 ment of the antarctic fauna have yet 

 to be worked out in the detail neces- 

 sary for rational harvest of the fish- 

 eries stocks, but the unfortunate his- 

 tory of the blue whale suggests that 

 our relations to the fishery resources 

 of the antarctic will be governed pri- 

 marily by socio-economic rather than 

 ecological considerations. That is, we 

 will simply fish until stocks are so 

 reduced that it becomes unprofitable 

 to expend the effort and funds neces- 

 sary to keep the catch up. 



Examples of Adaptation 



The adaptations and peculiarities 

 of the flora and fauna of the shallow 

 waters near the antarctic continent 

 are of great scientific and theoretical 

 interest. Two of the most interesting 

 concern the adaptation of fishes to 

 water that is below freezing by the 

 production of a sort of natural anti- 

 freeze substance (according to one 

 researcher) or to a higher concentra- 

 tion of salt in the blood (according to 

 another); other fish adapt to the low 

 temperature and high oxygen by de- 

 veloping the ability to function with- 

 out hemoglobin. The disagreement 

 between deVries, who finds that cer- 

 tain fishes may resist freezing because 

 of a protein containing carbohydrate 

 in their blood, as contrasted with 

 Smith's observation that this is ef- 

 fected by increased salt, should stim- 

 ulate more intensive and critical work 

 on the blood of antarctic fishes. 



The adaptations of the Weddell 

 seal, the southernmost mammal, are 

 of particular interest. This animal is 

 capable of diving for periods of more 

 than 40 minutes to depths of 400 



meters (about 1,200 feet), can swim 

 under water for at least two miles, 

 and has excellent sense of direction 

 under water. A thorough understand- 

 ing of the physiology of this mammal 

 will help us to understand the prob- 

 lems of diving, which is an increas- 

 ingly significant activity in man's ex- 

 panding use of the sea. 



Status of Scientific Activity 



At the present time there is con- 

 siderable interest in the nature and 

 significance of diversity in the sea — 

 that is, whether a high ratio of differ- 

 ences to total numbers of all kinds or 

 abundances is related to a situation 

 that may be in equilibrium or indica- 

 tive of a long-established condition, 

 or whether, conversely, a low pro- 

 portion of different kinds of species 

 indicates recent, temporary, or chang- 

 ing conditions. Many pollution pro- 

 grams are predicated on the idea that 

 diversity may be associated with 

 stable and presumably favorable or 

 optimum conditions. As yet we lack 

 adequate data to ascertain whether 

 or not diversity exists and what it 

 may signify, especially for situations 

 at the bottom of the sea. 



The benthic environment of the 

 antarctic should provide us with use- 

 ful information on this controversial 

 problem because it appears to be a 

 comparatively unchanging environ- 

 ment with a rich variety of species. 

 The problem will require a more in- 

 tensified level of field ecological work 

 on a year-round basis than is being 

 done at present, at least by U.S. re- 

 searchers. It is in this area that 

 theoretical formulation and mathe- 

 matical modeling (already being at- 

 tempted for situations in other re- 

 gions) would be most appropriate, 

 but we still lack the data base. For 

 example, we are still unable to evalu- 

 ate data concerning diversity in dif- 

 ferent regions of the antarctic. 



Physiological aspects seem to be 

 much better in hand; a concerted 

 attack on some of these problems is 



232 



