CORAL STUDY EST THE SOUTHERN OCEAN — SQUIRES 449 



to grow and secrete calcium carbonate in vast quantities because of the 

 unique relationship between symbiotic dinoflagellates called zooxan- 

 thellae and the coral animal which enhances the physiology of the 

 coral in its calcium-carbonate depositions. It is this same symbiotic 

 relationship which restricts the reef corals to warm waters and to 

 those waters which are lighted, for the symbionts require light for 

 their photosynthetic activity. Corals of the cold waters have not yet 

 been demonstrated to have such symbionts, and we should not expect 

 them in the waters of the deep ocean far beyond the penetration of 

 light. 



The ahermatypic corals show much greater latitude in their choice of 

 life sites. They are found to occur through wider ranges of depths, 

 through greater ranges of temperature, and through a greater 

 diversity of conditions than their more specialized hermatypic rela- 

 tions. This does not affect their value in studies of the relationships be- 

 tween animal and environment, however, for they have developed other 

 habitat restrictions which are of considerable interest to the ecologist. 



The very simplicity of the solitary corals is a distinct advantage in 

 studying the relationships between animal and environment, for 

 the responses of the animal are not clouded in the multiplicity of 

 asexually produced individuals which constitute the colonial coral 

 of the tropical reefs. The hermatypic corals are able to cope with 

 many external factors through successive minute adjustments in each 

 of the asexually produced members, which accumulate through their 

 generations major compensations in the form of the colony. The 

 solitary coral, on the other hand, records in its skeleton the entire 

 history of its personal response to the exigencies of life. 



The Southern Ocean, lying as a moat about the Antarctic Continent, 

 is actually composed of the southern segments of the other three great 

 oceans and as a result must be defined by arbitrary borders. Its 

 unity and identity lie principally in the cohesive nature of the 

 hydrology of the Southern Ocean, because through most of its extent — 

 the Southern Ocean is unbroken by land and is overlain by a potent 

 driving force of the Westerly Winds — it is powered by a basically 

 simple current system widely characterized as the West Wind Drift 

 composed of the "Roaring Forties," the "Furious Fifties" and the 

 "Screaming Sixties." The wind-driven system carries water about 

 the poles in a continuous broad band interrupted only by the relatively 

 insignificant Subantarctic Islands, by the projection into its northern 

 margin of the South Island of New Zealand, and severely constricted 

 only by the remnants of the Andean chain extending from Tierra del 

 Fuego across to Antarctica through the grand curvature of the 

 Scotia Arc. The water movement in these areas is actually not 

 directed solely around the Antarctic continent, but carries with it a 

 strong northern component so that Antarctic water is continually 



