492 EIGHTH PACIFIC SCIENCE CONGRESS 



lies between 26° and 27°. This relative coolness is due to a southward 

 moving current along the west side of the South China Sea and contri- 

 butes to the extension of northern algal species into such favorable 

 southern localities as the Nhatrang sea wall. During the summer this 

 cooling influence from the north is not felt, and the protected nature 

 of the region allows for appreciable advances in temperature, the 

 maxima of 29-30° being reached in late May and again in mid-Septem- 

 ber. Unfortunately, data are totally lacking as to seasonal variations 

 and fluctuations in the marine flora. 



In summary, two generalities are clear: 1. We are still outstandingly 

 deficient in information about the algae not only of the South China 

 Sea but of the whole Indo-Pacific region. 2. Local variations in ecolog)' 

 account for such extreme diversity between the algal associations of ad- 

 joining localities that it is meaningless to suggest affinities for the 

 Nhatrang Bay flora as a whole. 



Among these local variations one may recognize at least four dis- 

 tinctive habitats in each of which the dominant algal components re- 

 present a different pattern of distribution. 



In the upper intertidal zone, above the level of higher low water, 

 and in which the inhabitants are exposed regularly at each ebb tide, an 

 assemblage of species occurs in which the majority are cosmopolitan 

 throughout the temperate as well as the tropical regions of the world. 



In the quiet waters of the sheltered bay shores on either side of 

 the Institut most of the dominant algae are not cosmopolitan, but pan- 

 tropical, having wide, more or less continuous distributions in such 

 commonplace intertidal habitats, but only within tropical or warm seas, 

 particularly in the Indo-Pacific region. 



The dominant algae of the surge-swept rocks mentioned above are 

 similarly pan-tropical, but of a markedly more discontinuous pattern 

 of distribution due to their nanower ecological tolerances and con- 

 sequent restriction to a type of habitat of relatively infrequent occur- 

 rence. 



Finally, the dominant species of the surf-dashed sea wall at Nha- 

 trang represent a group of algae of restricted distribution in which they 

 are the southernmost outposts of a range centering in temperate 

 southern Japan. 



The presence of such a varied flora as has been found at Nhatrang 

 Bay, and of such distinctive habitats with their dissimilar algal inhab- 

 itants, all within an area of scarcely five square miles, demonstrates 

 the complexity of the problems of algal distributions in the vast Indo- 

 Pacific region, the more so when it is realized that this five square miles 

 represents only a solitary spot of knowledge surrounded by tens of 

 thousands of miles of unexplored coasts. 



