MARINE DIATOMS OF THE PHILIPPINE ISLANDS 



By Albert Mann 



Custodian, Section of Diatoms, United States National Museum 



INTRODUCTION 



The diatom flora of the Philippine Islands is easily recognizable as 

 a subtropical one. Its forms as a class are large, elaborately orna- 

 mented, and therefore very beautiful, and there is no preponderance 

 of the so-called naviculoid forms, elongated diatoms of rather plain 

 design, which are in such large majority in colder waters. This 

 robust and ornate development is due mainly to temperature, the 

 effect of which on the size and ornamentation of the diatoms has 

 been studied by Schumann (Diat. Hoh. Tetra, p. 38), Heribaud 

 (Journ. Roy. Micros. Soc 1894, p. 491), and others. But abundant 

 nourishment, including organic products in solution, and ample light 

 are also contributory factors in the richness of the diatom flora of 

 these islands. 



The locality is also a prolific one, both in the sense of the abundant 

 number of individuals and in that of the great diversity of genera and 

 species inhabiting these waters. It is generally found that colder 

 seas, like the north and south polar regions, while producing rather 

 plain diatoms, are richest in diatom life, as measured by the number 

 of individuals in a given cubic area of water or of bottom material. 

 But even in this particular I have yet to find any specimens of "marine 

 ooze" to equal some collected at Jolo Jolo. In the high percent- 

 age of diatoms it contained it reminded me, though it actually 

 surpassed, some material collected by the Shackleton South Polar 

 Expedition at McMurdo Sound. In a paper on Organic Fertility of 

 the North Pacific Ocean (Scripps Institute publications), E. L. 

 Michael says that diatom ooze is very abundant in south polar regions, 

 with isolated patches near the Aleutian and the Galapagos Islands, 

 and he adds: "It is also reported from the Philippine region, an 

 anomalous fact, since diatoms are most abundant in cold latitudes." 



The abundance expressed in number of genera and species above 

 noted is, on the other hand, truly subtropical. Just as a prolific pro- 

 duction of individuals is generally associated with cold water's, so a 



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