158 U.S. NATIONAL MUSEUM BULLETIN 291 



certain limits of oceano^rapliic conditions, no sino;le conservative or 

 nonconservative oceanographic parameter constitutes a limiting factor 

 to distribution. Instead, the combination of physicochemical factors 

 unites with biological factors to control the distribution of 

 Bathyteuthis. 



Tlie biological factors that have been shown to influence the distribu- 

 tion of bathypelagic animals are the rate of organic production, food 

 supply, and the availability of certain dissolved metabolites. Bruun 

 (1957, p. 651) emphasized that it is not depth that determines the sup- 

 ply of food available to deep-sea animals, but that it is the proximity 

 to land and the productivity at the surface. Furthermore, disjunct 

 distributions of many deep-sea forms are related to surface produc- 

 tivity (Bruun, 1956). Food that reaches deep-living animals is a re- 

 flection of the abundance and nature of the plankton at the surface 

 that in turn are regulated by local oceanographic conditions that sup- 

 ply varying amounts of inorganic materials (Moore, 1958, p. 134). 

 Based on his own work on melamphaids and on the work of previous 

 authors, Ebeling (1962, p. 143) suggested that the "segregation of 

 populations into regions of greater or lesser productivity intensifies 

 their genetic isolation." Therefore, areas of greatly disproportionate 

 productivity in the oceans result in faunas that are distinct in compo- 

 sition and abundance. 



Primary productivity and resulting food supply are greatest in areas 

 where nutrients that have accumulated in the depths replenish the eu- 

 photic zone; replenishment is greatest in regions of up welling and 

 vertical mixing and close to runoff from land. Intense upwellings occur 

 along the eastern boundaries of the oceans against the continents; areas 

 of divergence of oceanic water masses also produce upwellings. There- 

 fore, boreal and eastern equatorial waters are highly productive where 

 the shallow, unstable thermocline allows vertical replenishment of 

 nutrients; the central water masses are relatively sterile because the 

 deep, stable, thermocline prevents vertical mixing. A layer of minimum 

 oxygen concentrations due to the oxidation of dead organisms builds 

 up below the surface layer in regions of high productivity. 



The chart of organic production in the world oceans (fig. 60) is 

 reconstructed from Ebeling (1962) based on the report of Fleming 

 and Laevastu (1956) and others. It agrees well with the findings of 

 Nielsen (1954) and Nielsen and Jensen (1957). The most prominent 

 areas of high productivity lie in the boreal regions of the world. The 

 great Southern Ocean forms a broad belt of highly productive water 

 that extends around the Antarctic Continent. The boreal waters of the 

 North Atlantic have a high organic production; the Norwegian Sea 

 is one of the most highly productive areas of the world oceans. Another 



