450 



THE COMMUNITY 



ford and Gail (1922) measured light inten- 

 sity with a Kunz photo-electric cell and 

 found that the depths at which brown and 

 red algae were most abundant per square 

 meter of bottom to be at 10 to 15 meters 

 depth. The gradient in hght is given in 

 Table 32. 



This difference of 5 meters represents 

 a considerable reduction in Hght intensity 

 and is in general agreement with the ex- 

 perimental data of Klugh and Martin 

 (1927) and with the examination of the 

 Carnegie data by Graham (1941). 



This uppermost stratimi is in many re- 

 spects broadly analogous to the epilimnion 

 of second order lakes. Both are relatively 

 well illuminated, relatively high in dis- 

 solved oxygen, and relatively low in car- 

 bon dioxide; both contain the bulk of the 

 plankton with its numerous sidechains of 

 nektonic herbivores and carnivores; both 

 require large amounts of nitrates and phos- 

 phates for plant protein synthesis; in both, 

 these nutrients have a seasonal variation 

 (discussed in the following chapter). The 

 analogy is best appHed in open ocean, 

 where in summer a discontinuity layer 

 develops at between 10 and 20 meters. 

 Some parts of tropical seas are continuously 

 thermally stratified. 



For pelagic stratification, the best known 

 area, the North Atlantic, has been rela- 

 tively well studied. In this oceanic area 

 definite vertical stratification of animals has 

 been established to 5000 meters. In the 

 cold waters of the North Atlantic, between 

 60 and 80 degrees north (from the Wy- 

 ville Thompson Ridge to Franz Joseph 

 Land), the upper 200 meter zone has a 

 characteristic fauna associated with a rich 

 phytoplankton. The stratum includes 

 whales, herring, mackerel, scyphozoans, 

 arrow worms, and copepods, especially 

 Calanus finmarchicus (Bigelow, 1925; Mur- 

 ray and Hjort, 1912; Sverdrup, Johnson, 

 and Fleming, 1942). 



South of the Wyville Thompson Ridge, 

 at least from 60 to 10 degrees north, there 

 appear to be three defined strata. From the 

 surface to 150 meters (Murray and Hjort, 

 1912, pp. 669-670; Gran, 1912; Clements 

 and Shelford, 1939, p. 319), there is a 

 rich zooplankton of Foraminifera, Radio- 

 laria, Copepoda, pteropod moUusks, scy- 

 phozoans, tunicates, and Portuguese man- 

 of-war. The nekton is especially character- 



ized by scopefid fishes, there being at least 

 seven species of Myctophu7n and seven 

 genera of cephalopod moUusks. 



From 150 to 500 meters (Murray and 

 Hjort, 1912; Beebe, 1929, 1932, 1932a; 

 Clements and Shelford, 1939, pp. 318- 

 319), the zooplankton is composed chiefly 

 of copepods, amphipods, ostracods, arrow 

 worms, pteropods, and small medusae. The 

 nekton is made up largely of small fishes 

 that are typically laterally compressed, with 

 a silvery skin, large eyes, and usually with 

 numerous luminescent organs. Of these 

 fishes, the telescope-eyed fish (Argyropele- 

 cus) is representative of the stratum. 



From 500 to 5000 meters (Murray and 

 Hjort, 1912; Chace, 1940) is a deep stra- 

 tum, probably substratified. This includes 

 the lower portion of the photic zone as 

 well as a large section of the aphotic zone. 

 Within its range is a relatively sparse fauna 

 characterized by bathypelagic fishes, such 

 as the slender, dark-colored Cyclothone, 

 and bathypelagic crustaceans, such as the 

 typical Acanthephyra. 



Chace has thoroughly investigated these 

 crustaceans off Bermuda, between 800 and 

 2000 meters. The caridean decapods stud- 

 ied belonged to species recorded from the 

 bathypelagic stratum of many other areas. 

 Wide distributions in this zone demonstrate 

 that the marine faunistic regions are not 

 developed in it, and Table 33 illustrates 



Table 33. Number of Species of Bermudan 



Caridea Reported from Other Areas 



(From Chace, 1940) 



Mediterranean Sea 2 



South Atlantic 2 



South Pacific 4 



Sargasso Sea 4 



Off coasts of Ireland 5 



Hawaiian Islands 5 



Eastern Pacific (California to Peru) 6 



Off Cape of Good Hope 6 



North Atlantic (north and west of the Gulf 



Stream) 6 



Bahamas and the West Indies 9 



Malay Archipelago and Philippines to Japan 9 



Equatorial Atlantic 11 



Eastern North Atlantic (Bay of Biscay to 



Cape Verde Islands) II 



Indian Ocean 15 



the cosmopoUtan geographic range of these 

 bathypelagic prawns. 



Even allowing for insufficient knowledge 

 and for unequal effort in these fourteen 

 areas, the presence of so many species of 



