596 



THE COMMUNITY 



geographic examination of the sea.* The 

 unified concept of the community devel- 

 oped in this work treats the oceans essen- 

 tially as a single major community, and the 

 whole of marine ecological associations 

 constitutes essentially not only a single 

 major community and a single biome, but a 

 single biome-type. 



The marine associations designated by 

 Clements and Shelford (1939) as "biomes" 

 are nearer the bottom of the scale of biotic 

 ecological subdivisions, and cannot be ac- 

 cepted as major formations in any sense, 

 much less in the light of the definition of 

 the major community set forth in the pres- 

 ent work. 



Two groups of marine associations, so 

 far as hierarchial arrangement into cate- 

 gories is concerned, have some similarity 

 to the biome types of the terrestrial world. 

 These are the benthos and the pelagial, i.e., 

 the bottom dwellers together with the bot- 

 tom-bound fife ecologically directly asso- 

 ciated with the bottom, and the free-float- 

 ing and free-swimming plants and animals 

 of the open sea, which appear to be rela- 

 tively independent of the shores and bot- 

 tom. The open seas of the pelagial are 

 broadly connected, and temperature zones 

 are somewhat less marked than in the ben- 

 thos. The greatest differences of type 

 within the benthos are those of eroding 

 shores and depositing shores; these difi^er- 

 ences are mechanical and thus are physio- 

 graphically and physically, superimposed on 

 broad climatic zonation. 



The temperature-limited and thus espe- 

 cially biome-like coral reef (with its various 

 components) resembles the eroding shore 

 type on its outer face, exposed to wave- 

 shock, but is composed also of reef-condi- 

 tioned depositing lagoons, in which the 



* We are concerned in this chapter with the 

 broad outlines of the whole marine biome-type. 

 Special phases of this subject have been dis- 

 cussed previously. For example, oceanic and 

 littoral water masses (p. 151); marine habitats 

 and inhabitants with respect to vertical stratifi- 

 cation (pp. 447-451) and to the horizontal 

 zonation (pp. 453-460); marine sediments 

 (pp. 460, 461); food web (pp. 501-503) and 

 periodicities (pp. 542-544 and 554, 555). The 

 interested student will find extensive correlative 

 material in Murray and Hjort (1912), Ekman 

 (1935), Hesse, Allee, and Schmidt (1937), 

 Sverdrup, Johnson, and Fleming (1942), and 

 Coker (1947). 



massive corals of the reef face may be del- 

 icately arborescent and interspersed with 

 animals adjusted to quiet water (hke the 

 sponges and soft corals) or to the coral 

 sand bottom, like the sea cucumbers (p. 

 570). The separation of the major coral 

 reef regions into an Indo-Pacific and an 

 Atlantic subregion forms a still more strik- 

 ing analogue of a biome type with at least 

 two biomes. 



We must refer also to the remarkable 

 long-term successional phenomenon repre- 

 sented by coral reef islands. Darwin was 

 the first to explain the ringhke coral atolls 

 of the Pacific as related to the subsidence of 

 volcanoes, successively with a fringing 

 reef, a barrier reef and lagoon, and, with 

 the disappearance of the central volcanic 

 remnant, an atoll. The outer Society islands, 

 indeed, exhibit the last stages of the island 

 and barrier reef, in which the central is- 

 land is about to disappear (Darwin, 1842). 

 Because Darwin's theory does not explain 

 the contrary phenomenon of emergent 

 shores, and is oversimplified in other re- 

 spects, it has given rise to a voluminous 

 literature, much of which in its critique of 

 Darwin has "thrown out the baby with the 

 bath" by rejecting the essentially and even 

 obviously correct central core of his theory. 

 A summary of this extremely interesting 

 literature is presented by Davis (1928a). 



The slowness of the physiographic suc- 

 cession from eroding to depositing shore 

 marks the corresponding succession of the 

 forms of life, through the vast evolution- 

 ary periods of time that have been avail- 

 able to the life of the sea; it is thus evolu- 

 tionary rather than successional. Even on 

 rock coast, however, the life of depositing 

 shores interdigitates minutely in tide pools 

 and sheltered crevices, however small, with 

 that of the wave-pounded rock. 



The lightless deep sea includes a most 

 remarkable fauna, but this is dependent 

 either primarily or secondarily upon the 

 benthos and pelagial, and this dependence 

 further illustrates the difiiculty of recogni- 

 tion of true self-sustaining communities 

 within the sea, however much their world 

 distribution may resemble that of the ter- 

 restrial biomes. The parallels between the 

 unified deep-sea regions and the frag- 

 mented cave-community type of the land 

 are noteworthy. 



The development of major faunal regions 



