5, Communities of the Tropical Areas of the Ocean . 

 (A. K. Heinrich) 



The tropical community of the world ocean occupies a tremendous 

 water area, approximately between 40°N and 40°S. Very significant 

 faunistic changes occur at its boundaries--transition to the Arcto-boreal 

 community in the north and the Antarctic community in the south. Many 

 tropical species extend between these parallels throughout all three 

 oceans, and some of them are always among the most abundant species. 

 This creates a structural unity throughout the entire tropical community. 

 However, it is hierarchical in composition and is divided into communities 

 in the individual oceans, which in turn are divided into central, equatorial 

 distant neritic and neritic. Within these, there are other units of 

 lower rank. Transient communities are found between all of them. The 

 central, equatorial, distant neritic and neritic communities differ from 

 each other most strongly. Our task is a description of the structural 

 and functional peculiarities of the first three types of communities; 

 neritic communities will be analyzed only for comparison. 



The biotopes of the central and equatorial communities are the most 

 stable parts of the gyres transferring the primary water masses (central 

 and equatorial), while the biotopes of the distant neritic communities are 

 associated with less stable gyres of the secondary water masses, arising 

 as a result of mixing of the primary water masses (C. W. Beklemishev, 

 1969). The most extensive and unique distant neritic communities are 

 located in the eastern parts of the oceans, where the eastern equatorial 

 communities and communities of the eastern boundary currents (California, 

 Peru, Canary, Benguela) are found, in the locations of upwelling deep 

 waters. The communities of the currents along the western coasts are 

 influenced by the influx of water from the temperate latitudes. The 

 bases of habitats of certain species are maintained by differently 

 directed currents of surface and deeper layers of water (Longhurst, 1967; 

 Heinrich, 1974b). The biotopes of the neritic communities are located 

 in the smaller circulations near the coastlines. The environment here 

 is much less stable than in the oceanic zones, since it falls under the 

 influence of the variable wind regimes of the coastal upwel lings of 

 water and the continental runoff. The boundary, transitional biotopes 

 arise as a result of mixing of waters and have no closed circulation. 

 The position of these communities, according to C. W. Beklemishev (1969), 

 are shown in Fig. 21. The gyres of water maintain the stability of the 

 physical characteristics and allow the species inhabiting them to remain 

 in these regions and pass continually through their life cycles. 



The peculiarities of the biotopes and related populations are 

 created by the climate. The peculiarities of the various water masses 



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