PART I. THE ECOLOGY OF MARINE COMMUNITIES 



CHAPTER I. SOME PRINCIPLES OF THE STRUCTURE AND DEVELOPMENT 



OF MARINE COMMUNITIES 



1 . General Ecologic Concepts as Applied to Marine Communities. 

 The Community as a Continuum . (K. N. Nesis) 



The concept of the "biocenosis" was introduced by Mobius (1877). 

 Mdbius defined a biocenosis as a community of organisms inhabiting an 

 individual area of the environment; the composition and quantitative 

 relationships of the species of a community correspond to the mean of 

 the extremes of the environmental conditions. The members of the biocenosis, 

 according to Mobius, directly or indirectly depend on each other and 

 mutually serve each other so that a self-regulating biologic equilibrium 

 is formed, fluctuating about its mean position (Hesse, 1924). This 

 definition emphasizes first of all the biologic interconnection and inter- 

 dependence of the organisms of the community. This concept, introduced by 

 Mdbius, is firmly rooted in ecology. 



The most important stage in the development of marine ecology was the 

 introduction of a quantitative method of investigation of the benthos and 

 bottom communities, connected with the name of Petersen (1911-1918). 

 Petersen, however, had a quite different understanding of the word community 

 than did Mobius. Communities, according to Petersen, were statistical units, 

 regularly repeated groups of species encountered together, recognized (and 

 named) after the most numerous and characteristic species which "struck the 

 eye." The studies of Petersen were quite fruitful and stimulated extensive 

 development of research in the area of quantitative accounting for the 

 benthos (Zenkevich, 1947, 1963). The term "Petersen communities" has been 

 firmly implanted in the ecologic literature. 



However, at the same time, a Mdbius concept of the community as a group 

 of ecologically related organisms continued to exist and develop. The view 

 of the community as a structure with such close and numerous internal 

 connections that it could be likened to human society or even a super- 

 organism developed. "Animal communities . . . are not mere assemblages of 

 species living together, but form closely knit communities or societies 

 comparable to our own," wrote one of the founders of modern ecology, C. 

 Elton (1927, p. 5). Naturally, for the proponents of this view, the 

 Petersen concept of the community was unacceptable. As a result of the 

 extended discussions of the 1920s and 1930s, two concepts were developed in 

 ecology, particularly in hydrobiology : communities of animals are 

 statistical units, and communities are biologic units (Thorson, 1957). The 



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