a vital substance which it cannot obtain from sea water, it will be forced 

 to consume sufficient food to satisfy the demand for this substance (the 

 Liebig minimum law). If the minimum quantity of food necessary to 

 satisfy the demand for the limiting substance is significantly greater than 

 that quantity of food necessary to satisfy the energy demands of the 

 organism, it will be energetically favorable to the organism to convert 

 the food only to the stage at which the radicals and active centers required 

 by the organism are split off, and then to excrete the remainder in minimally 

 converted form. The ecologic effectiveness of a population in this case 

 will be significantly lower than the calculated effectiveness based on 

 metabolic, growth and generative demands alone, and the excretions can serve 

 as food for other animals, particularly for DOM consumers. 



The view on the benthic biocenosis as a community of independent 

 organisms, equally reacting to the abiotic conditions of the environment, 

 has been significantly modified by the acknowledgment of the tremendous, 

 decisive role of biologic, or more precisely symphsiologic (V. N. Beklemishev, 

 1951) interrelationships in marine communities (reviews: Miloslavskaya, 

 1961, 1964). Minimization of the competitive interrelationships between 

 species is a statistical, climactic aspect of the community; in the dynamic, 

 successional aspect, we see the entire variety of inter- and intra-speci^s 

 interrelationships: when competition between two (or more) species modifies 

 the reaction of these species to abiotic conditions, when the relationships 

 of two (or more) species are modified by the influence of a third, etc. 

 For example, the acorn barnacles Chthamalus stellatus can flourish throughout 

 the entire intertidal area, but cannot withstand the competition of Balanus 

 balanoides . As a result, they form a belt in the uppermost shore 

 horizon, where the B alanuses cannot exist due to the severe environmental 

 conditions. For the Balanuses , as for the Chthamaluses , the habitat 

 conditions are better the lower the level at which they live. However, 

 in the lower intertidal zone the dog-whelks Nucella lapillus , the principal 

 enemy of the acorn barnacles, are numerous. Therefore, balanuses of all 

 ages inhabit the upper level of the intertidal zone, while the lower level 

 is inhabited only by large individuals, too large for Nucella . The exis- 

 tence of these three species is possible due to their varying tolerance to 

 the stress conditions in the upper tidal levels, but their distribution in 

 belts does not reflect the distribution of the optimal conditions for their 

 existence at all (Connell, 1961a, b). The alga Hedophyllum sessile 

 finds its optimal conditions of existence in the surf zone, but is numerous 

 there only in areas with moderate wave action, since in heavy surf it cannot 

 withstand the competition of Laminaria setchelli and Lessoniopsis littoral is . 

 The sea urchins Strongylocentrotus purpuratus devour these algae and may 

 consume them completely, thus liberating the place for Hedophyllum . If an 

 area of the bottom is cleared from the sea urchins, then Laminaria and 

 Lessoniopsis rapidly crowd out Hedophyllum and its associated algae (Dayton, 

 1975) . Studies of this type of interrelationship between species have led 

 to the development of the concept of "key species" in a biocenosis, the 

 ecologic influence of which significantly exceeds their part in the number 

 and biomass of the biocenosis. Usually, the key species is a predator, 

 occupying a high position in the food pyramid of the biocenosis and 

 consuming, selectively or nonselectively, organisms which, were it not for 



