COMMUNITY STRUCTURE OF TRANSITIVE ZONES UNDER THE CONDITION OF COMPLEX ENVIRONMENTAL GRADIENTS (AN EXAMPLE OF MACROBENTHOS OF THE CHERNAYA ESTUARY, THE KANDALAKSHA BAY, THE WHITE SEA)

Two complex environmental gradients of different scale and direction a ffect the spatial structure of estuarine macrobenthos: the longitudina l (hydrodynamics, salinity etc.) and the transversal one (tidal level) . Each environmental gradient forms a gradient of the biotic structure , along which relatively homogeneous areas ale separated by tranzitive zones (ecotones), characterized by the ''edge effect'' - increased sp ecies diversity and abrupt changes of total abundance, size and specie s structure. Changes of macrobenthic structure related to one of the g radients are most expressed in ecotones along the other one, Sites of intersection sf longitudinal and transversal ecotones (''double-transi tion points'') are focuses of shifting of may abiotic factors and have peculiar fauna with dominance of most tolerant species, unstable stru cture and sharply varying productivity. The superposition of several e nvironmental gradients in different spatial scales results in complex multidimensional community patterns.