SCALES OF SUBSTRATUM HETEROGENEITY, STRUCTURAL COMPLEXITY, AND THE EARLY ESTABLISHMENT OF A MARINE EPIBENTHIC COMMUNITY

This study examines experimentally, in situ, the influence of four sca les of heterogeneity (0, 1, 10, 100 mm) and the hierarchical combinati on of those scales of heterogeneity (0 + 1 + 10, 0 + 1 + 100, 0 c 10 100, 0 + 1 + 10 + 100 mm) on the early establishment of a sessile mar ine littoral epibenthic community. The study was carried out in St. An drews, New Brunswick (Canada) from July to October 1989. Flat panels w ithout and with crevices of various depths (1, 10, 100 mm) alternating with adjoining flat areas were moored according to a random design in the surface 2 m in the sublittoral zone. Species diversity and total percent cover increased from August to October. However, the ANOVA sho wed no significant effect of substratum heterogeneity nor complexity ( the hierarchical combination of various scales of heterogeneity) on ov erall diversity (H') in August and October nor on percent cover on the whole panels in August. However, one type of complex panel out of eig ht types tested did show a significantly lower percent cover than the others in October. Small scale patterns of distributions varied signif icantly among the different types of surfaces within each panel, howev er. In general, percent cover of organisms were greater in 1 mm crevic es in August and in 10 mm crevices 2 months later, than on other types of surfaces. Local hydrodynamics and active larval choice may be invo lved. Our study shows that both substratum heterogeneity and complexit y did not influence much the overall northern sessile community charac teristics (diversity and abundance), but structured strongly the small scale distribution of its species during the early phases of developm ent.