|Ecology of intertidal and sublittoral cryptic epifaunal assemblages: 3. Assemblage structure and the solitary/colonial dichotomy|
Todd, C.D.; Turner, S.J. (1989). Ecology of intertidal and sublittoral cryptic epifaunal assemblages: 3. Assemblage structure and the solitary/colonial dichotomy, in: Ros, J.D. (Ed.) Topics in Marine Biology: Proceedings of the 22nd European Marine Biology Symposium, Barcelona, Spain, August 1987. Scientia Marina (Barcelona), 53(2-3): pp. 397-403
In: Ros, J.D. (Ed.) (1989). Topics in Marine Biology: Proceedings of the 22nd European Marine Biology Symposium, Barcelona, Spain, August 1987. Scientia Marina (Barcelona), 53(2-3). Instituto de Ciencias del Mar: Barcelona. 145-754 pp., meer
In: Scientia Marina (Barcelona). Consejo Superior de Investigaciones Científicas. Institut de Ciènces del Mar: Barcelona. ISSN 0214-8358; e-ISSN 1886-8134, meer
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Under-boulder cryptic epifaunal micro-habitats in both the intertidal and sublittoral were modelled by means of 15 x 15 x 1 cm slate panels bolted together horizontally, but separated by perspex spacers of either 25, 10 or 5 mm height. The under-surface of the top panel in each unit pair is held to represent a boulder undersurface and it is only these sessile assemblages which are considered. In order to assess the importance of timing of space availability on assemblage development, triplicate sub-sets of panels of all three gap-sizes were immersed in both habitats in February, June, August and October 1983. These were followed until January/February 1986. Rates of larval settlement, organism growth and area occupied were consistently greater in the sublittoral, and showed more-or-less predictable patterns with gap size (25>10>5mm). High-profile solitary organisms were not, as a rule, excluded from the narrower gap-sizes. Overall, for both habitats, colonial organisms dominated most panel sets, although solitary ascidlans were occasionally important. The axiom of the solitary strategy dominating intertidal hard-substratum assemblages does not, therefore, extend to cryptic habitats. Observations of comparable panel-sets initiated in similar months in succeeding years and compared at 12 months' age showed marked differences in assemblage structure: within- and between-year stochasticity of larval settlement and establishment are clearly important in determining at least the initial stages of "succession". Oualitative and quantitative comparisons clearly showed the intertidal and sublittoral assemblages to be structurally quite different. Low-shore under-boulder cryptic epifaunal assemblages should not, therefore, be viewed as merely the uppermost fringes of otherwise sublittoral components.