Vertical Zonation and the Rocky Shore
Student Number: 500890847
Candidate Number: 14822
Vertical Zonation and the Rocky Shore
According to Yonge (1949), “the zoning of both plants and animals within the narrow vertical limits of a rocky shore is one of the most striking features about shore life.” It is noticeable particularly where sessile organisms (such as barnacles) occur in abundance on the boundaries of their vertical distribution, as they form a conspicuous line (Boaden & Seed, 1985). The author has also been particularly impressed by clear zonation patterns of brown algae often to be found on rocky shores. Precise and universal demarcation of these zones is impossible (Brehaut, 1982), but a comprehension of the vertical zonation of rocky shores is clearly essential to an understanding of their ecology.
The first attempts to differentiate zones were based on tidal classification (Boaden & Seed, 1985). It is easy to distinguish (Brehaut, 1982) a sub-littoral zone (one which is never completely uncovered by water), a supra-littoral zone (never completely covered), and a littoral zone (where periodic covering and uncovering by water is normal). These are little more than terms of convenience however, as the extreme high and low levels of tide may only be reached at intervals a considerable number of years apart. Since many organisms that dwell on rocky shores are annuals, this is of no significance to them.
Although zonation is related to tides, it is influenced by other factors (discussed below). Indeed, Stephenson and Stephenson (1972) note, “Zonation, although undoubtedly related to tides, is not directly caused by them.” Lewis (1964) emphasises that restricting zones to tidal boundaries causes confusing terminology. The littoral zone should not be defined in relation to sea level, but rather as a strip of the shore which undergoes alternating periods of exposure to air and submersion under seawater, and where characteristic communities of organisms thrive.
Stephenson and
Candidate Number: 14822
Vertical Zonation and the Rocky Shore
According to Yonge (1949), “the zoning of both plants and animals within the narrow vertical limits of a rocky shore is one of the most striking features about shore life.” It is noticeable particularly where sessile organisms (such as barnacles) occur in abundance on the boundaries of their vertical distribution, as they form a conspicuous line (Boaden & Seed, 1985). The author has also been particularly impressed by clear zonation patterns of brown algae often to be found on rocky shores. Precise and universal demarcation of these zones is impossible (Brehaut, 1982), but a comprehension of the vertical zonation of rocky shores is clearly essential to an understanding of their ecology.
The first attempts to differentiate zones were based on tidal classification (Boaden & Seed, 1985). It is easy to distinguish (Brehaut, 1982) a sub-littoral zone (one which is never completely uncovered by water), a supra-littoral zone (never completely covered), and a littoral zone (where periodic covering and uncovering by water is normal). These are little more than terms of convenience however, as the extreme high and low levels of tide may only be reached at intervals a considerable number of years apart. Since many organisms that dwell on rocky shores are annuals, this is of no significance to them.
Although zonation is related to tides, it is influenced by other factors (discussed below). Indeed, Stephenson and Stephenson (1972) note, “Zonation, although undoubtedly related to tides, is not directly caused by them.” Lewis (1964) emphasises that restricting zones to tidal boundaries causes confusing terminology. The littoral zone should not be defined in relation to sea level, but rather as a strip of the shore which undergoes alternating periods of exposure to air and submersion under seawater, and where characteristic communities of organisms thrive.
Stephenson and
References: Achituv, Y. (1972). The zonation of Tetrachthamalus oblitteratus Newman, and Tetraclita squamosa rufotincta Pilsbry in the Gulf of Elat, Red Sea. Journal of Experimental Marine Biology and Ecology 8: 73-81. Allanson, B. R. (1958). Some aspects of the ecology of the molluscan genus Siphonaria in South Africa. Portugalia Acta Biologica. Serie B 6: 179-212 Bannister, J Boaden, P. J. S. and Seed, R. (1985). Life on Rocky Coasts. In An Introduction to Coastal Ecology, pp. 35-58. Glasgow: Blackie and Son Limited. Bolton, J. J. (1981). Community analysis of vertical zonation patterns on a Newfoundland rocky shore. Aquatic Botany 10: 299-316. Branch, G. M. (1975). Ecology of Patella species from the Cape Peninsula, South Africa. IV: Desiccation. Marine Biology 32: 179-188. Branch, G. M. (1981). The biology of limpets: physical factors, energy flow, and ecological interactions. Oceanography and Marine Biology Annual Review 19: 235-380. Brehaut, R. N. (1982). Ecology of Rocky Shores. London: Edward Arnold (Publishers) Limited. Crisp, D. J. (1984). Overview of research on marine invertebrate larvae, 1940-1980. In Marine Biodeterioration: An Interdisciplinary Study (ed. J. D. Costlow and Tipper, R. C.), pp. 103-126. Annapolis, Maryland: Naval Institute Press. Davies, P. S. (1969). Physiological ecology of Patella. III: Desiccation effects. Journal of the Marine Biology Association U.K. 49: 291-309 Denley, E Lewis, J. R. (1964). The Ecology of Rocky Shores. London: English University Press. Santelices, B. (1990). Patterns of reproduction, dispersal, and recruitment in seaweeds. Oceanography and Marine Biology Annual Review 28: 177-276. Seed, R. (1969). The ecology of Mytilus edulis (Lamellibranchiata) on exposed rocky shores. 2. Growth and mortality. Oecologia 3: 317-350. Simpson, R. D. (1976). Physical and biotic factors limiting the distribution and abundance of littoral molluscs on Macquarje Island (sub-Antarctic). Journal of Experimental Marine Biology and Ecology 21: 11-49. Stephenson, T. A. and Stephenson, A. (1972). Scientific Introduction. In Life Between Tidemarks on Rocky Shores, pp. 15-19. San Francisco: W. H. Freeman and Company. Stirling, H. P. (1982). The upper temperature tolerance of prosobranch gastropods of rocky shores at Hong Kong and Dar es Salaam, Tanzania. Journal of Experimental Marine Biology and Ecology 63: 133-144. Tait, R. V. and Dipper, F. A. (1998). The Seashore. In Elements of Marine Ecology, pp 256-303. Oxford: Butterworth-Heinemann. Yonge, C. M. (1949). The Sea Shore. London: Collins. Lewis, J. R. (1978). The Ecology of Rocky Shores. London: Hodder and Stoughton. Street, P. (1952). Between the Tides. London: University of London Press Ltd. Waller, G. (2000). Biology of Marine Environments. In Sealife – A Guide to the Marine Environment. Robertsbridge: Pica Press. Wilson, D. P. (1951). Life of the Shore and Shallow Sea. London: Nicholson and Watson.