The Biology of Laminaria Hyperborea. VIII. Growth on Cleared Areas

Abstract

INTRODUCTIONStudies of established populations of Laminaria hyperborea (Gunn.) Fosl. have indicated that there is often less change of growth rate with depth than might be expected to result from the decrease in irradiance (Kain, 1967; Lüming, 1969; Jupp & Drew, 1974). This has been attributed to self-limitation by the canopy of Laminaria fronds (Lüning, 1969; Kain et al. 1976). The removal of this canopy can result in fast growth in shallow water (Kitching, 1941; Svendsen, 1972) and a marked differential in growth rate over a small depth range (Svendsen, personal communication). A series of rocky subtidal areas at two depths off the Isle of Man was cleared of vegetation at various times (Kain, 1975a). This provided an opportunity to make growth measurements on individuals of known age in the absence of a canopy formed by older plants.