Some factors affecting the upper limit of the southern bull kelp Durvillaea antarctica (Chamisso) Hariot on two New Zealand shores

Experimental removal of limpets from intertidal rock above the low tidal band of the bull kelp Durvillaea antarctica on the Kaikoura coast enabled kelp sporelings to colonize levels up to 1.6 m above the normal upper margin of the kelp band. A similar experiment on the southeast Otago coast involving the removal of both barnacles and limpets did not have the same effect. The sporelings which grew above the kelp band at Kaikoura were unable to survive hot, dry conditions during summer, and it appears that although removing limpets did raise the level colonized by sporelings, the upper margins of the D. antarctica band is determined mainly by the physiological tolerance of sporelings to desiccation. The upper margin of the D. antarctica band is shown to be higher on the shore in southeast Otago than at Kaikoura. This difference is attributed to the relatively cooler and moister conditions that occur during summer in southeast Otago.