The development and phenology of Ecklonia radiata (C.Ag.) J.Ag.

Restricted Item. Print thesis available in the University of Auckland Library or may be available through Inter-Library Loan. A three year study was made of the relation between the physical environment and the growth and reproduction of Ecklonia radiata (C.Ag.)J.Ag., a laminarian which can form extensive forests in the warm temperate waters of the Southern Hemisphere. Field studies involving extensive sampling of sporophytes from contrasting environments and the monitoring of tagged individuals were supplemented by the study of the gametophytes and young sporophytes in culture to give a description of morphological development of both generations. Aspects of the environment of the study sites were assessed and related to phenology and morphological variation. Although the general pattern of sporophyte growth was similar in different environments, the rate of growth, seasonal patterns of growth and reproduction, the degree of stipe elongation and the frond morphology varied with depth, wave exposure and shading. Growth rates and phenology also varied with the stage of plant development. Yearly productivity can be 3-6 kg m-2 at 6-8m depth; it falls to 0.3-0.5 kg m-2 at 14-16m. The performance of gametophytes in culture did not vary consistently with the age or local environment of the sporophyte parent but did vary with geographical position, season and condition of light, temperature, nutrients and salinity. Growth proceeded in a daily quantum dose of 0.86 μE cm-2 and the growth rate increased with increasing light up to 40 μE cm-2. Above this point the gametophytes could reproduce, and the interaction between the vegetative and reproductive modes of development resulted in great variability so that there was no clear cut trend with increasing quantum dose. Gametophytes and young sporophytes were damaged by sunlight. The temperature tolerance range far reproduction, 8-24°C, coincided with the geographical temperature range experienced by the species. The optimum for both growth and reproduction was 15-20°C.

Restricted Item. Print thesis available in the University of Auckland Library or may be available through Inter-Library Loan.