The effects of the environment on the reproduction and early performance of the habitat-forming kelp Ecklonia radiata (C. Agardh) J. Agardh

[Truncated abstract] Many organisms display patterns in the intensity, frequency and synchrony of reproduction, which are influenced by the physical environment. Knowledge of how environmental factors underpin reproduction and early life-stage ecology is critical to assessing the persistence of populations and the ecosystem services they provide. In marine systems, some of the major factors which are known to influence the reproduction of ecologically important seaweeds are sea temperature, light, nutrients and wave action. Kelps (Order: Laminariales) are the major habitat-forming species on warm-temperate to polar subtidal reefs. Kelps have a biphasic, diplohaplontic, heteromorphic life cycle. Most kelp studies have focused on the ecology of the macroscopic sporophyte while comparatively little is known about their reproductive ecology and the ecology of the microscopic gametophyte stage. However, an understanding of all life stages is required to appreciate the dynamics and persistence of populations. Ecklonia radiata is the major habitat-forming kelp in temperate Australia where it plays a pivotal role in structuring shallow, inshore communities, by providing habitat and energy to higher trophic levels. Little is known about the reproduction of this ecologically significant species in Australia, and the role the environment plays in controlling it. Thus, the general aim of this thesis was to determine spatial and temporal patterns in the reproduction of E. radiata, and to examine the role of environmental drivers on zoospore production and release, and early gametophyte growth and survival. In order to study the juvenile phase of the kelp life cycle it is necessary to collect zoospores for experimentation; however, no standardised method for the extraction of zoospores exists. Hence the first experiment chapter (chapter two) reviewed zoospore release methods for Laminariales in order to develop an effective technique.