Variation in Propagule Supply and its Role in Kelp-Forest Regeneration

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Kelp forests, dominant of subtidal temperate reefs worldwide, often undergo relatively frequent and unpredictable local extinctions and recolonization. This investigation is a continuation of long-term research on the causal mechanisms producing widespread loss and regeneration of subtidal kelp communities. While the causes for the rapid decline of kelp populations are becoming clear, the mechanisms that allow for their rapid recovery following severe disturbance remain poorly understood. The research will use laboratory and field experiments to examine various aspects of propagule supply that promote recolonization following widespread forest loss. The major areas of study will involve determining patterns and environmental causes of variation in (1) the number of spores produced by adult plants, (2) the timing of spore release, (3) spore quality, and (4) the longevity of spore supply. The research will focus on two species of kelp (Macrocystis pyrifera and Pterygophora california) that form much of the biogenic structure of subtidal reef communities of central and southern California. The research is important because it explores the supply side of the regenerative process which has largely been ignored in studies of patch dynamics. It will fill an important gap in our knowledge of the complicated processes leading to successful recruitment. Such a comprehensive approach is a necessary (but rarely taken) step towards gaining a thorough understanding of the mechanisms that regulate marine communities.