Importance of kelp population strategies: annual vs. perennial Macrocystis pyrifera population dynamics under a changing environmental scenario

Alejandro H. Buschmann

Centro i~mar & CeBiB, Universidad de Los Lagos, Puerto Montt, Chile

This presentation summarizes our work over the past two decades with the giant kelp Macrocystis pyrifera trying to understand how annual populations of this kelp species can couple alternate and time separated sporophytic cohorts. The relevance of the development of microscopic stages, sexual reproduction and recruitment success, have been studied following natural annual and perennial populations of M. pyrifera along with laboratory experiments to assess their capacities to sustain its abundance in southern Chile.  Annual populations present characteristic traits in southern Chile (40° S), these populations are maintained by presenting microscopic stages for 3 to 4 months allowing the coupling of time separated sporophytic generations. Sexual reproduction success and fertilization are also dependent on some critical environmental conditions (e.g. temperature, nutrient availability), but also showing alternative reproduction capacities (e.g. partenogenesis) and differentiated interpopulation fertility success, allowing to maintain the populations even under stressful conditions. The viability of these annual populations under a changing climate conditions are discussed in this lecture.