The Effects Of Harvesting Macrocystis Pyrifera On Understory Algae In Carmel Bay California

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ISBN 13 :
Total Pages : 57 pages
Book Rating : 4.:/5 (79 download)

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Download or read book Ecological and Chemical Responses Macrocystis Spp (phaeophyceae) Under Primitive Harvesting Methods written by and published by . This book was released on 2010 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: Kelp harvesting and its ecological impacts on Chilean near shore communities have been well documented throughout the last twenty years. However, regulation of this industry is fairly recent and extraction methods that maintain resilience of kelp forests have never been designed. Therefore, it is imperative to develop sustainable ways of kelp extraction, especially for species such as Macrocystis pyrifera, due to their economical importance and fragile situation in northern Chile. In addition, chemical variation of the primary products obtained by this industry under repetitive harvesting of kelp populations has never been examined and it is not known if the quality of these products is reduced through time. To investigate this, two experimental harvesting treatments of natural M. pyrifera populations in Chile were tested in order to identify an alternative extraction method that is less destructive than the one currently used - where all adult individuals in the population are removed by hand. Since M. pyrifera grows primarily on boulders throughout northern Chile, all individuals on a boulder were hereafter considered as an algal unit. The two harvesting treatments tested were (1) half of the kelp biomass per algal unit was removed, and (2) all of the biomass per algal unit was removed from half of the algal units. In addition, a negative control where all the biomass was removed from all the algal units, and a positive control were no harvesting was performed were also established. Understory algal composition, herbivore densities, growth of new stipes, and recruitment of new M. pyrifera were monitored weekly in each treatment for two and a half months in summer 2009. Results suggest that removing only half of the biomass per algal unit was the most sustainable way of harvesting; no significant differences in understory algal community were observed, there was a constant growth of new stipes in each algal unit, physical abrasion (i.e. "whiplash effect") by the remaining stipes reduced herbivore presence on the boulders, and recruitment of new M. pyrifera sporophytes was maintained. In addition, variation of alginate quality and percentage of major macromolecules (proteins, lipids, crude fiber, carbohydrates and calories) under short-term harvesting and long-term harvesting pressure were analyzed to examine if there was a significant effect of repeated harvesting on these properties. No significant differences in these compounds were found over either a short-term (3.5 months) or after long-term (approximately 15 years) repetitive harvesting, suggesting that repetitive harvesting does not negatively impact the final products. Consequently, my results recommend the extraction of half of the biomass per algal unit within an area to obtain an ecologically sustainable industry focused on northern Chilean M. pyrifera populations, and with a harvesting frequency that depends exclusively on the time required for recovery of new stipes.