Award: OCE-0752523

This project aimed to establish whether the response of kelp recruitment to climate stressors (increased ocean temperature and decreased nutrients) was affected by either genetics or local acclimation to teh environment. The primary research objective for the project was to conduct a series of laboratory culture experiments under controlled temperature and nutrient conditions and assess the successful propagation of the kelp microscopic life history under such conditions. Individual experiments lasted 2-3 months and were conducted on different species from different collection sites within their distributional range. Additionally, field manipulations were conducted in California, British Columbia and Chile. In total, we conducted 31 laboratory culture experiments on 19 different kelp taxa, from four regions: central California, southern California, British Columbia and Chile. We sampled kelp taxa in each of the four kelp families. In every case, temperature was the overwhelming factor driving reproductive success, rather than nutrients as previously suggested. As such, all kelps responded to temperature with little variability among species. Contrary to current paradigms, nutrients had minimal impact on kelp recruitment. After completing all genetic and geographic sampling, we have concluded that, although temperature has a ubiquitously negative effect on kelp recruitment, the Macrocystae and Costariaceae clades have the ability to geographically acclimate to high temperature, and that the Lessoniaceae can tolerate the warmest temperatures of all clades; the Alariaceae is intolerant of rising temperatures and therefore may be the most vulnerable to climate change. The graduate and undergraduate students conducted 21 additional experiments related to their thesis research to further explore the mechanisms of kelp reproductive success. We met all of Year 1, 2, 3, and 4 laboratory and field objectives, and exceeded the number of proposed experiments by 50%. Last Modified: 07/31/2013 Submitted by: Michael H Graham