Kelps inhabit a narrow band of the Earth's ocean margins, yet they sustain some of the most diverse and productive ecosystems on the planet. Despite over 50 years of intensive field and laboratory research, however, much remains to be understood about the processes that determine the dynamics of kelp populations, and the subsequent consequences for the diversity and productivity of their associated communities. This limitation is due largely to the fact that processes regulating kelp system productivity, dynamics, and diversity are determined by how different kelp species interact with environmental variability over ecological and evolutionary timescales. In the face of imminent ocean climate change, how will individual kelp taxa respond to rising ocean temperatures or decreasing nutrients? This project will use a combination of laboratory and field studies to understand interactive effects of changing temperature and nutrients on gametogenesis, fertilization, and sporophyte recruitment of kelp. This project will use 9 kelp taxa from California, British Columbia, Australia, Mexico, South Africa, and Chile to test for local adaptation vs. phylogenetic patterns in these traits and to understand whether the level of stress experienced by a population determines regional tolerance patterns. The project will integrate research activities into a novel curriculum at Moss Landing Marine Laboratory and will involve students in laboratory and field studies. These activities will help students to develop good laboratory skills and facilitate the development of critical-thinking as it pertains to the comparative analysis of kelp life histories, conceptual models of life history evolution, and ecological implications of climate change.
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%.
