Recruitment strategies of Ulva and Porphyra in central California.

Abstract

RECRUITMENT STRATEGIES OF ULVA AND PORPHYRA IN CENTRAL CALIFORNIA by Rosemary Romero Ephemeral algae are early colonizers of the rocky intertidal zone after a disturbance, although the mechanism of early colonization (including benthic microscopic stages and waterborne propagules) is poorly known. Recruitment of the ephemeral Ulva spp. was studied in two types of disturbance manipulations (partial removal of all macroscopic organisms were removed vs. complete removal of all macroand microscopic organisms) and an un-manipulated control at two tidal heights (high Porphyra zone and low Mazzaella zone). Replicate disturbances were created in August 2007, November 2007, January 2008, and May 2008 and were monitored until August 2008 on a rocky bench north of Pigeon Point, California. Ulva colonization by waterborne propagules (complete removals) was observed throughout the year, whereas Porphyra was restricted to spring recruitment, as expected due to temporal cues (changes in photoperiod) regulating propagule availability. Peak Ulva responses varied in treatments as a function of timing of clearing, whereas peak Porphyra responses varied in locations as a function of timing of clearing. Location and interactions with location (heterogeneity among zones) explained most of the variability in early colonization. Fall and winter clearings experienced opposing responses by Ulva and Porphyra in each zone. Further experimentation is needed to rule out a negative interaction between Ulva and Porphyra in fall and winter disturbances. After some time, I realized that heterogeneity and instability must not be considered as just a drawback of field data to be neglected (averaged away or seen through by intuition) or circumvented by retreating into the laboratory because they are mere deviations from the typical or representative case (or even noise). On the contrary, heterogeneity and/or instability must be recognized as fundamental features of a natural situation. -Den Boer (1968) ACKNOWLEDGEMENTS This work was made possible by the support and guidance of many people. First I would like to thank my advisor, Dr. Mike Graham, and committee members Dr. Jim Harvey and Dr. Rick Zechman whose inquiring, input, and constant encouragement have made me a better scientist. I would like to give a special thanks to Dr. Graham who has additionally provided me with inspiration and countless opportunities to excel. To Dr. Kenneth Coale, Director of Moss Landing Marine Laboratories (MLML), who has put his heart and soul into this institution and makes it possible for students to work outside the box. I would also like to thank the faculty of MLML, especially Drs Diana Steller and Mike Foster. Dr. Steller and her husband Dr. Don Croll have been mentors to me since I attended UC Santa Cruz as an undergraduate and helped me realize my potential as a scientist. Dr. Foster was always willing to share his wealth of knowledge and opinion on tequila, seaweeds, and ecology. Field help was provided by many people who generously braved the cold and dark when required by the tides including: Mike Graham, Diana Steller, Aurora Alifano, Selena McMillan, Jennifer Jorve, Diana Kohtio, Thew Suskiewicz, Sam Rivera, Kyle Demes, Jasmine Ruvalcaba, Nora Grant, Megan Wehrenberg, Allison Gong, Ben Perlman, Kristine Williams, Shaara Ainsley, Meghan Frolli, Corinne Gibble, Ashley Neway, Kristen Green, Catalina Reyes, Elsie Tanadjaja, Paul and Bailey Tompkins, Jasmine Maurer, Kim Quaranta, Hilary Hayford, Phil Hoos, Jennifer Broughton, Colleen Young, Karl Jarmolowicz, Shelby Boyer, Brynn Hooton, and Sarah Jefferies. I would also like to thank Dr. Stacy Kim and Bob Zook for use of their metal detector.