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The role of fluctuating food supply on recruitment, survival and population dynamics in the sea
- Okamoto, Daniel K.
- Advisor(s): Holbrook, Sally J
Abstract
This collection of work focuses on dynamics of two marine taxa with very different life histories, both of whom are sensitive to changes in food supply. Chapters 1 and 2 focus on black surfperch (Embiotoca jacksoni), a direct developer with internal reproduction while chapters 3 and 4 focus on the purple sea urchin (Strongylocentrotus purpuratus a broadcast spawner with pelagic larvae. Chapter 1 was published in Proceedings of the Royal Society: B in 2012, and is co-authored by Russ Schmitt, Sally Holbrook and Dan Reed. In this chapter I used long-term data on surfperch and their prey to illustrate how variability food for surpferch corresponds to changes in the number of young that adults produce and how well those young survive. Chapter 2 provides evidence that survival in adult surfperch responded to both prey availability and competition among adults. This work is a collaboration with Russ Schmitt and Sally Holbrook. Chapter 3 focuses on fertilization dynamics in sea urchins and the role that varying egg concentrations during spawning can have on the rate of fertilization when mixed with sperm. I conducted laboratory experiments and developed new models to show that the per capita rate of interactions among eggs and sperm slow down as egg concentrations increase. Finally, in chapter 4 I used a 23-year dataset of larval settlement of purple urchins at seven sites to investigate whether settlement patterns were related to major climatic and biological variables including food supply and temperature. This chapter is an ongoing collaboration with Steve Schroeter, Dan Reed and several others. These analyses show a strong, negative relationship between settlement and El Nino cycles as well as temperature in southern California, indicating that multi-year fluctuations in climate may regulate the patterns of settlement that are highly variable in time. Collectively, these chapters highlight the importance of considering complex interactions and nonlinearities in dynamics of marine species.