headshot of Stephen Whitaker

PhD Student

Year Admitted
2018

Year Graduated
2023

Faculty Advisors
Steve Gaines and Robert Miller

Committee
Hunter Lenihan

Dissertation Title & Abstract

Assessing Decline and Recovery of Rocky Intertidal Foundation Species Using Long-Term Data

Rocky intertidal ecosystems have been significantly degraded. Of particular concern is the decline of rockweeds. As foundation species, rockweeds increase biodiversity by decreasing environmental stress under their canopy. To determine the status of the dominant rockweed species in southern California, Silvetia compressa, I analyzed canopy cover data from 30 sites spanning 18 years. I found that the rockweed had declined markedly at sites south of Point Conception. Analyses revealed that substantial declines in Silvetia cover were associated with strong, offshore Santa Ana wind events. To assess the recovery of disturbed rocky intertidal ecosystems, I analyzed 28 years of data from a controlled disturbance experiment at a remote site. I found the recolonization rates for species cleared to be highly variable ranging from years to decades, and that even relatively mild disturbances can have long-lasting effects on rockweeds. Since rockweeds have sustained extensive degeneration worldwide, and recovery of impacted rockweed populations is typically slow and unpredictable, I propose that rockweeds are optimal candidates for restoration. In my third chapter, I summarize the current knowledge of rockweed ecology, highlighting studies that could inform restoration practices, and recommend ways to improve our ability to implement scalable restoration of rockweeds and accompanying ecosystem-wide

Education
MS, Marine Biology, California State University, Fullerton
BS, Marine Biology, College of Charleston, South Carolina

Research Areas
Marine ecology, restoration ecology, and climate change