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I completed my dissertation in the Hofmann lab in summer of 2012. My dissertation research was centered around exploring the effects of anthropogenic-induced ocean acidification (OA) on larval sea urchins and the natural dynamics of ocean pH in coastal marine ecosystems. OA is predicted to strongly affect sea urchins and their larval stages may be especially vulnerable. I have conducted experiments here in Santa Barbara with the purple urchin (Strongylocentrotus purpuratus) and the red urchin (S. franciscanus) as well as at Friday Harbor Laboratories in Washington with the green urchin (S. droebachiensis). In addition to using biochemical approaches, the close evolutionary relationship between thee species facilitates the purple urchin as a foundation for creating molecule tools to study gene expression patterns in the ecologically and commercially important, but less studied, congeners.
In addition to these physiological studies, I was also interested in understanding the pH dynamics that organisms are currently experiencing in the nearshore marine environment. Such dynamics may play a large role in determining which species may have evolved to be "winners or losers" under future climate scenarios. This work is made possible by using autonomous pH sensors, called SeaFETS (images below), originally designed by Dr. Todd Martz at SIO. These SeaFETS allow us to collect high-frequency observations of pH to better understand the magnitude and patterns of variation that these marine species may be currently experiencing. I have used these sensors to observe pH variation here in California as well as under fast sea ice in Antarctica.This information can be valuable in constraining manipulative laboratory experiments to assess tolerance to OA stress.
I arrived in the Hofmann lab in Fall of 2007 after earning a Master’s degree in Biology working with Dr. Matthew Edwards at San Diego State University. While at SDSU, I examined how the physical environment affects the distribution and morphology of two understory kelp species, Pterygophora californica and Eisenia arborea, along California and the Baja California Peninsula. My research found that the southern distribution of Pterygophora may be limited to northern Baja California due to thermal sensitivity in its microscopic stages (gametophytes). Based on correlations between ocean climate and tissue carbon:nitrogen, the adult stages of both species appeared to be resilient to high temperatures and low nutrients. However, gametophytes of Pterygophora could only sexually reproduce and form sporophytes at 12 C but not 18 C, while Eisenia produced sporophytes at both temperatures. In addition to this work, I was fortunate to also be able to conduct subtidal research in Alaska, Peru, and Chile. These experiences have given me excellent perspective regarding how marine communities change across large spatial scales in addition to the rigors involved in remote fieldwork.
Hofmann GE, Smith JE, Johnson KS, Send U, Levin LA, et al. (2011) High-frequency dynamics of Ocean pH: a multiple ecosystem comparison. PLoS ONE 6(12): e28983.
Yu PC, Matson PG, Martz TR, Hofmann GE (2011) The ocean acidification seascape and its relationship to the performance of calcifying marine invertebrates: laboratory experiments on the development of urchin larvae framed by environmentally-relevant pCO2/pH. Journal of Experimental Marine Biology and Ecology 400: 288-295.
Fangue NA, O'Donnell MJ, Sewell MA, Matson PG, MacPherson AC and Hofmann GE (2010) A laboratory-based experimental system for the study of ocean acidification effects on marine invertebrate larvae. Limnology and Oceanography: Methods 8: 441-452.
Matson PG, Steffen BT, Allen RM (2010) Settlement behavior of cyphonautes larvae of the bryozoan Membranipora membranacea in response to different algal substrata. Invertebrate Biology 129 (3): 277-283.
Matson PG, Edwards MS (2007). Effects of ocean temperature on the southern range limits of two understory kelps, Pterygophora californica and Eisenia arborea, at multiple life stages. Marine Biology 151 (5): 1941-1949.