Examining the effects of climate change on red sea urchin, Mesocentrotus franciscanus, a commercially valuable fishery species
The Problem
Ocean warming and ocean acidification are major consequences of increasing levels of carbon dioxide in Earth's atmosphere. Furthermore, factors such as ocean temperature and pH are predicted to often change simultaneously, leading to multi-stressor impacts on marine organisms. These organisms may be particularly vulnerable during their early development. The red sea urchin Mesocentrotus franciscanus is an ecologically and economically important fishery species harvested for its roe.
The Approach
My previous work investigated how the early developmental stages of M. franciscanus responded to various pH and temperature conditions. My experiments were informed by oceanographic sensor data collected by the Hofmann Lab at UC Santa Barbara to implement laboratory treatments that were ecologically relevant. After adults were induced to spawn, embryos and larvae were cultured under different experimental conditions. I used a combination of epigenetic, transcriptomic, and physiological approaches to investigate how these organisms are responding to current ocean conditions, and to predict how they will respond to future ocean acidification and warming.
Physiological effects
We found that warmer temperatures increase the body size of M. franciscanus embryos, offsetting the stunting effect of decreased pH on growth. Embryo thermal tolerance is slightly higher when they are raised under warmer temperatures. Metabolic rates, however, we not found to be affected by developmental temperature and pH conditions. In summary, early development under low pH conditions may adversely impact M. franciscanus while moderate warming may improve growth and thermal tolerance.
Molecular-level effects
Although transcriptomic patterns appear to primarily varied by developmental stage, there are pronounced differences in gene expression as a result of both temperature and pH conditions during early development. Differentially expressed genes were related to the cellular stress response, transmembrane transport, metabolic processes, and the regulation of gene expression. At each developmental stage, temperature contributed
significantly to the observed variance in gene expression, which was also correlated to the phenotypic attributes of
the embryos. On the other hand, the transcriptomic response to pH was relatively muted, particularly at the
prism stage of early development.
Related publications
Juliet M. Wong and Gretchen E. Hofmann (2021). Gene expression patterns of red sea urchins (Mesocentrotus franciscanus) exposed to different combinations of temperature and pCO2 during early development. BMC Genomics 22(32). https://doi.org/10.1186/s12864-020-07327-x​
​
Juliet M. Wong and Gretchen E. Hofmann (2020) The effects of temperature and pCO2 on the size, thermal tolerance and metabolic rate of the red sea urchin (Mesocentrotus franciscanus) during early development. Marine Biology 167(33). https://doi.org/10.1007/s00227-019-3633-y.
​
Juliet M. Wong, Juan D. Gaitán-Espitia, and Gretchen E. Hofmann (2019) Transcriptional profiles of early stage red sea urchins (Mesocentrotus franciscanus) reveal differential regulation of gene expression across development. Marine Genomics 48(100692). https://doi.org/10.1016/j.margen.2019.05.007.