Examining the Effects of Varying pH Conditions on the Early Development of the Painted Sea Urchin, Lytechinus pictus

As the concentration of atmospheric carbon dioxide grows, ocean conditions become warmer and more acidic. These environmental consequences of global climate change threaten the survival of marine organisms, particularly those that undergo calcification. Asthe frequency of extreme heat and acidification events increase, it is likely that these marine organisms will be exposed to multiple environmental stressors at a time. In this study we sought to test how the larvae of a calcifying organism reacted when exposed to subsequent stress events. Our organism of focus was the summer-spawning painted sea urchin, Lytechinus pictus, due to its role as both an ecologically important species as well as a developmental model. In our study, gametes were collected by spawning adult urchins and combining the resulting sperm and eggs. Fertilized eggs were then separated into triplicate buckets maintained at either high (1136.4 μatm) or low (586.2μatm) pCO2 treatments throughout early development. Upon reaching their larval stage, individuals were measured for skeletal length, thermal tolerance, and developmental success. Thermal tolerance trials revealed urchins that had developed under high pCO2 conditions had higher tolerance to a thermal stress event than those that developed under low pCO2 conditions. Our results conveyed two major findings: (1) exposure to one stressful event had better prepared Lytechinus pictuslarvae for another stressful event and (2) Lytechinus pictuslarvae are extremely resistant to high temperature stress. Analysis of gene expression, lipids, and proteins will provide further understanding of the impacts of environmental stressors on Lytechinus pictus physiological performance