Examining the Effects of Varying pCO2 Conditions on the Early Development of the Painted Sea Urchin, Lytechinus pictus

Buyanzaya Buyanurt, University of California Santa Barbara, Santa Barbara, United States, Terence S Leach, Univeristy of California Santa Barbara, Ecology, Evolution and Marine Biology, Santa Barbara, CA, United States and Gretchen Hofmann, University of California Santa Barbara, Department of Ecology, Evolution, and Marine Biology, Santa Barbara, CA, United States
As the concentration of atmospheric carbon dioxide (CO2) grows, ocean conditions become warmer and more acidic. Future ocean acidification and marine heat waves (MHWs) threaten the survival of marine organisms, particularly early stages in the plankton. As the frequency of MHWs and declining ocean pH advances, it is likely that these marine organisms will be exposed to multiple environmental stressors at a time. In this study, we sought to observe how different pCO2 conditions may alter the development and performance of a benthic marine invertebrate, with specific interests in whether these conditions will alter tolerance to an additional heat stress event during the larval stage. Our study organism was the summer-spawning painted sea urchin, Lytechinus pictus; L. pictus was chosen due to its role as both an ecologically important species and a developmental model. For the study, gametes were collected by spawning adult urchins and bulk crossed. Fertilized eggs were then separated into triplicate buckets maintained at either high (1136.4 μatm) or low (586.2 μatm) pCO2 treatments throughout early development. We sampled urchins at two developmental stages (gastrula and pluteus), and measured the effect of pCO2 on developmental success and body size. Upon reaching their larval stage, individuals were additionally assayed for thermal tolerance. Thermal tolerance trials revealed urchins that developed under high pCO2 conditions had higher tolerance to an acute heat stress event than those that developed under low pCO2 conditions. From our thermal tolerance results, we concluded that: (1) development under stressful conditions (high pCO2) had better prepared L. pictus larvae for another stressful event (high temperature), and (2) overall, L. pictus larvae were extremely resistant to high temperature stress. These results provide a framework for future research on L. pictus and serve as an indicator that these organisms show resilience in the face of climate change.