Physiological and biochemical data for an experiment examining transgenerational effects in response to MHWs in S. purpuratus from the Santa Barbara Channel

Kelp forests of the Santa Barbara Channel have experienced prolonged marine heatwave (MHW) events that overlap in time with the phenology of life history events (e.g., gametogenesis and spawning) of marine invertebrates. To study the effect of thermal stress from MHWs during gametogenesis in the purple sea urchin (Strongylocentrotus purpuratus), adult urchins were acclimated to two conditions in the laboratory – a MHW (18°C) and a non-MHW (13°C) temperature at a time when gametogenesis would occur in situ. Following a four-month long acclimation period (October– January), adults were spawned and offspring from each parental condition were reared at MHW and non-MHW temperatures, creating a total of four offspring treatments. To assess for transgenerational effects in gamete traits, we measured egg size and biochemical composition. In addition, evidence of transgenerational effects was assessed by measuring embryo size and thermal tolerance of the progeny. Results indicated that MHW temperatures did affect life history traits. MHW-acclimated females had eggs with higher protein concentrations. Additionally, maternal thermal history influenced embryo body size at multiple stages of development while offspring developmental temperatures influenced body size only at the prism stage. Lastly, embryos from MHW-acclimated females were more thermally tolerant with higher LT50 values as compared to progeny from non-MHW-acclimated females. Overall, results showed that the thermal history of female S. purpuratus and developmental temperature influenced offspring traits and performance indicating that prolonged thermal stress, when it occurs during critical life history events, could influence reproductive success in situ. Moreover, our results suggest that transgenerational acclimation may aid in the capacity to resist the thermal stress associated with MHWs during early development in S. purpuratus.