South China Sea Annual Meeting 2023 (SCSAM)

37 / 2023-07-24 15:08:00

Physiological and intergenerational carry-over effects of marine heatwaves on an economically and ecologically important sea urchin

carryover effects, climate change, marine heatwave, sea urchin, thermal physiology

The potential of populations to persist under extreme conditions, such as marine heatwaves (MHW), relies on individuals being able to both survive and reproduce. Fundamentally, this depends on the capacity of an organism to (1) physiologically acclimatize to, and recover from, thermal stress, and (2) pass on resistance to the next generation. To elucidate whether heat-conditioning of parents could benefit offspring development, we exposed adult sea urchins (Heliocidaris erythrogramma) to ambient summer (23°C), moderate (25°C) or strong (26°C) MHW conditions for 10 days, followed by spawning to produce larvae. Offspring were then reared along a thermal gradient (22-28°C) and development tracked. In adult urchins, greater MHW intensity drove higher metabolic rates which were not matched with an increase in food consumption, ultimately leading to latent negative physiological effects that caused mortality even when conditions returned to normal. Interestingly, progeny from the MHW conditioned adults developed through to metamorphosis faster, and were larger, than those of ambient conditioned parents. In contrast, most offspring from the control summer temperature died before metamorphosis at temperatures above 25°C (a moderate MHW). Initial survival was higher in the progeny of MHW exposed parents, even at temperatures hotter than predicted MHWs (28°C). Importantly, however, there was substantial mortality of juveniles from the strong MHW parents within two weeks. Therefore, while carryover effects of parental conditioning to MHWs resulted in faster growing, larger progeny, this benefit will only persist beyond the more sensitive juvenile stage and enhance survival if conditions return promptly to normal ambient temperatures.