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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps13236

Key biological responses over two generations of the sea urchin Echinometra sp. A under future ocean conditions

S. Uthicke*, F. Patel, S. Karelitz, H. M. Luter, N. S. Webster, M. Lamare

*Corresponding author:

ABSTRACT: Few studies investigate effects of ocean warming and acidification on marine benthic organisms over ecologically relevant time scales. We use an environmentally controlled coral reef mesocosm system to assess growth and physiological responses of the sea urchin species Echinometra sp. A over two generations. Each mesocosm was controlled for temperature and pCO2 over 29 months under three climate change scenarios (present day, predicted state at 2050 and 2100 under RCP8.5). The system maintained treatment conditions including annual temperature cycles and a daily variation in pCO2. Over 20 months, adult Echinometra exhibited no significant difference in size and weight among the treatments. Growth rates and respiration rates did not differ significantly among treatments. Urchins from the 2100 treatment had elevated ammonium excretion rates and reduced O2:N ratios, suggesting a change in catabolism. We detected no difference in spawning index scores or oocyte size after 20 months in the treatments, suggesting gonad development was not impaired by variations in pCO2 and temperature reflecting anticipated climate change scenarios. Larvae produced from experimentally exposed adults were successfully settled from all treatments and raised for 5 months inside the mesocosm. The final size of these juveniles exhibited no significant difference among treatments. Overall, we demonstrated that the mesocosm system provided a near natural environment for this urchin species. Climate change and ocean acidification did not affect the benthic life stages investigated here. Importantly, in previous short-term (weeks to months) experiments this species exhibited reductions in growth and gonad development, highlighting the potential for short-term experiments with non-acclimated animals to yield contrasting, possibly erroneous results.