Some like it hot: Temperature and pH modulate larval development and settlement of the sea urchin Arbacia lixula

We studied the effects of temperature and pH on larval development, settlement and juvenile survival of a Mediterranean population of the sea urchin Arbacia lixula. Three temperatures (16, 17.5 and 19°C) were tested at present pH conditions (pHT8.1). At 19°C, two pH levels were compared to reflect present average (pHT8.1) and near-future average conditions (pHT7.7, expected by 2100). Larvae were reared for 52-days to achieve the full larval development and complete the metamorphosis to the settler stage. We analyzed larval survival, growth, morphology and settlement success. We also tested the carry-over effect of acidification on juvenile survival after 3days. Our results showed that larval survival and size significantly increased with temperature. Acidification resulted in higher survival rates and developmental delay. Larval morphology was significantly altered by low temperatures, which led to narrower larvae with relatively shorter skeletal rods, but larval morphology was only marginally affected by acidification. No carry-over effects between larvae and juveniles were detected in early settler survival, though settlers from larvae reared at pH7.7 were significantly smaller than their counterparts developed at pH8.1. These results suggest an overall positive effect of environmental parameters related to global change on the reproduction of A. lixula, and reinforce the concerns about the increasing negative impact on shallow Mediterranean ecosystems of this post-glacial colonizer. •Arbacia lixula can complete its development at 16 to 19°C at current (8.1) or near future pH (7.7).•Temperature enhances A. lixula development, increases larval survival and accelerates growth.•Mild acidification increases larval survival of A. lixula, but retards its growth.•Settlers' early survival is unaffected by changes in pH.•Global change may boost Mediterranean A. lixula populations, increasing its negative impact.