Increased temperature but not pCO2 levels affect early developmental and reproductive traits of the economically important habitat-forming kelp Lessonia trabeculata

Highlights: • Climate predictions suggest changes in temperature and pCO₂ levels of the ocean. • The effects of those changes on the kelp Lessonia trabeculata were studied. • The pCO₂ levels had no effects on most early developmental traits. • Temperature increments affected female gametophyte growth and the kelp fertility. • We suggest that mainly temperature increments affect the kelp recruitment. - Abstract: The effects of ocean warming and ocean acidification on developmental and reproductive traits of Lessonia trabeculata were evaluated. Meiospores were cultured for 35 days in an experimental mesocosm where temperature (~15 and 19 °C) and partial CO₂ pressure (pCO₂, ~400 and 1300 μatm) were controlled. The results indicate that germination was reduced at 19 °C, whereas the increase of pCO₂ only had effects at 15 °C. Likewise, the increase in temperature significantly affected the vegetative growth of female gametophytes. Sex ratio was not affected significantly by any of the variables studied. Fertility and reproductive success decreased by about 50% at 19 °C. The pCO₂ levels had no significant effects on most early developmental traits. The results suggest that ocean warming or periodic warming events (e.g. an El Niño event) might affect the recruiting capacity of this or other similar species by affecting their early developmental stages.