MEPS 563:169-184 (2017)  -  DOI: https://doi.org/10.3354/meps11973

ABSTRACT: The sea urchin Loxechinus albus is a benthic shallow water coastal herbivore and an exploited natural resource. This study evaluated the consequences of projected near-future ocean acidification (OA) and warming (OW) for small juveniles of this species. Individuals were exposed for 7 mo to contrasting pCO₂ (~400 and 1200 µatm) and temperature (~16 and 19°C) levels. We compared grazing rates during the first 2 mo of rearing. After an additional period (2 to 7 mo), we compared body size change (in terms of diameter, and wet and buoyant weight), self-righting, dislodgement resistance, foraging speeds, test dissolution rate, oxygen consumption and strength of structural integrity. Regardless of the temperature, urchins reared under present-day pCO₂ grazed preferentially on algae also reared under present-day pCO₂ conditions. However, urchins reared under elevated pCO₂ at both temperatures exhibited no grazing preference. Other traits such as growth rate in terms of diameter, vertical foraging speed and tenacity were not affected significantly by pCO₂, temperature and the interaction between them. However, growth rate in terms of wet weight, metabolism and dissolution rate of empty urchin tests was significantly affected by temperature and pCO₂ but not by the interaction between them. At 16°C, self-righting was faster for individuals reared at elevated pCO₂ but no differences were found at 19°C. We conclude that OA and OW may disrupt some early benthic ontogenetic traits of this species and thus have negative ecological and economic consequences. However, most traits will be not threated by the 2 investigated stressors.

KEY WORDS: Growth · Grazing rate · Tenacity · Structural integrity · Self-righting · Foraging speed · Loxechinus albus