Effect of ocean acidification on the early life stages of the blue mussel Mytilus edulis

[摘要] Several experiments have shown a decrease of growth and calcification oforganisms at decreased pH levels. There is a growing interest to focus onearly life stages that are believed to be more sensitive to environmentaldisturbances such as hypercapnia. Here, we present experimental data,acquired in a commercial hatchery, demonstrating that the growth ofplanktonic mussel (Mytilus edulis) larvae is significantly affectedby a decrease of pH to a level expected for the end of the century. Eventhough there was no significant effect of a 0.25–0.34 pH unit decrease onhatching and mortality rates during the first 2 days of development norduring the following 13-day period prior to settlement, final shells wererespectively 4.5±1.3 and 6.0±2.3% smaller at pH_NBS~7.8 (pCO₂~1100–1200 μatm) than at acontrol pH_NBS of~8.1 (pCO₂~460–640 μatm). Moreover, a decreaseof 12.0±5.4% of shell thickness was observed after 15d of development.More severe impacts were found with a decrease of ~0.5 pH_NBSunit during the first 2 days of development which could be attributed to adecrease of calcification due to a slight undersaturation of seawater withrespect to aragonite. Indeed, important effects on both hatching andD-veliger shell growth were found. Hatching rates were 24±4% lowerwhile D-veliger shells were 12.7±0.9% smaller at pH_NBS~7.6 (pCO₂~1900 μatm) than at a control pH_NBS of ~8.1 (pCO₂~540 μatm). Although theseresults show that blue mussel larvae are still able to develop a shell inseawater undersaturated with respect to aragonite, the observed decreases ofhatching rates and shell growth could lead to a significant decrease of thesettlement success. As the environmental conditions considered in this studydo not necessarily reflect the natural conditions experienced by this speciesat the time of spawning, future studies will need to consider the wholelarval cycle (from fertilization to settlement) under environmentallyrelevant conditions in order to investigate the potential ecological andeconomical losses of a decrease of this species fitness in the field.

[学科分类] 地球化学与岩石