Short- and long-term consequences of larval stage exposure to constantly and ephemerally elevated carbon dioxide for marine bivalve populations

[摘要] While larval bivalves are highly sensitive to oceanacidification, the basis for this sensitivity and the longer-termimplications of this sensitivity are unclear. Experiments were performed toassess the short-term (days) and long-term (months) consequences of larvalstage exposure to varying CO₂ concentrations for calcifying bivalves.Higher CO₂ concentrations depressed both calcification rates assessedusing ⁴⁵Ca uptake and RNA : DNA ratios in Mercenaria mercenaria andArgopecten irradians larvae with RNA : DNA ratiosbeing highly correlated with larval growth rates (r²>0.9).These findings suggested that high CO₂ has a cascading negativephysiological impact on bivalve larvae stemming in part from lowercalcification rates. Exposure to elevated CO₂ during the first fourdays of larval development significantly depressed A. irradians larval survival rates,while a 10-day exposure later in larval development did not, demonstratingthe extreme CO₂ sensitivity of bivalve larvae during first days ofdevelopment. Short- (weeks) and long-term (10 month) experiments revealedthat individuals surviving exposure to high CO₂ during larvaldevelopment grew faster when exposed to normal CO₂ as juvenilescompared to individuals reared under ambient CO₂ as larvae. Theseincreased growth rates could not, however, overcome size differencesestablished during larval development, as size deficits of individualsexposed to even moderate levels of CO₂ as larvae were evident evenafter 10 months of growth under normal CO₂ concentrations. This "legacyeffect" emphasizes the central role larval stage CO₂ exposure can playin shaping the success of modern-day bivalve populations.

[学科分类] 地球化学与岩石