The Interaction of Ocean Acidification and Food Availability on Growth and Metamorphosis in the Gastropod Crepidula fornicata
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The earth’s oceans are becoming more acidic due to absorption of atmospheric CO2. Ocean acidification decreases the concentration of carbonate ions in seawater, and imposes increased energy costs on organisms that deposit calcium carbonate shells and skeletons. Larval stages of these organisms are especially vulnerable to stresses of acidification and nutrition, which may have a common energetic basis. We investigated how acidification and nutrition affected pre-competent larval growth of the slipper limpet Crepidula fornicata during the first 8 days after hatching. We also asked if a four-day period of food and/or acidification stress, applied to older competent larvae, affected speed of metamorphosis and juvenile growth after stresses were relieved. Treatments in both experiments used all 4 combinations of pH 7.8 or 7.4, and high or low food concentration (15x104 or 1x104 cells/ml Isochrysis galbana). Lower food level in the pH 7.8 treatments resulted in decreased growth rates for pre-competent larvae (p<0.0001), while larvae failed to grow in the pH 7.4 treatments regardless of food level. Competent larvae were unaffected by either pH or nutrition level over the course of a four-day stress period indicated by their inability to grow. Increased acidification extended the latency of KCl-induced metamorphosis in the second experiment (p < 0.0309), but nearly all larvae completed metamorphosis within 24 hours. Together, acidification and low food availability decreased subsequent juvenile growth in the first 6 days after metamorphosis (p<0.01), demonstrating latent effects of larval experience.