Assessing physiological tipping point of sea urchin larvae exposed to a broad range of pH

• Published in: Global Change Biology
• Main Authors: Dorey, Narimane, Lançon, Pauline, Thorndyke, Mike, Dupont, Sam
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Ocean acidification
• Online Access: http://dx.doi.org/10.1111/gcb.12276; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fgcb.12276; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.12276

Abstract Our ability to project the impact of global change on marine ecosystem is limited by our poor understanding on how to predict species sensitivity. For example, the impact of ocean acidification is highly species‐specific, even in closely related taxa. The aim of this study was to test the hypothesis that the tolerance range of a given species to decreased pH corresponds to their natural range of exposure. Larvae of the green sea urchin S trongylocentrotus droebachiensis were cultured from fertilization to metamorphic competence (29 days) under a wide range of pH (from pH T = 8.0/ p CO 2 ≈ 480 μatm to pH T = 6.5/ p CO 2 ≈ 20 000 μatm) covering present (from pH T 8.7 to 7.6), projected near‐future variability (from pH T 8.3 to 7.2) and beyond. Decreasing pH impacted all tested parameters (mortality, symmetry, growth, morphometry and respiration). Development of normal, although showing morphological plasticity, swimming larvae was possible as low as pH T ≥ 7.0. Within that range, decreasing pH increased mortality and asymmetry and decreased body length (BL) growth rate. Larvae raised at lowered pH and with similar BL had shorter arms and a wider body. Relative to a given BL, respiration rates and stomach volume both increased with decreasing pH suggesting changes in energy budget. At the lowest pHs (pH T ≤ 6.5), all the tested parameters were strongly negatively affected and no larva survived past 13 days post fertilization. In conclusion, sea urchin larvae appeared to be highly plastic when exposed to decreased pH until a physiological tipping point at pH T = 7.0. However, this plasticity was associated with direct (increased mortality) and indirect (decreased growth) consequences for fitness.