Maintained larval growth in mussel larvae exposed to acidified under-saturated seawater

Abstract

Ocean acidification (OA) is known to affect bivalve early life-stages. We tested responses of blue mussel larvae to a wide range of pH in order to identify their tolerance threshold. Our results confirmed that decreasing seawater pH and decreasing saturation state increases larval mortality rate and the percentage of abnormally developing larvae. Virtually no larvae reared at average pHT 7.16 were able to feed or reach the D-shell stage and their development appeared to be arrested at the trochophore stage. However larvae were capable of reaching the D-shell stage under milder acidification (pHT ≈ 7.35, 7.6, 7.85) including in under-saturated seawater with Ωa as low as 0.54 ± 0.01 (mean ± s. e. m.), with a tipping point for normal development identified at pHT 7.765. Additionally growth rate of normally developing larvae was not affected by lower pHT despite potential increased energy costs associated with compensatory calcification in response to increased shell dissolution. Overall, our results on OA impacts on mussel larvae suggest an average pHT of 7.16 is beyond their physiological tolerance threshold and indicate a shift in energy allocation towards growth in some individuals revealing potential OA resilience.

A comparison of life-history traits in calcifying Spirorbinae polychaetes living along natural pH gradients

“…This in partial agreement with Saderne and Wahl, (2013), where growth 420 rates and recruitment of spirorbid Spirorbis spirorbis individuals at extreme low pH/ high 421 pCO2 levels (3150 ± 446 μatm) were significantly reduced, whereas at more realistic pH levels for end of the century projections, individuals did not show any adverse effects (Saderne & Wahl 2013). These pH values closely correspond to the low (S2) and extreme low (S3) pH values in this study and corroborate the idea that each species has specific pH 'tipping' points, as demonstrated in the larval mussels' development, Mytilus edulis (Ventura et al 2016). This theory that physiological tipping points may limit populations' pH tolerance complements that of Lucey et al 2016, where abnormally low pH values at the low pH site (S2) may have confounded a potential local adaptation signature.…”

Resilience of the larval slipper limpet Crepidula onyx to direct and indirect-diet effects of ocean acidification

“…fornicata 26 . Blue mussel Mytilus edulis larvae also showed high feeding rates at pH 7.35 53 . This observed increase in clearance rate could potentially incur energetic cost and affect energy allocation.…”

Physiological plasticity and local adaptation to elevated pCO2 in calcareous algae: an ontogenetic and geographic approach

“…Using a broader range of partial pressures of pCO 2 will help to investigate whether there is a tipping point in the growth and calcification of C. vancouveriensis from the northern populations and how it relates to the high pCO 2 variability at those locations. In other taxa such as mussels and sea urchins, tipping points in larval physiology have been associated with the extreme pCO 2 values of the present natural variability (Dorey, Lançon, Thorndyke, & Dupont, ; Ventura, Schulz, & Dupont, ). However, not all organisms show a clear threshold in physiological decline (i.e., tipping point) in response to pCO 2 values above extreme values in the natural environment (Comeau, Edmunds, Spindel, & Carpenter, ).…”

“…vancouveriensis from the northern populations and how it relates to the high pCO 2 variability at those locations. In other taxa such as mussels and sea urchins, tipping points in larval physiology have been associated with the extreme pCO 2 values of the present natural variability(Dorey, Lançon, Thorndyke, & Dupont, 2013;Ventura, Schulz, & Dupont, 2016). However, not all organisms show a clear threshold F I G U R E 3 Net photosynthetic productivity (A) and respiration (B) under high and low pCO 2 levels in adults of Corallina vancouveriensis from sites in California located north (Cambria and Arroyo Grande) and south (Santa Barbara and Carpinteria) of Point Conception (n = 24, mean ± SE).…”