Ion-transporting capacity and aerobic respiration of larval white seabass (Atractoscion nobilis) may be resilient to ocean acidification conditions

Highlights

  • Larval white seabass were lab-exposed to elevated CO2 levels simulating future ocean acidification (OA).
  • Exposure to OA did not induce any changes in ion-transporting capacity, aerobic respiration rate, or total length of larval white seabass.
  • Retroactive analysis of the water in broodstock tanks revealed the parents had been chronically exposed to elevated CO2 levels, which may have affected the physiology of the larvae and conferred the observed resilience.

Abstract

Ocean acidification (OA) has been proposed to increase the energetic demand for acid-base regulation at the expense of larval fish growth. Here, white seabass (Atractoscion nobilis) eggs and larvae were reared at control (542 ± 28 μatm) and elevated pCO2 (1,831 ± 105 μatm) until five days post-fertilization (dpf). Skin ionocytes were identified by immunodetection of the Na+/K+-ATPase (NKA) enzyme. Larvae exposed to elevated pCO2 possessed significantly higher skin ionocyte number and density compared to control larvae. However, when ionocyte size was accounted for, the relative ionocyte area (a proxy for total ionoregulatory capacity) was unchanged. Similarly, there were no differences in relative NKA abundance, resting O2 consumption rate, and total length between control and treatment larvae at 5 dpf, nor in the rate at which relative ionocyte area and total length changed between 2–5 dpf. Altogether, our results suggest that OA conditions projected for the next century do not significantly affect the ionoregulatory capacity or energy consumption of larval white seabass. Finally, a retroactive analysis of the water in the recirculating aquarium system that housed the broodstock revealed the parents had been exposed to average pCO2 of ~1,200 μatm for at least 3.5 years prior to this experiment. Future studies should investigate whether larval white seabass are naturally resilient to OA, or if this resilience is the result of parental chronic acclimation to OA, and/or from natural selection during spawning and fertilization in elevated pCO2.

Kwan G. T., Shen S. G., Drawbridge M., Checkley D. M. & Tresguerres M., 2021. Ion-transporting capacity and aerobic respiration of larval white seabass (Atractoscion nobilis) may be resilient to ocean acidification conditions. Science of The Total Environment: 148285. doi: 10.1016/j.scitotenv.2021.148285. Article.

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