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

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 mu atm) and elevated pCO(2) (1831 +/- 105 mu atm) until five days post-fertilization (dpf). Skin ionocytes were identified by immunodetection of the Na+/K+-ATPase (NKA) enzyme. Larvae exposed to elevated pCO(2) 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 O-2 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 and 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 pCO(2) of similar to 1200 mu atm 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 pCO(2). (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that exposure to elevated pCO2 conditions does not significantly affect the ionoregulatory capacity or energy consumption of larval white seabass. Even when parents were exposed to high pCO2 for an extended period prior to the experiment, the larvae did not show significant differences. Future research should further investigate the natural resilience of larval white seabass to ocean acidification and its potential mechanisms.