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Effects of Elevated CO 2 on Yellowfin tuna ( Thunnus albacares ) Early Life Stage Respiration and Ammonia Excretion
Author(s) -
Heuer Rachael M.,
Wang Yadong M.,
Pasparakis Christina,
Scholey Ver,
Margulies Daniel,
Grosell Martin
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.09653
Subject(s) - yellowfin tuna , tuna , biology , excretion , pelagic zone , thunnus , broodstock , population , zoology , fishery , aquaculture , fish <actinopterygii> , biochemistry , demography , sociology
Although the impacts of near‐future projected CO 2 levels on coastal fishes are well‐documented, few studies have addressed impacts to broad‐ranging pelagic fish species which generally live in a more stable environment and therefore may be more impacted by change. The early life stages of pelagic fish may be especially sensitive to CO 2 , since acid‐base regulatory mechanisms are not fully developed. Furthermore, few studies have examined how CO 2 exposure could impact nitrogenous waste excretion in early life stage fish. In the present study, we examined the impacts of near‐future CO 2 on early life stages of the Yellowfin tuna ( Thunnus albacares ). Tuna embryos were obtained from a captive spawning broodstock population of Yellowfin tuna at the IATTC Achotines Laboratory. Tuna were exposed to either control or 1900 matm CO 2 (prediction for year 2300) directly after spawn and through the first 3 days of development as embryos hatched into yolk sac larvae. Metabolic rate, ammonia tissue accumulation, and ammonia excretion were quantified at various timepoints throughout development. Since Rh proteins putatively transport CO 2 in addition to ammonia, samples to assess mRNA expression of Rh proteins were also taken at each developmental timepoint. Exposure to elevated CO 2 did not significantly impact the metabolic rate of developing tuna, however, at the final larval stage, a 22% decrease in metabolic rate was noted. This decline was immediately preceded by a significant increase in ammonia excretion in CO 2 ‐exposed larvae, despite no difference in ammonia tissue accumulation when comparing control and CO 2 ‐exposed larvae. Interestingly, CO 2 ‐exposed larvae exhibited a significant increase in urea accumulation at this timepoint. These data suggest that larvae are producing more nitrogenous waste, but are able to avoid the build‐up of toxic ammonia by maintaining higher levels of ammonia excretion and/or by converting ammonia to urea. Analysis of mRNA expression of Rh proteins is ongoing and may provide a mechanism for this increased nitrogenous waste excretion. These results suggest egg and yolk sac larvae life stages of yellowfin tuna may be equipped with mechanisms to counteract increases in CO 2. This research was made possible by a grant from The Gulf of Mexico Research Initiative. Grant No: SA‐1520. Support or Funding Information This research was made possible by a grant from The Gulf of Mexico Research Initiative. Grant No: SA‐1520.