Oxygen concentration in the water boundary layer next to rainbow trout (Oncorhynchus mykiss) embryos is influenced by hypoxia exposure time, metabolic rate, and water flow

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Abstract:

The objective of this study was to examine the influence of hypoxia exposure time, metabolic rate, and water flow rate on the O2 concentration in the boundary layer outside and inside the chorion of rainbow trout (Oncorhynchus mykiss) embryos. Oxygen consumption, growth, and dissolved O2 in the boundary layer were measured at 15, 22, and 29days post fertilization (dpf) from embryos reared in normoxia (O2 concentration at 100% saturation) and chronic hypoxia (>24h, 50% saturation) and exposed to acute hypoxia (30min, 50% saturation). Chronic and acute hypoxia exposure decreased the dissolved O2 in the boundary layer to the same extent at 15 and 22dpf; however, at 29dpf, O2 levels were significantly lower in acute relative to chronic hypoxia. At 29dpf, O2 uptake per individual was significantly lower in embryos exposed to chronic relative to acute hypoxia. In addition, mass-specific O2 uptake in chronic hypoxia-exposed embryos was ~40% less than that of controls but the same as that of acutely exposed embryos. This correlates with reduced growth in embryos exposed to chronic hypoxia. We conclude that boundary layer O2 is lower after 30min of hypoxia compared with 2 weeks of hypoxia simply because embryos exposed to chronic hypoxia grow slower and consume less O2.

Notre étude examine l’influence de la durée de l’exposition à l’hypoxie, du taux métabolique et du taux d’écoulement de l’eau sur la concentration d’oxygène dans la couche limite à l’extérieur et à l’intérieur du chorion des embryons de truites (Oncorhynchus mykiss). Nous avons mesuré la consommation d’oxygène, la croissance et la concentration d’oxygène dissous (DO) dans la couche limite 15, 22 et 29 jours après la fécondation chez des embryons élevés en normoxie ([O2] à 100 % de saturation) ou en hypoxie chronique (>24 h, 50 % de saturation) ou alors exposés à une hypoxie aiguë (30 min, 50 % de saturation). Les hypoxies chroniques et aiguës causent une diminution de DO dans la couche limite de même importance 15 et 22 jours après la fécondation; cependant, 29 jours après la fécondation, les concentrations d’oxygène sont significativement plus basses lors d’une hypoxie aiguë que d’une hypoxie chronique. Vingt-neuf jours après la fécondation, l’absorption d’oxygène par individu est significativement plus faible chez les individus exposés à une hypoxie chronique plutôt qu’à une hypoxie aiguë. De plus, l’absorption d’oxygène spécifique à la masse chez les embryons exposés à une hypoxie chronique est ~40 % inférieure à celle des témoins, mais semblable à celle des embryons ayant subi une exposition aiguë. Cela s’explique par la croissance réduite des embryons exposés à une hypoxie chronique. Nous concluons que la concentration d’oxygène dans la couche limite est plus basse après 30 min d’hypoxie qu’après 2 semaines, parce que les embryons exposés à l’hypoxie chronique croissent plus lentement et consomment moins d’oxygène.

Document Type: Research Article

Publication date: October 1, 2008

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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