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Thermal constraints on the respiration and excretion rates of krill, Euphausia hanseni and Nematoscelis megalops, in the northern Benguela upwelling system off Namibia
Werner, T.; Huenerlage, K.; Verheye, H.; Buchholz, F. (2012). Thermal constraints on the respiration and excretion rates of krill, Euphausia hanseni and Nematoscelis megalops, in the northern Benguela upwelling system off Namibia. Afr. J. Mar. Sci. 34(3): 391-399. hdl.handle.net/10.2989/1814232X.2012.689620
In: African Journal of Marine Science. NISC: Grahamstown. ISSN 1814-232X , more
Peer reviewed article  

Available in Authors 
    VLIZ: Open Repository 244183 [ OMA ]

Keyword
    Marine
Author keywords
    ammonia excretion, carbon demand, diel vertical migration, O:N ratio, temperature

Authors  Top 
  • Werner, T.
  • Huenerlage, K.
  • Verheye, H.
  • Buchholz, F.

Abstract
    Rates of respiration and ammonia excretion of Euphausia hanseni and Nematoscelis megalops were determined experimentally at four temperatures representative of conditions encountered by these euphausiid species in the northern Benguela upwelling environment. The respiration rate increased from 7.7 µmol O2 h-1 gww -1 at 5 °C to 18.1 µmol O2 h-1 gww -1 at 20 °C in E. hanseni and from 7.0 µmol O2 h-1 gww -1 (5 °C) to 23.4 µmol O2 h-1 gww -1 (20 °C) in N. megalops. The impact of temperature on oxygen uptake of the two species differed significantly. Nematoscelis megalops showed thermal adaptations to temperatures between 5 °C and 10 °C (Q10 = 1.9) and metabolic constraint was evident at higher temperatures (Q10 = 2.6). In contrast, E. hanseni showed adaptations to temperatures of 10–20 °C (Q10 = 1.5) and experienced metabolic depression below 10 °C (Q10 = 2.6). Proteins were predominantly metabolised by E. hanseni in contrast to lipids by N. megalops. Carbon demand of N. megalops between 5 and 15 °C was lower than in E. hanseni versus equal food requirements at 20 °C. It is concluded that the two species display different physiological adaptations, based on their respective temperature adaptations, which are mirrored in their differential vertical positioning in the water column.

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