Turnover of carbon and nitrogen during growth of larval krill, Euphausia superba Dana: a stable isotope approach

• Published in: Journal of experimental marine biology and ecology 1997-05, Vol.212 (2), p.259-275
• Main Authors: Frazer, Thomas K., Ross, Robin M., Quetin, Langdon B., Montoya, Joseph P.
• Format: Article
• Language: English
• Subjects: Euphausia superba; Marine; Metabolism; Stable isotopes; Temperature
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/S0022-0981(96)02740-2

Using natural abundances of stable isotopes ( δ 13C and δ 15N) as tracers, carbon and nitrogen turnover rates were determined for larval krill, Euphausia superba Dana, maintained in the laboratory. Experimental populations of larvae were reared at +1.5°C and −1.5°C on foods of known isotopic composition and subsampled weekly (8–10 weeks) for a determination of wet weight and isotopic composition. Metabolic turnover of carbon and nitrogen, manifested as temporal shifts in δ 13C and δ 15N, was tied closely to temperature. Larval krill reared at +1.5°C had replaced 22–29% of their original body carbon at the conclusion of the experiment, but only 13–22% of their original body nitrogen. Larvae reared at −1.5°C exhibited little evidence of carbon turnover and replaced less than 6% of their original body nitrogen. These are the first simultaneous, coupled measurements of long-term carbon and nitrogen turnover for any marine animal, and provide an essential calibration for the interpretation of stable isotope ratios in animals collected from the field. In addition to the feeding experiments, animals were starved for 2 months at +1.5°C and −1.5°C. Starved krill exhibited little isotopic change. This finding suggests that starvation cannot account for large temporal variations observed in the isotopic composition of larval krill collected from the field.