Unusual patterns in 15 N blood values after a diet switch in red knot shorebirds

• Published in: Isotopes in Environmental and Health Studies
• Main Authors: Dietz, Maurine W., Piersma, Theunis, Dekinga, Anne, Korthals, Harry, Klaassen, Marcel
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: blood cells; diet switch; discrimination factor; nitrogen-15; plasma; regression model; shorebirds; turnover rate; BIVALVE MACOMA-BALTHICA; STABLE-ISOTOPE RATIOS; LABORATORY EXPERIMENTS; CALIDRIS-CANUTUS; TISSUE TURNOVER; ANIMAL ECOLOGY; METABOLIC-RATE; TROPHIC SHIFT; SOFT PARTS; WADDEN SEA; Calidris canutus; Red Knot
• Online Access: https://hdl.handle.net/11370/73ef6578-da90-4898-bc59-dbce4a8e426e; https://research.rug.nl/en/publications/73ef6578-da90-4898-bc59-dbce4a8e426e; https://doi.org/10.1080/10256016.2013.776045

When a diet switch results in a change in dietary isotopic values, isotope ratios of the consumer's tissues will change until a new equilibrium is reached. This change is generally best described by an exponential decay curve. Indeed, after a diet switch in captive red knot shorebirds (Calidris canutus islandica), the depletion of C-13 in both blood cells and plasma followed an exponential decay curve. Surprisingly, the diet switch with a dietary N-15/N-14 ratio (N-15) change from 11.4 to 8.8 parts per thousand had little effect on N-15 in the same tissues. The diet-plasma and diet-cellular discrimination factors of N-15 with the initial diet were very low (0.5 and 0.2 parts per thousand, respectively). N-15 in blood cells and plasma decreased linearly with increasing body mass, explaining about 40 % of the variation in N-15. N-15 in plasma also decreased with increasing body-mass change (r(2)=.07). This suggests that the unusual variation in N-15 with time after the diet switch was due to interferences with simultaneous changes in body-protein turnover.