Dietary macronutrients influence super(13)C and super(15)N signatures of pinnipeds: Captive feeding studies with harbor seals (Phoca vitulina)

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Molecular & integrative physiology, 2006-01, Vol.143 (4), p.469-478
• Main Authors: Zhao, Liying, Schell, Donald M, Castellini, Michael A
• Format: Article
• Language: English
• Subjects: Marine; Phoca vitulina; Pinnipedia
• ISSN: 1095-6433
• DOI: 10.1016/j.cbpa.2005.12.032

Metabolic effects of dietary macronutrients on diet-tissue isotopic discrimination factors were investigated in harbor seals. Three seals were fed either high fat/low protein herring (H), or low fat/high protein pollock (P), and switched to the alternative every 4 months. This allowed each seal to be subjected to two dietary treatments in each of three metabolically defined seasons (breeding from May to September, molting from September to January, and late winter/early spring period from January to May) over a 2 year cycle, and function as its internal control regardless of physiological changes over season. One seal was fed a constant equal mix of H and P over the entire trial. Up to 1ppt differences in serum delta super(15)N values of one seal fed alternatively on H and P were observed. Progressively more enriched serum delta super(15)N values as diet switching from H to P might link to changes in seal digestive physiology and protein metabolism in response to very high protein intake on P diet. These findings demonstrate that dietary macronutrients of prey species and protein intake level of consumers also play important roles in shaping isotopic patterns of a consumer's tissues, and thus influence accurate data interpretation of stable isotope techniques in ecological applications.