Journal Article

Stable isotope and fatty acid variation of a planktivorous fish among and within large lakes

Axenrot, Thomas, Kalejs, Nicholas I., Ogonowski, Martin, Sandström, Alfred, Höök, Tomas O.

2024

Overview

Aquatic food webs are spatially complex, potentially contributing to intraspecific variability in production pathway reliance of intermediate trophic level consumers. Variation in trophic reliance may be described by well-established trophic indicators, like stable isotope ratios (δ 13 C, δ 15 N), along with emerging trophic indicators, such as fatty acid composition. We evaluated stable isotope ratios and fatty acid profiles of European smelt ( Osmerus eperlanus ) among and within distinct regions of three large Swedish lakes (Hjälmaren, Mälaren, Vättern) which differed in trophic status. We expected that smelts in more oligotrophic lakes and regions would be characterized by distinct stable isotope signatures and fatty acid profiles, with particularly high polyunsaturated fatty acid (PUFA) relative levels. However, we acknowledge that frequent movement of smelts among regions may serve to spatially integrate their diet and lead to limited within-lake variation in stable isotope ratios and fatty acid composition. As expected, in comparison with more productive lakes (i.e., Hjälmaren and Mälaren), smelts from ultra-oligotrophic Vättern were characterized by low δ 15 N, high δ 13 C and high percent of a dominant PUFA, docosahexaenoic acid (DHA). Smelts from different regions of the morphometrically complex Mälaren displayed differential stable isotope ratios and fatty acid relative concentrations, which were consistent with within-lake differences in productivity and water residence times, suggesting that smelts in this lake forage locally within distinct regions. Finally, at the individual smelt level there were particularly strong and consistent associations between a well-established trophic indicator (δ 13 C) and percent DHA, suggesting that the relative concentration of this fatty acid may be a useful additional trophic indicator for smelt.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Analysis / Animals / Biology and Life Sciences / Carbon 13 / Carbon Isotopes - analysis / Composition / Consumers / Cyanobacteria / Diet / Docosahexaenoic acid / Earth Sciences / Ecology / Ecology and Environmental Sciences / Ekologi / Evaluation / Fatty acid composition / Fatty acids / Fatty Acids - analysis / Fatty Acids - metabolism / Fertilizers / Fish / Fish and Aquacultural Science / Fishes - metabolism / Fisk- och akvakulturforskning / Food Chain / Food chains / Food webs / Indicators / Influence / Isotope ratios / Isotopes / Lakes / Medicine and Health Sciences / Nitrogen / Nitrogen Isotopes - analysis / Oligotrophic lakes / Omega-3 fatty acids / Physical Sciences / Plankton / Polyunsaturated fatty acids / Ratios / Stable isotopes / Sweden / Trophic levels / Trophic status / Unsaturated fatty acids / Variation