2025/12/08 by Tomasz Brzeziński, Maciej J. Bojanowski, Magdalena Radzikowska · 1 voice
Environmental Science · Earth and Planetary Sciences · #Isotope Analysis in Ecology #Aquatic Ecosystems and Phytoplankton Dynamics #Marine and coastal ecosystems
paper · pdf · doi:10.1007/s00442-025-05844-8
openalex created_date 2025/12/08 · openalex publication_date 2025/12/08 · openalex updated_date 2026/07/23
Abstract The analysis of stable isotopes of carbon and nitrogen is widely used in ecological investigations. However, sources of variation in isotope ratios of animals are far from being identified, which may bias the interpretation of the results. It has been suggested that stress is a factor that affects isotope ratios and trophic enrichment in animal bodies. Here, we tested the hypothesis that stress due to exposure to a predation threat affects metabolic processes that ultimately result in altered isotope composition of threatened prey. We found that both the nitrogen isotope composition (δ 15 N) and trophic enrichment in 15 N isotope (Δ 15 N) were affected by threat induced by planktivorous fish in two species of the keystone freshwater pelagic herbivore Daphnia : D. magna and D. pulex . The two species differed from each other with regard to isotope ratios. Despite this, with increasing perceived risk of predation, the δ 15 N decreased in both species and, as a consequence, individuals of the two species were depleted in 15 N with respect to their conspecifics not exposed to predation. We have not found evidence that the carbon isotope ratio (δ 13 C) was affected by the predation threat. The eco-physiological responses underlying the induction of antipredatory defences may be responsible for the observed pattern. The effect of predation on the nitrogen isotope ratio (δ 15 N and Δ 15 N) of consumers should be accounted for when using the analysis of stable isotopes in ecological investigations. Moreover, it could be applied to the fossil record to identify the introduction or removal of planktivorous predators in the paleoenvironment.