Effect of temperature on an alga-grazer trophic transfer: A dual stable isotope (C-13, N-15) labeling experiment

摘要

In this study, we examined the impact of temperature on the carbon and nitrogen trophic transfers from a macroalga to a macro-grazer by the use of dual C-13- and N-15-labeling. Using an experimental approach in mesocosms, individuals of the urchin Psammechinus miliaris were maintained for 1month at 17 degrees C (mean summer temperature in the Bay of Brest) and at 20 degrees C (maximum summer temperature) and fed with C-13- and N-15-labeled Solieria chordalis. The results showed that the urchins' C-13 uptake was 0.30 mu g(13)Cg dry weight (DW)(-1) at 17 degrees C and 0.14 mu g(13)Cg DW-1 at 20 degrees C at the end of the experiment. The lower uptake at the higher temperature may be attributed to a decrease in metabolic activity at 20 degrees C, involving lower feeding and/or respiration rates. Conversely, no significant effect of temperature was detected on N-15 uptake. At the end of the experiment, the urchins' N-15 uptake was 0.04 mu g(15)Ng DW-1 at 17 degrees C and 0.03 mu g(15)Ng DW-1 at 20 degrees C. This suggests that temperature may affect carbon and nitrogen trophic fluxes differently. The use of dual isotope labeling offers interesting prospects and needs to be further extended in order to better understand trophic interactions in marine communities and the consequences of current environmental changes, such as global warming.