Importance of phlorotannin content and C : N ratio of Laminaria hyperborea in determining its palatability as food for consumers

Abstract

The importance of the tissue C : N ratio and the content of phlorotannins for the suitability of kelp, Laminaria hyperborea, as food for consumers was tested. Laminas from kelp were sampled in winter. In the laboratory, the kelp was experimentally degraded for 3, 14 and 44 days by kelp-associated bacterial communities under aerobic conditions. The kelp C : N ratio and phlorotannin contents decreased with degradation. The kelp was fed to the kelp-associated amphipods Ampithoe rubricata and Gammarus locusta in no-choice feeding experiments. The growth of amphipods was higher on kelp that was not degraded or degraded for short periods than on kelp degraded for long periods. The results show that the content of phlorotannins in L. hyperborea lamina is of little importance for their suitability as food. An earlier study using kelp with a high C : N ratio showed increased amphipod growth after long degradation and the results from both studies suggest that the C : N ratio of kelp varies greatly with season and the degree of degradation and is important for their suitability as food. Kelp is only palatable when the C : N ratio is not too high or too low.

Keywords:

• amphipod
• Ampithoe rubricata
• bacterial degradation
• C : N feeding experiments
• Gammarus locusta
• kelp forest
• Laminaria hyperborea
• phlorotannins

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgments

This study formed part of a project to investigate the Norwegian kelp forest ecosystem. The project received financial support from the Research Council of Norway. We are grateful to Dr Mohamed Abdullah for advice on the phlorotannin analysis, to Sissel Brubak for assisting us with carrying them out, and to Hartvig Christie for corrections to the manuscript. We are also grateful to Anne Lise Bekken for help with feeding the animals.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark