[Press Release] “Herring-derived nutrients”: evidence from historical delta15N records of kelps

Kelp (Saccharina spp.) beds along the west coast of Hokkaido (Japan Sea) were used to be commercially exploited, but are currently decreasing. This is believed to be due to the present nutrient limitations. To date, however, the mechanisms that caused the nutrient limitations are still unclear because of a lack of scientific data on historical nutrient changes in this region. Dr. Takanori Kuribayashi (he received a doctoral degree as an adult student of our school), Lecturer Tsuyoshi Abe (Hokkaido University Museum), and Specially-appointed Prof. Shigeru Montani (Division of Biosphere Science) hypothesized that nutrients for Saccharina spp. beds may have been derived from spawning herrings (Clupea pallasii), which were previously caught 500–1000 times more than now. To test this hypothesis, they focused on stable nitrogen isotope ratios (delta¹⁵N) of 100- to 135-year-old Saccharina specimens preserved at Hokkaido University Museum. Delta¹⁵N values of old Saccharina specimens in this region were in the range of 10‰, which is significantly higher than the current specimens (3–7‰). This high delta¹⁵N supports the “herring-derived nutrients” hypothesis.

This research outcome is published in PLOS ONE.

Please visit links below to view the press release (Japanese ver. only).
Research Press Release (PDF)