Analysis of environmental and microbiological changes in Onagawa Bay immediately after the tsunami of the Great East Japan Earthquake based on sediment cores

Yutaka Okumura, Kenji Kaneko, Hiroto Ota, Hiromitsu Nagasaka, Motoyuki Hara

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

We investigated two sediment cores to understand whether a tsunami in Onagawa Bay, Japan caused environmental changes. The value of δ13C ranged from −21.9‰ to −24.3‰ and of δ15N ranged from 5.1 to 5.9‰. We conclude that the source of the sediment in the present study area was mainly oceanic and not terrestrial. The chlorophyll concentration ranged from 1.8 to 4.0 μg/g ww, and did not vary greatly between surface and bottom layers. We inferred that all layers were deposited after the tsunami. The major phytoplankton taxa in sediments were diatoms from DNA sequencing. The presence of harmful dinoflagellates was minor. The concentrations of several heavy metals decreased slightly after the tsunami. We inferred that heavy metals in sediments were diluted by the tsunami disturbance. The land in Onagawa suffered serious damage, but disturbance of the seabed was much less evident.

Original languageEnglish
Article number111235
JournalMarine Pollution Bulletin
Volume157
DOIs
Publication statusPublished - 2020 Aug

Keywords

  • Algae
  • Environmental sciences
  • Isotope ratios
  • Marine sediments
  • Oceanography
  • Tsunamis

ASJC Scopus subject areas

  • Oceanography
  • Aquatic Science
  • Pollution

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