Abstract
We examined structural changes in the molluscan community for ten years (2001–2010) before and five years (2011–2015) after the 2011 Great East Japan Earthquake and subsequent tsunami around Matsushima Bay, Miyagi Prefecture, northeastern Japan. Before the earthquake and tsunami, Ruditapes philippinarum, Macoma incongrua, Pillucina pisidium, and Batillaria cumingii were dominant, and an alien predator Laguncula pulchella appeared in 2002 and increased in number. After the tsunami, R. philippinarum and M. incongrua populations quickly recovered in 2012, but P. pisidium and B. cumingii populations did not recover until 2015. By contrast, Musculista senhousia, Mya arenaria, Retusa sp., and Solen strictus were found in low densities before the tsunami, but they rapidly increased in abundance/number over five years after the tsunami. These results suggest that the molluscan community on the Tona Coast was drastically changed by the earthquake and tsunami, and some species mainly inhabiting the intertidal—subtidal zone may have increased in number because of land subsidence. We also emphasize that the seawall delayed recovery of the intertidal community after the earthquake and tsunami.
Highlights
IntroductionBenthic animals on tidal flats are frequently damaged by natural and artificial catastrophic events, such as heavy sedimentation [1], storms [2], tsunamis [3,4,5], hypoxia [6,7,8], oil spills [9], dredging [10], introduced species [11,12,13,14], and reclamation [15], and full recovery from these events can take a minimum of 15–25 years [16]
In 2001, Ruditapes philippinarum, Macoma incongrua, Pillucina pisidium and Batillaria cumingii were collected in large numbers (Fig 2A), and R. philippinarum and B. cumingii occupied more than 80% of the community (Fig 2B)
Since many benthic organisms were reworked from the sediment and washed away by the tsunami, occasionally transported larvae could colonize the nearly barren habitat without intense competition with the other species. This inference is supported by the observed dominance of small individuals of M. senhousia and M. arenaria in 2011 immediately (2 months) after the tsunami on the Tona Coast [27], suggesting that opportunistic species were able to colonize after the tsunami
Summary
Benthic animals on tidal flats are frequently damaged by natural and artificial catastrophic events, such as heavy sedimentation [1], storms [2], tsunamis [3,4,5], hypoxia [6,7,8], oil spills [9], dredging [10], introduced species [11,12,13,14], and reclamation [15], and full recovery from these events can take a minimum of 15–25 years [16]. In order to examine the ecological impacts and recovery trajectory from these catastrophic events, long-term datasets from at least 15 years before and after the events are necessary. In most cases, preevent data are scarce or absent, so we cannot correctly demonstrate the influence of such catastrophic events on benthic animals.
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