Preliminary Report of Impacts of the 2011 Earthquake and Tsunami and Subsequent Events on Macrobenthic Community in a Shallow Brackish Lagoon in Sendai Bay, Japan
- 32 Downloads
We have been monitoring the spatio-temporal change of macrobenthic community inhabiting soft sediment in Gamo Lagoon which is located on the north side of the Nanakita River Estuary in Sendai Bay, Japan since 2011 earthquake and tsunami disturbance. Unstable condition of estuary topography has been observed to continue until 2017. Just after the disturbance, topography was catastrophically damaged, and macrobenthic community was almost all disappeared by flowing outward and/or being buried in soft sediments caused by tsunami. Soon after that, some opportunistic polychaetes and amphipods were observed to appear, and they sharply increased their population. The secondary series of disturbance, namely river mouth closing and typhoon-derived floods occurred, the area lasted completely in freshwater condition, and that following drastic decline in density again. Adding to these initial sudden changes within a year, successive events and serious diurnal hypoxia in summer were observed every year from 2012 on. Dominant species consisted of firstly small polychaetes and amphipods and later adding bivalves repeatedly appear and disappear during the period. Furthermore, the extraordinary intense deluge occurred in 2015 and the second tsunami arrived in the estuary following Fukushima Earthquake in 2016. The collapse of the balance of the sediment dynamics is suggested to be the worst and major cause which drove the estuary to an unstable environment and macrobenthos community continued to be vulnerable until 2017. Not only natural disturbances but continuous anthropogenic disturbances such as reconstruction of seawalls and dikes have been carried out around the estuary since 2011.
KeywordsTsunami Disturbance Lagoon Topography Macrobenthos Community structure Great East Japan Earthquake
This study was supported by a grant from the Tohoku Ecosystem-Associated Marine Sciences (TEAMS) research program of the Ministry of Education, Culture, Sports, Science and Technology (MEXT). We are grateful to members of the Laboratory of Biological Oceanography, Graduate School of Agricultural Science, Tohoku University, for their cooperation and assistance during field observations. This study was partially funded by a research grant from the Research Institute of Marine Invertebrates Foundation awarded to Tomohiko Kondoh and from Ministry of Education, Science, Sports and Culture of Japan (15K07540, 18K05777) to Waka Sato-Okoshi.
- Abe H, Kobayashi G, Sato-Okoshi W (2016) Ecological impacts of earthquake and tsunami and the following succession on the subtidal macrobenthic community in Onagawa Bay, northeastern Japan, with special reference to the dominant taxon, polychaetes. In: Nakashizuka T, Urabe J (eds) Ecological impacts of tsunamis on coastal ecosystems: lessons from the Great East Japan Earthquake, Ecological research monographs. Springer, Tokyo, pp 59–84Google Scholar
- Dean H (2008) The use of polychaetes (Annelida) as indicator species of marine pollution: a review. Rev Biol Trop 56:11–38Google Scholar
- Gray JS (1974) Animal–sediment relationships. Oceanogr Mar Biol Annu Rev 12:223–261Google Scholar
- Hunsigi G, Yekkeli N, Perumal L, Thippannavar M (2006) Effects of 2004 tsunami on marine ecosystems—a perspective from the concept of disturbance. Curr Sci 90:772–773Google Scholar
- Kanaya G, Maki H, Suzuki T, Sato-Okoshi W, Kikuchi E (2014) Tsunami-induced changes in a shallow brackish lagoon ecosystem (Gamo Lagoon) in Sendai Bay, Japan. Glob Environ Res 18:35–46Google Scholar
- Kanaya G, Suzuki T, Kanou K, Kondoh T, Sato-Okoshi W, Kikuchi E (2016) Ecological consequences of the 2011 tsunami and subsequent disturbance events in a shallow brackish lagoon in Sendai Bay, Japan. In: Nakashizuka T, Urabe J (eds) Ecological impacts of tsunamis on coastal ecosystems: lessons from the Great East Japan Earthquake, Ecological research monographs. Springer, Tokyo, pp 85–104Google Scholar
- Kanaya G, Suzuki T, Kinoshita K, Matsumasa M, Yamada K, Seike K, Okoshi K, Miura O, Nakai S, Sato-Okoshi W, Kikuchi E (2017) Disaster- induced changes in coastal wetlands and soft-bottom habitats: an overview of the impacts of the 2011 tsunami and Great East Japan Earthquake. Biol Int SI 36:62–80Google Scholar
- Kondoh T, 2017. Macrobenthic community dynamics and life-history strategies of each dominant species in Gamo Lagoon (Miyagi Pref., Japan) after the disturbance of 2011 earthquake and tsunami. Doctor thesis Tohoku University Sendai, 162pp (in Japanese)Google Scholar
- Kondoh T, Sato-Okoshi W (2016) Recoveries of the tidal flat ecosystems after the 2011 earthquake and tsunami. In: Kogure K, Hirose M, Kitazato H, Kijima A (eds) Marine ecosystems after Great East Japan Earthquake in 2011. Tokai University Press, Hiratsuka, pp 75–76Google Scholar
- Nakayama G (2017) Spatio-temporal change of macrobenthic community inhabiting Nanakita River Estuary, Miyagi after the Great East Japan Earthquake and tsunami disturbance. Master thesis, Tohoku University, Sendai, Japan, 61pp (in Japanese)Google Scholar
- Rhoads DC (1974) Organisms–sediment relation on the muddy sea floor. Oceanogr Mar Biol Annu Rev 12:263–300Google Scholar