The Ecosystems Monitoring Survey of the Pacific Coastal Areas of the Tohoku Region in FY2014

Summary

### 1. Purpose of the project

The earthquake and ensuing tsunami that occurred on March 11, 2011 off the Pacific coast of Japan’s Tohoku region (hereinafter “the Great East Japan Earthquake” or “the disaster”) had an enormous impact on the natural environment, people’s lives, and the social environment along the Pacific coast of the Tohoku region and elsewhere. The purpose of this project was to survey tidal flats, seagrass beds, seaweed beds, and seabirds in the coastal areas of the Tohoku region—where the impact of the Great East Japan Earthquake on the natural environment was particularly apparent—and to gauge the impacts of the earthquake and tsunami on the natural environment in the region.

### 2. Results of the project

## (1) Survey of tidal flats

For the tidal flats, the abundance and identification of benthic organisms were recorded through quantitative and qualitative surveys at 16 sites. Some of the species seen well before the disaster still could not be found in some of the sites. However, as a whole, the tidal flat environment had become more stable yearly than it had been immediate aftermath of the disaster, and the number of species at each of the sites has increased and has been recovering, although individual densities were low. It may be understand that recovery of the benthic communities at each of the sites may take a long time.

## (2) Survey of seagrass beds

For the seagrass beds, survey points were set near and off the shore at each of the site (Yamada Bay, Hirota Bay, Mangokuura, and Matsushima Bay), and seagrass species occurring in quadrats and their respective coverage were recorded. Compared to the results of the $ 7^{th} $ National Survey on the Natural Environment (seaweed bed survey), condition of seagrass showed an overall decline, with a low seagrass density at the survey sites with some exceptions. As the exceptions, some of the sites showed signs of seagrass recovery (ex., Matsushima Bay site), although it is very slight. It is necessary to conduct continuous monitoring to keep track of seagrass recovery.

## (3) Survey of seaweed beds

For the seaweed beds, species occurring in quadrats and their respective coverage as well as a line survey were recorded at Yamada Bay, Onagawa Bay, Kitaibaraki City (Izura), and Nakaminato (Oarai). According to the survey result, the overall condition of seaweed communities was recovering, although some of the sites showed the seaweed decline compared to pre-disaster levels. Seaweed community might change according to the condition of the surrounding environment is a point of attention.

## (4) Survey of seabirds

In the seabird survey, on the islands of Kabushima, Hidejima, Sanganjima, and Ashijima, the total number of nests was estimated from the nesting areas and nest densities. The direct impact of the disaster could not be determined from the survey, but soil runoff, vegetation changes at each of the sites were observed. There is a possibility that soil runoff and vegetation changes could hinder the breeding of seabirds. It is therefore necessary to conduct continuous monitoring of seabirds including the nesting conditions.