## Ecosystem Monitoring

We monitored the seaweed beds, Zostera beds, seabird breeding sites and benthos living landscape in tidal flats along the Pacific coastal regions from Aomori Prefecture to Chiba Prefecture which are thought to be affected by the earthquake especially.

## Benthos in tidal flats

There are various types of tidal flats depending on the sites and geographical locations and the level of impact differs for each area.

## Sanriku Coast

The disturbance was on a relatively large scale and the benthos landscape has changed vastly together with changes in the shape and submergence of the tidal flats.

## Sendai Bay

Although the disturbance was on a relatively moderate scale, the benthos landscape has changed together with the disappearance and withering of Phragmitetea and deposition of sand on the sea bottom.

## Aomori coast

The disturbance was on a relatively small scale and no changes in the sea-bottom living landscape were observed.

## ●Matsushima Bay

The disturbance at the entrance of the bay was on a relatively moderate scale and the benthos landscape had changed. In the inner bay, the disturbance was on a relatively small scale and the benthos landscape hadn't changed so much.

## Mangokuura

Although the impact of the tsunami was small, the disturbance was on a relatively moderate scale; the previous appearance of the tidal flat at a low tide was lost due to approximately 80 cm land subsidence. The benthos landscape changed with that.

## The east coast of the Boso peninsula

Although the disturbance was on a relatively moderate scale, the benthos landscape changed together with changes in the sea bottom.

## The estuary of Unosumai River, Kamaishi City, Iwate Prefecture (Sanriku coast)

## After the earthquake

In tidal flat areas with brackish water and relatively low salt content, many polychaete such as Tylorrhynchus heterochaetus and crustacean such as Deiratonotus cristatus were observed.

Due to the tsunami, the sandbar disappeared and the estuary opened up directly into the sea with the agricultural land on the left bank being turned into a tidal flat. As a result, organisms that live in brackish waters with relatively higher salt content such as Nuttalliia japonica, Laternula marilina, Ruditapes philippinarum and Mya arenaria oonogai moved in, resulting in changes to the ecosystem.

Left bank of estuary of Unosumai River that has been turned into a new tidal flat

## Seabird breeding sites

Although there was no direct impact on migratory seabirds since the earthquake occurred before they flew here to breed, the land was stripped of its vegetation and litter flowed out into the area together with the flooding caused by the tsunami.

## Kabu Island

## (Hachinohe City, Aomori Prefecture)

The impact on the land slipping due to the tsunami was minor and the proportion of vegetation such as Dactylis glomerata, Poa annua and Brassica napus increased.

Calonectris leucomelas (Hide Island)

## Hide Island (Miyako City, Iwate Prefecture)

Although the area was flooded up to a height of 20-40 meters, no soil runoff due to the tsunami or impact caused by the land stripping were observed.

## Sangan Island

(Kamaishi City, Iwate Prefecture)

The area was flooded up to a height of about 20 meters and landslides shrunk the area where storm petrels could build their nests.

## Ashi Island

(Onagawa Town, Miyagi Prefecture)

The impact of soil runoff due to the tsunami was minor and most of the vegetation and land within the nesting range remained intact.

## Ashi Island, Onagawa Town, Miyagi Prefecture

## Before the earthquake

Ashi Island is the southern tip of the breeding grounds for Cerorhinca monocerata, and Calonectris leucomelas also used to build their nests in the same area.

The tsunami was thought to have reached a height of about 15 meters as it exceeded the height of the saddle in the center of the island (height about 15 meters). However, the land and vegetation remained in most areas and thus the impact on the nest density of the Cerorhinca monocerata was thought to be minor.

Nest area of the Larus crassirostris at the northern end of Ashi Island

## Zostera beds

As Zostera forest are mainly located in the inner bay areas where the force of the tsunami is concentrated, the great disturbance such as disappearance of the sea bed caused by the tsunami was observed.

Phyllospadix iwatensis (Inubosaki)

## Yamada Bay

## Hirota Bay

Before the earthquake, the largest Zostera forest in the Sanriku area was formed here. There was a clear demarcation between Zostera marina in the shallow areas and Zostera caulescens in the deeper areas. However, the ground subsided by about 60-80 cm after the earthquake and the distribution border became indistinguishable.

There was a large population of mixed Zostera caespitosa and Zostera marina before the earthquake. After the earthquake, the northern and central areas of the bay were observed to be just as dense even though the ground subsided by about 40 cm.

## Mangokuura

Zostera was seen from the west coast of Kuroshima Island to about 100 meters out at sea before the earthquake disaster. After the earthquake, the ground subsided by about 90 cm, wiping out large areas of the Zostera population.

## ●Matsushima Bay (Sabusawa Island)

One species of Zostera marina used to grow here before the earthquake disaster. After the earthquake, the ground subsided by about 1 meter, and only a small number at the mouth of the bay remained intact.

Inubosaki

Before the earthquake, cold and warm temperate and cold current algae and seaweed used to grow in this area and no significant changes were seen after the earthquake.

## Otsuchi

Small-scale Zostera beds used to dot the area before the earthquake. After the earthquake, most of it disappeared together with the seabed. Although some Zostera was seen, the coverage was almost 0%.

## Mangokuura, Ishinomaki City, Iwate Prefecture (lagoon)

According to a survey of the west coast of Kuroshima Island carried out near the center of the lagoon in Dec 2006, Zostera was observed to be growing from the coast up to about 100 meters out at sea.

The ground was seen to have subsided by about 0.9 meters, becoming muddy as sludge accumulated. The distribution area of the Zostera was drastically reduced. Zostera population reported in the survey in 2006 was exterminated.

## Seaweed beds

Seaweed beds are mainly located at the mouth of the bay facing the open sea. While there has been some impact due to the sinking of the ground caused by the tsunami, no large changes in the population landscape were observed. Also as this area is mainly used for growing young algae such as Undaria pinnatifida and Laminariaceae bory, the impact on the population was thus thought to be relatively minor.

## Yamada Bay

Before the earthquake, it was a Laminariaceae bed mainly consisted of Laminaria japonica Areschoug and Costaria costata. After the earthquake, Laminaria japonica Areschoug was seen.

## Shizugawa Bay

Japanese kelp (Yamada Bay)

Before the earthquake, the main population seen was Eisenia bicyclis. No major changes in the population landscape were seen immediately after the earthquake but significant growth of Undaria pinnatifida was seen in 2012.

## Onagawa Bay

Before the earthquake, there were almost no large algae species and several varieties of small red algae were seen mostly. After the earthquake, Schizymenia dubyi and Laminaria religiosa were seen mainly in the shallow areas while Undaria pinnatifida and Sargassum horneri were seen mainly in the deeper areas.

## Kitaibaraki City area

Before the earthquake, it was mainly Undaria pinnatifida and Sargassum beds. After the earthquake, it became a mixture of Eisenia bicyclis, Undaria pinnatifida and Sargassum.

## Onagawa Bay, Onagawa Town, Miyagi Prefecture (Minamisanriku)

## Before the earthquake

Originally, the bed consisted of Undaria pinnatifida and Sargassum but is now dominated by several varieties of small red algae dotted with Dictyota dichotoma, a large brown algae (March 2007 survey).

In the shallow areas, a red algae Schizymenia dubyi grows in abundance mixed with a large brown algae, Laminaria religiosa. In the deeper areas, it is mainly dominated by Sargassum horneri and Undaria pinnatifida (August 2012 survey).

*Aerial Photos: Taken by Geospatial Information Authority of Japan