Past Sea Creation Business

As a result of a preliminary survey conducted at the end of fiscal 2007, the seabed in front of Yamashita Park was found to be about 30 m offshore from the quay and 3 m to 5 m deep from the seabed.
In fiscal 2008, we believe that it is important to enhance the water purification capacity of the sea, and physically separated by underwater screens to suppress the inflow of red tides and muddy water due to rainfall, which tend to drift near the sea surface, and examined the effects of water purification by living creatures. In addition, since the Yamashita　Koen-mae Sea area was decided to become a swim venue for the 2009 Yokohama International Triathlon Tournament in August 2009, the sea where you can swim was also important.

• Transparency Results

Transparency in front of Yamashita Park. There is no difference at any point until about three months have passed since the installation of the water purification experiment facility, but there is no difference at any point.
After three months, you can see that St.1-2 is more transparent than St.2 and St.3.
This means that many filtration bivalves and other organisms grow on underwater screens and anchors, functioning as a base for living organisms, such as transparency, etc.
It was found that it would contribute to the improvement of the marine environment. Since St.1 has a water depth of about 3m, it can be seen that the lower value comes out due to the winding of the bottom mud.

• Results of bottom quality survey

The revetment in front of the Yamashita Park was masonry, and the surface was found to be attached to oysters, wisteria, and mussels.
Under the seawall, a shell bed with shells such as oysters and mussels that had fallen off the seawall was formed.
As the water depth increased, it became a reduced seabed with increased organic pollution, containing a lot of silt and clay.
From this, it is thought that it is limited to living organisms such as sulfuric acid reduction bacteria that can inhabit even if they are anobic in summer.

• Seabed in front of Yamashita Park

In fiscal 2008, we were able to understand the effect of partitioning with a screen as a pilot experiment in front of Nippon Maru Dock and Yamashita Park.
As a result, the effect of mitigating the effects of red tide and turbid water, reducing the number of fecal coliform bacteria and improving transparency through biological purification functions were obtained.
In fiscal 2009, we conducted experiments for practical use in the waters near Yamashita Park. In addition, many citizens visited in front of Yamashita Park, and since the 2009 Yokohama International Triathlon Tournament was also scheduled, we actively provided information and other public information to raise public interest.

• Results of water quality survey

In both illuminance and transparency, the deeper the water, the lower the water. This may include creatures that live in the Asanami area, creatures that live on the screen, and the physical control effect of the screen itself.
Especially in the Asanami area (near st1), there are many creatures such as mussels attached to the seawall in front of Yamashita Park, which is considered to have water purification capacity.

• Experimental results to enhance purification capacity

The base for living organisms was installed on July 27, 2009, and the transition status (September 4, 2009) from the state where there were no attached organisms was confirmed by visual observation.

• Materials used

From this experiment, it is thought that the living base has led to the improvement of the habitat. We believe that sand covering has been effective with an increase in living things.
In addition, it was thought that a lot of adhering organisms could be obtained by installing them in a place where the water depth was shallow and the amount of dissolved oxygen could be secured.
With regard to materials, it was not possible to judge superiority only by this experiment.

・About the first round-table conference (March 18, 2010)
・About the 2nd round-table conference (July 25, 2010)

As a result of partial purification experiments conducted in Yamashita　Koen-mae and other areas, it was found that in order to further improve the water quality of Yokohama Port, it is important to create a sea that utilizes the purification capacity of marine organisms.
In order to promote the creation of a sea with a rich purification capacity that can be familiar to citizens, grasp the current situation of the city coast, select candidate sites to promote sea purification, and sea areas at candidate sites We examined purification methods suitable for the situation.