The Sea Revives, the Cycle Begins. The Day 'Living Blocks' Were Installed in Kamogawa Fisherina.

Installation of artificial reef blocks at Kamogawa Fisherina.

Kankyo Naisuimen Shigen Kenkyujo Co., Ltd. (Headquarters: Tsuruoka City, Yamagata Prefecture; Representative Director: Yoshi Sato) has completed the underwater installation of 'Organic Blocks,' an environmentally friendly artificial reef, at Kamogawa Fisherina in Kamogawa City, Chiba Prefecture, and has commenced a demonstration experiment.

This demonstration is being advanced with the cooperation of Kamogawa City Fisheries Cooperative, Kamogawa Marine Development Co., Ltd., and KGM Co., Ltd.

Do you know about 'Isoshake'?

In recent years, the disappearance of seaweed beds has been progressing along coastlines throughout Japan. This phenomenon, known as 'isoshake,' causes the loss of seaweed forests that once served as nurseries for fish and shellfish, transforming the coastal and seabed environment into something resembling a desert.

Seaweed forests are like the 'roots' that support the marine food chain, serving as hiding places for juvenile fish and shellfish and as spawning grounds. Their loss means the collapse of the very 'foundation' for marine life. As a result, not only do fish catches decrease and local fisheries decline, but also the function of seaweed to absorb, fix, and circulate carbon in the sea (blue carbon) is lost. This is a quiet and extremely serious crisis that progresses unseen.

According to a survey by the Fisheries Agency, approximately 80% of prefectures nationwide reported a decline in seaweed beds. Various other surveys also report a decreasing trend in Japan's seaweed beds since the 1990s, and the sea off Kamogawa City is no exception.

Not concrete.
Born from nature's bounty, eventually returning to the sea — Organic Blocks.

Organic Blocks (7 hexagonal columns on a pedestal)

This time, with the wish for seaweed bed regeneration, we installed 'Organic Blocks' made from recycled materials into the sea. At first glance, they may look like ordinary concrete blocks, but their contents and roles are significantly different.

Utilizing recycled resources (recycled materials) such as organic components and recycled soil, they are designed with shapes, textures, and structures that make it easy for microorganisms and seaweed to settle. The use of cement is minimized, and over time, they gradually decompose and change, eventually integrating into nature's cycle as sandy components and inorganic nutrients. "After their role is fulfilled, they return to the environment" — this is an artificial structure based on a new concept.

In a prior demonstration in Sakata Port, Yamagata, changes appeared on the surface in about two months, with algae (diatoms) and barnacles settling. By September of the following year, naturally settled oysters (about 80mm) could be observed, and schools of fish such as mejina, ishidai, and horse mackerel were confirmed nearby. Currently, after about two and a half years, a landscape of lush seaweed is spreading. The demonstration of "the sea where living creatures return" is steadily progressing.

Sakata Port Prior Demonstration Results

Attachment of algae and barnacles (51 days after installation) Colonies of white ascidians and initial vegetation (225 days after installation) Natural settlement and community of oysters (371 days after installation) Seaweed sprouts, sea lettuce, etc. (596 days after installation)

Fish aggregation effect: High density of mejina, ishidai, horse mackerel, etc., and lush seaweed beds as of February 22, Reiwa 8 (892 days after installation)

Why Kamogawa?

Kamogawa has always been a town where rich nature and fisheries are a source of local pride. While the previous demonstration in Sakata Port, Yamagata Prefecture, was a project within a 'port,' this time it is being conducted in a 'space where people and the sea interact,' a marina visited by tourists.

"Can human use and natural regeneration coexist?" — We seek the answer to this question in the sea of Kamogawa. This demonstration, carried out in collaboration with local fisheries cooperatives, marinas, and researchers who show deep understanding of the initiative, is being advanced in Chiba Prefecture, which is promoting various initiatives for seaweed bed regeneration. It aims to be a regenerative Kamogawa model, with a view to expanding to coastal facilities nationwide.

What will be monitored from now on?

In this demonstration, monitoring will continue from the following perspectives:

• How many types, numbers, and speeds of seaweed and attached organisms settle

• What kind of fish gather (aggregation effect)

• Whether an increase in Aoriika (bigfin reef squid), a natural enemy of harmful fish (e.g., rabbitfish, rudderfish), can be expected

• What effectiveness can be confirmed in the ecosystem compared to ordinary concrete

• How long it takes for the blocks to decompose

• Whether it can establish itself as an ecosystem recovery model

Future Development

Following the demonstration in Sakata Port, Kamogawa is the first step. The 'Organic Block' aims to be deployed in a wide range of applications, including seaweed bed creation, 'isoshake' countermeasures, combination with oyster farming, and coastal ecosystem conservation. We will also proceed with the development of "locally produced and consumed blocks" that utilize local materials and are designed according to the topography and currents of each region. While looking to expand to overseas waters as well as domestically, we aim to realize a coastal environment where people and the sea can coexist for a long time, centered on "circulation, efficiency, and co-creation."

Demonstration Experiment Outline
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