Oita University - Kagoshima Bay

Restoration Project

Oita University - Kagoshima Bay

Restoration Objective:

The objective of this study is to develop environmentally oriented base materials for seaweed beds with a low environmental load using volcanic ash and several recycled materials from industrial waste.

Cause Of Decline:

Seaweed beds are communities consisting of large benthic plants (seaweed/seagrass), and they form rich underwater forests. These forests play an important role in the ecosystem of the coastal area, serving as nursery grounds for fish and shellfish, and include egg-laying sites and feeding grounds [1,2,3]. However, they have been remarkably reduced in Japan by climate change or human activity.

Key Reasons For Decline:

Multiple

Scientific Paper

Development of environment-oriented base materials for seaweed beds by recycled materials

Yamamoto, K., Negami, T., Mizoguchi, N., Hira, M., & Tsurunari, Y. (2023).https://link.springer.com/article/10.1007/s10163-023-01786-6

Organisation:

Oita University

Site Observations:

Observation Date

1st May 2013 – 1st Jul 2017

Action Summary:

An artificial substrate structure was produced in a 35 L concrete mixer using volcanic ash (29.4%), recycled gypsum (23.5%), water (14.7%), scrap ceramics (17.6%), and cement (14.7%), moulded into a disc-shaped structure (40 cm diameter, ~14 cm height, ~23 kg), demoulded after approximately 3 days, cured for approximately 28 days, and then placed in the sea for natural seaweed colonisation.

Lessons Learned:

Iron powder applied to the substrate surface was more effective for promoting seaweed rooting and growth than other treatments, while surface roughness had little observable effect due to the attachment of barnacles and shellfishes over time. Cement additions of approximately 11–13% were considered most suitable, as higher amounts could create overly alkaline conditions unsuitable for living organisms, while lower amounts resulted in structures that were more easily broken under wave action.

Project Outcomes:

The results of the long-term monitoring show that the developed base materials containing iron powder on the surface were effective for the rooting and growth of seaweed compared with other specimens and the normal type of base material that contains a lot of cement.

Area of Restoration (Ha)

0.00001

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Presence / Absence of Kelp

Observation Date

1st May 2013 – 1st Jul 2017

Action Summary:

An artificial substrate structure was produced in a 35 L concrete mixer using volcanic ash (30.8%), recycled gypsum (24.6%), water (13.8%), scrap ceramics (18.5%), cement (12.3%), and a 300 g surface covering of iron powder, moulded into a disc-shaped structure (40 cm diameter, ~14 cm height, ~23 kg), demoulded after approximately 3 days, cured for approximately 28 days, and then placed in the sea for natural seaweed colonisation.

Lessons Learned:

Iron powder applied to the substrate surface was more effective for promoting seaweed rooting and growth than other treatments, while surface roughness had little observable effect due to the attachment of barnacles and shellfishes over time. Cement additions of approximately 11–13% were considered most suitable, as higher amounts could create overly alkaline conditions unsuitable for living organisms, while lower amounts resulted in structures that were more easily broken under wave action.

Project Outcomes:

The results of the long-term monitoring show that the developed base materials containing iron powder on the surface were effective for the rooting and growth of seaweed compared with other specimens and the normal type of base material that contains a lot of cement.

Area of Restoration (Ha)

0.00001

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Presence / Absence of Kelp

Observation Date

1st May 2013 – 1st Jul 2017

Action Summary:

An artificial substrate structure was produced in a 35 L concrete mixer using volcanic ash (35.1%), recycled gypsum (24.6%), water (14.0%), scrap ceramics (17.5%), and cement (8.8%), moulded into a disc-shaped structure (40 cm diameter, ~14 cm height, ~23 kg), demoulded after approximately 3 days, cured for approximately 28 days, and then placed in the sea for natural seaweed colonisation.

Lessons Learned:

Iron powder applied to the substrate surface was more effective for promoting seaweed rooting and growth than other treatments, while surface roughness had little observable effect due to the attachment of barnacles and shellfishes over time. Cement additions of approximately 11–13% were considered most suitable, as higher amounts could create overly alkaline conditions unsuitable for living organisms, while lower amounts resulted in structures that were more easily broken under wave action.

Project Outcomes:

The results of the long-term monitoring show that the developed base materials containing iron powder on the surface were effective for the rooting and growth of seaweed compared with other specimens and the normal type of base material that contains a lot of cement.

Area of Restoration (Ha)

0.00001

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Presence / Absence of Kelp

Observation Date

1st May 2013 – 1st Jul 2017

Action Summary:

An artificial substrate structure was produced in a 35 L concrete mixer using volcanic ash (30.8%), recycled gypsum (24.6%), water (13.8%), scrap ceramics (18.5%), cement (12.3%), and 300 g of iron powder mixed into half of the structure, moulded into a disc-shaped structure (40 cm diameter, ~14 cm height, ~23 kg), demoulded after approximately 3 days, cured for approximately 28 days, and then placed in the sea for natural seaweed colonisation.

Lessons Learned:

Iron powder applied to the substrate surface was more effective for promoting seaweed rooting and growth than other treatments, while surface roughness had little observable effect due to the attachment of barnacles and shellfishes over time. Cement additions of approximately 11–13% were considered most suitable, as higher amounts could create overly alkaline conditions unsuitable for living organisms, while lower amounts resulted in structures that were more easily broken under wave action.

Project Outcomes:

The results of the long-term monitoring show that the developed base materials containing iron powder on the surface were effective for the rooting and growth of seaweed compared with other specimens and the normal type of base material that contains a lot of cement.

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Presence / Absence of Kelp

Observation Date

1st May 2013 – 1st Jul 2017

Action Summary:

An artificial substrate structure was produced in a 35 L concrete mixer using volcanic ash (26.8%), recycled gypsum (21.5%), water (12.1%), scrap ceramics (16.1%), cement (13.4%), and shells (10.1%), moulded into a disc-shaped structure (40 cm diameter, ~14 cm height, ~23 kg), demoulded after approximately 3 days, cured for approximately 28 days, and then placed in the sea for natural seaweed colonisation.

Lessons Learned:

Iron powder applied to the substrate surface was more effective for promoting seaweed rooting and growth than other treatments, while surface roughness had little observable effect due to the attachment of barnacles and shellfishes over time. Cement additions of approximately 11–13% were considered most suitable, as higher amounts could create overly alkaline conditions unsuitable for living organisms, while lower amounts resulted in structures that were more easily broken under wave action.

Project Outcomes:

The results of the long-term monitoring show that the developed base materials containing iron powder on the surface were effective for the rooting and growth of seaweed compared with other specimens and the normal type of base material that contains a lot of cement.

Area of Restoration (Ha)

0.00001

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Presence / Absence of Kelp

Observation Date

1st May 2013 – 1st Jul 2017

Action Summary:

An artificial substrate structure was produced in a 35 L concrete mixer using volcanic ash (29.9%), recycled gypsum (23.9%), water (13.4%), scrap ceramics (17.9%), cement (11.9%), and iron powder (3.0%), moulded into a disc-shaped structure (40 cm diameter, ~14 cm height, ~23 kg), demoulded after approximately 3 days, cured for approximately 28 days, and then placed in the sea for natural seaweed colonisation.

Lessons Learned:

Iron powder applied to the substrate surface was more effective for promoting seaweed rooting and growth than other treatments, while surface roughness had little observable effect due to the attachment of barnacles and shellfishes over time. Cement additions of approximately 11–13% were considered most suitable, as higher amounts could create overly alkaline conditions unsuitable for living organisms, while lower amounts resulted in structures that were more easily broken under wave action.

Project Outcomes:

The results of the long-term monitoring show that the developed base materials containing iron powder on the surface were effective for the rooting and growth of seaweed compared with other specimens and the normal type of base material that contains a lot of cement.

Area of Restoration (Ha)

0.00001

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Presence / Absence of Kelp

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