Biodiversity recovery of a coastal seaweed bed by using the Vivary Unit composed of steelmaking slag, by-product of steel manufacturing

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Description

Intro

NSSMC has developed the Vivary Unit, a fertilizer that supplies iron compound in the seawater, and has installed it on the sea floor where it can promote growth of seaweed. Slag and humus-rich soil, its major components, are recycled materials which are readily sourced at low cost. The first installation was made in 2004 in Mashike Town, Hokkaido, where the seabed desertification had caused a decline in the fishery. By 2014, 42 tons of the Vivary Unit were installed and helped recover 1.3 hectare of seaweed beds, contributing to restoration of biodiversity and revival of the fishery.

Objective of the practice

The Vivary Unit is a fertilizer developed for helping to prevent loss of functioning seaweed beds, a phenomenon known as “sea desertification,” observedin the coasts of various parts of Japan. Focusing on the iron deficiency in the seawater, which is considered to be one cause of sea desertification, we postulated that the supply of iron contained in steelmaking slag – a by-product of iron and steel manufacture – could help seaweed beds to recover. Our experiments have validated the effects. As supply of iron in the seawater and use of steelmaking slag for this were unprecedented, we had to make various attempts, steadily accumulate results, and make persistent efforts in order to achieve viable results. The Vivary Unit is a mixture of steelmaking slag and humus-rich soil, which supplies iron, an indispensable material needed for healthy seaweed growth, in the form of dissolved ions, to the seawater. The iron ion originates in the steelmaking slag and is eluted by the organic acids from the humus soil. NSSMC generates approximately 5 million tons of steelmaking slag every year, at the ratio of about 110 kg of the slag being generated as a by-product from manufacturing of one ton of iron and steel, while the humus soil is obtained by fermentation of waste wood chips. As both the slag and the enriched soil are recycled materials, they are easily and reliably sourced at low cost. [12.2/14.2] The seaweed bed created by placing the Vivary Unit on the sea floor can also be a promising contributor to improvement of the blue carbon ecosystem. Recently, much attention has been given to sequestering carbon in coastal ecosystems, or blue carbon. Maintenance and expansion of the seaweed beds created by use of the Vivary Unit, and its application to other marine areas, can be considered as a way to increase sequestering. As an additional possibility, use of the Vivary Unit may dampen the impact of ocean waves driven by tsunami, as coastal seaweed beds contribute to significantly damp offshore waves. Their effects can be boosted by installing the Vivary Unit along coast lines, which should eventually demonstrate the similar function to gray infrastructure including breakwater. [13.1] When Japan’s Fisheries Agency was revising the “Guideline on Measures Against Sea Desertification,” we conducted an experiment to validate the effects of the Vivary Unit, jointly with the Agency. The results were referenced on the revision, and helped raise awareness of this new iron fertilizing technology. Moreover, the Blue Carbon Study Group, which reports to the Ministry of Land, Infrastructure, Travel and Tourism, is studying the measurement and analysis of the sequestering, in preparation for future estimation of the potential of blue carbon. In line with such moves, we are continuing our project so that the artificial seaweed beds by use of the Vivary Unit can make a similar contribution to the ecosystem as the natural seaweed beds do. [13.2]

Partners

In 2004, the Sea Forestation Study Group began experimental use of the Vivary Unit at a test site provided by the Mashike Town Fishery Cooperative in Hokkaido Prefecture, for its development and validation (Phase I). The study group, comprised of experts in areas such as civil engineering and biology, and from industry and academia, including members from NSSMC, is also helping the experiment. Based on the outcome of Phase I and the relationship of trust with local people, a large-scale experimental project (Phase II) was begun in 2014 by the cooperative, supervised by the study group.

Implementation of the Project/Activity

The experiment in Mashike has been conducted in two phases. Phase I (2004-2014) was to develop and install the Vivary Unit in the actual sea floor for the first time, and validate its effects. Phase II (from 2014) began as a large-scale experiment with the aim of assessing the economic impact of creation of seaweed beds. Phase I experiment was sponsored by the Sea Forestation Study Group. This group, which is comprised of experts in areas such as civil engineering and biology, and from industry and academia (including those from the University of Tokyo, Hokkaido University, Nishimatsu Construction, Penta-Ocean Construction, and NSSMC and others), was established with the aim of validating the seaweed bed creation technology by use of the Vivary Unit, and has been testing the installation method and the quantitative assessment method for this. For Phase I, the test site selected was in Shaguma, Mashike Town, and was provided by the cooperative. The Vivary Unit was embedded in the seabed by NSSMC. The Shaguma site, having stones in the seabed and primarily being shoals of 3-4 meters in depth and about 100 meters in length, was ideal for sea forest creation. Six tons of the Vivary Unit were placed along 25 meters of the shoreline. The installation method aimed at the outflow of the water (containing iron ions) from the Vivary Unit, to be caused by the rise and fall of the tide. According to the research conducted by the study group before the placement of the Vivary Unit, conditions at this test site were typical of sea desertification. The site was covered with white stones with dead coralline algae (Corallinales), with exception of some kelp (Saccharina japonica) being scattered around (Photo 1, as of September 2004). Based on the results of Phase I, Phase II was begun in 2014 as a large-scale undertaking aimed at assessing the economic impact of creation of seaweed beds. It has been implemented by the Mashike cooperative. A second test site in Betsukari, Mashike Town was selected by the cooperative; this choice was made mainly because the site was not used for fishery and was also shoals with seabed stones, similar to Shaguma. NSSMC installed 36 tons of the Vivary Unit along the shorelines, by using the same placement method as before. The test site was six times larger than the Phase I site. It consisted of six sections with each section being 50 meters in length. Six tons of the Vivary Unit were placed in a 25-meter line, or half of the section length. In order to assess economic impact of seaweed bed creation, the sea urchin was selected as the fishery product to test as it likes to eat a certain edible kepl and the urchin is a valuable product harvested at the local port. The Sea Forestation Study Group has been engaged in research on water quality and seaweed beds after the Vivary Unit placement, and has been participating in discussions with the cooperative on yields of the sea urchin.

Results/Outputs/Impacts

In Phase I, the kelp beds grew from 0.3 hectare before the Vivary Unit placement to 0.6 hectare after one year (Photo 2) and about one hectare after two years. In 2013, nine years after the placement, the seaweed beds were still about one hectare. In 2008, four years after the placement, a sample of the Vivary Unit was retrieved and analyzed. The iron content of the steelmaking slag was roughly halved, leading us to estimate that the effects of the Vivary Unit in Shaguma should last for a little less than 10 years. Interestingly, the level of iron content in the seawater kept rising until the fifth year and then stayed at a level similar to that of the surrounding sea areas. This suggested that the Vivary Unit initially contributed to creation of a seaweed bed, which prompted reproduction of seaweed and improved the ecosystem to enable expansion of seaweed, resulting in the maintenance and expansion of seaweed without relying on the Vivary Unit. During Phase I, we worked closely with the cooperative, collected information on the characteristics of the area and the condition each year, and continuously validated the effects. Subsequently, a strong collaborative network was established with the cooperative and local people, leading into the Phase II large-scale testing. In Phase II, the iron content increased by 71 times since the placement of the Vivary Unit: from 0.4 μg/L to 25.6 μg/L. The size of the seaweed beds stayed almost the same from 540 m2 before the placement to 542 m2 after one year, but expanded sharply from the second year to 3,456 m2 by the end of the third year, an increase of 6.4 times. At the peak in 2017, flourishing of the kelp was confirmed up to 50 m offshore (Photo 3). Along with the expansion of the seaweed beds, as initially expected, a swarm of urchin arrived from surrounding areas and the yield in Betsukari increased by 1.8 times. As successful outcome of the Mashike experiment, apart from the expansion of the seaweed bed, other municipalities have also began installing the Vivary Unit. We welcomed many visitors from other prefectures to the site. These visitors had struggled with a decline in the seaweed bed, just their Mashike counterparts did, and witnessed the effects of the Vivary Unit. As a result, the number of experimental sites has gradually increased to 37. The seaweed bed created by the Vivary Unit is also promising as a blue carbon ecosystem. For an idea of what this might mean, an estimated 15,000 hectares of seaweed beds (mainly comprised of kelp) had been lost to sea desertification in Hokkaido during the 20 years from 1990 to 2010. If the 15,000-hectare seaweed bed is restored, sequestering of 0.93-2.03 million tons of carbon are estimated to be the result. We plan to continue research on annual biomass, gas exchange amounts at the seaweed bed and the like in order to calculate the carbon sequestering at the experiment site.

Enabling factors and constraints

We faced two major obstacles in initially promoting this project: to make its potential beneficiaries understand the merits of using steelmaking slag in coastal areas; and to convince them of the benefits of iron supply to the seawater. We took the following measures to overcome these obstacles and were consequently able to conduct the experimentation. (1)In Mashike, where we conducted the first experiment using the Vivary Unit, we focused on establishing a solid relationship of trust with local people concerned by closely working together, as we thought that this would help them appreciate the benefits and significance of the Vivary Unit. This was one of the reasons enabling a step-up from Phase I to Phase II and an expansion into the experimental project. (2)The Sea Forestation Study Group, an industrial-academia organization, was established and studied the validation method; the experiment using the Vivary Unit was conducted not by NSSMC alone but by a group of experts. Their objective assessment contributed to solidly establishing the sea forest creation technology by use of the Vivary Unit. A symposia were also conducted to announce and promote the outcome of the project. (3)We conducted a 96-hour acute toxicity test by exposing some valuable marine products (tiger prawns, disk abalone, and red sea bream) in the eluent of the Vivary Unit, in order to obtain assurance of the safety and convince those concerned on the idea of placing steelmaking slag in the ocean. The test result, that no fish or marine animals died after being exposed to the eluent, was examined by a third-party institution and the Vivary Unit was approved by the National Federation of Fisheries Cooperative Associations in 2010. (4)We built a large aquarium (mesocosm aquaria, namely SEA-Lab.. within an NSSMC facility and conducted a test to validate the effects of the Vivary Unit. We not only accumulated experiment results but invited many people concerned (from universities, private companies, the fishery business, and authorities, local people, students and others) to observe and learn about significance and effectiveness of the project. (5)Jointly with the Fisheries Agency, we conducted an experiment to validate the effects of the Vivary Unit in Oita Prefecture and Hokkaido. The results were referenced in the agency’s “Guideline on Measures Against Sea Desertification.” This helped raise awareness on the effectiveness of fertilizers, and in particular the supply of iron, as a measure against sea desertification (2014). (6)We presented the Vivary Unit in exhibitions featuring environmental initiatives by companies or civic groups (e.g., the EcoPro) in order to raise awareness, on the part of citizens and potential users, of the safety of steelmaking slag and the effectiveness of the Vivary Unit. (7)We invited local people engaged in the fishery business, authorities, and some media to the test site in 2008 and 2018. (8)We proactively publicized the scientific evidence of the effects and the results of the experiment by means of conference presentations and submission of papers (19 reports with peer review).

Sustainability and replicability

The Vivary Unit is made up of recycled materials, steelmaking slag and humus-rich soil. Steelmaking slag is a by-product of iron and steel manufacturing: about 110 kg of the slag is generated from manufacturing one ton of iron and steel. The humus soil is obtained from fermentation of wood chips from waste or thinned wood. As both of these are continuously generated, they can easily and reliably be sourced at low cost. The Vivary Unit can be installed anywhere by combining it with the Vivary Rock, a similarly-recycled artificial rock made from steelmaking slag. In case of shoals, such as in Mashike, the Vivary Unit can be embedded along the coast line. In case of creating seaweed bed offshore, the Vivary Unit is injected into an iron box and the box is installed in a deep water location or a deep sandy mud bottom where seaweed is hard to become established. The Vivary Rocks are assembled and iron boxes that contain the Vivary Unit are installed on the top of the structure or its surrounding area. In order to best demonstrate the effect of the Vivary Unit in a given location, a pre-installation survey, in particular of water quality and the nearby natural seaweed beds, is essential. Whether sea desertification is caused by the deficiency of iron, or nutrients containing nitrogen or phosphorous, or by damage from urchins or herbivorous fish, needs to be identified. Preferably, the tidal stream should also be surveyed to estimate how much of the nutrient component of the Vivary Unit may be lost. Another critical element for success of the Vivary Unit use is to obtain the cooperation of local fishermen or business operators in installation and surveying of effects of such use. The operating cost for the creation of a seaweed bed by use of the Vivary Unit is high. As the creation of a seaweed bed is expected to lead to restoration of the ecosystem and return of fish to the bed, quantitative assessment of the secondary effects, generated by the expected outcome, can be a driving force in expansion and sustenance of the effort, and development leading to the next stage. To achieve this progress, one idea is to survey the yields of fish or use of the seaweed bed, and make a quantitative assessment of the impact (such as the number of visitors and consumption) for a leisure or environmental study. Support and assistance by the national or prefectural government to the initiatives taken by fishermen, local administrators, and others is also important. The creation of seaweed can be promising for sequestering of carbon or for the blue carbon ecosystem. If the carbon that is sequestered can be quantified and recorded as being certain inventory, the effects of the seaweed bed creation may be understood in a wider context.

Conclusions

NSSMC has developed the Vivary Unit and has used it to create seaweed beds. The Vivary Unit is composed of steelmaking slag, which is a by-product of steel manufacture, and humus-rich soil made by combining fermented waste wood chips with soil. Both the slag and the humus soil are recycled materials that can be reliably generated and purchased at low cost. As supply of iron in the seawater and use of steelmaking slag for this were unprecedented, we initially had to make persistent efforts to be acknowledged. For the first adoption of the Vivary Unit in the ocean in Mashike Town, Hokkaido, first of all, a sea forestation study group was established by experts in industry and academia for objective research and development of installation methodology. We also strengthened the cooperative relationship with fishermen and local people concerned and jointly conducted an experiment so that the unprecedented adoption of steelmaking slag in a marine area could be accepted in the community. As a result, the demonstration experiment was stepped up from Phase I to Phase II and made considerable achievements. The Vivary Unit installation has led to a rise in the iron content in the seawater, a creation of 1.3 hectares of seaweed beds, and a 1.8 times increase in the yield of sea urchin, and proved positive effects for fisheries. With the aim of widely promoting the Vivary Unit, scientific papers on the mechanism of the effects and the results of the demonstration experiments have been published (including 19 papers with peer review) and scientific evidence has been accumulated. Moreover, we promoted the effects of the Vivary Unit at exhibitions and through site visits, as well as in the in-house mesocosm aquaria tests. Jointly with Japan’s Fisheries Agency, we conducted the experiment and the seaweed bed creation technology was referenced in the “Guideline on Measures Against Sea Desertification.” In order to assure safety, we conducted a 96-hour acute toxicity test by exposing three kinds of valuable marine products to the eluent of the Vivary Unit. The test result was examined by a third-party institution and the Vivary Unit received the approval of the National Federation of Fisheries Cooperative Associations. By accumulating such objective insights, the Vivary Unit has become better recognized and the number of its installed sites has increased to 37 sites across Japan. Going forward, for further penetration of the seaweed bed creation technology by use of the Vivary Unit and a resultant decrease in the desertified sea areas across Japan, a wider expansion of the present undertaking alone is not enough. Other indispensable elements are a cooperative network among business operators, local fishermen and authorities, and proactive initiatives by local people who use the developed site. We sincerely hope the national and prefectural governments will establish a support system for such initiatives. The revived seaweed bed is also promising as a blue carbon ecosystem. Going forward, we plan to continue the project and accumulate scientific evidence on the evaluation method and the effects of carbon sequestering.

Other sources of information

http://www.nssmc.com/product/slag/index.html Yamamoto et. al., (2010) Application of iron humates to barren ground in a coastal area for restoring seaweed beds. Journal of Chemical Engineering of Japan, 43, 627-634. Yamamoto et al., (2017) Effectiveness of iron fertilization for seaweed bed restoration in coastal area. Journal of Water and Environment Technology, 15, 186-197. Kato et. al., (2015) Application of steelmaking slag to marine forest restoration. Nippon Steel & Sumitomo Metal Technical Report, 109, 79-84. Kato et. al., (2015) Study on environmental impact evaluation of steelmaking slag using in coastal sea area. Nippon Steel & Sumitomo Metal Technical Report, 109, 85-89.

SDGS & Targets

Goal 12

Ensure sustainable consumption and production patterns

Goal 13

Take urgent action to combat climate change and its impacts

Goal 14

Conserve and sustainably use the oceans, seas and marine resources for sustainable development

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Biodiversity recovery of a coastal seaweed bed by using the Vivary Unit composed of steelmaking slag, by-product of steel manufacturing

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Name	Description
14.2	By 2020, sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience, and take action for their restoration in order to achieve healthy and productive oceans

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