What should we do if the ocean also loses hair? Its "hair transplanter" turns out to be seaweed

Produced by: Science Popularization China

Author: Liu Mingjie (PhD Candidate in Marine Ecology, Institute of Oceanology, Chinese Academy of Sciences)

Producer: China Science Expo

Editor's note: In order to unveil the mystery of scientific work, the China Science Popularization Frontier Science Project launched a series of articles called "Me and My Research", inviting scientists to write articles themselves, share their scientific research experiences, and create a scientific world. Let us follow the explorers at the forefront of science and technology and embark on a journey full of passion, challenges, and surprises.

"Like a piece of seaweed, seaweed, drifting with the waves", the seaweeds drifting with the waves are like the beautiful hair of the "sea girl" fluttering in the wind.

seaweed

(Photo source: veer photo gallery)

Seagrasses are the only type of monocotyledonous angiosperms that can adapt to submerged life in the ocean and are widely distributed in tropical and temperate coastal waters around the world.

Dense seagrass beds provide many ecological services, such as purifying water, protecting coasts, maintaining marine biodiversity, and storing organic carbon. They play a key role in climate regulation and improving human well-being.

In recent years, with climate change and increasing intensity of marine development and utilization, the tremendous pressure caused by environmental changes and human activities has caused the seagrass bed ecosystem to decline rapidly on a global scale. The blue ocean has suffered from "hair loss" disease, and there is an urgent need to find a "good medicine" to curb this phenomenon and protect and restore the seagrass bed ecosystem.

Seagrass bed ecological restoration is a necessary means to make up for the decline in biodiversity and the loss of ecosystem service functions in seagrass bed ecosystems. It is regarded as a nature-based solution that can effectively respond to climate change and protect biodiversity.

In order to compensate or reduce the losses caused by the degradation of seagrass beds, a large number of ecological protection and restoration actions have been actively carried out in different regions of the world, accumulating valuable experience for the restoration and reconstruction of seagrass beds. Some of these cases have obtained good feedback and results. Large-scale seagrass bed restoration programs have played an important role in improving local ecological health and enhancing the level of ecosystem function.

There are many reasons for the degradation of seagrass beds, such as water quality deterioration, physical damage, species competition, etc. Before carrying out human intervention, we must first find the real "cause" that causes the degradation of seagrass beds so that we can carry out targeted protection and management measures.

Find the cause and improve the habitat

From the 1950s to the 1980s, eutrophication of the water bodies in Tampa Bay, Florida, USA, intensified, leading to frequent outbreaks of phytoplankton and large algae, reduced water transparency and dissolved oxygen levels, and the death of seagrass due to "starvation" and lack of oxygen. The distribution area of ​​seagrass beds decreased by about 8,900 hectares.

In order to improve the harsh environmental conditions in Tampa Bay and restore its ecological functions, the local government has adopted a series of management measures to control land-based nutrient emissions, including strict sewage discharge standards, strengthening wastewater recycling and reuse, controlling agricultural fertilization and phosphate mining.

After nearly 30 years of efforts, the total nitrogen load in Tampa Bay was significantly reduced when it was reassessed in 2012, the concentrations of total nitrogen, total phosphorus and chlorophyll a in the water body all decreased significantly, and the seagrass bed coverage area increased by approximately 5,258 hectares.

Tampa Bay macroalgae bloom

(Image source: Reference 2)

At the same time, the recovery of seagrass beds further promoted the absorption of nitrogen and phosphorus nutrients and reduced water turbidity, thus forming a virtuous circle. The recovery rate of seagrass beds can reach about 300 hectares per year. By 2018, the area had recovered to 16,451 hectares, exceeding the expected recovery target of 15,378 hectares.

This shows that by taking reasonable and effective management measures to remove the threatening factors that cause seagrass bed degradation and improving the seagrass bed habitat, the seagrass beds can be effectively restored. It also indirectly reflects the importance of diagnosing the causes of seagrass bed degradation.

If the causes of seagrass bed degradation are not investigated and analyzed, and restoration activities are carried out rashly without removing or reducing interfering factors, the restoration may have little effect or even fail. For example, in the case of Ruppia tuberosa restoration in southern Australia, the restoration of seagrass patches was unable to complete the normal life cycle process because the drought caused by the low water level in spring was not addressed. The seed bank could not be continuously replenished and eventually dried up.

Adapt measures to local conditions and prescribe the right medicine

After identifying the "cause", appropriate restoration technology should be selected according to environmental characteristics. **Seed restoration is gradually being recognized as an important technical means for large-scale seagrass bed ecological restoration. **Seagrass can produce seeds of different sizes, lifespans and dispersal abilities. Compared with plant transplantation, seagrass seeds are easy to collect, store and transport, and seed collection causes less damage to the donor grass bed, while also maintaining genetic diversity.

In addition, the seed method is easier to form economies of scale than the transplantation method. Increasing the scale of restoration helps to disperse risks in time and space to cope with fluctuations in environmental conditions, thereby improving the success rate of restoration.

Since 1999, researchers have been conducting large-scale seeding restoration in four bays in eastern Virginia, U.S.A. They have conducted in-depth research on the collection, screening and preservation of eelgrass seeds, as well as the time, density, depth and methods of seeding, and have developed efficient seed collection, processing and seeding plans.

Due to suitable environmental conditions and less interference from human activities, eelgrass grew and spread rapidly, forming dense and continuous seagrass beds. By 2010, the area of ​​seagrass beds had recovered to 1,714 hectares (37.8 million seeds were sown), about 14 times the sown area.

After the establishment of a stable seagrass bed, the seeds can be self-sufficient and no longer need to be collected from external grass beds. By 2018, the area of ​​eelgrass seagrass beds had recovered to 3,612 hectares, with a total of 74.5 million seeds sown. The restoration of the seagrass beds has established a positive positive feedback mechanism, which has reduced the turbidity of the water in the bay, increased the carbon and nitrogen reserves in the sediments, increased the number and abundance of fish and invertebrates, and gradually restored and improved the ecological service functions of the seagrass beds.

After years of transplant failures, seagrass restoration in the Wadden Sea has gradually shifted from transplantation to seeding, hoping to disperse risks and increase the success rate of restoration through large-scale restoration. Cockburn Sound in Western Australia has been trying to use seeds to restore degraded Posidonia australis seagrass beds since 2018, hoping to reduce restoration costs while increasing the participation of local community residents through continuous improvement of restoration plans.

Australian boxwood grass seed collection

(Image source: Reference 5)

All people participate, unity is strength

The high labor costs incurred in the collection and deployment of restoration materials is a long-term limitation to seagrass restoration work. Although a variety of mechanized equipment has been developed, such as seed collectors, seeders, and transplanters, these mechanized equipment have high usage conditions and are restricted by the complex hydrological and geographical conditions of the restoration area. The current mechanized operation process of seagrass bed restoration work is difficult to carry out, and large-scale seagrass restoration still relies on intensive labor. By allowing the public or volunteers to participate in the seagrass restoration process, labor costs can be greatly reduced.

In order to restore the seagrass beds in the Port Stephens area of ​​New South Wales, Australia, researchers applied the concept of "Citizen Science" to seagrass restoration. By launching an "Operation Posidonia" activity, they encouraged community residents to collect seagrass fragments washed ashore by wind and waves. The collected fragments were screened and temporarily raised before being transplanted by professionals to the sea area to be restored.

Dense seagrass

(Photo source: veer photo gallery)

In the first 14 months of the activity, local volunteers collected more than 1,200 seagrass fragments. After monitoring, the survival rate of transplantation was over 50%, which effectively reduced the need to collect plants from natural grass beds. At the same time, it also enabled local community residents to participate in the seagrass restoration plan and raised people's awareness of the importance of seagrass.

In addition to collecting seaweed fragments, community residents can also participate in the collection, processing and sowing of seaweed seeds, transplantation of seaweed plants, transportation of personnel and equipment, promotion of activities, etc. In the seeding restoration case in Virginia, USA, volunteers collected more than 10 million seaweed seeds and played an important role in the entire restoration work.

The general lack of public awareness of the importance of seagrasses is considered one of the key challenges to global seagrass conservation, indicating the need for appropriate science communication activities to accompany and promote seagrass bed protection and restoration actions.

The "scientist + volunteer" seagrass restoration model is a new idea. This model defines seagrass restoration as a public welfare environmental protection activity that everyone can participate in. It mobilizes the public to participate in seagrass restoration work, making seagrass restoration more popular than scientific research work. It can effectively solve the problem of labor shortage and reduce restoration costs.

As shown in the figure below, scientists refer to scientific researchers, who mainly play a role in popularizing science, technology research and development, equipment support and technical training. Their main task is to lower the technical threshold for seagrass restoration and increase the feasibility of public participation in seagrass restoration. Volunteers cover a wide range and can include many social forces such as public welfare organizations and community residents. They mainly make up for the shortcomings of scientific researchers in terms of funding, publicity, personnel organization, etc., so that the public can participate more widely and deeply in seagrass restoration activities.

Conceptual image of the “scientists + volunteers” seagrass restoration model

(Image source: self-made by the author)

The difficulty of this model lies in how to attract more volunteers to participate in the seagrass restoration plan. First, the public needs to understand the extent and consequences of the environmental crisis (such as ecological, social, economic, and cultural aspects). Then, we can cooperate with schools, communities, and public welfare organizations to hold regular publicity activities and training, and use social media and news media to popularize science, recruit volunteers, and promote activities through public service advertisements, video clips, and self-media tweets, and then form public welfare organizations and teams specializing in seagrass restoration.

Ecological restoration of seagrass beds in my country

my country is rich in seagrass resources, with 16 existing seagrass species covering a distribution area of ​​nearly 30,000 hectares. However, seagrass research started late. Compared with coastal ecosystems such as mangroves and coral reefs, the protection and restoration of seagrass beds has lagged behind, and seagrass resources have declined. Compared with before the 1980s, more than 80% of the seagrass beds in my country's coastal waters have disappeared.

The decline of seagrass bed ecosystems has aroused people's attention and exploration of seagrass bed protection and restoration. According to different causes of seagrass bed degradation and different seagrass species, researchers have conducted extensive exploration of seagrass bed restoration theories and technologies in Hebei, Shandong, Guangxi and Hainan provinces, proposed a number of new technologies for seagrass bed ecological restoration, and established a relatively complete technical system.

However, due to various reasons, related research is basically at the experimental scale, there are few large-scale restoration examples, and the restoration effects are also uneven. Among the 1,011 coastal restoration projects carried out in my country from 1950 to 2014, there were only 11 seagrass bed restoration projects, and the total restoration area was less than 30 hectares.

Since the 18th CPC National Congress, as the country attaches great importance to the protection of marine ecological environment, the ecological restoration of seagrass beds has been supported by national strategies, and my country has also carried out a number of large-scale seagrass bed ecological protection and restoration projects, such as the Caofeidian District Marine Ecological Protection and Restoration Project in Tangshan City, Hebei Province (total restoration area of ​​636 hectares), the Southern Marine Ecological Restoration, Supervision and Monitoring and Evaluation Project of the Yellow River Delta National Nature Reserve (total restoration area of ​​50 hectares), etc.

Workers from CSSC Environmental Group collect eelgrass seedlings in the eelgrass seedling collection area of ​​the marine ecological protection and restoration project in Caofeidian District, Tangshan City (drone photo)

(Photo source: Xinhua News Agency)

my country has also strengthened the construction of the national ecological restoration standard system, and issued the first national standard for seagrass bed ecosystem restoration technology - "Technical Guidelines for Marine Ecological Restoration Part 4: Seagrass Bed Ecological Restoration", and the first industry standard for seagrass bed ecological restoration technology - "Technical Specifications for Seagrass Bed Construction", which provide a technical basis for standardizing and safeguarding my country's seagrass bed ecological restoration projects.

At the same time, more and more public welfare forces have joined the ranks of seagrass bed protection and restoration. Projects such as the "Guangxi Hepu Dugong National Nature Reserve Seagrass Bed Protection Action Project" funded by the United Nations Development Program, the "Action for the Sea" funded by the Sustainable Global Environment Institute and the Beijing Entrepreneurs Environmental Protection Foundation, and the "Wei Hai Action" jointly initiated by the Ministry of Natural Resources and public welfare organizations are also working hard to enhance the public's awareness of seagrass bed protection and explore sustainable development paths for seagrass bed protection and restoration based on public participation.

The release of "Carbon Sink Measurement and Monitoring Methods for Seagrass Bed Ecological Restoration" and the successful signing of the country's first public seagrass bed blue carbon intention subscription also mark the feasibility of using the blue carbon trading market mechanism to promote seagrass bed ecological restoration projects.

In order to prevent the further deterioration of "hair loss", by analyzing international seagrass bed restoration cases, we need to further continuously monitor the dynamic changes of seagrass beds in the future, accurately grasp the current status of seagrass bed ecosystem degradation; try to carry out artificial cultivation of seagrass, develop mechanized restoration equipment, and improve the success rate and efficiency of restoration; strengthen knowledge sharing and public participation among government decision makers, non-profit organizations and other forces. I believe that with long-term efforts, the blue ocean will surely grow thick "hair" again!

References

[1] Govers, LL, Heusinkveld, JHT, Grafnings, MLE, Smeele, Q., and van der Heide, T. (2022). Adaptive intertidal seed-based seagrass restoration in the Dutch Wadden Sea. PLoS One 17(2), e0262845. doi: 10.1371/journal.pone.0262845.

[2] Greening, H., Janicki, A., Sherwood, ET, Pribble, R., and Johansson, JOR (2014). Ecosystem responses to long-term nutrient management in an urban estuary: Tampa Bay, Florida, USA. Estuarine, Coastal and Shelf Science 151, A1-A16. doi: 10.1016/j.ecss.2014.10.003.

[3] Liu, Z., Cui, B., and He, Q. (2016). Shifting paradigms in coastal restoration: Six decades' lessons from China. Science of The Total Environment 566-567, 205-214. doi: 10.1016/j.scitotenv.2016.05.049.

[4] Orth, RJ, Lefcheck, JS, McGlathery, KS, Aoki, L., Luckenbach, MW, Moore, KA, et al. (2020). Restoration of seagrass habitat leads to rapid recovery of coastal ecosystem services. Science Advances.

[5] Sinclair, EA, Sherman, CDH, Statton, J., Copeland, C., Matthews, A., Waycott, M., et al. (2021). Advances in approaches to seagrass restoration in Australia. Ecological Management & Restoration 22(1), 10-21. doi: 10.1111/emr.12452.

[6] Tan, YM, Dalby, O., Kendrick, GA, Statton, J., Sinclair, EA, Fraser, MW, et al. (2020). Seagrass Restoration Is Possible: Insights and Lessons From Australia and New Zealand. Frontiers in Marine Science 7. doi: 10.3389/fmars.2020.00617.

[7] Zhou Yi, Jiang Zhijian, Qiu Guanglong, Zhang Peidong, Xu Shaochun, Zhang Xiaomei, Liu Songlin, Li Wentao, Wu Yunchao, Yue Shidong, Gu Ruiting, Ding Li, Zheng Fengying, Huang Xiaoping, Fan Hangqing. Current distribution status, degradation causes and protection strategies of seagrass resources in China[J]. Oceanology and Limnology, 2023, 54(5): 1248-1257.