Wild, keen, and fearless.
Underwater meadows are rapidly disappearing around the world, but new research shows that they may be the most easily restored coastal habitats.
Before November 23, 2020
Twenty years ago, scientists and volunteers on the coast of Virginia started throwing seaweed seeds into barren seaside lagoons. In the 1930s, diseases and strong hurricanes destroyed these plants, and nearby grasslands were unable to act as a natural source of dispersion for seeds to bring them back.
The planting work eventually delivered more than 70 million seeds, and it paid off, creating 9,000 acres of underwater plants.
Now, monitoring of these restored grasslands shows that their restoration has multiple benefits, including a greatly increased abundance of fish and invertebrates, improved water transparency, and a large amount of carbon and nitrogen capture.
"It is very laborious to grow adult seaweed, but we started to consider using seeds in the laboratory and found it easy," said Robert "JJ" Ott, the lead author of the new paper.
About the project. "These areas have good water quality, shallow terrain, and close to the ocean, so you can bathe in cool water-perfect conditions. The speed is amazing."
The paper is part of growing evidence that seagrass meadows are easier to recover than other coastal habitats.
Successful seaweed restoration methods include
. Elimination of threats, proximity to the donor seagrass bed, planting techniques, project scale and site selection all play an important role in the success of the restoration effort.
However, human assistance is not always required. In areas where some beds remain, seaweed can even recover on its own after reducing or removing the source of stress. For example, after Tampa Bay improved water quality by reducing the nitrogen load in runoff by about 90%, seagrass began to recover.
However, more and more seagrass meadows are difficult to survive.
According to the fact that the number of marine flowering plants worldwide has decreased since the 1930s, the current disappearing rate is equivalent to a football field every 30 minutes.
. And a study published in 2018 found that the rate of decline is
In many areas.
The reasons for the decline vary from region to region and overlap. These include thermal stress caused by climate change; human activities such as dredging, anchoring and coastal infrastructure; and intentional evacuation in tourist areas. In addition, increased runoff from land carries sediments that make the water turbid, thereby preventing the sunlight needed by plants for photosynthesis. Runoff may also carry pollutants and nutrients in fertilizers, destroy habitats and cause algal blooms.
All these damages come at a price.
Like rain forest and
, The loss of seagrass increases carbon dioxide emissions. This not only causes trouble for certain habitats, but also troubles for the entire planet.
Although seagrass covers up to 0.2% of the seabed,
The capacity of the ocean to store carbon in the soil, and these meadows are estimated to store carbon dioxide 30 times faster than most terrestrial forests. The slow decomposition rate of seaweed sediments is the cause of their decomposition
. In Australia, according to
Researched by scientists at Edith Cowan University, the loss of seagrass meadows since the 1950s has increased carbon dioxide emissions by 5 million vehicles each year. The United Nations Environment Programme reported that seagrass in the Chesapeake Bay fell by 29% between 1991 and 2006, resulting in an estimated loss of up to 1.8 million tons of carbon.
Seagrass also protects coastal habitats. A healthy grassland can slow down wave energy, reduce erosion and reduce the risk of flooding. According to Morro Bay, California, seagrass species has declined by 90%, which has led to widespread erosion.
Researchers from California State Polytechnic University.
Lead author Ryan Walter said: "Immediately, we found a general trend of sediment loss or erosion." "Many studies have shown this on separate eelgrass beds, but few studies are system-wide. To study it within."
In the tropics, the natural protection of seagrass can reduce the need for expensive and often environmentally unfriendly
Regularly in the tourist area.
The seagrass ecosystem improves water quality and transparency, filters out particles in the water column, and prevents the re-suspension of sediments. In the future, this role may become more important. By producing oxygen through photosynthesis, grassland can help offset the decrease in oxygen levels caused by rising water temperature (the solubility of oxygen in warm water is lower than in cold water).
Meadows also provide important habitats for various marine life, including marine mammals such as fish, turtles, birds, manatees, seaweed, invertebrates, and algae. They are
One of the largest fisheries in the world
Only one fish habitat in Florida.
On the contrary, their disappearance will lead to the death of marine life. Biscayne Bay in Florida lost more than 20 square miles of seagrass, which may be a large-scale
Piero Gardinali, a professor at Florida International University, said that by the summer of 2020, due to rising temperatures and falling oxygen levels, the lack of oxygen-producing grasses makes the basin more vulnerable.
Governments and conservationists around the world have put a lot of effort into coastal restoration. This helped some seagrass populations.
However, the pressure still exists and the recovery work becomes more complicated.
A paper published in September this year found that only 37% of seaweed restorations survived. Newly restored grasslands are still vulnerable to the original stressors that depleted them, as well as storms and climate change.
Alexander Charlen Heyman of the School of Natural Resources and Environment at the University of Florida said that in the Chesapeake Bay, a cold-water species of seagrass is currently reaching high temperatures, especially in summer. As the sea continues to warm due to climate change, the species is likely to disappear there.
Climate-driven sea level rise also complicates the problem. Seagrass grows strong at a certain depth-too shallow, they dry out or are eaten, too deep, there is not enough light for photosynthesis.
Fortunately, according to a study, seagrass meadows can flourish for hundreds of years with their own equipment.
It was published last year by Hyman and other researchers at the University of Florida. The researchers came to their conclusions by observing the shells of live mollusks and fossil shells to estimate the age of the grasslands in Florida's Greater Bend on the Gulf Coast.
The area has vast, relatively primitive seagrass meadows. Co-author Michal Kowalewski said: "Our motivation is to understand the past history of these systems, and the shell stores a lot of history."
The high similarity between the live shell and the dead shell indicates that the area is stable, while a mismatch indicates that the area has changed from seaweed to barren sand. The researchers found that the long-term accumulation of shells is similar to that of live shells, indicating that the habitat of seagrass has remained stable over time.
Hyman believes that this stability enables biodiversity to flourish and creates conditions for the survival and reproduction of special species.
Kowalewski pointed out that the discovery of the long-term stability of seagrass meadows is of great significance to the selection of restoration sites.
He said: "There must be a reason for them to thrive in one place, but not a mile away. The fossil data suggests that they may never have been." "If we remove the seagrass patch, we will not be able to hope to plant it in Other places. Not just special seaweeds. The location found is also very special."
A better way is to protect these habitats first, but we have not done enough work yet. The United Nations reports that marine protected areas can only protect 26% of the recorded seagrass meadows, compared with 40% for coral reefs and 43% for mangroves.
At the same time, Gardinelli suggested that small-scale actions can play a big role-such as fertilizer regulations.
He said: "Nitrogen and phosphorus are the problem." "This is a simple first step. We can change the way we do little things one at a time."
At this point, everything we do will help, not only for seaweed, but also for everything that depends on seaweed.
“These habitats are vital,” Hyman said. “Leave aside the control of soil erosion and all these benefits that people might not find, they hide the juvenile stages of all these marine species that we like to eat (such as blue crabs). From this perspective, seaweed has brought countless benefits to the economy."
Those benefits are more ignored, but hope to have more obvious and more attractive terrestrial habitats. Experts say this needs to change.
Walter said: "The trees in the Amazon rainforest provide the system with the eel grass in the estuary system." "Not only the beautiful grass, but also many ecosystem services."
If we allow it, it will provide hundreds of years of service.
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