On the western side of Lake Macquarie in New South Wales, Australia, sits Myuna Bay – a quiet bay with meadows of seagrass waving beneath the water. The most common marine plant species you find there is Zostera muelleri. It has long ribbon-like leaves that grow from stems (called rhizomes)
Heat stress from marine heat waves can create a toxic relationship between seagrasses and a hidden ecosystem of bacteria, transforming a previously beneficial co-existence between marine plants and microbes into a harmful one, a University of Sydney and UNSW study has found. Seagrasses are marine flowering plants that act as
A new study of the British Isles’ coastal ecosystems has revealed that nitrogen enrichment is significantly reducing the abundance and variety of marine life. The research, published by scientists at Swansea University and the charity Project Seagrass, warns that increasing nutrient flows are overriding local habitat conditions to restructure and
New research led by scientists at University of California’s San Diego’s Scripps Institution of Oceanography is shining a spotlight on one of the ocean’s most overlooked habitats: seagrass. Led by Scripps Oceanography Ph.D. candidate Rilee Sanders, the study documented the first successful restoration of open-coast seagrass (common eelgrass). The findings offer
The wellbeing benefits of nature are often linked to forests or habitats that support diverse pollinators. Spending time in green spaces reduces stress and anxiety, for example. By contrast, the benefits of the ocean are more commonly associated with fishing, exciting creatures such as whales and dolphins, or adventure watersports, rather than
Extreme heat can have a devastating effect on seagrass, but new research from Edith Cowan University (ECU) could shape how these vitally important marine ecosystems are managed and restored. In separate studies carried out on both the west and east coasts of Australia, researchers have investigated how seagrasses stand up
Current estimates of the global extent of seagrass range from between 160,000-266,000km. Such a high degree of uncertainty presents challenges for researchers and managers and their ability to make informed decisions which account for the changing status of seagrass ecosystems. Key to improving our understanding of seagrass presence and absence,
Ewan Garvey, one of Project Seagrass’ Interns for the 2025-26 academic year, explores how seagrass can provide protection for coastal communities. As the seasons transition from autumn into winter, storms often become a pressing concern for coastal communities. In recent years, the growing impacts of climate change have become increasingly
Seagrass meadows have an important climate protection function due to their long-term carbon storage potential. An international research team led by the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) has now been able to show that seagrass beds have a stronger influence on the carbon and sulfur cycling in
A major global study using teabags as a measuring device shows warming temperatures may reduce the amount of carbon stored in wetlands. The international team of scientists buried 19,000 bags of green tea and rooibos in 180 wetlands across 28 countries to measure the ability for wetlands to hold carbon
On the western side of Lake Macquarie in New South Wales, Australia, sits Myuna Bay – a quiet bay with meadows of seagrass waving beneath the water. The most common marine plant species you find there is Zostera muelleri. It has long ribbon-like leaves that grow from stems (called rhizomes) buried beneath the sediment and provides important shelter for small fish, shrimp and crabs. Although Myuna Bay looks quite normal, it is actually a bit unusual. For decades, the nearby Eraring power station released warm water into the lake that was used to cool down their systems, causing water temperatures here to be consistently 1°C to 3°C higher than nearby sites. This made the bay a rare natural laboratory for understanding what warming oceans might mean for coastal ecosystems. In our new research, published today in the journal New Phytologist, we used this setting to investigate what happens to seagrass and the microbes living in the sediment when ocean temperatures increase in the way climate models predict they will in the future. Experimental design. Sediments (intact or disrupted microbial communities via autoclaving) and seagrass (Zostera muelleri) plants (with intact or disrupted rhizosphere microbial community) were transplanted into the warm environment to test how belowground microbes affect seagrass performance under elevated ocean temperatures. Six plants (two from each of the three ambient and warm sites) were randomly placed into each pot with five replicate pots per treatment. Credit: New Phytologist (2026). One of the most important coastal habitats Seagrasses are often overlooked, but they are among the most important coastal habitats on Earth. They are marine flowering plants that stabilize sediments, improve water clarity and provide food and shelter for many marine animals. They also store large amounts of carbon in the sediments beneath them, making them important for slowing climate change. But seagrasses don’t function alone. Beneath the leaves, in the sediments, lives a hidden ecosystem of microbes: bacteria, fungi and other microscopic organisms that interact with the plant. Just as plants on land depend on soil microbes, seagrasses rely on microbial communities in the sediment around their roots. These microbes carry out many important processes. Some provide nutrients that plants need to grow. Others break down organic matter or detoxify harmful compounds in the sediment. In some ways, the relationship can be compared to the partnership between corals and the microscopic algae living inside them. Corals rely on those algae for energy, while seagrasses depend on microbes to help maintain a healthy environment around their roots. But not all microbes are helpful. Some produce sulfide, a compound that can be toxic to seagrass roots when it accumulates in sediments. We are starting to find out that whether microbial communities help or harm the plant can depend strongly on environmental conditions, including increases in ocean temperatures due to climate change. Simulating future ocean warming in the field To understand how ocean warming might affect the relationship between seagrasses and microbes in the sediment under realistic future conditions, we designed a field experiment at Myuna Bay. We collected seagrass plants and sediments from both warmer and “normal” temperature sites in Lake Macquarie. Some plants were grown in sediments with their microbial communities intact. In other treatments, the sediments were heated to 121°C to disrupt the microbes; this reduces total bacterial abundance by more than 95%. This allowed us to test how plants performed when the microbial community was intact versus when it had been disrupted. We then placed plants in pots with those different sediments and exposed the plants to warmer conditions at Myuna Bay, similar to those expected in the future. After one month, we monitored how the plants responded. We measured how they survived, how many shoots they produced and how their biomass changed over time. At the same time, we analyzed the bacterial communities in the sediment using DNA sequencing to see how they differed between treatments. Looking beyond plants When plants were grown in sediments from “normal” temperature sites, seagrass performed well whether the microbes were intact or disrupted. But when plants were grown in sediments from warmer sites, the outcome changed: plants growing with intact sediment microbial communities performed worse. These sediments from the warm areas also contained different bacterial communities, which may help explain the lower plant biomass we observed. One possible explanation involves sulfide. In seagrass sediments, certain microbes produce sulfide as part of their metabolism. At high concentrations, sulfide can be toxic for seagrasses. Warmer temperatures may stimulate microbial activity, increasing sulfide production and tipping the balance from a supportive microbial community to one that harms the plant. Our findings highlight an important idea: the impacts of climate change on seagrasses can’t be understood by looking at the plants alone. The microbial communities living in the sediment can also influence how these plants respond to warming. This has important implications for conservation and restoration. Around the world, seagrass meadows are declining due to coastal development, pollution and climate change. Restoration projects often focus on planting seagrass shoots or seeds. But the condition of the surrounding sediment, including its microbial community, may also determine whether restoration succeeds. As oceans continue to warm, the future of seagrass meadows may depend not only on the plants we see when snorkelling, but also on the microscopic microbes living in the sediment beneath them. More information: This article is republished from Phys.org Read the research paper here: Ocean warming indirectly affects seagrass performance through effects on sediment microbial communities – Jongen – New Phytologist – Wiley Online Library
Heat stress from marine heat waves can create a toxic relationship between seagrasses and a hidden ecosystem of bacteria, transforming a previously beneficial co-existence between marine plants and microbes into a harmful one, a University of Sydney and UNSW study has found. Seagrasses are marine flowering plants that act as fish nurseries, purify water and are crucial in coastal carbon storage. Their decline is often missed until it’s too late. The role soil microbes play in land plant health and climate resilience is well known. But for marine plants like seagrass, this science has largely been overlooked. “It’s worth paying attention to what happens in seagrass habitats as marine heat waves become more common. That information could be invaluable for conservation efforts,” said lead researcher Dr. Renske Jongen, from the School of Life and Environmental Sciences. In an underwater gardening experiment, biologists found a diverse bacterial ecosystem in the soil and around seagrass roots. The bacterial ecosystem was in a delicate balance, controlling the chemistry of the soil and seagrass health. Under increased water temperature, tiny bacteria living in the sediment among seagrass roots can reduce seagrass tolerance to climate change, stunting its growth and its ability to cope with heat stress. Higher temperatures favor bacterial species known to produce hydrogen sulfide, a compound toxic to seagrass, which may stunt seagrass growth. Plants previously exposed to warmer conditions suffer more from those changes in microbes. The researchers found seagrass growing in sediments from warm areas produces 34% less biomass when the natural sediment microbes weren’t disturbed. The findings show how bacterial communities are a hidden factor in recovering and restoring seagrass. “Just as microalgal symbionts (tiny organisms that rely on sunlight as energy) are key to the health of coral reefs, bacterial symbionts nestled at the roots and sediment of seagrasses can influence whether seagrass survives or declines,” said Dr. Jongen. “Even though seagrasses may look okay at first glance, what we’ve found below ground under increased temperature tells a different story.” Just as heat waves have hit terrestrial plants, marine heat waves have thinned out once lush and widespread seagrass meadows along the Australian coast. They are mainly found in shallow coastal waters and estuaries from tropical Queensland all the way down to the cool, temperate waters of Tasmania. Microbial communities also shape marine plants’ responses to environmental stress. Heat stress isn’t only about hot water. “Increased water temperatures dramatically change the ecosystem of microbes living among the seagrass roots and how microbes co-exist,” said senior author Associate Professor Ziggy Marzinelli from the University of Sydney. “Under heat stress, the microbial communities around seagrass roots shift in ways that can harm rather than help the plant.” How decades of industrial history created a real-world climate experiment In Myuna Bay in Lake Macquarie, history has created the perfect conditions for the research team to answer the question—”what would happen to seagrasses and microbes if water temperatures increased as projected by climate change models?” Since 1984, Eraring Power Station has continually fed a plume of warm estuarine water into the lake. This has made some of the lake waters up to three degrees warmer than ambient temperature for nearly four decades, mimicking both marine heat waves and what future oceans could be like along the Eastern Australia coast by 2090. “This has inadvertently created realistic conditions for the ultimate ‘gardening experiment’—for us to test how seagrass and below ground microbe health is shaped by exposure to higher-than-normal ocean temperatures,” said Dr. Jongen. “Locals are aware of the temperature increase in the area. It also has a reputation as a popular fishing spot because the hot water attracts a lot of fish species and everything from sharks to turtles have been seen here.” The research team transplanted Zostera muelleri, a species of sea grass native to coastal areas of Australia, into the lakebed. They also extracted and analyzed DNA to find the type of bacterial communities from the sediment and sediment from the seagrass roots to find how their composition changed at different temperatures. That was when they uncovered the change in bacterial communities and especially the relative increase of bacterial species that suppressed seagrass growth. “Our study highlights the overlooked role of microbes in tipping the balance in marine environments,” said Professor Paul Gribben from the University of New South Wales. “Seagrass restoration should not just focus on selecting species that are more heat tolerant, but also look deeper, below the ground surface—and, if needed, address microbial communities before transplanting or restoring seagrass meadows.” More information: This article is republished from Phys.org Read the research paper here: Ocean warming indirectly affects seagrass performance through effects on sediment microbial communities – Jongen – New Phytologist – Wiley Online Library
A new study of the British Isles’ coastal ecosystems has revealed that nitrogen enrichment is significantly reducing the abundance and variety of marine life. The research, published by scientists at Swansea University and the charity Project Seagrass, warns that increasing nutrient flows are overriding local habitat conditions to restructure and deplete coastal biodiversity. While the Planetary Boundaries for nitrogen and phosphorus flows have already been exceeded globally, this study provides a rare, large-scale assessment of how these nutrients impact the fine-scale diversity of our coastlines. Factors causing the pollution include sewage, agricultural waste, and poor land management. The study examined seagrass meadows in 16 different marine environments, including estuaries, lagoons, and islands. These ranged from the Orkneys Islands and the Firth of Forth to the Solent and the Island of Skomer. The findings were stark: higher nitrogen concentrations were consistently associated with a decrease in animal abundance and species richness. Specifically, the researchers found that an increase of nitrogen could correspond to an approximately 90 per cent decrease in the abundance of life per unit of available habitat area. “Eutrophication, the enrichment of water by nutrients, remains one of the most pressing environmental challenges in coastal waters, particularly regarding biodiversity loss,” said the authors. Key findings: Nitrogen as a driver: Nitrogen enrichment emerged as a consistent driver of biodiversity loss across the UK, even when accounting for the physical complexity of the environment; Habitat sensitivity: Coastal and lagoon environments showed the strongest declines under enhanced enrichment. In particular, phosphorus exhibited a devastating negative effect on life within lagoon environments; Site-specific impact: While some moderate enrichment was tolerated in specific estuarine settings, further enrichment in already impacted coastal sites exacerbated the loss of species; and, Beyond physical structure: Surprisingly, the physical traits of the marine vegetation (such as leaf length or biomass) had little influence on diversity compared to the overwhelming impact of local nutrient regimes. Crab in seagrass in Orkney Credit Lewis Jefferies Gastropods in seagrass. Credit Lewis Jefferies The researchers argue that current regional conservation targets may be insufficient. Because the effects of nutrients are “context-dependent,” effective management requires strategies tailored to the specific ecological conditions of a site. They concluded: “Our findings demonstrate that eutrophication alters biodiversity in complex ways. Effective management will require site-specific nutrient reduction and monitoring strategies that reflect local conditions rather than uniform regional targets.” The research was conducted by scientists from Swansea University, and Project Seagrass. The team used standardised sampling and mixed-effects modelling to isolate the drivers of biodiversity across the UK seascape. Read the research in full in Global Ecology and Conservation.
New research led by scientists at University of California’s San Diego’s Scripps Institution of Oceanography is shining a spotlight on one of the ocean’s most overlooked habitats: seagrass. Led by Scripps Oceanography Ph.D. candidate Rilee Sanders, the study documented the first successful restoration of open-coast seagrass (common eelgrass). The findings offer promising insight into the feasibility of restoring high-value coastal habitats in the future. The work is published in the journal Estuaries and Coasts. Seagrasses act as ecosystem engineers, creating complex underwater habitats that support life along the coast. Around the world, these habitats are increasingly threatened by climate change and human impacts like coastal development, invasive species and overfishing. While most West Coast seagrass research has focused on protected bays and estuaries, this study focused on open-coast areas off Catalina Island. Drawing on nearly a decade’s worth of surveys, the team examined everything from seagrass structure to fish communities and ocean conditions to identify where restoration might succeed. Juvenile señorita (Oxyjulis californica) utilize the protective canopy of the open-coast seagrass restoration site at Button Shell, Catalina Island. Credit Adam ObazaPaua Marine Research Group Two bat rays (Myliobatis californica) soaring over an open-coast eelgrass (Zostera marina) bed on Catalina Island. Credit Adam ObazaPaua Marine Research Group The results were encouraging, as the researchers completed the first transplant of open-coast common eelgrass (also known as Zostera marina). Within a year, the restored site began functioning like a natural meadow, supporting fish communities and ecosystem structure, and by year two, it was even healthier and more biodiverse than natural reference meadows. “Seagrasses are kind of an unsung hero of nearshore ocean habitats,” said Sanders. “They provide nursery habitat for young fish, store carbon in sediments and support immense biodiversity in places that might otherwise be sandy seafloor. Being able to quickly restore that structure and function on the open coast is really exciting.” The findings suggest that open-coast environments could become a valuable new tool for seagrass restoration and conservation in California, especially as coastal development and climate change reduce the available suitable habitat in bays and estuaries. And sometimes restoration has surprising benefits. During monitoring, researchers even captured images of an endangered sea turtle visiting the restored meadow. In short: if we plant seagrass, the ecosystem may follow. More information: This article is republished from PHYS.ORG and provided by the University of California – San Diego. Rilee D. Sanders et al, Open-Coast Eelgrass (Zostera marina) Transplant Catalyzes Rapid Mirroring of Structure and Function of Extant Eelgrasses, Estuaries and Coasts (2025). DOI: 10.1007/s12237-025-01609-x
The wellbeing benefits of nature are often linked to forests or habitats that support diverse pollinators. Spending time in green spaces reduces stress and anxiety, for example. By contrast, the benefits of the ocean are more commonly associated with fishing, exciting creatures such as whales and dolphins, or adventure watersports, rather than as a living system that directly supports human wellbeing. Yet growing scientific evidence shows that marine biodiversity is fundamental to the health of people, animals and the planet. The “one health” concept (a term now widely used by the World Health Organization) captures this connection by recognising that human health, animal health and environmental health are inseparable. Our new paper in the journal BioScience applies this idea to seagrass meadows for the first time. We argue that healthy coastal ecosystems such as seagrass meadows are not optional extras, but essential infrastructure for resilient societies. Coastal seas host some of the most biologically rich ecosystems on Earth. Kelp forests, oyster reefs, saltmarshes and seagrass meadows form the foundation of complex food webs that support fisheries, regulate water quality and protect shorelines. These habitats influence everything from food security and livelihoods to exposure to pollution and disease. Take seagrass meadows as one example. These underwater flowering plants stabilise sediments, reduce wave energy and filter nutrients from coastal waters. The benefits ultimately reduce coastal flooding and make the environment cleaner. They also support young fish and invertebrates that later populate offshore fisheries. Seagrass and water quality exist in a delicate balance. When the quality becomes too poor the seagrass becomes less abundant, and it’s then less able to act as a filter. This further exacerbates the water quality problems with implications for fish and other wildife. Similar patterns are seen when kelp forests collapse or shellfish reefs are lost. This is why we need better recognition for the important roles these habitats play. Marine biodiversity also helps regulate the Earth’s climate. Coastal habitats such as seagrass capture and store carbon and can reduce the negative effects of storms and flooding. While saving these ecosystems can’t replace the need to cut greenhouse gas emissions, their loss can accelerate climate impacts at local and regional scales increasing risks to coastal communities. Despite their importance, many marine ecosystems have been severely degraded. Pollution, overfishing, coastal development and warming seas have reduced biodiversity along coastlines around the globe. These losses are rarely visible to the public as they’re hard to see. This is because these losses occur underwater and gradually. Yet their consequences are increasingly felt through declining fisheries, poorer water quality and greater vulnerability to extreme weather. These factors all ultimately affect our health and wellbeing. Our new paper argues that restoring marine biodiversity requires a shift in how success is measured. Conservation and restoration efforts are often judged by the amount of hectares of habitat planting planted or short-term project outcomes. While these metrics are easy to calculate, they can obscure the real goal: the recovery of ecological function and long-term resilience. Biodiverse seagrass habitats have huge value to fisheries, from industrial fishing vessels to communities fishing by hand. Richard Unsworth A collaborative approach This is where the one health perspective becomes particularly valuable. By linking environmental condition to human and animal health, it encourages collaboration across disciplines that rarely interact. Coastal management, public health, fisheries policy and climate adaptation are often treated separately yet they all depend on the same underlying ecosystems. Examples from around the world show that biodiversity can do miraculous things, such as seagrass meadows trapping pathogens, reducing harmful bacteria in coastal waters that kills corals and contaminates seafood. That’s nature directly buffering human and animal health. We also know that when habitat is degraded and lost, it displaces associated wildife. This can lead to greater interactions between wild and farmed animals. In the case of seagrass loss, typically we know that geese become displaced to farmland to graze. This has the potential to increase interactions with farmed animals and could enhance spread of diseases such as bird flu. Recovery of our ocean habitats and the wildlife, plants and microbes that live there is possible. Where water quality improves and physical disturbance is reduced, marine habitats can rebound, bringing measurable benefits for biodiversity fisheries and coastal protection. Importantly, the benefits then extend to people – cleaner water, a more affable environment and better, more abundant food. However restoration of these habitats alone cannot compensate for ongoing damage. Protecting what remains is consistently more effective and less costly than rebuilding ecosystems after they collapse. Marine biodiversity may feel distant from everyday life but it quietly supports many of the systems that societies depend on. Recognising oceans and coasts as part of our shared health system rather than as separate from it could transform how we manage and value the marine environment. In a changing climate, this shift may prove essential not only for nature but for our own resilience. This article was originally published in The Conservation.
Extreme heat can have a devastating effect on seagrass, but new research from Edith Cowan University (ECU) could shape how these vitally important marine ecosystems are managed and restored. In separate studies carried out on both the west and east coasts of Australia, researchers have investigated how seagrasses stand up to marine heat waves and prolonged ocean warming. Executive Dean of ECU’s School of Science, Professor Marnie Campbell, conducted the research during her time at Central Queensland University. She noted that insights into how different intertidal species respond to elevated water temperatures are critical for informing future seagrass management. “The outcomes demonstrate that the way we protect and restore seagrass will need to change as the climate warms,” Professor Campbell said. Ph.D. candidate Nicole Said from ECU’s Center for Marine Ecosystem Research said that not all seagrass species faced the same climate risk, with her research findings on Western Australian seagrass ecosystems indicating that subtidal seagrass meadows could be restored with more heat-resistant populations of the same species. “By identifying and sourcing heat-tolerant populations—sometimes just kilometers away—we can translate this knowledge into on-the-ground action, incorporating resilient populations into restoration to create climate-ready meadows,” Ms. Said explained. West coast Ms. Said is lead author of the study “Seagrasses are most vulnerable to marine heat waves in tropical zones: local‐scale and broad climatic zone variation in thermal tolerances,” which looked at six species along the Western Australian coast, spanning broad thermal gradients from temperate to tropical climates. The study is published in the journal New Phytologist. “Western Australia is an ideal setting for studying seagrass thermal tolerances, and there is a critical need for this data due to WA being a global hotspot for marine climate impacts,” Ms. Said explained. “We can use this information to look at which species might be vulnerable during future marine heat waves, and which ones we should focus our conservation value on.” The study revealed that seagrasses are most vulnerable to marine heat waves in tropical zones. It also showed that climate risk varied across seagrass species, with a 10-degree Celsius difference in thermal optima, and even neighboring populations showed different heat tolerances. “Some populations are better equipped to deal with the heat, and in some cases, the tough ones might be growing next door,” Ms. Said explained. “This shows that not all species face the same level of risk from climate change, and a one-size-fits-all approach is not appropriate for management of thermally vulnerable seagrass species.” The findings could also benefit restoration of seagrass meadows that have already suffered from thermal warming and marine heat wave events. “We can use this information to help build climate-ready meadows, by migrating plants or seeds from more heat-resistant populations into thermally vulnerable areas.” East coast Professor Campbell’s study “Varying vulnerabilities: Seagrass species under threat from prolonged ocean warming” is a paper published in Limnology and Oceanography that examined the impacts of elevated water temperatures on five intertidal species in Gladstone, Queensland, with a focus on improving seagrass restoration. “This study offers an understanding of how climate change might impact these seagrasses, whose ecological functions are not easily replaced once lost,” Professor Campbell said. “Seagrasses are a critically important ecosystem that provides food, shelter and nursery areas for a wide variety of marine life, so with changing climate, it is at risk in different ways. We wanted to understand how these species react when temperatures reach dangerous extremes, which is becoming more common with climate change.” Professor Campbell said they found intertidal pools where the water was more than 40 degrees for weeks on end. “The tide would go out, and the seagrass would be left high and dry, quite often in little, tiny pockets of water which would reach massive temperatures,” Professor Campbell said. “To restore or manage the species, you have to look at the distinct thermal thresholds of the different species—you can’t treat them all as one. “This knowledge helps us to decide which species to plant where—including the best substrate and water depth; so we can restore these ecosystems more effectively.” Professor Campbell said the species she studied were commonly found in Australia and other parts of the world, with the outcomes leading to global impact. “There were two species that were really good candidates for future-proofing restoration in regions that are warming up,” Professor Campbell said. “Two were highly vulnerable and will require more protection from heat stress, or if you’re going to restore them, you need to find micro-climates that are cooler for them—for example, if they are in the sub-tropics, you would look at temperate areas to restore them.” More information: This article is republished from PHYS.ORG and provided by the Edith Cowan University. Nicole Said et al, Seagrasses are most vulnerable to marine heatwaves in tropical zones: local‐scale and broad climatic zone variation in thermal tolerances, New Phytologist (2025). DOI: 10.1111/nph.70742 Marnie L. Campbell et al, Varying vulnerabilities: Seagrass species under threat from prolonged ocean warming, Limnology and Oceanography (2025). DOI: 10.1002/lno.70156
Current estimates of the global extent of seagrass range from between 160,000-266,000km. Such a high degree of uncertainty presents challenges for researchers and managers and their ability to make informed decisions which account for the changing status of seagrass ecosystems. Key to improving our understanding of seagrass presence and absence, identified as one of the six Global Challenges facing effective seagrass conservation, is the collection and integration of interoperable data on seagrass extent. A new paper published in Bioscience from members of the Coordinated Global Research Assessment of Seagrass Systems working group outlines how the Seagrass Essential Ocean Variable can help us to address this challenge. This paper was co-written by members of our Project Seagrass team. Achieving our goals for seagrass conservation requires reliable information on the status and trends of seagrasses and the organisms that associate with them, yet seagrass variables measured and the methods for doing so vary widely across projects and organisations, presenting challenges for comparisons across studies. This new paper provides a global framework for seagrass monitoring as an Essential Ocean Variable of the Global Ocean Observing System, key to aligning seagrass researchers and managers around a common approach to seagrass monitoring. Implementing these guidelines will support the collection of more comparable, compatible, and combinable seagrass data. The Seagrass Essential Ocean Variable contains three priority measurements to maximise compatibility across data sets: Seagrass percentage cover Seagrass species composition (the identify and relative abundances of seagrass species in an area) Seagrass areal extent (the horizontal extent of seagrass at the meadow of seascape scale These three priority measurements collectively have been identified to provide the most useful assessment of seagrass status and change at landscape scales, addressing most scientific, management, and policy needs and targets. The Essential Ocean Variable also includes further supporting variables relating to biological and environment factors. Seagrass monitoring using SeagrassSpotter At Project Seagrass we’re well placed to contribute to this global process with our OpenAccess SeagrassSpotter.org platform collecting georeferenced data on seagrass percentage cover and species composition. In 2026 we will also be launching a complementary app called SeagrassTracker which will help scientists report, share, and archive data on seagrass spatial extent. These platforms are all linked to the Global Ocean Observing System. Key to the Seagrass Essential Ocean Variable is a commitment to collaborate. If utilised across widely, the EOV will support the creation of a growing resource of seagrass data that is maximally compatible and supports more reliable local research and better-informed management.
Ewan Garvey, one of Project Seagrass’ Interns for the 2025-26 academic year, explores how seagrass can provide protection for coastal communities. As the seasons transition from autumn into winter, storms often become a pressing concern for coastal communities. In recent years, the growing impacts of climate change have become increasingly clear: extreme weather events once considered “once-in-a-decade” now seem to strike far more frequently. In response, governments and communities are looking for protective solutions, investing heavily in sea defence systems, ranging from sandbags to seawalls. But what if nature has already developed a solution? Enter seagrass. Seagrass’s unique characteristics make it a powerful ally in protecting coastlines. Unlike concrete walls or other flood defence systems, seagrass meadows work with natural processes to reduce erosion and flooding, while also creating vital habitat for marine life. How Seagrass Protects Our Shores Root FixationMuch like how trees stabilise the soil in forests, seagrass root systems anchor sand and mud in place, reducing sediments from being washed away during storms. This helps to maintain the structure of beaches, providing more stable coastal habitats. Dissipation of Wave EnergyWhen waves pass over seagrass meadows, the blades create friction. This slows the water, disperses energy, and reduces the force that reaches the shoreline. This means water travels up the beach less and can lessen flooding events. Challenges Hard-engineered coastal defences such as rock armour can cost upwards of £1 million for just a 35-metre section. Seagrass restoration is also expensive, and to date has been largely funded through philanthropic and government funding mechanisms. Seagrass restoration is not without challenges; newly planted seeds are vulnerable to being washed away or buried by shifting sediment before they can properly establish. Seagrass also requires good water quality; too much pollution can prevent seedlings from developing. In many areas, improving river and coastal water quality must go hand in hand with restoration for projects to succeed. A Blended Solution Is seagrass the silver bullet for coastal protection? Not entirely. By blending natural and engineered approaches, we can create more sustainable, resilient coastlines—ones that not only protect us from storms but also support thriving marine ecosystems. Combining engineered solutions such as breakwaters or seawalls with seagrass meadows could reduce wave energy and sediment loss, which would lower the stress on the artificial defences. This could result in cheaper, smaller sea defence structures, reducing both environmental impact and cost. References and Extra Research “Seagrass as a nature-based solution for coastal protection” by Forrester, Leonardi, Cooper & Kumar (2024) Infantes et al. (2022) — Seagrass roots strongly reduce cliff erosion rates in sandy sediments Donatelli et al. (2018) — “Seagrass Impact on Sediment Exchange Between Tidal Flats and Salt Marsh, and The Sediment Budget of Shallow Bays” Bricheno, L. M., et al. “Climate change impacts on storms and waves relevant to the UK and Ireland.” MCCIP Science Review 2025 (2025).
Seagrass meadows have an important climate protection function due to their long-term carbon storage potential. An international research team led by the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) has now been able to show that seagrass beds have a stronger influence on the carbon and sulfur cycling in subtropical coastal areas than previously thought. Of particular interest is the important role of sulfur, which stabilizes organic carbon, regardless of whether it is sequestered in the calcareous sediments of subtropical seagrass meadows or remains in dissolved form. The results of the study were recently published in Communications Earth & Environment. Seagrass ecosystems are particularly worthy of protection as they provide shelter and food for a wide diversity of marine species and act as natural wave breakers that reduce coastal erosion. They also store so-called “blue carbon”—carbon that stays trapped in the ocean and in coastal ecosystems for a long time and therefore cannot have a climate-damaging effect as carbon dioxide (CO2). Seagrass not only stores carbon via photosynthesis in its plant components, but also buries the organic material of other organisms that accumulates in the dense plant cover in its root sediments. How do subtropical seagrass meadows ‘tick?’ “It has been known for some time that not all seagrass meadows ‘tick’ in the same way when it comes to carbon storage. Tropical and subtropical seagrass meadows in particular can sometimes release more carbon than they store,” says Mary Zeller. The marine chemist is an expert in biogeochemical seabed processes and lead author of the new study on the seagrass carbon cycle. “However, as seagrass meadows are particularly widespread in warm ocean regions, we wanted to take a close look at the processes that ultimately determine their carbon balance. This is the only way to correctly estimate their climate protection potential,” says the scientist, who now works at MARUM—Center for Marine Environmental Sciences at the University of Bremen, but was a researcher in IOW’s Geochemistry & Isotope Biogeochemistry working group during the seagrass study. Zeller and her German-American research team focused on subtropical seagrass beds located in Florida Bay in the south of the United States. In order to understand whether and how organic matter—and therefore carbon—is released from the sediments into the water column, they combined state-of-the-art geochemical and molecular methods to analyze sediments, pore water and the surrounding water. The focus of the involved IOW researchers Zeller and Michael Böttcher was to analyze various stable isotopes as biogeochemical markers to understand the complex matter transformation processes, as well as to employ a special method of high-resolution mass spectrometry, which allows the determination of the molecular formula of individual molecule types in complex mixtures of organic molecules. Porewater and sediment inorganic and stable isotope geochemical data. Credit: Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01832-7 Surprisingly close coupling of the sulfur and carbon cycles The researchers found that almost 10% of all organic matter of the investigated seagrass meadows is bound to their calcareous sediments. This type of sediment is a characteristic of tropical and subtropical seagrass ecosystems, because in the warm environment the metabolic processes of the seagrass plants cause carbonate, which is dissolved in the seawater, to be converted into lime that accumulates in the root area. If these sediments disintegrate, the bound organic substances can dissolve and enter the water column, making them potentially available again to the marine carbon cycle. “We were able to provide direct proof for the first time that seagrass sediments actually release organic carbon. In particular, our molecular analyses have shown that the dissolved organic molecules in the surrounding water correspond to 97% in structure and composition with the lime-associated organic material in the sediments,” Zeller explains. A crucial role in the mobilization of organic substances from the sediments is played by the sulfur chemistry in the seabed, which the seagrass meadows stimulate like a kind of biocatalyst: Their roots actively transport oxygen into the sediment, which facilitates the oxidation of sulfur compounds by microorganisms. This produces acid, which causes the calcareous sediments at the seagrass roots to partially disintegrate, releasing previously bound organic matter. Additionally, these microbial processes produce highly stable organic sulfur compounds that are largely resistant to biological decomposition and degradation by the UV radiation of sunlight. Improved modeling of the climate protection potential of seagrass “The fact that the sedimentary and dissolved carbon pools in seagrass meadows are so closely coupled was previously unknown and was therefore not adequately taken into account in climate modeling,” comments Zeller on the results of the study. “In this context, it is also important that although the organic sulfur generated in seagrass beds mostly exists in dissolved rather than particulate form, it is apparently still a very long-lived carbon reservoir that cannot be easily metabolized into climate-active CO2,” Zeller continues. According to the marine chemist, the study could help to improve modeling of the “blue carbon” storage potential of the widespread tropical and subtropical seagrass meadows. “However, further research is needed to clarify whether the mechanisms found here are universal—i.e., whether they also apply to other ecosystems with similar rhizosphere processes, such as mangroves. It also needs to be clarified whether and what kind of impact environmental changes such as climate change have on these processes,” concludes Zeller. More information: Mary A. Zeller et al, The unique biogeochemical role of carbonate-associated organic matter in a subtropical seagrass meadow, Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01832-7 This article is republished from PHYS.ORG and provided by Leibniz-Institut für Ostseeforschung Warnemünde.
A major global study using teabags as a measuring device shows warming temperatures may reduce the amount of carbon stored in wetlands. The international team of scientists buried 19,000 bags of green tea and rooibos in 180 wetlands across 28 countries to measure the ability for wetlands to hold carbon in their soil, known as wetland carbon sequestration. While tea bags may seem an unusual instrument to measure this phenomenon, it is a proven proxy method to measure carbon release from soil into the atmosphere. However, this is the first time teabags have been used for a large-scale, long-term study and the tea leaves have revealed which types of wetlands are leaking the most carbon. RMIT University’s Dr. Stacey Trevathan-Tackett led the study as part of an Australian Research Council DECRA Fellowship while at Deakin University. “Climate effects on belowground tea litter decomposition depend on ecosystem and organic matter types in global wetlands” is published in Environmental Science and Technology. The global study involved 110 co-authors on the paper, along with many others who helped, such as undergraduate students and citizen scientists. Core team members included Dr. Martino Malerba and Professor Peter Macreadie from Deakin University and RMIT, Dr. Sebastian Kepfer-Rojas from the University of Copenhagen in Denmark and Dr. Ika Djukic from The Swiss Federal Institute for Forest, Snow and Landscape Research WSL. “This is the first long-term study of its kind, using this teabags method, which will help guide how we can maximize carbon storage in wetlands and help lower emissions globally,” said Trevathan-Tackett, who is now in RMIT’s School of Science. “Changes in carbon sinks can significantly influence global warming—the less carbon decomposed means more carbon stored and less carbon in the atmosphere.” Map of TeaComposition H2O sites across eight macroclimatic zones. Credit: Environmental Science & Technology (2024). DOI: 10.1021/acs.est.4c02116 Reading the tea leaves Tea bags provide a simple and standardized way to identify how climate, habitat type and soil type influence carbon breakdown rates in wetlands. At each site, scientists buried between 40 and 80 tea bags about 15 cm underground and collected these at various time intervals over three years, tagging their GPS location. They then measured their remaining organic mass to assess how much carbon had been preserved in the wetlands. The project used the two types of tea bags (green and rooibos) as measures for different kinds of organic matter found in soils. Green tea consists of organic matter that decomposes easily, whereas rooibos decomposes more slowly. Using both types of tea bags in this project enabled the researchers to gain a more comprehensive picture of the wetlands’ capacity for carbon storage. “This data shows us how we can maximize carbon storage in wetlands globally,” Trevathan-Tackett said. The Findings The team studied the effect of temperature in two ways: using local weather station data for each site and comparing differences in climate regions. “Generally, warmer temperatures led to increased decay of organic matter, which translates to reduced carbon preservation in soil,” Trevathan-Tackett said. The two tea types acted differently with increasing temperature. “For the harder to degrade rooibos tea, it didn’t matter where it was—higher temperature always led to more decay, which indicates that types of carbon we’d typically expect to see last longer in the soil were vulnerable to higher temperatures,” Trevathan-Tackett said. “With increasing temperatures, the green tea bags decayed at different rates depending on the type of wetland—it was faster in freshwater wetlands but slower in mangrove and seagrass wetlands. “Increasing temperatures may also help boost carbon production and storage in plants, which could help offset carbon losses in wetlands due to warmer weather, but this warrants further investigation with future studies.” Freshwater wetlands and tidal marshes had the highest tea mass remaining, indicating a greater potential for carbon storage in these ecosystems. The study’s findings are helping piece together the puzzle of wetland carbon sequestration on a global scale. Within the terrestrial TeaComposition initiative led by Djukic, information on litter decomposition has been collected at about 500 sites worldwide resulting in several peer-review publications. “Applying the common metric across aquatic, wetland, marine and terrestrial ecosystems allows for a conceptual comparison and understanding of key drivers involved in the control of global litter carbon turnover,” Djukic said. “Now that we are starting to get a better understanding of which environments are storing more carbon than others, we can use this information to ensure we protect these areas from environmental or land-use change.” The researchers will combine the data from this project with data from similar studies of land-based carbon sinks, including forests, to inform designs of predictive global models. More information: Stacey M. Trevathan-Tackett et al, Climate Effects on Belowground Tea Litter Decomposition Depend on Ecosystem and Organic Matter Types in Global Wetlands, Environmental Science & Technology (2024). DOI: 10.1021/acs.est.4c02116 This article is republished from PHYS.ORG and provided by RMIT. Explore our blog for insights on the latest research from across the globe. Click here
