Dead leaves in sea break down into a compost that produces oxygen
October 11, 2024 Researchers from the University of Liège (BE) studied the fate of the material produced by Posidonia seagrass meadows. This study, carried out in the Mediterranean Sea at STARESO, shows that the dead leaves of what is commonly known as Neptune grass accumulate in shallow areas, where they break down like a compost, remineralizing the organic matter. This has a previously underestimated effect on carbon fluxes in the Mediterranean coastal environments. Surprisingly, alongside this CO2 emission, oxygen production was also measured. This is linked to the presence of photosynthetic organisms living in this compost in the sea, which fundamentally differentiates it from compost on land. The work is published in the journal Estuarine, Coastal and Shelf Science. From left to right: View of the STARESO harbor entrance with Posidonia meadow islands and an accumulation of dead leaves. Close-up of litter accumulation. Experimental benthic incubation device (‘bell’) installed on accumulations of Posidonia dead leaves (10 m deep). Credit: G.Lepoint & W. Champenois / ULiège Posidonia, a flowering plant emblematic of the Mediterranean Sea, commonly known as Neptune grass, forms vast meadows (underwater prairies) in shallow waters (less than 40m deep). “It is a terrestrial plant that recolonized the marine environment several million years ago, a small quirk of evolution,” explains Alberto Borges, an oceanographer at ULiège. “Like most terrestrial plants in our regions, Posidonia loses its oldest leaves in autumn. These dead leaves accumulate as litter (like at the base of trees) in large patches near the seagrass meadows.” It is these accumulations of dead leaves and their breakdown and transformation that interested the researchers who traveled to STARESO, an underwater and oceanographic research station located in Calvi, Corsica, to conduct a study on the primary production and degradation of organic matter in Posidonia litter. “In the litter, the organic matter breaks down and releases nutrients and CO2, like compost in gardens,” explains Gilles Lepoint. “The litter accumulates in open, sun-light areas.” “Every gardener knows that to grow plants, you need nutrients and light. It is on this basis that we conducted our study which led to a surprising first result: in the litter resulting from the accumulation of material that one would initially imagine as dead and inert, we measured oxygen production, a consequence of the photosynthetic activity of macroalgae drifted from rocks, living Posidonia shoots detached from the nearby meadow, and diatoms (microscopic algae) present in the litter.” To summarize, in this nutrient-rich environment, all living plants associated with the litter thrive and photosynthesize. This oxygen production is significant but does not offset the oxygen consumption by the decomposition of the dead leaves. These accumulations, therefore, remain net consumers of oxygen and, consequently, net emitters of CO2, much like compost and litter in terrestrial environments. The second result from this study somewhat surprised the researchers. “While we thought that Posidonia litter degraded relatively quickly, this study showed us the opposite, based on measurements of litter mass loss—it degrades more slowly,” says Alberto Borges. “We measured respiration through short-term (1-day) incubations based on very precise oxygen measurements.” These measurements provided a more realistic and accurate estimate, with lower values than those traditionally obtained by monitoring mass loss over very long periods (several months). This result could modify the current carbon balance calculations for these ecosystems, which are based on traditional mass loss measurements. As part of this study, the researchers also examined the primary production and degradation of organic matter from the macroalgae growing on rocks adjacent to the Posidonia meadows. “We hypothesized that there might be exchanges between the two systems, which one might initially imagine to be separate and compartmented. Once again, we obtained an unexpected result,” says Willy Champenois. “These macroalgae, despite undergoing photosynthesis, were net consumers of oxygen rather than net producers. This means that the communities of bacteria and invertebrates living within the algae community consume more organic matter than the algae produce. This necessarily implies that this excess organic matter must come from an external source.” By calculating a mass balance, the researchers concluded that this excess organic matter was likely provided by the Posidonia in the form of dissolved organic molecules diffusing from the seagrass meadow and litter to the rocks. In summary, there is a two-way exchange between the macroalgae on the rocks and the Posidonia meadows. The macroalgae drifting from the rocks can accumulate in the Posidonia litter and contribute to primary production there. In turn, the seagrass can supply organic molecules that diffuse to the rocks and are assimilated by the bacterial communities associated with the macroalgae on the rocks. A mutually beneficial relationship, indeed. This study provides new insights into the quantification and understanding of the organic carbon balance of Posidonia seagrass meadows in the Bay of Calvi, which has been the subject of research by oceanographers and marine biologists at the University of Liège since the 1980s, notably through the STARESO marine research station. More information:W. Champenois et al, Community gross primary production and respiration in epilithic macroalgae and Posidonia oceanica macrophytodetritus accumulation in the Bay of Revellata (Corsica), Estuarine, Coastal and Shelf Science (2024). DOI: 10.1016/j.ecss.2024.108971 This article is republished from PHYS.ORG and provided by the University of Liège. Explore our blog for insights on the latest research from across the globe. Click here
Sentinel-2 data reveal significant seasonal variations in intertidal seagrass
October 7, 2024 With data from the Copernicus Sentinel-2 mission, researchers have revealed seasonal variations in intertidal seagrass across Western Europe and North Africa. As a key indicator of biodiversity, these new findings offer valuable insights for the conservation and restoration of these vital ecosystems. The intertidal zone is the area where the ocean meets the land between high and low tides, and here seagrasses can form extensive meadows. These flowering marine plants provide critical habitats, acting as shelter, nurseries, and feeding and spawning grounds for a diverse range of birds, fish and invertebrates. Beyond their ecological importance, seagrass meadows also stabilize sediments and protect coastlines from erosion. Monitoring the occurrence, extent, condition and diversity of intertidal seagrass as a key biodiversity variable is essential for assessing the overall health of local ecosystems. Current global estimates of seagrass coverage do not differentiate between seagrasses in the intertidal zone and those in the subtidal zone, which remain submerged below the sea surface. However, a recent paper, published in Communications Earth & Environment, details how a team of scientists used high-resolution imagery from the Copernicus Sentinel-2 mission to demonstrate its ability to map intertidal seagrass meadows and their seasonal changes across continents with consistency and precision. Bede Ffinian Rowe Davies from Nantes University in France and lead author of the paper, said, “Coastal regions, like much of the world, are experiencing rapid and alarming biodiversity loss. To address this, it’s crucial to develop efficient monitoring methods so that timely and appropriate action can be taken to preserve delicate ecosystems. “Using data from Sentinel-2 within the BiCOME project, we were able to reveal significant seasonal variations in intertidal seagrass. The peaks in extent shifted by as much as five months—challenging previous assumptions that there was little or no seasonal fluctuation.” The satellite images below illustrate changes in intertidal seagrass cover in the Bay of Bourgneuf, located north of the Bay of Biscay, off the western coast of France. The image on the left, from April 2021, shows sparse intertidal seagrass, while the image on the right, from September 2021, reveals abundant growth. Victor Martinez-Vicente, BiCOME project principal investigator, noted, “This study demonstrates the potential of satellite observations to track changes in the extent of natural coastal ecosystems, providing valuable insights for indicators in the Global Biodiversity Framework. Further research is needed to develop long-term satellite-based monitoring systems and datasets to support global progress toward achieving the framework goals.” ESA’s Marie-Helene Rio added, “These new findings clearly demonstrate the value that Sentinel-2 can bring to monitoring intertidal seagrass. We now believe that these intertidal meadows behave differently to the type of seagrass that spends most of its life submerged by seawater. This suggests that previous estimates, which grouped the two types together, could be misleading. The research paves the way to further monitoring and assessment of intertidal seagrass meadows using Sentinel-2 data.” The Sentinel-2 satellites each carry a multispectral imager that takes high-resolution images of Earth’s land, islands, and inland and coastal waters. And with a large swath width of 290 km, it provides these images in 13 spectral bands with resolutions of 10 m, 20 m and 60 m. The third Sentinel-2 satellite, Sentinel-2C, was launched on 5 September 2024, and has already delivered its first images of Earth. More information: Bede Ffinian Rowe Davies et al, A sentinel watching over inter-tidal seagrass phenology across Western Europe and North Africa, Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01543-z This article is republished from PHYS.ORG and provided by the European Space Agency. Explore our blog for insights on the latest research from across the globe. Click here
Invasive seagrass species discovered in Biscayne Bay
September 9, 2024 An invasive species of seagrass has been on a steady march across the world, taking over ecosystems well beyond its native waters of the Red Sea, Persian Gulf and Indian Ocean. Scientists have long wondered when it would reach the waters off the coast of Florida. Florida International University scientists say that day has arrived. Florida International University marine scientist Justin Campbell has positively identified Halophila stipulacea growing in Crandon Marina and nearby areas of Biscayne Bay. It is the first time this non-native species has been found in waters along the continental United States. The study appears on the preprint server bioRxiv. “I think this species could pose a considerable threat,” Campbell said. “There are several reports of it being able to outcompete native seagrasses in other areas across the Caribbean. It is plausible that this could also be true for seagrasses here in South Florida.” A marina worker first noticed the seagrass last month and reached out to Campbell, who conducted tests to determine the species. Halophila stipulacea first started spreading its distribution with the opening of the Suez Canal in the late 1800s, hitching rides on the anchors and other parts of boats. By the early 2000s, it was found in the Caribbean. Field photographs of H. Stipulacea inside Crandon Marina (Key Biscayne, Florida) (a,b). Close-up detail of samples collected inside the marina, structure and leaf cross veins (c,d). Credit: Matthew White (a,b) and Justin Campbell (c,d). Healthy seagrass meadows are vital for healthy oceans. They are nursery habitats for commercially and economically important fish as well as shrimp, stone crabs, scallops and other crustaceans and shellfish. Seagrasses are a primary food source for sea turtles, manatees and other marine herbivores. And for the health of the planet, seagrasses are really good at sucking carbon emissions out of the air and storing that carbon long-term. While scientists are still working to understand possible impacts from the invasive species entering waters around the U.S., early research suggests some fish species may avoid the shorter seagrass when scouting nursery locations and local sea turtles in the Caribbean avoid eating the invasive seagrass, preferring native species as part of their regular diets. While most species of seagrass are on the decline from warming waters and other human-induced impacts, Halophila stipulacea has the unique ability to grow quickly and adapt to different conditions including salinity levels, temperature and light availability. Just a small piece can float through water and grow. Once it settles into soil, it can take hold easily and grow at a variety of depths. While most seagrass species require shallower depths to attain sunlight, Halophila stipulacea has been observed flourishing at depths of 60 feet or more. “The arrival of yet another invasive species to Florida is a reminder that all of our earth is interconnected and that human actions have the power to change the planet, for good or bad,” said James Fourqurean, co-author of the research and director of the Coastlines and Oceans Division in FIU’s Institute of Environment. Fourqurean has studied seagrasses, especially those in Florida, for more than 40 years. A foremost expert, he is one of the lead scientists in the International Blue Carbon Working Group, as well as scientific representative to the International Blue Carbon Policy Working Group—both dedicated to the recognition and preservation of seagrass meadows, mangroves and tidal salt marshes as critical contributors to slowing the rise of CO2 in the atmosphere. “Given the importance of seagrasses to a healthy South Florida, we now need to do what we can to limit the spread of this invasive species and be wary of disruptions to the natural order it may cause,” Fourqurean said. Stipulacea has a very different appearance and structure than the native seagrasses in South Florida and throughout the Caribbean. At least 19 Caribbean islands have reported this seagrass growing in nearby waters and, in some cases, overtaking meadows of native grass. “We don’t know whether Stipulacea provides similar ecological benefits as compared to our native species,” Campbell said. “Our seagrass meadows here are some of the most pristine and well-protected in the Western Hemisphere. They are iconic and emblematic. We certainly don’t want to lose them.” So how long has this non-native species been in South Florida? It is hard for Campbell to say, but based on the current distribution, he believes it first started taking root several years ago. It had gone unnoticed because, to the casual observer, it can be difficult to distinguish from native vegetation, he said. Crandon Marina can accommodate medium and large sized sailboats, likely capable of travel to and from areas where Stipulacea is well-established. This is one possible and likely way the non-native seagrass reached Biscayne Bay. With other large marinas in the region, Campbell said surveys and monitoring should be expanded now that this invasive species is confirmed to be in South Florida. More information:Justin E. Campbell et al, First record of the seagrass Halophila stipulacea (Forskkal) Ascherson in the waters of the continental United States (Key Biscayne, Florida), bioRxiv (2024): DOI: 10.1101/2024.09.02.610701 This article is republished from PHYS.ORG and provided by the Florida International University. Explore our blog for insights on the latest research from across the globe. Click here
Scientists and rangers share knowledge to restore seagrass
August 14, 2024 Scientists from The University of Western Australia have partnered with Indigenous rangers on a seagrass restoration project in Gathaagudu (Shark Bay) to help moderate climate change and conserve biodiversity. Dr. Elizabeth Sinclair and Professor Gary Kendrick, from UWA’s School of Biological Sciences and Oceans Institute, were co-authors of the paper published in Ocean & Coastal Management. “Solutions that integrate western science and Traditional Ecological Knowledge are key to improving restoration outcomes,” Dr. Sinclair said. Researchers partnered with Malgana Aboriginal Corporation Rangers on a program that included On Country workshop-based knowledge sharing in north-west Western Australia, with a focus on seagrass restoration. Malgana Elder, Auntie Pat Oakley said managing and caring for a living and dynamic Country are at the heart of well-being for all Indigenous Peoples. “The global rate of seagrass decline continues largely due to human activities, including the widespread impacts from climate change,” Professor Kendrick said. “Reversing this decline by restoring seagrass ecosystems and the benefits they provide is challenging and can take decades, even when human impacts are reduced.” The program found with the right resourcing and logistics, there are opportunities to support training workshops that develop expertise in seagrass restoration activities in Shark Bay. Sean McNeair, Malgana man and ranger coordinator, said field-based restoration workshops helped people reconnect with Country through two-way knowledge sharing. “We need to empower the Malgana Aboriginal Corporation Rangers and local Indigenous-led businesses to schedule restoration activities that help build seasonal local economies and increase the ability to restore seagrass at larger scales,” Dr. Sinclair said. More information: Elizabeth A. Sinclair et al, Healing country together: A seagrass restoration case study from Gathaagudu (Shark Bay), Ocean & Coastal Management (2024). DOI: 10.1016/j.ocecoaman.2024.107274 Journal information can be found here: Ocean and Coastal Management This article is republished from PHYS.ORG and provided by the University of Western Australia.
Seagrasses filter human pathogens in marine waters
August 14, 2024 An international team of researchers discovered that coastal urban seagrass ecosystems can significantly reduce human bacterial pathogens, including those with widespread antibiotic resistance, in marine bivalves—a vital food source for people around the world. The study, published Aug 2 in the journal Nature Sustainability, sheds light on the significant role seagrass meadows play in their ecosystems. Not only do they serve as crucial habitats for marine life and contribute to biodiversity and clearer waters, but they also act as natural filtration systems, reducing bacterial pathogens in the surrounding waters. This is important because the current economic burden of human infectious diseases in marine environments is estimated at $12 billion annually. Furthermore, the looming threat of antimicrobial resistance, projected to cause over 300 million deaths and cost the global economy $100 trillion, underscores the urgency of such natural interventions. “Our paper presents the first evidence that coastal urban seagrass ecosystems can reduce human bacterial pathogens, several with known widespread antibiotic resistance, in a food source that has the potential to support over half of global seafood production and consumption,” said Joleah Lamb, assistant professor at the University of California, Irvine, Charlie Dunlop School of Biological Sciences, who led the research with Drew Harvell, professor emerita of ecology and evolutionary biology at Cornell. The team analyzed mussels deployed by Washington’s Department of Fish and Wildlife Mussel Watch across 20 Puget Sound beaches with varying seagrass presence. Mussel gills from locations with seagrass showed a 65% reduction in bacterial pathogens compared with those from places without seagrass. Phoebe Dawkins performs seagrass health surveys in Puget Sound. Credit: Cornell University This study adds to Lamb and Harvell’s previous work showing 50% reductions in pathogenic bacteria in Indonesia seagrass meadows, and suggests that intact seagrass ecosystems in both tropical and temperate waters could play a vital role in ensuring safer seafood and enhancing public health. “Seagrasses have untapped potential to contribute to the chain of survival for humans and our coastal biodiversity,” Harvell said. “Seagrass meadows are prime feeding grounds for wild birds and shelter crabs, oysters, mussels and sea stars, and so the role of lower bacteria has yet unmeasured benefit for wildlife as well as humans.” Harvell’s Cornell research team of postdocs, graduate students and undergraduates has been studying the health of seagrass and drivers of decline in the San Juan Islands and Friday Harbor Labs for over a decade. The Cornell-based research team for this project included not only Lamb, but also Phoebe Dawkins, then a graduate student in Harvell’s lab, and undergraduate Evan Fiorenza ’17. The potential applications of this research are vast, Lamb said. As global food demand accelerates, securing safe and sustainable seafood from a healthy ocean is critical. Seagrass meadows, which are already recognized for their high-value services such as nutrient cycling, carbon sequestration and shoreline protection, now present an added layer of public health benefits. The study’s model estimates that 1.1 billion people currently live within 50 kilometers of seagrass ecosystems, highlighting the immediate opportunity to integrate these natural infrastructures into urban planning and conservation strategies. This research aligns with numerous global sustainability initiatives, including the U.N. Decade of Ocean Science for Sustainable Development and the U.N. Decade on Ecosystem Restoration. It provides timely evidence to inform policies and commitments aimed at reversing the decline of seagrass ecosystems, which are disappearing at an alarming rate of 7% per year. The study’s implications extend beyond immediate public health benefits, Lamb said, offering a blueprint for sustainable urban development that leverages nature’s powers to address global challenges. Lamb has called for a concerted effort from policymakers, urban planners and conservationists to recognize and harness the benefits of seagrass ecosystems. “As ecosystems continue to decline globally, there is an urgent need to invest in environmental conservation and assess the value of ecosystem services,” she said. “By doing so, we can make significant strides in addressing the biodiversity and climate crises while simultaneously improving human health and food security.” This research was supported by the Sea Doc Society, a program of the Karen C. Drayer Wildlife Health Center at the School of Veterinary Medicine at the University of California, Davis; the University of California, Irvine; and The Nature Conservancy. Credit: Video produced by Bob Friel and the SeaDoc Society. Narrated by SeaDoc Society Science Director Joe Gaydos. More information: Phoebe D. Dawkins et al, Seagrass ecosystems as green urban infrastructure to mediate human pathogens in seafood, Nature Sustainability (2024). DOI: 10.1038/s41893-024-01408-5 Journal information: Nature Sustainability This article is republished from PHYS.ORG and provided by the Cornell University.
Study projects loss of brown macroalgae and seagrasses
July 1, 2024 Researchers predict that climate change will drive a substantial redistribution of brown seaweeds and seagrasses at the global scale. The projected changes are alarming due to the fundamental role of seaweeds and seagrasses in coastal ecosystems, and provide evidence of the pervasive impacts of climate change on marine life. In a collaborative study between the University of Helsinki and the EU Joint Research Centre, researchers for the first time have modeled the future distribution of brown seaweeds and seagrasses at the global scale. They predict that by 2100, climate change will drive a substantial redistribution of both groups globally: Their local diversity will decline by 3–4% on average and their current distribution will shrink by 5–6%. More notably, the preferred habitat for both brown seaweeds and seagrasses will undergo a substantial global reduction (78–96%) and will shift among marine regions, with potential expansions into Arctic and Antarctic regions. The research is published in the journal Nature Communications. “We find it alarming that coastal areas worldwide will become dramatically less hospitable for habitat-forming macrophytes, as this might have severe and widespread impacts on coastal ecosystem functioning at the global scale. Interestingly, while global percentual declines in diversity show similar trends for seagrasses and brown macroalgae, the regional patterns are strikingly different between the two groups,” says Federica Manca, the lead author of the study from the University of Helsinki. Present distribution and projected end-of-century changes in global macrophyte species diversity. Credit: Nature Communications (2024). DOI: 10.1038/s41467-024-48273-6 Why should we care about seaweeds and seagrasses? Brown seaweeds and seagrasses provide important ecological and socio-economic services in coastal areas worldwide. They support coastal biodiversity and fisheries, ensure coastal protection, participate in ocean nutrient recycling, contribute to carbon sequestration and climate change mitigation. As climate change is severely threatening macrophyte habitats and the services they provide, we urgently need to understand how both brown seaweeds and seagrasses will respond to changing climatic conditions in the coming decades. Previous studies have modeled the future distribution of these habitat-forming macrophytes, focusing on regional or local scales only and on a limited number of species. In contrast, this study is the first to provide a comprehensive view of the effects of climate change on more than 200 species of brown seaweeds and seagrasses at the global scale. The results show that the redistribution of these habitat-forming marine macrophytes will be geographically heterogeneous, and highlight the regions where the loss of macrophyte diversity and habitat will be most severe, such as the Pacific coast of South America for brown seaweeds, and the coast of Australia for seagrasses. Additionally, researchers have identified macrophyte species that will be more severely affected by climate change, like the Atlantic seaweed Laminaria digitata. The findings can help identify target areas and species for conservation, potentially buffering the impact of climate change. Surprisingly, and contrary to expectations, the models did not predict severe losses of brown seaweed or seagrass diversity in the tropics but rather at intermediate and high latitudes, such as along the Atlantic coasts of Europe and in the Baltic Sea. This indicates that end-of-century climatic conditions in these regions might exceed the tolerance limits of resident macrophyte species. The Baltic Sea is at the forefront in the rate at which climate change is influencing the ecosystem. “Combined with a legacy of multiple other disturbances (such as eutrophication) and low species diversity with only a few brown seaweeds and seagrasses, the Baltic Sea is exceptionally vulnerable to these predicted changes,” says Alf Norkko, professor at the Tvärminne Zoological Station, University of Helsinki. “Another surprising—and alarming—result is the dramatic loss of highly suitable habitat for both macroalgae and seagrasses globally: Coastal areas worldwide will become substantially less hospitable for habitat-forming macrophytes,” adds Dr. Mar Cabeza from the Global Change and Conservation Group at the University of Helsinki. The disappearance of these habitat-forming macrophytes can trigger cascading effects on other species, compromising the integrity of entire ecosystems and undermining ecological and socio-economic services important to human society. Thus, forecasting changes in the distribution of habitat-forming species is crucial to raise awareness of climate change impacts and foster conservation efforts accordingly. “Our findings confirm, once again, that climate change might have profound impacts on ecosystems, promoting rapid and most often detrimental changes to the diversity and resilience of natural communities. In fact, habitat-forming macrophytes support biodiversity through an exceptional diversity of ecological interactions.” “Hence, their projected loss and redistribution might lead to unpredictable cascading effects, most likely resulting in the local extinction of many associated species,” says Giovanni Strona from the EU Joint Research Centre. More information: Federica Manca et al, Projected loss of brown macroalgae and seagrasses with global environmental change, Nature Communications (2024). DOI: 10.1038/s41467-024-48273-6 This article is republished from PHYS.ORG and provided by the University of Helsinki.
Seagrass clone in the Baltic sea is more than 1,400 years old
June 24, 2024 Using a novel genetic clock, a team of researchers from Kiel, London, Oldenburg, and Davis, California, has determined the age of a large marine plant clone for the first time. This seagrass clone from the Baltic Sea dates back to the migration period 1,400 years ago. The newly developed clock can be applied to many other species, from corals and algae to plants such as reeds or raspberries. The scientists have published their work in the journal Nature Ecology and Evolution. “Vegetative reproduction as an alternative mode of reproduction is widespread in the animal, fungal, and plant kingdoms,” explains research leader Dr. Thorsten Reusch, Professor of Marine Ecology at the GEOMAR Helmholtz Centre for Ocean Research Kiel. These so-called “clonal species” produce genetically similar offspring by branching or budding and often reach the size of a football field or more. However, these offspring are not genetically identical. (a), Multicellular clonal species exist across the tree of life. (b), Allele frequency change of SoGV due to the formation of new modules by branching or splitting. A new module is initiated either directly by the stem cells (that is, splitting) or by the daughter cells of the stem cells (that is, branching). Splitting reduces the size of the original stem cell population, while branching leaves the original cell population untouched. During the formation of new modules, the cell population undergoes a genetic bottleneck. c,d, The accumulation rate of fixed SoGV is independent of module formation rate. The tree topology depicts a module undergoing (multiple) module formation events, where the dashed line and the solid line represent the original module and the new module respectively. New mutations (M) occur at a constant rate, and only mutations in the new modules are depicted (with a different colour). For each timepoint, the vertical length of the colours represents the frequency of the SoGV within the module. Clonal dynamics in a single module (solid line in tree structure) are depicted as a Muller plot that shows the nested allele frequency of SoGV over time. The frequency of SoGV changes during module formation events, due to the bottleneck. Eventually, SoGVs are either fixed or lost. Under low module formation rate (c), fixation events are rare. Thus, many SoGVs have accumulated in the intervening time and are fixed simultaneously. Under high module formation rate (d), fixation events occur more frequently, but with fewer SoGVs fixed at each branching event. CREDIT: Nature Ecology & Evolution (2024). DOI: 10.1038/s41559-024-02439-z Previous work by a team led by GEOMAR researchers had already shown that somatic mutations accumulate in vegetative offspring, a process similar to cancer. Now, a team led by Prof. Dr. Reusch, Dr. Benjamin Werner (Queen Mary University London, QMUL), and Prof. Dr. Iliana Baums (Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg, HIFMB) has used this mutation accumulation process to develop a novel molecular clock that can determine the age of any clone with high precision. Researchers at the University of Kiel, led by Professor Reusch, applied this novel clock to a worldwide dataset of the widespread seagrass Zostera marina (eelgrass), ranging from the Pacific to the Atlantic and the Mediterranean. In Northern Europe in particular, the team found clones with ages of several hundred years, comparable to the age of large oak trees. The oldest clone identified was 1402 years old and came from the Baltic Sea. This clone reached this advanced age despite a harsh and variable environment. This makes the eelgrass clone older than the Greenland shark or the Ocean Quahog, which live only a few hundred years. These new age and longevity estimates for clonal species fill an important knowledge gap. Particularly in marine habitats, many fundamental habitat-forming species such as corals and seagrasses can reproduce vegetatively, and their clones can become very large. The continuous production of small, genetically identical but physically separated shoots or fragments from the parent clone means that age and size are decoupled in these species. The new study now provides a tool to date these clones with high accuracy. “Such data are, in turn, a prerequisite for solving one of the long-standing puzzles in conservation genetics, namely why such large clones can persist despite variable and dynamic environments,” says Reusch. Once a high-quality eelgrass genome was available, work could begin. Another key factor in the study was that colleagues at the University of California, Davis (UC Davis) had kept a seagrass clone in their culture tanks for 17 years, which served as a calibration point. “This paper shows how interdisciplinary interactions between cancer evolutionary biologists and marine ecologists can lead to new insights,” says Dr. Werner, Lecturer in Mathematics and Cancer Evolution at QMUL, who focuses on the somatic evolution of tumors which also develop clonally. Prof. Dr. Baums, molecular ecologist at the HIFMB, adds, “We can now apply these tools to endangered corals to develop more effective conservation measures, which we urgently need as unprecedented heat waves threaten coral reefs.” “We expect that other seagrass species and their clones of the genus Posidonia, which extend over more than ten kilometers, will show even higher ages and thus be by far the oldest organisms on Earth,” says Reusch. These will be the next objects of study. More information: Lei Yu et al, A somatic genetic clock for clonal species, Nature Ecology & Evolution (2024). DOI: 10.1038/s41559-024-02439-z This article is republished from PHYS.ORG and provided by Helmholtz Association of German Research Centres
Restoring the land to restore the sea
June 4, 2024 Benjamin Jones Chief Conservation Officer This year’s World Environment Day campaign focuses on land restoration, under the slogan “Our land. Our future. We are #GenerationRestoration.” Loss and degradation of coastal marine ecosystems, compromise the delivery of important ecosystem services to human society. Yet turning the tide on these losses and working towards a net gain in biodiversity is a challenge, not least because coastal marine ecosystems are exposed to threats occurring both in the ocean and on land. Land use change, through conversion of native terrestrial vegetation for agriculture, urbanization, and industry increases runoff and sedimentation, causing degradation of coastal ecosystems such as seagrass meadows. Swathes of evidence from across the globe reveal that anthropogenic activities from the land are some of the largest drivers of seagrass loss. For example, research from the Philippines has revealed that land use is more important than marine protection for tropical seagrass condition, and our own research has revealed the agricultural drivers of seagrass degradation across the British Isles. Yet for the most part, conservation prioritisation for coastal ecosystems is traditionally centred around protecting intact habitats from ocean-based stressors (e.g., fishing). If we are to conserve seagrass, we need to look beyond the ocean, and to the land. And this year’s World Environment Day is a key reminder of that. To conserve seagrass, should we be protecting habitat on land, protecting habitat in the ocean, restoring habitat on land, restoring habitat in the ocean, or a mixture of these actions? Answering this question is extremely difficult, not least when data is absent, histories of change are blurred, priorities for monitoring and management change and the nature and extent of threats to seagrass are unknown. In these instances, we believe that it is vital to understand which threats local stakeholders observe or perceive as being most persistent. Interweaving indigenous and local knowledge, and other expert witness knowledge as alternative data sources, is key. Our land. Our future. Seagrass meadows in the Wakatobi National Park (WNP), Indonesia are exploited for their rich fish and invertebrate communities – faunal communities that provide food security and livelihoods across the National Parks islands. Yet, with a growing population, the area of seagrass habitat is decreasing, and plant species composition and health is declining. Working with our local partner, FORKANI, and after a series of focus groups with local stakeholders, it seemed clear that the issue and threat they felt was most dominant, was sedimentation; the removal of mangroves and primarily forest areas had lessened the ability for land to absorb and store water. Built on indigenous and local knowledge, FORKANI, in collaboration with Project Seagrass, developed an incentives programme designed to provide fruit trees to farmers and landowners to facilitate stabilisation of river banks and reduce sediment deposition to the coast and at the same time improve the continually worsening problem of water storage. Now, over 5000 trees have been planted along riverbanks across the National Park by FORKANI, as well as school groups and government ministers. Photo: Nusi, a member of FORKANI, tends to trees in a nursery. Photo: Teenagers and school groups also took part in tree planting.
Seagrass meadows expanding near inhabited islands in Maldives
Swimming through the crystal clear waters of the Maldives, a nation renowned for its marine life, it could be easy to forget that these delicate ecosystems stand on the frontline of climate change and that seagrass habitats are in crisis globally. Now, my research, which combined hundreds of hours of fieldwork with thousands of satellite images, has uncovered something unexpected: Maldivian seagrasses have expanded three-fold over the last two decades—and island populations could be playing a part. I also discovered that seagrass is surprisingly three times more likely to be found next to inhabited islands, rather than uninhabited. So this flowering plant seems to benefit from living in seas close to humans. Seagrass habitats are expanding in some areas, to the surprise of researchers. CREDIT: Matthew Floyd, CC BY-ND Seagrasses grow along coasts all around the world. They can help guard against climate change yet they are frequently underappreciated. In the Maldives, seagrass meadows are dug up to maintain the iconic white beaches that are a frequent feature of honeymoon photos. Important marine habitats have declined in the Maldives. Amid this backdrop of environmental uncertainty, I have spent more than three years studying seagrasses here alongside a team of scientists. We found that seagrasses are faring remarkably well and one of the most plausible drivers could be the supply of nutrients from densely populated areas, such as tourist resorts. Every day, human activities could provide valuable nutrients for seagrass habitats in an otherwise nutrient limited environment. Food waste is traditionally discarded into the sea from the beach and rain can wash excess fertilizers from farmland into the ocean. As human populations and fertilizer use have both increased, we suspect that seagrass meadows have started to thrive and expand as a result of this increased nutrient supply. Additionally, building work around islands may create more suitable habitats for seagrass. Land reclamation is widespread across the country as the population has expanded by 474% since 1960. (A) Trends in overall seagrass extent in the Maldives from 2000-2021, (B) Seagrass area trends detailing changes across all 26 atolls from 2000-2021 CREDIT: Matthew Floyd, CC BY-ND During this development, sand is dug up from the seabed and some inevitably spills into the water. The structure of seagrass meadows can slow down local water currents, promoting suspended sand grains to sink and creating more sediment for future generations of seagrass to grow into. Currently, nutrient inputs seem to be creating just the right conditions for seagrasses. But if nutrients continue to increase, there is a risk that the seagrasses will be outcompeted by seaweeds and smothered. Continued land reclamation works that disregard seagrass may also remove this important habitat. So the future of this Maldivian success story may therefore largely lie in our hands. The ecotourism paradox Although seagrass removal has done little to curb habitat expansion, it highlights a troubled relationship with the tourism industry upon which so many jobs in the Maldives depend. Because it can ultimately make water depths shallower, seagrass can limit boat access and mooring, and therefore interfere with daily life. The proliferation of seagrass in areas of domestic refuse has understandably damaged its image in the eyes of the public. But, by making coastal waters shallower, seagrasses reinforce coastal protection. And by growing close to refuse sites, they absorb excess nutrients and clean the water of pathogens. Despite being a vital tool in the fight against climate change, seagrass clearly has an image problem on the islands. As a marine ecologist, I firmly believe that conservation scientists—and ecotourists—have an important role to play in conveying the value of seagrasses. Conservationists must also fully appreciate the challenges that meadow expansion can bring to local communities, and understand how the needs of conservation and tourism may differ. There is hope. A campaign called #ProtectMaldivesSeagrass, recently launched by Blue Marine Foundation and Maldives Underwater Initiative, led to 37 resorts (out of a total of 168) pledging to protect their seagrass meadows. Additionally, the data from my research can be used to protect seagrass habitats and quantify their value to people and nature. Hopefully, the unexpected—yet welcome—success of seagrass in the Maldives is a cause for conservation optimism. And perhaps tourist resorts can learn to love their newly expanding neighbors. More information: Floyd, M., East, H.K., Traganos, D. et al. Rapid seagrass meadow expansion in an Indian Ocean bright spot. Sci Rep 14, 10879 (2024). https://doi.org/10.1038/s41598-024-61088-1 This article is republished from The Conversation under a Creative Commons license. Read the original article.
Making seagrass restoration more resistant to rising temperatures
New research demonstrates that seagrass habitat restoration can be enhanced by including other grasses in addition to the declining or lost species and – ultimately – that restoration efforts must proactively select species that can withstand current and intensifying stressors driven by human activities and climate change. Rising global temperatures combined with centuries of humans working within our seascapes has reshaped coastal ecosystems. Rebuilding or restoring coastal habitat is becoming a top priority for natural resource conservation and as an insurance policy for the provision of critical services including shoreline protection, clean water, and seafood. Yet, successful habitat restoration is still rare, and most efforts are unsustainably expensive and labor intensive. “Any gardener knows the difficultly in mastering how to grow a plant from seed or a clipping, and the same goes for restoration practitioners using habitat-forming species – discovering the perfect conditions.” says Enie Hensel, lead-author, postdoctoral researcher at UF IFAS SWES Nature Coast Biological Station and former postdoctoral researcher at William & Mary’s Virginia Institute of Marine Science (VIMS). TOP LEFT IMAGES ARE COLLECTED WIDGEONGRASS (TOP) AND EELGRASS (BOTTOM) SEEDS THAT WERE SEEDED IN LYNNHAVEN RIVER, VIRGINIA BEACH, VA TO RESTORE SEAGRASS HABITAT (SECOND FROM LEFT) THAT CAN HANDLE MULTIPLE NOVEL STRESSORS INCLUDING WARMING TEMPERATURES. CREDIT: CREDIT: ENIE HENSEL, UMCES IAN SYMBOLS, VIRGINIA INSTITUTE OF MARINE SCIENCE. Seagrasses are experiencing global declines and, in the Chesapeake Bay, United States, where this study was conducted, intensifying heat waves are a main cause for declines in the dominant seagrass, eelgrass (Zostera marina). Recent research has shown the most successful restorations span large areas and location selection is key. The location should have a certain sand or sediment type, water quality level, temperature range, and the presence of beneficial ‘bugs’ or invertebrates that graze off grass-smothering algae – all of which are dependent on grass identity (M. M can Katwijk et al., 2016). “These novel environmental conditions are a challenge for restoration. But what tends to always thrive in someone’s yard, no matter how hard one caters to their prized lawn grass, are weeds. And this fact might translate well to seagrass restoration – incorporating ‘weedy,’ or generalist, seagrass species that aren’t necessarily the targeted species for a given restoration,” says Enie. “This project is important because Chesapeake Bay eelgrass has been declining for the past 30 years due to warming waters and we need to start thinking about alternative restoration strategies that accommodate this shifting environmental baseline. Here, we included a widely distributed generalist seagrass, widgeongrass [Ruppia maritima], which increases the portfolio of species diversity, providing some insurance that helps enhance long term restoration success.” says co-author Christopher J. Patrick, co-lead of the Submerged Aquatic Vegetation Restoration portion of the U.S. Army Corps of Engineer’s Lynnhaven River Basin Ecosystem Restoration Project and director of the Chesapeake Bay’s SAV Monitoring and Restoration Program For this study, Enie and her collaborators leveraged a planned seagrass restoration in the lower Chesapeake Bay and conducted a field experiment to evaluate (1) which seeding methods yielded the most widgeongrass growth, tested if seeding widgeongrass next to eelgrass can increase restoration success, and quantified how either seagrass species changes restored bed structure, invertebrate communities, and nitrogen cycling. In the following year, researchers operationalized their experimental findings during a multi-acre pilot restoration. “This is the first large-scale restoration effort in the lower Chesapeake Bay to use widgeongrass, and one of the few field experiments to identify how to best grow widgeongrass in the wild,” Enie says. In the experiment, hand-seeded widgeongrass successfully grew. The highest survival and growth were when seeding mimicked nature and for this study that meant seeding widgeongrass in the fall with no pre-seed treatment – an advantageous finding for practitioners as it requires the least effort. Additionally, by seeding both widgeongrass and eelgrass, the restoration nearly doubled in size as widgeongrass was seeded in the shallows where water temperatures were above local practitioners’ recommendation for eelgrass restorations. “Two exciting findings: these young widgeongrass beds were, one, full of epiphytic algal grazers, the ‘beneficials’ for a seagrass meadow and two, recycled less nitrogen than its surrounding sandy substrate. While this trend will likely change as widgeongrass matures, young widgeongrass recycling a negligible amount of nitrogen in a nutrient-rich area should have a positive effect on both grasses by not further increasing available nutrients, a known seagrass stressor in human-influenced systems like the Virgina Beach area” says Enie. This study was a part of the initial phase for SAV Restoration led and supported by William G. Reay of the Chesapeake Bay National Estuarine Research Reserve (NOAA NOS/OCM, NA21NOS4200127) at VIMS as well as Robert J. Orth and Christopher J. Patrick of VIMS (NSF OCE 1737258 and 1658135) for the ‘Lynnhaven River Basin Ecosystem Restoration Project’ led and funded by the U.S. Army Corps of Engineers with local Norfolk District USACE (W912HZ-20-2-0021) as well as collaboration with City of Virginia Beach Department of Defense. More information: Hensel et al, Incorporating generalist seagrasses enhances habitat restoration in a changing environment , Journal of Applied Ecology (2024). DOI: 10.1111/1365-2664.14643 This story is republished courtesy of Virginia Institute of Marine Science.