Posidonia seagrass meadows, veritable underwater forests, play a major ecological role. Under constant pressure from human activity, scientists are looking for ways to ensure their survival, in particular by carrying out restoration campaigns. A study conducted by the University of Liège at the marine and oceanographical research station STARESO (Calvi,
In a new blog series, our Conservation Trainee Abi David explores some of the amazing creatures that call seagrass meadows their home. The Brent Goose Branta bernicla is of a similar size to a Mallard duck, making it one of the smallest goose species in the world. They are a
Beneath the surface of the Chesapeake Bay, a subtle but dramatic shift is taking place as eelgrass gives way to its warmer-water relative, widgeon grass. A new study from researchers at William & Mary’s Batten School & VIMS shows that this seagrass swap could have ecological impacts across the Bay’s
Posidonia seagrass meadows, veritable underwater forests, play a major ecological role. Under constant pressure from human activity, scientists are looking for ways to ensure their survival, in particular by carrying out restoration campaigns. A study conducted by the University of Liège at the marine and oceanographical research station STARESO (Calvi, Corsica) reveals that the transplantation method directly influences the root microbiome, which is essential for the survival of the plants. These results pave the way for more effective and sustainable restoration techniques. The paper is published in the journal Environmental Microbiome. Roots growing on a Posidonia cutting transplanted using metal staples. Arnaud Boulenger conditioning Posidonia roots for genetic analysis of the microbiome. Credit: University of Liège, Arnaud Boulenger Often compared to terrestrial forests, Posidonia oceanica seagrass meadows form off the coast of the Mediterranean. These ecosystems act as environmental sentinels, stabilizing the seabed, storing carbon, and harboring exceptional biodiversity. Unfortunately, scientists have been observing a decline in their population for many years due to coastal urbanization, boat anchoring, and climate change. To halt this decline, researchers are experimenting with transplanting cuttings. “Until now, efforts have focused mainly on their visible survival, i.e., root recovery and leaf growth,” explains Arnaud Boulenger, a Ph.D. candidate in oceanography at ULiège (Belgium). “However, the study we conducted at STARESO reveals that the health of seagrass beds also depends on an invisible network of microorganisms associated with the roots.” It is therefore not enough to simply replant the seagrass meadows; we must also ensure the good health of their microbiome. By testing three transplantation techniques—metal staples, coconut fiber mats and potato starch structures—the team showed that the choice of substrate profoundly changed the composition of the microbiome. “Staples, which allow direct contact with the sediment, promote the establishment of key bacteria such as Chromatiales and Desulfobacterales, which are essential for the sulfur and nitrogen cycles,” the researcher explains. “Conversely, the other methods delay this beneficial colonization.” Scientists highlight that restoration methods must now incorporate this microbiological dimension, as these bacteria play a direct role in plant resilience. “These results are groundbreaking,” says Sylvie Gobert, oceanographer. “This is the first time that a study has demonstrated in situ the importance of the microbiome in the success of Posidonia transplantation. The results we have obtained open up concrete perspectives, such as the inoculation of beneficial bacteria or the design of supports that facilitate root-sediment interaction.” Restoring a seagrass bed is therefore much more than just replanting cuttings underwater. It means recreating an entire ecosystem, both visible and invisible, in which bacteria play a crucial role. As Boulenger sums it up, “it’s a bit like replanting a forest, while also ensuring that the soil that nourishes it is brought back to life.” More information: This article is republished from PHYS.ORG and provided by the University of Liège. Arnaud Boulenger et al, Microbiome matters: how transplantation methods and donor origins shape the successful restoration of the seagrass Posidonia oceanica, Environmental Microbiome (2025). DOI: 10.1186/s40793-025-00764-9
In a new blog series, our Conservation Trainee Abi David explores some of the amazing creatures that call seagrass meadows their home. The Brent Goose Branta bernicla is of a similar size to a Mallard duck, making it one of the smallest goose species in the world. They are a highly social species and form strong bonds within the groups they live in. If you spot a group of Brent Geese, look out for the ‘compass’ goose – this is the leader of the group and will lead the way between foraging areas. Depending on the species of Brent Goose, individuals may have a dark or light belly, along with a dark head and body, with adults having a small white patch on their necks. They can be seen throughout the UK during the autumn/ winter months in marine, intertidal or wetland areas. Dark bellied Brent Geese. Photo Credit Emma Butterworth Migration Just like many other bird species, Brent Geese carry out an annual migration. They spend summer months breeding and raising chicks in the Arctic and migrate to Western Europe for more temperate winters. Generally, the individuals we get overwintering here in the UK are from Siberia. Due to these long migration routes and small body size, Brent Geese have a high food demand meaning they heavily rely on stopovers to refuel. Their most popular stopover sites tend to be Zostera marina meadows. Large numbers of Brent Geese have been spotted for several weeks each year in Izembek Lagoon (Alaska), lagoons in Baja California, the German/Danish Wadden Sea, the Golfe du Morbihan (France), British estuaries, and the White Sea (Western Russian Arctic). Diet Brent Geese are heavily herbivorous and mainly consume seagrass. They have relatively short necks and lack the ability to dive so can only reach plants at low tide or in shallow water. Interestingly, during breeding season the geese will consume a wide range of plant species but show a strong preference for Zostera species throughout non-breeding seasons due to the high digestibility and nutritional value compared to other options. They have been observed eating both the leaves and rhizomes of the plants. Importance of seagrass for Brent Goose populations As mentioned previously, Brent Geese rely heavily on seagrass during their migrations. This can be seen in population trends. In the 1930s, Zostera species across the North American coast were heavily affected by wasting disease and there was a significant population decline. At the same time, a steep decline in Brent Goose population was also observed on both sides of the Atlantic, with estimates ranging from 75 – 90% of populations lost. During the 1950s, there was a good recovery of seagrass beds in the areas previously affected, which was followed by a recovery of Brent Goose populations from around 15,000 to over 100,000. Similar smaller scale events like this have been observed, showing just how important healthy seagrass meadows are for species like the Brent Goose that rely so heavily on them. Are Brent Geese bad for seagrass restoration? It could be argued that Brent Geese are bad for seagrass and bad for seagrass restoration due to their consumption of the plants. However, there is a bit more to it than that. Seagrass provides services for many species, and a food source is one of those. Anecdotally, there have been instances where restoration has occurred only for geese to come along and eat all of the freshly planted shoots, which really isn’t ideal. In the scientific literature, there is mixed evidence about how much the geese will consume and how this affects the meadow’s health, which makes it difficult to quantify their impact. Some research notes that the percent the geese eat out of the whole meadow is actually quite small and a healthy meadow should have no issue recovering from any damage. The geese could even be useful in seagrass restoration. They tend to only be seen where food is available and as such are an indicator species for the health of an ecosystem. Like all birds, they are useful for their ability to spread nutrients and seeds through their faeces, helping to spread plant species more widely than they would on their own. Additionally, they are an important food source for predators such as foxes and raptors in their Arctic breeding grounds. Brent Geese, like any other species using seagrass, are carrying out behaviours that have evolved over thousands of years. Therefore, the question of whether geese are bad for seagrass restoration is not a straightforward one. What do you think? Sources: Ganter, B. (2000). Seagrass ( Zostera spp.) as food for brent geese ( Branta bernicla ): an overview. Helgoland Marine Research, 54(2–3), 63–70. https://doi.org/10.1007/s101520050003 Find out more the role that seagrass plays for migratory birds here.
Beneath the surface of the Chesapeake Bay, a subtle but dramatic shift is taking place as eelgrass gives way to its warmer-water relative, widgeon grass. A new study from researchers at William & Mary’s Batten School & VIMS shows that this seagrass swap could have ecological impacts across the Bay’s food webs, fisheries and ecosystem functions. Published in Marine Ecology Progress Series, the study reveals that while both seagrass species offer valuable habitat, they support marine life in very different ways. The researchers estimate that the continued shift from eelgrass to widgeon grass could lead to a 63% reduction in the total quantity of invertebrate biomass living in seagrass meadows in the bay by 2060. “Several factors including water quality, rising temperatures and human development are threatening eelgrass in the Chesapeake Bay. In its place, particularly in the middle Bay, widgeon grass has expanded due to its ability to tolerate warmer, more variable conditions,” said Associate Professor Chris Patrick, who is also director of the Submerged Aquatic Vegetation (SAV) Monitoring & Restoration Program at the Batten School of Coastal & Marine Sciences & VIMS. “However, the two grasses provide structurally distinct habitats that shape the animals living within.” All grasses are not created equal While working with Patrick and earning her master’s degree at the Batten School & VIMS, lead author Lauren Alvaro engaged in extensive fieldwork studying seagrass meadows in Mobjack Bay. Her team surveyed and compared habitats consisting of eelgrass, widgeon grass as well as mixed beds. They documented everything from burrowing clams and snails to crabs and fishes to get an idea of life living within the sediment and among the grasses. The findings showed that while widgeon grass supports more individual invertebrates per gram of plant material, eelgrass meadows are home to larger animals and have more plant biomass per square meter. As a result, eelgrass supports a greater total animal biomass per square meter. “Our findings suggest that we’re likely to see a fundamental shift in the structure of the food web that favors smaller creatures as eelgrass is replaced by widgeon grass,” said Alvaro. “The eelgrass meadows produced fewer animals, but they’re bigger and more valuable to predators like fish and blue crabs.” Much of the difference is due to the physical characteristics of the two types of seagrasses. Widgeon grass beds have a greater surface-to-biomass ratio due to their narrower leaf structure, which provides more area for small invertebrates to cling to. However, eelgrass’s broader leaves provide a type of canopy favored by animals like pipefish, blue crabs, and larger isopods, which are small shrimp-like crustaceans. The bigger picture The researchers extrapolated their findings and estimated that current seagrass habitats in the Chesapeake Bay support approximately 66,139 tons of invertebrate biomass living in the sediment and among the grass beds and produce 35,274 tons of new animal biomass each growing season. Termed “secondary production,” this is the biomass the habitat makes available to higher levels of the food chain. If seagrasses continue to shift as expected, by 2060 secondary production could be reduced by more than 60% under a scenario where no further nutrient reductions occur. Nutrient runoff into the Bay is the largest threat to submerged aquatic vegetation. Even in a best-case nutrient management scenario, the Bay could still lose approximately 15% of secondary production biomass. “Within the limits of our study, it wasn’t possible to determine whether it was the meadow’s physical structure, the meadow area, or available food sources that contributed to greater numbers of fish in the eelgrass meadows,” said Alvaro. “This makes it difficult to accurately estimate fishery-level impacts of changes in meadow composition, but several lines of reasoning support an expectation of reduction in numerous commercial and recreational species.” The study adds to a growing body of research documenting the effects of changes in foundational species influenced by a warming planet. The authors cite similar research involving Florida’s mangroves and a worldwide shift from coral to algae-dominated ecosystems. As states within the Bay’s extensive watershed work to maintain and improve the health of the estuary, the team hopes their findings will help inform management decisions and restoration strategies. Protecting and restoring the remaining eelgrass and better understanding the role of widgeon grass may help preserve ecological resources for future generations and provide a buffer against future shocks. More information: This article is republished from PHYS.ORG and provided by Virginia Institute of Marine Science. Lauren Elizabeth Alvaro et al, Changing foundation species in Chesapeake Bay: implications for faunal communities of two dominant seagrass species, Marine Ecology Progress Series (2025). DOI: 10.3354/meps14901
