The fast changes in climate are driving global efforts to reduce greenhouse emissions and offset those that cannot be avoided. Interest in vegetated coastal ecosystems, known as Blue Carbon Ecosystems (BCEs), has grown rapidly due to their potential contribution to global carbon sequestration. Spain and Portugal host two of the main BCEs types; seagrass meadows and tidal marshes. To date, no comprehensive national assessment of BCEs carbon stocks has been conducted for Spain and Portugal. We have assessed the magnitude of the carbon sink associated with them across the entire Iberian Peninsula and insular Spanish territories and the potential CO2 emission resulting from their degradation. The BCEs in the studied area are estimated to store 95 Tg CO2-eq in the biomass and top meter of soil, equivalent to about 25% of the CO2 emissions of Spain and Portugal in 2022. The average rate of accumulation of organic carbon to the soil stock was estimated at 0.15 Tg CO2-eq y-1, equivalent to 0.04% of the annual anthropogenic CO2eq emissions of these two countries (in 2022). Additionally, the loss of BCEs in Spain and Portugal over the last century may have released 11-27 Tg CO2-eq, whereas we predicted that 1.3-5.6 Tg CO2-eq will be released over the next 30 years. Which underscores the urge to increase conservation and restoration efforts. This study provides the first comprehensive Spanish and Portuguese national blue carbon inventory for its inclusion in NDCs, providing baseline data for the implementation of blue carbon offsetting projects.

Abstract Following the unprecedented marine heatwaves of summer 2022, extensive flowering of the endemic seagrass Posidonia oceanica was witnessed across the western Mediterranean. To unravel the causes of this event, we conducted a pan-Mediterranean analysis across 442 sites spanning all Mediterranean ecoregions, with 76% exhibiting flowering. Flowering differed regionally, with both highest flowering prevalence (over 90%) and flowering intensity (up to 0.75) recorded in the Liguro-Provençal and Balearic Seas. We demonstrate that regions experiencing large summer sea surface temperature anomaly with high marine heatwave cumulative intensity displayed the highest flowering intensity. The probability of flowering was very likely when marine heatwave cumulative intensity exceeded ⁓120°C days. These findings suggest that marine heatwaves trigger flowering in P. oceanica and, given the high energetic cost of sexual reproduction, continued ocean warming may shift energy allocation toward flowering. This shift could profoundly affect the species’ reproductive strategies, posing major challenges and uncertainties for its long-term evolution.

Seagrass ecosystems are pivotal contributors to coastal carbon sequestration through the long-term burial of organic carbon (OC) in sediments. Yet global burial estimates remain uncertain, with early values of 138 ± 38 g OC m-2 yr-1 derived from a limited dataset biased toward highly depositional communities and indirect, production-based approaches. We call for a downward revision, supported by a data-driven assessment based on a global synthesis of 326 dated sediment cores integrating OC burial over the last century. We find that seagrass meadows bury OC at a geometric mean rate of 26 ± 2 g OC m-2 yr-1, with an area-weighted global average of 33 ± 10 g OC m-2 yr-1 accounting for bioregional differences in seagrass distribution. Globally, these rates scale to 6–16 Tg C yr-1, based on current mapped seagrass extent (247,800–366,200 km2), and reveal that ~15% of seagrass net community production is retained and buried locally. Although our estimate is roughly one-fourth of earlier values, seagrass sediments still account for 3–6% of total oceanic OC burial, despite occupying <0.1% of the seafloor. Combined with mangroves and tidal marshes, OC burial in vegetated coastal sediments represents an estimated 8–13% of total oceanic OC burial.

Mitigation of climate change, implies, among other measures, the increase on the use of carbon-free energy sources, ensuring a zero environmental footprint. Borehole heat exchangers (BHE), a renewable heat source from the ground used for thermal regulation of infrastructures, could significantly reduce CO2 emissions. Yet, BHE perturbs groundwater temperature by heating and cooling the ground in summer and winter, respectively, which may alter the temperature of Sea Groundwater Discharges. We propose a methodology to strategically locate BHE to discharge cooler temperatures into the sea during summer, alleviating the extreme marine temperatures occurring during marine heatwaves around the groundwater discharge areas, and ensuring a thermal refuge for temperature-sensitive coastal ecosystems. This study opens a new avenue to accomplish the climate targets of the Paris Agreement and mitigate the negative effects of global warming on coastal ecosystems.

Seagrass meadows are critical components of coastal ecosystems, playing a significant role in the global carbon cycle. These "Blue Carbon Ecosystems" (BCEs) are highly effective natural carbon sinks because they are highly productive, trap allochthonous carbon, and can store sequestered carbon for centuries to millennia in the sediment. Hence, they contribute to the long-term removal of atmospheric CO2 and prevent the remineralization of buried carbon via methanogenesis, thereby supporting climate regulation. This study evaluates the recovery of ecosystem services, specifically greenhouse gas (GHG) flux regulation, in a Zostera marina seagrass meadow that has undergone phased restoration since 2015. By assessing the fluxes of methane (CH4) and carbon dioxide (CO2) across different restoration stages using a LICOR 7810 and an incubator chamber, we explore how the meadow's GHG emissions and carbon sequestration capacity change over time as the ecosystem recovers. Our findings show that, after 9 years of restoration, CH4 emissions decreased by 1.11-fold and CO2 net sequestration increased by 1.23-fold compared to the eroded meadow. While CO2 fluxes in the older restored meadow are 1.33 times higher than those in the original meadow, CH4 fluxes are 3 times higher, indicating a greater challenge in restoring ecosystem services related to methane flux. Despite this, GHG fluxes, especially methane emissions, decrease over time, suggesting that restored meadows are gradually recovering their capacity as carbon sinks. This study highlights the potential of phased restoration to enhance carbon sequestration and support long-term climate mitigation efforts.

The brown macroalga Ascophyllum nodosum is a foundation species on intertidal rocky shores, where its perennial canopy and high productivity support key ecological functions. However, its population dynamics near the northern edge, where low temperatures and sea ice may challenge stability, are largely unknown. We followed the population structure, dynamics, and nutrient status of A. nodosum in the sheltered, subarctic Kobbefjord, Greenland from 2012 to 2019. Despite the northern location, population biomass (16-27 kg FW · m-2) was within the upper known range and was dominated by few large (max length: 109 cm), old individuals (observed age: up to 19 years; estimated mean lifespan: 37.5 years based on intrinsic mortality rate). Population density remained stable because of low mortality (0.019 · year-1) and recruitment rates (0.010 · year-1), sustained by an understory of small juveniles. Biomass increased 1.5-fold over the 8-year study, supported by high biomass productivity (3.3-8.1 kg FW · m-2 · year-1) that balanced branch loss and reflected a moderate biomass turnover time (2.6-6.3 years) of organic matter, underlying the apparent stability. Such overall population stability reflects a "biomass storer" strategy typical of environments with low disturbance and nutrient levels. The stability is remarkable given seasonal ice cover (2-7.5 months per year), large variation in average daily temperature (-3.9 to 15.4°C), and low nutrient supply. While ice breakup poses a risk of shoot abrasion, the ice cover likely provides protection against ice scouring. Enhanced growth during warmer summers and earlier ice break-up suggests faster turnover rates in the future to the extent nutrient availability can support it.

Seagrass ecosystems are recognized for their capacity to sequester and store organic carbon, but there is large variability in soil organic carbon stocks associated with plant traits and environmental conditions, making the quantification and scaling of carbon storage and fluxes needed to contribute to climate change mitigation highly challenging. Here, we provide estimates of carbon stocks associated with seagrass systems (biomass and soil) through analyses of a comprehensive global database including 2700+ seagrass soil cores. The median global soil Corg stock estimate is 24.2 (12.4 - 44.9) Mg Corg ha-1 in the top 30 cm of soil, 27% lower than estimates from previous global syntheses, refining the IPCC Tier 1 soil Corg stock currently used for carbon accounting in places without local data. We estimate that seagrass carbon stocks at risk of degradation could emit 1,154 Tg (665 - 1699) CO2 with a social cost of $213 billion (2020 US dollars), if no action is taken to conserve these habitats.

Grazing by sea urchins is a main driver of kelp forest dynamics causing shifts from kelp forests to urchin barrens in the temperate region but there is limited information on such patterns from the Arctic region. Based on information from 132 underwater video transects along Greenland's West Coast at 59.9-77.8 degrees N, we explored the distribution of kelps and sea urchins, including the occurrence of sea urchin barrens, along latitudinal- and depth-gradients. We observed more extended kelp cover and deeper-growing kelp forests toward south, although with marked variability among sites. Sea urchins were present along the entire West Coast, with no clear depth-related pattern, but their densities were generally higher toward north. Kelp cover declined toward deeper, light-limited waters and was also reduced where sea urchins were abundant, in some cases with urchin barrens within the kelp beds, suggesting a potential top-down control of kelp distribution by sea urchins. Sea urchins left, on average, 10% of the potential kelp area barren, with the largest proportion (20%) of barren ground toward north. Earlier studies have identified the length of the sea-ice free period and water temperature as main bottom-up drivers of spatial distribution of kelp in this region. We conclude that sea urchins are present all along Greenland's West Coast and occur at densities suggesting they may act as local co-drivers of kelp forest distribution and cover.

ABSTRACT Exotic herbivores can exert profound impacts on terrestrial communities, but their ecological effects on marine habitats are not sufficiently quantified. The exotic crab Percnon gibbesi, which is rapidly spreading throughout the Mediterranean Sea, grazes almost exclusively on benthic macrophytes, providing an opportunity to study the potential impacts of herbivores in the marine realm. Here, we first quantified the abundance of P. gibbesi in Mallorca (Balearic Islands; Spain) in 2023/2024 and reported average densities of 61 individuals 100 m−2, approximately 30 times greater than those recorded in 2003 on the islands. We then performed a feeding preference experiment using common native and invasive species of macroalgae (Caulerpa cylindracea, Halimeda incrassata, Haliptilon virgatum, Halopteris scoparia, Padina pavonica, and Ulva compressa) from the Mediterranean Sea. The per capita grazing rates of P. gibbesi (3.83 ± 1.71 WW g crab−1 day−1), which can ingest almost 75% of their body weight daily, were higher than those recorded for most native herbivorous species in the Mediterranean. The estimated daily grazing rates for P. gibbesi average 23.59 ± 15.17 kg WW macroalgae ha−1 day−1, value that corresponds with 0.1% to 10.9% (average 5.5%) of the total macroalgae production in this area. Our experiment revealed clear preferences of P. gibbesi for three species of macroalgae, which were not explained by the nutritional content. Overall, our results generate great concern and, coupled with the large extent of the invasion, indicate that the ecological impacts of this exotic herbivore on Mediterranean marine communities could be substantial, and have, until now, gone largely unreported.

Marine and salt marsh sediments contain large amounts of organic carbon (OC) and are therefore important in the global carbon cycle. Here, we collated previously published and unpublished measurements of sediment OC in marine and salt marsh sediments in European regional seas (EURO-CARBON; available at https://doi.org/10.5281/zenodo.14905489). To the extent possible the OC data were complemented by variables such as sediment porosity and dry bulk density. The EURO-CARBON dataset holds 61306 individual data entries of sediment OC content from different regions of European regional seas. Around three quarters (76%) were collected in coastal and deep sea bare sediments, 18% from salt marshes, 7% from seagrass habitats, and 0.03% from macroalgal habitats. For all habitats and sediment depth layers the OC content varied between <0.1 and 41.56 % (avg.: 2.47 ± 3.37 %; median: 1.39 %), with the content generally decreasing in the following sequence: salt marsh (5.01 ± 5.96 %; 3.03 %) > seagrass (2.37 ± 5.96 %; 3.03 %) > bare sediment (1.88 ± 2.03 %; 1.20 %). The EURO-CARBON dataset will serve as a basis for future work, and it will be an important resource for researchers, managers, and policymakers working towards protecting sediment OC pools.

The habitat-forming intertidal brown alga Ascophyllum nodosum has its colder northern distribution limit at 69°N in Disko Bay, Greenland. Its reproductive effort has never been assessed there despite expected northward expansion with climate change. We analyzed reproductive allocation and phenology at the northern distribution edge and across the geographical distribution range through field studies at three Greenland sites and one Danish site, supplemented with a literature survey. Because Ascophyllum is long-lived and forms annual segments through apical growth, old shoots sampled in the reproductive season revealed receptacle formation with segment age, from the tip to the base of the shoots. We confirmed the fertility of the northernmost populations, as zygotes formed from gametes. We found a consistent pattern of receptacle formation with larger receptacles closer to the canopy top and receptacle abundance following a quadratic relationship with segment age. Ascophyllum's reproductive allocation constitutes 33%-39% of its annual production in the Disko Bay and increases towards southern, warmer latitudes. Reproductive phenology also varies significantly with latitude and temperature, showing a 4.5-day delay in the reproduction peak for every degree northward and a 14-day delay with every 1°C decrease in temperature. The carbon flux released from the reproductive structures to the surrounding Arctic ecosystem at the end of the reproductive season was significant, amounting to 212-827 g C m-2 year-1 in Greenland, which should be considered in future productivity assessments. Synthesis: Our results indicate different life-history strategies at the opposing distribution edges and stress the importance of temperature as a regulator of Ascophyllum reproduction. Arctic warming will likely enhance reproductive output and stimulate an earlier onset of reproduction. Furthermore, the significant contribution from sexual reproduction to the annual carbon production (26%-41% in Greenland) highlighted its importance to the Arctic detrital community.

Coastal Blue Carbon ecosystems like seagrass meadows are foundation habitats with a capacity to sequester and store organic carbon in their sediments, and their protection and restoration may thereby support climate change mitigation while also supporting biodiversity and many other ecosystem functions. However, seagrass ecosystems are being lost due to human activities, disease and, in some regions, climate change, which may trigger the release of stored carbon into the atmosphere. Yet, we do not fully understand how global change-induced seagrass loss influences sedimentary carbon dynamics. What is even less clear is whether seagrass loss may also result in tipping points, i.e., abrupt and difficult-to-reverse shifts, in carbon flux dynamics turning seagrass ecosystems from net carbon sinks to net carbon sources. Here, we propose that conceptual mechanistic models of coupled ecological and biogeochemical dynamics can help to study the effects of major stressors on seagrass meadows and associated carbon fluxes. We then illustrate one case of such a conceptual model that focuses on anthropogenic induced mortality by physical stress as an example. Our perspective highlights how a modeling approach for understanding the response of carbon fluxes in seagrass ecosystems to global change stressors may be useful in informing coastal seagrass management towards climate change mitigation actions.

Submarine Groundwater Discharge (SGD) delivers nutrients to the coastal sea triggering phytoplankton blooms, eutrophication, and can also serve as a pathway for contaminants. Wastewater treatment plants (WWTP) including injection wells in coastal areas influence coastal aquifers and might impact the composition and magnitude of SGD fluxes. In tourist areas, wastewater treatment may be less efficient and larger in volume during high seasons, potentially impacting nutrient fluxes from SGD and exacerbating environmental impacts. This study analyzes the nutrient transfer from treated wastewater injection in karstic aquifers to the coastal sea via SGD, considering the impacts of tourism seasonality. This study is conducted in Cala Deià, a small cove in the Balearic Islands, a Mediterranean tourist destination. The findings suggest that the seasonality of tourism, leading to variations in the volume of wastewater treated in the WWTP, influences the dynamics of the coastal aquifer. This leads to increased SGD water and nutrient fluxes to the sea in summer, i.e. the peak tourist season. The measured DIN, DIP, and DSi inventories in the cove are much larger in August than in April (3, 10, and 1.5 times higher, respectively) due to higher input of nutrients in summer due to SGD impacted by the WWTP. These elevated nutrient flows can support algal blooms in the cove, compromising water quality for local swimmers and tourists. Indeed, in August, shoreline stations exhibited eutrophic Chl-a concentrations, with peaks reaching approximately 4 mg Chl-a L-1. These elevated levels suggest the presence of an algal bloom during the survey. The anthropogenic origin of SGD-driven nutrients is traced in seawater and seagrass meadows, as evidenced by high ∂15N signatures indicative of polluted areas. Thus, the high pressure exerted on coastal areas by tourism activities increased the magnitude of SGD nutrient fluxes, thereby threatening coastal ecosystems and the services they provide.

AbstractSeagrasses are vital in coastal areas, offering crucial ecosystem services and playing a relevant role in coastal protection. The decrease in the density of Mediterranean seagrasses over recent decades, due to warming and anthropogenic stressors, may imply a serious environmental threat. Here we quantify the role of coastal impact reduction induced by seagrass presence under present and future climate. We focus in the Balearic Islands, a representative and well monitored region in the Mediterranean. Our results quantify how important the presence of seagrasses is for coastal protection. The complete loss of seagrasses would lead to an extreme water level (eTWL) increase comparable to the projected sea level rise (SLR) at the end of the century under the high end scenario of greenhouse gases emissions. Under that scenario, the eTWL could increase up to ~ 1.4 m, with 54% of that increase attributed to seagrass loss. These findings underscore the importance of seagrass conservation for coastal protection.

Amphiboreal taxa are often composed of vicariant phylogroups and species complexes whose divergence and phylogeographic affinities reflect a shared history of chronic isolation and episodic trans-Arctic dispersal. Ecological filters and shifting selective pressures may also promote selective sweeps, niche shifts and ecological speciation during colonization, but these are seldom considered at biogeographical scales. Here we integrate genetic data and Ecologic Niche Models (ENMs) to investigate the historical biogeography and cohesion of the polymorphic rockweed Fucus distichus throughout its immense amphiboreal range, focusing on trans-Arctic asymmetries, glacial/interglacial dynamics, and integrity of sympatric eco-morphotypes. Populations were sampled throughout the Pacific and the Atlantic, from southern rear-edges to the high-Arctic. They were genotyped for seven microsatellites and an mtDNA spacer, and genetic diversity and structure were assessed from global to local scales. ENMs were used to compare niche divergence and magnitude of post-glacial range shifts in Pacific versus Atlantic sub-ranges. Haplotypic and genotypic data revealed distinct and seemingly isolated Pacific vs Arctic/Atlantic gene-pools, with finer-scale regional sub-structuring pervasive in the Pacific. MtDNA diversity was highly structured and overwhelmingly concentrated in the Pacific. Regionally, Alaska showed the highest intra-population diversity but the lowest levels of endemism. Some sympatric/parapatric ecotypes exhibited distinct genotypic/haplotypic compositions. Strikingly, niche models revealed higher Pacific tolerance to maximum temperatures and predicted a much more consolidated presence in the NE Atlantic. Glacial and modern ranges overlapped extensively in the Pacific, whereas the modern Atlantic range was largely glaciated or emerged during the Last Glacial Maximum. Higher genetic and ecogeographic diversity supports a primary Pacific diversification and secondary Atlantic colonization, also likely reflecting the much larger and more stable climatic refugia in the Pacific. The relic distribution and reduced ecological/morphological plasticity in the NE Atlantic are hypothesized to reflect functional trans-Arctic bottlenecks, recent colonization or competition with congeners. Within the Pacific, Alaska showed signatures of a post-glacial melting pot of eastern and southern populations. Genetic/ecotypic variation was generally not sufficiently discontinuous or consistent to justify recognizing multiple taxonomic entities, but support a separate species in the eastern Pacific, at the southern rear-edge. We predict that layered patterns of phylogeographic structure, incipient speciation and niche differences might be common among widespread low-dispersal amphiboreal taxa.

Extreme storms can trigger abrupt and often lasting changes in ecosystems by affecting foundational (habitat-forming) species. While the frequency and intensity of extreme events are projected to increase under climate change, its impacts on seagrass ecosystems remain poorly documented. In January 2020, the Spanish Mediterranean coast was hit by Storm Gloria, one of the most devastating recent climate events in terms of intensity and duration. We conducted rapid surveys of 42 Posidonia oceanica meadows across the region to evaluate the extent and type of impact (burial, unburial and uprooting). We investigated the significance of oceanographic (wave impact model), geomorphological (latitude, depth, exposure), and structural (patchiness) factors in predicting impact extent and intensity. The predominant impact of Storm Gloria was shoot unburial. More than half of the surveyed sites revealed recent unburial, with up to 40 cm of sediment removed, affecting over 50 % of the meadow. Burial, although less extensive, was still significant, with 10-80 % of meadow cover being buried under 7 cm of sediment, which is considered a survival threshold for P. oceanica. In addition, we observed evident signs of recently dead matte in some meadows and large amounts of detached drifting shoots on the sea bottom or accumulated as debris on the beaches. Crucially, exposed and patchy meadows were much more vulnerable to the overall impact than sheltered or continuous meadows. Given how slow P. oceanica is able to recover after disturbances, we state that it could take from decades to centuries for it to recoup its losses. Seagrass ecosystems play a vital role as coastal ecological infrastructure. Protecting vulnerable meadows from anthropogenic fragmentation is crucial for ensuring the resilience of these ecosystems in the face of the climate crisis.

Disentangling spatial variation in climate change impacts is a pressing challenge. Here we compared the performance of Posidonia oceanica seagrass populations to temperature, throughout a year-long translocation experiment across 2800 km in the Mediterranean Sea. Transplants in central and warm-edge locations experienced temperatures >29 ºC during summer, representing thermal anomalies >5ºC above long-term maxima for cool-edge populations, 1.5ºC for central and <1ºC for warm-edge populations. At the onset of the experiment, a highly selective herbivory event removed 75% of cool-to-warm transplant biomass but left adjacent central and warm-edge treatments intact. Despite big differences in thermal stress and acute herbivory, cool-edge populations recovered and matched warm-edge populations across all performance metrics. Central populations displayed significantly lower growth and survivorship in response to thermal stress. Our findings reveal that intraspecific variation in thermal performance does not necessarily reflect thermal geography and suggest greater resilience to warming for Posidonia oceanica than previously recognised.

Warming as well as species introductions have increased over the past centuries, however a link between cause and effect of these two phenomena is still unclear. Here we use distribution records (1813-2023) to reconstruct the invasion histories of marine non-native macrophytes, macroalgae and seagrasses, in the Mediterranean Sea. We defined expansion as the maximum linear rate of spread (km year-1) and the accumulation of occupied grid cells (50 km2) over time and analyzed the relation between expansion rates and the species' thermal conditions at its native distribution range. Our database revealed a marked increase in the introductions and spread rates of non-native macrophytes in the Mediterranean Sea since the 1960s, notably intensifying after the 1990s. During the beginning of this century species velocity of invasion has increased to 26 ± 9 km2 year-1, with an acceleration in the velocity of invasion of tropical/subtropical species, exceeding those of temperate and cosmopolitan macrophytes. The highest spread rates since then were observed in macrophytes coming from native regions with minimum SSTs two to three degrees warmer than in the Mediterranean Sea. In addition, most non-native macrophytes in the Mediterranean (>80%) do not exceed the maximum temperature of their range of origin, whereas approximately half of the species are exposed to lower minimum SST in the Mediterranean than in their native range. This indicates that tropical/subtropical macrophytes might be able to expand as they are not limited by the colder Mediterranean SST due to the plasticity of their lower thermal limit. These results suggest that future warming will increase the thermal habitat available for thermophilic species in the Mediterranean Sea and continue to favor their expansion.

Limnology and Oceanography BulletinVolume 32, Issue 2 p. 84-84 Meeting Highlights It will be Worth the Wait: ASLO Aquatic Sciences Meeting 2023 in Palma de Mallorca Nona Sheila R. Agawin, Nona Sheila R. Agawin [email protected] orcid.org/0000-0001-5951-360X Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorIris E. Hendriks, Iris E. Hendriks orcid.org/0000-0002-2238-6018 Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), Esporles, SpainSearch for more papers by this authorEva Sintes, Eva Sintes orcid.org/0000-0002-7408-5647 Centro Oceanográfico de Baleares, IEO-CSIC, Palma, SpainSearch for more papers by this authorMaria Ll. Calleja, Maria Ll. Calleja orcid.org/0000-0002-5992-2013 Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorMaria Capa, Maria Capa orcid.org/0000-0002-5063-7961 Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorManuela Gertrudis García Márquez, Manuela Gertrudis García Márquez orcid.org/0000-0001-7698-5932 Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorLluis Gómez-Pujol, Lluis Gómez-Pujol orcid.org/0000-0002-6746-7604 Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorManuel Hidalgo, Manuel Hidalgo orcid.org/0000-0002-3494-9658 Centro Oceanográfico de Baleares, IEO-CSIC, Palma, SpainSearch for more papers by this authorHilmar Hinz, Hilmar Hinz orcid.org/0000-0003-4909-0089 Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), Esporles, SpainSearch for more papers by this authorNuria Marbá, Nuria Marbá orcid.org/0000-0002-8048-6789 Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), Esporles, SpainSearch for more papers by this authorElvira Mayol Alcover, Elvira Mayol Alcover orcid.org/0000-0002-6179-8269 Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), Esporles, SpainSearch for more papers by this author Nona Sheila R. Agawin, Nona Sheila R. Agawin [email protected] orcid.org/0000-0001-5951-360X Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorIris E. Hendriks, Iris E. Hendriks orcid.org/0000-0002-2238-6018 Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), Esporles, SpainSearch for more papers by this authorEva Sintes, Eva Sintes orcid.org/0000-0002-7408-5647 Centro Oceanográfico de Baleares, IEO-CSIC, Palma, SpainSearch for more papers by this authorMaria Ll. Calleja, Maria Ll. Calleja orcid.org/0000-0002-5992-2013 Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorMaria Capa, Maria Capa orcid.org/0000-0002-5063-7961 Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorManuela Gertrudis García Márquez, Manuela Gertrudis García Márquez orcid.org/0000-0001-7698-5932 Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorLluis Gómez-Pujol, Lluis Gómez-Pujol orcid.org/0000-0002-6746-7604 Department of Biology, University of the Balearic Islands, Palma, SpainSearch for more papers by this authorManuel Hidalgo, Manuel Hidalgo orcid.org/0000-0002-3494-9658 Centro Oceanográfico de Baleares, IEO-CSIC, Palma, SpainSearch for more papers by this authorHilmar Hinz, Hilmar Hinz orcid.org/0000-0003-4909-0089 Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), Esporles, SpainSearch for more papers by this authorNuria Marbá, Nuria Marbá orcid.org/0000-0002-8048-6789 Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), Esporles, SpainSearch for more papers by this authorElvira Mayol Alcover, Elvira Mayol Alcover orcid.org/0000-0002-6179-8269 Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), Esporles, SpainSearch for more papers by this author First published: 04 April 2023 https://doi.org/10.1002/lob.10565Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume32, Issue2May 2023Pages 84-84 RelatedInformation

The tropical seagrass Halophila stipulacea invaded the Eastern Mediterranean Sea in the late nineteenth century and progressively spread throughout the basin ever since. Its spread is expected to continue north-westward as the Mediterranean Sea becomes warmer, potentially changing the seagrass biogeography of the basin. Given the power of genomics to assess invasion dynamics in non-model species, we report the first ddRAD-seq study of H. stipulacea and small-scale population genomic analysis addressing its century-old Mediterranean invasion. Based on 868 SNPs and 35 genotyped native (Red Sea) and exotic (from Cyprus, Greece, and Italy) samples, results suggest that genetic structure was high, especially between major geographic discontinuities, and that exotic populations maintain comparably lower genetic diversity than native populations, despite 130 years of invasion. The evidence of high heterozygosity excess, coupled with previously reported male-dominated and rare flowering records in the exotic range, suggests that clonal propagation likely played a pivotal role in the successful colonization and spread of H. stipulacea in the Mediterranean. This shift in reproductive strategy, particularly evident in the Italian populations located closest to the western boundary and representing more recent establishments, underscores the importance of this cost-effective mode of reproduction, especially during the initial stages of invasion, raising questions about the species future expansion trajectory. Our findings serve as a catalyst for future research into the species’ invasion dynamics, including deciphering the intricate roles of acclimatization and rapid adaptation, important for a comprehensive assessment of invasion risks and improving management strategies aimed at conserving seagrass ecosystems.