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- Predicted regime shift in the seagrass ecosystem of the Gulf of Arguin driven by climate changePublication . Chefaoui, Rosa M.; Duarte, Carlos M.; Tavares, Ana I; Frade, Duarte; Sidi Cheikh, M.A.; Abdoull Ba, M.; Serrao, EsterThe Banc d′Arguin is a marine ecosystem of global conservation significance, the largest bird sanctuary of western Africa, supported by one of the most extensive seagrass beds in the world composed by three seagrass species, two temperate near their southern limit (Zostera noltei and Cymodocea nodosa) and one tropical at its northern limit (Halodule wrightii). Here we predict the fate of this seagrass ecosystem under climate change scenarios during the 21st century, using species distribution models and sea level rise estimates. We forecast a probable decline in total seagrass area of 3340 Km2 (78%) by 2100, involving the loss of both temperate seagrasses (Z. noltei, C. nodosa), the foundational ecosystem components. By 2050, only the tropical species (H. wrightii) would remain, which forms thin and sparse shallow stands functionally distinct from the previous tall dense meadows that span wider vertical ranges. Intertidal flats, the essential bird foraging habitats, would become unvegetated and also suffer a major reduction in area (114 km2 by 2050, 587 km2 by 2100). The large projected loss of foundational seagrass species portends a collapse of major ecosystem functions with profound impacts on biodiversity, fishery resources and ecosystem services.
- A fine-tuned global distribution dataset of marine forestsPublication . Assis, J.; Fragkopoulou, Eliza; Frade, Duarte; Neiva, J.; Oliveira, André; Abecasis, David; Faugeron, Sylvain; Serrao, EsterSpecies distribution records are a prerequisite to follow climate-induced range shifts across space and time. However, synthesizing information from various sources such as peer-reviewed literature, herbaria, digital repositories and citizen science initiatives is not only costly and time consuming, but also challenging, as data may contain thematic and taxonomic errors and generally lack standardized formats. We address this gap for important marine ecosystem-structuring species of large brown algae and seagrasses. We gathered distribution records from various sources and provide a fine-tuned dataset with ~2.8 million dereplicated records, taxonomically standardized for 682 species, and considering important physiological and biogeographical traits. Specifically, a flagging system was implemented to signal potentially incorrect records reported on land, in regions with limiting light conditions for photosynthesis, and outside the known distribution of species, as inferred from the most recent published literature. We document the procedure and provide a dataset in tabular format based on Darwin Core Standard (DwC), alongside with a set of functions in R language for data management and visualization.
- Not regionally extinct: rediscovery of ruppia drepanensis in Portugal, the westernmost range edge in EuropePublication . Frade, Duarte Gonçalves; Miranda Neiva, João; Martínez-Garrido, Jose; Davison, Anne; Caminiti, Luca; Ramos, Gonçalo Miguel da Cruz e Cunha Guinote; Pearson, Gareth Anthony; Serrao, Ester A.Ruppia drepanensis Tineo ex Guss. is an important habitat-forming aquatic plant in saline and brackish Mediterranean wetlands. The species is declining in several parts of its range due to hydrological changes and habitat degradation. R. drepanensis was considered Critically Endangered, possibly Regionally Extinct in Portugal, due to not being observed since 1986 despite extensive surveys of suitable habitat. We report on a new population, the westernmost known record for the species in Europe, identified with morphological and molecular data. Despite being inside a protected area, this population occupies a single small pond adjacent to a road, making it vulnerable to habitat changes. Ex situ conservation is recommended, including seed banking and/or the establishment of new populations.
- Cryptic diversity in colonizing seagrasses and implications for conservationPublication . Frade, Duarte Gonçalves; Serrão, Ester A.; Pearson, Gareth A.Seagrasses are foundational marine angiosperms that provide essential ecosystem services, yet many aspects of their diversity and evolution remain poorly understood. This is especially true for colonising seagrasses—small, fast-growing species that dominate dynamic or marginal environments and are becoming increasingly dominant in many regions. This thesis investigates the diversity of colonising seagrasses and its implications for conservation using a combination of phylogenetic, and ecological approaches. By compiling the first comprehensive review of hybridisation and polyploidy in seagrasses, I show that these processes are more widespread than previously recognised, particularly in Ruppia, the most widely distributed genus of colonising seagrass. Phylogenetic evidence indicates that multiple hybrid or allopolyploid Ruppia lineages have colonised oceanic islands (Azores, Madeira, Canary Islands), providing clear evidence of long-distance dispersal—previously considered unlikely for the genus. Additional phylogenetic analyses and botanical surveys reveal overlooked species even in mainland Portugal, a region with a long history of seagrass research, underscoring persistent biases toward larger, persistent species. To assess how colonising and larger seagrasses may respond differently to climate change, species distribution modelling was applied to three West African seagrasses: one colonising species (Halodule wrightii) and two larger species (Cymodocea nodosa, Zostera noltei). The models predict severe losses for the larger species by 2050, while Halodule is expected to persist and expand under most scenarios. Finally, through IUCN Red List assessments, this work reviews the conservation implications of ongoing regime shifts toward colonising species and addresses unresolved taxonomic challenges. Overall, this thesis provides essential baseline data on evolutionary processes, species, and regions that remain underrepresented in the global seagrass literature.
- Updated extinction risk of seagrass species in the tropical atlantic bioregionPublication . Samper-Villarreal, Jimena; Creed, Joel C.; Frade, Duarte; Furman, Bradley T.; Bandeira, Salomão; El-Hacen, Hacen M.; Peralta, A. Carolina; Serrao, Ester A.; Vegas, Beatriz E. Vera; Tussenbroek, Brigitta I. van; Frade, Duarte GonçalvesSeagrasses can form vast meadows in coastal areas and provide valuable ecosystem services. Despite their importance, seagrasses are threatened, and their spatial extent and ecological condition have declined worldwide. Globally, there are six seagrass bioregions based on ocean basin and species distribution. The Tropical Atlantic Bioregion encompasses seagrasses in the warm waters off the Atlantic American continent, the eastern Pacific and the west coast of Africa. Here, the extinction risk of the species was determined through the Categories and Criteria of the IUCN Red List of Threatened Species. The extinction risk for the 15 native seagrass species in the bioregion was assessed and summarized as an update to the previous IUCN effort, conducted 15 years ago. The updated regional assessments were based on expert opinion and compilation of revised data on species´ distribution, population status and trend. Of the 15 native species, nine were endemic to the bioregion; thus, the regional assessment was also a global one. Two other species were typical for the region but also occurred beyond bioregional boundaries (Halodule beaudettei and H. wrightii). The remaining species were either distributed circumglobally (2 species), or consisted of peripheral populations of species characteristic of neighboring bioregions (2 species). The detailed information of 15 assessments have been made freely accessible in an open repository. Nine species maintained their previous risk of extinction status, while one species (Thalassia testudinum) changed from the Least Concern to the Near Threatened category. Downgrading of the status of T. testudinum is worrying, as this is the dominant climax species in the wider Caribbean. Its replacement by less resistant and smaller but faster growing species, such as Syringodium filiforme and H. wrightii (both classified as Least Concern), could compromise the ecosystem services of seagrasses in this bioregion. An additional two species had been recently introduced, and are also briefly covered. The assessments included past and present taxonomical uncertainties of various assessed species. Issues concerning the current boundaries of the bioregions themselves were also encountered. To address this and better capture future and ongoing range expansion or reduction associated with climate change, we propose overlapping transitional boundaries with neighboring seagrass bioregions.
- Rediscovery of Althenia (Potamogetonaceae) in Portugal, 168 years after the last collectionPublication . Frade, Duarte Gonçalves; NEIVA MACHADO, JOÃO PEDRO; Anne Davison; Pearson, Gareth Anthony; Serrao, Ester A.Althenia (Potamogetonaceae) is a small genus of aquatic angiosperms from saline environments that includes the most recently evolved seagrass, Althenia marina. One or two species occur in Europe, both rare and considered Data Deficient at the regional level. We report the first records of Althenia in Portugal since 1853: two populations in the Algarve and a third in central Portugal. As in previous studies, all Portuguese populations include plants with and without visible nerves in the leaf sheaths, a character used to distinguish between A. orientalis and A. filiformis. We tentatively recognize a single Althenia species in Eurasia, pending further studies. We recommend further searches of suitable habitat, as Althenia species are small and easily overlooked, as well as monitoring and safeguarding of known populations through in situ and ex situ conservation.
- Training manual for seagrass monitoring and management in the RAMPAO countriesPublication . Barrena de los Santos, Carmen; de la Hoz Schilling, Carolina; Queiroga, Henrique; Ahmed, Mohamed; Araújo, António; Frade, Duarte Gonçalves; Martins, Samir; Barri, Iça; Bandeira, Salomão; Failler, Pierre; Serrao, Ester A.; Santos, Carmen B. de los; Queiroga, Henrique; Cheikh, Sidi; Araújo, António; Serrão, EsterThis training manual aims to improve knowledge, raise awareness, and provide appropriate working tools to managers and other users of MPAs in the RAMPAO network for the protection and conservation of seagrass habitats. Its preparation used a participatory approach, through consultation with MPA managers and other conservation stakeholders from seven RAMPAO member countries (Cabo Verde, The Gambia, Guinea, Guinea Bissau, Mauritania, Senegal and Sierra Leone), with the aim of identifying their capacity building needs and gaining a better understanding of the threats facing seagrass beds in West Africa.
- Network analysis reveals humans as top predators and the key role of cuttlefish in the food web structure of a marine protected area (Arrábida Natural Park)Publication . Vinagre, Catarina; Almeida, Luis Pedro; Ronquillo, Pilar; Alegria Mendonça, Vanessa Sofia; Frade, Duarte Gonçalves; Gonçalves, Emanuel J.; Erzini, Karim; Serrao, Ester A.The marine protected area (MPA) of the Arrábida Natural Park is a mid-latitude hotspot for biodiversity. To understand its trophic structure, a highly defined food web network was assembled for this ecosystem, consisting of 884 taxa. Network analysis showed that humans are the top predators, as well as various seabirds, dolphins and sharks. This web is dominated by intermediate species, and its general organization follows previously reported patterns for other marine and coastal ecosystems. Two swimming crabs, Polybius navigator and Polybius henslowii, assume important roles as mid-trophic level consumers and prey, due to their high connectivity in the network. The cuttlefish, Sepia officinalis, a cephalopod of high commercial value, assumes the most pivotal role in the network, as it is the species with the highest number of prey and is among the top 10 most highly connected species (with more links to other species). Additionally, the cuttlefish is among the species with shortest path length, that is the lowest number of links connecting it to any other species. Since, this cephalopod is highly mobile and extends its territory outside the MPA, into the Sado estuary, where it is the main target of local fisheries, and is exposed to various pollution sources, close monitoring the local population of cuttlefish is of the utmost importance, not only in the Arrabida ´ MPA but also in the adjacent Sado estuary.