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Macroalgae (or seaweed) aquaculture can potentially provide many ecosystem services, including climate change mitigation, coastal protection, preservation of biodiversity and improvement of water quality. Nevertheless, there are still many constraints and knowledge gaps that need to be overcome, as well as potential negative impacts or scale-dependent effects that need to be considered, before macroalgae cultivation in Europe can be scaled up successfully and sustainably. To investigate these uncertainties, the Expert Working Group (EWG) on Macroalgae was established. Its role was to determine the state of knowledge regarding the potential of macroalgae culture in providing climate-related and other ecosystem services (ES) and to identify specific knowledge gaps that must be addressed before harvesting this potential. The methodological framework combined a multiple expert consultation with Delphi process and a Quick Scoping Review (QSR). To analyse the outcome of both approaches, the EWG classified the findings under the categories Political, Environmental, Social, Technical, Economic and Legal (PESTEL approach) and categorised the ES based on the CICES 5.1 classification. Although representative stakeholders from many different disciplines were contacted, the majority of responses to the Delphi process were from representatives of academia or research. While the results of each method differed in many ways, both methods identified the following top six ecosystem services provided by seaweed cultivation: i) provisioning food, ii) provisioning hydrocolloids and feed, iii) regulating water quality, iv) provisioning habitats, v) provisioning of nurseries and vi) regulating climate. Diverse technological knowledge gaps were identified by both methods at all scales of the macroalgae cultivation process, followed by economic and environmental knowledge gaps depending on the method used. Based on suggestions from the expert respondents in the Delphi process, there is a cl

Macroalgae (or seaweed) aquaculture can potentially provide many ecosystem services, including climate change mitigation, coastal protection, preservation of biodiversity and improvement of water quality. Nevertheless, there are still many constraints and knowledge gaps that need to be overcome, as well as potential negative impacts or scale-dependent effects that need to be considered, before macroalgae cultivation in Europe can be scaled up successfully and sustainably. To investigate these uncertainties, the Expert Working Group (EWG) on Macroalgae was established. Its role was to determine the state of knowledge regarding the potential of macroalgae culture in providing climate-related and other ecosystem services (ES) and to identify specific knowledge gaps that must be addressed before harvesting this potential.

Cystoseira sensu lato (s.l.) – encompassing the genera Cystoseira sensu stricto (s.s.), Ericaria and Gongolaria – is a diverse group of forest-forming brown macroalgae endemic to the warm-temperate North-east Atlantic. These algae have immense biogeographic and ecological significance and have been experiencing recent regional declines. Most Cystoseira s.l. display important morphological plasticity and can be confused with similar species. Therefore, species boundaries, geographic ranges and phylogenetic affinities remain imprecise for most. In the face of persistent taxonomic difficulties, several authors underlined the necessity for new molecular-based approaches, but studies so far lacked representativity, resolution and standardization. To fill in these gaps, in this study we sequenced a comprehensive collection of Cystoseira s.l. spanning its entire North-east Atlantic range for a ~1200 bp cox1 barcode, and sequenced selected individuals representing major genetic entities for a few additional plastid markers. Phylogeographic, phylogenetic and species delimitation methods revealed 27 Molecular Operational Taxonomic Units, including unaccounted cryptic diversity, and elucidated with unprecedented resolution species compositions and phylogenetic relationships within each genus. Some entities within the lineages Cystoseira compressa/humilis, Ericaria brachycarpa/crinita, E. selaginoides and tophulose Gongolaria, as well as among free-living algae, conflicted with a priori taxonomic assignments, and required the redefinition, reinstatement and recognition of new taxa. For some, diagnostic mutations and biogeography were more useful for species identifications than morphological characters or conventional barcoding gaps. A few species showed narrow geographic ranges and others were the sole representatives of their respective lineages. Several sister-species showed Atlantic vs Mediterranean complementary ranges. Phylogenetic signal of cox1 was nevertheless insuffic

[EN] Despite being major ecosystem services providers, seagrass meadows and macroalgae forests are suffering a global decline as a result of anthropogenic pressures acting at worldwide scales. In addition to mitigation measures and sustainable management of coastal ecosystems, ecological restoration activities are considered critical in order to boost the recovery of ecosystem functioning and services. In the case of marine macrophytes, considerable progress has been made over the last few decades; however, the knowledge, methodologies, and techniques to develop large-scale restoration actions are limited in comparison with terrestrial macrophytes. In this context, this master's thesis aims to identify and summarise the current state of knowledge regarding marine macrophyte restoration. To do this a systematic quick scoping review was conducted considering only peer-reviewed original research articles published in internationally recognised scientific journals from 1980 to date. The results indicated an increasing global trend in research interest in marine macrophyte restoration during the last decades; 224 restoration actions were identified out of 150 eligible articles. Seagrass restoration accounted for 83.9% of the trials, and seaweeds for the remaining 16.1%. Zostera marina was the most studied species, accounting for the 33.04% of all studies. Overall, seagrass restoration trials were conducted at larger scales and considered for a longer monitoring period than studies aiming to restore seaweed forests. Since the 80´s, the success of seagrass restoration actions followed an increasing trend in Europe and Asia, but no such trend was identified in the case of macroalgae restoration. In assessing the factors determining the success of restoration actions in seagrasses and seaweeds, the age of the biological material considered in the actions was shown to be a significant factor in relation to the likelihood of success in both cases. In seagrasses, transplantatio, [ES] A pesar de los importantes servicios ecosistémicos que proporcionan las praderas marinas y los bosques de macroalgas, están sufriendo un declive global como consecuencia de las presiones antropogénicas que actúan sobre estos a escala mundial. Además de las medidas de mitigación y gestión sostenible de los ecosistemas costeros, las actividades de restauración se consideran fundamentales para impulsar la recuperación del funcionamiento y los servicios de los ecosistemas. En el caso de los macrófitos marinos, se ha avanzado considerablemente en las últimas décadas; sin embargo, los conocimientos, metodologías y técnicas para desarrollar acciones de restauración a gran escala son limitados en comparación con los macrófitos terrestres. En este contexto, esta tesis de máster pretende identificar y resumir el grado actual de conocimiento sobre la restauración de macrófitos marinos. Para ello, se ha realizado una revisión rápida y sistemática, teniendo en cuenta únicamente los artículos de investigación originales revisados por pares y publicados en revistas científicas reconocidas internacionalmente desde 1980 hasta la fecha. Se observó un aumento global del interés de la investigación en la restauración de macrófitos marinos durante las últimas décadas; se identificaron 224 acciones de restauración de un total de los 150 artículos revisados. La restauración de hierbas marinas representó el 83.9% de los ensayos, y las algas el 16.1% restante. Zostera marina fue la especie más estudiada, representando el 33.04% de todos los estudios. En general, los ensayos de restauración de praderas marinas se realizaron a mayor escala y consideraron un periodo de seguimiento más largo que los experimentos con algas. Desde los años 80, el éxito de las acciones de restauración de praderas marinas siguió una tendencia creciente en Europa y Asia, pero no se identificó ninguna tendencia de éxito en la restauración de macroalgas. Al evaluar los factores que determinan el éxito de las acci

Zostera marina and Z. noltii are two dominant meadow-forming seagrass species in temperate regions in the northern hemisphere. Seagrass meadows provide several goods and ecological services and rank amongst the most valuable ecosystems worldwide. Phenological shifts in Zostera species occur along latitudinal or temperature gradients, leading to an expectation for distinct seasonal dynamics and annual production in Spain and Ireland. Despite their global ecological importance, seasonal seagrass traits of populations exposed to contrasting climate settings from Ireland and southern Spain are poorly described. To address this gap, we evaluated the seasonal vegetative development (morphology, population structure, and productivity) of Z. marina and Z. noltii populations exposed to cold (western Ireland) and warm (southern Spain) temperatures over a year-long period. Our results highlight contrasting dynamics of Z. marina populations across their temperature range. The Irish population exhibited maximal growth during warmer months while the Spanish population revealed signs of growth reduction under maximum annual temperatures. Our results suggest that plants of Z. marina in Ireland were temperature-limited at most times, but in southern Spain exceeded their optima temperature for growth during summer. In addition, Irish and Spanish Z. noltii populations displayed differential vegetative dynamics and population structures, likely related to the contrasting local temperature regimes. These differences were particularly evident in summer when shoot size and growth rates were reduced in warm-temperate locations. This study represents an essential comparative baseline for future assessments of ecological status, and anticipated growth stress induced by climate change across the distributional gradient, of these important Zostera species

The red seaweed Agarophyton vermiculophyllum is an invasive species native to the north-west Pacific, which has proliferated in temperate estuaries of Europe, North America and Africa. Combining molecular identification tools, historical satellite imagery and one-year seasonal monitoring of biomass and environmental conditions, the presence of A. vermiculophyllum was confirmed, and the invasion was assessed and reconstructed. The analysis of satellite imagery identified the first bloom in 2014 and revealed that A. vermiculophyllum is capable of thriving in areas, where native bloom-forming species cannot, increasing the size of blooms (ca. 10%). The high biomass found during the peak bloom (>2 kg m−2) and the observation of anoxic events indicated deleterious effects. The monitoring of environmental conditions and biomass variability suggests an essential role of light, temperature and phosphorous in bloom development. The introduction of this species could be considered a threat for local biodiversity and ecosystem functioning in a global change context.

The red seaweed Agarophyton vermiculophyllum is an invasive species native to the north-west Pacific, which has proliferated in temperate estuaries of Europe, North America and Africa. Combining molecular identification tools, historical satellite imagery and one-year seasonal monitoring of biomass and environmental conditions, the presence of A. vermiculophyllum was confirmed, and the invasion was assessed and reconstructed. The analysis of satellite imagery identified the first bloom in 2014 and revealed that A. vermiculophyllum is capable of thriving in areas, where native bloom-forming species cannot, increasing the size of blooms (ca. 10%). The high biomass found during the peak bloom (>2 kg m−2) and the observation of anoxic events indicated deleterious effects. The monitoring of environmental conditions and biomass variability suggests an essential role of light, temperature and phosphorous in bloom development. The introduction of this species could be considered a threat for local biodiversity and ecosystem functioning in a global change context.

The evolutionary history of the genus Ruppia has been shaped by hybridization, polyploidisation and vicariance that have resulted in a problematic taxonomy. Recent studies provided insight into species circumscription, organelle take-over by hybridization, and revealed the importance of verifying species identification to avoid distorting effects of mixing different species, when estimating population connectivity. In the present study, we use microsatellite markers to determine population diversity and connectivity patterns in Ruppia cirrhosa including two spatial scales: (1) from the Atlantic Iberian coastline in Portugal to the Siculo–Tunisian Strait in Sicily and (2) within the Iberian Peninsula comprising the Atlantic–Mediterranean transition. The higher diversity in the Mediterranean Sea suggests that populations have had longer persistence there, suggesting a possible origin and/or refugial area for the species. The high genotypic diversities highlight the importance of sexual reproduction for survival and maintenance of populations. Results revealed a regional population structure matching a continent–island model, with strong genetic isolation and low gene flow between populations. This population structure could be maintained by waterbirds, acting as occasional dispersal vectors. This information elucidates ecological strategies of brackish plant species in coastal lagoons, suggesting mechanisms used by this species to colonize new isolated habitats and dominate brackish aquatic macrophyte systems, yet maintaining strong genetic structure suggestive of very low dispersal.

The evolutionary history of the genus Ruppia has been shaped by hybridization, polyploidisation and vicariance that have resulted in a problematic taxonomy. Recent studies provided insight into species circumscription, organelle take-over by hybridization, and revealed the importance of verifying species identification to avoid distorting effects of mixing different species, when estimating population connectivity. In the present study, we use microsatellite markers to determine population diversity and connectivity patterns in Ruppia cirrhosa including two spatial scales: (1) from the Atlantic Iberian coastline in Portugal to the Siculo–Tunisian Strait in Sicily and (2) within the Iberian Peninsula comprising the Atlantic–Mediterranean transition. The higher diversity in the Mediterranean Sea suggests that populations have had longer persistence there, suggesting a possible origin and/or refugial area for the species. The high genotypic diversities highlight the importance of sexual reproduction for survival and maintenance of populations. Results revealed a regional population structure matching a continent–island model, with strong genetic isolation and low gene flow between populations. This population structure could be maintained by waterbirds, acting as occasional dispersal vectors. This information elucidates ecological strategies of brackish plant species in coastal lagoons, suggesting mechanisms used by this species to colonize new isolated habitats and dominate brackish aquatic macrophyte systems, yet maintaining strong genetic structure suggestive of very low dispersal.

Highlights: • Cystoseira ericaefolia assemblages were studied along the Mediterranean-Atlantic transition (Alboran Sea). • The assemblages showed significant differences at local and regional scales. • Regional oceanographic features seemed to play an important role explaining regional differences. • No significant differences were found between assemblages under different pollution pressures. • The results support that the effects of pollution are more visible at landscape scales than at assemblage ones. Abstract: The Cystoseira ericaefolia group is conformed by three species: C. tamariscifolia, C. mediterranea and C. amentacea. These species are among the most important habitat forming species of the upper sublittoral rocky shores of the Mediterranean Sea and adjacent Atlantic coast. This species group is sensitive to human pressures and therefore is currently suffering important losses. This study aimed to assess the influence of anthropogenic pressures, oceanographic conditions and local spatial variability in assemblages dominated by C. ericaefolia in the Alboran Sea. The results showed the absence of significant effects of anthropogenic pressures or its interactions with environmental conditions in the Cystoseira assemblages. This fact was attributed to the high spatial variability, which is most probably masking the impact of anthropogenic pressures. The results also showed that most of the variability occurred on at local levels. A relevant spatial variability was observed at regional level, suggesting a key role of oceanographic features in these assemblages.

Highlights: • Cystoseira ericaefolia assemblages were studied along the Mediterranean-Atlantic transition (Alboran Sea). • The assemblages showed significant differences at local and regional scales. • Regional oceanographic features seemed to play an important role explaining regional differences. • No significant differences were found between assemblages under different pollution pressures. • The results support that the effects of pollution are more visible at landscape scales than at assemblage ones. Abstract: The Cystoseira ericaefolia group is conformed by three species: C. tamariscifolia, C. mediterranea and C. amentacea. These species are among the most important habitat forming species of the upper sublittoral rocky shores of the Mediterranean Sea and adjacent Atlantic coast. This species group is sensitive to human pressures and therefore is currently suffering important losses. This study aimed to assess the influence of anthropogenic pressures, oceanographic conditions and local spatial variability in assemblages dominated by C. ericaefolia in the Alboran Sea. The results showed the absence of significant effects of anthropogenic pressures or its interactions with environmental conditions in the Cystoseira assemblages. This fact was attributed to the high spatial variability, which is most probably masking the impact of anthropogenic pressures. The results also showed that most of the variability occurred on at local levels. A relevant spatial variability was observed at regional level, suggesting a key role of oceanographic features in these assemblages.

The Alboran Sea is the westernmost ecoregion of the Mediterranean Sea. It is located in the vicinity of Strait of Gibraltar, the only natural connection of the Mediterranean Sea with global circulation. This ecoregion presents steep and highly variable environmental gradients, thus acting as a natural filter for Mediterranean and Atlantic species. This study aimed to analyse spatial patterns of littoral and upper sublittoral communities and their relationship with oceanographic conditions and coastal geomorphology, and to quantify littoral and upper sublittoral rocky shore communities at landscape scale. The results suggest that oceanographic conditions are the main factor to explain landscape patterns along the studied area, while geomorphological features should be related with local-scale variability. In this sense, three biogeographic subregions, matching with oceanographic patterns, were identified: western, central and eastern. These subregions showed significant differences in the structure and the composition of the littoral and upper sublittoral community, which can be explained by regional oceanographic dynamics. Posidonia oceanica, Cystoseira ericaefolia group and Mytilus spp. were the species that most contributed to landscape dissimilarity between the three subregions identified. The central oceanographic region, where the environmental conditions were more variable, showed the poorer and less differentiated flora, suggesting the existence of a divergent boundary between the Atlantic and the Mediterranean Sea.

The Alboran Sea is the westernmost ecoregion of the Mediterranean Sea. It is located in the vicinity of Strait of Gibraltar, the only natural connection of the Mediterranean Sea with global circulation. This ecoregion presents steep and highly variable environmental gradients, thus acting as a natural filter for Mediterranean and Atlantic species. This study aimed to analyse spatial patterns of littoral and upper sublittoral communities and their relationship with oceanographic conditions and coastal geomorphology, and to quantify littoral and upper sublittoral rocky shore communities at landscape scale. The results suggest that oceanographic conditions are the main factor to explain landscape patterns along the studied area, while geomorphological features should be related with local-scale variability. In this sense, three biogeographic subregions, matching with oceanographic patterns, were identified: western, central and eastern. These subregions showed significant differences in the structure and the composition of the littoral and upper sublittoral community, which can be explained by regional oceanographic dynamics. Posidonia oceanica, Cystoseira ericaefolia group and Mytilus spp. were the species that most contributed to landscape dissimilarity between the three subregions identified. The central oceanographic region, where the environmental conditions were more variable, showed the poorer and less differentiated flora, suggesting the existence of a divergent boundary between the Atlantic and the Mediterranean Sea.