Percorrer por autor "Silva, João"
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- A 15-month survey of Dimethylsulfoniopropionate and Dimethylsulfoxide content in Posidonia oceanicaPublication . Richir, Jonathan; Champenois, Willy; Engels, Guyliann; Abadie, Arnaud; Gobert, Sylvie; Lepoint, Gilles; Silva, João; Santos, Rui; Sirjacobs, Damien; V. Borges, AlbertoPosidonia oceanica is the only reported seagrass to produce significant amount of dimethylsulfoniopropionate (DMSP). It is also the largest known producer of DMSP among coastal and inter-tidal higher plants. Here, we studied (i) the weekly to seasonal variability and the depth variability of DMSP and its related compound dimethylsulfoxide (DMSO) in P. oceanica leaves of a non-disturbed meadow in Corsica, France, (ii) the weekly to seasonal variability and the depth variability of DMSP to DMSO concentration to assess the potential of the DMSP:DMSO ratio as indicator of stress, and (iii) the relationships between DMSP, DMSO, and the DMSP:DMSO ratio with potential explanatory variables such as light, temperature, photosynthetic activity (effective quantum yield of photosystem II), and leaf size. The overall average concentrations of organosulfured compounds in P. oceanica leaves were 130 ± 39 µmol.g−1 fw for DMSP and 4.9 ± 2.1 µmol.g−1 fw for DMSO. Concentrations of DMSP and DMSO in P. oceanica were overall distinctly higher and exhibited a wider range of variations than other marine primary producers such as Spartina alterniflora, phytoplankton communities, epilithic Cyanobacteria and macroalgae. Concentrations of both DMSP and DMSO in P. oceanica leaves decreased from a maximum in autumn to a minimum in summer; they changed little with depth. Potential explanatory variables except the leaf size, i.e., the leaf age were little or not related to measured concentrations. To explain the seasonal pattern of decreasing concentrations with leaf aging, we hypothesized two putative protection functions of DMSP in young leaves: antioxidant against reactive oxygen species and predator-deterrent. The similar variation of the two molecule concentrations over time and with depth suggested that DMSO content in P. oceanica leaves results from oxidation of DMSP. The DMSP:DMSO ratio remained constant around a mean value of 29.2 ± 9.0 µmol:µmol for the non-disturbed harvested meadow regardless of the time of the year, the depth or the leaf size. As suggested for the salt march plant S. alterniflora, we hypothesized the DMSP:DMSO ratio could be considered as indicator of stress in seagrasses exposed to environmental or anthropogenic stressors. More research would now be needed to confirm the functions of DMSP and DMSO in seagrasses and how the DMSP:DMSO ratio will vary under various disturbances.
- 2b-RAD genotyping of the seagrass Cymodocea nodosa along a latitudinal cline identifies candidate genes for environmental adaptationPublication . Ruocco, Miriam; Jahnke, Marlene; Silva, João; Procaccini, Gabriele; Dattolo, EmanuelaPlant populations distributed along broad latitudinal gradients often show patterns of clinal variation in genotype and phenotype. Differences in photoperiod and temperature cues across latitudes influence major phenological events, such as timing of flowering or seed dormancy. Here, we used an array of 4,941 SNPs derived from 2b-RAD genotyping to characterize population differentiation and levels of genetic and genotypic diversity of three populations of the seagrass Cymodocea nodosa along a latitudinal gradient extending across the Atlantic-Mediterranean boundary (i.e., Gran Canaria-Canary Islands, Faro-Portugal, and Ebro Delta-Spain). Our main goal was to search for potential outlier loci that could underlie adaptive differentiation of populations across the latitudinal distribution of the species. We hypothesized that such polymorphisms could be related to variation in photoperiod-temperature regime occurring across latitudes. The three populations were clearly differentiated and exhibited diverse levels of clonality and genetic diversity. Cymodocea nodosa from the Mediterranean displayed the highest genotypic richness, while the Portuguese population had the highest clonality values. Gran Canaria exhibited the lowest genetic diversity (as observed heterozygosity). Nine SNPs were reliably identified as outliers across the three sites by two different methods (i.e., BayeScan and pcadapt), and three SNPs could be associated to specific protein-coding genes by screening available C. nodosa transcriptomes. Two SNPs-carrying contigs encoded for transcription factors, while the other one encoded for an enzyme specifically involved in the regulation of flowering time, namely Lysine-specific histone demethylase 1 homolog 2. When analyzing biological processes enriched within the whole dataset of outlier SNPs identified by at least one method, "regulation of transcription" and "signalling" were among the most represented. Our results highlight the fundamental importance signal integration and gene-regulatory networks, as well as epigenetic regulation via DNA (de)methylation, could have for enabling adaptation of seagrass populations along environmental gradients.
- A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicumPublication . Sordo, L.; Santos, Rui; Reis, João; Shulika, Alona; Silva, JoãoMost ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO2. However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO(2). Here we describe a system in which the target pCO(2) is controlled via direct analysis of pCO(2) in seawater. This direct type of control accommodates potential temperature and salinity shifts, as the target variable is directly measured instead of being estimated. Water in a header tank is permanently re-circulated through an air-water equilibrator. The equilibrated air is then routed to an infrared gas analyzer (IRGA) that measures pCO(2) and conveys this value to a Proportional-Integral-Derivative (PID) controller. The controller commands a solenoid valve that opens and closes the CO2 flush that is bubbled into the header tank. This low-cost control system allows the maintenance of stabilized levels of pCO(2) for extended periods of time ensuring accurate experimental conditions. This system was used to study the long term effect of OA on the coralline red algae Phymatolithon lusitanicum. We found that after 11 months of high CO2 exposure, photosynthesis increased with CO2 as opposed to respiration, which was positively affected by temperature. Results showed that this system is adequate to run long-term OA experiments and can be easily adapted to test other relevant variables simultaneously with CO2, such as temperature, irradiance and nutrients.
- Accuracy of faecal calprotectin and neutrophil Gelatinase B-associated Lipocalin in evaluating subclinical inflammation in UlceRaTIVE colitis-the ACERTIVE studyPublication . Magro, Fernando; Lopes, Susana; Coelho, Rosa; Cotter, Jose; Castro, Francisca Dias de; Sousa, Helena Tavares; Salgado, Marta; Andrade, Patrícia; Vieira, Ana Isabel; Figueiredo, Pedro; Caldeira, Paulo; Sousa, A.; Duarte, Maria A.; Avila, Filipa; Silva, João; Moleiro, Joana; Mendes, Sofia; Giestas, Silvia; Ministro, Paula; Sousa, Paula; Gonçalves, Raquel; Gonçalves, Bruno; Oliveira, Ana; Chagas, Cristina; Torres, Joana; Dias, Claudia Camila; Lopes, Joanne; Borralho, Paula; Afonso, Joana; Geboes, Karel; Carneiro, FátimaBackground and Aims: Mucosal healing and histological remission are different targets for patients with ulcerative colitis, but both rely on an invasive endoscopic procedure. This study aimed to assess faecal calprotectin and neutrophil gelatinase B-associated lipocalin as biomarkers for disease activity in asymptomatic ulcerative colitis patients. Methods: This was a multicentric cross-sectional study including 371 patients, who were classified according to their endoscopic and histological scores. These results were evaluated alongside the faecal levels of both biomarkers. Results: Macroscopic lesions [i.e. endoscopic Mayo score >= 1] were present in 28% of the patients, and 9% had active disease according to fht Ulcerative Colitis Endoscopic Index of Severity. Moreover, 21% presented with histological inflammation according to the Geboes index, whereas 15% and 5% presented with focal and diffuse basal plasmacytosis, respectively. The faecal levels of calprotectin and neutrophil gelatinase B-associated lipocalin were statistically higher for patients with endoscopic lesions and histological activity. A receiver operating characteristic-based analysis revealed that both biomarkers were able to indicate mucosal healing and histological remission with an acceptable probability, and cut-off levels of 150-250 mu g/g for faecal calprotectin and 12 mu g/g for neutrophil gelatinase B-associated lipocalin were proposed. Conclusions: Faecal calprotectin and neutrophil gelatinase B-associated lipocalin levels are a valuable addition for assessment of disease activity in asymptomatic ulcerative colitis patients. Biological levels of the analysed biomarkers below the proposed thresholds can rule out the presence of macroscopic and microscopic lesions with a probability of 75-93%. However, caution should be applied whenever interpreting positive results, as these biomarkers present consistently low positive predictive values.
- Acoustic monitoring of O2 production of a seagrass meadowPublication . Felisberto, P.; Jesus, S. M.; Zabel, F.; Santos, Rui; Silva, João; Gobert, S.; Beer, S.; Bjork, M.; Mazzuca, S.; Procaccini, G.; Runcie, J. W.; Champenois, W.; Borges, A. V.Acoustic data were acquired in October 2011 over a Posidonia oceanica meadow in the Bay of la Revellata, Calvi, Corsica. The purpose was to develop an acoustic system for monitoring the oxygen (O2) production of an entire seagrass meadow. In a shallow water area (<38m), densely covered by P. oceanica, a sound source transmitted signals in 3 different bands (400-800Hz, 1.5-3.5kHz and 6.5-8.5kHz) toward three self-recording hydrophones at a distance of 100m, over the period of one week. The data show a high correlation between the diel cycle of the acoustic signals' energy received by the hydrophones and the temporal changes in water column O2 concentration as measured by optodes. The results thus show that a simple acoustic acquisition system can be used to monitor the O2-based productivity of a seagrass meadow at the ecosystem level with high temporal resolution. The finding of a significant production of O2 as bubbles in seagrass ecosystems suggests that net primary production is underestimated by methods that rely on the mass balance of dissolved O2 measurements. © 2015 Elsevier B.V.
- Brazil oil spill response: protect rhodolith bedsPublication . Soares, M. O.; Teixeira, C. E. P.; Bezerra, L. E. A.; Rossi, S.; Tavares, T.; Cavalcante, R. M.; Assis, J.; Silva, João; Santos, Rui; Serrao, EsterIn his News In Depth story “Mystery oil spill threatens marine sanctuary in Brazil” (8 November 2019, p. 672), H. Escobar highlights important ecosystems that have been affected by the spill. However, he did not mention the Brazilian rhodolith beds—the most extensive, abundant, and diverse biogenic carbonate habitats in the South Atlantic (1). The oil spill severely threatens these ecosystems, which comprise a staggering 2 x 1011 tons of carbonatic bank (2), stretch from 5°N to 27°S along the Brazilian coast, and cover a seabed potential area of 229,000 km2 (1).
- Calcification in free-living coralline algae is strongly influenced by morphology: implications for susceptibility to ocean acidificationPublication . Schubert, Nadine; Hofmann, Laurie C.; Almeida Saá, Antonella C.; Moreira, Anderson Camargo; Arenhart, Rafael Güntzel; Fernandes, Celso Peres; de Beer, Dirk; Horta, Paulo A.; Silva, JoãoRhodolith beds built by free-living coralline algae are important ecosystems for marine biodiversity and carbonate production. Yet, our mechanistic understanding regarding rhodolith physiology and its drivers is still limited. Using three rhodolith species with different branching morphologies, we investigated the role of morphology in species' physiology and the implications for their susceptibility to ocean acidification (OA). For this, we determined the effects of thallus topography on diffusive boundary layer (DBL) thickness, the associated microscale oxygen and pH dynamics and their relationship with species' metabolic and light and dark calcification rates, as well as species' responses to short-term OA exposure. Our results show that rhodolith branching creates low-flow microenvironments that exhibit increasing DBL thickness with increasing branch length. This, together with species' metabolic rates, determined the light-dependent pH dynamics at the algal surface, which in turn dictated species' calcification rates. While these differences did not translate in species-specific responses to short-term OA exposure, the differences in the magnitude of diurnal pH fluctuations (~ 0.1-1.2 pH units) between species suggest potential differences in phenotypic plasticity to OA that may result in different susceptibilities to long-term OA exposure, supporting the general view that species' ecomechanical characteristics must be considered for predicting OA responses.
- Causes and effects of wine tourism development in wineries: the perspective of institutional theoryPublication . Lavandoski, Joice; Pinto, Patrícia; Silva, João; Vargas-Sanchez, AlfonsoPurpose - This study aims to propose that the institutional environment exerts pressure on the behavior of wineries toward wine tourism development (WTD) and the effect of this influence confers legitimacy to the business of wine tourism.Design/methodology/approach - Structural equation modeling through partial least squares was applied to estimate and validate a model using data from a quantitative survey in the universe of 62 wineries with a wine tourism component along the Alentejo Wine Route in Portugal. The proposed model is based on institutional theory through an inter-organizational perspective of wineries.Findings - The results show that WTD coexists with a highly institutionalized environment, exerting distinctive mechanisms of external pressure together with the search for social legitimacy through actions and practices on the part of the involved wineries. However, the relationship between legitimacy and organizational performance in wineries with wine tourism is not validated.Research limitations/implications - The specific sample of the Alentejo wine companies does not allow the results to be generalized. Future studies should replicate the proposed research model using other geographic areas.Practical implications - The results are particularly interesting for managers of wineries and should be considered in the decision-making and strategic processes regarding wine tourism.Originality/value - The use of institutional theory in the wine tourism context is novel and original. This study fills a research gap by conducting an empirical investigation of wine tourism based on institutional theory, which allows the identification of exogenous factors that can influence and impose restrictions on the organizational behavior of winery companies toward wine tourism.
- A common terminology to unify research and conservation of coralline algae and the habitats they createPublication . Jardim, Victor L.; Grall, Jacques; Barros‐Barreto, M. Beatriz; Bizien, Anaëlle; Benoit, Thomas; Braga, Juan C.; Brodie, Juliet; Burel, Thomas; Cabrito, Andrea; Diaz‐Pulido, Guillermo; Gagnon, Patrick; Hall‐Spencer, Jason M.; Helias, Mathieu; Horta, Paulo Antunes; Joshi, Siddhi; Kamenos, Nick A.; Kolzenburg, Regina; Krieger, Erik C.; Legrand, Erwann; Page, Tessa M.; Peña, Viviana; Ragazzola, Federica; Rasmusson, Lina M.; Rendina, Francesco; Schubert, Nadine; Silva, João; Tâmega, Frederico T. S.; Tauran, Adeline; Burdett, Heidi L.Linguistic uncertainty is a prime source of uncertainty pervading ecology and conservation. Coralline algae are a widespread and diverse group of calcifying red macroalgae that underpin coastal ecosystem function and service provision. Recent increasing interest in coralline algae in the scientific literature has revealed a diverse but confusing terminology at organism to habitat scales. Coralline algal research and conservation are international and multidisciplinary, so there are geographic and disciplinary imbalances in research and conservation efforts. To reach consensus and reduce uncertainty, we propose a unified terminology. We review trends in cultural and scientific use of coralline algal terms and propose a system based on six morphologies: (1) attached, (2) free-living geniculate, (3) encrusting and free-living nongeniculate coralline algae, the latter either being (4) nucleated or (5) non-nucleated thalli or (6) fragments. We take inspiration from other coastal systems that have achieved consensus through umbrella terms, such as 'coral' and 'kelp', to accelerate global progress in coralline algal research and conservation. We characterise 14 coralline algae-dominated habitat global types, falling within seven functional groups, four biomes and four realms: (1) freshwater coralline streams; (2) coralline tide pools; (3) intertidal coralline rims and (4) turf; (5) coralline sea caves; (6) coral-algal reefs; (7) algal ridges; (8) coralligenous reefs; subtidal (9) carbonate crusts, (10) coralline barrens and (11) turf; and (12) articulith, (13) maerl and (14) rhodolith beds, which fall into the coralline algal bed functional group. We hope this unified terminology promotes data comparison, enables cross-boundary and cross-sector sharing of best practices, develops capacity for meta-analyses and improves conservation strategies.
- Compared photophysiology of native seagrasses with an invasive macroalga in Sydney Harbour, AustraliaPublication . Silva, João; Runcie, J. W.; Barrote, Isabel; Costa, Monya; Santos, RuiThe comparative photophysiology of the seagrasses Zostera capricorni and Halophila ovalis and the invasive macroalgae Caulerpa taxifolia was investigated in a shallow mixed meadow at Chowder Bay (Sydney, Australia), where the three species coexist. This study was developed under the auspices of the COST Action “Seagrasses: from genes to ecosystems”, targeting one of its objectives, the development of innovative devices for the continuous measurement of seagrass photosynthesis. Automated multi-channel chlorophyll fluorometers were deployed for 24-hour periods to examine and compare the changes in the photosynthetic efficiency and energy quenching mechanisms of the 3 species. Tissue samples were collected at predawn and noon, frozen and analysed by HPLC for detailed pigment analysis. The invasive C. taxifolia showed generally higher photosynthetic efficiency than both Z. capricorni and H. ovalis. Both seagrass species showed down-regulation of photosynthesis at noon, evidenced by the low quantum yield and the significant reduction of the antennae pigments between pre-dawn and noon. In contrast, C. taxifolia showed no reduction in antennae pigments or total photosynthetic pigments along the day. While both seagrasses showed 3- to 7-fold increases in the epoxidation state of xanthophyll cycle pigments between pre-dawn and noon, in C. taxifolia there was no significant change. Our results show that C. taxifolia is better adapted to high light conditions than Z. capricorni and H. ovalis, which means that, from the photophysiological point of view, this invasive macroalgae constitutes a serious competitor for seagrasses in shallow areas with high irradiance.