Sapientia
Repositório Científico da UAlg
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Consortium of microalgae/nitrogen-fixing bacteria as a next-generation biofertilizer, biostimulant and biopesticide
Publication . Gouveia, Luisa; Ferreira, Alice; Bastos, Carolina Vela; Avetisova, Gayane; Karapetyan, Zhaneta; Toplaghaltsyan, Anna; Melkonyan, Lusine
This study aims to provide insights into a new consortium of a microalga, twelve nitrogen-fixing (N-fixing) bacteria and a cyanobacterium. The microalga Tetradesmus obliquus (T), in conjunction with various N-fixing bacteria and the cyanobacterium Synechocystis sp. PCC 6803 (S), the N-fixing bacterium Sphingobacterium sp. L13G8 (5), cultivated in complete Bristol medium and in Bristol-NaNO3 free conditions, were examined. The study encompassed the analysis of their consortia, including evaluation of their growth, and potential as a biostimulant, biofertilizer and biopesticide, and assessed for sedimentation performance for targeted applications. The T and N-fixing bacteria consortia had higher growth in Bristol NaNO3-free media. The triple culture TS5 had the highest growth parameter (2.4 OD540) in the same medium, followed by T5. The consortia were employed to ascertain the efficacy of their biostimulants and biofertilizers on watercress (Lepidium sativum) and to determine the potency of their biopesticides against the fungal pathogens Fusarium oxysporum and Rhizoctonia solani (in certain consortia). Consortium T5 demonstrated the most significant impact on the seeds germination index (212.7%) and root length (6.0 cm) of L. sativum. The same consortium had a significant impact on the shoot length (4.4 cm) of L. sativum. Among all consortia that were examined, T5 exhibited significant inhibitory effects on the growth of F. oxysporum (60.6%) and R. solani (69.2%). In the same consortium, the rate of microalgal biomass sedimentation was enhanced by the N-fixing bacterium (0.4 cm h−1). Consortium T5 was the most effective in relation to growth and biomass sedimentation efficiency, in addition to its use as a biostimulant, biofertilizer and biopesticide. The created combination of microalga and N-fixing bacterium represents significant progress in the field of microalga cultivation, with notable benefits including improved biomass sedimentation and enhanced agricultural practices, as well as environmental friendliness and safety.
First assessment of blue carbon stocks, sequestration rates and potential sources since 1900 at Arguin Island (Mauritania)
Publication . Martins, Márcio; Abrantes, Fatima; Aires, Tania; Rautenbach, Sarah; Engelen, Aschwin; Encarnação, João Pedro da Silva; Abecasis, David; Gandega, Cheikhna; Magalhães, Vitor; Brahim, Khallahi; Ebaye, Sidina; Barusseau, Jean-Paul; Freiwald, André; Barrena de los Santos, Carmen; Serrao, Ester A.; Santos, Rui
Global blue carbon assessments are hindered by a lack of data from understudied seagrass regions, such as those of Western Africa. This study reports the first in situ records of organic carbon (OC) stocks and burial rates for seagrass beds at Arguin Island, Banc d'Arguin (Mauritania), Western Africa, measured in intertidal Zostera noltei and subtidal Cymodocea nodosa meadows. The major blue carbon sources in seagrass meadows since 1900 were assessed using sedimentary environmental DNA (eDNA) and chronostratigraphy. The OC stocks in the top 50 cm of the sediment cores were not significantly different between the beds of the two seagrass species and averaged 27.8±7.14 Mg C ha−1, which is 5 times higher than that in adjacent unvegetated sediments. The OC sequestration rate for the past 100 years was 10.3±1.4 g C m−2 year−1 in C. nodosa sediments and 12.3±5.9 g C m−2 year−1 in Z. noltei sediments. Sedimentary eDNA analysis revealed that the major OC source within the C. nodosa and Z. noltei sediments has been the seagrass species itself, with low contributions from allochthonous eDNA reads. Carbon sources in Z. noltei meadows were more diverse than those in C. nodosa meadows. In bare sediment, diatoms were the major carbon source. The present study demonstrates the potential of sedimentary eDNA to reveal the major sources of organic matter in blue carbon ecosystems, improving our understanding of the provenance of sedimentary OC and thus carbon cycling processes. Additionally, it provides new OC stock and sequestration rate measurements from a region of the world that remains underrepresented in global blue carbon assessments.
High variability in aggression and habituation to the mirror assay in ornamental Siamese fighting fish Betta splendens
Publication . Coelho da Silva, Melina; Canario, Adelino; Hubbard, Peter; Cardoso, Sara D.; Gonçalves, David
Understanding consistent inter-individual variability in animal behaviour, known as personality traits, is essential for exploring the mechanisms and evolutionary consequences of behavioural diversity. Aggressive behaviour influences survival, resource acquisition, and reproduction, so clarifying individual differences can enhance our understanding of ecological dynamics and improve experimental design accuracy in behavioural studies. In this study, ornamental male Betta splendens, a model organism for aggression research, were analysed for intra- and inter-individual variability in aggressive responses to their mirror image—a standard method for assessing aggression in fish—once per week, and their consistency was evaluated over three consecutive weeks There were significant differences in aggressive behaviour across individuals, with coefficients of variation ranging from 29 to 60%. While most fish exhibited the full suite of aggressive displays, some showed no aggressive behaviour, while others only displayed threat behaviours but did not advance to the attacks. The consistency of individual threat and attack behaviours varied, but repeatability was high overall (intra-class correlation coefficients≥0.5), indicating that individual fish have different levels of aggression. There was habituation to the mirror assay, with aggression decreasing significantly by the second week, though the degree of habituation, a form of learning, varied among individuals in some behaviours. Air-breathing frequency correlated positively with aggression behaviours and can be considered an indicator to infer aggression level in this species. These results indicate that inter-individual variation in aggressive behaviour and habituation to repeated testing using the mirror assay should be considered in aggression studies using B. splendens and potentially in other species.
Asymmetric connectedness among regional green economies, carbon markets, and oil shocks
Publication . Hanif, Waqas; El Khoury, Rim; Gubareva, Mariya; Teplova, Tamara
This study investigates spillovers among the US, Europe, and Asia green economies, carbon allowances and oil price shocks in 2010–2023. We segregate oil shocks in demand-, supply-, and risk-driven price movements. The TVP-VAR methodology is applied to model the dynamic interrelationships among the markets. Our static connectedness outcomes highlight a substantial role of the US and European green economy and the demand-driven shocks as emitters of innovations to other markets. It is found that European green economy is the main innovations contributor to global carbon allowances whereas the demand-driven oil shocks dominate in transmitting spillovers to others. We demonstrate that major economic events make connectedness increase. Our asymmetry analysis reveals a heightened susceptibility of the system to negative news, with the impacts of negative spillovers overcoming those of positive ones. The dynamics of spillovers emphasize how crucial it is to take into account both the time and the sign. Our research advances understanding of the complex relationships within the green-carbon-oilshocks system. The results are potentially useful for risk managers and investors, as they allow the creation of effective risk management plans.
Assessing the role of CT imaging in identifying candidates for neoadjuvant chemotherapy in right colon cancer: a critical analysis
Publication . Lopes, João Leão; Soares, Ana Sofia S.; Mendes, Beatriz; Tomada, Elisa Paoluzzi; Cunha, Miguel F.; Melina Fernandez, Laura; Amorim, Edgar; Azevedo, José; Parvaiz, Amjad
Background and purpose Standard treatment for localized right colon cancer is radical surgery, followed by adjuvant chemotherapy for stage III or intermediate MSS and high-risk stage II tumours. Recent studies suggest a benefit from neoadjuvant chemotherapy (NAC), particularly for T4b and/or N+tumours. Patient selection for NAC relies on CT-based clinical staging, but the accuracy of CT in detecting high-risk features is variable, raising concerns about potential overtreatment. The study aims to demonstrate the accuracy of CT staging of the right colon with the purpose of indicating neoadjuvant CT. Methods Patients undergoing curative right hemicolectomy between 2013 and 2023 at two Portuguese institutions were included. All had preoperative CT; those receiving NAC were excluded. Sensitivity, specificity, positive predictive value, and negative predictive value of CT in identifying T4b and N+tumours were calculated by comparing clinical (cTNM) and pathological (pTNM) staging. Results Among 165 patients (48% male, mean age 70.5 years), CT showed low sensitivity (26%) but high specificity (91%) for pT4b tumours, with a tendency toward understaging. For nodal disease, sensitivity was 87% and specificity 41%. Only 57% of cT4b and/or cN+cases confirmed at least one unfavorable pathological factor, implying potential overtreatment in 43% of patients if NAC were applied solely based on CT findings. Conclusion CT remains the standard for clinical staging but demonstrates limited accuracy in identifying high-risk right colon cancers. NAC decisions should integrate additional criteria beyond CT findings to avoid overtreatment.