Influence of Microcystis sp. and freshwater algae on pH: changes in their growth associated with sediment

Samples from two reservoirs with eutrophication problems, located in Pontevedra and Ourense (Northwestern Spain), were cultured, along with a third crop from a reservoir with no problems detected in Ourense (Northwestern Spain). The samples were grown under the same conditions (with an average temperature of 21 ± 2 °C, and a 3000 lux light intensity) in triplicate, and their growth, absorbance and pH were studied. High correlation values were obtained for pH and cellular growth (R2 ≥ 95%). The water from Salas showed the greatest microalgal growth (0.15 × 106 cells/ml to 31.70 × 106 cells/ml of "Microcystis sp." for the last day of culturing) and the greatest increase in pH (5.72–9.02). In all the cultures studied here, the main species that reproduced was "Microcystis sp.", which can produce neurotoxins and hepatotoxins. In addition, water samples were cultured with sediments of their own reservoir and with others to observe their evolution. The sediments studied in this case were rich in biotites, which can lead phosphate to be a limiting factor for phytoplankton due to the formation and sedimentation of insoluble salts of ferric phosphate. In crops grown with sediments from the Salas reservoir, actinobacteria developed which can inhibit microalgal growth. The study of the growth of cyanobacteria and possible methods of inhibiting them directly concerns the quality of water and its ecosystems, avoiding pollution and impact on ecosystems

Water toxicity in reservoirs after freshwater algae harvest

Blooms of microalgae and cyanobacteria increase every year, presenting great problems for the environment. Finding a way of harvesting these microalgae could be useful for water governance. Furthermore, the method should not cause cell lysis and should thus avoiding discharging toxins into the water. Three reservoirs were studied, two of them with eutrophication problems (As Conchas and A Baxe) and another (Salas) with no such problems. Three different harvesting methods were studied; electroflocculation (EF) with the application time being varied; centrifugation, with application times and speeds being varied; and finally, natural sedimentation. The highest efficiency was obtained in the culture from A Baxe, which had a higher initial absorbance value (1.664), using EF (90.64% for an application time of 2 min and 30 s) and centrifugation at 4000 rpm (92.25% for2 minutes, 92.73% for 5 min). Electrofloculation can obtain up to 84% more biomass than natural sedimentation alone. Sample toxicity was studied before and after harvesting using Microcystest and found to be higher after harvesting. It was observed that for the same sample, the higher the yield was the greater the toxicity was. For the A Baxe culture with an application time of 2 min, a speed of 2000 rpm and a yield of 87.02%, a toxicity figure of 0.94 μg/L was obtained, while for a speed of 4000 rpm the yield was 92.25% and the toxicity was 1.05 μg/L. The toxicity limit set by the World Health Organization (WHO) is 1 μg/L, and this small difference seems to be key. With these results, this study concludes that chlorophyll levels may interfere with the test used. Future tests or analyses should be developed so as to avoid such interference, which may alter the toxin values. Electroflocculation seems to be a promising method since it does not cause the lysis of "Microcystis aeruginosa", whereas the centrifugation method could give problems. Finally, it is worth highlighting the importance of performing toxin measurements after harvesting the microalgae to check that the method is viable in natural ecosystems

Influence of ashes in the use of forest biomass as source of energy

One of the main challenges using biofuels, such as pellets or wood chips in domestic boilers, is the slagging and fouling risks associated to the process, which could damage the boiler and limit its efficiency. The prediction of sintering and slagging in biomass combustion is essential to establish biofuel quality standards, and minimize their harmful effects. In this work, we analysed the chemical composition of 40 woodchips samples from different genera and origins in order to predict slagging. We studied two indexes of deposition (%B and the NaK/B) in order to limit sintering of biomass ashes. In addition, a new threshold classification was proposed for ratio-slag viscosity index. These indexes were validated with two different tests: a qualitative test, and a quantitative test (Bioslag). Our results showed that the species chosen did not have an impact in slagging and sintering. However, biomass with high concentrations of SiO2 and tree bark showed high risk of slagging. On the other hand, high CaO concentrations showed a low slagging risk. The results obtained from the validation tests showed similar results to the ones obtained from the indexes. It can be concluded that the %B and NaK/B indexes show good potential and should be considered as tools for predicting slagging in woody and herbaceous biomass

Water security and watershed management assessed through the modelling of hydrology and ecological integrity: a study in the Galicia-Costa (NW Spain)

Water management is a crucial tool for addressing the increasing uncertainties caused by climate change, biodiversity loss and the conditions of socioeconomic limits. The multiple factors affecting water resources need to be successfully managed to achieve optimal governance and thus move towards water security. This study seeks to obtain a holistic vision of the various threats that affect the ecological integrity of the basins that form the hydrological district of Galicia-Costa, through the method of partial least squares path modelling (PLS-PM). The data is analysed overall for the hydrological years from 2009 to 2015. The independent latent variables are “Anthropogenic” (comprising the percentage of water bodies with edges alongside artificial surfaces, the percentage connected to artificial land use patches, the edge density of artificial surfaces and population density) and “Nature” (edge density of forestry land uses, edge length of land water bodies alongside forested areas and the percentage of land occupied by the largest patch of forest). The dependent latent variables are “SWP”, which represents surface water parameters (biological oxygen demand, chlorides, conductivity and dissolved iron) and “Ecological Integrity” (METI Bioindicator). The connections between latent variables are uantified through path coefficients (β). From an overall perspective, the PLS-PM results reveal that 69.0% of “SWP” is predicted by the independent variables (R2 = 0.690), “Anthropogenic” contributes by increasing SWP (β = 0.471), while “Nature” decreases the concentration of SWP (β = −0.523), which indicates the polluting parameters in the water. The variables “Anthropogenic” (β = −0.351) and “SWP” (β = −0.265) lower the quality of “Ecological Integrity”. This variable must be managed through soil conservation measures for the benefit of water security. This study has been able to identify and quantify the variables that increase contaminant concentration and decrease ecological integrity, providing a promising methodology that facilitates protection and correction measures to guarantee water safety.Xunta de Galicia | Ref. R815 131H 64502Fundação para a Ciência e a Tecnologia | Ref. UID/AGR/04033/2020Fundação para a Ciência e a Tecnologia | Ref. UIDB/QUI/00616/2020Fundação para a Ciência e a Tecnologia | Ref. UIDP/00616/2020Fundação para a Ciência e a Tecnologia | Ref. SFRH/BD/146151/201

Connectivity study in Northwest Spain: barriers, impedances, and corridors

Functional connectivity between habitats is a fundamental quality for species dispersal and genetic exchange throughout their distribution range. Brown bear populations in Northwest Spain comprise around 200 individuals separated into two sub-populations that are very difficult to connect. We analysed the fragmentation and connectivity for the Ancares-Courel Site of Community Importance (SCI) and its surroundings, including the distribution area for this species within Asturias and in the northwest of Castile and León. The work analysed the territory’s connectivity by using Geographic Information Systems (GIS). The distance-cost method was used to calculate the least-cost paths with Patch Matrix. The Conefor Sensinode software calculated the Integral Connectivity Index and the Connectivity Probability. Locating the least-cost paths made it possible to define areas of favourable connectivity and to identify critical areas, while the results obtained from the connectivity indices led to the discovery of habitat patches that are fundamental for maintaining connectivity within and between different spaces. Three routes turned out to be the main ones connecting the northern (Ancares) and southern (Courel) areas of the SCI. Finally, this work shows the importance of conserving natural habitats and the biology, migration, and genetic exchange of sensitive species.Xunta de Galici

Modelling of threats that affect Cyano-HABs in an eutrophicated reservoir: First phase towards water security and environmental governance in watersheds

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGCyano-HABs are proliferating around the world due to anthropogenic nutrient enrichment of freshwater bodies. This study seeks to obtain a holistic vision over the various threats that affect the Cyano-HABs of Umia basin and especially of A Baxe reservoir (Galicia, NW Spain), through the method of Partial least squares path modelling (PLS-PM). The A Baxe reservoirs is a fundamental source of drinking water supply to surrounding dwellings. This study identifies and quantify the variables that increase contaminant concentration and decrease ecological integrity, as well as how this scenario evolved over various hydrologic years. In this regard, the PLS-PM equations will be robust and powerful tools to predict changes in eutrophication and ecological integrity, as response to measures implemented in the basin that can improve water quality. The dependent latent variables are “Eutrophication” (chlorophyl-a, Microcystis sp.) and “Ecological Integrity” (METI Bioindicator). The independent latent variables are “SWP”, which represents surface water parameters (phosphorus, nitrogen and pH) and “Climatic Conditions” (temperature, precipitation). The PLS-PM results revealed that 51.0% of “Eutrophication” is predicted by the independent variables. The connections between latent variables are quantified through path coefficients (β). The “SWP” contributes by increasing “Eutrophication” (β=0.235), the same occurring with the “Climatic Conditions” (β=−0.672). The variables “Eutrophication” (β=−0.217) and “SWP” (β=−0.483) lower the “Ecological Integrity”. On the other hand, different trophic scenarios, adapted to the temperature increase predicted for the study area, were tested, and it was found that ecological integrity would improve by 46% if the oligotrophic state were reached. Therefore, it is recommended to prevent pollution by means of water control and governance plans, as well as corrective and preventive measures, which guarantee the water security of the river basins. Despite the complex mathematics behind the PLS-PM models, their user-friendly development and application through interactive graphical interfaces make them easily transposable to other eutrophic reservoirs, widening the readership of these studies focused on multiple-geosphere assessment of environmental impactsFundação para a Ciência e a Tecnologia | Ref. UIDB/00616/2020Fundação para a Ciência e a Tecnologia | Ref. UIDP/00616/ 2020.Xunta de Galicia | Ref. R815 131H 6450

Influence of small hydroelectric power stations on river water quality

Hydropower electricity generation is considered one of the cheapest technologies regarding electricity generation costs, and it is the most traditional, clean, renewable energy source. However, despite the environmental benefits offered by hydropower, they also can have negative impacts and consequences in the environment affecting water quality and disrupting river ecology. We investigated the environmental effects of four small hydropower plants (SPH) in north-west Spain by looking at the water quality of the four river stretches where the SPH plants are located. The physicochemical and biological characteristics of the water streams were analyzed, as well as the riparian ecological quality. Results showed that the presence of the hydropower plants did not significantly influence the physical and chemical characteristics of the water. There were no alterations of the benthic macroinvertebrate community at any of the plants except for one, and the riparian habitat was in general classified as good quality or close to natural conditions for all plants.TASG

Hydrothermal carbonization and pellet production from Egeria densa and Lemna minor

Biofuels are seen as a potential option for mitigating the effects of fossil fuel use. On the other hand, nutrient pollution is accelerating eutrophication rates in rivers, lakes, and coastal waters. Harvesting aquatic plants to produce biofuels could mitigate this problem, though it is important to attack the problem at source, mainly as regards the contribution of nutrients. For the first time, solid biofuels were obtained in the forms of carbon and pellets from the aquatic plants Egeria densa, which is classed as an invasive plant under the Spanish Catalogue of Exotic Invasive Species, and Lemna minor, both of which can be found in the Umia River in north-west Spain. The essential oils and macro- and microelements present in both these plants were also extracted and analyzed. The higher heating values (HHVs) of the carbon products obtained ranged from 14.28 to 17.25 MJ/kg. The ash content ranged from 22.69% to 49.57%. The maximum yield obtained for biochar for Egeria densa at 200 °C was 66.89%. Temperature significantly affects solid hydrochar yield. The HHVs of the pellets obtained ranged from 11.38 to 13.49 MJ/kg. The use of these species to obtain biofuels through hydrothermal carbonization (HTC) and pellets is a novel and effective approach that will facilitate the removal of nutrients that cause eutrophication in the Umia River. The elements extracted show that harvesting these plants will help to remove excessive nutrients from the ecosystem

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)