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Macroalgal holobiont studies involve understanding interactions between the host, its microbiota, and the environment. We analyzed the effect of bacteria-kelp interactions on phenotypic responses of two genetically distinct populations of giant kelp, Macrocystis pyrifera (north and south), exposed to different nitrogen (N) concentrations. In co-culture experiments with different N concentration treatments, we evaluated kelp growth responses and changes in three specific molecular markers associated with the N cycle, both in epiphytic bacteria (relative abundance of nrfA-gene: cytochrome c nitrite reductase) and macroalgae (expression of NR-gene: nitrate reductase; GluSyn-gene: glutamate synthase). Both kelp populations responded differently to N limitation, with M. pyrifera-south sporophytes having a lower specific growth rate (SGR) under N-limiting conditions than the northern population; M. pyrifera-north sporophytes showed no significant differences in SGR when exposed to low-N and high-N concentrations. This corresponded to a higher GluSyn-gene expression in the M. pyrifera-north sporophytes and the co-occurrence of specific nrfA bacterial taxa. These bacteria may increase ammonium availability under low-N concentrations, allowing M. pyrifera-north to optimize nutrient assimilation by increasing the expression of GluSyn. We conclude that bacteria-kelp interactions are important in enhancing kelp growth rates under low N availability, although this effect may be regulated by the genetic background of kelp populations.

Convective heat transfer has been proven to offer vast potential to increase the efficient use of energy in various processes in both industry and everyday life. However, standard methods for improving convective heat transfer appear to have reached their limits. The application of classical nanofluids and ferronanofluids is a new strategy to overcome these limits. This chapter provides an overview of the state of the art regarding experimental investigations of convective heat transfer employing such suspensions. As discussed in the literature, and also revealed by experiments, there are no anomalous effects. Further detailed investigations need to be conducted to develop nanofluids and ferronanofluids as robust heat transfer fluids for use in industrial applications. The focus should be on the development of nanofluids with a strong increase in thermal conductivity but only slightly increased viscosity.

Early naturalists suggested that predation intensity increases toward the tropics, affecting fundamental ecological and evolutionary processes by latitude, but empirical support is still limited. Several studies have measured consumption rates across latitude at large scales, with variable results. Moreover, how predation affects prey community composition at such geographic scales remains unknown. Using standardized experiments that spanned 115° of latitude, at 36 nearshore sites along both coasts of the Americas, we found that marine predators have both higher consumption rates and consistently stronger impacts on biomass and species composition of marine invertebrate communities in warmer tropical waters, likely owing to fish predators. Our results provide robust support for a temperature-dependent gradient in interaction strength and have potential implications for how marine ecosystems will respond to ocean warming.

The capacity of marine organisms to adapt and/or acclimate to climate change might differ among distinct populations, depending on their local environmental history and phenotypic plasticity. Kelp forests create some of the most productive habitats in the world, but globally, many populations have been negatively impacted by multiple anthropogenic stressors. Here, we compare the physiological and molecular responses to ocean acidification (OA) and warming (OW) of two populations of the giant kelp Macrocystis pyrifera from distinct upwelling conditions (weak vs strong). Using laboratory mesocosm experiments, we found that juvenile Macrocystis sporophyte responses to OW and OA did not differ among populations: elevated temperature reduced growth while OA had no effect on growth and photosynthesis. However, we observed higher growth rates and NO3− assimilation, and enhanced expression of metabolic-genes involved in the NO3− and CO2 assimilation in individuals from the strong upwelling site. Our results suggest that despite no inter-population differences in response to OA and OW, intrinsic differences among populations might be related to their natural variability in CO2, NO3− and seawater temperatures driven by coastal upwelling. Further work including additional populations and fluctuating climate change conditions rather than static values are needed to precisely determine how natural variability in environmental conditions might influence a species’ response to climate change.

The contact angle of droplets attracts attention as one of the relevant thermophysical properties describing the wettability behaviour of the fluids. The contact angle depends on the surface characteristics such as surface type and roughness as well as on the liquid type and surrounding atmosphere. This study aims to correct the error in the coefficient of the theoretical model developed for droplet shape prediction by Vafaei and Podowski [1]. The corrected model is also rearranged by non-dimensional numbers. The contact angle and the shape of water droplets for different volumes and surface types are predicted by the rearranged model and validated by experimental results. Contact angles have been over-estimated compared to experimental results because of measurement errors in geometrical parameters. It is found that the contact angle model is too sensitive to geometrical parameters. Moreover, the contact angle is found to be independent of the volume.

13 pages, 6 figures, 2 tables.-- This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License, The rapid, global spread of COVID-19, and the measures intended to limit or slow its propagation, are having major impacts on diverse sectors of society. Notably, these impacts are occurring in the context of other anthropogenic-driven threats including global climate change. Both anthropogenic stressors and the COVID-19 pandemic represent significant economic challenges to aquaculture systems across the globe, threatening the supply chain of one of the most important sources of animal protein, with potential disproportionate impacts on vulnerable communities. A web survey was conducted in 47 countries in the midst of the COVID-19 pandemic to assess how aquaculture activities have been affected by the pandemic, and to explore how these impacts compare to those from climate change. A positive correlation between the effects of the two categories of drivers was detected, but analysis suggests that the pandemic and the anthropogenic stressors affect different parts of the supply chain. The immediate measurable reported losses varied with aquaculture typology (land vs. marine, and intensive vs. extensive). A comparably lower impact on farmers reporting the use of integrated multitrophic aquaculture (IMTA) methods suggests that IMTA might enhance resilience to multiple stressors by providing different market options under the COVID-19 pandemic. Results emphasize the importance of assessing detrimental effects of COVID-19 under a multiple stressor lens, focusing on areas that have already locally experienced economic loss due to anthropogenic stressors in the last decade. Holistic policies that simultaneously address other ongoing anthropogenic stressors, rather than focusing solely on the acute impacts of COVID-19, are needed to maximize the long-term resilience of the aquaculture sector., The Open Access publication of the MS was funded by M. Cristina Mangano FOE N. 418 at Stazione Zoologica Anton Dohrn (personal OA publication fund). People at Laboratory of Ecology have been found by the PRIN-MAHRES project (Ministry of Italian Research; MUR) 2017MHHWBN_003 Linea C and by the HARMONY Project Italy-Malta 2016 (grant C1-3.1-31) funded by the Sicilian Region and Maltese Government. A. Nogueira thanks FCT/MCTES for the financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020), through national funds. J.M.F. Babarro thanks project PID2019-106008RB-C21 for support through Spanish Government funds

Thermosyphons are among the most efficient passive heat transfer devices known nowadays. Due to heat and mass transfer limitations of working fluids, much effort is invested in developing a new gen...

Epiphytism is a common phenomenon in macroalgal aquaculture worldwide. This problem can affect the productivity and quality of the farmed species which may have socioeconomic consequences for the human communities that depend on this activity. In southern Chile, the aquaculture of the red macroalga Agarophyton chilense in the area of Maullin River has suffered losses in local production (> 90%) due to the proliferation of the filamentous green epiphyte Rhizoclonium sp. This epiphyte becomes entangled with A. chilense fronds, diminishing its quality and preventing its sale as raw material. Thus, the aim of this study was to investigate the effects of light intensity (90 and 180 μmol photons m−2 s−1) on the competitive interaction between the epiphyte Rhizoclonium sp. and the basiphyte A. chilense co-cultured at different initial biomass proportions in a replace series experiment. At the end of the experiment, the presence of Rhizoclonium sp. did not affect negatively the growth of A. chilense, but both species showed stress responses (i.e. reduced Fv/Fm and C:N ratio, suggesting nutrient limitation) in co-culture compared with monocultures. The epiphyte-basiphyte interaction was not modulated by light availability at any initial co-culture proportion and could have been related to nutrient availability during experimentation. Using the replacement series approach, an interspecific competition was observed at all initial co-culture proportion under 180 μmol photons m−2 s−1 while competition was found at the initial co-culture 1:1 under 90 μmol photons m−2 s−1. Our results suggest that the interaction in co-culture between both A. chilense and Rhizoclonium sp. seems to be regulated by nutrient availability as well as it demands utilization rather than light availability.

Background Although blood cultures (BCs) are the "gold standard" for detecting bacteremia, the utility of BCs in patients with community-acquired pneumonia (CAP) is controversial. This study describes the proportion of patients with CAP and afebrile bacteremia and identifies the clinical characteristics predicting the necessity for BCs in patients who are afebrile. Methods Bacteremia rates were determined in 4,349 patients with CAP enrolled in the multinational cohort study The Competence Network of Community-Acquired Pneumonia (CAPNETZ) and stratified by presence of fever at first patient contact. Independent predictors of bacteremia in patients who were afebrile were determined using logistic regression analysis. Results Bacteremic pneumonia was present in 190 of 2,116 patients who were febrile (8.9%), 101 of 2,149 patients who were afebrile (4.7%), and one of 23 patients with hypothermia (4.3%). Bacteremia rates increased with the CURB-65 score from 3.5% in patients with CURB-65 score of 0 to 17.1% in patients with CURB-65 score of 4. Patients with afebrile bacteremia exhibited the highest 28-day mortality rate (9.9%). Positive pneumococcal urinary antigen test (adjusted OR [AOR], 4.6; 95% CI, 2.6-8.2), C-reactive protein level > 200 mg/L (AOR, 3.1; 95% CI, 1.9-5.2), and BUN level ≥ 30 mg/dL (AOR, 3.1; 95% CI, 1.9-5.3) were independent positive predictors, and antibiotic pretreatment (AOR, 0.3; 95% CI, 0.1-0.6) was an independent negative predictor of bacteremia in patients who were afebrile. Conclusions A relevant proportion of patients with bacteremic CAP was afebrile. These patients had an increased mortality rate compared with patients with febrile bacteremia or nonbacteremic pneumonia. Therefore, the relevance of fever as an indicator for BC necessity merits reconsideration.

BACKGROUND: Bio‐oils can be effectively used for the preparation of bio‐based materials owing to their chemical compositions. In this study, brown macroalgal‐derived bio‐oil was used for the synthesis of graphene oxide‐carbon dot composite by a simple hydrothermal process. RESULTS: A simple and facile hydrothermal process was explored for the preparation of green‐emitting graphene oxide‐carbon dot (GO‐CD) composite from brown macroalgal biomass‐derived bio‐oil as carbon source in water medium at 170 °C for 4 h. An aqueous solution of the prepared GO‐CD composite exhibited green emission under ultraviolet (UV) radiation exposure. Raman spectroscopy and transmission electron microscopy analyses confirmed the successful formation of GO‐CD composite. Physicochemical characterizations such as phase structure and optical properties of the GO‐CD were investigated by X‐ray diffraction, UV–visible and photoluminescence analyses. The effects of the GO‐CD composite on the seed germination of mung bean were studied. It was found that, compared with the control (100/0 vol% water; total length of plant ∼20 cm), the 75/25 vol% water/GO‐CD ratio treatment resulted in better plant growth (total length of plant ∼25 cm) under the studied conditions. Further increase in GO‐CD concentration above the optimum level resulted in a decrease in plant growth but did not have a significant effect on the mass, root and leaf mass development. CONCLUSION: Brown macroalgal bio‐oil‐derived graphene oxide‐carbon dot composite were explored for the seed germination of mung bean and the results showed that a low concentration enhanced the plant growth. © 2019 Society of Chemical Industry

Experiments with a two-phase closed thermosyphon are carried out with the aim of investigating the influence of different working fluids on geysering. The length of the analysed device is 1.800 mm and its inner diameter is 20 mm. It is filled with various working fluids: from pure deionised-water and deionised-water plus sodium dodecyl sulphate (surfactant) as reference fluids to two different gold nanofluids, a silica nanofluid, and a nanofluid with nanohorn nanoparticles. Thermal performance of the thermosyphon is investigated with respect to time averaged parameters, such as amount of heat transferred, thermal resistance, and temperature distribution in the working fluid sump, but also with respect to geysering frequency and time dependent internal pressure. The inlet temperature of heating water is controlled between 35 °C and 85 °C and of the cooling medium between 15 °C and 25 °C. The most important conclusion is that geysering is strongly affected not only by nanoparticles, but also by chemical stabilisers like sodium dodecyl sulphate or polyvinylpyrrolidone. It is shown experimentally that nanofluids consisting of base fluid, chemical stabiliser, and nanoparticles in some cases diminish or even completely suppress geysering. Effects related to the nanoparticles alter the solid-vapour interface (a nanoporous layer on the evaporator wall) and the vapour-liquid interface (bubble surface). The influence of nanoparticles is restricted to the evaporator section. Replacing water with one of the other studied solutions/suspensions shifts the working point of the thermosyphon, changing the amount of transferred heat (increase even up to 80% for low evaporator temperature) and operating temperature levels.

The demand for seaweed biomass for hydrocolloid industries and novel products for the food, pharmaceutical, cosmetics and agro-industry has been steadily increasing during the last decade. This trend is expected to continue into the future as new uses are discover and the ever-increasing human population needs for healthy products and clean energy expand beyond land-based resources. Seaweed farming still faces constraints for its development and one of them is its economic profitability as in general the seaweed biomass has a rather low value with few exceptions of some species used for human consumption. Therefore, there is a need to increase production of seaweed biomass, but there is still a lack of realistic economic assessments that determine the economic potentiality of a seaweed farming project to attract investors. This article reports an economic model, fed with data of a pre-commercial Macrocystis pyrifera 21-ha pilot farm installed in southern Chile. The economic sensitivity analysis revealed that cultivation of M. pyrifera in southern Chile is profitable in a 10-ha cultivation system when the market price is at least US$ 87 wet t−1 and yields are kept at a minimum of 12.4 kg m−1. We discuss the potential that seaweed cultivation has in Chile and we agree with previous studies that value, productivity and the farming model used are key factors for the economic success of seaweed farming.

International audience; During the domestication process, farmers influence the reproduction and care of organisms to ensure a predictable supply of the resource of interest, causing changes in phenotypic and genotypic character frequencies. In Chile, as a result of unconscious selection and domestication process, farmed populations of the red alga Agarophyton chilensis have most likely undergone a reduction in genetic diversity and a modification in life-history traits compared to wild populations. In order to understand the implications that these processes may have in A. chilensis, we investigated how temperature variations (10 °C, 15 °C, and 20 °C) affect growth and photosynthetic responses of natural and farmed populations from three different localities along the Chilean coast. Natural population’s growth decreased at low and high temperature levels while all three farmed populations respond in a very similar way to temperature variation. We propose that a possible outcome of farming, in the A. chilensis, vegetatively propagated crops, could have been the selection of general-purpose-genotypes able to perform adequately across the range of temperature tested in our experiment. Furthermore, our results showed that photosynthetic activity was also affected by temperature treatments (e.g., different maximum maximal electron transport rate and quantum yield values depending on the population type and temperature). In a context of climate change, A. chilensis farmed populations may be better able to cope with impacts of anthropogenic activities than natural populations due to the buffer effect of their general-purpose-genotypes, tolerant to a wide range of conditions.

Chile, located in the southeastern Pacific, possess a high richness of seaweed species, some of which have been traditionally extracted from natural beds for the production of hydrocolloids (e.g. agar, carrageenan and alginates), but still a high proportion of the biomass is being exported as dried material to processors in Asia and Europe. During the period 2006–2016, this tendency has been maintained, but has also started to show signs of changing towards a more sustainable, localized seaweed industry as new actions by the Chilean government provided subsidies to seaweed farming activities and also to investments in local valorization of the resources. This “sea change” has been further supported by an increase in the number of localized scientific and technical studies related to Chilean seaweed resources which has prepared the foundation required in order to move to more advanced stages of local seaweed farming and development of local processing.

In terrestrial plants, it is well known that genetic diversity can affect responses to abiotic and biotic stress and have important consequences on farming. However, very little is known about the interactive effects of genetic and environmental factors on seaweed crops. We conducted a field experiment on Gracilaria chilensis to determine the effect of heterozygosity and nutrient addition on two southern Chilean farms: Ancud and Chaica. In addition to growth rate and productivity, we measured photosynthetic responses, photosynthetic pigment concentration (chlorophyll a and phycobiliproteins), C:N ratio (C:N), and epiphytic load. Nutrient addition affected the growth rate, productivity, phycobilin, and C:N content, but not the epiphytic load. These results were independent of the heterozygosity of the strains used in the experiments. Interestingly, depending on the sampled sites, distinct photosynthetic responses (i.e., maximal quantum yield, Fv /Fm , and maximal electron transport rate, ETRmax ) to nutrient addition were observed. We propose that thallus selection over the past few decades may have led to ecological differentiation between G. chilensis from Chaica and Ancud. The lack of effect of heterozygosity on growth and physiological responses could be related to the species domestication history in which there is a limited range of genetic variation in farms. We suggest that the existing levels of heterozygosity among our thalli is not sufficient to detect any significant effect of genetic diversity on growth or productivity in Metri bay, our experimental site located close to the city of Puerto Montt, during summer under nitrogen limiting conditions.

Magnetic influence on ferronanofluid flow is gaining increasing interest from not only the scientific community but also industry. The aim of this study is the examination of the potentials of magnetic forces to control heat transfer. Experiments are conducted to investigate the interaction between four different configurations of permanent magnets and laminar pipe flow with mixed convection. For that purpose a pipe flow test rig is operated with a water-magnetite ferronanofluid. The Reynolds number is varied over one order of magnitude (120–1200). To characterise this suspension, density, solid content, viscosity, thermal conductivity, and specific heat capacity are measured. It is found that, depending on the positioning of the magnet(s) and the Reynolds number, heat transfer is either increased or decreased. The experiments indicate that this is a local effect. After relaxation lengths ranging between 2 and 3.5 lengths of a magnet, all changes disappeared. The conclusion from these findings is that magnetic forces are rather a tool to control heat transfer locally than to enhance the overall heat transfer of heat exchangers or the like. Magnetically caused disturbances decay due to viscous dissipation and the flow approaches the basic state again.

Exsiccation of suspension droplets generates characteristic ring-like stains. The homogeneity of such coffee rings is disturbed by subsequent cracking. Placing silica droplets on copper and stainless steel substrates, the ensuing drying and cracking chronology is investigated. The formation of the coffee ring and its cracking are visualised through microscopic imaging and videotaping. Based on the cracking chronology, three crack generations are identified. The evolution of the 1st crack generation is studied in detail. Two fracture types – logarithmic spiral and straight radially oriented – characterise these initial cracks. While the first type is due to deposition delamination, the straight cracks are induced by the interplay of capillary pressure and shear stress between coating and substrate. Most noteworthy is our finding that the cracking speed of the straight cracks is one order of magnitude larger than that of the spiral cracks. The pattern of the 1st generation cracks defines the final crack network. Our findings provide a comprehensive understanding of the crack pattern formation following the desiccation of silica droplets. This study offers details on nanofluid exsiccation on metal substrates, thereby opening routes for depositing nanoparticles on heated and non-heated surfaces for various engineering applications.

The sustainability of aquaculture has been debated intensely since 2000, when a review on the net contribution of aquaculture to world fish supplies was published in Nature. This paper reviews the developments in global aquaculture from 1997 to 2017, incorporating all industry sub-sectors and highlighting the integration of aquaculture in the global food system. Inland aquaculture—especially in Asia—has contributed the most to global production volumes and food security. Major gains have also occurred in aquaculture feed efficiency and fish nutrition, lowering the fish-in–fish-out ratio for all fed species, although the dependence on marine ingredients persists and reliance on terrestrial ingredients has increased. The culture of both molluscs and seaweed is increasingly recognized for its ecosystem services; however, the quantification, valuation, and market development of these services remain rare. The potential for molluscs and seaweed to support global nutritional security is underexploited. Management of pathogens, parasites, and pests remains a sustainability challenge industry-wide, and the effects of climate change on aquaculture remain uncertain and difficult to validate. Pressure on the aquaculture industry to embrace comprehensive sustainability measures during this 20-year period have improved the governance, technology, siting, and management in many cases. The volume of global aquaculture production has tripled since 2000 with positive trends in environmental performance, but the sector faces mounting challenges including pathogen management, pollution, climate change, and increasing dependence on land-based resource systems.

13 pages, 3 tables, 5 figures, The COVID-19 global pandemic has had severe, unpredictable and synchronous impacts on all levels of perishable food supply chains (PFSC), across multiple sectors and spatial scales. Aquaculture plays a vital and rapidly expanding role in food security, in some cases overtaking wild caught fisheries in the production of high-quality animal protein in this PFSC. We performed a rapid global assessment to evaluate the effects of the COVID-19 pandemic and related emerging control measures on the aquaculture supply chain. Socio-economic effects of the pandemic were analysed by surveying the perceptions of stakeholders, who were asked to describe potential supply-side disruption, vulnerabilities and resilience patterns along the production pipeline with four main supply chain components: a) hatchery, b) production/processing, c) distribution/logistics and d) market. We also assessed different farming strategies, comparing land- vs. sea-based systems; extensive vs. intensive methods; and with and without integrated multi-trophic aquaculture, IMTA. In addition to evaluating levels and sources of economic distress, interviewees were asked to identify mitigation solutions adopted at local / internal (i.e., farm-site) scales, and to express their preference on national / external scale mitigation measures among a set of a priori options. Survey responses identified the potential causes of disruption, ripple effects, sources of food insecurity, and socio-economic conflicts. They also pointed to various levels of mitigation strategies. The collated evidence represents a first baseline useful to address future disaster-driven responses, to reinforce the resilience of the sector and to facilitate the design reconstruction plans and mitigation measures, such as financial aid strategies, M.C.M.'s research activity was supported by the European Union's Horizon 2020 Research and Innovation programme under the Marie Skłodowska-Curie Action (Grant agreement no. 835589, MIRROR Project). People at the Laboratory of Ecology have been funded by the PRIN-MAHRES project (Ministry of Italian Research; MUR - 017MHHWBN_003 Linea C) and by the Interreg Italia-Malta HARMONY 2016 (Grant C1-3.1-31). C. Pita and A. Nogueira would like to thank FCT/MCTES for the financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020), through national funds. J.M.F. Babarro thanks project PID2019-106008RB-C21 for support through Spanish Government funds. The authors would like to thank also the ERASMUS+-FISHAQU project (No. 610071-EPP-1-2019-1-PT-EPPKA2-CBHE-JP)

International audience; Thermosyphons are heat transfer devices characterized by high efficiency due to simultaneous phase changes occurring in the evaporation-condensation cycle of working fluid. One of the most promising solutions to enhance their heat transfer capacity of the device is the use of nanofluids – suspensions of particles with at least one dimension below 100 nm. It was determined that nanofluid does not influence the work of thermosyphons condenser section and the focus should be put on the boiling process in the evaporator section. During boiling, nanoparticles tend to deposit on the heater’s surface, what alters characteristics of this surface and near surface hydrodynamics. This changes the appearance of nanofluid, but the precise effect on how the deposition of particles affects the properties of nanofluid is unknown. Changes in surface tension and wettability affect boiling regimes (e.g. reduced surface tension reduces the size of departing bubbles and inhibits geysering), and efficiency of heat transfer through the device. Understanding of those parameters is crucial for the development of appropriate models describing heat transfer in thermosyphon working with nanofluids. The main goal of this study is to determine surface tension and contact angle of nanofluids based on silica nanoparticles and nano-sized graphene oxide flakes before and after the experimental boiling cycle in the thermosyphon. Results show that, in comparison with water, silica nanofluid (2 vol.%) is characterized by lower surface tension and contact angles on both analysed surfaces. After-use silica nanofluid exhibited noticeably higher averaged surface tension and smaller contact angles in comparison to the fresh working medium. The change was most likely due to the decreased concentration caused by the deposition of nanoparticles during the thermosyphon operation. Still, the differences between before-use and after-use samples were smaller than the measurement uncertainties. Before-use graphene oxide nanofluid already showed surface tension and contact angle similar to water due to low concentration of graphene flakes (0.1 g/L). Consequently, the properties of after-use graphene oxide fluid were also not much different from water. Additional measurements of surface tension for graphene oxide nanofluid with and without addition of sodium dodecyl sulfate surfactant allowed to differentiate the effects caused by graphene flakes and surfactant. The surfactant reduced the surface tension of the nanofluid, but the change was smaller than in case of surfactant addition to pure water.

Solar radiation effects on the ecophysiology and biochemical responses of the brown macroalga Macrocystis pyrifera (L.) C. Agardh were evaluated using a mesocosm approach in Southern Chile. Treatments with different radiation attenuations were simulated with three vertical attenuation coefficients: (1) total (Kd = 0.8 m−1), (2) attenuated (Kd = 1.2 m−1), and (3) low (Kd = 1.6 m−1) radiation levels. Nutrient concentration and temperature did not show differences under the three light conditions. Photosynthetic activity was estimated by in vivo chlorophyll a (Chla) fluorescence under the three light treatments as an isolated physical factor in both in situ solar radiation in the field. This was achieved using a pulse amplitude-modulated (PAM) fluorometera—Diving PAM (in situ). Photosynthetic activity and biochemical composition were measured in winter during two daily cycles (1DC and 2DC) in different parts of the thalli of the plant: (1) canopy zone, (2) middle zone, and (3) down zone, associated with different depths in the mesocosm system. Nevertheless, the in situ electron transport rate (ETRin situ) was higher in the exposed thalli of the canopy zone, independent of the light treatment conditions. The concentration of phenolic compounds (PC) increases in the down zone in the first daily cycle, and it was higher in the middle zone in the second daily cycle. The Chla increased in the morning time under total and attenuated radiation in the first daily cycle. Solar radiation increasing at midday prompted the photoinhibition of photosynthesis in the canopy zone but also an increase in productivity and phenol content. Therefore, light attenuation in the water column drove key differences in the photo-physiological responses of M. pyrifera, with the highest productivity occurring in thalli positioned in the canopy zone when exposed to solar irradiance.

The sustainability of aquaculture has been debated intensely since 2000, when a review on the net contribution of aquaculture to world fish supplies was published in Nature. This paper reviews the developments in global aquaculture from 1997 to 2017, incorporating all industry sub-sectors and highlighting the integration of aquaculture in the global food system. Inland aquaculture-especially in Asia-has contributed the most to global production volumes and food security. Major gains have also occurred in aquaculture feed efficiency and fish nutrition, lowering the fish-in-fish-out ratio for all fed species, although the dependence on marine ingredients persists and reliance on terrestrial ingredients has increased. The culture of both molluscs and seaweed is increasingly recognized for its ecosystem services; however, the quantification, valuation, and market development of these services remain rare. The potential for molluscs and seaweed to support global nutritional security is underexploited. Management of pathogens, parasites, and pests remains a sustainability challenge industry-wide, and the effects of climate change on aquaculture remain uncertain and difficult to validate. Pressure on the aquaculture industry to embrace comprehensive sustainability measures during this 20-year period have improved the governance, technology, siting, and management in many cases.

International audience; This editorial note is dedicated to the 1st International Conference on Nanofluids (ICNf19), which was organized under the auspices of Nanouptake COST Action in June 2019, in Castelló (Spain). After a brief report about the conference issues, the successful selected contributions to this SpecialIssue of Energies about the ICNf19 are introduced.

The paper presents a thermal performance analysis of a thermosyphon filled with graphene oxide nanofluid. It focuses on factors influencing thermal resistance and geyser boiling processes, such as the presence of surfactant (here: sodium dodecyl sulphate), the time-related deterioration of nanoparticles, and working conditions. Results indicate that GO nanofluids improved heat transfer at low heat loads and that enhancements were limited to the evaporator section. Although thermal resistance of the device was similar for all tested working fluids at high evaporator temperatures, the time-dependent behaviour was different. Both water and GO nanofluid facilitated geyser boiling. Sodium dodecyl sulphate inhibited the phenomenon for pure water, but the same concentration of surfactant in the graphene oxide nanofluid did not show the same effect. SEM analysis showed that substantial amount of surfactant attached to the surface of graphene oxide flakes, which explains the previously described behaviour.

Wettability is the ability of the liquid to contact with the solid surface at the surrounding fluid and its degree is defined by contact angle (CA), which is calculated with balance between adhesive and cohesive forces on droplet surface. Thermophysical properties of the droplet, the forces acting on the droplet, atmosphere surrounding the droplet and the substrate surface are the main parameters a ecting on CA.With nanofluids (NF), nanoparticle concentration and size and shape can modify the contact angle and thus wettability. This study investigates the validity of single-phase CA correlations for several nanofluids with di erent types of nanoparticles dispersed in water. Geometrical parameters of sessile droplet (height of the droplet, wetting radius and radius of curvature at the apex) are used in the tested correlations, which are based on force balance acting on the droplet surface, energy balance, spherical dome approach and empirical expression, respectively. It is shown that single-phase models can be expressed in terms of Bond number, the non-dimensional droplet volume and two geometrical similarity simplexes. It is demonstrated that they can be used successfully to predict CA of dilute nanofluids’ at ambient conditions. Besides evaluation of CA, droplet shape is also well predicted for all nanofluid samples with 5% error.

Finfish aquaculture is an activity that has experienced an explosive global development, but presents several environmental risks, such as high nitrogen outputs with potential eutrophication consequences. Therefore, the integration of seaweed aquaculture with the aim of decreasing nitrogen emissions associated with intensive salmon farming has been proposed as a bioremediation solution. Ecophysiological knowledge about seaweeds cultured close to farming cages is, however, still rudimentary. We experimentally studied the growth and physiological responses of Macrocystis pyrifera (Linnaeus) C. Agardh in a suspended culture system near a commercial salmon farm at three culture depths in order to understand its productivity performance. The results showed maximum growth responses at intermediate depths (3 m) as opposed to near the surface (1 m) or at a deeper culture level (6 m). At 6 m depth, light limitations were detected, whereas the sporophytes growing at 1 m depth responded to high irradiances, especially in late spring and summer, where they were more intensely exposed to decay of photosynthesis than individuals from other depths. Accordingly, photosynthetic pigment concentrations (chlorophyll a and c, and fucoxonthin) were higher during low-light seasons (winter and early spring) but decreased during the summer. On the other hand, although both nitrogen uptake and Nitrate Reductase (NR) activity varied seasonally, increasing significantly in spring and summer, these variables were not affected by culture depth. Therefore, the optimal culture depth of M. pyrifera near salmon farms appears to be a physiological integration between nitrogen supply and demand, which is modulated by plant acclimation to the seasonal change in light and temperature. The results allow to discuss about the environmental constrains of M. pyrifera in an ecophysiological context to improve the understanding of its aquaculture, and to contribute relevant information on the use of this species in bioremediation.

International audience; The accelerated development of seaweed aquaculture is stimulating research on the genetic drivers of phenotypic diversity of the target species, in order to optimize breeding strategies, to help determine the choice of source populations, and for the selection of traits and varieties that fit with the environmental variability of the production site. This study investigates the spatial variation of the genetic and phenotypic diversities in natural populations of the giant kelp Macrocystis pyrifera, and evaluates the potential for modifying agronomic traits through controlled breeding. Nine microsatellites and 12 morphological traits were used to describe the distribution of diversity present along the Southeastern Pacific (SEP) Coast. We expected concordant patterns of spatial discontinuities if the genetic background was driving morphological divergence across habitats. Crossing experiments were made to assess the heritability of specific traits and evaluate the performance of the F1 generation in the laboratory and in open sea cultivation respectively. Our results revealed four genetic clusters along the latitudinal distribution of M. pyrifera populations, tightly correlated with the existence of major environmental discontinuities. These clusters also matched clusters of morphological diversity, suggesting that both morphological and genetic diversities responded to the same environmental drivers. In crossing experiments, no significant differences were detected between selfed and outbred F1, in morphology, growth and chemical components, but a high variability among all different crosses was observed, revealing a high degree of heritable phenotypic variance. Although, the results suggest that the morphological variation of Macrocystis along the SEP coast is strongly driven by the genetic background. Our controlled crosses were also indicative of a high potential for using this genetic variability in breeding programs for sustainable aquaculture development.

The interest in seaweeds by humans seems to have originated over 1700 years ago when several seaweed species became used in ethnic cuisines. These initial applications enabled the start of ...