Propagating waves of self-assembly in organosilane monolayers

Wavefronts associated with reaction-diffusion and self-assembly processes are ubiquitous in the natural world. For example, propagating fronts arise in crystallization and diverse other thermodynamic ordering processes, in polymerization fronts involved in cell movement and division, as well as in the competitive social interactions and population dynamics of animals at much larger scales. Although it is often claimed that self-sustaining or autocatalytic front propagation is well described by mean-field "reaction-diffusion" or "phase field" ordering models, it has recently become appreciated from simulations and theoretical arguments that fluctuation effects in lower spatial dimensions can lead to appreciable deviations from the classical mean-field theory (MFT) of this type of front propagation. The present work explores these fluctuation effects in a real physical system. In particular, we consider a high-resolution near-edge x-ray absorption fine structure spectroscopy (NEXAFS) study of the spontaneous frontal self-assembly of organosilane (OS) molecules into self-assembled monolayer (SAM) surface-energy gradients on oxidized silicon wafers. We find that these layers organize from the wafer edge as propagating wavefronts having well defined velocities. In accordance with two-dimensional simulations of this type of front propagation that take fluctuation effects into account, we find that the interfacial widths w(t) of these SAM self-assembly fronts exhibit a power-law broadening in time, w(t) approximately t(beta), rather than the constant width predicted by MFT. Moreover, the observed exponent values accord rather well with previous simulation and theoretical estimates. These observations have significant implications for diverse types of ordering fronts that occur under confinement conditions in biological or materials-processing contexts.     

Assessment of Explicit Representation of Dynamic Viral Processes in Regional Marine Ecological Models

Viruses, the most abundant microorganisms in the ocean, play important roles in marine ecosystems, mainly by killing their hosts and contributing to nutrient recycling. However, in models simulating ecosystems in real marine environments, the virus-mediated mortality (VMM) rates of their hosts are implicitly represented by constant parameters, thus ignoring the dynamics caused by interactions between viruses and hosts. Here, we construct a model explicitly representing marine viruses and the VMM rates of major hosts, heterotrophic bacteria, and apply it to two sites in the oligotrophic North Pacific and the more productive Arabian Sea. The impacts of the viral processes were assessed by comparing model results with the viral processes enabled and disabled. For reliable assessments, a data assimilation method was used to objectively optimize the model parameters in each run. The model generated spatiotemporally variable VMM rates, generally decreasing in the subsurface but increasing at the surface. Although the dynamics introduced by viruses could be partly stabilized by the ecosystems, they still caused substantial changes to the bacterial abundance, primary production and carbon export, with the changes greater at the more productive site. Our modeling experiments reveal the importance of explicitly simulating dynamic viral processes in marine ecological models.     

Phytoplankton species richness scales consistently from laboratory microcosms to the world's oceans

Species-area relationships have been observed for virtually all major groups of macroorganisms that have been studied to date but have not been explored for microscopic phytoplankton algae, which are the dominant producers in many freshwater and marine ecosystems. Our analyses of data from 142 different natural ponds, lakes, and oceans and 239 experimental ecosystems reveal a strong species-area relationship with an exponent that is invariant across ecosystems that span >15 orders of magnitude in spatial extent. A striking result is that the species-area relationship derived from small-scale experimental studies correctly scales up to natural aquatic ecosystems. These results significantly broaden our knowledge of the effects of island size on biodiversity and also confirm the relevance of experimentally derived data to the analysis and understanding of larger-scale ecological patterns. In addition, they confirm that patterns in microbial diversity are strongly consistent with those that have been repeatedly reported in the literature for macroorganisms.     

Iron conservation by reduction of metalloenzyme inventories in the marine diazotroph Crocosphaera watsonii

The marine nitrogen fixing microorganisms (diazotrophs) are a major source of nitrogen to open ocean ecosystems and are predicted to be limited by iron in most marine environments. Here we use global and targeted proteomic analyses on a key unicellular marine diazotroph Crocosphaera watsonii to reveal large scale diel changes in its proteome, including substantial variations in concentrations of iron metalloproteins involved in nitrogen fixation and photosynthesis, as well as nocturnal flavodoxin production. The daily synthesis and degradation of enzymes in coordination with their utilization results in a lowered cellular metalloenzyme inventory that requires ～40% less iron than if these enzymes were maintained throughout the diel cycle. This strategy is energetically expensive, but appears to serve as an important adaptation for confronting the iron scarcity of the open oceans. A global numerical model of ocean circulation, biogeochemistry and ecosystems suggests that Crocosphaera's ability to reduce its iron-metalloenzyme inventory provides two advantages: It allows Crocosphaera to inhabit regions lower in iron and allows the same iron supply to support higher Crocosphaera biomass and nitrogen fixation than if they did not have this reduced iron requirement.     

Functionally diverse reef-fish communities ameliorate coral disease

Coral reefs, the most diverse of marine ecosystems, currently experience unprecedented levels of degradation. Diseases are now recognized as a major cause of mortality in reef-forming corals and are complicit in phase shifts of reef ecosystems to algal-dominated states worldwide. Even so, factors contributing to disease occurrence, spread, and impact remain poorly understood. Ecosystem resilience has been linked to the conservation of functional diversity, whereas overfishing reduces functional diversity through cascading, top-down effects. Hence, we tested the hypothesis that reefs with trophically diverse reef fish communities have less coral disease than overfished reefs. We surveyed reefs across the central Philippines, including well-managed marine protected areas (MPAs), and found that disease prevalence was significantly negatively correlated with fish taxonomic diversity. Further, MPAs had significantly higher fish diversity and less disease than unprotected areas. We subsequently investigated potential links between coral disease and the trophic components of fish diversity, finding that only the density of coral-feeding chaetodontid butterflyfishes, seldom targeted by fishers, was positively associated with disease prevalence. These previously uncharacterized results are supported by a second large-scale dataset from the Great Barrier Reef. We hypothesize that members of the charismatic reef-fish family Chaetodontidae are major vectors of coral disease by virtue of their trophic specialization on hard corals and their ecological release in overfished areas, particularly outside MPAs.     

Introduced rats indirectly change marine rocky intertidal communities from algae- to invertebrate-dominated

It is widely recognized that trophic interactions structure ecological communities, but their effects are usually only demonstrated on a small scale. As a result, landscape-level documentations of trophic cascades that alter entire communities are scarce. Islands invaded by animals provide natural experiment opportunities both to measure general trophic effects across large spatial scales and to determine the trophic roles of invasive species within native ecosystems. Studies addressing the trophic interactions of invasive species most often focus on their direct effects. To investigate both the presence of a landscape-level trophic cascade and the direct and indirect effects of an invasive species, we examined the impacts of Norway rats (Rattus norvegicus) introduced to the Aleutian Islands on marine bird densities and marine rocky intertidal community structures through surveys conducted on invaded and rat-free islands throughout the entire 1,900-km archipelago. Densities of birds that forage in the intertidal were higher on islands without rats. Marine intertidal invertebrates were more abundant on islands with rats, whereas fleshy algal cover was reduced. Our results demonstrate that invasive rats directly reduce bird densities through predation and significantly affect invertebrate and marine algal abundance in the rocky intertidal indirectly via a cross-community trophic cascade, unexpectedly changing the intertidal community structure from an algae- to an invertebrate-dominated system.     

Marine biodiversity,ecosystem functioning,and carbon cycles

Although recent studies suggest that climate change may substantially accelerate the rate of species loss in the biosphere, only a few studies have focused on the potential consequences of a spatial reorganization of biodiversity with global warming. Here, we show a pronounced latitudinal increase in phytoplanktonic and zooplanktonic biodiversity in the extratropical North Atlantic Ocean in recent decades. We also show that this rise in biodiversity paralleled a decrease in the mean size of zooplanktonic copepods and that the reorganization of the planktonic ecosystem toward dominance by smaller organisms may influence the networks in which carbon flows, with negative effects on the downward biological carbon pump and demersal Atlantic cod (Gadus morhua). Our study suggests that, contrary to the usual interpretation of increasing biodiversity being a positive emergent property promoting the stability/resilience of ecosystems, the parallel decrease in sizes of planktonic organisms could be viewed in the North Atlantic as reducing some of the services provided by marine ecosystems to humans.     

Dose-dependent regulation of microbial activity on sinking particles by polyunsaturated aldehydes: Implications for the carbon cycle

Diatoms and other phytoplankton play a crucial role in the global carbon cycle, fixing CO₂ into organic carbon, which may then be exported to depth via sinking particles. The molecular diversity of this organic carbon is vast and many highly bioactive molecules have been identified. Polyunsaturated aldehydes (PUAs) are bioactive on various levels of the marine food web, and yet the potential for these molecules to affect the fate of organic carbon produced by diatoms remains an open question. In this study, the effects of PUAs on the natural microbial assemblages associated with sinking particles were investigated. Sinking particles were collected from 150 m in the water column and exposed to varying concentrations of PUAs in dark incubations over 24 h. PUA doses ranging from 1 to 10 µM stimulated respiration, organic matter hydrolysis, and cell growth by bacteria associated with sinking particles. PUA dosages near 100 µM appeared to be toxic, resulting in decreased bacterial cell abundance and metabolism, as well as pronounced shifts in bacterial community composition. Sinking particles were hot spots for PUA production that contained concentrations within the stimulatory micromolar range in contrast to previously reported picomolar concentrations of these compounds in bulk seawater. This suggests PUAs produced in situ stimulate the remineralization of phytoplankton-derived sinking organic matter, decreasing carbon export efficiency, and shoaling the average depths of nutrient regeneration. Our results are consistent with a “bioactivity hypothesis” for explaining variations in carbon export efficiency in the oceans.Planktonic microbes in the world’s oceans play a major role in the global carbon cycle. Through photosynthesis, phytoplankton convert carbon dioxide into particulate organic carbon (POC), which then has the potential to sink to the deep sea. This process is opposed by zooplankton and heterotrophic bacteria, which, as agents of respiration, degrade organic matter and convert it back into carbon dioxide. In addition to respiring POC, heterotrophic bacteria that are associated with sinking POC use membrane-bound ectohydrolytic enzymes that affect the disaggregation of POC into smaller nonsinking particles and dissolved organic carbon (DOC) (1). Despite the long-recognized role of particle-associated bacteria (2), the relationships between the activities of these bacteria, particle properties, and the time and depth scales of sinking POC degradation, disaggregation, and respiration remain poorly constrained. Although the molecular-level composition of sinking POC has been used to identify its phytoplanktonic sources and to constrain the timescales of its degradation by heterotrophic bacteria (3–5), none of these studies has accounted for the potential impacts of bioactive molecules within sinking POC on the activities of particle-associated bacteria.Diatoms are key members of the phytoplanktonic communities across the world’s ocean and are known to produce a large diversity of organic molecules, including many that are bioactive. Polyunsaturated aldehydes (PUAs) have received particular interest. The stage for discovery of these molecules was set in the 1990s, when a group of researchers advanced the “paradox of diatom-copepod interactions”—the observation that copepods, which prey on diatoms, exhibited decreased reproductive success when exclusively fed diatoms (6–8). Miralto et al. (9) later purified PUAs from diatom cultures and observed arrested embryogenesis of copepod eggs that were exposed to these compounds. PUA production is now a well-characterized stress surveillance response to wounding during grazing and to nutrient depletion, both of which are bloom termination mechanisms (10, 11).It has been proposed that PUAs also mediate phytoplankton bloom dynamics by impacting other members of the marine planktonic community, aside from zooplankton. In culture conditions, many eukaryotic phytoplankton experience a decrease in growth rate when exposed to PUAs (12, 13). Isolated bacterial strains demonstrate a varied response to PUAs, whereby diatom-associated isolates are generally unaffected, whereas other strains exhibit either dose-dependent decreases or increases in growth rate in response to PUAs (14). Although many culture studies have been conducted on zooplankton, phytoplankton, and bacterial isolates—all important players in the microbial loop—there have been few attempts to study the impact of PUAs on these trophic levels in natural marine ecosystems under in situ condition (15, 16). Surveys of water column concentrations of PUAs suggest that concentrations are generally much lower than levels required to elicit responses in phytoplankton, zooplankton, or bacteria (17, 18). Consequently, the impact of PUAs on the marine carbon cycle remains an open question.     

Sensitivities of marine carbon fluxes to ocean change

Throughout Earth''s history, the oceans have played a dominant role in the climate system through the storage and transport of heat and the exchange of water and climate-relevant gases with the atmosphere. The ocean''s heat capacity is ≈1,000 times larger than that of the atmosphere, its content of reactive carbon more than 60 times larger. Through a variety of physical, chemical, and biological processes, the ocean acts as a driver of climate variability on time scales ranging from seasonal to interannual to decadal to glacial–interglacial. The same processes will also be involved in future responses of the ocean to global change. Here we assess the responses of the seawater carbonate system and of the ocean''s physical and biological carbon pumps to (i) ocean warming and the associated changes in vertical mixing and overturning circulation, and (ii) ocean acidification and carbonation. Our analysis underscores that many of these responses have the potential for significant feedback to the climate system. Because several of the underlying processes are interlinked and nonlinear, the sign and magnitude of the ocean''s carbon cycle feedback to climate change is yet unknown. Understanding these processes and their sensitivities to global change will be crucial to our ability to project future climate change.     

Fish as major carbonate mud producers and missing components of the tropical carbonate factory

Carbonate mud is a major constituent of recent marine carbonate sediments and of ancient limestones, which contain unique records of changes in ocean chemistry and climate shifts in the geological past. However, the origin of carbonate mud is controversial and often problematic to resolve. Here we show that tropical marine fish produce and excrete various forms of precipitated (nonskeletal) calcium carbonate from their guts ("low" and "high" Mg-calcite and aragonite), but that very fine-grained (mostly < 2 μm) high Mg-calcite crystallites (i.e., > 4 mole % MgCO(3)) are their dominant excretory product. Crystallites from fish are morphologically diverse and species-specific, but all are unique relative to previously known biogenic and abiotic sources of carbonate within open marine systems. Using site specific fish biomass and carbonate excretion rate data we estimate that fish produce ～6.1 × 10(6) kg CaCO(3)/year across the Bahamian archipelago, all as mud-grade (the < 63 μm fraction) carbonate and thus as a potential sediment constituent. Estimated contributions from fish to total carbonate mud production average ～14% overall, and exceed 70% in specific habitats. Critically, we also document the widespread presence of these distinctive fish-derived carbonates in the finest sediment fractions from all habitat types in the Bahamas, demonstrating that these carbonates have direct relevance to contemporary carbonate sediment budgets. Fish thus represent a hitherto unrecognized but significant source of fine-grained carbonate sediment, the discovery of which has direct application to the conceptual ideas of how marine carbonate factories function both today and in the past.     

The influence of oceanographic fronts and early-life-history traits on connectivity among littoral fish species

The spatial distribution of neutral genetic diversity is mainly influenced by barriers to dispersal. The nature of such barriers varies according to the dispersal means and capabilities of the organisms concerned. Although these barriers are often obvious on land, in the ocean they can be more difficult to identify. Determining the relative influence of physical and biotic factors on genetic connectivity remains a major challenge for marine ecologists. Here, we compare gene flow patterns of 7 littoral fish species from 6 families with a range of early-life-history traits sampled at the same geographic locations across common environmental discontinuities in the form of oceanic fronts in the Western Mediterranean. We show that these fronts represent major barriers to gene flow and have a strong influence on the population genetic structure of some fish species. We also found no significant relation between the early-life-history traits most commonly investigated (egg type, pelagic larval duration, and inshore-offshore spawning) and gene flow patterns, suggesting that other life-history factors should deserve attention. The fronts analyzed and the underlying physical mechanisms are not site-specific but common among the oceans, suggesting the generality of our findings.     

Top marine predators track Lagrangian coherent structures

Meso- and submesoscales (fronts, eddies, filaments) in surface ocean flow have a crucial influence on marine ecosystems. Their dynamics partly control the foraging behavior and the displacement of marine top predators (tuna, birds, turtles, and cetaceans). In this work we focus on the role of submesoscale structures in the Mozambique Channel in the distribution of a marine predator, the Great Frigatebird. Using a newly developed dynamic concept, the finite-size Lyapunov exponent (FSLE), we identified Lagrangian coherent structures (LCSs) present in the surface flow in the channel over a 2-month observation period (August and September 2003). By comparing seabird satellite positions with LCS locations, we demonstrate that frigatebirds track precisely these structures in the Mozambique Channel, providing the first evidence that a top predator is able to track these FSLE ridges to locate food patches. After comparing bird positions during long and short trips and different parts of these trips, we propose several hypotheses to understand how frigatebirds can follow these LCSs. The birds might use visual and/or olfactory cues and/or atmospheric current changes over the structures to move along these biologic corridors. The birds being often associated with tuna schools around foraging areas, a thorough comprehension of their foraging behavior and movement during the breeding season is crucial not only to seabird ecology but also to an appropriate ecosystemic approach to fisheries in the channel.     

Evolving science of marine reserves: new developments and emerging research frontiers

The field of marine reserve science has matured greatly over the last decade, moving beyond studies of single reserves and beyond perspectives from single disciplines. This Special Feature exemplifies recent advances in marine reserve research, showing insights gained from synthetic studies of reserve networks, long-term changes within reserves, integration of social and ecological science research, and balance between reserve design for conservation as well as fishery and other commercial objectives. This rich body of research helps to inform conservation planning for marine ecosystems but also poses new challenges for further study, including how to best design integrated fisheries management and conservation systems, how to effectively evaluate the performance of entire reserve networks, and how to examine the complex coupling between ecological and socioeconomic responses to reserve networks.     

Rapid chemotactic response enables marine bacteria to exploit ephemeral microscale nutrient patches

Because ocean water is typically resource-poor, bacteria may gain significant growth advantages if they can exploit the ephemeral nutrient patches originating from numerous, small sources. Although this interaction has been proposed to enhance biogeochemical transformation rates in the ocean, it remains questionable whether bacteria are able to efficiently use patches before physical mechanisms dissipate them. Here we show that the rapid chemotactic response of the marine bacterium Pseudoalteromonas haloplanktis substantially enhances its ability to exploit nutrient patches before they dissipate. We investigated two types of patches important in the ocean: nutrient pulses and nutrient plumes, generated for example from lysed algae and sinking organic particles, respectively. We used microfluidic devices to create patches with environmentally realistic dimensions and dynamics. The accumulation of P. haloplanktis in response to a nutrient pulse led to formation of bacterial hot spots within tens of seconds, resulting in a 10-fold higher nutrient exposure for the fastest 20% of the population compared with nonmotile cells. Moreover, the chemotactic response of P. haloplanktis was >10 times faster than the classic chemotaxis model Escherichia coli, leading to twice the nutrient exposure. We demonstrate that such rapid response allows P. haloplanktis to colonize nutrient plumes for realistic particle sinking speeds, with up to a 4-fold nutrient exposure compared with nonmotile cells. These results suggest that chemotactic swimming strategies of marine bacteria in patchy nutrient seascapes exert strong influence on carbon turnover rates by triggering the formation of microscale hot spots of bacterial productivity.     

Design and Evaluation of an Ultrahigh-Strength Coral Aggregate Concrete for Maritime and Reef Engineering

In this paper, an ultrahigh-strength marine concrete containing coral aggregates is developed. Concrete fabricated from marine sources is considered an effective and economical alternative for marine engineering and the construction of remote islands. To protect sea coral ecosystems, the coral aggregates used for construction are only efflorescent coral debris. To achieve the expected mechanical performance from the studied concrete, an optimal mixture design is conducted to determine the optimal proportions of components, in order to optimize the compressive strength. The mechanical properties and the autogenous shrinkage, as well as the heat flow of early hydration reactions, are measured. The hydration products fill up the pores of coral aggregates, endowing our concrete with flowability and self-compacting ability. The phases in the marine concrete are identified via X-ray diffraction analysis. The 28-day compressive and flexural strength of the developed marine concrete achieve 116.76 MPa and 18.24 MPa, respectively. On account of the lower cement content and the internal curing provided by coral aggregates, the volume change resulting from autogenous shrinkage is only 63.11% of that of ordinary reactive powder concrete.     

Multiyear predictability of tropical marine productivity

With the emergence of decadal predictability simulations, research toward forecasting variations of the climate system now covers a large range of timescales. However, assessment of the capacity to predict natural variations of relevant biogeochemical variables like carbon fluxes, pH, or marine primary productivity remains unexplored. Among these, the net primary productivity (NPP) is of particular relevance in a forecasting perspective. Indeed, in regions like the tropical Pacific (30°N–30°S), NPP exhibits natural fluctuations at interannual to decadal timescales that have large impacts on marine ecosystems and fisheries. Here, we investigate predictions of NPP variations over the last decades (i.e., from 1997 to 2011) with an Earth system model within the tropical Pacific. Results suggest a predictive skill for NPP of 3 y, which is higher than that of sea surface temperature (1 y). We attribute the higher predictability of NPP to the poleward advection of nutrient anomalies (nitrate and iron), which sustain fluctuations in phytoplankton productivity over several years. These results open previously unidentified perspectives to the development of science-based management approaches to marine resources relying on integrated physical-biogeochemical forecasting systems.In 2010, global fisheries supplied the world with ∼148 million tons of fish with a total value of 217.5 billion US dollars (1). Fisheries represent a strong anthropogenic pressure on marine ecosystems and an increasing fraction of commercially exploited fish stocks are on the verge of collapse (1). However, in some oceanic regions like the tropical Pacific, which hosts the largest world fisheries (1), the decline of fish stocks cannot be attributed solely to overfishing. It is suspected to result from the interplay between human foraging and regional natural fluctuations in food abundance at the base of the food web such as variations in net primary productivity (NPP) occurring at interannual-to-decadal timescales. These natural fluctuations impact marine ecosystems across large oceanic regions (2). In the tropical Pacific, these fluctuations are suggested to be driven by large-scale climate variations such as the Madden Julian Oscillation (3), the El Niño Southern Oscillation (4), or the Pacific Decadal Oscillation (5). These climate modes are potentially predictable between one and up to several years (6, 7). However, although past studies have investigated the predictive skill of physical variables such as sea surface temperature (SST) (8) or precipitation (9) in the tropical Pacific, none has explored the potential predictability of natural variations of biogeochemical variables like NPP. This is all of the more surprising as the ability to predict natural variations of NPP at interannual-to-decadal timescales may be of key relevance to fisheries management (10–12).     

In Vitro Wound Dressing Stack Model as a First Step to Evaluate the Behavior of Dressing Materials in Wound Bed—An Assessment of Mass Transport Phenomena in Hydrogel Wound Dressings

Wound dressings when applied are in contact with wound exudates in vivo or with acceptor fluid when testing drug release from wound dressing in vitro. Therefore, the assessment of bidirectional mass transport phenomena in dressing after application on the substrate is important but has never been addressed in this context. For this reason, an in vitro wound dressing stack model was developed and implemented in the 3D printed holder. The stack was imaged using magnetic resonance imaging, i.e., relaxometric imaging was performed by means of T₂ relaxation time and signal amplitude 1D profiles across the wound stack. As a substrate, fetal bovine serum or propylene glycol were used to simulate in vivo or in vitro cases. Multi-exponential analysis of the spatially resolved magnetic resonance signal enabled to distinguish components originating from water and propylene glycol in various environments. The spatiotemporal evolution of these components was assessed. The components were related to mass transport (water, propylene glycol) in the dressing/substrate system and subsequent changes of physicochemical properties of the dressing and adjacent substrate. Sharp changes in spatial profiles were detected and identified as moving fronts. It can be concluded that: (1) An attempt to assess mass transport phenomena was carried out revealing the spatial structure of the wound dressing in terms of moving fronts and corresponding layers; (2) Moving fronts, layers and their temporal evolution originated from bidirectional mass transport between wound dressing and substrate. The setup can be further applied to dressings containing drugs.     

Isolation and Characterization of the First Temperate Virus Infecting Psychrobacillus from Marine Sediments

Viruses are far more abundant than cellular microorganisms in the marine ecosystem. However, very few viruses have so far been isolated from marine sediments, especially hydrothermal vent sediments, hindering the understanding of the biology and ecological functions of these tiny organisms. Here, we report the isolation and characterization of a temperate bacteriophage, named PVJ1, which infects Psychrobacillus from a hydrothermal vent field in Okinawa Trough. PVJ1 belongs to the Myoviridae family of the order Caudovirales. The tailed phage possesses a 53,187 bp linear dsDNA genome, with 84 ORFs encoding structural proteins, genome replication, host lysis, etc. in a modular pattern. The phage genome is integrated into the host chromosome near the 3′-end of deoD, a gene encoding purine nucleoside phosphorylase (PNP). The phage integration does not appear to disrupt the function of PNP. The phage DNA is packaged by the headful mechanism. Release of PVJ1 from the host cell was drastically enhanced by treatment with mitomycin C. Phages encoding an MCP sharing significant similarity (≥70% identical amino acids) with that of PVJ1 are widespread in diverse environments, including marine and freshwater sediments, soils, artificial ecosystems, and animal intestines, and primarily infect Firmicutes. These results are valuable to the understanding of the lifestyle and host interactions of bacterial viruses at the bottom of the ocean.     

Gel Evolution of Copper Tailing-Based Green Geopolymers in Marine Related Environments

Geopolymers have attracted extensive attention in the marine environment because of its special reticulate nanostructure. Gel evolutions of copper tailing-based green geopolymers were studied under air, deionized water, seawater, freeze–thaw cycle and carbonization environments. Their mechanical properties and microstructures were characterized by compressive strength measurement, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). It was found that the deionized water and natural marine water exposure promoted the evolution degree of geopolymers and improved their compressive strength, while exposure to the carbonization environment weakened the gel evolution and decreased the cross-linking degree of the Sodium aluminosilicate hydrate (N-A-S-H)gel structure, resulting in a decline of compressive strength. The geopolymer exposed in the freeze–thaw cycle exhibited the worst deterioration due to the expansion caused by the crystallization in the geopolymer. These results are essential and beneficial to further understanding the gel formation process in various marine environments and could promote the investigation of green concrete.