Heterogeneous Substrates Research Articles

Study on the Heterogeneous Nucleation Mechanism of SiCp/AZ91 Magnesium Matrix Composites under Pulse Current

SiCp/AZ91D magnesium matrix composites with 30% SiCp were successfully prepared by pulsed current melting in this work. Then, the influences of the pulse current on the microstructure, phase composition, and heterogeneous nucleation of the experimental materials were analyzed in detail. The results show that the grain size of both the solidification matrix structure and SiC reinforcement are refined by pulse current treatment, and the refining effect is gradually more obvious with an increase in the pulse current peak value. Moreover, the pulse current reduces the chemical potential of the reaction between SiCp and Mg matrix, thus promoting the reaction between SiCp and the alloy melt and stimulating the formation of Al4C3 along the grain boundaries. Furthermore, Al4C3 and MgO, as heterogeneous nucleation substrates, can induce heterogeneous nucleation and refine the solidification matrix structure. Finally, when increasing the peak value of the pulse current, the repulsive force between the particles increases while the agglomeration phenomenon is suppressed, which results in the dispersed distribution of SiC reinforcements.

Leaky-wave radiating surface on heterogeneous high-κ material for monolithic antenna-frontend integration

In a highly integrated analog radio-over-fiber transceiver, seamless integration of the antenna-frontend is crucial as an antenna is generally implemented on a high-κ material, which is set to highly degrade the antenna's performance. This work is concerned with the radiation behavior improvement of a planar leaky-wave antenna with an inductive partially reflecting surface (PRS) on a high-κ substrate for the development of a highly directive antenna. To begin with, we show how a thin and single-mode resonance (SMR) inductive PRS on high-κ materials in a planar leaky-wave antenna is set to provoke two resonance frequencies (i.e., PRS and cavity resonances) to converge, thereby diminishing the antenna's broadside directivity. By applying an equivalent circuit model, we explain how a multi-mode resonance (MMR) PRS can adequately be applied to address the underlying challenges. Subsequently, the leaky-wave radiation behavior of an antenna with a heterogeneous substrate is investigated and analytical equations are derived and verified with a full-wave simulation. The effects of material permittivity and thickness in a heterogeneous-cavity antenna on leaky-wave performance are investigated using these approximate yet accurate-enough equations. To justify the findings, two 9 × 9 planar leaky-wave antennas are prototyped on heterogeneous substrates based on SMR and MMR PRS and the radiation performances are compared. Our investigations reveal that in the proposed scenario, an MMR PRS can significantly enhance the antenna's broadside directivity by over 4 dBi at the resonance frequency (27.5 GHz), which is also set to improve radiation pattern compared to a SMR-based antenna. Finally, a single-fed dual-band aperture-shared antenna with a large frequency ratio (S-band and Ka-band) is developed and fabricated on a high-κ substrate based on the proposed MMR PRS.

As good as human experts in detecting plant roots in minirhizotron images but efficient and reproducible: the convolutional neural network “RootDetector”

Plant roots influence many ecological and biogeochemical processes, such as carbon, water and nutrient cycling. Because of difficult accessibility, knowledge on plant root growth dynamics in field conditions, however, is fragmentary at best. Minirhizotrons, i.e. transparent tubes placed in the substrate into which specialized cameras or circular scanners are inserted, facilitate the capture of high-resolution images of root dynamics at the soil-tube interface with little to no disturbance after the initial installation. Their use, especially in field studies with multiple species and heterogeneous substrates, though, is limited by the amount of work that subsequent manual tracing of roots in the images requires. Furthermore, the reproducibility and objectivity of manual root detection is questionable. Here, we use a Convolutional Neural Network (CNN) for the automatic detection of roots in minirhizotron images and compare the performance of our RootDetector with human analysts with different levels of expertise. Our minirhizotron data come from various wetlands on organic soils, i.e. highly heterogeneous substrates consisting of dead plant material, often times mainly roots, in various degrees of decomposition. This may be seen as one of the most challenging soil types for root segmentation in minirhizotron images. RootDetector showed a high capability to correctly segment root pixels in minirhizotron images from field observations (F1 = 0.6044; r2 compared to a human expert = 0.99). Reproducibility among humans, however, depended strongly on expertise level, with novices showing drastic variation among individual analysts and annotating on average more than 13-times higher root length/cm2 per image compared to expert analysts. CNNs such as RootDetector provide a reliable and efficient method for the detection of roots and root length in minirhizotron images even from challenging field conditions. Analyses with RootDetector thus save resources, are reproducible and objective, and are as accurate as manual analyses performed by human experts.

Functional Diversity of Vibrational Signaling Systems in Insects.

Communication by substrate-borne mechanical waves is widespread in insects. The specifics of vibrational communication are related to heterogeneous natural substrates that strongly influence signal transmission. Insects generate vibrational signals primarily by tremulation, drumming, stridulation, and tymbalation, most commonly during sexual behavior but also in agonistic, social, and mutualistic as well as defense interactions and as part of foraging strategies. Vibration signals are often part of multimodal communication. Sensilla and organs detecting substrate vibration show great diversity and primarily occur in insect legs to optimize sensitivity and directionality. In the natural environment, signals from heterospecifics, as well as social and enemy interactions within vibrational communication networks, influence signaling and behavioral strategies. The exploitation of substrate-borne vibrational signaling offers a promising application for behavioral manipulation in pest control. Expected final online publication date for the Annual Review of Entomology, Volume 68 is January 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Effect of Trace Amount Modified SiC Nanoparticles on Microstructures and Mechanical Properties of ZA27 Alloy

In order to modify the microstructure and enhance the mechanical properties, the influence of trace amount modified SiC nanoparticles on the as‐cast ZA27alloy is investigated. The results indicate that the original coarse and developed dendrites are refined gradually and turn into fine and uniform equiaxed crystals and spherical structures. The primary α(Al) phases, eutectoid(α + η) phases, and ε(CuZn4) phases are also refined. The planar disregistry calculations between 6H‐SiC and α(Al) show that 6H‐SiC is an effective heterogeneous nucleus substrate for α(Al). The refined mechanism of modified SiC nanoparticles on ZA27 alloy is also discussed. When the addition is 0.5%, the tensile strength is increased by 6.5% and elongation is increased by 12.7%. The yield strength of SiC nanoparticles reinforced ZA27 is discussed quantitatively to reveal the strengthening mechanisms.

The influence of subsurface architecture on scour hole formation in the Rhine–Meuse delta, the Netherlands

Abstract Scour holes are common features in deltaic rivers which can destabilise embankments through oversteepening of the river bed. Their development has been studied extensively from the hydraulic perspective, but another important control is the erodibility of the river bed which varies considerably due to thickening of heterogeneous deltaic substrate towards the coast. Therefore, we assessed the influence of delta-scale geological heterogeneity and local subsurface architecture on scour hole formation in addition to the hydrodynamic controls. We (1) created an inventory of 165 scour hole locations in the Rhine–Meuse delta, (2) assessed the hydrodynamic conditions at the locations, (3) extracted geometric characteristics and (4) determined the subsurface architecture from geological data. Central and lower delta branches have 0.6–0.7 scours per km while upper delta branches have less than 0.2. Downstream, 58% of scour holes were related to architectural elements, notably sand bodies from former Holocene channel belts and Early Holocene cohesive beds. These scours have steeper slopes due to higher proportions of cohesive sediments near the river bed. Furthermore, scours related to channel belt sand bodies are limited in downstream length and depth, up to maximum of approximately two times the water depth. From our results, we provide a delta-scale explanatory framework that relates the position of present-day river channels with respect to Pleistocene river deposits and Holocene fluvio-deltaic deposits to scour hole formation. Upstream rivers are incised in Pleistocene deposits showing less local variation in erodibility. The majority of scour holes here relate to engineering works. In central and lower delta branches, geologically inherited heterogeneity of the Holocene substrate at critical depths near the channel bottom adds to anthropogenic induced scours and results in high abundances. This demonstrates that downstream variation in subsurface architecture should be considered as a key control on scour locations and characteristics for management purposes.

Root foraging in the leguminous zinc hyperaccumulator Crotalaria novae-hollandiae from Queensland, Australia

Context Root foraging by hyperaccumulator plants in response to patchily distributed metals has been observed in several obligate hyperaccumulators, but it is not known whether facultative hyperaccumulators respond similarly. Aims This study investigated the root-growth behaviour in the leguminous zinc (Zn) hyperaccumulator Crotalaria novae-hollandiae compared with the non-accumulating Crotalaria cunninghamii in response to localised soil Zn enrichment in the soil to observe foraging versus avoidance responses. Methods We conducted rhizotron experiments in which we exposed the Crotalaria species pair to juxtaposed treatments, which were either homogenous (each half of the treatments containing same Zn concentrations) or heterogenous (different Zn concentrations in each half of the treatments). The Zn concentrations were 0 μg Zn g−1 (control), 2000 μg Zn g−1 and 5000 μg Zn g−1 in the form of zinc carbonate). Key results We found that none of the treatments had significantly different rooting density and root biomass, regardless of the Crotalaria species. This finding contrasts with increased root proliferation in Zn-rich patches found for other obligate hyperaccumulator species. Conclusions and implications The no-preference root response towards Zn in Crotalaria may partly explain the facultative hyperaccumulation mechanism displayed by these species. This root response towards Zn may ultimately affect Zn phytoextraction efficacy when utilising Crotalaria species in a heterogenous Zn soil substrate. These findings highlight the need for rhizosphere investigations prior to field phytoextraction applications.

Design of a Circularly Polarized High-Gain Patch Antenna Using a Higher-Order Mode With a Heterogeneous Substrate Layer for GPS Applications

Design of a Circularly Polarized High-Gain Patch Antenna Using a Higher-Order Mode With a Heterogeneous Substrate Layer for GPS Applications

On the study of some geological structure models

In this work, we study problems of harmonic vibrations of extended elastic structures with a coating. The studied boundary value problems can have different physical interpretations; in this case, they are considered as models of geological structures. We used two different coating models. The equation of a bending plate was chosen to describe one of them. The second type of coating is not a traditionally studied stringer or overlay, since it is characterized by several parameters of a two-dimensional deformable object. Further we have conducted a study of the properties for the substrate/coating system. Where numerical analysis showed us that the difference between the zero and pole curves for an elastic medium with a coating from the dispersion curves for an elastic medium without a coating is stronger the greater the thickness of the coating plate and the denser its material. The conclusions are valid for both plate models used. The models of lithospheric structures considered in this work make it possible to study the features of wave propagation in a three-dimensional deformable foundation with a two-dimensional coating, not only for continuous coatings, but also in the presence of vertical defects in them, as well as heterogeneous composite coatings. The presented approach can be extended to problems for heterogeneous substrates.

Microstructure-driven electrical conductivity optimization in additively manufactured microscale copper interconnects.

As the microelectronics field pushes to increase device density through downscaling component dimensions, various novel micro- and nano-scale additive manufacturing technologies have emerged to expand the small scale design space. These techniques offer unprecedented freedom in designing 3D circuitry but have not yet delivered device-grade materials. To highlight the complex role of processing on the quality and microstructure of AM metals, we report the electrical properties of micrometer-scale copper interconnects fabricated by Fluid Force Microscopy (FluidFM) and Electrohydrodynamic-Redox Printing (EHD-RP). Using a thin film-based 4-terminal testing chip developed for the scope of this study, the electrical resistance of as-printed metals is directly related to print strategies and the specific morphological and microstructural features. Notably, the chip requires direct synthesis of conductive structures on an insulating substrate, which is shown for the first time in the case of FluidFM. Finally, we demonstrate the unique ability of EHD-RP to tune the materials resistivity by one order of magnitude solely through printing voltage. Through its novel electrical characterization approach, this study offers unique insight into the electrical properties of micro- and submicrometer-sized copper interconnects and steps towards a deeper understanding of micro AM metal properties for advanced electronics applications.

Heterogeneous integration of lithium tantalate thin film on quartz for high performance surface acoustic wave resonator

Surface acoustic wave (SAW) resonator based on the piezo film on a foreign substrate is promising to enhance the performance of radio frequency filters. In this work, the 4 inch wafer-scale lithium tantalate thin film on quartz (LTOQ) heterogenous substrate was fabricated by ion-cut process. The cut angle of quartz was optimized to achieve high-quality factor (Q) based on finite element analysis. The average film thickness and the film nonuniformity for the whole wafer are 602 nm and ±2.2%, respectively. The lithium tantalate film exhibits single-crystalline quality where the full width at half-maximum of high-resolution X-ray diffraction rocking curve is 47.4 arcsec. The shear horizonal surface acoustic wave resonator based on the LTOQ structure exhibits a maximum Bode-Q exceeding 3000 and the electromechanical coupling coefficient of 10.26%. The temperature coefficient of frequency at resonant frequency and anti-resonant frequency are −25.21 ppm °C−1 and −35.22 ppm °C−1, respectively.

Effect of the Surface Activation Parameter on the Fabrication Process of 4H–SiC Film on SiO2/Si Using the Crystal‐Ion‐Slicing Technique

4H–silicon carbide on silicon (4H–SiC on Si) fabricated by crystal‐ion‐slicing (CIS) technology can be served as an integration platform for optoelectronic devices and composite substrate for gallium nitride heteroepitaxy. The bonding strength of 4H–SiC on Si is closely related to the surface activation parameter, which finally impacts the fabrication process. Herein, 1.2 μm thick 4H–SiC single crystal film has been successfully transferred onto Si substrate by CIS technology. The mechanism of bonding strength enhanced by plasma activation is studied, and the effect of bonding strength on the exfoliating process of film is analyzed. High bonding strength obtained under the O2 90 s activation condition makes the film have a more compact interface, and the characterizations of morphology and structure confirm the smooth surface and single crystal quality. These results provide a possibility for optoelectronic integration and growth of gallium nitride on the heterogeneous substrate.

Mechanism of cyclic β-glucan export by ABC transporter Cgt of Brucella.

Polysaccharides play critical roles in bacteria, including the formation of protective capsules and biofilms and establishing specific host cell interactions. Their transport across membranes is often mediated by ATP-binding cassette (ABC) transporters, which utilize ATP to translocate diverse molecules. Cyclic β-glucans (CβGs) are critical for host interaction of the Rhizobiales, including the zoonotic pathogen Brucella. CβGs are exported into the periplasmic space by the cyclic glucan transporter (Cgt). The interaction of an ABC transporter with a polysaccharide substrate has not been visualized so far. Here we use single-particle cryoelectron microscopy to elucidate the structures of Cgt from Brucella abortus in four conformational states. The substrate-bound structure reveals an unusual binding pocket at the height of the cytoplasmic leaflet, whereas ADP-vanadate models hint at an alternative mechanism of substrate release. Our work provides insights into the translocation of large, heterogeneous substrates and sheds light on protein-polysaccharide interactions in general.

Stable copper anode enabled by an ionic conducting sulfurized interphase

Lithium metal is one of the most promising anodes for non-aqueous battery because of its high capacity and low potential, and recently, lithium-free anode has been proposed which can further increase the real electrode capacity by utilizing lithium (Li) deposition and dissolution on copper (Cu) current collector. However, either Li or Li-free anode has been much plagued by the solid electrolyte interphase (SEI) issues, dendrite growth and dead Li formation induced by slower Li+-diffusion across the interphase and/or difficult Li nucleation on heterogeneous substrate. In this work, constructing an artificial copper sulfide (CuS) layer on Cu was proposed to address these issues. Copper sulfide has been loaded on Cu substrate through a facile vapor-deposition method. The extra layer reduced the contact between electrolyte and electrode. Additionally, a favorable interphase was generated by the in-situ conversion of CuS, which was composed of sub-micron lithium sulfide (Li2S) and Cu particles. The former optimized the SEI composition structure and improved the Li+ diffusion pathway, and the latter decreased the real local current density. With these assistances, dense and uniform Li deposition on Cu was achieved. The Li|S-Cu cell realized 300 times stable cycling and the Li@S-Cu|LiFePO4 full cell could well maintain the capacity as long as 200 cycles. This work provides an alternative strategy to regulate the electrode/electrolyte interface and sheds more lights on the Li deposition/dissolution reaction kinetics.

Polyoxometalate‐Soft Matter Composite Materials: Design Strategies, Applications, and Future Directions

AbstractMolecular metal oxides or polyoxometalates (POMs) offer unrivaled properties in areas ranging from catalysis and energy conversion through to molecular electronics, biomimetics, and theranostics. While POMs are ubiquitous metal oxide model systems studied in most areas of chemistry and materials science, their technological deployment is often hampered by their molecular nature, as this leads to increased degradation, leaching, and loss of reactivity, particularly when harsh applications, such as water electrolysis, thermal catalysis or highly basic/acidic reaction solutions are targeted. Therefore, immobilization of POMs on heterogeneous substrates has recently become a central theme in POM research. While early studies focused mainly on metal oxide and semiconductor supports, more recently, POM integration in soft matter matrices including polymers, conductive polymers, hydrogels, and stimuli‐responsive matrices leads to breakthroughs in multifunctional composite design. This Review summarizes pioneering experimental and theoretical progress in this emerging field over the last decade, highlighting current challenges that need to be overcome to allow a more widespread technological deployment and providing the authors’ view of some of the most promising future directions of the research field. In addition, the current understanding of correlations between structure (on the molecular, nano‐ and microscale) and reactivity in POM polymer composites is summarized, so that rational materials design can be further developed.

Combined contact force and local impedance dynamics during repeat atrial fibrillation catheter ablation.

Background: Optimal lesion formation during catheter-based radiofrequency current (RFC) ablation depends on electro-mechanical tip-tissue coupling measurable via contact force (CF) and local impedance (LI) monitoring. We aimed to investigate CF and LI dynamics in patients with previous atrial fibrillation (AF) ablation who frequently present with heterogenous arrhythmia substrate. Methods: Data from consecutive patients presenting for repeat AF or atrial tachycardia ablation using a novel open-irrigated single-tip ablation catheter were studied. RFC applications were investigated regarding CF, LI and the maximum LI drop (∆LI) for evaluation of ablation efficacy. ∆LI > 20 Ω was defined as a successful RFC application. Results: A total of 730 RFC applications in 20 patients were analyzed. Baseline CF was not associated with baseline LI (R = 0.06, p = 0.17). A mean CF < 8 g during ablation resulted in lower ∆LI (<8 g: 13 Ω vs. ≥ 8 g: 16 Ω, p < 0.001). Baseline LI showed a better correlation with ∆LI (R = 0.35, p < 0.001) compared to mean CF (R = 0.17, p < 0.001). Mean CF correlated better with ∆LI in regions of low (R = 0.31, p < 0.001) compared to high (R = 0.21, p = 0.02) and intermediate voltage (R = 0.17, p = 0.004). Combined CF and baseline LI predicted ∆LI > 20 Ω (area under the receiver operating characteristic curve (AUC) 0.75) better compared to baseline LI (AUC 0.72), mean CF (AUC 0.60), force-time integral (AUC 0.59) and local bipolar voltage (0.55). Conclusion: Combination of CF and LI may aid monitoring real-time catheter-tissue electro-mechanical coupling and lesion formation within heterogenous atrial arrhythmia substrate in patients with repeat AF or atrial tachycardia ablation.

A novel method for visualization and quantification of nerve density in transmural biopsies after myocardial infarction

Abstract Introduction Abnormal cardiac innervation plays an important role in arrhythmogenicity after myocardial infarction (MI). To study the innervation state after cardiac damage and ventricular arrhythmias, accurate quantification of nerve density is important. However, as cardiac nerves are very small structures, the histological quantification of nerves requires high resolution images, thus far proved extremely challenging and has never been performed transmurally. Aim To develop a method to analyze nerve density in large transmural biopsies after MI. Method Transmural myocardial biopsies from 4 swine, 3 months after MI, were stained with Picrosirius Red (fibrosis) and Beta-III-Tubulin (autonomic nerves). Fibrosis cut-offs were used to classify the biopsies into MI core (&amp;gt;59.8%), borderzone (BZ) (14.3–59.8%) or remote zone (RZ) (&amp;lt;14.3%). Each biopsy was quantified with a custom software pipeline, involving Python, Matlab and ImageJ. The biopsy was graphically divided into a 1x1mm grid. Using fixed values, nerve and myocardial tissue areas were thresholded and subjected to a quality check and artefact removal, followed by further division into 0.1x0.1mm squares. The nerve density per square was calculated and classified into denervation, hypoinnervation, normal innervation and hyperinnervation according to cut-offs (5th, 95th percentile) derived from 3 control swine. Finally, squares were located back to the original position within the biopsy allowing visualization and quantification of the different innervation types. Currently these steps are being integrated into an easy-to-use framework. Results In all 121 analyzed biopsies (experimental swine n=83, control n=38), areas with variable nerve densities were observed, although the areas with denervation, hypo- and hyperinnervation were largest in the MI core and BZ. Normal innervation was observed in 94.9% (93.8–96.0%) of the total biopsy area in the RZ, decreased in the BZ biopsies, 87.9% (85.1–92.4%, p&amp;lt;0.001), and even lower in the MI core, 72.8% (66.3–75.8%, p&amp;lt;0.001). The percentage of denervation and hypoinnervation per biopsy was highest in the core biopsies, 16.7% (13.5–23.5%) and 3.8% (2.9–5.0%) respectively, lower in the BZ, 2.6% (1.6–6.5%, p&amp;lt;0.008) and 1.2% (0.8–1.7%, p=0.015) and even lower in the RZ, 1.2% (0.7–1.8%, p&amp;lt;0.001), 0.6% (0.3–1.3, p&amp;lt;0.001). Hyperinnervation was observed mainly in the BZ, 5.3% (3.7–9.4%) and remarkably, also in the core, 5.3% (3.7–9.4%, p&amp;gt;0.999), whilst being low in the RZ 2.6% (1.7–4.3%, p=0.002 and p=0.038 respectively). Conclusion This novel method allows successful visualization and quantification of nerve density after cardiac damage in transmural biopsies. Strikingly, alternating areas of different innervation types could be identified within the same biopsy after MI, indicating a potentially heterogenous substrate for arrhythmias. This method has the potential to be broadly applied to any research involving high resolution imaging of nerves in large tissues. Funding Acknowledgement Type of funding sources: None.

Seasonal context of Bristly Cave Crayfish Cambarus setosus habitat use and life history

Cave crayfishes are important members of groundwater communities, but many cave crayfishes are threatened or endangered. Unfortunately, we lack basic life history and ecological data that are needed for developing conservation plans for most cave crayfishes, especially the role of seasonal and annual fluctuations in structuring populations. Therefore, we determined the seasonal life history and habitat use of Cambarus setosus in Smallin Civil War Cave, Christian County, Missouri, United States. We conducted visual crayfish surveys over a 400 m section of the cave from 2006 to 2019. We used multinomial logit, multiple linear regression, and logistic regression models to estimate crayfish substrate, water depth, and water velocity use, respectively. All models included sex, carapace length, season, distance into the cave, and interactions between all variables and sex as predictor terms. We also used t-tests to assess morphometric differences between male and female crayfish. Six mark-recapture events (2010 to 2019) were used to estimate population sizes using a nil-recapture model. We attempted to age eight individuals using gastric mill bands, but annual bands were not discernable. We found reproductively active males during all seasons. We captured one ovigerous female during the spring, though ovigerous females were observed during show cave tours during spring, summer, and autumn. Male C. setosus were more likely to use homogenous and heterogeneous rock substrates and shallower and calmer water when compared to females; however, these relationships varied based on distance into the cave and season. Females sampled were significantly larger than males, and males regenerated chelae more often. Minimum population size estimates ranged from 9 to 159 individuals and indicated the population was relatively stable. Our data provide both a baseline population estimate for comparison with future studies and valuable trait information that is often lacking but useful for developing conservation efforts.

High-Pressure Die Casting: A Review of Progress from the EPSRC Future LiME Hub

This article provides an overview of high-pressure die casting (HPDC)-related research undertaken at the EPSRC Future LiME Hub between 2015–2022. The project aimed to identify the cause of variability in the tensile ductility of die-cast structures, and to develop novel processing techniques to address this issue. Variability in tensile ductility was related to the size of large pores and non-metallic inclusions. It was proposed that these non-metallic inclusions formed during the pyrolysis of commercial plunger lubricants in the shot sleeve, and that these large pores derived from dilatational strains introduced during semi-solid deformation. Processing parameters and die design were found to significantly influence the microstructure of die-cast products, and the subsequent variability in tensile ductility. To close, recent progress on the application of intensive melt shearing to HPDC is reviewed. Intensive melt shearing was found to induce significant grain refinement in both Al and Mg alloys due to the effective dispersion of native oxide particles, and the use of these particles as heterogeneous nucleation substrates. The presence of native oxide particles also enabled the use of novel heat treatment procedures that avoided conventional issues such as surface blistering and geometrical distortion.

Benthic community zonation from mesophotic to deep sea: Description of first deep-water kelp forest and coral gardens in the Madeira archipelago (central NE Atlantic)

The Madeira archipelago has a unique underwater landscape that is characterised by narrow shelves, steep slopes and a large submarine tributary system that boosts primary productivity in oligotrophic waters and thus offers a potential for hotspots of biodiversity. Despite this, there have been limited deep-water exploration activities with less than five expeditions since the 1960s. Here, we investigated the seabed on the southern side of the Madeira-Desertas Ridge using a manned submersible along a 3.8 km long transect starting at 366 m depth up the ridge shelf until its top at 73 m. Benthic habitats and community composition were documented with video along a depth gradient from mesophotic to deep sea. Six distinct biotopes were recognised (three deeper, and three shallower than 115 m depth). Our results showed a rich biodiversity with deep biotopes characterised by sponges and non-reef-building corals (e.g., Pachastrella monilifera, Viminella flagellum, Eunicella verrucosa) and shallow biotopes comprising macroalgae and the gorgonian Paramuricea cf. grayi. The pronounced benthic zonation reflects the steep environmental gradient that includes high topographic variation, heterogeneous substrates, and bidirectional regular wave-motion at the shallow mesophotic part. Together with biotic factors, such as low density of sea urchins and presence of predatory fish, this environment with unusual deep light penetration, a mesoscale cyclonic eddy, and deep wave-motion, has allowed the establishment of a mature deep-water kelp population of Laminaria ochroleuca in the plateau (max. &amp;gt;100 individuals p/100 m2). At the same time, a conspicuous coral fauna was observed on a wide range of soft to hard bottoms with several species taking advantage of the favourable hydrodynamic regime and seawater properties together with substratum availability to create coral gardens. These habitats were previously not known from Madeira, and their newfound discovery in the archipelago merit further investigation and protection.