Reduced Nearshore Warming Associated With Eastern Boundary Upwelling Systems

Coastal marine biodiversity within eastern boundary upwelling systems (EBUS) is closely linked to the cooler sea temperatures associated with them. It has been suggested that global warming could lead to enhanced sea surface cooling in EBUS via the intensification of upwelling-favorable winds. Conversely, increased stratification and the widespread warming of the world’s oceans could drive these systems in the opposite direction. These competing mechanisms hold the potential for driving the thermal envelopes of EBUS toward – or away from – the thermal envelopes found outside EBUS, with likely contrasting implications for biodiversity conservation in each scenario. Here we characterize the patterns of net sea surface warming rates over more than three decades throughout the global ocean to evaluate if waters inside EBUS are changing differently from those outside EBUS. Results point to a trend of reduced warming inside EBUS, especially along the nearshore. We found that reduced net warming was prevalent in Pacific EBUS but restricted in Atlantic EBUS. In contrast, net warming in the coastal ocean outside EBUS was pervasive and generally associated with proximity to land. Our results suggest that EBUS have been responding to climate change differently from the rest of the global ocean, potentially buffering coastal biomes from decades of global warming

Inactivating SARS-CoV-2 Using 275 nm UV-C LEDs through a Spherical Irradiation Box: Design, Characterization and Validation

We report on the design, characterization and validation of a spherical irradiation system for inactivating SARS-CoV-2, based on UV-C 275 nm LEDs. The system is designed to maximize irradiation intensity and uniformity and can be used for irradiating a volume of 18 L. To this aim: (i) several commercially available LEDs have been acquired and analyzed; (ii) a complete optical study has been carried out in order to optimize the efficacy of the system; (iii) the resulting prototype has been characterized optically and tested for the inactivation of SARS-CoV-2 for different exposure times, doses and surface types; (iv) the result achieved and the efficacy of the prototype have been compared with similar devices based on different technologies. Results indicate that a 99.9% inactivation can be reached after 1 min of treatment with a dose of 83.1 J/m2

Defects in III-N LEDs: experimental identification and impact on electro-optical characteristics

III-N light-emitting-diodes (LEDs) are subject of intense investigations, thanks to their high efficiency and great reliability. The quality of the semiconductor material has a significant impact on the electro-optical performance of LEDs: for this reason, a detailed characterization of defect properties and the modeling of the impact of defects on device performance are of fundamental importance. This presentation addresses this issue, by discussing a set of recent case studies on the topic; specifically, we focus on the experimental characterization of defects, and on the modeling of their impact on the electro-optical characteristics of the devices

Age and reproduction in two Antarctic plunderfishes (Artedidraconidae) from the Weddell Sea.

The Antarctic plunderfishes (Artedidraconidae) are a poorly known component of the bottom fish fauna inhabiting the continental shelf of the High Antarctic Zone. Biological data on these fishes are still rather scarce and generally based on only a few specimens. To increase the knowledge of this group, we investigated the reproductive biology and population age structure of Artedidraco skottsbergi and Dolloidraco longedorsalis, the most abundant plunderfishes collected during the 2013/2014 expedition of the RV Polarstern in the Weddell Sea. Based on macroscopic and histological analyses, we found that both species exhibited prolonged gametogenesis and produced few eggs. Estimates of absolute and relative fecundity were lower in A. skottsbergi than in D. longedorsalis, ranging from 69 \ub1 7 oocytes per female and 11.4 \ub1 4.3 oocytes/g, and from 209 \ub1 73 oocytes per female and 13.5 \ub1 3.7 oocytes/g, respectively. Female size at first spawning was estimated to be 9.5 and 11 cm in A. skottsbergi and D. longedorsalis, respectively. Age and growth were assessed through otolith readings, and estimates of age ranged between 6-14 years in A. skottsbergi and 3-14 years in D. longerdorsalis. The von Bertalanffy growth parameters were only estimated for D. longedorsalis (L\uf0a5 = 12.5 cm, k = 0.27, t0 = - 0.06). The results of this study provide insights into some of the biological aspects of these species and shed new light on their life strategies, which show similarities to those of other notothenioids

Impact of Generation and Relocation of Defects on Optical Degradation of Multi-Quantum-Well InGaN/GaN-Based Light-Emitting Diode

The defectiveness of InGaN-based quantum wells increases with low indium contents, due to the compressive strain induced by the lattice mismatch between the InGaN and GaN layers, and to the stronger incorporation of defects favored by the presence of indium. Such defects can limit the performance and the reliability of LEDs, since they can act as non-radiative recombination centers, and favor the degradation of neighboring semiconductor layers. To investigate the location of the layers mostly subjected to degradation, we designed a color-coded structure with two quantum wells having different indium contents. By leveraging on numerical simulations, we explained the experimental results in respect of the ratio between the emissions of the two main peaks as a function of current. In addition, to evaluate the mechanisms that limit the reliability of this type of LED, we performed a constant-current stress test at high temperature, during which we monitored the variation in the optical characteristics induced by degradation. By comparing experimental and simulated results, we found that degradation can be ascribed to an increment of traps in the active region. This process occurs in two different phases, with different rates for the two quantum wells. The first phase mainly occurs in the quantum well closer to the p-contact, due to an increment of defectiveness. Degradation follows an exponential trend, and saturates during the second phase, while the quantum well close to the n-side is still degrading, supporting the hypothesis of the presence of a diffusive front that is moving from the p-side towards the n-side. The stronger degradation could be related to a lowering of the injection efficiency, or an increment of SRH recombination driven by a recombination-enhanced defect generation process

Injection-limited efficiency of InGaN LEDs and impact on electro-optical performance and ageing: a case study

This paper investigates the factors that influence the efficiency and reliability of InGaN based visible light emitting diodes with non-optimized carrier injection. The devices under test are LEDs with a single quantum well with a nominal emission wavelength of 495 nm at I = 100 mA. We stressed the devices with a constant current density of J = 80 A/cm2, at room temperature, for 25000 minutes. We monitored the optical performance of the devices before and during stress. From the preliminary characterization we observed an increment in the optical power followed by a blue shift as a function of current. Simulation results highlight an asymmetric carrier injection, in particular a lack of electrons in the low bias regime. The low injection efficiency is also confirmed by temperature-dependent measurements, where we observed an increment in the OP with increasing temperature. During an ageing experiment, we observed an increment in OP for high injection level, accompanied with a blue shift in the peak emission wavelength. This result suggests an improvement in the injection efficiency and or a better carrier confinement. In this regard, we performed photoluminescence measurements during stress, which confirm the hypothesis of a better carrier confinement. In particular, PL signal show an increasing trend during the ageing process, which can be ascribed to the generation of negatively charged defects in the quantum barrier, with consequent impact on carrier confinement

Applying landscape metrics to species distribution model predictions to characterize internal range structure and associated changes

Distributional shifts in species ranges provide critical evidence of ecological responses to climate change. Assessments of climate-driven changes typically focus on broad-scale range shifts (e.g. poleward or upward), with ecological consequences at regional and local scales commonly overlooked. While these changes are informative for species presenting continuous geographic ranges, many species have discontinuous distributions—both natural (e.g. mountain or coastal species) or human-induced (e.g. species inhabiting fragmented landscapes)—where within-range changes can be significant. Here, we use an ecosystem engineer species (Sabellaria alveolata) with a naturally fragmented distribution as a case study to assess climate-driven changes in within-range occupancy across its entire global distribution. To this end, we applied landscape ecology metrics to outputs from species distribution modelling (SDM) in a novel unified framework. SDM predicted a 27.5% overall increase in the area of potentially suitable habitat under RCP 4.5 by 2050, which taken in isolation would have led to the classification of the species as a climate change winner. SDM further revealed that the latitudinal range is predicted to shrink because of decreased habitat suitability in the equatorward part of the range, not compensated by a poleward expansion. The use of landscape ecology metrics provided additional insights by identifying regions that are predicted to become increasingly fragmented in the future, potentially increasing extirpation risk by jeopardising metapopulation dynamics. This increased range fragmentation could have dramatic consequences for ecosystem structure and functioning. Importantly, the proposed framework—which brings together SDM and landscape metrics—can be widely used to study currently overlooked climate-driven changes in species internal range structure, without requiring detailed empirical knowledge of the modelled species. This approach represents an important advancement beyond predictive envelope approaches and could reveal itself as paramount for managers whose spatial scale of action usually ranges from local to regional

A broad-scale long-term dataset of Sabellaria alveolata distribution and abundance curated through the REEHAB (REEf HABitat) Project

Numerous reef-forming species have declined dramatically in the last century, many of which have been insufficiently documented due to anecdotal or hard-to-access information. One of them, the honeycomb worm Sabellaria alveolata (L.) is a tube-building polychaete that can form large reefs, providing important ecosystem services such as coastal protection and habitat provision. It ranges from Scotland to Morocco, yet little is known about its distribution outside of the United Kingdom, where it is protected and where there is a strong heritage of natural history and sustained observations. As a result, online marine biodiversity information systems currently contain haphazardly distributed records of S. alveolata. One of the objectives of the REEHAB project (http://www.honeycombworms.org) was to combine historical records with contemporary data to document changes in the distribution and abundance of S. alveolata. Here we publish the result of the curation of 331 sources, gathered from literature, targeted surveys, local conservation reports, museum specimens, personal communications by authors and by their research teams, national biodiversity information systems (i.e. the UK National Biodiversity Network (NBN), https://nbn.org.uk/) and validated citizen science observations (i.e. https://www.inaturalist.org/). 80% of these records were not previously referenced in any online information system. Additionally, historic field notebooks from Edouard Fischer-Piette and Gustave Gilson were scanned for S. alveolata information and manually entered. Each of the 21512 S. alveolata records were checked for spatial and taxonomic accuracy, particularly in the English Channel and the North Sea where incorrectly identified observations of intertidal Sabellaria spinulosa were recorded. A further 54 observations are recorded as &lsquo;Sabellaria spp.&rsquo; as the available information did not allow for an identification to species level. Many sources reported abundances based on the semi-quantitative SACFOR scale whilst others simply noted its presence, and others still verified both its absence and presence. The result is a curated and comprehensive dataset spanning over two centuries on the past and present global distribution and abundance of S. alveolata. Sabellaria alveolata records projected onto a 50km grid. When SACFOR scale abundance scores were given to occurrence records, the highest abundance value per grid cell was retained.</span