Search

Abstract: Understanding the relationships among life history traits, density dependence, and population dynamics is a central goal in ecology. It is also vital if we are to predict how populations [...]

A large-wave generator can be used to test the results of the design philosophy when compared with measurements made with a completed torsional wave machine. The experiment involves clamping one end of the machine to a desk and pulling the other end with three spring balances. The key characteristic of the waves created with the machine is the motion of the rods.

Demonstrations of high voltage phenomena are among the most spectacular and visually beautiful illustrations of physics. Here, we describe a high potential generator (several hundred thousand volts) which is based on a resonant transformer, derived from a standard Tesla coil arrangement with high Q secondary coil. Control electronics have been implemented that allow the user to command single shot discharges, should they be required for a particular demonstration. We review the behavior of a coupled resonant system with relevance to the spark-gap excited Tesla circuit implemented in our generator. The importance of the Q factor in the secondary coil design is emphasized, but only with due regard to other design factors including the coupling coefficient and primary spark-gap, which in certain configurations can outweigh the benefits of achieving very high Q.

THE ANALYSIS BY T. A. GARDNER ET AL. OF THE decade-scale trajectory of reef decline in the Caribbean ('Long-term region-wide declines in Caribbean corals,' Reports, 15 Aug., p. 958) is [...]

Current challenges in AR waveguide technology are reviewed with reference to a new low‐cost compact wide‐field‐of‐view color waveguide display reference design using integrated dual axis beam expansion and a compact picture generation unit. [ABSTRACT FROM AUTHOR]

Large‐scale and long‐term changes in fish abundance and distribution in response to climate change have been simulated using both statistical and process‐based models. However, national and regional fisheries management requires also shorter term projections on smaller spatial scales, and these need to be validated against fisheries data. A 26‐year time series of fish surveys with high spatial resolution in the North‐East Atlantic provides a unique opportunity to assess the ability of models to correctly simulate the changes in fish distribution and abundance that occurred in response to climate variability and change. We use a dynamic bioclimate envelope model forced by physical–biogeochemical output from eight ocean models to simulate changes in fish abundance and distribution at scales down to a spatial resolution of 0.5°. When comparing with these simulations with annual fish survey data, we found the largest differences at the 0.5° scale. Differences between fishery model runs driven by different biogeochemical models decrease dramatically when results are aggregated to larger scales (e.g. the whole North Sea), to total catches rather than individual species or when the ensemble mean instead of individual simulations are used. Recent improvements in the fidelity of biogeochemical models translate into lower error rates in the fisheries simulations. However, predictions based on different biogeochemical models are often more similar to each other than they are to the survey data, except for some pelagic species. We conclude that model results can be used to guide fisheries management at larger spatial scales, but more caution is needed at smaller scales. [ABSTRACT FROM AUTHOR]

The stomach contents of 640 starry smooth‐hound Mustelus asterias from the north‐east Atlantic were examined. The diet was dominated by crustaceans (98.8% percentage of index of relative importance, %IRI), with the two main prey species being hermit crab Pagurus bernhardus (34% IRI) and flying crab Liocarcinus holsatus (15% IRI). Ontogenetic dietary preferences showed that smaller individuals [20–69 cm total length (LT) n = 283] had a significantly lower diversity of prey than larger individuals (70–124 cm LT, n = 348); however, 18 prey species were found exclusively in smaller individuals and eight prey taxa were found exclusively in larger individuals. Larger commercially important brachyurans such as edible crab Cancer pagurus and velvet swimming crab Necora puber were more prevalent in the diet of larger individuals. Specimens from the North Sea ecoregion had a lower diversity of prey types for a given sample size than fish from the Celtic Seas ecoregion. Whilst cumulative prey curves did not reach an asymptote, this was primarily due to the high taxonomic resolution utilized and 95% of the diet was described by just seven crustacean taxa. The trophic level (TL) was calculated as 4.34 when species‐level prey categories were used. This fine‐scale taxonomic resolution resulted in a TL estimate close to a whole level above that estimated using wider taxonomic groupings. This large bias has important methodological implications for TL studies based on categorized prey data, particularly those of predatory fish. [ABSTRACT FROM AUTHOR]

Halophyte distributions on saltmarshes are strongly related to elevation in the tidal frame. However, collinearity between elevation, the consequent inundation regime, and sediment waterlogging/redox potential obscures the proximate causes of distribution patterns. We sought to distinguish the effects of elevation per se from those of waterlogging by manipulating microtopography.We experimentally manipulated elevation by ±15 cm at locations that spanned the elevation ranges of three saltmarshes recently reactivated by managed coastal realignment. Experimental plots were initially cleared of any vegetation. Elevation and sediment redox potential were determined for each plot. We planted five perennial species (Armeria maritima, Atriplex portulacoides, Limonium vulgare, Plantago maritima and Triglochin maritima) in half of the plots, recording survival over 4 years, and monitored natural colonization of the other plots.Overall, redox potential increased with elevation. Sediments were more oxidizing in raised plots and more reducing in lowered plots. Redox reductions in lowered plots were in line with those that would be predicted from the overall redox/elevation relationship, but increases in raised plots were greater than predicted from elevation alone.Plant colonization and survival was poorer in lowered plots and, for most species, improved in raised plots. This poorer colonization and survival can, in part, be attributed to the concomitant alterations in redox potential and elevation in the tidal frame, but microtopographic manipulation also had substantial independent effects on plant performance, including on the survival of all planted species and the colonization of Puccinellia maritima, Salicornia europaea agg. and Tripolium pannonicum.Synthesis. Microtopography can have effects on sediment chemistry and plant performance similar in magnitude to those of overall tidal elevation. Understanding how its effects modulate the relationship between tidal elevation, redox and other environmental conditions helps clarify the abiotic factors that fundamentally determine halophyte colonization and survival. These results support the use of topographic manipulation to enhance the diversity of created saltmarshes. [ABSTRACT FROM AUTHOR]

DigiLens Switchable Bragg Gratings enable digitally reconfigurable waveguides with form factors and field of view surpassing those of competing technologies. DigiLens waveguides can be laminated to integrate functions such as color displays and eye‐tracking seamlessly with minimal impact on form factor. Features and benefits of this breakthrough technology are reviewed. [ABSTRACT FROM AUTHOR]

We examined succession of the rhizosphere microbiota of three model plants (Arabidopsis, Medicago and Brachypodium) in compost and sand and three crops (Brassica, Pisum and Triticum) in compost alone. We used serial inoculation of 24 independent replicate microcosms over three plant generations for each plant/soil combination. Stochastic variation between replicates was surprisingly weak and by the third generation, replicate microcosms for each plant had communities that were very similar to each other but different to those of other plants or unplanted soil. Microbiota diversity remained high in compost, but declined drastically in sand, with bacterial opportunists and putative autotrophs becoming dominant. These dramatic differences indicate that many microbes cannot thrive on plant exudates alone and presumably also require carbon sources and/or nutrients from soil. Arabidopsis had the weakest influence on its microbiota and in compost replicate microcosms converged on three alternative community compositions rather than a single distinctive community. Organisms selected in rhizospheres can have positive or negative effects. Two abundant bacteria are shown to promote plant growth, but in Brassica the pathogen Olpidium brassicae came to dominate the fungal community. So plants exert strong selection on the rhizosphere microbiota but soil composition is critical to its stability. microbial succession/ plant-microbe interactions/rhizosphere microbiota/selection. [ABSTRACT FROM AUTHOR]

The article analyzes the natural variation for the requirement of vernalization temperature in Arabidopsis thaliana flowering plant accessions which found the dependence of the vernalization on the cold-induced epigenetic silencing of the floral repressor locus FLC.

Plant-microbe interactions in the rhizosphere have important roles in biogeochemical cycling, and maintenance of plant health and productivity, yet remain poorly understood. Using RNA-based metatranscriptomics, the global active microbiomes were analysed in soil and rhizospheres of wheat, oat, pea and an oat mutant (sad1) deficient in production of anti-fungal avenacins. Rhizosphere microbiomes differed from bulk soil and between plant species. Pea (a legume) had a much stronger effect on the rhizosphere than wheat and oat (cereals), resulting in a dramatically different rhizosphere community. The relative abundance of eukaryotes in the oat and pea rhizospheres was more than fivefold higher than in the wheat rhizosphere or bulk soil. Nematodes and bacterivorous protozoa were enriched in all rhizospheres, whereas the pea rhizosphere was highly enriched for fungi. Metabolic capabilities for rhizosphere colonisation were selected, including cellulose degradation (cereals), H2 oxidation (pea) and methylotrophy (all plants). Avenacins had little effect on the prokaryotic community of oat, but the eukaryotic community was strongly altered in the sad1 mutant, suggesting that avenacins have a broader role than protecting from fungal pathogens. Profiling microbial communities with metatranscriptomics allows comparison of relative abundance, from multiple samples, across all domains of life, without polymerase chain reaction bias. This revealed profound differences in the rhizosphere microbiome, particularly at the kingdom level between plants. [ABSTRACT FROM AUTHOR]

Highlights: [•] Multigenerational demographic responses of Artemia to EMS genotoxicity were assessed by matrix population modelling. [•] Population growth rate λ assessed for three generations was proportionally more sensitive to juvenile survival. [•] Effect of EMS on juvenile fertility contributed more to variations in λ. [•] Multigenerational consequences of genotoxicity were greater in asexual Artemia. [•] Ecological risk assessments should include information from multigenerational studies. [Copyright &y& Elsevier]

Highlights: [•] A discard ban may not achieve the CFP reform objective of reduced unwanted catches. [•] A discard ban and effort controls create weak incentives for selective fishing. [•] Catch quotas create strong incentives for avoidance of regulated species only. [•] Economic impacts are unevenly spread unless catch quotas are set differentially. [•] Vessels targeting non-quota species could see the largest reductions in income. [Copyright &y& Elsevier]

The high demand for shells of the large reef-associated gastropodTrochus niloticusin the manufacture of mother-of-pearl buttons has resulted in a widespread decline of its population. As a consequence, juvenile mass production and restocking has been practiced as one of the many conservation measures. Trochus has long been successfully bred in captivity, but culturing of juveniles until ready for release is faced with many problems, including the shortage of natural food. Terrestrial plants have traditionally been used by fishermen as food in keeping wild trochus juveniles, but their potential use in intermediate culture of trochus has not been evaluated. We conducted four growth trials for 60–120 days, rearing hatchery-produced juveniles (10–28-mm shell diameter) at different stocking densities in indoor tanks and sea cages, with coconut leaves as the main or an additional substrate. An average growth rate of 4.4 mm mo−1(95% CL 4.0–4.7 mm mo−1) for all stocking densities was achieved in growth trials using small cages deployed at 5–6 m on the reef slope, which was comparable to growth rates in the wild. This growth rate was three times higher than in trials using large metal cages on the reef slope, and 2 to 23 times higher than indoor trials using wooden tanks or small cages in concrete tanks. Survival rates were as high as 99%. Incidence of escape in sub-tidal cages was low except when some cages were damaged by strong waves. The results indicate that trochus juveniles can be successfully cultured at high density in sub-tidal cages with coconut leaves as substrate. [ABSTRACT FROM PUBLISHER]

Intentional release of wild-caught individuals has been widely used to establish new populations of the commercially valuable but threatened reef gastropodTrochus niloticusin oceanic islands. Is this also a viable strategy to enhance depleted populations of this species and other marine invertebrates? We monitored growth and survival of 765 translocated individuals and 486 in their original habitat for 5–9 months. Individuals translocated to a severely overexploited reef (mainland Palawan) grew 2–3 times faster than those at Tubbataha Reefs Natural Park, Phillipines. Despite variations in growth between the three sites, survival probabilities were consistently high, ranging between 0.77 and 0.92. So translocation is feasible, and sites at which a species has previously been found are likely to be suitable for their growth and survival. If site management can control over-fishing, this approach is likely to be a valuable tool for enhancing field populations of a large invertebrates likeTrochusthat have a short lived planktonic larva. [ABSTRACT FROM PUBLISHER]