Productivity and Temperature as Drivers of Seasonal and Spatial Variations of Dissolved Methane in the Southern Bight of the North Sea

Dissolved CH₄ concentrations in the Belgian coastal zone (North Sea) ranged between 670 nmol l^?1 nearshore and 4 nmol l^?1 offshore. Spatial variations of CH₄ were related to sediment organic matter (OM) content and gassy sediments. In nearshore stations with fine sand or muddy sediments, the CH₄ seasonal cycle followed water temperature, suggesting methanogenesis control by temperature in these OM-rich sediments. In offshore stations with permeable sediments, the CH₄ seasonal cycle showed a yearly peak following the chlorophyll-a spring peak, suggesting that in these OM-poor sediments, methanogenesis depended on freshly produced OM delivery. This does not exclude the possibility that some CH₄ might originate from dimethylsulfide (DMS) or dimethylsulfoniopropionate (DMSP) or methylphosphonate transformations in the most offshore stations. Yet, the average seasonal CH₄ cycle was unrelated to those of DMS(P), very abundant during the Phaeocystis bloom. The annual average CH₄ emission was 126 mmol m^?2 y^?1 in the most nearshore stations (~4 km from the coast) and 28 mmol m^?2 y^?1 in the most offshore stations (~23 km from the coast), 1260–280 times higher than the open ocean average value (0.1 mmol m^?2 y^?1). The strong control of CH₄ by sediment OM content and by temperature suggests that marine coastal CH₄ emissions, in particular in shallow areas, should respond to future eutrophication and warming of climate. This is supported by the comparison of CH₄ concentrations at five stations obtained in March 1990 and 2016, showing a decreasing trend consistent with alleviation of eutrophication in the area.     

Estimating hominid life history: the critical interbirth interval

Unlike any great apes, humans have expanded into a wide variety of habitats during the course of evolution, beginning with the transition by australopithecines from forest to savanna habitation. Novel environments are likely to have imposed hominids a demographic challenge due to such factors as higher predation risk and scarcer food resources. In fact, recent studies have found a paucity of older relative to younger adults in hominid fossil remains, indicating considerably high adult mortality in australopithecines, early Homo, and Neanderthals. It is not clear to date why only human ancestors among all hominoid species could survive in these harsh environments. In this paper, we explore the possibility that hominids had shorter interbirth intervals to enhance fertility than the extant apes. To infer interbirth intervals in fossil hominids, we introduce the notion of the critical interbirth interval, or the threshold length of birth spacing above which a population is expected to go to extinction. We develop a new method to obtain the critical interbirth intervals of hominids based on the observed ratios of older adults to all adults in fossil samples. Our analysis suggests that the critical interbirth intervals of australopithecines, early Homo, and Neanderthals are significantly shorter than the observed interbirth intervals of extant great apes. We also discuss possible factors that may have caused the evolutionary divergence of hominid life history traits from those of great apes.     

A Novel Graphene Oxide Wrapped Na2Fe2(SO4)3/C Cathode Composite for Long Life and High Energy Density Sodium‐Ion Batteries

The cathode materials in the Na‐ion battery system are always the key issue obstructing wider application because of their relatively low specific capacity and low energy density. A graphene oxide (GO) wrapped composite, Na₂Fe₂(SO₄)₃@C@GO, is fabricated via a simple freeze‐drying method. The as‐prepared material can deliver a 3.8 V platform with discharge capacity of 107.9 mAh g^?1 at 0.1 C (1 C = 120 mA g^?1) as well as offering capacity retention above 90% at a discharge rate of 0.2 C after 300 cycles. The well‐constructed carbon network provides fast electron transfer rates, and thus, higher power density also can be achieved (75.1 mAh g^?1 at 10 C). The interface contribution of GO and Na₂Fe₂(SO₄)₃ is recognized and studied via density function theory calculation. The Na storage mechanism is also investigated through in situ synchrotron X‐ray diffraction, and pseudocapacitance contributions are also demonstrated. The diffusion coefficient of Na⁺ ions is around 10^?12–10^?10.8 cm² s^?1 during cycling. The higher working voltage of this composite is mainly ascribed to the larger electronegativity of the element S. The research indicates that this well‐constructed composite would be a competitive candidate as a cathode material for Na‐ion batteries.     

Similar responses in morphology,growth, biomass allocation,and photosynthesis in invasive <Emphasis Type="Italic">Wedelia trilobata</Emphasis> and native congeners to CO<Subscript>2</Subscript> enrichment

Both global change and biological invasions threaten biodiversity worldwide. However, their interactions and related mechanisms are still not well elucidated. To elucidate potential traits contributing to invasiveness and whether ongoing increase in CO₂ aggravates invasions, noxious invasive Wedelia trilobata and native Wedelia urticifolia and Wedelia chinensis were compared under ambient and doubled atmospheric CO₂ concentrations in terms of growth, biomass allocation, morphology, and physiology. The invader had consistently higher leaf mass fraction (LMF) and specific leaf area than the natives, contributing to a higher leaf area ratio, and therefore to faster growth and invasiveness. The higher LMF of the invader was due to lower root mass fraction and higher fine root percent. On the other hand, the invader allocated a higher fraction of leaf nitrogen (N) to photosynthetic apparatus, which was associated with its higher photosynthetic rate, and resource use efficiency. All these traits collectively contributed to its invasiveness. CO₂ enrichment increased growth of all studied species by increasing actual photosynthesis, although it decreased photosynthetic capacities due to decreased leaf and photosynthetic N contents. Responses of the invasive and native plants to elevated CO₂ were not significantly different, indicating that the ongoing increase in CO₂ may not aggravate biological invasions, inconsistent with the prevailing results in references. Therefore, more comparative studies of related invasive and native plants are needed to elucidate whether CO₂ enrichment facilitates invasions.     

Assessment of Maturity,Reproduction and Reproductive Potentials of Torpedo Scad, <Emphasis Type="Italic">Megalaspis cordyla</Emphasis> (Linnaeus, 1758) from Northern Arabian Sea Coast of Pakistan

Port landing specimens of torpedo scad, Megalaspis cordyla were collected at monthly intervals from August 2013 to June 2014 from the northern Arabian Sea coast of Pakistan. The life history characteristics revealed that torpedo scad has a prolonged breeding season which occurred with two peaks: from May to June and from November to February. The spawning seasonality was also validated with microscopic gonad examination.The highest GSI value was noted in May and January whereas the lowest in November was recorded for both sexes. The age at which individuals of both sexes become 50% mature (t₅₀) was estimated as 2.44 year. Life span (t_max) calculated as 3.96 years for male and females. The size of 270 and 265 mm at which 50% individuals attained sexual maturity (L₅₀) was determined for males and females respectively. The reproductive potential (fecundity)was made from ten ripe females ranged from 29–43.8 cm TL and weighing 220–540 g of IV–V developmental stage was enumerated as 32306–236677 eggs (CV = 2.135) with an average number of eggs 86544 counted per ripe female/season. This study contains fundamental data of an important fish species in the northern Arabian Sea coast of Pakistan. It provides vital information to the fisheries managers for implementation on sustainable use of the resource during spawning season.     

Natural selection on ecophysiological traits of a fern species in a temperate rainforest

Unlike other species of the genus Blechnum, the fern Blechnum chilense occurs in a wide range of habitats in Chilean temperate rainforest, from shaded forest understories to abandoned clearings and large gaps. We asked if contrasting light environments can exert differential selection on ecophysiological traits of B. chilense. We measured phenotypic selection on functional traits related to carbon gain: photosynthetic capacity (A _max), dark respiration rate (R _d), water use efficiency (WUE), leaf size and leaf thickness in populations growing in gaps and understorey environments. We assessed survival until reproductive stage and fecundity (sporangia production) as fitness components. In order to determine the potential evolutionary response of traits under selection, we estimated the genetic variation of these traits from clonally propagated individuals in common garden experiments. In gaps, survival of B. chilense was positively correlated with WUE and negatively correlated with leaf size. In contrast, survival in shaded understories was positively correlated with leaf size. We found positive directional fecundity selection on WUE in gaps population. In understories, ferns of lower R _d and greater leaf size showed greater fecundity. Thus, whereas control of water loss was optimized in gaps, light capture and net carbon balance were optimized in shaded understories. We found a significant genetic component of variation in WUE, R _d and leaf size. This study shows the potential for evolutionary responses to heterogeneous light environments in functional traits of B. chilense, a unique fern species able to occupy a broad successional niche in Chilean temperate rainforest.     

Morphological variation in the horse: defining complex traits of body size and shape

Horses, like many domesticated species, have been selected for broad variation in skeletal size. This variation is not only an interesting model of rapid evolutionary change during domestication, but is also directly applicable to the horse industry. Breeders select for complex traits like body size and skeletal conformation to improve marketability, function, soundness and performance in the show ring. Using a well-defined set of 35 measurements, we have identified and quantified skeletal variation in the horse species. We collected measurements from 1215 horses representing 65 breeds of diverse conformation such as the American Miniature, Shetland Pony, Arabian Horse, Thoroughbred, Shire and Clydesdale. Principal components analysis has identified two key dimensions of skeletal variation in the horse. Principal component 1 is positively correlated with every measurement and quantifies overall body size. Principal component 2 captures a pattern of bone widths vs. lengths and thus quantifies variation in overall bone thickness. By defining these complex skeletal traits, we have created a framework for whole genome association studies to identify quantitative trait loci that contribute to this variation.     

Statistical analysis of the Bacterial Carbohydrate Structure Data Base (BCSDB): Characteristics and diversity of bacterial carbohydrates in comparison with mammalian glycans

Background  

There are considerable differences between bacterial and mammalian glycans. In contrast to most eukaryotic carbohydrates, bacterial glycans are often composed of repeating units with diverse functions ranging from structural reinforcement to adhesion, colonization and camouflage. Since bacterial glycans are typically displayed at the cell surface, they can interact with the environment and, therefore, have significant biomedical importance.