Effects of copper exposure on the metabolism of the mysid Praunus flexuosus

first_imgThe metabolism of a coastal mysid population ŽPraunus flexuosus. from the West Solent South England. has been studied in different seasons winter, spring and summer.. Metabolic responses to copper 0, 5, 25, 75 and 200 mg ly1 copper added. were measured in winter and summer at 24 h, 96 h and 10 days of exposure. The metabolic rates of P. flexuosus in controls were different between seasons. Respiration and ammonia excretion were 2.5 to 6 times lower in winter than in summer. O:N ratios also varied significantly with season from 3.5–5 in summer to8 in winter. Temperature dependency of respiration Q10s1.76. and excretion Q10s1.95. was moderate. Copper effects on metabolism resulted in a decrease of the O:N ratio, from values of 10 to values between 4 and 2. The metabolic responses to copper were stronger in summer than in winter, causing larger changes and being effective at lower concentrations. Alterations of the O:Nratio found in this study were a very sensitive indicator of sublethal and lethal toxicity.last_img read more

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Near-surface turbulent fluxes in stable stratification: calculation techniques for use in general-circulation models

first_imgPractically oriented flux-calculation techniques based on correction functions to the neutral drag and heat/mass transfer coefficients are further developed. In the traditional formulation, the correction functions depend only on the bulk Richardson number. However, data from measurements of turbulent fluxes and mean profiles in stable stratification over different sites exhibit too strong variability in this type of dependencies. Indirect evidence from climate and weather prediction modelling also shows that the traditional flux-calculation technique is not sufficiently advanced. It is conceivable that other mechanisms besides the surface-layer stratification and, therefore, other arguments besides the bulk Richardson number must be considered. The proposed technique includes a newly discovered effect of the static stability in the free atmosphere on the surface-layer scaling and accounts for the general essential difference between the roughness lengths for momentum and scalars. Besides bulk Richardson number, recommended correction functions depend on one more stability parameter, involving the Brunt–Visl frequency in the free atmosphere, and on the roughness lengths.last_img read more

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Remote islands reveal rapid rise of Southern Hemisphere sea debris

first_imgA generation of people have now grown up thinking that shorelines strewn with anthropogenic artefacts is normal. Yet this pehnomenon is just a few decades old and aesthetics and beach cleanups are only the tip of the iceberg – plastics at sea are poisoning, choking and starving large animals and transporting small organisms to places they’ve never been. It is now widely acknowledged that one of the great threats to global biodiversity is establishment of pest species, yet little is known of thier latest vector, our miracle material – plastic. Annual clear ups in the northern hemisphere show only little recent increases in marine litter but this study of remote southern shores and islands shows drastic increases in accumulation across the entire southern hemisphere over 3 decades. Although there is much variability, typically now >2 items per m per year strand at the equator and items now carry hitchhikers to the most southern shores of the Southern Ocean. The number of people per area of the globe match almost exactly the amount of rubbish stranding on the shores at any latitude. The rate of change seems most extreme on the shores of subAntarctic islands. Plastics are pushing pole-wards and the wilderness shores around Antarctica are becoming symbols of our waste culture.last_img read more

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Interactions between ice and ocean observed with phase-sensitive radar near an Antarctic ice-shelf grounding line

first_imgPrecise measurements of basal melting have been made at a series of 14 sites lying within a few kilometres of the grounding line of the Ronne Ice Shelf, Antarctica, where the ice thickness ranges from 1570 to 1940 m. The study was conducted over the course of 1 year and included a detailed survey of the horizontal deformation, as well as phase-sensitive radar measurements of the vertical displacement of both internal reflecting horizons and the ice-shelf base. Results from the surface survey show that the long-term viscous strain rate is modulated at tidal frequencies by (probably) elastic strains of order 10−5 per metre of tidal elevation. The radar measurements show a similar modulation of the long-term thinning/thickening of the ice shelf, with thickness oscillations up to a few centimetres in range. The long-term trends in ice thickness determined at points moving with the ice-shelf flow are consistent with a steady-state thickness profile. Vertical strain rates within the ice shelf were determined from the relative motion of internal reflectors. At two sites the observations were sufficient to discern the effect of tidal bending about a neutral surface 60% of the way down the ice column. Coincident measurements of horizontal and vertical strain imply a Poisson’s ratio of 0.5, and this combined with the asymmetric bending gives rise to the observed oscillations in thickness. At a number of sites the long-term viscous strain rates were found to be a linear function of depth. For an ice shelf this is an unexpected result. It can be attributed to the presence of significant vertical shear stresses set up close to the grounding line where the ice is still adjusting to flotation. Additional vertical motion arising from firn compaction was observed within the upper layers of the ice shelf. The additional motion was consistent with the assumption that firn density is a function only of the time since burial by steady surface accumulation. With both spatial and temporal fluctuations in the vertical strain rate accurately quantified it was possible to estimate the vertical motion of the ice-shelf base in response. Differences between the calculated and observed motion of the basal reflector arise because of basal melting. Derived melt rates at the 14 sites ranged from −0.11 ± 0.31 to 2.51 ± 0.10 ma−1, with a mean of 0.85 m a−1 and a standard deviation of 0.69 m a−1, and showed no signs of significant sub-annual temporal variability. There was no obvious global correlation with either ice thickness or distance from the grounding line, although melt rates tended to decrease downstream along each of the flowlines studied. Previous estimates of basal melting in this region have been obtained indirectly from an assumption that the ice shelf is locally in equilibrium and have included a broad range of values. Only those at the lower end of the published range are consistent with the directly measured melt rates reported here.last_img read more

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The biodiversity of the deep Southern Ocean benthos

first_imgOur knowledge of the biodiversity of the Southern Ocean (SO) deep benthos is scarce. In this review, we describe the general biodiversity patterns of meio-, macro- and megafaunal taxa, based on historical and recent expeditions, and against the background of the geological events and phylogenetic relationships that have influenced the biodiversity and evolution of the investigated taxa. The relationship of the fauna to environmental parameters, such as water depth, sediment type, food availability and carbonate solubility, as well as species interrelationships, probably have shaped present-day biodiversity patterns as much as evolution. However, different taxa exhibit different large-scale biodiversity and biogeographic patterns. Moreover, there is rarely any clear relationship of biodiversity pattern with depth, latitude or environmental parameters, such as sediment composition or grain size. Similarities and differences between the SO biodiversity and biodiversity of global oceans are outlined. The high percentage (often more than 90%) of new species in almost all taxa, as well as the high degree of endemism of many groups, may reflect undersampling of the area, and it is likely to decrease as more information is gathered about SO deep-sea biodiversity by future expeditions. Indeed, among certain taxa such as the Foraminifera, close links at the species level are already apparent between deep Weddell Sea faunas and those from similar depths in the North Atlantic and Arctic. With regard to the vertical zonation from the shelf edge into deep water, biodiversity patterns among some taxa in the SO might differ from those in other deep-sea areas, due to the deep Antarctic shelf and the evolution of eurybathy in many species, as well as to deep-water production that can fuel the SO deep sea with freshly produced organic matter derived not only from phytoplankton, but also from ice algae.last_img read more

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Geolocators map the wintering grounds of threatened Lesser Kestrels in Africa

first_imgAim To identify the wintering grounds of the threatened western European Lesser Kestrels to focus conservation efforts in those areas. Location Huelva Province, southern Spain, as breeding range, and western Africa (Senegal and Mauritania), as wintering range. Methods We used archival light level geolocators (1.5 g) to map the wintering areas and determine some characteristics of the migratory journeys of 20 adult Lesser Kestrels from the Iberian Peninsula tagged in 2007. Results Thirteen geolocators were recovered the following breeding season (2008) after attachment in 2007. Four recovered geolocators provided useful data. According to kernel density analyses, kestrels wintered near the Senegal River (border between Mauritania and Senegal). Pre-nuptial migration took longer than the post-nuptial migration, which may be the consequence of a loop migration. Main conclusions Geolocators have solved a crucial conservation question (i.e. the winter destination of western European Lesser kestrels), and these devices have thus proved useful to determine the location of the winter quarters of small sized migratory species. Our data indicate that European Lesser Kestrels winter in West Africa, in accordance with previous suggestions based on scattered observations during the winter months. This valuable information should serve to focus conservation efforts both in northern Senegal and southern Mauritania. Large roosts gathering thousands of lesser kestrels had been recorded in these areas over the years, but there was no previous confirmation of individuals staying all winter long. Specific and sustained protection of the roost sites, where the birds may be most vulnerable, should be sought in conjunction with local authorities.last_img read more

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Re-examining the roles of surface heat flux and latent heat release in a “hurricane-like” polar low over the Barents Sea

first_imgPolar lows are intense mesoscale cyclones that occur at high latitudes in both hemispheres during winter. Their sometimes evidently convective nature, fueled by strong surface fluxes and with cloud-free centers, have led to some polar lows being referred to as “arctic hurricanes.” Idealized studies have shown that intensification by hurricane development mechanisms is theoretically possible in polar winter atmospheres, but the lack of observations and realistic simulations of actual polar lows have made it difficult to ascertain if this occurs in reality. Here the roles of surface heat fluxes and latent heat release in the development of a Barents Sea polar low, which in its cloud structures showed some similarities to hurricanes, are studied with an ensemble of sensitivity experiments, where latent heating and/or surface fluxes of sensible and latent heat were switched off before the polar low peaked in intensity. To ensure that the polar lows in the sensitivity runs did not track too far away from the actual environmental conditions, a technique known as spectral nudging was applied. This was shown to be crucial for enabling comparisons between the different model runs. The results presented here show that (1) no intensification occurred during the mature, postbaroclinic stage of the simulated polar low; (2) surface heat fluxes, i.e., air-sea interaction, were crucial processes both in order to attain the polar low’s peak intensity during the baroclinic stage and to maintain its strength in the mature stage; and (3) latent heat release played a less important role than surface fluxes in both stages.last_img read more

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Full circumpolar migration ensures evolutionary unity in the Emperor penguin

first_imgDefining reliable demographic models is essential to understand the threats of ongoing environmental change. Yet, in the most remote and threatened areas, models are often based on the survey of a single population, assuming stationarity and independence in population responses. This is the case for the Emperor penguin Aptenodytes forsteri, a flagship Antarctic species that may be at high risk continent-wide before 2100. Here, using genome-wide data from the whole Antarctic continent, we reveal that this top-predator is organized as one single global population with a shared demography since the late Quaternary. We refute the view of the local population as a relevant demographic unit, and highlight that (i) robust extinction risk estimations are only possible by including dispersal rates and (ii) colony-scaled population size is rather indicative of local stochastic events, whereas the species’ response to global environmental change is likely to follow a shared evolutionary trajectorylast_img read more

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Johnny Manziel makes CFL preseason debut

first_img Beau Lund June 2, 2018 /Sports News – National Johnny Manziel makes CFL preseason debut FacebookTwitterLinkedInEmailPhoto by Allen Kee / ESPN Images(HAMILTON, Ontario) — Johnny Manziel made his Canadian Football League debut on Friday night, playing in a preseason game for the Hamilton Tiger-Cats. The former Heisman Trophy winner completed nine of his eleven pass attempts for 80 yards. None of his five possessions resulted in points.Manziel came on in relief of former University of Oregon quarterback Jeremiah Masoli. Earlier this week, Tiger-Cats head coach June Jones confirmed that Masoli will be the team’s starter when the season begins.Hamilton lost the game 36-18.Manziel last played in the NFL in 2015, and played just two games in The Spring League this April before signing with the Tiger-Cats.After the game, Manziel said he expects to get trash talk from opponents, but that he can take it.“I’m not here to be pushed over,” Manziel said. “You can come at me ’cause my name’s in the papers, because my name’s on TV…but I’m not backing down. I’m here for a reason. I’m here to play ball.”Copyright © 2018, ABC Radio. All rights reserved.center_img Written bylast_img read more

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Report: Jets to hire Adam Gase as next head coach

first_imgJanuary 10, 2019 /Sports News – National Report: Jets to hire Adam Gase as next head coach Written by Beau Lundcenter_img FacebookTwitterLinkedInEmailJoel Auerbach/Getty Images(NEW YORK) — It appears the New York Jets have chosen their next head coach.ESPN reports the team is expected to bring former Miami Dolphins head coach Adam Gase on board to lead the squad.Gase, 40, was fired by Miami on Dec. 31 after three seasons with the team. During his time with the Dolphins, the team went 23-25 but beat the Jets in five of their six matchups.The Jets have been searching for a new head coach since firing Todd Bowles after their last game this past season. Under Bowles’ leadership, New York went 24-40 in four seasons without any playoff appearances.Copyright © 2019, ABC Radio. All rights reserved.last_img read more

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