Diel vertical migration and feeding of copepods at an oceanic site near South Georgia

first_imgTwelve Longhurst Hardy Plankton Recorder (LHPR) profiles were taken over a 16 h period in January 1990, in order to study feeding of four copepod species at an Antarctic oceanic site near South Georgia. Vertical distributions of their life stages, as well as those of dominant competitors and predators, are described in relation to the feeding cycles of Calanoides acutus CV, Calanus simillimus CV, Calanus propinquus CV and Rhincalanus gigas CIII, CV and CVI♀. Comparisons with vertical ring-net catches, which were used for concomitant gutevacuation experiments, demonstrated the suitability of the LHPR for these fine-scale studies. Planktonic predators, with the exception of the diel migrant Themisto gaudichaudii, resided deeper than the herbivores. During the day and around midnight, when feeding rates were low, species and stages reached their maximum vertical separation. At these times, new generation copepodites of the four species lived progressively deeper and the overwintered generation (i.e., R. gigas Stages CIV, CV, CVI) were progressively shallower. During the afternoon or evening (depending on species), all stages older than CII, as well as Euphausia frigida and T. gaudichaudii, migrated upwards, to amass in the surface mixed layer. Feeding was restricted to darkness, although R. gigas commenced several hours before dusk. In detail their migration and feeding differed widely, with combinations of unimodal and apparent bimodal cycles. As a whole, the results suggest that (1) feeding could occur during sinking as well as during upward migrations, (2) upward migrations were not always associated with feeding increases, and (3) individuals appeared to descend after filling their guts.last_img read more

Fossil angiosperm wood: its role in the reconstruction of biodiversity and palaeoenvironment

first_imgFossil wood is subject to different taphonomic, sampling and recognition biases in the palaeobotanical record when compared with leaves and palynomorphs. Wood therefore provides a systematically independent source of information that can increase our knowledge of past biodiversity and environments. Increase in fossil wood records from Cretaceous and Tertiary sediments helps further the understanding of trends in anatomical specialization through geological time. These data can then be used to distinguish such specialization from anatomical response to environmental change. Two case studies, a Late Cretaceous early Tertian’ wood flora from Antarctica and a lower Tertiary w ood flora from southern England, have been used to exemplify the importance of studying the fossil wood component of palaeofloras.last_img read more

Parasite treatment affects maternal investment in sons

first_imgParasitism can be a major constraint on host condition and an important selective force. Theoretical and empirical evidence shows that maternal condition affects relative investment in sons and daughters; however, the affect of parasitism on sex ratio in vertebrates is seldom considered. Here we demonstrate experimentally that parasitism constrains the ability of mothers to rear sons in a long lived seabird, the European shag Phalacrocorax aristotelis. The effect contributes to the decline in offspring survival as the breeding season progresses and hence has important population-level consequences for this, and potentially other, seasonal breeders.last_img

Airborne gravity reveals interior of Antarctic volcano

first_imgUnderstanding Antarctic volcanoes is important as they provide a window on magmatic and tectonic processes of the Antarctic plate and contain datable records of ice-sheet changes. We present the results from the first detailed airborne radar and gravity surveys across James Ross Island, northern Antarctic Peninsula, which is dominated by Mt Haddington, an ice-covered Miocene-Recent alkaline stratovolcano. The surveys provide new insights into the subsurface structure of the volcano and hence its development, which are unavailable from the surface geology alone. We show that Mt Haddington is associated with a significant negative Bouguer gravity anomaly (>= 26 mGal), which suggests that there has not been significant pooling and solidification of a dense shallow-level mafic magma chamber during the growth of the volcano over at least the past 6 m.y., which is consistent with independent geochemical evidence. Simple flexural isostatic models cannot explain the localised negative Bouguer anomaly. 3D modelling techniques show that the negative anomaly is best explained by a shallow, low-density intra-crustal body with its top close to, or at, the surface. Although comparable gravity anomalies are commonly associated with large (similar to 20 km) ash-filled calderas, as seen at Yellowstone or Toba, there is no geological evidence on James Ross Island for a similar structure. We therefore propose that the James Ross Island volcanic edifice subsided into the thick underlying pile of relatively soft Jurassic and Cretaceous sediments, which were displaced by low-density hyaloclastite breccia. The type of deformation envisaged is similar to that associated with Concepciou, or lwaki volcanoes in South America, although Mt Haddington is much larger. (C) 2009 Elsevier B.V. All rights reserved.last_img read more

The thermal limits to life on Earth

first_imgLiving organisms on Earth are characterized by three necessary features: a set of internal instructions encoded in DNA (software), a suite of proteins and associated macromolecules providing a boundary and internal structure (hardware), and a flux of energy. In addition, they replicate themselves through reproduction, a process that renders evolutionary change inevitable in a resource-limited world. Temperature has a profound effect on all of these features, and yet life is sufficiently adaptable to be found almost everywhere water is liquid. The thermal limits to survival are well documented for many types of organisms, but the thermal limits to completion of the life cycle are much more difficult to establish, especially for organisms that inhabit thermally variable environments. Current data suggest that the thermal limits to completion of the life cycle differ between the three major domains of life, bacteria, archaea and eukaryotes. At the very highest temperatures only archaea are found with the current high-temperature limit for growth being 122 °C. Bacteria can grow up to 100 °C, but no eukaryote appears to be able to complete its life cycle above ∼60 °C and most not above 40 °C. The lower thermal limit for growth in bacteria, archaea, unicellular eukaryotes where ice is present appears to be set by vitrification of the cell interior, and lies at ∼−20 °C. Lichens appear to be able to grow down to ∼−10 °C. Higher plants and invertebrates living at high latitudes can survive down to ∼−70 °C, but the lower limit for completion of the life cycle in multicellular organisms appears to be ∼−2 °Clast_img read more

A high-resolution model of the external and induced magnetic field at the Earth’s surface in the northern hemisphere

first_imgWe describe a method of producing high-resolution models of the Earth’s combined external and induced magnetic field using the method of empirical orthogonal functions (EOFs) applied to the SuperMAG archive of ground-based magnetometer data. EOFs partition the variance of a system into independent modes, allowing us to extract the spatiotemporal patterns of greatest dynamical importance without applying the a priori assumptions of other methods (such as spherical harmonic analysis, parameterized averaging, or multivariate regression). We develop an approach based on that of Beckers and Rixen (2003) and use the EOF modes to infill missing data in a self-consistent manner. Applying our method to a north polar case study spanning February 2001 (chosen for its proximity to solar maximum and good data coverage), we demonstrate that 41.7% and 9.4% of variance is explained by the leading two modes, respectively, describing the temporal variations of the disturbance polar types 2 and 1 (DP2 and DP1) patterns. A further 14.1% of variance is explained by four modes that describe separate aspects of the motion of the DP1 and DP2 systems. Thus, collectively over 65% of variance is described by the leading six modes and is attributable to DP1 and DP2. This attribution is based on inspection of the spatial morphology of the modes and analysis of the temporal variation of the mode amplitudes with respect to solar wind measures and substorm occurrence. This study is primarily a demonstration of the technique and a prelude to a model spanning the full solar cyclelast_img read more

Kansas City Chiefs player Laurent Duvernay-Tardif graduates from medical school

first_img Written by FacebookTwitterLinkedInEmailJustin K. Aller/Getty Images(KANSAS CITY, Mo.) — Laurent Duvernay-Tardif appears to be a man of many talents both on and off the football field.The Kansas City Chiefs player graduated Tuesday with his degree from McGill University’s medical school in Montreal after a long eight years of studying while playing football.“This is it! Today I become a doctor!” he wrote in a tweet with a picture of his new white medical coat painted with “Dr. Duvernay-Tarif” and his football jersey number 76.Laurent planned to have a medical career when he first enrolled at McGill, but he was drafted to the NFL as the Chiefs’ starting right guard in 2014.His love of football brought him back to the field as he became the best college player in Canada, all while following a plan created by the school to keep him on track to finish his degree.Laurent recently said he promised himself that he was going to finish his studies and get his medical degree while still playing the game.“It’s one of those life projects that you promise yourself you’re going to accomplish,” he said when speaking to ESPN Tuesday.He is the first active NFL player to hold a medical degree. Earlier this offseason, Duvernay-Tardif said he wanted the NFL to allow him to add M.D. to the end of his name on his Chiefs’ jersey.“It’s official now! #LDTMD! THANK YOU to all of you who supported me. If there was only one lesson to be learned from all of this is that with passion and determination, we are all capable of going beyond our limits!” Duvernay-Tardif wrote on Twitter.The Kansas City Chiefs tweeted his graduation photo to show their support for the athlete.Copyright © 2018, ABC Radio. All rights reserved. Beau Lundcenter_img May 29, 2018 /Sports News – National Kansas City Chiefs player Laurent Duvernay-Tardif graduates from medical schoollast_img read more

Tom Brady shares heartfelt note on his parents’ 50th wedding anniversary

first_img FacebookTwitterLinkedInEmailJoe Faraoni / ESPN Images(NEW YORK) — Tom Brady often speaks about his deep appreciation for his parents and the hand they’ve had in his great success.The New England Patriots quarterback shared a lengthy post to celebrate their 50th wedding anniversary on Friday.Alongside Galynn Brady and Tom Brady Sr.’s wedding photo and a more recent photo of the couple, the football star wrote, “The strength of their marriage has always been an inspiration and the best example to me and my sisters of what true love, respect and commitment mean.”He explained that their union has helped him and his three sisters navigate life’s challenges.“Life always has its ups and downs and their togetherness in good and bad taught us teamwork,” he wrote. “Their trust, love and dedication as parents taught us how to become the parents we are today.”He went on, “They have always put our family first and instilled in us the values they were taught from their parents, which we now carry on and teach our own kids. They have always encouraged us to attain milestones and we’re honored to celebrate this one they’ve achieved.”“We love you so much, mom and dad,” he added. “Happy anniversary!!!”Brady is extremely close with his family. They were at Super Bowl LIII in February to watch him get his sixth ring after the Patriots beat the Los Angeles Rams 13-3.Copyright © 2019, ABC Radio. All rights reserved. Written by April 22, 2019 /Sports News – National Tom Brady shares heartfelt note on his parents’ 50th wedding anniversarycenter_img Beau Lundlast_img read more

Curran Walsh Added To USU Men’s Basketball Coaching Staff

first_img Brad James Tags: Craig Smith/Curran Walsh/Dwayne Wade/Jimmy Butler/Lindenwood-Belleville/Loyola Marymount/Rajon Rondo/USU Men’s Basketball FacebookTwitterLinkedInEmailLOGAN, Utah-Friday, Utah State men’s basketball head coach Craig Smith announced an addition to his staff in Curran Walsh.Walsh joins Smith’s staff after spending the last two seasons at Loyola Marymount of Los Angeles.While with the Lions, Walsh served as a graduate assistant, helping the squad to 22 wins, their most since the 1989-90 season.Walsh is a 2016 graduate of Lindenwood-Belleville of Belleville, Ill. and started for the NAIA-affiliated Lynx all four seasons of his collegiate career.He earned academic all-American Midwest Conference honors in 2015 and 2016.Walsh also earned a Master’s in educational studies at Loyola Marymount.Walsh has also played a key role in the player development process of many NBA players, including Jimmy Butler, Dwayne Wade and Rajon Rondo, among others. June 7, 2019 /Sports News – Local Curran Walsh Added To USU Men’s Basketball Coaching Staff Written bylast_img read more