Species and sexual isolating mechanisms in sibling species of giant petrels Macronectes

first_imgThe two sibling species of giant petrels Macronectes halli and M. giganteus are the dominant avian scavengers in the Southern Ocean ecosystem. They breed sympatrically at a number of sub-Antarctic sites. This paper synthesises data from a detailed study at South Georgia to examine the importance of various interspecific and intersexual differences between these closely related species. Morphological, breeding, dietary, feeding and moult characteristics were investigated. The most significant interspecific differences are a six week separation in the onset of breeding and the importance of seal carrion to male M. halli, the earlier breeding species. There is a strong sexual size dimorphism with females being only 75–80% of the weight of males in both species. Intersexual dietary differences are stronger than interspecific ones and females also have later primary moult schedules. Reproductive isolation and ecological adaptations are discussed in relation to the present distribution of giant petrels, comprising a more restricted sub-Antarctic species (M. halli) and a widespread Antarctic species (M. giganteus). It is suggested that the marked sexual dimorphism evolved before the two taxa became specifically distinct.last_img read more

Validating and improving elevation data of a satellite-image map of Filchner-Ronne Ice Shelf, Antarctica, with results from ERS-I

first_imgA satellite-image map with surface-elevation contours of Filchner Ronne Ice Shelf has been published previously as a topographic map. The image map was constructed from a mosaic of 69 Landsat Multispectral Scanner (MSS) images and NOAA AVHRR data. The standard deviation in position in the central part of the mosaic is ±125m. Topographic-glaciologic features were taken from Landsat scenes and represent the best coastline of this region. Surface elevations have been calculated from airborne and ground measurements of either ice thickness (by assuming hydrostatic equilibrium) or barometric pressure. Accuracies vary from ±2 to ±7 m, Oversnow trigonometric levelling in the northeastern part of the ice shelf, tied to sea level at the ice front, has given accuracies of ± 1m. Accuracies reduce to about ±20 m in the grounded ice areas, ERS-I radar-altimeter data over the ice shelf have been processed to give ellipsoidal heights elevation above the ellipsoid), Geoidal reductions have been used to convert these to orthometric heights (elevation above sea level). No tidal corrections have been applied. The overall accuracy of the radar-altimeter-derived elevations is estimated to be better than ±5m. There are noticeable differences from the topographic map in the central part where the radar data indicate a lower surface. However, the maps agree to within the stated error figures.last_img read more

Strontium isotope correlation of the basal Maastrichtian Stage in Antarctica to the European and US biostratigraphic schemes

first_imgNew 87Sr/86Sr dating allows the correlation of a marker horizon within the prolific Late Cretaceous Gunnarites antarcticus faunal assemblage of the Cape Lamb Member, Snow Hill Island Formation, Vega Island, Antarctica with reference sections in Europe and the USA. This horizon is between 81.5 and 96.5 m above the base of the G antarcticus assemblage. Replicate analysis of six macrofossils from within it yielded a mean value for 87Sr/86Sr of 0.707 735 9 ± 0.000 004 3 (± 2 s.e., n=17). This ratio in turn yields a numerical age of 71.0 ± 0.2 Ma when compared to the standard 87Sr/s6Sr reference curve for the latest Cretaceous, for which the Campanian-Maastrichtian boundary is placed at 71.3 ± 0.5 Ma. The value of 0.707 735 9 ± 0.000 004 3 correlates to a level in the Belemnella lanceolata belemnite Zone of the Chalk of northwestern Germany that is 2.5 ± 5 m beneath the base of the overlying B. pseudobtusa Zone (and 7.5 m above the Campanian-Maastrichtian belemnite boundary), and to an interval within the ammonite zonation of the US Western Interior that spans the early Maastrichtian Baculites baculus and B. eliasi zones, but with a most likely level within the B. eliasi Zone. An earliest Maastrichtian age is thereby determined for the Antarctic horizon, and indeed for the entire G. antarcticus assemblage. Gunnarites, sensu lato, is an important ammonite marker for the base of the Maastrichtian throughout the southern high-latitude regions, and the associated large heteromorph ammonite Diplomoceras may comprise a macrofossil link back to the Maastrichtian type sections.last_img read more

Polar marine ecosystems: major threats and future change

first_imgThis review of polar marine ecosystems covers both the Arctic and Antarctic, identifying the major threats and, where possible, predicting their possible state(s) in 2025. Although the two polar regions are similar in their extreme photoperiod, low temperatures, and in being heavily influenced by snow and ice, in almost all other respects they are very different. The Arctic Ocean is a basin surrounded by continental landmasses, close to, and influenced by, large populations and industrial activities. In contrast, the Southern Ocean is contiguous with all the other great oceans and surrounds a single land mass; Antarctica is remote from major centres of population and sources of pollution. Marine environments in both polar regions have been highly disturbed by fishing activity, but, in terms of pollution, some areas remain among the most pristine in the world. There are, however, both local and global pressures. Over the 2025 time horizon, the greatest concern for the Arctic is probably the ecological implications of climate change, particularly insofar as sea ice extent and duration are likely to be affected. Such changes are not expected to be as pronounced in the Southern Ocean over this time period, and concerns are related more to direct threats from harvesting of marine living resources, and the ability to manage these fisheries sustainably. In both polar regions, the capacity of marine ecosystems to withstand the cumulative impact of a number of pressures, including climate change, pollution and overexploitation, acting synergistically is of greatest concern.last_img read more

Ice Shelf Water plume flow beneath Filchner-Ronne Ice Shelf, Antarctica

first_imgA two-dimensional plume model is used to study the interaction between Filchner-Ronne Ice Shelf, Antarctica and its underlying ocean cavity. Ice Shelf Water (ISW) plumes are initiated by the freshwater released from a melting ice shelf and, if they rise, may become supercooled and deposit marine ice due to the pressure increase in the in situ freezing temperature. The aim of this modeling study is to determine the origin of the thick accretions of marine ice at the base of Filchner-Ronne Ice Shelf and thus improve our understanding of ISW flow paths. The model domain is defined from measurements of ice shelf draft, and from this ISW the model is able to predict plumes that exit the cavity in the correct locations. The modeled plumes also produce basal freezing rates that account for measured marine ice thicknesses in the western part of Ronne Ice Shelf. We find that the freezing rate and plume properties are significantly influenced by the confluence of plumes from different meltwater sources. We are less successful in matching observations of marine ice under the rest of Filchner-Ronne Ice Shelf, which we attribute primarily to this model’s neglect of circulations in the ocean outside the plume.last_img read more

Areas of importance for seabirds tracked from French southern territories, and recommendations for conservation

first_imgSeabirds are increasingly threatened worldwide, with population declines for many species that are faster than in any other group of birds. Here the Important Bird Area (IBA) criteria recommended by BirdLife International were applied to a large tracking dataset collected from a range of seabirds, to identify areas of importance at an ocean basin scale. Key areas were identified using tracks obtained from both the breeding and non-breeding periods of 10 species that have different habitat requirements. These species range in their IUCN threat status from Least Concern to Critically Endangered. An evaluation of spatial overlap between the key areas for these species and the jurisdiction of Regional Fisheries Management Organisations (RFMOs), national Exclusive Economic Zones (EEZs) and other stakeholder bodies highlighted the major importance of the French EEZs (around Crozet, Kerguelen and Amsterdam Islands) for seabird conservation. The majority of the candidate marine IBAs that were identified were located in the High Seas, where Marine Protected Areas cannot easily be designated under existing international agreements, except in the Commission for the Conservation of Antarctic Marine Living Resources Convention Area. In the short term, it seems that only fisheries regulations (through international agreements) can bring about efficient protection for seabirds in the High Seas. The BirdLife IBA approach, although sensitive to heterogeneity in the data (species selected, inclusion of different life stages, years etc.), proved valuable for selecting important areas corresponding to large-scale oceanographic structures that are considered to be key foraging habitats for many species.last_img read more

The influence of substorms on extreme rates of change of the surface horizontal magnetic field in the United Kingdom

first_imgWe investigate how statistical properties of the rate of change R of the surface horizontal magnetic field in the United Kingdom differ during substorm expansion and recovery phases compared with other times. R is calculated from 1‐min magnetic field data from three INTERMAGNET observatories—Lerwick, Eskdalemuir, and Hartland and between 1996 and 2014—nearly two solar cycles. Substorm expansion and recovery phases are identified from the SuperMAG Lower index using the Substorm Onsets and Phases from Indices of the Electrojet method. The probability distribution of R is decomposed into categories of whether during substorm expansion and recovery phases, in enhanced convection intervals, or at other times. From this, we find that 54–56% of all extreme R values (defined as above the 99.97th percentile) occur during substorm expansion or recovery phases. By similarly decomposing the magnetic local time variation of the occurrence of large R values (>99th percentile), we deduce that 21–25% of large R during substorm expansion and recovery phases are attributable to the Disturbance Polar (DP)1 magnetic perturbation caused by the substorm current wedge. This corresponds to 10–14% of all large R in the entire data set. These results, together with asymptotic trends in occurrence probabilities, may indicate the two‐cell DP2 magnetic perturbation caused by magnetospheric convection as the dominant source of hazardous R > 600 nT/min that is potentially damaging to the U.K. National Grid. Thus, further research is needed to understand and model DP2, its mesoscale turbulent structure, and substorm feedbacks in order that GIC impact on the National Grid may be better understood and predicted.last_img read more

SLCC Men’s Basketball Star Named Scenic West Player of the Week

first_img Brad James Written by FacebookTwitterLinkedInEmailTAYLORSVILLE, Utah-Monday, the #8 Salt Lake Community College men’s basketball team received a prestigious honor from the Scenic West Athletic Conference.Cameron Mack, a 6-2 redshirt freshman guard out of Austin, Texas, was named as the Scenic West Conference player of the week for the 9-2 Bruins.Mack, a commit to traditional NCAA Division I power St. John’s of the Big East Conference, averaged 24 points a game last week for the Bruins at the Florida Tournament.In an 88-84 win over nationally-ranked Eastern Florida, Mack netted 24 points against the Titans.In an 80-75 loss to Florida Southwestern Community College, Mack’s 39 points paced the Bruins against the Buccaneers. Tags: Big East/Eastern Florida Titans/Florida Southwestern Buccaneers/SLCC Men’s Basketball/St. John’s/SWAC Player of the Week December 4, 2018 /Sports News – Local SLCC Men’s Basketball Star Named Scenic West Player of the Weeklast_img read more

David Ortiz throws out first pitch at Fenway Park, surprises crowd 3 months after he was shot

first_img Beau Lund Written by FacebookTwitterLinkedInEmailFILE photo by Scott Clarke / ESPN Images(BOSTON) — Beloved Boston icon David Ortiz brought the crowd at Fenway Park to its feet after making a surprise appearance three months after he was shot in the Dominican Republic.Ortiz, the retired Red Sox slugger, was met with roaring applause and a standing ovation Monday night when he came out to throw out the first pitch ahead of the team’s game against the New York Yankees. It was his first public appearance since the shooting on June 9.“First of all, I want to thank God for giving me a second opportunity in my life to be able to be here with all of you,” Ortiz said before the game. ” I want to thank the Red Sox, my real family, they have always been there for me, supported [me]. With what happened to me, they were the first supporting me. Thank you very much, Red Sox family.”Ortiz, who is affectionately known as “Big Papi,” was sitting at the Dial Bar and Lounge in Santo Domingo when a gunman came behind him and opened fire. An investigation into the shooting revealed that Ortiz was not the intended target and the bullets were meant for his friend, Sixto David Fernandez.Oritz underwent at least three surgeries after he was shot in the back. He was released from the hospital nearly 7 weeks after the shooting.Rolfi Ferreira-Cruz, 25, of New Jersey, was arrested and identified as the alleged gunman who shot Ortiz. Thirteen other suspects have also been arrested for their alleged involvement in the shooting.Mookie Betts, the right fielder for the Red Sox, posted a tribute to Ortiz welcoming him back.“So glad to have you back! Love you big bro,” he wrote on Instagram.Red Sox fans were pleasantly surprised at both the appearance and how good he looked on Monday.“Everybody stood up. It was unbelievable,” one Red Sox fan told ABC Boston affiliate WCVB. “Everyone was just cheering. It was crazy.”“He actually looked really good when he came out,” the fan said. “I was surprised. I thought he’d be, like, maybe limping or with someone helping him, but he ran right out there.”Copyright © 2019, ABC Radio. All rights reserved.center_img September 10, 2019 /Sports News – National David Ortiz throws out first pitch at Fenway Park, surprises crowd 3 months after he was shotlast_img read more

New York Mets legend Tom Seaver dies at 75 after battle with dementia

first_img Written by FacebookTwitterLinkedInEmailmanusapon kasosod/iStockBy MARK OSBORNE, ABC News(NEW YORK) — The greatest pitcher in New York Mets history and one of the greatest in baseball history has died.Tom Seaver, known as “Tom Terrific,” died Monday at the age of 75. He had battled dementia in recent years, according to the Baseball Hall of Fame.“We are heartbroken to share that our beloved husband and father has passed away,” his wife Nancy Seaver and daughters, Sarah and Anne, said in a statement. “We send our love out to his fans, as we mourn his loss with you.”Seaver was elected to the Hall of Fame in 1992, appearing on 425 of 430 ballots.The flame-throwing righty won three Cy Young Awards (1969, 1973 and 1975) and went to the All-Star Game 12 times.“I am deeply saddened by the death of Tom Seaver, one of the greatest pitchers of all-time,” MLB Commissioner Rob Manfred said in a statement. “Tom was a gentleman who represented the best of our National Pastime. He was synonymous with the New York Mets and their unforgettable 1969 season. After their improbable World Series Championship, Tom became a household name to baseball fans — a responsibility he carried out with distinction throughout his life.”Copyright © 2020, ABC Audio. All rights reserved. Beau Lundcenter_img September 2, 2020 /Sports News – National New York Mets legend Tom Seaver dies at 75 after battle with dementialast_img read more