Abstract: Partitioning resources is a key mechanism for avoiding intraspecific competition and maximizing individual energy gain. However, in sexually dimorphic species it is difficult to discern if partitioning is due to competition or the different resource needs of morphologically distinct individuals. In the highly dimorphic southern elephant seal, there are intersexual differences in habitat use; at Iles Kerguelen, males predominantly use shelf waters, while females use deeper oceanic waters. There are equally marked intrasexual differences, with some males using the nearby Kerguelen Plateau, and others using the much more distant Antarctic continental shelf ( 2,000 km away). We used this combination of inter and intrasexual behavior to test two hypotheses regarding habitat partitioning in highly dimorphic species. (a) that intersexual differences in habitat use will not appear until the seals diverge in body size and (b) that some habitats have higher rates of energy return than others. In particular, that the Antarctic shelf would provide higher energy returns than the Kerguelen Shelf, to offset the greater cost of travel. We quantified the habitat use of 187 southern elephant seals (102 adult females and 85 subadult males). The seals in the two groups were the same size ( 2.4 m) removing the confounding effect of body size. We found that the intersexual differences in habitat use existed before the divergence in body size. Also, we found that the amount of energy gained was the same in all of the major habitats. This suggests that the use of shelf habitats by males is innate, and a trade-off between the need to access the large benthic prey available on shelf waters, against the higher risk of predation there. Intrasexual differences in habitat use are another trade-off; although there are fewer predators on the Antarctic shelf, it is subject to considerable interannual fluctuations in sea-ice extent. In contrast, the Kerguelen Plateau presents more consistent foraging opportunities, but contains higher levels of predation. Habitat partitioning in this highly dimorphic species is therefore the result of complex interplay of life history strategies, environmental conditions and predation pressure.

Abstract: In December 2019, the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group (V-MOD) adopted the thirteenth generation of the International Geomagnetic Reference Field (IGRF). This IGRF updates the previous generation with a definitive main field model for epoch 2015.0, a main field model for epoch 2020.0, and a predictive linear secular variation for 2020.0 to 2025.0. This letter provides the equations defining the IGRF, the spherical harmonic coefficients for this thirteenth generation model, maps of magnetic declination, inclination and total field intensity for the epoch 2020.0, and maps of their predicted rate of change for the 2020.0 to 2025.0 time period.

Abstract: Since The Signature Of The Minamata Convention On Mercury In 2017, National Regulation Coordinated At An International Level Will Come Into Force In Order To Limit Anthropogenic Emissions And Therefore Protect The Human Health And Ecosystem From This Highly Toxic Pollutant. One Need To Evaluate The Efficiency Of National Measures, And Long-term Monitoring Of Atmospheric Mercury (Hg) Is An Important Tool To Address The Changes Over Time Of Emission Sources, Transport, And Deposition Patterns.the Global Mercury Observation System (Gmos) Project Was Funded By The European Commission (Http://www.gmos.eu) And Started In November 2010 With The Overall Goal To Develop A Coordinated Global Observing System To Monitor Hg On A Global Scale, Including A Large Network Of Ground-based Monitoring Stations. To Date, More Than 40 Ground-based Monitoring Sites Constitute The Global Network Covering Many Regions Where Little To No Observational Data Were Available Before Gmos (Sprovieri Et Al., 2016). All Gmos Work Is Now Continued In The Framework Of The International Frame Work Of Gos4m (Global Observation System For Mercury – Http://www.gos4m.org)although Essential To Fully Understand The Cycling Of Mercury At The Global Scale, Mercury Species Records In The Southern Hemisphere Were Really Scarce Before Gmos. In This Context, An Atmospheric Mercury Monitoring Station Has Been Set Up On Amsterdam Island (37?48 S, 77?34 E) In The Remote Southern Indian Ocean In 2012. Since 2012, We Continuously Measured Gaseous Mercury Species With A 15 Min Frequency. Angot Et Al. (2014) Discussed The First Two Years Of This Record, Using Principally Wind Sector Analysis And Air Mass Back Trajectories. They Also Include In Their Analysis The Unique Continuous Record Of Radon 222 And 220 (Thoron) (Polian Et Al., 1986; Kritz Et Al., 1990). Radon 222 And 220 (Thoron) Activities Can Be Used To Distinguish Local Soil Outgassing From Remote Continental Source. Combined With Meteorological Data, The Change Of Activities Are Then Powerful Tool To Classify Air Mass Origin For The Atmospheric Gaseous Mercury Record. Rapid And Sharp Variations Of Radon 222 Activity, Referred To As &Ldquo;radonic Storms” (Lambert Et Al., 1970) And Ascribed To Strong Continental Air Mass Advection, Are Then Observed At Amsterdam Island. The Occurrence Of Radonic Storms Was Estimated To Be About 4 % In 2012 And 7 % In 2013. Considering The Works Realized In 2014, The Goal Of This Internship Is To Deeper Explore The Relationships Between The Collected Gaseous Elemental Mercury And Observed Radon (222rn / 220rn) Activities In The Entire Data Set. In Particular, We Will Study The Specific And Coupled Trend Of These Compounds, The Frequency And Intensity Of Radonic Storm Occurrence And Their Potential Link With The Gaseous Elemental Mercury Cycle. Local Meteorology Data As Well As Backtrajectories Simulation (Hysplit And/or Flexpart Model) Will Be Also Used.