Genetic diversity and population structure of the franciscana dolphin,Pontoporia blainvillei,in Southern Buenos Aires,Argentina

The franciscana dolphin, Pontoporia blainvillei, is endemic to the coastal waters of the southwestern Atlantic Ocean and the most endangered dolphin in the area. Four Franciscana Management Areas (FMAs) are currently recognised; however, results of genetic studies suggest the requirement for additional FMAs and highlight the need for more detailed studies in the southern extreme of the species distribution. With this aim, we studied the genetic diversity and population structure of the species analysing an mtDNA control region fragment (434?bp) in 44 individuals collected in four sampling sites located in Southern Buenos Aires. Haplotype diversity (H?=?0.75?±?0.05) was mostly higher than the observed in endangered or near threatened odontocetes. Population structure analyses suggest that three different genetic populations should be recognised within FMA IV: Northern, Eastern and Southern Buenos Aires. Altogether, these results should be taken into account in future conservation plans for the species.     

Astronomical frequencies for climate research at the decadal to century time scale

Short-term variations of the elements representing the Earth's motion around the Sun and its rotation have been analyzed over the last 6000 years using 1-year steps. Their low-frequency part is compared first to the values obtained from a secular theory of the planetary long-term motion showing that they can be considered reliable enough to represent adequately the motion of the Earth over the last 5000 years. Spectral analysis of these values shows that the main periodicities are 2.67, 3.98, 5.26, 5.93, 7.9, 9.8, 11.9, 14.7, 15.8, 29, 42, 61, 122, 165 and 250 years for the eccentricity as well as for the climatic precession, with an additional component at around 930 years for the eccentricity and around 840 years for the climatic precession. Periodicities at 2.67, 3.8, 5.9, 8.0, 9.3, 11.9, 14.7, 18.6, 29, 135, 250 and 840 yr are also shown for the obliquity. Spectral analyses of the daily July mid-month insolation at 65°N show essentially the same periodicities as the climatic precession and the obliquity, i.e. 2.67, 3.98, 5.92, 8.1, 11.9, 15.7, 18.6, 29, 40, 61 and around 900 years. Finally a wider analysis of the insolation pattern was performed related to the large periodicity band of the insolation time series for the solstices and the equinoxes for 7 different latitudes. In equatorial latitudes the insolation variance is largely explained by precession. But precession dominates everywhere with the obliquity signal being stronger at polar latitudes at the solstices. The amplitudes of the insolation change at these frequencies is of the order of 0.2 Wm^–2 at the maximum. Offprint requests to: A Berger     

Lessons learned from bacterial transport research at the South Oyster Site

This paper provides a review of bacterial transport experiments conducted by a multiinvestigator, multiinstitution, multidisciplinary team of researchers under the auspices of the U.S. Department of Energy (DOE). The experiments were conducted during the time period 1999-2001 at a field site near the town of Oyster, Virginia known as the South Oyster Site, and included four major experimental campaigns aimed at understanding and quantifying bacterial transport in the subsurface environment. Several key elements of the research are discussed here: (1) quantification of bacterial transport in physically, chemically, and biologically heterogeneous aquifers, (2) evaluation of the efficacy of conventional colloid filtration theory, (3) scale effects in bacterial transport, (4) development of new methods for microbial enumeration and screening for low adhesion strains, (5) application of novel hydrogeophysical techniques for aquifer characterization, and (6) experiences regarding management of a large field research effort. Lessons learned are summarized in each of these areas. The body of literature resulting from South Oyster Site research has been widely cited and continues to influence research into the controls exerted by aquifer heterogeneity on reactive transport (including microbial transport). It also served as a model (and provided valuable experience) for subsequent and ongoing highly-instrumented field research efforts conducted by DOE-sponsored investigators.     

西藏丁青弧前蛇绿岩的地球化学特征

丁青蛇绿岩位于班化湖－丁青－怒江蛇绿岩带的东段，其地幔岩出露规模是该带中最大的。本文报道的丁青蛇绿岩主要由地幔橄榄岩、堆晶岩、辉长岩和斜长花岗岩组成。蛇绿岩剖面上覆硅岩中的放射虫化石是早株罗世和晚三叠世诺利克期的，中侏罗统砂岩和砾岩不整合覆盖在蛇绿岩之上，由此确定丁青蛇绿岩是晚三叠－早侏罗世的，在中株罗世之前侵位，丁青蛇绿岩属于玻安岩系，玻安岩的特点是富Si、Mg和大离子亲石元素（LILE），贫高场强元素（Ti、P、Zr、Y、Yb和Nb）。丁青蛇绿岩的堆晶岩、辉长岩和辉绿岩均具“U”型REE分布，暗示丁青玻安岩是由于亏损的地幔源岩和来自消减带的水和流体两组分的混合形成的。丁青玻安岩的地球化学特征类似西太平洋第三纪玻安岩，而明显不同于MORB的地球化学性质， 表明丁青玻安岩应当形成于洋内岛弧的弧前环境，属于弧前蛇绿岩。