Research Article| February 01, 1998 A test of (Ge/Si)opal as a paleorecorder of (Ge/Si)seawater Gilles Bareille; Gilles Bareille 1Département de Géologie et Océanographie, CNRS URA 197, Université de Bordeaux I, Avenue des Facultés, 33405 Talence Cedex, France Search for other works by this author on: GSW Google Scholar Monique Labracherie; Monique Labracherie 1Département de Géologie et Océanographie, CNRS URA 197, Université de Bordeaux I, Avenue des Facultés, 33405 Talence Cedex, France Search for other works by this author on: GSW Google Scholar Richard A. Mortlock; Richard A. Mortlock 2Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar Ernst Maier-Reimer; Ernst Maier-Reimer 3Max-Planck Institut für Meteorologie, Bundesstrasse 55, 20146 Hamburg, Germany Search for other works by this author on: GSW Google Scholar Philip N. Froelich Philip N. Froelich 4School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332-0340 Search for other works by this author on: GSW Google Scholar Geology (1998) 26 (2): 179–182. https://doi.org/10.1130/0091-7613(1998)026<0179:ATOGSO>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Gilles Bareille, Monique Labracherie, Richard A. Mortlock, Ernst Maier-Reimer, Philip N. Froelich; A test of (Ge/Si)opal as a paleorecorder of (Ge/Si)seawater. Geology 1998;; 26 (2): 179–182. doi: https://doi.org/10.1130/0091-7613(1998)026<0179:ATOGSO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Late Pleistocene variations of germanium to silicon ratios in marine diatom shells from sediment cores, (Ge/Si)opal, are coherent with the global isotope record of glacial to interglacial climate change. These variations are thought to reflect changes in (Ge/Si)seawater driven by climate-modulated alterations in oceanic Ge/Si sources and sinks. However, an important criterion for interpreting (Ge/Si)opal as a monitor of whole ocean (Ge/Si)seawater is that the opal burial ratio be insensitive both to local diatom production and surface ocean silica concentrations (so-called biological fractionation effects) and to differential dissolution artifacts (so-called diagenesis offsets). Here we test these assumptions by comparing model ocean sediment (Ge/Si)opal distributions with data from Holocene and glacial sediments across the high-latitude Indian-Antarctic Ocean siliceous ooze belt. In contrast to the model, the data show no gradients in either Holocene or glacial (Ge/Si)opal values across productivity zones displaying dramatic changes in biosiliceous production, opal burial, and dissolution. This evidence supports the contention that fractionation effects are small and that observed down-core variations in (Ge/Si)opal faithfully record secular changes in (Ge/Si)seawater. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Quantifying the scale and importance of individual dispersion between populations and life stages is a key challenge in marine ecology. The common sole (Solea solea), an important commercial flatfish in the North Sea, Atlantic Ocean and the Mediterranean Sea, has a marine pelagic larval stage, a benthic juvenile stage in coastal nurseries (lagoons, estuaries or shallow marine areas) and a benthic adult stage in deeper marine waters on the continental shelf. To date, the ecological connectivity among these life stages has been little assessed in the Mediterranean. Here, such an assessment is provided for the first time for the Gulf of Lions, NW Mediterranean, based on a dataset on otolith microchemistry and stable isotopic composition as indicators of the water masses inhabited by individual fish. Specifically, otolith Ba/Ca and Sr/Ca profiles, and δ13C and δ18O values of adults collected in four areas of the Gulf of Lions were compared with those of young-of-the-year collected in different coastal nurseries. Results showed that a high proportion of adults (>46%) were influenced by river inputs during their larval stage. Furthermore Sr/Ca ratios and the otolith length at one year of age revealed that most adults (∼70%) spent their juvenile stage in nurseries with high salinity, whereas the remainder used brackish environments. In total, data were consistent with the use of six nursery types, three with high salinity (marine areas and two types of highly saline lagoons) and three brackish (coastal areas near river mouths, and two types of brackish environments), all of which contributed to the replenishment of adult populations. These finding implicated panmixia in sole population in the Gulf of Lions and claimed for a habitat integrated management of fisheries.
Otolith Sr/Ca, Ba/Ca and 87 Sr/ 86 Sr ratios and vertebral bone histomorphometry were used to investigate the life-history of Anguilla obscura eels from an enclosed lake, Lalolalo (Wallis Island in the Pacific), with no apparent connection with the sea. 87 Sr/ 86 Sr isotopic ratio from the core region gives evidence of indisputable marine origin of eels caught in the lake suggesting that underground connections between the lake and the sea exist. Sr/Ca and Ba/Ca ratios recorded after the elver mark are undifferentiated from seawater ones, thus limiting their used as marker of entrance in the lake and movement. However, 87 Sr/ 86 Sr isotopic ratio demonstrated that: 1) eels enter in the lake just after their metamorphosis and spend their entire adult life in the lake and 2) the lake chemistry is consistent with 1 % seawater-like contribution and 99 % basalt weathering and/or geothermal spring contribution. The vertebrae do not show a particular demineralization of bone matrix (45-52 %). Reversely, the study of bone compactness shows an important loss of bone that favors the hypothesis of a genital maturation that arises in the ecological state of the lake.
