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Regional variation in maturation of sandeels in the North Sea 总被引:1,自引:0,他引:1
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The sources of carbon, which fuel water column respiration, remain unresolved for most estuaries; our objective was to examine
carbon dynamics in a shallow subtropical estuary. We sampled the Sabine-Neches estuary, Texas, during low (November 1999)
and high (May 2000) freshwater inflow and measured stable carbon isotope ratios of the dissolved inorganic and orgnaic carbon
(δ13C-DIC, δ13C-DOC), as well as quantifying accessory parameters (salinity, nutrients, total suspended solids, and photosynthetic pigments).
Pigment analysis indicated that diatoms were the predominant phytoplankton. Data from the May 2000 sampling event exhibited
conservative mixing, indicating that the system was acting as a conduit between the watershed and the Gulf of Mexico. During
November, mixing was generally nonconservative indicating extensive recycling of allochthonous and autochthonous carbon sources.
Our data imply that both carbon sources had similar isotope, ratios that made it impossible to unambiguously determine the
dominant source supporting respiration. The nonconservative DIC concentration data indicating an autotrophic sink as well
as the strong relationship between δ13C-DOC and chlorophylla, suggest that in situ production was an important component of the DOC pool. We hypothesize that uncharacteristically calm
wind conditions during sampling may have promoted phytoplankton settling, removing autotrophs, from the water column, but
leaving behind a dissolved biogeochemical signature. Interpretation of carbon dynamics may be confounded by spatial and temporal
decoupling of producers and consumers from biogeochemical indicators. 相似文献
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Natural Hazards - Driving after natural disasters entails a substantial amount of stress; therefore, the number of motor vehicle crashes may increase. However, few studies have examined this issue.... 相似文献
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Richard A. Staff Takeshi Nakagawa Gordon Schlolaut Michael H. Marshall Achim Brauer Henry F. Lamb Christopher Bronk Ramsey Charlotte L. Bryant Fiona Brock Hiroyuki Kitagawa Johannes van der Plicht Rebecca L. Payne Victoria C. Smith Darren F. Mark Alison Macleod Simon P. E. Blockley Jean‐Luc Schwenninger Pavel E. Tarasov Tsuyoshi Haraguchi Katsuya Gotanda Hitoshi Yonenobu Yusuke Yokoyama Suigetsu Project Members 《Boreas: An International Journal of Quaternary Research》2013,42(2):259-266
The varved sediment of Lake Suigetsu (central Japan) provides a valuable opportunity to obtain high‐resolution, multi‐proxy palaeoenvironmental data across the last glacial/interglacial cycle. In order to maximize the potential of this archive, a well‐constrained chronology is required. This paper outlines the multiple geochronological techniques being applied – namely varve counting, radiocarbon dating, tephrochronology (including argon–argon dating) and optically stimulated luminescence (OSL) – and the approaches by which these techniques are being integrated to form a single, coherent, robust chronology. Importantly, we also describe here the linkage of the floating Lake Suigetsu (SG06) varve chronology and the absolute (IntCal09 tree‐ring) time scale, as derived using radiocarbon data from the uppermost (non‐varved) portion of the core. This tie‐point, defined as a distinct (flood) marker horizon in SG06 (event layer B‐07–08 at 1397.4 cm composite depth), is thus derived to be 11 255 to 11 222 IntCal09 cal. years BP (68.2% probability range). 相似文献
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Fiona S. Tweed 《Geology Today》2012,28(6):217-223
Volcanic eruptions generate hazards, are potent agents of landscape change and have the power to alter global climate. Recent events in Iceland have emphasised the multi‐scale and trans‐boundary nature of hazards from ice‐volcano interactions and have highlighted their local, national and international impacts. Prompted by these recent events, this article reviews a selection of Icelandic volcanic eruptions in order to demonstrate the diversity of hazards and impacts generated by Icelandic volcanic activity. Some of the challenges associated with managing risks from Icelandic volcanic hazards are discussed and future prospects are outlined. 相似文献
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Brent B. Wolfe Matthew D. Falcone Ken P. Clogg-Wright Cherie L. Mongeon Yi Yi Bronwyn E. Brock Natalie A. St. Amour William A. Mark Thomas W. D. Edwards 《Journal of Paleolimnology》2007,37(2):221-231
Recent advances in sample preparation techniques and mass spectrometry have fostered more routine oxygen isotope analysis
of aquatic cellulose in lake sediment cores, a proxy for lake water oxygen isotope history. These methodological developments
have significantly increased the feasibility of incorporating this approach into high-resolution, multi-site, and multi-proxy
studies, which are frequently necessary to answer complex hydrological, hydroecological and hydroclimatic questions requiring
a paleoenvironmental perspective. Direct translation of lake sediment aquatic cellulose oxygen isotope composition into lake
water oxygen isotope composition offers appreciable opportunity for quantitative paleohydrological reconstructions, as evidenced
by studies conducted over the past 15 years that span Holocene and pre-historical timescales. 相似文献