Multiple Factors driving Variability of CO2 Exchange Between the Ocean and Atmosphere in a Tropical Coral Reef Environment     

Rachel F. S. Massaro  Eric Heinen De Carlo  Patrick S. Drupp  Fred T. Mackenzie  Stacy Maenner Jones  Katie E. Shamberger  Christopher L. Sabine  Richard A. Feely 《Aquatic Geochemistry》2012,18(4):357-386

In this paper, we present the results of the first automated continuous multi-year high temporal frequency study of CO₂ dynamics in a coastal coral reef ecosystem. The data cover 2.5?years of nearly continuous operation of the CRIMP-CO₂ buoy spanning particularly wet and dry seasons in southern Kaneohe Bay, a semi-enclosed tropical coral reef ecosystem in Hawaii. We interpret our observational results in the context of how rapidly changing physical and biogeochemical conditions affect the pCO₂ of surface waters and the magnitude and direction of air–sea exchange of CO₂. Local climatic forcing strongly affects the biogeochemistry, water column properties, and gas exchange between the ocean and atmosphere in Kaneohe Bay. Rainfall driven by trade winds and other localized storms generates pulses of nutrient-rich water, which exert a strong control on primary productivity and impact carbon cycling in the water column of the bay. The “La Ni?a” winter of 2005–2006 was one of the wettest winters in Hawaii in 30?years and contrasted sharply with preceding and subsequent drier winter seasons. In addition, short-term variability in physical forcing adds complexity and helps drive the response of the CO₂–carbonic acid system of the bay. Freshwater pulses to Kaneohe Bay provide nutrient subsidies to bay waters, relieving the normal nitrogen limitation of this system and driving phytoplankton productivity. Seawater pCO₂ responds to the blooms as well as to physical forcing mechanisms, leading to a relatively wide range of pCO₂ in seawater from about 250 to 650?μatm, depending on conditions. Large drawdowns in pCO₂ following storms occasionally cause bay waters to switch from being a source of CO₂ to the atmosphere to being a sink. Yet, during our study period, the southern sector of Kaneohe Bay remained a net source of CO₂ to the atmosphere on an annualized basis. The integrated net annual flux of CO₂ from the bay to the atmosphere varied between years by a factor of more than two and was lower during the wet “La Ni?a” year, than during the following year. Over the study period, the net annualized flux was 1.80?mol?C?m^?2?year^?1. Our CO₂ flux estimates are consistent with prior synoptic work in Kaneohe Bay and with estimates in other tropical coral reef ecosystems studied to date. The high degree of climatological, physical, and biogeochemical variability observed in this study suggests that automated high-frequency observations are needed to capture the short-, intermediate-, and long-term variability of CO₂ and other properties of these highly dynamic coastal coral reef ecosystems.  相似文献   

Cro‐Magnon: How the Ice Age Gave Birth to the First Modern Humans. Brian Fagan (Ed.). 2011. Bloomsbury Press,New York. 320 pp., ISBN 978‐1‐608‐19405‐6, $18 (paper).     

Fiona Coward 《Geoarchaeology》2012,27(6):540-542

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The Aspen–Amsterdam void finder comparison project     

Jörg M. Colberg  Frazer Pearce  Caroline Foster  Erwin Platen  Riccardo Brunino  Mark Neyrinck  Spyros Basilakos  Anthony Fairall  Hume Feldman  Stefan Gottlöber  Oliver Hahn  Fiona Hoyle  Volker Müller  Lorne Nelson  Manolis Plionis  Cristiano Porciani  Sergei Shandarin  Michael S. Vogeley  Rien van de Weygaert 《Monthly notices of the Royal Astronomical Society》2008,387(2):933-944

Despite a history that dates back at least a quarter of a century, studies of voids in the large-scale structure of the Universe are bedevilled by a major problem: there exist a large number of quite different void-finding algorithms, a fact that has so far got in the way of groups comparing their results without worrying about whether such a comparison in fact makes sense. Because of the recent increased interest in voids, both in very large galaxy surveys and in detailed simulations of cosmic structure formation, this situation is very unfortunate. We here present the first systematic comparison study of 13 different void finders constructed using particles, haloes, and semi-analytical model galaxies extracted from a subvolume of the Millennium simulation. This study includes many groups that have studied voids over the past decade. We show their results and discuss their differences and agreements. As it turns out, the basic results of the various methods agree very well with each other in that they all locate a major void near the centre of our volume. Voids have very underdense centres, reaching below 10 per cent of the mean cosmic density. In addition, those void finders that allow for void galaxies show that those galaxies follow similar trends. For example, the overdensity of void galaxies brighter than   m _B =−20  is found to be smaller than about −0.8 by all our void finding algorithms.  相似文献   

Limnology of nine Westland beech forest lakes     

H. W. Paerl  G. W. Payne  A. L. Mackenzie  P. E. Kellar  M. T. Downes 《新西兰海洋与淡水研究杂志》2013,47(1):47-57

Lakes in the beech (Nothofagus sp.) forest foothills between Greymouth and Hokitika, Westland, are characterised by amber‐coloured waters. Microbiological, biochemical, and chemical analyses of samples from nine such lakes during March 1976 indicate that they are unproductive. Microbial biomass was intensively investigated in heavily stained Lakes Haupiri and Lady and in least‐stained Lake Brunner. A combination of adenosine triphosphate assays, Utermöhl phytoplankton counts, and autoradiographic biomass determinations revealed a greater bacterial than algal biomass in heavily stained lakes, a highly unusual phenomenon which suggests that most of the production of organic matter was allochthonous. Autochthonous productivity was low, probably because biologically available phosphorus was very scarce and because discoloration reduced the transparency of the water. Hypqlimnetic oxygen depletion was slight during this period of maximum thermal stratification; decomposition of organic matter was apparently incomplete. Reactive phosphorus did not increase appreciably in partially deoxygenated hypolimnia. Much of the allochthonous organic matter originating from beech forests and their soils may be partially resistant to biodegradation.  相似文献   

Climate change policy and practice in regional New Zealand: How are actors negotiating science and policy?     

Alison Greenaway  Fiona Carswell 《New Zealand geographer》2009,65(2):107-117

Regional governance to address climate change is being constituted in New Zealand through domestic policy measures and international discourses. We examine climate change responses in two regions: Marlborough and Waikato. Informants expressed a desire for more transparent government policy; that planning for climate change makes good business sense for farmers and other businesses; that technology is sought to increase productivity and decrease environmental impact; and research networks build capacity for local action, linking sectors and organisations. Often conflicting, these responses to climate change were informed by a mix of discourses shaping New Zealand, including participatory democracy, the knowledge economy and sustainable development.  相似文献   

Constraints on the average magnetic field strength of relic radio sources 0917+75 and 1401−33 from XMM–Newton observations     

C. M. Hubert Chen  D. E. Harris  Fiona A. Harrison  Peter H. Mao † 《Monthly notices of the Royal Astronomical Society》2008,383(3):1259-1268

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Impact history of the Apollo 17 landing site revealed by U‐Pb SIMS ages          下载免费PDF全文

Fiona Thiessen  Alexander A. Nemchin  Joshua F. Snape  Martin J. Whitehouse  Jeremy J. Bellucci 《Meteoritics & planetary science》2017,52(4):584-611

Secondary ion mass spectrometry (SIMS) U‐Pb ages of Ca‐phosphates from four texturally distinct breccia samples (72255, 76055, 76015, 76215) collected at the Apollo 17 landing site were obtained in an attempt to identify whether they represent a single or several impact event(s). The determined ages, combined with inferences from petrologic relationships, may indicate two or possibly three different impact events at 3920 ± 3 Ma, 3922 ± 5 Ma, and 3930 ± 5 Ma (all errors 2σ). Searching for possible sources of the breccias by calculating the continuous ejecta radii of impact basins and large craters as well as their expected ejecta thicknesses, we conclude that Nectaris, Crisium, Serenitatis, and Imbrium are likely candidates. If the previous interpretation that the micropoikilitic breccias collected at the North Massif represent Serenitatis ejecta is correct, then the average ²⁰⁷Pb/²⁰⁶Pb age of 3930 ± 5 Ma (2σ) dates the formation of the Serenitatis basin. The occurrence of zircon in the breccias sampled at the South Massif, which contain Ca‐phosphates yielding an age of 3922 ± 5 Ma (2σ), may indicate that the breccia originated from within the Procellarum KREEP terrane (PKT) and the Imbrium basin appears to be the only basin that could have sourced them. However, this interpretation implies that all basins suggested to fall stratigraphically between Serenitatis and Imbrium formed within a short (<11 Ma) time interval, highlighting serious contradictions between global stratigraphic constraints, sample interpretation, and chronological data. Alternatively, the slightly older age of the two micropoikilitic breccias may be a result of incomplete resetting of the U‐Pb system preserved in some phosphate grains. Based on the currently available data set this possibility cannot be excluded.  相似文献   

Preface     

Fred T. Mackenzie 《Aquatic Geochemistry》1998,4(3-4):299-300

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Crustal structure above the Iceland mantle plume imaged by the ICEMELT refraction profile   总被引：2，自引：0，他引：2  

Fiona A. Darbyshire  Ingi Th. Bjarnason  Robert S. White  & Ólafur G. Flóvenz 《Geophysical Journal International》1998,135(3):1131-1149

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Crabs,leeches and trypanosomes: an unholy trinity?     

Hemmingsen W  Jansen PA  Mackenzie K 《Marine pollution bulletin》2005,50(3):336-339

The red king crab Paralithodes camtschaticus was deliberately introduced to the Barents Sea in the 1960s and 1970s from its native area in the North Pacific. The carapace of these crabs is a favoured substrate for the leech Johanssonia arctica to deposit its eggs, and the leech is a vector for a trypanosome blood parasite of marine fish, including cod. We examined cod for trypanosome infections during annual cruises along the coast of Finnmark in North Norway over three successive years from stations along a gradient of over 1000 km. In every year the level of trypanosome infection in cod was significantly highest in the area with the greatest density of king crabs. We propose the hypothesis that the burgeoning population of red king crabs in this area is indirectly responsible for increased transmission of trypanosomes to cod by promoting an increase in the population of the leech vector.  相似文献