Does use of tropical beaches by tourists and island residents result in damage to fringing coral reefs? A case study in Moorea French Polynesia     

Allison Juhasz  Ellen Ho  Erika Bender  Peggy Fong 《Marine pollution bulletin》2010,60(12):2251-2256

Although coral reefs worldwide are subject to increasing global threats, humans also impact coral reefs directly through localized activities such as snorkeling, kayaking and fishing. We investigated five sites on the northern shore of Moorea, French Polynesia, and quantified the number of visitors on the beach and in shallow water. In field surveys, we measured total coral cover and colony sizes of two common genera, Porites and Acropora, a massive and branching morphology, respectively. One site, which hosted over an order of magnitude more people than the other four, had significantly less total coral cover and supported very little branching Acropora. In addition, size frequency distributions of both the branching and massive genera were skewed toward smaller colony sizes at the high use site. Our results demonstrated that the use of tropical beaches may result in less coral cover, with branching colonies rare and small.  相似文献   

Temperature variability over the past millennium inferred from Northwestern Alaska tree rings   总被引：3，自引：0，他引：3  

Rosanne D’Arrigo  Erika Mashig  David Frank  Rob Wilson  Gordon Jacoby 《Climate Dynamics》2005,24(2-3):227-236

We describe a new tree-ring width data set of 14 white spruce chronologies for the Seward Peninsula (SP), Alaska, based on living and subfossil wood dating from 1358 to 2001 AD. A composite chronology derived from these data correlates positively and significantly with summer temperatures at Nome from 1910 to 1970, after which there is some loss of positive temperature response. There is inferred cooling during periods within the Little Ice Age (LIA) from the early to middle 1600s and late 1700s to middle 1800s; and warming from the middle 1600s to early 1700s. We also present a larger composite data set covering 978–2001 AD, utilizing the SP ring-width data in combination with archaeological wood measurements and other recent collections from northwestern Alaska. The Regional Curve Standardization (RCS) method was employed to maximize potential low-frequency information in this data set. The RCS chronology shows intervals of persistent above-average growth around the time of the Medieval Warm Period (MWP) early in the millennium, which are comparable to growth levels in recent centuries. There is a more sustained cold interval during the LIA inferred from the RCS record as compared to the SP ring-width series. The chronologies correlate significantly with Bering and Chukchi Sea sea surface temperatures and with the Pacific Decadal Oscillation index. These atmosphere–ocean linkages probably account for the differences between these records and large-scale reconstructions of Arctic and Northern Hemisphere temperatures based largely on continental interior proxy data.  相似文献   

Ecological response to hurricane events in the Pamlico Sound system, North Carolina, and implications for assessment and management in a regime of increased frequency   总被引：1，自引：0，他引：1  

Hans W. Paerl  Lexia M. Valdes  Alan R. Joyner  Benjamin L. Peierls  Michael F. Piehler  Stanley R. Riggs  Robert R. Christian  Lisa A. Eby  Larry B. Crowder  Joseph S. Ramus  Erika J. Clesceri  Christopher P. Buzzelli  Richard A. Luettich 《Estuaries and Coasts》2006,29(6):1033-1045

Since the mid 1990s, the Atlantic and Gulf Coast regions have experienced a dramatic increase in the number of hurricane landfalls. In eastern North Carolina alone, eight hurricances have affected the coast in the past 9 years. These storms have exhibited individualistic hydrologic, nutrient, and sediment loading effects and represent a formidable challenge to nutrient management aimed at reducing eutrophication in the Pamlico Sound and its estuarine tributaries. Different rainfall amounts among hurricanes lead to variable freshwater and nutrient discharge and variable nutrient, organic matter, and sediment enrichment. These enrichments differentially affected physical and chemical properties (salinity, water residence time, transparency, stratification, dissolved oxygen), phytoplankton primary production, and phytoplankton community composition. Contrasting ecological responses were accompanied, by changes in nutrient and oxygen cycling, habitat, and higher trophic levels, including different direct effects on fish populations. Floodwaters from the two largest hurricances, Fran (1996) and Floyd (1999), exerted, multi-month to multi-annual effects on hydrology, nutrient loads, productivity, and biotic composition. Relatively low rainfall coastal hurricanes like Isabel (2003) and Ophelia (2005) caused strong vertical mixing and storm surges, but relatively minor hydrologic and nutrient effects. Both hydrologic loading and wind forcing are important drivers and must be integrated with nutrient loading in assessing short-term and long-term ecological effects of these storms. These climatic forcings cannot be managed but should be considered in the development of water quality management strategies for these and other large estuarine ecosystems faced with increasing frequencies and intensities of hurricane activity.  相似文献   

Origin of sulfur species in acid sulfate-chloride thermal waters,northeastern Japan     

Yasuhiro Kiyosu  Makoto Kurahashi 《Geochimica et cosmochimica acta》1983,47(7):1237-1245

Acid sulfate-chloride thermal water samples collected together with fumarolic gases from various volcanic areas in northeastern Japan were studied chemically and isotogdically. δ³⁴S (COT) values of sulfate and hydrogen sulfide from these volcanic hot springs range from +4.0 to +31 and from ?15.0 to ?2.0% respectively, with δ³⁴S_ys value of +2.5 to +31. The δ³⁴S of the sulfate in the more saline waters tends to become smaller with increasing ratio of SO₄ to Cl, although the chemical and isotopic composition of acid thermal water within some areas may be altered by secondary processes during the discharge of the thermal waters. This trend can be explained by the reaction of the volcanic gases, having S/Cl of 4 ~ 7 and total sulfur of ~0% in δ³⁴S, with ground water at 200°C, and/or the removal of sulfide phase depleted in ³⁴S from the acid thermal water formed by the disproportionation of volcanic sulfur. The sulfur species in acid sulfate-chloride thermal water are shown to be volcanic exhalations.  相似文献   

Functional attributes of epilithic diatoms for palaeoenvironmental interpretations in South-West Greenland lakes     

Suzanne McGowan  Hazel V. Gunn  Erika J. Whiteford  N. John Anderson  Vivienne J. Jones  Antonia C. Law 《Journal of Paleolimnology》2018,60(2):273-298

Benthic diatoms are commonly used for palaeoenvironmental reconstruction in Arctic regions, but interpretation of their ecology remains challenging. We studied epilithic diatom assemblages from the shallow margins of 19 lakes from three areas (coast-inland-ice sheet margin) along a climate gradient in Kangerlussuaq, West Greenland during two periods; shortly after ice-off (spring) and in the middle of the growth season (summer). We aimed to understand the distribution of Arctic epilithic diatoms in relation to water chemistry gradients during the two seasons, to investigate their incorporation into lake sediments and to assess their applicability as palaeoenvironmental indicators. Diatoms were correlated with nutrients in the spring and alkalinity/major ions in the summer, when nutrients were depleted; approximately half of the variance explained was independent of spatial factors. When categorised by functional attributes, diatom seasonal succession differed among regions with the most obvious changes in inland lakes where summer temperatures are warmer, organic nutrient processing is prevalent and silicate is limiting. These conditions led to small, motile and adnate diatoms being abundant in inland lakes during the summer (Nitzschia spp., Encyonopsis microcephala), as these functional attributes are suited to living within complex mats of non-siliceous microbial biofilms. Seasonal succession in silica-rich lakes at the coast was less pronounced and assemblages included Tabellaria flocculosa (indicating more acidic conditions) and Hannaea arcus (indicating input from inflowing rivers). The nitrogen-fixing diatom Epithemia sorex increased from the coast to the ice sheet, negatively correlating with a gradient of reactive nitrogen. The presence of this diatom in Holocene sediment records alongside cyanobacterial carotenoids during arid periods of low nitrogen delivery, suggests that it is a useful indicator of nitrogen limitation. Nitzschia species appear to be associated with high concentrations of organic carbon and heterotrophy, but their poor representation in West Greenland lake sediments due to taphonomic processes limits their palaeoenvironmental application in this region. Proportions of epilithic taxa in lake sediment records of coastal lakes increased during some wetter periods of the Holocene, suggesting that snowpack-derived nutrient delivery may offer diatom taxa living at lake margins a competitive advantage over planktonic diatoms during the “moating” ice melt period. Thus, further research investigating linkages between epilithic diatoms, snowpack and nutrient delivery in seasonally frozen lakes is recommended as these taxa live on the ‘front-line’ during the spring and may be especially sensitive to changes in snowmelt conditions.  相似文献   

Interannual variability associated with ENSO: present and future climate projections of RegCM4 for South America-CORDEX domain     

Rosmeri Porfírio da Rocha  Michelle Simões Reboita  Lívia Márcia Mosso Dutra  Marta Pereira Llopart  Erika Coppola 《Climatic change》2014,125(1):95-109

Interannual variability over South America (SA) is mainly controlled by the El Niño-Southern Oscillation (ENSO) phenomenon. This study investigates the ENSO precipitation signal during austral spring (September–October–November-SON) over SA. Three global circulation models-GCMs-(MPI, GFDL and HadGEM2) are used for RegCM4 (Regional Climate Model version 4) downscaling of the present (1975–2005) near-future (2020–2050) and far-future (2070–2098) climates using two greenhouse gas stabilization scenarios (RCP4.5 and RCP8.5). For the present climate, only HadGEM2 simulates a frequency of El Niño (EN) and La Niña (LN) years similar to the observations. In terms of ENSO frequency changes, only in the far-future RCP8.5 climate there is greater agreement among GCMs, indicating an increase (decrease) of EN (LN) years. In the present climate, validation indicates that only the RegCM4 ensemble mean provides acceptable precipitation biases (smaller than ±20 %) in the two investigated regions. In this period, the GCMs and RegCM4 agree on the relationship between ENSO and precipitation in SA, i.e., both are able to capture the observed regions of positive/negative rainfall anomalies during EN years, with RegCM4 improving on the GCMs’ signal over southeastern SA. For the near and far future climates, in general, the projections indicate an increase (decrease) of precipitation over southeastern SA (northern-northeastern SA). However, the relationship between ENSO and rainfall in most of RegCM4 and GCM members is weaker in the near and far future climates than in the present day climate. This is likely connected with the GCMs’ projection of the more intense ENSO signal displaced to the central basin of Pacific Ocean in the far future compared to present climate.  相似文献   

Calibrating Environment Canada's MESH Modelling System over the Great Lakes Basin     

Amin Haghnegahdar  Bryan A. Tolson  Bruce Davison  Frank R. Seglenieks  Erika Klyszejko  Eric D. Soulis 《大气与海洋》2014,52(4):281-293

This paper reports on recent progress towards improved predictions of a land surface-hydrological modelling system, Modélisation Environmentale–Surface et Hydrologie (MESH), via its calibration over the Laurentian Great Lakes Basin. Accordingly, a “global” calibration strategy is utilized in which parameters for all land class types are calibrated simultaneously to a number of sub-basins and then validated in time and space. Model performance was evaluated based on four performance metrics, including the Nash-Sutcliffe (NS) coefficient and simulated compared with observed hydrographs. Results from two calibration approaches indicate that in the model validation mode, the global strategy generates better results than an alternative calibration strategy, referred to as the “individual” strategy, in which parameters are calibrated individually to a single sub-basin with a dominant land type and then validated in a different sub-basin with the same dominant land type. The global calibration strategy was relatively successful despite the large number of calibration parameters (51) and relatively small number of model evaluations (1000) used in the automatic calibration procedure. The NS values for spatial validation range from 0.10 to 0.72 with a median of 0.41 for the 15 sub-basins considered. Results also confirm that a careful model calibration and validation is needed before any application of the model.  相似文献   

Fission track thermochronology of the Beni Bousera peridotite massif (Internal Rif,Morocco) and the exhumation of ultramafic rocks in the Gibraltar Arc     

Ali Azdimousa  Jacques Bourgois  Gérard Poupeau  Mercedes Vázquez  Lahcen Asebriy  Erika Labrin 《Arabian Journal of Geosciences》2014,7(5):1993-2005

The Beni Bousera peridotite massif and its metamorphic surrounding rocks have been analyzed by the fission track (FT) method. The aim was to determine the cooling and uplift history of these mantle and associated crustal rocks after the last major metamorphic event that dates back to the Lower Miocene–Upper Oligocene time (～22–24 Ma). The zircon FT analyses give an average cooling—i.e., below 320 °C—age of ～19.5 Ma. In addition, the apatite FT data give an average cooling—i.e., below 110 °C—age of ～15.5 Ma. Taking into account the thermal properties of the different thermochronological systems used in this work, we have estimated a rate of cooling close to 50 °C/Ma. This cooling rate constrains a denudation rate of about ～2 mm year^?1 from 20 to 15 Ma. These results are similar to those determined in the Ronda peridotite massif of the Betic Cordilleras documenting that some ultrabasic massifs of the internal zones of the two segments of the Gibraltar Arc have a similar evolution. However, Burdigalian sediments occur along the Betic segment (Alozaina area, western Betic segment) unconformably overlying peridotite. At this site, ultramafic rock was exposed to weathering at ages ranging from 20.43 to 15.97 Ma. Since the Beni Bousera peridotite was still at depth until 15.5 Ma, we infer that no simple age projection from massif to massif is possible along the Gibraltar Arc. Moreover, the confined fission track lengths data reveal that a light warming (～100 °C) has reheated the massif during the Late Miocene before the Pliocene–Quaternary tectonic uplift.  相似文献