A Simple Index of Trophic Status in Estuaries and Coastal Bays Based on Measurements of pH and Dissolved Oxygen     

Shane O’Boyle  Georgina McDermott  Tone Noklegaard  Robert Wilkes 《Estuaries and Coasts》2013,36(1):158-173

Measurements of pH and dissolved oxygen saturation in summer from 90 Irish estuaries and coastal bays were used to develop a simple index of trophic state. The index is based on the assumption that large fluctuations in both these variables are likely to be a characteristic feature of eutrophication. In this paper, we use a simple index to capture the relative variation in both pH and dissolved oxygen saturation in each water body during a period of 3 years. We show that the index is in good agreement with other trophic status schemes and strongly correlated with parameters indicative of trophic state such as chlorophyll a and biochemical oxygen demand. We conclude that the index could be used as a simple screening tool to group individual water bodies into broad categories that reflect their trophic state.  相似文献   

Very high-frequency and seasonal cave atmosphere P_CO2 variability: Implications for stalagmite growth and oxygen isotope-based paleoclimate records     

James U.L. Baldini  Frank McDermott  Dirk L. Hoffmann  David A. Richards  Nicholas Clipson 《Earth and Planetary Science Letters》2008,272(1-2):118-129

Cave air P_CO2 at two Irish sites varied dramatically on daily to seasonal timescales, potentially affecting the timing of calcite deposition and consequently climate proxy records derived from stalagmites collected at the same sites. Temperature-dependent biochemical processes in the soil control CO₂ production, resulting in high summer P_CO2 values and low winter values at both sites. Large Large-amplitude, high-frequency variations superimposed on this seasonal cycle reflect cave air circulation. Here we model stalagmite growth rates, which are controlled partly by CO₂ degassing rates from drip water, by considering both the seasonal and high-frequency cave air P_CO2 variations. Modeled hourly growth rates for stalagmite CC-Bil from Crag Cave in SW Ireland reach maxima in late December (0.063 μm h^− 1) and minima in late June/early July (0.033 μm h^− 1). For well-mixed ‘diffuse flow’ cave drips such as those that feed CC-Bil, high summer cave air P_CO2 depresses summer calcite deposition, while low winter P_CO2 promotes degassing and enhances deposition rates. In stalagmites fed by well-mixed drips lacking seasonal variations in δ¹⁸O, integrated annual stalagmite calcite δ¹⁸O is unaffected; however, seasonality in cave air P_CO2 may influence non-conservative geochemical climate proxies (e.g., δ¹³C, Sr/Ca). Stalagmites fed by ‘seasonal’ drips whose hydrochemical properties vary in response to seasonality may have higher growth rates in summer because soil air P_CO2 may increase relative to cave air P_CO2 due to higher soil temperatures. This in turn may bias stalagmite calcite δ¹⁸O records towards isotopically heavier summer drip water δ¹⁸O values, resulting in elevated calcite δ¹⁸O values compared to the ‘equilibrium’ values predicted by calcite–water isotope fractionation equations. Interpretations of stalagmite-based paleoclimate proxies should therefore consider the consequences of cave air P_CO2 variability and the resulting intra-annual variability in calcite deposition rates.  相似文献   

A nonlinear elastic approach to modelling the hydro-mechanical behaviour of the SEALEX experiments on compacted MX-80 bentonite     

A. P. Fraser Harris  C. I. McDermott  A. E. Bond  K. Thatcher  S. Norris 《Environmental Earth Sciences》2016,75(22):1445

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Artificial Marine Micro‐Reserves Networks (AMMRNs): an innovative approach to conserve marine littoral biodiversity and protect endangered species          下载免费PDF全文

José C. García‐Gómez  José M. Guerra‐García  Free Espinosa  Manuel J. Maestre  Georgina Rivera‐Ingraham  Darren Fa  Alexander R. González  Aurora Ruiz‐Tabares  Carlos M. López‐Fé 《Marine Ecology》2015,36(3):259-277

Coastal engineering works, especially the outer breakwaters of ports where environmental conditions are usually good, often constitute new habitats for marine littoral species. Their potential indirect contribution to the regeneration and conservation of protected species opens up a new perspective in protection of marine biodiversity. This is particularly true when these works harbour, as we show here, important reproductive populations of species that are threatened or even in danger of extinction. We provide integrated data on protected marine species in Southern Iberia established on different substrata (quarried dolomitic rocks, concrete cubic blocks, concrete tetrapods and vertical concrete walls) that are used in the construction of artificial levees that could potentially be Artificial Marine Micro‐Reserves (AMMRs). We also present the first evidence of the ‘reserve effect’ in potential AMMRs and we discuss the need for the creation of AMMRs including their effective networking (AMMRNs), supporting data for which has been observed by studying coastal facilities subjected to strict access restrictions (for security reasons, not conservation). These facilities have acted as valuable proxies and, in reality, potentially act as AMMRs, as well as having a role in helping to detect and control invasive species. We discuss the ecological engineering aspects related to the design and type of materials used in coastal constructions with a view to aiding the integration of these into existing coastal ecosystems as well as promoting greater settlement of species and therefore increases in biodiversity. Finally, the environmental implications of AMMRNs within the future implementation strategy of the Water Framework Directive 2000/60 EC are also discussed.  相似文献   

Application of the geomechanical facies approach and comparison of exploration and evaluation methods used at Soultz-sous-Forêts (France) and Spa Urach (Germany) geothermal sites   总被引：1，自引：1，他引：0  

Helmut Tenzer  Chan-Hee Park  Olaf Kolditz  Christopher Ian McDermott 《Environmental Earth Sciences》2010,61(4):853-880

Earth-reservoirs are increasingly exploited today with the extraction of resources, such as heat and hydrocarbons, and the large-scale emplacement of waste, such as CO₂ sequestration. The characterization, site investigation, predictive modeling and long-term monitoring are dependent on the processes being investigated and modeled. In most cases complex coupled processes have to be addressed in a geologically complex rock mass system. In this paper we present a conceptual holistic framework known as geomechanical facies linking all the scales of investigation, characterization and reservoir development methods. We demonstrate this concept on the work undertaken during the design and development of the enhanced geothermal systems (EGS) systems at the forefront of European Hot-Dry-Rock (HDR) technology, Soultz-sous-Forêts (France) and Spa Urach (Germany). Soultz-sous-Forêts is situated within granitic rocks and an active tectonic graben system in the central part of the Rhine Graben. It presents conditions of lithology, temperature, stress, hydraulics and geochemistry that are very different from those at Spa Urach, located in a very dense gneiss formation in the South German crystalline complex. Spa Urach exhibits more elastic behavior and is set tectonically within an almost inactive strike-slip stress field described in more detail in Sects. “Drill core analysis” and “Hydraulic stimulation at Spa Urach”. This paper compares the exploration and field development methods used at these two sites against the back drop of the geomechanical facies concept. Issues addressed include the key parameters for flow and heat transport properties, coupled hydro-mechanical process identification, the success of the HDR reservoir as a heat exchanger and exploration techniques applicable to the different facies. Identification of the key geomechanical facies gives an indication as to which technologies will prove more efficient in the application of HDR technology. The results of this study will hopefully help in developing heat recovery schemes for the long-term economical operation of future HDR plants and EGS as well as assist in the understanding of engineered geosystems.  相似文献   

Development and application of a CAD interface for fractured rock   总被引：2，自引：0，他引：2  

Thomas Kalbacher  Wenqing Wang  Chris McDermott  Olaf Kolditz  Takeo Taniguchi 《Environmental Geology》2005,47(7):1017-1027

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Geochemical constraints on crustal anatexis: a case study from the Pan-African Damara granitoids of Namibia     

F. McDermott  N. B. W. Harris  C. J. Hawkesworth 《Contributions to Mineralogy and Petrology》1996,123(4):406-423

 Major and trace element models of recently published vapour-absent mica dehydration melting experiments are used to identify granitoids generated by muscovite and biotite dehydration melting, and to distinguish between plagioclase-limited and biotite-limited, biotite dehydration melting. In the case of granitoids from the Pan-African Damara mobile belt (Namibia), many of the leucogranites and Salem-type granitoids may be modelled by biotite dehydration melting. The low Rb/Sr granitoids (e.g. Donkerhuk Onanis, Salem Onanis, Donkerhuk Nomatsaus, Salem Goas) probably reflect feldspar-limited, biotite dehydration melting (a pelitic source) whereas the high Rb/Sr suites (e.g. Bloedkoppie leucogranite, Stinkbank leucogranite, Salem Swakopmund, Leucocratic Stink bank granite) reflect biotite-limited, biotite dehydration melting (a greywacke source). Alaskites from the Damara belt have major element compositions which are consistent with muscovite dehydration melting, and their positive Eu anomalies are linked to high K₂O reflecting K-feldspar entrainment. Combined Zr and LREE (light rare earth element) solubility models indicate that insufficient time (probably less than 10⁴ years) had elapsed between melt generation and melt extraction to ensure that the alaskite melts attained their equilibrium concentrations of Zr and the LREEs. In contrast, the leucogranites and Salem-type granites have attained their equilibrium inventories of these trace elements. Combined Fe₂O₃ and MgO contents in some samples from two granitoids (the Salem Goas and Donkerhuk Onanis intrusions) are higher than those readily attainable by biotite dehydration melting indicating either: (1) that they contain a contribution from melts generated by incipient garnet breakdown or; (2) that they contain small amounts of an entrained ferromagnesian phase. Received: 24 April 1995/Accepted: 11 December 1995  相似文献   

Archival explorations of climate variability and social vulnerability in colonial Mexico     

Georgina H. Endfield 《Climatic change》2007,83(1-2):9-38

In this paper, unpublished archival documentary sources are used to explore the vulnerability to–and implications of–climatic variability and extreme weather events in colonial Mexico. Attention focuses on three regions covering a variety of environmental, social, economic, and political contexts and histories and located at key points along a north-south rainfall gradient: Chihuahua in the arid north, Oaxaca in the wetter south and Guanajuato located in the central Mexican highlands. A number of themes are considered. First, the significance of successive, prolonged, or combined climate events as triggers of agrarian crisis. Second, a case study demonstrating the national and regional impacts of a particularly devastating climate induced famine, culminating with the so-called ‘Year of Hunger’ between 1785 and 1786, is presented. The way in which social networks and community engagement were rallied as a means of fortifying social resilience to this and other crises will be highlighted. Third, the impacts of selected historical flood events are explored in order to highlight how the degree of impact of a flood was a function of public expectation, preparedness and also the particular socio-economic and environmental context in which the event took place. An overview of the spatial and temporal variations in vulnerability and resilience to climatic variability and extreme weather events in colonial Mexico is then provided, considering those recorded events that could potentially relate to broader scale, possibly global, climate changes.  相似文献   

Spatial variability of phytoplankton, nutrients and new production estimates in the waters around Svalbard   总被引：3，自引：0，他引：3  

Georgina Owrid  Giorgio Socal  Giuseppe Civitarese  Anna Luchetta  Jozef Wiktor  Eva-Maria Nöthig  Inger Andreassen  Ursula Schauer  Volker Strass 《Polar research》2000,19(2):155-171

Phytoplankton dynamics and carbon input into Arctic and sub-Arctic ecosystems were investigated around Svalbard, in summer 1991. Phytoplankton biomass, species composition and dissolved nutrient concentrations were analysed from water samples collected along seven transects. Phytoplankton biomass was low especially to the north (Chlorophyll-a mean 0.3 pg 1- '), where flagellates dominated the communities and only ice-diatoms were present. To the west, the phytoplankton composition was representative of a summer Atlantic community, in a post-bloom state. Zooplankton grazing, mainly by copepods, appeared to be the main control on biomass to the west and north of Svalbard.
In the Barents Sea (east of Svalbard), an ice edge bloom was observed (Chlorophyll-a max. 6.8 pgl-') and the ice edge receded at a rate of approximately 1 1 km day-'. The phytoplankton community was represented by marginal ice species, especially Phaeocystis poucherii and Chaeroceros socialis. South of the ice edge, Deep Chlorophyll Maxima (DCM) were observed, as surface waters became progressively nutrient-depleted. In these surface waters, the phytoplankton were predominantly auto- and heterotrophic flagellates.
Carbon production measurements revealed high net production (new and regenerated) to the north of the Barents Sea Polar Front (BSPF); it was especially high at the receding ice edge (reaching 1.44gC m-'day-'). To the south, a low level of production was maintained, mainly through regenerative processes.  相似文献   

Application of hybrid numerical and analytical solutions for the simulation of coupled thermal,hydraulic, mechanical and chemical processes during fluid flow through a fractured rock     

Christopher McDermott  Alexander Bond  Andrew Fraser Harris  Neil Chittenden  Kate Thatcher 《Environmental Earth Sciences》2015,74(12):7837-7854

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