NERC Open Research Archive

    The SALTMED model calibration and validation using field data from Morocco

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    The objective of this study was to calibrate and validate the SALTMED model using field data of three growing seasons of quinoa (Chenopodium quinoa Willd.), chickpeas (Cicer arietinum) and sweet corn (Zea mays Saccharata) which were grown in the south of Morocco and subjected to six treatments of deficit irrigation with treated wastewater. The calibration focussed primarily on soil moisture related to quinoa in the field, measured yield and dry matter. The validation process of biomass production was based on use of the calibrated photosynthesis efficiency value of the control treatment. Plant parameters such as plant height and rooting depth, duration of each growth stage, sowing date, harvesting date, harvest index and leaf area index were based on field measurements and records. Crop coefficients Kc, Kcb, Fc were based on FAO56 paper. Soil parameters such as water retention curves were based on laboratory measurements. Initial soil water content and salinity were based on measurements either in the laboratory or in the field. Fine tuning of some crop and soil parameters was carried out in order to obtain a good calibration. Following successful calibration and validation, the SALTMED model proved its ability to predict soil moisture, yield and total dry matter for three growing seasons under several deficit irrigation strategies using treated wastewater. The model showed a very good agreement between the observed and simulated data, as well as being able to reveal the same difference between deficit irrigation strategies in terms of measured yield and total dry matter

    Marine invertebrate skeleton size varies with latitude, temperature and carbonate saturation: implications for global change and ocean acidification

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    There is great concern over the future effects of ocean acidification on marine organisms, especially for skeletal calcification, yet little is known of natural variation in skeleton size and composition across the globe, and this is a prerequisite for identifying factors currently controlling skeleton mass and thickness. Here, taxonomically controlled latitudinal variations in shell morphology and composition were investigated in bivalve and gastropod molluscs, brachiopods, and echinoids. Total inorganic content, a proxy for skeletal CaCO3, decreased with latitude, decreasing seawater temperature, and decreasing seawater carbonate saturation state (for CaCO3 as calcite (Ωcal)) in all taxa. Shell mass decreased with latitude in molluscs and shell inorganic content decreased with latitude in buccinid gastropods. Shell thickness decreased with latitude in buccinid gastropods (excepting the Australian temperate buccinid) and echinoids, but not brachiopods and laternulid clams. In the latter, the polar species had the thickest shell. There was no latitudinal trend in shell thickness within brachiopods. The variation in trends in shell thickness by taxon suggests that in some circumstances ecological factors may override latitudinal trends. Latitudinal gradients may produce effects similar to those of future CO2-driven ocean acidification on CaCO3 saturation state. Responses to latitudinal trends in temperature and saturation state may therefore be useful in informing predictions of organism responses to ocean acidification over long-term adaptive timescale

    Environmental geographic basis for the Protected Area System

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    Variations between winter and summer in the toxicity of copper to a population of the mysid Praunus flexuosus

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    Copper toxicity was tested on a coastal population of the mysid Praunus flexuosus (Müller) from Southampton Water (Southern England) under winter and summer conditions. Ten-day toxicity tests were performed on the different life-cycle stages (female, male and juvenile) present in winter (December/February) and summer (August). The individuals were in winter or summer physiological condition and were exposed to seawater to which 0, 5, 25, 75 and 200 μg l−1 copper was added. There were significantly different copper toxicity effects in winter and summer. In winter mortality was ≤ 1% at all levels of copper exposure, while in summer identical exposure levels caused mortality of up to 93%. The 96 h LC50 was 30.8 μg l−1 copper added in the summer. In winter, the low mortality prevented calculation of LC50. There were differences in responses to copper between the life-cycle stages. Juveniles were more sensitive than adults, and were severely affected within 24 h. Females were more affected than males at lower doses and shorter exposure times

    Colonisation vs. disturbance: the effects of sustained ice-scouring on intertidal communities

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    Shoreline plant and animal communities close to a retreating tidewater glacier on the sub-Antarctic island of South Georgia displayed a series of physical and biological gradients from the open sea to the glacier terminus. These included increasing scouring intensity caused by floating and/or grounded ice fragments as well as decreasing diversity and abundance of both macroflora and macrofauna. The correlation between gradients suggests that shoreline scouring intensity can be directly quantified from plant diversity and abundance, and that the colonisation of coastlines exposed to sustained ice-scouring is not stochastic like that following single massive ice-scouring events, but directional like recovery from small scale disturbances. However, colonisation following small-scale disturbance events is much more rapid than that associated with continual scouring. Indeed recovery from continual scouring is so protracted that affected shores are held for a prolonged period at a particular phase of the normal spring annual spring colonisation process by local ice-scouring intensity

    Mixed biosiliceous-terrigenous sedimentation under the Antarctic Circumpolar Current, Scotia Sea

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    Sediment supply to the Scotia Sea is controlled by the east-flowing Antarctic Circumpolar Current (ACC) with some Weddell Gyre influence in the south. Near-bottom flow is unsteady with frequent changes in flow direction and episodic benthic storms. Near the North Scotia Ridge, mounds of sediment up to 1 km thick have accumulated on lower Miocene ocean floor. The basins farther south contain up to 2 km of sediment which is flat-lying or draped rather than mounded. Sediment cores exhibit a biogenic-terrigenous cyclicity related to glacial-interglacial cycles. Grain-size data suggest that ACC flow was stronger during glacials than interglacials

    Changes in heavy metals in Antarctic snow from Coats Land since the mid-19th to the late-20th century

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    V, Cr, Mn, Cu, Zn, Co, Ag, Cd, Ba, Pb, Bi and U have been measured in a series of dated snow samples, covering the period from 1834 to 1990, collected at remote, low accumulation sites in Coats Land, Antarctica. They were determined by ultrasensitive inductively coupled sector field mass spectrometry in ultraclean conditions. Concentrations are found to be extremely low, down to 3 x 10(-15) g/g, for most metals, then confirming the high purity of Antarctic snow. The results show contrasting time trends for the different metals. For Mn, Co, Ba, and possibly V and Cd, no clear time trends are observed. For Cr, Cu, Zn, Ag, Pb, Bi and U, on the other hand, pronounced enhancements are observed during the recent decades. They are attributed to emissions of heavy metals to the atmosphere from human activities in Southern America, Southern Africa and Australia, especially non-ferrous metal mining and smelting in Chile, Peru, Zaire, Zambia and Australia. It shows that atmospheric pollution for heavy metals in the remote Antarctic continent is not limited to Pb and Cu, as previously thought, but also affects several other metals. It is a further indication that atmospheric pollution for heavy metals is really global
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