The effects of varying CO2 concentration on lipid composition and carbon isotope fractionation in Emiliania huxleyi.

We have measured the stable carbon isotopic composition of bulk organic matter (POC), alkenones, sterols, fatty acids, and phytol in the coccolithophorid Emiliania huxleyi grown in dilute batch cultures over a wide range of CO2 concentrations (1.1–53.5 μmol L−1). The carbon isotope fractionation of POC (εPOC) varied by ca. 7‰ and was positively correlated with aqueous CO2 concentration [CO2aq]. While this result confirms general trends observed for the same alga grown in nitrogen-limited chemostat cultures, considerable differences were obtained in absolute values of εPOC and in the slope of the relationship of εPOC with growth rate and [CO2aq]. Also, a significantly greater offset was obtained between the δ13C of alkenones and bulk organic matter in this study compared with previous work (5.4, cf. 3.8‰). This suggests that the magnitude of the isotope offset may depend on growth conditions. Relative to POC, individual fatty acids were depleted in 13C by 2.3‰ to 4.1‰, phytol was depleted in 13C by 1.9‰, and the major sterol 24-methylcholesta-5,22E-dien-3β-ol was depleted in 13C by 8.5‰. This large spread of δ13C values for different lipid classes in the same alga indicates the need for caution in organic geochemical studies when assigning different sources to lipids that might have δ13C values differing by just a few ‰. Increases in [CO2aq] led to dramatic increases in the alkenone contents per cell and as a proportion of organic carbon, but there was no systematic effect on values of U37k′ used for reconstructions of paleo sea surface temperature

Preservation effects on the isotopic and elemental composition of skeletal structures in the deep-sea bamboo coral Lepidisis spp. (Isididae)

Trace elements and stable isotopes (δ13C and δ15N) in deep-sea coral have been used as proxies to reconstruct past climate, and to investigate food web structure. However, there is a paucity of information regarding the effect of preservation on the ch

Preservation effects on the isotopic and elemental composition of skeletal structures in the deep-sea bamboo coral Lepidisis spp. (Isididae)

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On-site and in situ remediation technologies applicable to petroleum hydrocarbon contaminated sites in the Antarctic and Arctic

Petroleum hydrocarbon contaminated sites, associated with the contemporary and legacy effects of human activities, remain a serious environmental problem in the Antarctic and Arctic. The management of contaminated sites in these regions is often confounded by the logistical, environmental, legislative and financial challenges associated with operating in polar environments. In response to the need for efficient and safe methods for managing contaminated sites, several technologies have been adapted for on-site or in situ application in these regions. This article reviews six technologies which are currently being adapted or developed for the remediation of petroleum hydrocarbon contaminated sites in the Antarctic and Arctic. Bioremediation, landfarming, biopiles, phytoremediation, electrokinetic remediation and permeable reactive barriers are reviewed and discussed with respect to their advantages, limitations and potential for the long-term management of soil and groundwater contaminated with petroleum hydrocarbons in the Antarctic and Arctic. Although these technologies demonstrate potential for application in the Antarctic and Arctic, their effectiveness is dependent on site-specific factors including terrain, soil moisture and temperature, freeze–thaw processes and the indigenous microbial population. The importance of detailed site assessment prior to on-site or in situ implementation is emphasized, and it is argued that coupling of technologies represents one strategy for effective, long-term management of petroleum hydrocarbon contaminated sites in the Antarctic and Arctic