TEX86 (tetraether index of 86 carbon atoms) is an organic paleotemperatureproxy based on the relative abundances of thaumarcheal isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs). The calibration is based on global core top sediments. The global core top calibrations of TEX86 are often not reliable for reconstructions of watertemperatures in regions with distinct hydrographic conditions. In the area of the continental edge of Newfoundland (Northwest Atlantic), hydrographic conditions are mainly determined by the Labrador- and the North Atlantic Current. Thus, the region differs from the global ocean. In this study the accuracy of temperature estimations of TEX86 was tested at the realm of the continental edge off Newfoundland. For this purpose, GDGT distribution in suspended particulate matter of water surface and core top sediments was analysed. Based on the GDGT composition, the influence of the regional environmental factors on the TEX86 proxy was investigated. Based on TEX-signals of the samples, temperatures were estimated, using various global core top calibrations (for the surface sediments: TEX86, BAYSPAR (for sea surface temperature (SST), for subsurface temperature (SubT0-200 m)), TEX86L, TEX86L0-200 m / for the suspended solids samples: TEX86, BAYSPAR (SST), TEX86L). Using the global core top TEX86-calibration for sedimentary signals, the annual mean (am) SST were estimated. However, due to the large standard error, reliability is uncertain. Statistical analyses show strong relations of the sedimentary TEX86L-values to the mean temperatures of summer season (June, July, August) below the water surface (average temperature of 10 and 15 m water depth). A sedimentary temperature signal of the summer months could be explained by a combination of the maximum abundance of the regional Thaumarchaeota and the iGDGT export by fecal pallets of a local copepod population in the summer season. The temperatures derived from TEX-signals of suspended particulate matter results in an overestimation of the in situ temperature. This could be explained by the iGDGT production of an archaea group, whose membrane lipid adaptation is individual with respect to the growth temperature. The sedimentary iGDGT distribution, however, does not seem to be affected. Based on the findings, a regional calibration could be developed to refine the reconstruction of paleo-water-temperatures at the shelf slopes of Newfoundland. […]

Long chain alkyl diols (LCDs) are lipid biomarkers that occur ubiquitously in sediments. Their abundance and distributions are increasingly used as the basis of molecular proxies for environmental parameters such as sea surface temperature (SST) via the Long chain Diol Index (LDI), and upwelling intensity and nutrient conditions (parametrized as diol indices, DI-2, and Nutrient Diol Index, NDI, respectively). Their marine producers remain the subject of debate, but in cultures, they can be found within the outer wall (algaenan) of eustigmatophytes or in Proboscia diatoms. LCDs appear to be well preserved in sediments, potentially as a result of their association with algaenan and/or minerals, but little is known of their pre-depositional histories, in particular transport dynamics. Here, 15 surface continental margin sediments as well as one high-deposition-rate sediment core (50 cm, spanning the last ~30 years) were analyzed in order to evaluate the impact of organo-mineral associations, lateral transport, and hydrodynamic sorting on sedimentary LCD signals. The abundance and distribution of LCDs in bulk sediments and corresponding grain-size fractions was determined. The highest proportion of all LCD isomers is found in the fine fraction (2 – 10 µm), which also holds the highest proportion of organic matter in relation to the other grain-size fractions. However, LCDs are also found in the other fractions (sand, coarse silt, and clay), and their concentrations are not correlated with bulk organic carbon content, indicating different preservation or transport mechanisms. LDI-SST in the bulk sediment is comparable to the mean annual SST at all sites except those influenced by upwelling and characterized by strong seasonal SST gradients. To the contrary of other biomarker-related proxies (e.g., alkenones), lateral transport does not appear to strongly affect LDI-SST in size fractions, suggesting that the intimate relationship of LCD with the algaenan may counteract the influence of hydrodynamic mineral sorting processes on related proxy signals. The difference between the fraction-weighted LCD concentration and bulk sedimentary LCD concentration indicates potential release of LCD during laboratory fractionation, suggesting degradation of algaenan or dissolution of opal frustules.