Early diagenesis of lipid biomarker compounds in North Atlantic sediments

Abstract

Near‐surface sediments (0–45 mm depth interval) from the Iceland Basin (59°N, 21°W, 3070‐m water depth) and Biscay Abyssal Plain (48°N, 17°W, 4105‐m water depth) were sectioned at millimeter‐scale resolution to assess alterations in key lipid biomarkers during early diagenesis. Inventories (µg cm−2 in the topmost 45 mm) of biomarkers from presumed terrestrial sources (>C20 linear n‐alkanes, n‐alkanoic acids, n‐alkanols) and from phytoplankton sources (phytosterols, long‐chain alkenones and alkenoates) were 1.5–4 times more abundant in the Iceland Basin core than in the Biscay Abyssal Plain core, indicating greater sedimentary inputs and/or preservation at the Iceland Basin site. Biomarker concentrations varied significantly over millimeter‐scale depth intervals. Pronounced subsurface concentration maxima were present at both sites. At the Biscay Abyssal Plain site, steep concentration gradients in the uppermost few mm of the sediment column indicate extensive diagenetic losses at or near the sediment/water interface. Strong covariance was seen in the concentrations of various compounds within each class (e.g., long‐chain n‐alkanes, n‐alkanols, n‐alkanoic acids and long‐chain alkenones and alkyl alkenoates), indicating that individual compounds within each class are associated with the same organic matrix and have similar degradation and mixing rates. Thus biomarker indices for assessment of land‐derived inputs (CPI, C29/C31, ACL) and sea surface temperature (IPT) remain largely unaltered by early diagenetic processes in oxic, abyssal sediments in spite of extensive bioturbation and degradative losses within the uppermost few centimeters of the sediment column.

Assessment of lipid compounds and phosphorus in mangrove sediments of Santa Catarina Island, SC, Brazil

“…Lipids were then taken up in 2 mL of CH 2 Cl 2 and passed through a Pasteur pipette minicolumn containing 1 g of combusted Na 2 SO 4 to remove any residual water. 33 Lipid isolations were performed in a glass column (0.5 cm i.d. x 4 cm effective length) filled with previously activated alumina (2 g, top part of the column) and silica (2 g, lower part).…”

Biomarkers as organic-carbon-source and environmental indicators in the Late Quaternary Arctic Ocean: problems and perspectives

“…Consequently a pronounced algal signature is not necessarily marine in origin, and all data have to be interpreted cautiously. Whereas the long-chain fatty acids are almost exclusively of terrigenous origin, derived from specific terrestrial higher plants ŽEglinton and Hamilton, 1963;Madureira et al, . Ž 1995 , the short-chain saturated and monorpoly-.…”

“…Ž pigments Table 2 , short-chain n-alkanes e.g., Eglinton and Hamilton, 1963;Venkatesan et al, . 1987;Madureira et al, 1995 Salasoo, 1987;Villanueva et al, 1997 . The synthesis of long-chain n-alkanes by some special sulfatereducing bacteria seems to be of minor importance Ž .…”

Distribution of lipid compounds in sediments from Conceição Lagoon, Santa Catarina Island, Brazil

“…Lipids were then taken up in 2 mL of CH 2 Cl 2 and passed through a Pasteur pipette micro column containing 1 g of combusted Na 2 SO 4 to remove any residual water. 19 Lipid isolations were performed in a glass column (0.5 cm i.d. × 4 cm effective length) filled with previously activated alumina (2 g, top part of the column) and silica (2 g, lower part).…”