Changes in long chain alkenone distributions and Isochrysidales groups along the Baltic Sea salinity gradient

Alkenone Distributions and Hydrogen Isotope Ratios Show Changes in Haptophyte Species and Source Water in the Holocene Baltic Sea

“…In that case, a transect from the Kattegat into the Baltic Sea basin showed the presence of all three haptophyte groups reflected in changing alkenone distributions. This was confirmed by 18S rDNA preserved in surface sediments (Kaiser et al, ). Additionally, the relative percent contribution of the C 37:4 alkenone (%C 37:4 ) increases for Group II species (Chivall et al, ) and has been proposed as a salinity proxy in culture and modern Baltic Sea sediments (Kaiser et al, ).…”

“…Salinities were reconstructed using %C 37:4 for the entire record and the RIK 37 equation for the Ancylus Lake phase since it was the only phase to contain C 37 tri‐unsaturated isomers (equations and , respectively; Kaiser et al, , ). Values ranged from 4.1 to 8.7 g kg −1 (%C 37:4 ) and 2.0 to 5.2 g kg −1 ( RIK 37 ), with the %C 37:4 yielding slightly higher values (Table ).…”

“…with % C37:4 being the concentration of C 37:4 as a percentage of total C 37 alkenones. Furthermore, salinity was estimated from the RIK 37 salinity calibration from Kaiser et al (2019):…”

“…Besides different alkenone distributions, the hydrogen isotope ratios of long‐chain alkenones also differ by group; more depleted δ 2 H C37 values are noted for Group III haptophytes compared to Group II when both are grown at the same salinity (Chivall et al, ; M'Boule et al, ). Based on distributions and hydrogen isotope ratios of alkenones, mixed contributions of Groups I and II as well as Groups II and III have been noted in some environments (Schwab & Sachs, ; Nelson & Sachs, ; Weiss, Schouten, et al, ), but a mixing of all three groups based on distributions has only been observed for surface sediments of the Baltic Sea (Kaiser et al, ). In that case, a transect from the Kattegat into the Baltic Sea basin showed the presence of all three haptophyte groups reflected in changing alkenone distributions.…”

Abrupt Freshening Since the Early Little Ice Age in Lake Sayram of Arid Central Asia Inferred From an Alkenone Isomer Proxy

“…Such increases in Group I LCA contributions indicate freshening of lake water at that time favorable for the growth of Group I Isochrysidales. Employing the published RIK 37 ‐salinity calibration (salinity = 14.77 × RIK 37 − 7.86; root mean square error (RMSE): ~1.2‰; Kaiser et al, 2019), we quantitatively reconstruct the salinity changes in Lake Sayram during the last ~3,000 years (Figure S3c and Table S4). Note that this calibration is the only one available at present, but further studies on regional calibration would help improve the accuracy of the reconstructed salinity.…”