Sterol, n-alcohol and n-alkane composition of living fen plants

In groundwater-fed fen peatlands, the surface biomass decays rapidly and, as a result, highly humified peat is formed. A high degree of humification constrains palaeoecological studies because reliable identification of plant remains is hampered. Organic geochemistry techniques as a means of identifying historical plant communities have been successfully applied tobog peat. The method has also been applied to fen peat, but without reference to the composition of fen plants. We have applied selected organic geochemistry methods to determine the composition of the neutral lipid fractions from 12 living fen plants, to investigate the potential for the distributions to characterize and separate different fen plants and plant groups. Our results show correspondence with previous studies, e.g. C23 and C25n-alkanes dominating Sphagnum spp. and C27 to C31 alkanes dominating vascular plants. However, we also found similarities in n-alkane distributions between Sphagnum spp. and the below ground parts of some vascular plants. We tested the efficiency of different n-alkane ratios to separate species and plant groups. The ratios used for bog studies (e.g. n-C23/n-C25 and n-C23/n-C29) did not work as consistently for fen plants. Some differences in sterol distribution were found between vascular plants and mosses; in general vascular plants had a higher concentration of sterols. When distributions of n-alkanes, n-alkane ratios and sterols were all included as variables, redundancy analysis (RDA) separated different plant groups into their own clusters. Our results imply that the pattern for bog biomarkers cannot directly be applied to fen environments. Nevertheless, they encourage further testing to determine whether or not the identification of plant groups, plants or plant parts from highly humified peat is possible by applying fen species-specific biomarker proxies.

Ocean Acidification Affects Redox-Balance and Ion-Homeostasis in the Life-Cycle Stages of Emiliania huxleyi

Ocean Acidification (OA) has been shown to affect photosynthesis and calcification in the coccolithophore Emiliania huxleyi, a cosmopolitan calcifier that significantly contributes to the regulation of the biological carbon pumps. Its non-calcifying, haploid life-cycle stage was found to be relatively unaffected by OA with respect to biomass production. Deeper insights into physiological key processes and their dependence on environmental factors are lacking, but are required to understand and possibly estimate the dynamics of carbon cycling in present and future oceans. Therefore, calcifying diploid and non-calcifying haploid cells were acclimated to present and future CO2 partial pressures (pCO2; 38.5 Pa vs. 101.3 Pa CO2) under low and high light (50 vs. 300 µmol photons/m**2 /s). Comparative microarray-based transcriptome profiling was used to screen for the underlying cellular processes and allowed to follow up interpretations derived from physiological data. In the diplont, the observed increases in biomass production under OA are likely caused by stimulated production of glycoconjugates and lipids. The observed lowered calcification under OA can be attributed to impaired signal-transduction and ion-transport. The haplont utilizes distinct genes and metabolic pathways, reflecting the stage-specific usage of certain portions of the genome. With respect to functionality and energy-dependence, however, the transcriptomic OA-responses resemble those of the diplont. In both life-cycle stages, OA affects the cellular redox-state as a master regulator and thereby causes a metabolic shift from oxidative towards reductive pathways, which involves a reconstellation of carbon flux networks within and across compartments. Whereas signal transduction and ion-homeostasis appear equally OA-sensitive under both light intensities, the effects on carbon metabolism and light physiology are clearly modulated by light availability. These interactive effects can be attributed to the influence of OA and light on the redox equilibria of NAD and NADP, which function as major sensors for energization and stress. This generic mode of action of OA may therefore provoke similar cell-physiological responses in other protists.