Climate change, society, and pandemic disease in Roman Italy between 200 BCE and 600 CE.

Records of past societies confronted with natural climate change can illuminate social responses to environmental stress and environment-disease connections, especially when locally constrained high-temporal resolution paleoclimate reconstructions are available. We present a temperature and precipitation reconstruction for ~200 BCE to ~600 CE, from a southern Italian marine sedimentary archive-the first high-resolution (~3 years) climate record from the heartland of the Roman Empire, stretching from the so-called Roman Climate Optimum to the Late Antique Little Ice Age. We document phases of instability and cooling from ~100 CE onward but more notably after ~130 CE. Pronounced cold phases between ~160 to 180 CE, ~245 to 275 CE, and after ~530 CE associate with pandemic disease, suggesting that climate stress interacted with social and biological variables. The importance of environment-disease dynamics in past civilizations underscores the need to incorporate health in risk assessments of climate change.

Quantitative analysis of diverse sporomorph-derived sporopollenins.

Over the years studies on sporopollenin have reported a wide variety of structures. However, the methods and techniques used to elucidate sporopollenin structures are highly diverse so that much is still unclear with respect to the nature and structural diversity of sporopollenins. In order to investigate the structural diversity in sporopollenin between different taxa, extant sporomorphs of ten different species ranging from a mushroom to a cycad were examined using a relatively simple and fast analytical procedure. Sporomorphs, before and after saponification, were analysed for sporopollenin composition by Thermally assisted Hydrolysis and Methylation (THM) using [13C]tetramethylammonium hydroxide ([13C]TMAH). The sporomorp chemical composition differed markedly between the groups of organisms analysed. Moreover, we not only identified the nature and relative quantities of the well-known sporopollenin constituents p-coumaric acid and ferulic acid but also many other phenolic moieties, such as caffeic acid, which appeared to be the most abundant phenolic constituent in spores of Equisetum palustre, Salvinia molesta, Cyrtomium falcatum and Anemia phyllitidis. Within the two Equisetum species analysed as well as in the closely related Azolla and Salvinia species the same suite of phenolic constituents were observed, but their relative distribution varied largely. We thus demonstrate the existence of a high structural diversity, both qualitatively and quantitatively in sporopollenins enabling future studies related to the evolution, phylogeny and (palaeo)environment of sporopollenin-producing organisms. Furthermore, a better knowledge of sporopollenin and its structural variety is of relevance to the rapidly growing application of spores and pollen as a drug delivery agent in medicine.

Cryogenian evolution of stigmasteroid biosynthesis.

Sedimentary hydrocarbon remnants of eukaryotic C26-C30 sterols can be used to reconstruct early algal evolution. Enhanced C29 sterol abundances provide algal cell membranes a density advantage in large temperature fluctuations. Here, we combined a literature review with new analyses to generate a comprehensive inventory of unambiguously syngenetic steranes in Neoproterozoic rocks. Our results show that the capacity for C29 24-ethyl-sterol biosynthesis emerged in the Cryogenian, that is, between 720 and 635 million years ago during the Neoproterozoic Snowball Earth glaciations, which were an evolutionary stimulant, not a bottleneck. This biochemical innovation heralded the rise of green algae to global dominance of marine ecosystems and highlights the environmental drivers for the evolution of sterol biosynthesis. The Cryogenian emergence of C29 sterol biosynthesis places a benchmark for verifying older sterane signatures and sets a new framework for our understanding of early algal evolution.

Stratification of archaeal membrane lipids in the ocean and implications for adaptation and chemotaxonomy of planktonic archaea.

Membrane lipids of marine planktonic archaea have provided unique insights into archaeal ecology and paleoceanography. However, past studies of archaeal lipids in suspended particulate matter (SPM) and sediments mainly focused on a small class of fully saturated glycerol dibiphytanyl glycerol tetraether (GDGT) homologues identified decades ago. The apparent low structural diversity of GDGTs is in strong contrast to the high diversity of metabolism and taxonomy among planktonic archaea. Furthermore, adaptation of archaeal lipids in the deep ocean remains poorly constrained. We report the archaeal lipidome in SPM from diverse oceanic regimes. We extend the known inventory of planktonic archaeal lipids to include numerous unsaturated archaeal ether lipids (uns-AELs). We further reveal (i) different thermal regulations and polar headgroup compositions of membrane lipids between the epipelagic (≤ 100 m) and deep (>100 m) populations of archaea, (ii) stratification of unsaturated GDGTs with varying redox conditions, and (iii) enrichment of tetra-unsaturated archaeol and fully saturated GDGTs in epipelagic and deep oxygenated waters, respectively. Such stratified lipid patterns are consistent with the typical distribution of archaeal phylotypes in marine environments. We, thus, provide an ecological context for GDGT-based paleoclimatology and bring about the potential use of uns-AELs as biomarkers for planktonic Euryarchaeota.

The 2.1 Ga old Francevillian biota: biogenicity, taphonomy and biodiversity.

The Paleoproterozoic Era witnessed crucial steps in the evolution of Earth's surface environments following the first appreciable rise of free atmospheric oxygen concentrations ∼2.3 to 2.1 Ga ago, and concomitant shallow ocean oxygenation. While most sedimentary successions deposited during this time interval have experienced thermal overprinting from burial diagenesis and metamorphism, the ca. 2.1 Ga black shales of the Francevillian B Formation (FB2) cropping out in southeastern Gabon have not. The Francevillian Formation contains centimeter-sized structures interpreted as organized and spatially discrete populations of colonial organisms living in an oxygenated marine ecosystem. Here, new material from the FB2 black shales is presented and analyzed to further explore its biogenicity and taphonomy. Our extended record comprises variably sized, shaped, and structured pyritized macrofossils of lobate, elongated, and rod-shaped morphologies as well as abundant non-pyritized disk-shaped macrofossils and organic-walled acritarchs. Combined microtomography, geochemistry, and sedimentary analysis suggest a biota fossilized during early diagenesis. The emergence of this biota follows a rise in atmospheric oxygen, which is consistent with the idea that surface oxygenation allowed the evolution and ecological expansion of complex megascopic life.

Differences in the chemical composition of organic-walled dinoflagellate resting cysts from phototrophic and heterotrophic dinoflagellates.

Dinoflagellates constitute a large proportion of the planktonic biomass from marine to freshwater environments. Some species produce a preservable organic-walled resting cyst (dinocyst) during the sexual phase of their life cycle that is an important link between the organisms, the environment in which their parent motile theca grew, and the sedimentary record. Despite their abundance and widespread usage as proxy indicators for environmental conditions, there is a lack of knowledge regarding the dinocyst wall chemical composition. It is likely that numerous factors, including phylogeny and life strategy, determine the cyst wall chemistry. However, the extent to which this composition varies based on inherent (phylogenetic) or variable (ecological) factors has not been studied. To address this, we used micro-Fourier transform infrared spectroscopy to analyze nine cyst species produced by either phototrophic or heterotrophic dinoflagellates from the extant orders Gonyaulacales, Gymnodiniales, and Peridiniales. Based on the presence of characteristic functional groups, two significantly different cyst wall compositions are observed that correspond to the dinoflagellate's nutritional strategy. The dinocyst wall compositions analyzed appeared carbohydrate-based, but the cyst wall produced by phototrophic dinoflagellates suggested a cellulose-like glucan, while heterotrophic forms produced a nitrogen-rich glycan. This constitutes the first empirical evidence nutritional strategy is related to different dinocyst wall chemistries. Our results indicated phylogeny was less important for predicting composition than the nutritional strategy of the dinoflagellate, suggesting potential for cyst wall chemistry to infer past nutritional strategies of extinct taxa preserved in the sedimentary record.

The use of dinoflagellate cysts to separate human-induced from natural variability in the trophic state of the Po River discharge plume over the last two centuries.

To obtain insight into the natural and/or human-induced changes in the trophic state of the distal portion of the Po River discharge plume over the last two centuries, high temporal resolution dinoflagellate cyst records were established at three sites. Cyst production rates appear to reflect the natural variability in the river's discharge, whereas cyst associations reflect the trophic state of the upper waters, which in turn can be related to agricultural development. The increased abundances of Lingulodinium machaerophorum and Stelladinium stellatum found as early as 1890 and 1920 correspond to the beginning of the industrial revolution in Italy and the first chemical production and dispersion of ammonia throughout Europe. After 1955, the increased abundances of these species and of Polykrikos schwartzii, Brigantedinium spp. and Pentapharsodinium dalei correspond to agriculturally induced alterations of the hypertrophic conditions. A slight improvement in water quality can be observed from 1987 onward.