Lipid biomarker signatures as tracers for harmful cyanobacterial blooms in the Baltic Sea

The recent proliferation of harmful cyanobacterial blooms (cyanoHABs) in the Baltic and other marginal seas poses a severe threat for the health of infested ecosystems as e.g. the massive export and decay of cyanobacterial biomass facilitates the spread of bottom water hypoxia. There is evidence that cyanoHABs occurred repeatedly in the Baltic Sea but knowledge of their spatiotemporal distribution and the cyanobacteria that contributed to them is limited. In this study, we examined representatives of the major bloom-forming heterocystous cyanobacteria (i.e. Aphanizomenon, Dolichospermum (formerly Anabaena) and Nodularia) to establish lipid fingerprints that allow tracking these environmentally important diazotrophs in the modern and past Baltic Sea. The distribution of normal and mid-chain branched alkanes, fatty acid methyl esters, bacteriohopanepolyols and heterocyst glycolipids permitted a clear chemotaxonomic separation of the different heterocystous cyanobacteria but also indicated a close phylogenetic relationship between representatives of the genera Aphanizomenon and Dolichospermum. Compared to the discontinuous nature of phytoplankton surveys studies, the distinct lipid profiles reported here will allow obtaining detailed spatiotemporal information on the frequency and intensity of Baltic Sea cyanoHABs as well as their community composition using the time-integrated biomarker signatures recorded in surface and subsurface sediments. As heterocystous cyanobacteria of the genera Aphanizomenon, Dolichospermum and Nodularia are generally known to form massive blooms in many brackish as well as lacustrine systems worldwide, the chemotaxonomic markers introduced in this study may allow investigating cyanoHABs in a great variety of contemporary environments from polar to tropical latitudes.Peer reviewe

Влияние волнистости S-образных пружин на точностные характеристики часов

Экспериментальным путем установлено отрицательное влияние волнистости S-образных пружин на точностные характеристики наручных часов. Предложен способ оперативного контроля этого дефекта пружин

Life and death in the Chicxulub impact crater: a record of the Paleocene–Eocene Thermal Maximum

latitudes, with sea surface temperatures at some localities exceeding the 35 ∘C at which marine organisms experience heat stress. Relatively few equivalent terrestrial sections have been identified, and the response of land plants to this extreme heat is still poorly understood. Here, we present a new record of the PETM from the peak ring of the Chicxulub impact crater that has been identified based on nannofossil biostratigraphy, an acme of the dinoflagellate genus Apectodinium, and a negative carbon isotope excursion. Geochemical and microfossil proxies show that the PETM is marked by elevated TEXH86-based sea surface temperatures (SSTs) averaging ∼37.8 ∘C, an increase in terrestrial input and surface productivity, salinity stratification, and bottom water anoxia, with biomarkers for green and purple sulfur bacteria indicative of photic zone euxinia in the early part of the event. Pollen and plants spores in this core provide the first PETM floral assemblage described from Mexico, Central America, and the northern Caribbean. The source area was a diverse coastal shrubby tropical forest with a remarkably high abundance of fungal spores, indicating humid conditions. Thus, while seafloor anoxia devastated the benthic marine biota and dinoflagellate assemblages were heat-stressed, the terrestrial plant ecosystem thrived

Heterocyte glycolipid diketones: A novel type of biomarker in the N2-fixing heterocytous cyanobacterium Microchaete sp.

International audienceThe heterocyte (heterocyst) glycolipid (HG) content of heterocytous (heterocystous) cyanobacteria canprincipally be separated into two different types. In the first type, the aglycone moiety attached to thesugar headgroup exclusively contains hydroxyl functionalities resulting in the formation of HG diolsand HG triols. In the second type, one of the hydroxyl groups is replaced by a ketone functionality givingrise to HG keto-ols and HG keto-diols. In the N2-fixing heterocytous cyanobacterium Microchaetesp. PCC7126 both types of HGs were dominant and consisted primarily of two structural isomers each of theHG28diol and HG28keto-ol. In addition to these well-characterized HGs,Microchaetesp. PCC 7126 alsocontained a yet undescribed type of HG that based on comparison of retention times, molecular weightand mass spectrometry consisted of a hexose headgroup attached to an aglycone moiety with 28 carbonatoms at which two instead of one ketone functionalities were attached. Hence, the novel HG structurewas identified as HG28diketone. This study thus provides further evidence for the large structural diver-sity of HGs, which allows chemotaxonomic profiling of heterocytous cyanobacteria and in turn studyingthe community composition of these important diazotrophs in the geological rock record

Sea surface temperature reconstruction from IODP Hole 350-U1437B

Sea surface temperature data based on the tetraether index based on glycerol dialkyl glycerol tetraethers consisting of 86 carbon atoms (TEX86) and unsaturated ketone index (UK'37) paleothermometers as well as methane index (MI) and branched and isoprenoid tetraether index (BIT) values of the past 1 Ma at Site U1437

Fractional abundances of biomarkers from IODP Hole 350-U1437B

The dataset comprises fractional abundances of individual isoprenoid and branched glycerol dialkyl glycerol tetraethers (GDGTs) and C37 alkenones of samples from the past 1 Ma at Site 350-U1437 relevant for the calculation of the TEX86 (tetraether index based on glycerol dialkyl glycerol tetraethers consisting of 86 carbon atoms), methane index (MI), branched and isoprenoid tetraether index (BIT), and the unsaturated ketone index (UK'37), respectively. The ketone-bearing fractions were measured on an Agilent 7980 GC coupled to an Agilent 5975 MS (Agilent, Germany). The polar fractions were analyzed by high performance liquid chromatography coupled to mass spectrometry (HPLC/MS) using an Alliance 2690 HPLC (Waters, UK) and a Quattro LC triple quadrupole MS (Micromass, UK) to measure glycerol dialkyl glycerol tetraethers (GDGTs)

Concentrations of plant wax lipids from IODP Hole 350-U1437B

Concentrations of plant wax lipids (long-chain n-alkanes, n-alcohols, and nonacosan-10-ol), the carbon preference index of n-alkanes, the branched and isoprenoid tetraether index (BIT), and mass accumulation rates of total organic carbon (TOC) and C37 alkenones

Biomarker and XRF scanning data from IODP Site 350-U1437B: a study of paleoceanographic and paleoclimatic changes in the Northwest Pacific Ocean over the past 1 Ma

Sediment core U1437B was drilled during International Ocean Discovery Program Expedition 350 in 2014. The aim of this study was to infer information on the paleoclimatic and paleoceanographic evolution of the Northwest Pacific Ocean and adjacent East Asian continent over the past 1 Ma. For this, 174 freeze-dried and homogenized sediment samples from Site U1437 Hole B were extracted using a solvent mixture of dichloromethane:methanol (93:7, v:v) at elevated temperature (75° ) and pressure (50 bar) using a Büchi Speed Extractor (Büchi, Switzerland). Total lipid extracts were desulfurized and an aliquot with an added standard mixture was measured on an Agilent 7980 gas chromatograph (GC) coupled to an Agilent 5975 mass spectrometer (MS) to quantify long- chain n-alkanes, n-alcohols, and nonacosan-10-ol. Another aliquot of the total lipid extracts was separated into apolar, ketone and polar fractions using column chromatography. The ketone-bearing fractions were subsequently measured on an Agilent 7980 GC coupled to an Agilent 5975 MS (Agilent, Germany). The polar fractions were analyzed by high performance liquid chromatography coupled to mass spectrometry (HPLC/MS) using an Alliance 2690 HPLC (Waters, UK) and a Quattro LC triple quadrupole MS (Micromass, UK) to measure glycerol dialkyl glycerol tetraethers (GDGTs). Total organic carbon contents were determined on 200 mg decarbonized sediment powder using an ELTRA CS- 580A elemental analyzer. Additionally, sections 350-U1437B-1H-1A to 17F-4A, comprising the uppermost 120 m of Hole B and corresponding to the past 1 Ma, were scanned using an ITRAX micro-X-ray fluorescence (XRF) core scanner at Kochi Core Center, Japan. XRF spectra were generated every 2 cm with an exposure time of 60 sec. The X-ray beam was generated with a 3 kW Mo tube run at 30 kV and 55 mA. Sea surface temperature estimates calculated from the unsaturated ketone index (UK'37) and GDGT- based tetraether index (TEX86) as well as GDGT-based methane index (MI) and branched and isoprenoid tetraether index (BIT) values are reported in Dataset S1. Dataset S2 contains summed concentrations of long-chain n-alkanes, n-alcohols and nonacosan-10- ol, as well as mass accumulation rates of TOC and C37 alkenones, which were calculated using linear sedimentation rates, alkenone or TOC contents, and dry bulk densities from shipboard measurements (Tamura et al., 2015). Fractional abundances of individual GDGTs and C37 ketones are reported in Dataset S3. Dataset S4 comprises ratios of selected elements calculated from XRF scanning measurements on core sections of the uppermost 120 meters below seafloor of Site U1437 Hole B

Elemental ratios (Ba/Al and Al/Ca) from IODP Site 350-U1437

Selected elemental ratios (Ba/Al and Al/Ca*1000) calculated from individual element abundances in counts per second (cps) as measured via X-ray fluorescence (XRF)-scanning of the uppermost 120 meters below seafloor of Site U1437

Heterocyte glycolipids indicate polyphyly of stigonematalean cyanobacteria

International audienceThe cyanobacterial phylum is currently divided into five subsections (I-V), with the latter two containing no or false-branching (nostocalean) and true-branching (stigonematalean) cyanobacteria. Although morphological traits (such as cellular division and secondary branches) clearly separate both types of heterocytous cyanobacteria, molecular evidence indicates that stigonematalean cyanobacteria (Subsection V) do not form a monophyletic group but instead are interspersed and nested within the nostocalean cyanobacteria (Subsection IV). To further resolve the phylogeny of heterocytous cyanobacteria, we here analyzed the distribution of heterocyte glycolipids (HGs) in the true-branching cyanobacterium Stigonema ocellatum SAG 48.90 (type genus of Subsection V) and compared it with the HG inventory of other stigonematalean and nostocalean cyanobacteria. The most dominant HGs in S. ocellatum SAG 48.90 were 1-(O-hexose)-27-keto-3,25-octacosanediol (HG28 keto-diol) and 1-(O-hexose)-3,25,27-octacosanetriol (HG28 triol), which together constituted ca. 94% of all HGs. In addition, 1-(O-hexose)-3-keto-27-octacosanols (HG28 keto-ols), 1-(O-hexose)-3,27-octacosanediols (HG28 diols), 1-(O-hexose)-3-keto-27,29-triacontanediol (HG30 keto-diol) and 1-(O-hexose)-3,27,29-triacontanetriol (HG30 triol) occurred in minor abundances. Heterocyte glycolipids previously reported to be unique for stigonematalean cyanobacteria, i.e. 1-(O-hexose)-3,29,31-dotriacontanetriols (HG32 triols) and 1-(O-hexose)-3-keto-29,31-dotriacontanediols (HG32 keto-diols), were not detected in S. ocellatum SAG 48.90. Comparison of the HG distribution pattern with those of other heterocytous cyanobacteria indicated that S. ocellatum SAG 48.90 is most closely related to the nostocalean families Rivulariaceae and Scytonemataceae, which is complementary to reconstructed 16S rRNA gene sequence phylogenies. Our HG-based data thus provides evidence for the polyphyly of stigonematalean cyanobacteria, independent from molecular approaches, and points to the need for a critical re-evaluation of the current taxonomy of heterocytous cyanobacteria