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Man-made structures in the North Sea are known to act as artificial reefs by providing a habitat for sessile epifauna in a predominantly soft sediment environment. This epifauna is hypothesized to cast a so-called "shadow"over the soft sediment ecosystem by altering the nutrient composition in the overlying water column. In addition, the structure itself could alter currents and thereby influence the deposition and erosion of the sediments in the wake of the platform. This study aims to assess the long-Term effects of a gas platform in the southern North Sea on the surrounding benthic community by both morphological and molecular identification of benthic species. The species composition and a set of abiotic factors of the sediment around a gas platform were assessed along four transects. Differences for the abiotic factors were found in the closer vicinity of the platform in the direction corresponding to the predominant currents. The number of benthic fauna families found in the molecular approach were on average three times higher than for the morphological approach. Both approaches showed that small differences occurred primarily due to changes in sedimentary organic matter content. Differences in species composition were more pronounced between transects rather than between distances from the platform.

The Black Sea basin is the sink for some of the largest European rivers and has acted as such, since it was part of the Eastern Paratethys. The late Miocene-to-Pliocene sedimentary record of the Black Sea documents several phases of strongly evaporitic conditions associated with extreme changes in regional hydrology. Here, we present the first combined record of continental temperature, soil type, and biomass burning in the circum–Black Sea region from the late Miocene to the transition into Pliocene (~ 10.0 to 5.0 Ma). We use branched glycerol dialkyl glycerol tetraethers (brGDGT) to reconstruct mean annual air temperature (MAT) and soil pH within the catchment of the Black Sea basin and complement these data with evidence from charcoal morphology as a proxy for burned biomass. The brGDGT data reveal generally decreasing temperatures and acidic soils between ~ 10 and 8.5 Ma, overlapping with increase in herbaceous cover in the Black Sea region. The Pontian flooding at 6.12 Ma is characterized by large quantities of organic debris and charcoal fragments in the basin and is followed by cooling starting at 5.97 Ma, event that is superimposed on the TG 20 and TG 22 glacial peaks (at 5.8 Ma). Between 5.8 and 5.0 Ma, the brGDGTs seem to be primarily derived from a cold steppe environment. Enhanced fire activity coinciding with generally cooler temperatures and a higher proportion of herbaceous plants are indicative of increased continentality between 5.8 and 5.0 Ma in the Black Sea region.

Methane emissions from peat bogs are mitigated by methanotrophs, which live in symbiosis with peat moss (e.g. Sphagnum). Here, we investigate the influence of temperature and resultant changes in methane fluxes on Sphagnum and methanotroph- related biomarkers, evaluating their potential as proxies in ancient bogs. A pulse-chase experiment using 13C-labelled methane in the field clearly showed label uptake in diploptene, a biomarker for methanotrophs, demonstrating in situ methanotrophic activity in Sphagnum under natural conditions. Peat cores containing live Sphagnum were incubated at 5, 10, 15, 20 and 25°C for two months, causing differences in net methane fluxes. The natural δ13C values of diploptene extracted from Sphagnum showed a strong correlation with temperature and methane production. The δ13C values ranged from −34‰ at 5°C to −41‰ at 25°C. These results are best explained by enhanced expression of the methanotrophic enzymatic isotope effect at higher methane concentrations. Hence, δ13C values of diploptene, or its diagenetic products, potentially provide a useful tool to assess methanotrophic activity in past environments. Increased methane fluxes towards Sphagnum did not affect δ13C values of bulk Sphagnum and its specific marker, the C23 n-alkane. The concentration of methanotroph-specific bacteriohopanepolyols (BHPs), aminobacteriohopanetetrol (aminotetrol, characteristic for type II and to a lesser extent type I methanotrophs) and aminobacteriohopanepentol (aminopentol, a marker for type I methanotrophs) showed a non-linear response to increased methane fluxes, with relatively high abundances at 25°C compared to those at 20°C or below. Aminotetrol was more abundant than aminopentol, in contrast to similar abundances of aminotetrol and aminopentol in fresh Sphagnum. This probably indicates that type II methanotrophs became prevalent under the experimental conditions relative to type I methanotrophs. Even though BHP concentrations may not directly refle

Sediment cores were collected using a piston corer at three sites in the eastern Mediterranean Sea. Piston cores MS21 (32°20.7'N, 31°39.0'E; 1022 m water depth; 751.5 cm in length) and MS66 (33°1.9'N, 31°47.9'E; 1630 m water depth; 630 cm in length) were recovered during the MIMES cruise with the R/V Pelagia in 2004. Piston core 64PE406E1 (33°18.1'N, 33°23.7'E; 1760 m water depth; 920.5 cm in length) was recovered during the Eastern Mediterranean part of the 64PE406 (NESSC) cruise with the R/V Pelagia in 2016. The cores were opened and then prepared for X-Ray Fluorescence (XRF) core scanning by carefully flattening the sediment and covering it with a 4-μm SPEXCerti Ultralene foil. Subsequently, the sediments were XRF-scanned with a 1-mm resolution using four settings (10 kV-no filter, 20 kV-Al filter, 30 kV-Pd-thick filter, and 50 kV-Cu filter). The produced XRF-core-scanner data were calibrated using a subset of the discrete samples taken from the same core material. These samples were digested with an acid mixture and partially measured by inductively coupled plasma mass spectrometry (ICP-MS) and partially measured by ICP-optical emission spectroscopy (ICP-OES). The main purpose of our data collection was to reconstruct in detail (~10-50 yr resolution) the deoxygenation and anoxia in the eastern Mediterranean Sea during the last 300 ka BP; we focused on elements and elemental ratios of Al, Ba, Mo, Ti, and U.

During the so-called Messinian Salinity Crisis (MSC: 5.97-5.33 Myr ago), reduced exchange with the Atlantic Ocean caused the Mediterranean to develop into a “saline giant” wherein ∼1 million km3 of evaporites (gypsum and halite) were deposited. Despite decades of research it is still poorly understood exactly how and where in the water column these evaporites formed. Gypsum formation commonly requires enhanced dry conditions (evaporation exceeding precipitation), but recent studies also suggested major freshwater inputs into the Mediterranean during MSC-gypsum formation. Here we use strontium isotope ratios of ostracods to show that low-saline water from the Paratethys Seas actually contributed to the precipitation of Mediterranean evaporites. This apparent paradox urges for an alternative mechanism underlying gypsum precipitation. We propose that Paratethys inflow would enhance stratification in the Mediterranean and result in a low-salinity surface-water layer with high Ca/Cl and SO4/Cl ratios. We show that evaporation of this surface water can become saturated in gypsum at a salinity of ∼40, in line with salinities reported from fluid inclusions in MSC evaporites.