Sebastian Naeher

GNS Science

In this paper we synthesize the new knowledge on oxygen and oxygen-related phenomena in aquatic systems, resulting from the EU-FP7 project HYPOX (“In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and land-locked water bodies”, www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutr...

We analysed the distributions of glycerol dialkyl glycerol tetraethers (GDGTs) and other lipid biomarkers [glycerol dialkyl diethers (DGDs), fatty acids (FAs), sterols, hopanoids and phytol] in the water column and sediments of Lake Rotsee (Switzerland) to understand the processes and organisms involved in CH4 cycling. In the sediment we found subs...

Redox dynamics of manganese (Mn) were studied in the sediment of Lake Zurich using precise sediment core age models, monthly long-term oxygen (O-2) monitoring data of the water column (1936-2010) and high-resolution XRF core scanning. The age models were based on bi-annual lamination and calcite precipitation cycles. If present, Mn exhibits distinc...

We examined the distributions of tetrapyrrole pigments (i.e. intact chlorophylls and bacteriochlorophylls, pheopigments) as well as their compound-specific carbon and nitrogen isotopic compositions in the sediments of three Swiss lakes (Lakes Rotsee, Cadagno and Zurich) and the Black Sea to investigate the biogeochemical cycling of carbon and nitro...

The Paleocene Waipawa Formation is a widespread, ∼2–80 m-thick marine mudstone that occurs in several New Zealand basins. It is relatively enriched in organic matter (OM) and is the inferred source of a sub-commercial oil discovery and several correlated oil seeps. To determine the organofacies and depositional influences on the petroleum potential...

Ratios of glycerol dialkyl glycerol tetraethers (GDGT), which are membrane lipids of bacteria and archaea, are at the base of several paleoenvironmental proxies. They are frequently applied to soils as well as lake‐ and marine sediments to generate records of past temperature and soil pH. To derive meaningful environmental information from these re...

Understanding past fire regimes and how they vary with climate, human activity, and vegetation patterns is fundamental to the mitigation and management of changing fire regimes as anthropogenic climate change progresses. Ash‐derived trace elements and pyrogenic biomarkers from speleothems have recently been shown to record past fire activity in spe...

Glycerol dialkyl diethers (GDDs) are membrane lipids and a variation of the more commonly known glycerol dialkyl glycerol tetraethers (GDGTs). GDGTs include both archaeal and bacterial membrane lipids that are both frequently used for paleoclimate reconstruction in a range of terrestrial and aquatic environments. In contrast to GDGTs, GDDs lack one...

Radiocarbon ( ¹⁴ C) dating of sediment deposition around Antarctica is often challenging due to heterogeneity in sources and ages of organic carbon in the sediment. Chemical and thermochemical techniques have been used to separate organic carbon when microfossils are not present. These techniques generally improve on bulk sediment dates, but they n...

Understanding past fire regimes and how they vary with climate, human activity, and vegetation patterns is fundamental to the mitigation and management of changing fire regimes as anthropogenic climate change progresses. Ash-derived trace elements and pyrogenic biomarkers from speleothems have recently been shown to record past fire activity in spe...

Based on Nationally Determined Contributions concurrent with Shared Socioeconomic Pathways (SSPs) 2-4.5, the IPCC predicts global warming of 2.1–3.5 ∘C (very likely range 10–90th percentile) by 2100 CE. However, global average temperature is a poor indicator of regional warming and global climate models (GCMs) require validation with instrumental o...

Cyanobacterial blooms are increasing in frequency and intensity globally, impacting lake ecosystem health and posing a risk to human and animal health due to the toxins they can produce. Cyanobacterial pigments preserved in lake sediments provide a useful means of understanding the changes that have led to cyanobacterial blooms in lakes. However, t...

For the first time, polar organic compounds in extracted bitumen from the Lower Triassic Montney Formation have been analyzed. This stratigraphic unit is one of the most prolific low-permeability reservoirs in Western Canada. However, its organic geochemical characterization is a challenge due to low biomarker concentration in the liquids and frequ...

Based on Nationally-Determined Contributions concurrent with Shared Socio-economic Pathway (SSP) 2–4.5, the IPCC predicts global warming between 2.1–3.5°C (very likely range 10th–90th percentile) by 2100 AD. However, global average temperature is a poor indicator of regional warming and Global Climate Models (GCMs) require validation with instrumen...

Late Paleocene deposition of an organic-rich sedimentary facies on the continental shelf and slope of New Zealand and eastern Australia has been linked to short-lived climatic cooling and terrestrial denudation following sea level fall. Recent studies confirm that the organic matter in this facies, termed “Waipawa organofacies”, is primarily of ter...

Life on Earth produces innumerable structurally diverse biomolecules. Biomarkers, a subset of these compounds, are sufficiently specific in the structure that they serve as tracers of organisms present in the environment or preserved in the geological record. Biomarkers can be used as proxies for organisms and the biogeochemical processes they medi...

This article is composed of three independent commentaries about the state of Integrated, Coordinated, Open, Networked (ICON) principles in the American Geophysical Union Biogeosciences section, and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: (a) Global collaboration, technology tra...

Plain Language Summary Paleoceanography and Paleoclimatology seeks to reveal past changes in the oceans and the climate, to help us better understand how Earth systems work. Traditionally, it has a strong focus on international networks and cooperation and we have accomplished many international projects. However, we are still facing some major cha...

Lakes and their catchments have been subjected to centuries to millennia of exploitation by humans. Efficient monitoring methods are required to promote proactive protection and management. Traditional monitoring is time consuming and expensive, which limits the number of lakes monitored. Lake surface sediments provide a temporally integrated repre...

Late Paleocene deposition of an organic-rich sedimentary facies on the continental shelf and slope of New Zealand and eastern Australia has been linked to short-lived climatic cooling and terrestrial denudation following sea-level fall. Recent studies have confirmed that the organic matter in this facies, termed Waipawa organofacies, is primarily o...

The factors controlling Re-Os systematics and potential for geochronology in organic-rich sedimentary rocks deposited in fully terrestrial to paralic environments are not well understood. Here we present Re-Os, bulk pyrolysis and sulfur data for coals and coaly mudstones from the Late Cretaceous Rakopi and North Cape, Paleocene Farewell and Eocene...

In the middle–late Paleocene, a marine, organic-rich sedimentary unit (Waipawa Formation [Fm]) in which the organic matter was derived mainly from terrestrial plants was deposited in many of New Zealand's sedimentary basins. The unique organofacies of this formation has not been identified in any other time interval within the geological history of...

The Orui-1A stratigraphic drillhole near Riversdale, coastal Wairarapa, was drilled in 2011 by East Coast Energy Ventures to assess the prospectivity of the Paleocene Waipawa Formation, a widespread marine source rock. The drillhole was cored from 30.35 m to 117.3 m TD (total depth drilled), and acoustic image logs were run. The cored interval span...

Sedimentary hydrocarbon remnants of eukaryotic C 26 –C 30 sterols can be used to reconstruct early algal evolution. Enhanced C 29 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 syngene...

Pigmente aus Algen und Bakterien, zum Beispiel Chlorophyll, tragen dazu bei, den Sauerstoffgehalt sowie den Kohlenstoff- und den Stickstoffkreislauf in Seen und Ozeanen besser zu verstehen.

To reconstruct the impact of eutrophication on phototrophic communities and the biogeochemical cycling of carbon and nitrogen in the surface water, we investigated the distributions and carbon and nitrogen isotopic compositions (δ¹³C and δ¹⁵N values) of chlorins in the sediments of Lake Zurich. The chlorin distributions were dominated by chlorophyl...

To expand the limited knowledge about the ecological significance of anaerobic ammonium oxidation (anammox) in continental aquatic and terrestrial ecosystems, we studied community structure, abundance, and activity of anammox bacteria in soils and sediments in the wetland of Trou Deshayes, a riparian zone in the Seine Estuary, France. Combining (i)...

To expand the limited knowledge about the ecological significance of anaerobic ammonium oxidation (anammox) in continental aquatic and terrestrial ecosystems, we studied community structure, abundance, and activity of anammox bacteria in soils and sediments in the wetland of Trou Deshayes, a riparian zone in the Seine Estuary, France. Combining i)...

Ein Indikator für den Sauerstoffgehalt im Tiefenwasser von Seen ist das Verhältnis von Mangan zu Eisen in Sedimenten. Die Elementzusammensetzung der Sedimente ist mit Röntgenfluoreszenz messbar und zeigt auch die Umweltveränderungen der Vergangenheit.

Ergothioneine and ovothiol A are sulfur-containing histidine derivatives produced by microorganisms including Mycobacterium tuberculosis, Trypanosoma cruzi or Erwinia amylovora and may also play important roles in human physiology. Based on our recent identification of thiohistidine biosynthetic enzymes from Mycobacterium smegmatis and Erwinia tasm...

In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX ("In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies", http://www.hypox.net). In view of the anticipated oxygen loss in a...

We analysed glycerol dialkyl glycerol tetraether (GDGT) distributions in the water column, sediment and catchment soils of the Swiss Lake Rotsee to determine the sources of GDGTs in the lake sediment and to determine the implications for GDGT-based palaeoclimate proxies. The branched GDGT (brGDGT) distribution in the soils surrounding the lake show...

Maleimides (transformation products of chlorophylls and bacteriochlorophylls) were studied in recent sediments from the Swiss lake Rotsee and the Romanian Black Sea Shelf to investigate chlorophyll degradation, the role of oxygen in maleimide formation, and to identify their sources. Naturally occurring maleimides (i.e. "free" maleimides) and malei...

Sediments of lakes of high trophic level are often supersaturated with methane, a strong greenhouse gas which significantly contributes to global warming. Lake Rotsee and Lake Lungern are Swiss prealpine lakes known for their methane emission. Relevant transport mechanisms for methane emission are mainly equilibrium-controlled degassing and diffusi...

The Black Sea, containing the world's largest natural anoxic basin since ca 7500 years (Jones & Gagnon 1994), suffers from combined effects of anthropogenic eutrophication, overfishing and climate variability (Oguz & Gilbert 2007). We discuss causes for hypoxia in western shelf waters. Freshwater runoff by the large rivers Danube, Dniester and Dnie...

The evolution of environmental changes during the last decades and the impact on the living biomass in the western part of Amvrakikos Gulf was investigated using abundances of benthic foraminifera and lipid biomarker concentrations. These proxies indicated that the gulf has dramatically changed due to eutrophication. Eutrophication has led to a hig...

The effects of eutrophication on short term changes in the microbial community were investigated using high resolution lipid biomarker and trace metal data for sediments from the eutrophic Lake Rotsee (Switzerland). The lake has been strongly influenced by sewage input since the 1850s and is an ideal site for studying an anthropogenically altered e...

Chlorophylls and bacteriochlorophylls are the most abundant photosynthetic pigments on Earth. These compounds and their transformation products (chlorins, porphyrins, maleimides) can be preserved in limnic and marine sedimentary deposits and crude oils and serve as valuable proxies for palaeoenvironmental reconstructions. Among these degradation pr...

Trace metals, such as iron (Fe) and manganese (Mn), have received much attention in the last decades due to their redox-sensitive behaviour in the environment. In lakes, seasonal redox changes in the water column lead to biogeochemical cycling of Fe and Mn throughout the year. Under reducing conditions during stratification, they are (re)dissolved...

The effects of eutrophication on short term changes in the microbial community were investigated using high resolution lipid biomarker and trace metal data for sediments from the eutrophic Lake Rotsee (Switzerland). The lake has been strongly influenced by sewage input since the 1850s and is an ideal site for studying an anthropogenically altered e...

The evolution of environmental changes during the last decades and the impact on the living biomass in the western part of Amvrakikos Gulf was investigated using abundances and species distributions of benthic foraminifera and lipid biomarker concentrations. These proxies indicated that the gulf has markedly changed due to eutrophication. Eutrophic...