S. Nemiah Ladd

S. Nemiah Ladd
University of Basel | UNIBAS · Department of Environmental Sciences

PhD

About

44
Publications
9,841
Reads
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461
Citations
Citations since 2016
33 Research Items
432 Citations
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2016201720182019202020212022020406080100120140
2016201720182019202020212022020406080100120140
2016201720182019202020212022020406080100120140
Additional affiliations
April 2019 - October 2021
University of Freiburg
Position
  • Lecturer
April 2017 - March 2019
ETH Zurich
Position
  • PostDoc Position
April 2015 - April 2017
Eawag: Das Wasserforschungs-Institut des ETH-Bereichs
Position
  • Fellow
Education
June 2011 - December 2014
University of Washington Seattle
Field of study
  • Oceanography
June 2009 - June 2011
University of Washington Seattle
Field of study
  • Oceanography
August 2006 - May 2008
University of Pennsylvania
Field of study
  • Education

Publications

Publications (44)
Article
Full-text available
Hydrogen isotope ratios (2H/1H or δ2H) of plant leaf waxes typically covary with those of precipitation, and are therefore used as a proxy for past hydrologic variability. Mangroves present an important exception to this relationship, as salinity can strongly influence 2H fractionation in leaf lipids. To better understand and calibrate this effect,...
Article
Compound specific hydrogen isotope ratios (2H/1H) of lipid biomarkers preserved in sediments are used as paleohydro- logic proxies. However, several variables, including contributions from different source organisms and their growth rates, can influence 2H/1H fractionation between lipids and source water. Significant uncertainties remain about how...
Article
Full-text available
Hydrogen isotope ratios of sedimentary leaf waxes (δ2HWax values) are increasingly used to reconstruct past hydroclimate. Here, we add δ2HWax values from 19 lakes and four swamps on 15 tropical Pacific islands to an updated global compilation of published data from surface sediments and soils. Globally, there is a strong positive linear correlation...
Article
Hydrogen isotope ratios of plant lipids are used for paleoclimate reconstruction, but are influenced by both source water and biosynthetic processes. Measuring 2H : 1H ratios of multiple compounds produced by different pathways could allow these effects to be separated, but hydrogen isotope fractionations during isoprenoid biosynthesis remain poorl...
Article
An experimental forest ecosystem drought Drought is affecting many of the world’ s forested ecosystems, but it has proved challenging to develop an ecosystem-level mechanistic understanding of the ways that drought affects carbon and water fluxes through forest ecosystems. Werner et al . used an experimental approach by imposing an artificial droug...
Article
The isotopic composition of xylem water (δX ) is of considerable interest for plant source water studies. In-situ monitored isotopic composition of transpired water (δT ) could provide a non-destructive proxy for δX -values. Using flow-through leaf chambers, we monitored 2-hourly δT -dynamics in two tropical plant species, one canopy-forming tree a...
Preprint
Full-text available
Drought can affect the capacity of soils to emit and consume biogenic volatile organic compounds (VOCs). Here we show the impact of prolonged drought followed by rain and recovery on soil VOC fluxes from an experimental rainforest. Under wet conditions the rainforest soil acted as a net VOCs sink, in particular for isoprenoids, carbonyls and alcoho...
Article
Full-text available
Monoterpenes (C10H16) are emitted in large quantities by vegetation to the atmosphere (>100 TgC year⁻¹), where they readily react with hydroxyl radicals and ozone to form new particles and, hence, clouds, affecting the Earth’s radiative budget and, thereby, climate change1–3. Although most monoterpenes exist in two chiral mirror-image forms termed...
Preprint
Drought impacts microbial carbon cycling, and thus the fate of carbon in soils. Carbon allocation to energy via CO 2 producing respiration and to biosynthesis via volatile organic compound (VOC) emissions both represent consequent carbon loss to the atmosphere, although only the former is well studied. Here, we examined drought impacts on carbon al...
Preprint
Full-text available
Daytime respiration in leaves is an integral component of plant metabolism, with CO 2 produced as a byproduct during the synthesis of many secondary metabolites, including many common volatile organic compounds (VOCs). It remains unclear how the carbon fluxes associated with daytime respiration and VOC emission vary among mature trees, and how they...
Article
Full-text available
Reconstructing past climate change in mangrove swamps contextualizes ongoing and future developments in these globally important ecosystems. Taraxerol, a well-recognized lipid biomarker for mangroves, is a promising target compound for calibration since it is relatively refractory and well preserved in sediments and since mangrove lipid δ2H and δ13...
Article
Full-text available
As direct mediators between plants and soil, roots play an important role in metabolic responses to environmental stresses such as drought, yet these responses are vastly uncharacterized on a plant-specific level, especially for co-occurring species. Here, we aim to examine the effects of drought on root metabolic profiles and carbon allocation pat...
Article
Full-text available
Long-chain polyunsaturated fatty acids are biologically important lipids that are unevenly distributed between and throughout environments. This heterogeneity can affect the evolution of metabolic processes, as populations adapt to the resource landscape that they encounter. Here, we compare fatty acid phenotypes of stickleback over two time scales...
Article
Full-text available
The nutritional diversity of resources can affect the adaptive evolution of consumer metabolism and consumer diversification. The omega-3 long-chain polyun-saturated fatty acids eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) have a high potential to affect consumer fitness, through their widespread effects on reproduct...
Preprint
Full-text available
Monoterpenes exist in mirror image forms called enantiomers, but their individual formation pathways in plants and ecological functions are poorly understood, as enantiomers are usually measured and modelled together. Here we present enantiomerically separated atmospheric monoterpene and isoprene data from an enclosed tropical rainforest ecosystem...
Article
Climate warming is causing rapid spatial expansion of ocean warm pools from equatorial latitudes towards the subtropics. Sedentary coral reef inhabitants in affected areas will thus be trapped in high temperature regimes, which may become the “new normal”. In this study, we used clownfish Amphiprion ocellaris as model organism to study reef fish me...
Article
Climate warming is causing rapid spatial expansion of ocean warm pools from equatorial latitudes towards the subtropics. Sedentary coral reef inhabitants in affected areas will thus be trapped in high temperature regimes, which may become the “new normal”. In this study, we used clownfish Amphiprion ocellaris as model organism to study reef fish me...
Article
Reconstructing past responses of coastal wetlands to climate change contextualizes ongoing and future developments in these globally important ecosystems. The molecular distributions and stable isotope ratios (δ²H and δ¹³C) of sedimentary plant wax n-alkanes are frequently used to infer past vegetation and hydroclimate changes in wetland systems. H...
Article
Anthropogenic soil erosion is a problem of global concern and recently has become the focus of extensive research. In spite of this, our knowledge about the history of land-use and its long-term impact on soil erosion and the local environment remains limited. This study seeks to address this issue by investigating sediments of Lake Murten, Switzer...
Article
Paleoclimatic changes during MIS7 and MIS6 remain poorly described in the Near East. We quantified source-specific biomarkers in Lake Van sediments during the interglacial/glacial cycle MIS7/MIS6. Long-chain n-alkanes produced by land-derived vegetation, as well as long-chain alkenones and sterols (namely brassicasterol and dinosterol) produced by...
Poster
Full-text available
Climate warming is causing the rapid expansion of tropical warm pools in the oceans at rates exceeding 2 million square kilometers per decade. This phenomenon is leading to increasingly larger ocean areas delimited by high temperature isotherms, especially in the range between 29˚C and 30˚C. From an ecological perspective, this means that marine an...
Article
Well prepared It is well known that species radiate into new niches by adapting to novel environments. But why do some species radiate in this way, while other, related, species do not. Ishikawa et al. looked across sticklebacks to determine why some, originally marine, lineages were able to colonize postglacial freshwater environments (see the Per...
Article
Full-text available
Please cite this article as: Krentscher, C., Dubois, N., Camperio, G., Prebble, M., Nemiah Ladd, S., Palmitone as a potential species-specific biomarker for the crop plant taro (Colocasia esculenta Schott) on remote Pacific islands, ABSTRACT The Pacific Island ecosystems of Remote Oceania were dramatically transformed following the arrival of human...
Article
Paired hydrogen and carbon isotope ratios (2H/1H and 13C/12C) of mangrove lipids can be used to quantita- tively reconstruct past salinity and 2H/1H ratios of environmental water, and in some cases precipitation rate. This approach is based on the observation that net 2H- and 13C-fractionation increases and decreases, respec- tively, with the salin...
Article
Sedimentary plant wax ²H/¹H ratios are important tools for understanding hydroclimate and environmental changes, but large spatial and temporal uncertainties exist about transport mechanisms from ecosystem to sediments. To assess atmospheric pathways, we collected aerosol samples for two years at four locations within a ∼60 km radius in northern Sw...
Article
Full-text available
The hydrogen isotopic composition (δ²H) of lipid biomarkers has diverse applications in the fields of paleoclimatology, biogeochemistry, and microbial community dynamics. Large changes in hydrogen isotope fractionation have been observed among microbes with differing core metabolisms, while environmental factors including temperature and nutrient a...
Article
The effect of salinity on hydrogen isotope fractionation during the production of leaf wax n-alkanes was assessed for Laguncularia racemosa (white mangrove), Rhizophora mangle (red mangrove), and Avicennia germinans (black mangrove) along a 31 ppt (parts per thousand) salinity gradient in the Shark River estuary, Florida, USA. Significant variation...
Article
Full-text available
The hydrogen isotope composition (δ²H) of biomarkers produced by algae is strongly influenced by the δ²H values of the water in which they grew. δ²H values of algal biomarkers preserved in lake sediments are thus a useful tool for reconstructing past changes in lake water δ2H values, which can be used to infer hydroclimate variability. However, stu...
Article
Hydrogen isotope ratios (²H/¹H or D/H) of sedimentary mangrove lipid biomarkers can be exploited as a quantitative proxy of past salinity and water isotopes. This approach is based on the observation that apparent ²H/¹H fractionation between surface water and mangrove leaf lipids increases with surface water salinity. In order to better understand...
Conference Paper
Full-text available
Hydrogen isotope ratios (2H/1H or δ2H) of algal lipid biomarkers have demonstrated potential as a proxy for past environmental conditions. The 2H/1H ratio of lipids is strongly influenced by that of the water in the algae grew. The isotopic composition of environmental water pools is in turn controlled by climatic variables such as temperature, pre...
Conference Paper
Full-text available
Hydrogen isotope ratios (1H/2H or δ2H) of mangrove leaf lipids are negatively correlated with salinity and have the potential to be developed as a proxy for past salinity and rainfall amount. The relationship between salinity and isotope fractionation in mangroves was first observed in estuaries, where salinity fluctuates with the tides, complicati...
Article
Hydrogen isotope ratios ((2) H/(1) H, δ(2) H) of leaf waxes covary with those in precipitation and are therefore a useful paleohydrologic proxy. Mangroves are an exception to this relationship because their δ(2) H values are also influenced by salinity. The mechanisms underlying this response were investigated by measuring leaf lipid δ(2) H and lea...
Article
Full-text available
Well-preserved sediment from closed water bodies of atolls such as Lib Pond are rare opportunities to reconstruct the past regional climate, which pieced together across a latitude and longitude range identify the range of movement patterns of wider scale climate phenomena such as the Intertropical Convergence Zone (ITCZ) and El Niño Southern Oscil...
Article
Carbon isotope ratio (δ13C) values of lipid biomarkers from plants can be used to assess water use efficiency and to reconstruct environmental conditions in the past. We assessed the effect of salinity on the δ13C values for leaf wax n-C31 and n-C33 alkanes, bulk leaf matter and leaf total lipid extracts from Avicennia marina (gray mangrove) trees...
Article
Hydrogen isotope ratios in lipids derived from mangroves have the potential to be used for paleohydrologic reconstructions and could serve as a much needed tool for establishing past climate variability in the tropics. We assessed the effect of salinity on the apparent fractionation factor, αa, between mangrove derived n-alkanes and their source wa...
Article
Stable hydrogen and carbon isotope ratios in mangrove-derived lipids are sensitive indicators of hydrologic changes and hold potential for improving our knowledge of recent paleoclimate variability in the tropics, but further calibration studies are required in order to quantitatively apply these tools. We assessed the effect of salinity on the app...
Article
Full-text available
Fluorescence anisotropy measurements were performed on a set of multichromophoric compounds, which contain a different number of aminopyrenyl moieties linked to a triazine ring, in order to reveal the nature of both the electronic excited states and relaxation pathways of the compounds. Our experimental results complement quantum chemical calculati...
Article
Full-text available
With the likelihood that carbon dioxide and other greenhouse-gas levels in the atmosphere will continue to increase for the next decades, and that the planet as a whole will likely warm as a result, we expect the oceanography and climate of the Galapagos to change. Based on an analysis of observational studies and climate models, the main changes a...
Conference Paper
Tropical rainfall patterns directly influence the subsistence lifestyle of more than a billion people and indirectly influence climate globally. Their seasonal changes are associated with the position of the Intertropical Convergence Zone (ITCZ) where deep convection causes heavy rainfall near 10°N in boreal summer and 3°N in winter. Dynamic contro...

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Projects

Projects (5)
Project
The occurrence and species composition of algae in lakes influence water quality, food webs, and the carbon cycle. One of the best ways to understand algae in the present and how they will react to future changes is to study their past occurrence by analyzing their remains in lake sediments. New methods based on lipid biomarkers and sedimentary DNA can help to reconstruct a more complete picture of the past. The overall goal of the ADAPT project is to understand how algae in lakes have reacted over time in response to human and natural changes. The project begins by assessing how well chemical fossils in water and surface sediments represent the current species composition of algae. These measurements are then applied to sediments to study how algae in Swiss lakes (1) reacted to rising and falling phosphorus concentrations in the 20th century, (2) how they reacted to changes in water quality caused by ancient Romans, and (3) to what extent they have changed in the last 10,000 years independently of human influence.
Project
The overarching goal of the experiment was to fully track the forest’s response to drought from molecules to the ecosystem. We accomplished this by measuring multiple ecosystem compartments (atmosphere, leaf, stem, root, soil) online with 133 online gas sampling locations sampled by clusters of gas analyzers for water (H2O) isotopes, carbon dioxide (CO2) isotopes, volatile organic compounds (VOCs), and other trace gases (20 online gas analyzers total) and 290 additional environmental sensors. Moreover, we used the glass and steel structure enclosing the rainforest biome to precisely control the rainfall regime, and also to deliver stable isotope labeling at unprecedented ecosystem scales including whole atmosphere 13C-CO2 pulse labeling to track the speed and fate of C allocation under drought and control conditions and deep water 2H-H2O labeling to trace the role of plant deep water access.
Archived project