Hydrological thresholds and basin control over paleoflood records in lakes

The scarcity of long-term hydrological data is a barrier to reliably determining the likelihood of floods becoming more frequent and/or intense in a warmer world. Lake sediments preserve characteristic event layers, offering the potential to develop widely distributed and unique chronologies of historical floods. Inferring flood magnitude remains a greater challenge, previously overcome in part by analyzing sharply laminated polar or alpine sequences. Here we demonstrate an approach to obtain flood frequency and magnitude data from an unexploited resource, the largely visually homogeneous, organic sediments that typify most temperate lakes. The geochemical composition and end-member modeling of sediment trap and adjacent short core particle size data for Brotherswater (northwest England) discriminates the signature of infrequent, coarse-grained flood deposits from seasonal and longer-term allogenic (enhanced discharge and sediment supply during winter) and autogenic (summer productivity, thermal mixing) depositional processes. Comparing the paleoflood reconstruction to local river discharges shows that hydrological thresholds censor event signature preservation, with 4 yr recurrence intervals detectable in delta-proximal sediments declining to 9 yr in the lake center. Event threshold (discharge) and process characterization are essential precursors to discerning flood magnitude from sediment archives. Implementation of our approach in globally prevalent temperate lakes offers a vast, unique repository of long-term hydrological data for hydrologists, climate modelers, engineers, and policy makers addressing future flood risks

Empathy, compassion, and theory of mind in obsessive‐compulsive disorder

Objectives: Individuals with obsessive-compulsive disorder (OCD) often suffer from impairments in social functioning. This study investigates differences in empathy, compassion, and Theory of Mind (ToM) in individuals with OCD as a possible cause for social functioning deficits. Design: Sixty-four individuals diagnosed with OCD and 62 healthy individuals completed a naturalistic behavioural task (EmpaToM) and a self-report measure (Interpersonal Reactivity Index, IRI). Methods: Three preregistered repeated measures analyses of variance (ANOVAs). Results: People with OCD exhibited higher empathy levels - namely increased sharing of others' suffering - in the EmpaToM task and reported more distress (IRI) compared with healthy individuals. Furthermore, no differences in compassion (EmpaToM) between both groups emerged, although people with OCD reported more concern for others (IRI) compared with healthy individuals. Concerning the ToM, no group differences were detected, neither in the behavioural task, nor self-report. Conclusion: By investigating OCD with diverse scientific practices we shed light on the higher levels of empathy exhibited by individuals with OCD, which are relevant for clinical practice and our understanding of OCD symptomatology. Practitioner points: People with obsessive-compulsive disorder show higher levels of empathy, that is the increased sharing of others' suffering, compared with healthy individuals in both a traditional self-report and a naturalistic task. Regarding compassion, that is caring for others, their self-reported compassion was higher in people with OCD. In Theory of Mind, that is cognitively understanding the situation of another person, no differences have been found neither at self-report nor in a naturalistic task compared with healthy individuals. Independent of traditional interventions, it could prove useful to improve emotion regulation skills so people with OCD learn to cope with empathic distress. Furthermore, it might strengthen the treatment gains and lower dropout rates if the social mind and consequently social relationships become a topic in the treatment and prevention of OCD

Stable oxygen and carbon isotopes of carbonates in lake sediments as a paleoflood proxy

Lake sediments are increasingly explored as reliable paleoflood archives. In addition to established flood proxies including detrital layer thickness, chemical composition, and grain size, we explore stable oxygen and carbon isotope data as paleoflood proxies for lakes in catchments with carbonate bedrock geology. In a case study from Lake Mondsee (Austria), we integrate high-resolution sediment trapping at a proximal and a distal location and stable isotope analyses of varved lake sediments to investigate flood-triggered detrital sediment flux. First, we demonstrate a relation between runoff, detrital sediment flux, and isotope values in the sediment trap record covering the period 2011–2013 CE including 22 events with daily (hourly) peak runoff ranging from 10 (24) m3 s−1 to 79 (110) m3 s−1. The three- to ten-fold lower flood-triggered detrital sediment deposition in the distal trap is well reflected by attenuated peaks in the stable isotope values of trapped sediments. Next, we show that all nine flood-triggered detrital layers deposited in a sediment record from 1988 to 2013 have elevated isotope values compared with endogenic calcite. In addition, even two runoff events that did not cause the deposition of visible detrital layers are distinguished by higher isotope values. Empirical thresholds in the isotope data allow estimation of magnitudes of the majority of floods, although in some cases flood magnitudes are overestimated because local effects can result in too-high isotope values. Hence we present a proof of concept for stable isotopes as reliable tool for reconstructing flood frequency and, although with some limitations, even for flood magnitudes

Laboratory observations of enhanced entrainment in dense overflows in the presence of submarine canyons and ridges

Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 55 (2008): 737-750, doi:10.1016/j.dsr.2008.02.007.The continental slopes in the oceans are often covered by small-scale topographic features such as submarine canyons and ridges. When dense plumes, flowing geostrophically along the slope, encounter such features they may be steered downslope inside and alongside the topography. A set of laboratory experiments was conducted at the rotating Coriolis platform to investigate the effect of small-scale topography on plume mixing. A dense water source was placed on top of a slope, and experiments were repeated with three topographies: a smooth slope, a slope with a ridge, and a slope with a canyon. Three flow regimes were studied: laminar, waves, and eddies. When a ridge or a canyon were present on the slope, the dense plume was steered downslope and instabilities developed along the ridge and canyon wall. This happened regardless of the flow characteristics on the smooth slope. Froude and Reynolds numbers were estimated, and were found to be higher for the topographically steered flow than for flow on smooth topography. The stratification in the collecting basin was monitored and the mixing inferred. The total mixing and the entrainment rate increased when a ridge or a canyon were present. The difference in mixing levels between the regimes was smaller when topography was present, indicating that it was the small-scale topography and not the large-scale characteristics of the flow that determined the properties of the product water.AW was funded by the Swedish Research Council and ED in part by Meltzer Stiftelsen, for which we are grateful. CC was supported by an NSF grant OCE-0085089. The work described in this publication was supported by the European Community's Sixth Framework Programme through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB III, Contract no. 022441 (RII3)

A new purple sulfur bacterium from saline littoral sediments, Thiorhodotvibrio winogradskyi gen. nov. and sp. nov.

Two strains of a new purple sulfur bacterium were isolated in pure culture from the littoral sediment of a saline lake (Mahoney Lake, Canada) and a marine microbial mat from the North Sea island of Mellum, respectively. Single cells were vibrioid-to spirilloid-shaped and motile by means of single polar flagella. Intracellular photosynthetic membranes were of the vesicular type. As photosynthetic pigments, bacteriochlorophyll a and the carotenoids lycopene, rhodopin, anhydrorhodovibrin, rhodovibrin and spirilloxanthin were present. Hydrogen sulfide and elemental sulfur were used under anoxic conditions for phototrophic growth. In addition one strain (06511) used thiosulfate. Carbon dioxide, acetate and pyruvate were utilized by both strains as carbon sources. Depending on the strain propionate, succinate, fumarate, malate, tartrate, malonate, glycerol or peptone may additionally serve as carbon sources in the light. Optimum growth rates were obtained at pH 7.2, 33 °C, 50 mol m-2 s-1 intensity of daylight fluorescent tubes and a salinity of 2.2–3.2% NaCl. During growth on sulfide, up to ten small sulfur globules were formed inside the cells. The strains grew microaerophilic in the dark and exhibited high specific respiration rates. No vitamins were required for growth. The DNA base composition was 61.0–62.4 mol% G+C. The newly isolated bacterium belongs to the family chromatiaceae and is described as a member of a new genus and species, Thiorhodovibrio winogradskyi gen. nov. and sp. nov. with the type strain SSP1, DSM No. 6702

Dissolved Organic Matter in the Upwelling System off Peru: Imprints of Bacterial Activity and Water Mass Characteristics

Microbial degradation of dissolved organic matter (DOM) contributes to the formation and preservation of oxygen minimum zones (OMZs) in the ocean, but information on the spatial distribution and molecular composition of DOM in OMZ regions is scarce. We quantified molecular components of DOM that is, dissolved amino acids (DAA) and dissolved combined carbohydrates (DCCHO), in the upwelling region off Peru. We found the highest concentrations of DCCHO in fully oxygenated surface waters steeply declining at shallow depth. The highest DAA concentrations were observed close to the surface also, but attenuation of DAA concentration over depth was less pronounced. Compositional changes of DCCHO were strongest within more oxygenated waters. Compositional changes of DAA were also evident under suboxic conditions (<5 µmol O2 kg−1) and indicated bacterial peptide degradation. Moreover, specific free amino acids (alanine and threonine) were enhanced within suboxic waters, pointing to a potential production of dissolved organic nitrogen under suboxic conditions. Our results therewith suggest that deoxygenation supports a spatial decoupling of DCCHO and DAA production and degradation dynamics and give new insights to carbon and nitrogen cycling in the OMZ off Peru