Investigations on the vertical migration of planktonic Crustacea in the Bodensee-Obersee. [Translation from: Schriften des Vereins fur Geschichte des Bodensees und seiner Umgebung, 87, 177-187, 1969.]

The vertical zoning of the planktonic Crustacea in a lake is the expression of a complex set of different factors. Besides the measurable, external influences such as light, temperature, acid and C02 stratification, a particularly large part is played by internal factors, which co-ordinate a specific reaction in each species depending on state of development, age and sex. Supporting this extensive, predictable, annual course of diurnal depths and the daily vertical migrations, whose extent is again dependent on external conditions, primarily of course on the amount of light. The individual factors mentioned, however, are here also of great significance. Within the scope of a long-term study of the planktonic Copepoda of Lake Constance, some day and night series were in 1963 also carried out in the Obersee, in order to obtain at least volumetric data on the extent of the daily migrations of these creatures

Inter-specific hybridization underlies phenotypic variability in Daphnia populations

In the glacial lakes of the Palaearctic three species of Cladocera commonly coexist: Daphnia hyalina, D. galeata , and D. cucullata . Frequently these populations contain not only animals which are morphologically typical for the species but also individuals of an intermediate phenotype. Electrophoretic investigations of allozyme-patterns in morphologically typical individuals reveal that each species is fixed for a different allele at the GOT locus. Morphologically intermediate animals are heterozygous for the alleles of the two species which they resemble. The allelic pattern at other loci is also consistent with the assumption that morphological intermediates are formed via interspecific hybridization. Very few backcrosses between galeata-hyalina hybrids and their parent species are found, and there is no indication of gene flow between D. cucullata and the other species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47761/1/442_2004_Article_BF00378763.pd

Control of primary productivity and the significance of photosynthetic bacteria in a meromictic kettle lake.

During 1986 planktonic primary production and controlling factors were investigated in a small (A0 = 11.8 · 103 m2, Zmax = 11.5 m) meromictic kettle lake (Mittlerer Buchensee). Annual phytoplankton productivity was estimated to ca 120 gC · m–2 · a–1 (1,42 tC · lake–1 · a–1). The marked thermal stratification of the lake led to irregular vertical distributions of chlorophylla concentrations (Chla) and, to a minor extent, of photosynthesis (Az). Between the depths of 0 to 6 m low Chla concentrations (< 7 mg · m–3) and comparatively high background light attenuation (kw = 0,525 m–1, 77% of total attenuation due to gelbstoff and abioseston) was found. As a consequence, light absorption by algae was low (mean value 17,4%) and self-shading was absent. Because of the small seasonal variation of Chla concentrations, no significant correlation between Chla and areal photosynthesis (A) was observed. Only in early summer (June–July) biomass appears to influence the vertical distribution of photosynthesis on a bigger scale. Around 8 m depth, low-light adapted algae and phototrophic bacteria formed dense layers. Due to low ambient irradiances, the contribution of these organisms to total primary productivity was small. Primary production and incident irradiance were significantly correlated with each other (r2 = 0.68). Although the maximum assimilation number (Popt) showed a clear dependence upon water temperature (Q10 = 2.31), the latter was of minor importance to areal photosynthesis

Anaerobic Microbial Degradation of Hydrocarbons: From Enzymatic Reactions to the Environment

Hydrocarbons are abundant in anoxic environments and pose biochemical challenges to their anaerobic degradation by microorganisms. Within the framework of the Priority Program 1319, investigations funded by the Deutsche Forschungsgemeinschaft on the anaerobic microbial degradation of hydrocarbons ranged from isolation and enrichment of hitherto unknown hydrocarbon-degrading anaerobic microorganisms, discovery of novel reactions, detailed studies of enzyme mechanisms and structures to process-oriented in situ studies. Selected highlights from this program are collected in this synopsis, with more detailed information provided by theme-focused reviews of the special topic issue on 'Anaerobic biodegradation of hydrocarbons' [this issue, pp. 1-244]. The interdisciplinary character of the program, involving microbiologists, biochemists, organic chemists and environmental scientists, is best exemplified by the studies on alkyl-/arylalkylsuccinate synthases. Here, research topics ranged from in-depth mechanistic studies of archetypical toluene-activating benzylsuccinate synthase, substrate-specific phylogenetic clustering of alkyl-/arylalkylsuccinate synthases (toluene plus xylenes, p-cymene, p-cresol, 2-methylnaphthalene, n-alkanes), stereochemical and co-metabolic insights into n-alkane-activating (methylalkyl) succinate synthases to the discovery of bacterial groups previously unknown to possess alkyl-/arylalkylsuccinate synthases by means of functional gene markers and in situ field studies enabled by state-of-the-art stable isotope probing and fractionation approaches. Other topics are Mo-cofactor-dependent dehydrogenases performing O-2-independent hydroxylation of hydrocarbons and alkyl side chains (ethylbenzene, p-cymene, cholesterol, n-hexadecane), degradation of p-alkylated benzoates and toluenes, glycyl radical-bearing 4-hydroxyphenylacetate decarboxylase, novel types of carboxylation reactions (for acetophenone, acetone, and potentially also benzene and naphthalene), W-cofactor-containing enzymes for reductive dearomatization of benzoyl-CoA (class II benzoyl-CoA reductase) in obligate anaerobes and addition of water to acetylene, fermentative formation of cyclohexanecarboxylate from benzoate, and methanogenic degradation of hydrocarbons

Anatomy of Heinrich Layer 1 and its role in the last deglaciation

X-ray fluorescence (XRF) core scanning and X-ray computed tomography data were measured every 1 mm to study the structure of Heinrich Event 1 during the last deglaciation at International Ocean Discovery Program Site U1308. Heinrich Layer 1 comprises two distinct layers of ice-rafted detritus (IRD), which are rich in detrital carbonate (DC) and poor in foraminifera. Each DC layer consists of poorly sorted, coarse-grained clasts of IRD embedded in a dense, fine-grained matrix of glacial rock flour that is partially cemented. The radiocarbon ages of foraminifera at the base of the two layers indicate a difference of 1400 $^{14}$C years, suggesting that they are two distinct events, but the calendar ages depend upon assumptions made for surface reservoir ages. The double peak indicates at least two distinct stages of discharge of the ice streams that drained the Laurentide Ice Sheet through Hudson Strait during HE1 or, alternatively, the discharge of two independent ice streams containing detrital carbonate. Heinrich Event 1.1 was the larger of the two events and began at ~16.2 ka (15.5–17.1 ka) when the polar North Atlantic was already cold and Atlantic Meridional Overturning Circulation (AMOC) weakened. The younger peak (H1.2) at ~15.1 ka (14.3 to 15.9 ka) was a weaker event than H1.1 that was accompanied by minor cooling. Our results support a complex history for Heinrich Stadial 1 (HS1) with reduction in AMOC during the early part (~20–16.2 ka) possibly driven by melting of European ice sheets, whereas the Laurentide Ice Sheet assumed a greater role during the latter half (~16.2–14.7 ka).This research used data acquired at the XRF Core Scanner Lab at the MARUM–Center for Marine Environmental Sciences, University of Bremen, Germany. This research used samples provided by the International Ocean Discovery Program (IODP). Funding for this research was provided by the UK Natural Environmental Research Council (NERC) to Hodell. The NERC Radiocarbon Facility supported two radiocarbon dates, and Wally Broecker generously supported the remainder with funding from the Comer Family Foundation. Research by Rodríguez-Tovar and Dorador was financed by Project CGL2015-66835-P. B.M. acknowledges support from the CSIC-Ramón y Cajal postdoctoral programme RYC-2013-14073. J.F.E. would like to acknowledge funding under ERC Advanced grant 320750- Nanopaleomagnetism

Epiphytic metazoans on emergent macrophytes in oxbow lakes of the Krapina River, Croatia: differences related to plant species and limnological conditions

This study investigated the structure of the epiphytic metazoans on emerged macrophytes in the littoral zone of two oxbow lakes with different trophic levels. Differences in the diversity and density of the epiphytic metazoans were analyzed in relation to plant architecture (simple or complex stems), food resources (algae and detritus) and water characteristics (transparency and derived trophic state index). Asignificant negative correlation was found between detritus on plants as food resource, and diversity and density of epiphytic metazoans, indicating grazing of microphagous species. Rotifers dominated in diversity and density in the epiphyton on all habitats. Total density of metazoans, rotifers and copepods in epiphyton were significantly higher on Mentha in mesotrophic lake than on Iris in a eutrophic lake.We presume that macrophyte belt width and trophic state governed biotic interactions and consequently epiphytic assemblages more strongly than macrophyte architecture. However, a Mentha habitat showed a slightly higher density and diversity of epiphytic metazoans in relation to Iris at the same site, but these differences were not significant

Effect of sampling effort and sampling frequency on the composition of the planktonic crustacean assemblage: a case study of the river Danube

Although numerous studies have focused on the seasonal dynamics of riverine zooplankton, little is known about its short-term variation. In order to examine the effects of sampling frequency and sampling effort, microcrustacean samples were collected at daily intervals between 13 June and 21 July of 2007 in a parapotamal side arm of the river Danube, Hungary. Samples were also taken at biweekly intervals from November 2006 to May 2008. After presenting the community dynamics, the effect of sampling effort was evaluated with two different methods; the minimal sample size was also estimated. We introduced a single index (potential dynamic information loss; to determine the potential loss of information when sampling frequency is reduced. The formula was calculated for the total abundance, densities of the dominant taxa, adult/larva ratios of copepods and for two different diversity measures. Results suggest that abundances may experience notable fluctuations even within 1 week, as do diversities and adult/larva ratios

Search for Eccentric Black Hole Coalescences during the Third Observing Run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass $M>70$ $M_\odot$) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities $0 < e \leq 0.3$ at $0.33$ Gpc$^{-3}$ yr$^{-1}$ at 90\% confidence level.Comment: 24 pages, 5 figure

S-nitrosothiols regulate nitric oxide production and storage in plants through the nitrogen assimilation pathway

Nitrogen assimilation plays a vital role in plant metabolism. Assimilation of nitrate, the primary source of nitrogen in soil, is linked to the generation of the redox signal nitric oxide (NO). An important mechanism by which NO regulates plant development and stress responses is through S-nitrosylation, that is, covalent attachment of NO to cysteine residues to form S-nitrosothiols (SNO). Despite the importance of nitrogen assimilation and NO signalling, it remains largely unknown how these pathways are interconnected. Here we show that SNO signalling suppresses both nitrate uptake and reduction by transporters and reductases, respectively, to fine tune nitrate homeostasis. Moreover, NO derived from nitrate assimilation suppresses the redox enzyme S-nitrosoglutathione Reductase 1 (GSNOR1) by S-nitrosylation, preventing scavenging of S-nitrosoglutathione, a major cellular bio-reservoir of NO. Hence, our data demonstrates that (S)NO controls its own generation and scavenging by modulating nitrate assimilation and GSNOR1 activity.5540