bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial variability of stable isotopes and fossil pigments in surface sediments of Alaskan coastal lakes: Constraints on quantitative estimates of past salmon abundance
Authors: Brock Curtis S. , Leavitt Peter R. , Schindler Daniel E. , Johnson Susan P. , Moore Jonathan W.
Published: July 2010

We quantified spatial patterns of stable isotopes of N and C (δ15N, δ13C) and fossil pigment concentrations in the uppermost 10 mm of sediment (,10 yr) from 74 profundal locations and three spawning‐stream discharge areas in Lake Nerka, southwest Alaska. Sediment δ15N (4.3% ± 0.7%) and δ13C (−26.3% ± 1.2%) varied directly (δ15N) or inversely (δ13C) with water column depth, whereas concentrations of most fossil pigments from algae were negatively correlated with depth. Sediment δ15N and δ13C were poorly correlated with either fossil pigment abundance or the local densities of spawning salmon. Instead, coastal nursery lakes appeared to integrate marine‐derived nutrients rapidly into lakewide nutrient pools, suggesting that while individual cores may be used to reconstruct whole‐lake salmon densities, habitat‐specific variations of past fish populations cannot be quantified reliably from sedimentary analyses.
Phytoplankton trapped within seagrass (Posidonia oceanica) sediments are a nitrogen source: An in situ isotope labeling experiment
Authors: Barrín Cristina , Middelburg Jack J. , Duarte Carlos M.
Published: July 2010

We examined the retention of nitrogen associated with sedimented planktonic material trapped within a Mediterranean seagrass (Posidonia oceanica) meadow with the use of 15N‐enriched algal material injected into vegetated and nonvegetated sediment as a tracer. The retention of labeled nitrogen material in the sediment and the appearance in P. oceanica leaves, rhizomes, and roots was examined 3, 5, 9, and 21 d after injection. More than 80% of the label material added to the bare sediment was lost within 5 d. Labeled material was retained better in vegetated sediments. Labeled material from the sediment was taken up rapidly by the roots, translocated through the rhizomes, and accumulated in the new leaves. The amount of 15N recovered during the experiment in P. oceanica meadow was fourfold higher than that recovered in unvegetated sediment, demonstrating that the P. oceanica meadow was more efficient in retaining the nitrogen deposited as algal material than unvegetated sediments. Enhanced trapping of sestonic particles by seagrass canopies can be an efficient nutrient acquisition strategy in the oligotrophic environments that seagrasses inhabit.
Nitrogen sources and cycling in the San Francisco Bay Estuary: A nitrate dual isotopic composition approach
Authors: Wankel Scott D. , Kendall Carol , Francis Chris A. , Paytan Adina
Published: July 2010

We used the dual isotopic composition of nitrate (δ15N and δ18O) within the estuarine system of San Francisco (SF) Bay, California, to explore the utility of this approach for tracing sources and cycling of nitrate (NO2−). Surface water samples from 49 sites within the estuary were sampled during July–August 2004. Spatial variability in the isotopic composition suggests that there are multiple sources of nitrate to the bay ecosystem including seawater, several rivers and creeks, and sewage effluent. The spatial distribution of nitrate from these sources is heavily modulated by the hydrodynamics of the estuary. Mixing along the estuarine salinity gradient is the main control on the spatial variations in isotopic composition of nitrate within the northern arm of SF Bay. However, the nitrate isotopic composition in the southern arm of SF Bay exhibited a combination of source mixing and phytoplankton drawdown due mostly to the long residence time during the summer study period. Very low δ18ONO3 values (as low as −5.0%) at the Sacramento–San Joaquin River delta region give rise to a wide range of δ18ONO3 values in the SF Bay system. The range in δ18ONO3 values is more than twice that of δ15NNO3, suggesting that δ18ONO3 is an even more sensitive tool for tracing nitrate sources and cycling than δ15NNO3.
Trophic upgrading of autotrophic picoplankton by the heterotrophic nanoflagellate Paraphysomonas sp.
Authors: Bec Alexandre , Martin-Creuzburg Dominik , von Elert Eric
Published: July 2010

We investigated whether trophic repackaging of autotrophic picoplankton by phagotrophic protists is associated with an improvement in food quality for the metazooplankton Daphnia magna (i.e., whether trophic upgrading occurs in this system). The nutritional value of the autotrophic species Microcystis aeruginosa PCC7806, Synechococcus sp. strain BO8809, Synechococcus elongatus SAG 89.79, and Choricystis minor KR1988/ 8, and of the heterotrophic nanoflagellate Paraphysomonas sp. grown on these different picoplanktonic species was evaluated in standardized growth experiments with D. magna. In order to investigate the functional role of the flagellate in the simplified autotrophic picoplankton‐Daphnia food chain, Paraphysomonas sp. was grown on the different picoplanktonic organisms and subsequently separated from the food items before being fed to D. magna. The presence of Paraphysomonas sp. as an intermediary trophic step enhanced somatic growth and reproduction of D. magna. Supplementation of Synechococcus sp. with lipids from Paraphysomonas sp. (grown on Synechococcus sp.) revealed that trophic upgrading of autotrophic picoplankton is due to the additional lipids present in the flagellate. Paraphysomonas sp. synthesized polyunsaturated fatty acids and sterols de novo, which most likely explains the trophic upgrading. Paraphysomonas sp. also improved the food quality of M. aeruginosa PCC7806, which is toxic for D. magna. The heterotrophic flagellate Paraphysomonas sp. is capable of trophically upgrading a poor quality food source not only by producing essential lipids, but also by detoxifying the cyanobacterial food organism.
Copper‐dependent iron transport in coastal and oceanic diatoms
Authors: Maldonado Maria T. , Allen Andrew E. , Chong Joanne S. , Lin Kevin , Leus Dan , Karpenko Nataliya , Harris Shannon L.
Published: July 2010

We investigated the presence of plasmalemma‐bound copper‐containing oxidases associated with the inducible iron (Fe) transport system in two diatoms of the genus Thalassiosira. Under Fe‐limiting conditions, Thalassiosira oceanica, an oceanic isolate, was able to enzymatically oxidize inorganic Fe(II) extracellularly. This oxidase activity was dependent on copper (Cu) availability and diminished by exposure to a multi‐Cu oxidase (MCO) inhibitor. The rates of Fe uptake from ferrioxamine B by Fe‐limited T. oceanica were also dependent on Cu availability in the growth media. The effects of Cu limitation on Fe(II) oxidation and Fe uptake from ferrioxamine B were partially reversed after a short exposure to a Cu addition, indicating that the putative oxidases contain Cu. Limited physiological experiments were also performed with the coastal diatom Thalassiosira pseudonana and provided some evidence for putative Cu‐containing oxidases in the high‐affinity Fe transport system of this isolate. To support these preliminary physiological data, we searched the newly available T. pseudonana genome for a multi‐Cu‐containing oxidase gene and, using real‐time polymerase chain reaction (PCR), quantified its expression under various Fe and Cu levels. We identified a putative MCO gene with predicted transmembrane domains and found that transcription levels of this gene were significantly elevated in Fe‐limited cells relative to Fe‐replete cells. These data collectively suggest that putative MCOs are part of the inducible Fe transport system of Fe‐limited diatoms, which act to oxidize Fe(II) following reductive dissociation of Fe(III) from strong organic complexes.
Response of Southern Ocean phytoplankton and bacterioplankton production to short‐term experimental warming
Authors: MorÁn XosÉ Anxelu G. , SebastiÁn Marta , Pedrís-Alií Carlos , Estrada Marta
Published: July 2010

We examined the potential response of Southern Ocean pelagic ecosystems to warming through changes in total primary production (particulate plus dissolved = PPP + DPP) and bacterial production (BP), determined simultaneously at ambient temperature (−1.4 to 0.4°C) and at 2°C in eight experiments performed near the Antarctic Peninsula in late spring 2002. Short (<6 h) time course experiments of radiocarbon uptake and photosynthesis‐irradiance relationships consistently showed that a significant amount of photosynthate appeared as dissolved substances, with a mean 35% extracellular release (PER). Whereas PPP remained virtually unchanged (0.7 mg C m−3 h−1), DPP increased significantly at 2°C from 0.5 to 0.9 mg C m−3 h−1. The corresponding increase in PER (54% on average) was significantly and positively correlated with the temperature difference among treatments, suggesting that an increase in DPP could be expected with a temperature rise in the Southern Ocean. BP, estimated via [3H]leucine incorporation, tended to increase at 2°C only at low absolute values, and this increment was inversely related to PPP. However, our results show that the estimated bacterial carbon demand (BCD) was generally well below concurrent DPP at both treatments (mean BCD:DPP ratios of 0.60 and 0.27 at ambient temperature and 2°C, respectively), indicating that temperature‐related extra inputs of organic substrates were not fully and immediately processed by bacteria. To the extent that these results reflect general ecophysiological trends, warming of Southern Ocean surface waters could produce changes in plankton‐mediated biogeochemical processes leading to a greater importance of dissolved organic matter fluxes.
Long‐term fluctuations (1974‐99) of the salps Thalia democratica and Salpa fusiformis in the northwestern Mediterranean Sea: Relationships with hydroclimatic variability
Authors: Licandro Priscilla , Ibañez FrÉdÉric , Etienne Michèle
Published: July 2010

We investigated the long‐term variability of the salps Thalia democratica and Salpa fusiformis during the period 1974‐1999 at a coastal site in the Bay of Villefranche‐sur‐mer. During this period T. democratica varied both interannually and seasonally, whereas S. fusiformis showed only seasonal fluctuations. Weeks in which T. democratica and S. fusiformis populations were developing in situ (i.e., near the sampling station without advection) are defined as the informative periods. Different species‐specific optima of temperature, salinity, and chlorophyll a concentration, as well as stability conditions of the water column, were related to informative periods for the two Thalia and Salpa species. Long‐term temperature oscillations were significantly related to the interannual maxima of T. democratica. The link between positive anomalies of temperature and outbreaks of T. democratica stress the importance of primary consumers as indicators of changes occurring in the marine system.
Consumer growth linked to diet and RNA—P stoichiometry: Response of Bosmina to variation in riverine food resources
Authors: Acharya Kumud , Bukaveckas Paul A. , Jack Jeffrey D. , Kyle Marcia , Elser James J.
Published: July 2010

Feeding experiments were performed with riverine Bosmina to investigate how their somatic growth rate responded to variation in food resources arising from changing hydrodynamic conditions. Experimental manipulations of food quality and quantity were achieved by diluting riverine suspended particulate matter (seston) to obtain a range of food concentrations and by amending natural seston with laboratory‐grown Scenedesmus acutus. Bosmina experienced food limitation during periods of elevated discharge when the P content of seston was low (C : P > 600). Growth rates covaried with body RNA and P contents (R2 = 0.96 and 0.86, respectively; content expressed as percent of dry mass), which is consistent with the hypothesis that high growth rates require increased allocation to P‐rich ribosomal RNA and that high seston C : P induces P limitation in riverine Bosmina. P limitation arises in riverine consumers of riverine seston when hydrologic conditions favor terrestrial inputs, sediment resuspension, and low algal productivity, thereby resulting in seston fractions dominated by P‐poor materials. During low discharge, riverine seston was P‐rich relative to Bosmina requirements and growth rates were decoupled from body P content. Bosmina RNA content was strongly and linearly related to growth over a broad range of resource conditions, suggesting that it may be a useful surrogate to assess dietary sufficiency of food resources in natural settings.
The importance of submarine groundwater discharge to the near shore nutrient supply in the Gulf of Aqaba (Israel)
Authors: Shellenbarger Gregory G. , Monismith Stephen G. , Genin Amatzia , Paytan Adina
Published: July 2010

We used two short‐lived radium isotopes (223Ra, 224Ra) and a mass balance approach applied to the radium activities to determine the nutrient contribution of saline submarine groundwater discharge to the coastal waters of the northern Gulf of Aqaba (Israel). Radium isotope activities were measured along transects during two seasons at a site that lacked any obvious surficial water input. An onshore well and an offshore end member were also sampled. For all samples, nutrients and salinity data were collected. Radium isotope activities generally decreased with distance offshore and exhibited significant tidal variability, which is consistent with a shorederived tidally influenced source. Submarine groundwater contributes only 1–2% of the water along this coast, but this groundwater provides 8–46% of the nutrients. This saline groundwater is derived predominately from tidally pumped seawater percolating through the unconfined coastal aquifer and leaching radium and nutrients. This process represents a significant source of nutrients to the oligotrophic nearshore reef.
Light supply, plankton biomass, and seston stoichiometry in a gradient of lake mixing depths
Authors: Berger Stella A. , Diehl Sebastian , Kunz Thomas J. , Albrecht Dieter , Oucible Amine M. , Ritzer Sylvie
Published: July 2010

We derive from a dynamic model that light availability, phytoplankton density, and the carbon : nutrient ratio of phytoplankton biomass should all be negatively related to mixed surface layer depth, whereas the areal standing stock of phytoplankton should show a unimodal, and total and dissolved nutrients a horizontal or increasing, relationship to mixing depth. These predictions agree closely with data from 65 central European lakes during summer stratification. In addition, zooplankton biomass was strongly negatively related to mixing depth in a subset of lakes. A decrease in mixing depth is thus a form of enrichment with light of the mixed surface layer, the effects of which could propagate to higher trophic levels.
Limnological conditions in Subglacial Lake Vostok, Antarctica
Authors: Christner Brent C. , Royston-Bishop George , Foreman Christine M. , Arnold Brianna R. , Tranter Martyn , Welch Kathleen A. , Lyons W. Berry , Tsapin Alexandre I. , Studinger Michael , Priscu John C.
Published: July 2010

Subglacial Lake Vostok is located ~4 km beneath the surface of the East Antarctic Ice Sheet and has been isolated from the atmosphere for ≫15 million yr. Concerns for environmental protection have prevented direct sampling of the lake water thus far. However, an ice core has been retrieved from above the lake in which the bottom ,85 m represents lake water that has accreted (i.e., frozen) to the bottom of the ice sheet. We measured selected constituents within the accretion ice core to predict geomicrobiological conditions within the surface waters of the lake. Bacterial density is two‐ to sevenfold higher in accretion ice than the overlying glacial ice, implying that Lake Vostok is a source of bacterial carbon beneath the ice sheet. Phylogenetic analysis of amplified small subunit ribosomal ribonucleic acid (rRNA) gene sequences in accretion ice formed over a deep portion of the lake revealed phylotypes that classify within the β‐, γ‐, and Δ‐Proteobacteria. Cellular, major ion, and dissolved organic carbon levels all decreased with depth in the accretion ice (depth is a proxy for increasing distance from the shoreline), implying a greater potential for biological activity in the shallow shoreline waters of the lake. Although the exact nature of the biology within Lake Vostok awaits direct sampling of the lake water, our data from the accretion ice support the working hypothesis that a sustained microbial ecosystem is present in this subglacial lake environment, despite high pressure, constant cold, low nutrient input, potentially high oxygen concentrations, and an absence of sunlight.
Probing the microenvironment of freshwater sediment macrofauna: Implications of deposit‐feeding and bioirrigation for nitrogen cycling
Authors: Stief Peter , de Beer Dirk
Published: July 2010

The effect of sediment‐dwelling macrofauna on nitrifying bacteria was investigated by direct probing in their overlapping habitat, i.e., the upper few millimeters of freshwater sediments. Microsensors (O2, NH4+, NO3‐, and diffusivity) were used at the sediment surface and inside animal burrows to record steady‐state and dynamic distributions of reactants, respectively. Short‐term changes of metabolic activity (actual and potential nitrification rates) and long‐term changes of abundance (fluorescence in situ hybridization) of nitrifying bacteria were determined. The presence of insect larvae (Chironomus riparius) increased the availability of O2 and NO3‐ in the sediment pore water and inside animal burrows, suggesting promotion of nitrification and dissimilatory NO3‐ reduction, particularly in the burrowing layer of C. riparius. At the sediment surface (i.e., in the feeding layer of C. riparius), however, nitrification was inhibited by low NH4+ availability and high macrofaunal grazing pressure. Consequently, both actual and potential nitrification rates decreased in the feeding layer. Inside burrows, no net nitrification was detected, despite high NH4+ availability and frequent O2 injections by larval ventilation activity. Conversely, burrows were sites of NH4+ production and consumption. Nevertheless, the abundance of nitrifying bacteria increased measurably in the burrowing layer after prolonged incubation, but only in sediments in which the larvae were able to construct and ventilate stable burrows.
Red and black tides: Quantitative analysis of water‐leaving radiance and perceived color for phytoplankton, colored dissolved organic matter, and suspended sediments
Authors: Dierssen Heidi M. , Kudela Raphael M. , Ryan John P. , Zimmerman Richard C.
Published: July 2010

Using field measurements and quantitative modeling, we demonstrate that red coloration of the sea surface is not associated with any particular group of phytoplankton and is strongly dependent on the physiology of the human visual system. Red or brown surface waters can be produced by high concentrations of most types of algae, colored dissolved organic matter, or suspended sediment. Even though light reflected by red tides commonly peaks in the yellow spectral region (570‐580 nm), human color perception requires consideration of the entire spectrum of light relative to receptors within the human eye. The color shift from green to red is not due to any special optical properties of the algae but results from an overlap in spectral response of the eye’s red and green cones (centered at 564 and 534 nm, respectively). The spectral peak in light reflected from dense algal blooms coincides with a critical hinge point in color vision (570‐580 nm), where fine‐scale shifts in the spectral shape of water‐leaving radiance due to algal absorption and backscattering properties lead to pronounced variations in the observed color. Of the taxa considered, only Chlorophytes and Prochlorophytes lacked sufficient accessory pigments to produce a red tide. Chlorophyll fluorescence and enhanced near‐infrared reflectance (the “red edge”) contribute negligibly to the perceived color. Black water events are produced when water is highly absorbing but lacks backscattering constituents.
Characteristics of the surface boundary layer important to the development of red tide on the southern Namaqua shelf of the Benguela upwelling system
Authors: Pitcher Grant C. , Nelson Greville
Published: July 2010

The southern Namaqua shelf, north of the Cape Columbine upwelling center, is particularly prone to red tide. Two influences of the surface boundary layer on the development of red tide in this area were investigated—the dynamics of the upper mixed layer in determining phytoplankton community composition and the role of mesoscale circulation in bloom concentration and transport. Two survey periods (18 February‐11 March 2000 and 13‐30 March 2001) are reported during which red tide, dominated by the dinoflagellate Gyrodinium zeta, formed in the area. A high degree of concordance between characteristics of stratification and groupings of phytoplankton demonstrated the importance of the upper mixed layer in determining species or life‐form selection and development. Ordination of across‐shelf phytoplankton samples revealed a consistent banded pattern, created by a wind‐induced upwelling plume, tending to isolate a nearshore zone from an offshore domain, thereby creating an area of retention on the coastal side of the plume, favoring development of dinoflagellate blooms. The appearance of red tide was clearly associated with increasingly stratified conditions driven by alongshore flow from the north, following periods of wind relaxation and consequent reversal of surface currents.
To sink or to be lysed? Contrasting fate of two large phytoplankton species in Lake Biwa
Authors: Kagami Maiko , Gurung Tek Bahadur , Yoshida Takehito , Urabe Jotaro
Published: July 2010

We estimated the contributions of sedimentation and cell lysis to the loss of two large phytoplankton species (Fragilaria crotonensis and Staurastrum dorsidentiferum) in Lake Biwa. Major loss process differed between species, and large phytoplankton did not necessarily function as a nutrient sink. The spring bloom of F. crotonensis was terminated by nutrient depletion and a subsequent increase in sedimentation rate. Although this species could be occasionally grazed by zooplankton, sedimentation eliminated nutrients from the surface. In contrast, the summer bloom of Staurastrum dorsidentiferum crashed mainly as a result of cell lysis caused by fungal infection within the surface mixing layer, which accounted for more than 75% of the mortality rate of this species. Cell lysis of S. dorsidentiferum may lead to nutrients within the surface mixing layer, supporting the production of bacteria and zooplankton. The different loss process of these two species implies that the function of phytoplankton in material flows cannot be assessed by cell size alone. Fungal parasitism can result in a different fate, which may play an important role in material cycling in lakes.
Stable isotopes in subtidal food webs: Have enriched carbon ratios in benthic consumers been misinterpreted?
Authors: Nadon Marc-Olivier , Himmelman John H.
Published: July 2010

We examined the hypothesis that the δ13C of benthic consumers is depleted in offshore, deeper waters where kelp and benthic microalgae are absent by conducting three analyses: (1) we analyzed δ13C (and δ15N) of consumers along a nearshore‐offshore gradient in the field, (2) we analyzed δ13C (and δ15N) of consumers placed in cages at various depths and distances from shore, and (3) we reexamined published stable isotope values for consumers taken at various depths from studies around the world. In all three situations, we did not observe the predicted change in δ13C values of benthic consumers. In both the literature and in our field measurements, the δ13C values for consumers were on average separated from the values for suspended particulate organic matter by 4%, irrespective of depth, indicating that factors other than the feeding on 13C‐rich benthic primary producers may explain the enriched carbon ratios in benthic consumers (e.g., selective feeding on enriched particles). The hypothesis that the high δ13C ratio in suspension and deposit feeders reflects feeding on benthic primary producers is thus tenuous and requires further investigation.
The effect of light stress on the release of volatile iodocarbons by three species of marine microalgae
Authors: Hughes Claire , Malin Gill , Nightingale Philip D. , Liss Peter S.
Published: July 2010

We investigated the influence of high light stress on iodocarbon release by three species of marine phytoplankton from different algal classes: the prymnesiophyte Emiliania huxleyi, the prasinophyte Tetraselmis sp., and the diatom Thalassiosira pseudonana. Despite a pronounced decrease in the fluorescence‐based maximum quantum yield for photosystem II (Fv/Fm), increased iodocarbon release relative to lower light controls was not observed in any of the experiments performed. These findings do not support the hypothesis that upper‐ocean iodocarbon concentrations are influenced by light‐induced algal stress.
Statistical dynamics of equatorial waves in tropical radiosonde wind data
Authors: Koh T.-Y. , Djamil Y. S. , Teo C. K.
Published: July 2010

Abstract. Weibull distributions were fitted to wind speed data from radiosonde stations in the global tropics. A statistical theory of equatorial waves was proposed to explain the shape parameter k obtained over Malay Peninsula and the wider Equatorial Monsoon Zone. The theory uses the (−5/3)-power law in quasi-2-D turbulence, classical Boltzmann statistics and the Central Limit Theorem. It provides a statistical dynamical basis for using empirical Weibull fits to derive wind speed thresholds for monitoring data quality. The regionally adapted thresholds retain more useful data than conventional ones defined from taking the regional mean plus three standard deviations. The new approach is shown to eliminate reports of atypically strong wind over Malay Peninsula which may have escaped detection in quality control of global datasets as the latter has assumed a larger spread of wind speed.
Laboratory measurements of trace gas emissions from biomass burning of fuel types from the Southeastern and Southwestern United States
Authors: Burling I. R. , Yokelson R. J. , Griffith D. W. T. , Johnson T. J. , Veres P. , Roberts J. M. , Warneke C. , Urbanski S. P. , Reardon J. , Weise D. R. , Hao W. M. , de Gouw J.
Published: July 2010

Abstract. Vegetation commonly managed by prescribed burning was collected from five southeastern and southwestern US military bases and burned under controlled conditions at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. The smoke emissions were measured with a large suite of state-of-the-art instrumentation including an open-path Fourier transform infrared (OP-FTIR) spectrometer for measurement of gas-phase species. The OP-FTIR detected and quantified 19 gas-phase species in these fires: CO2, CO, CH4, C2H2, C2H4, C3H6, HCHO, HCOOH, CH3OH, CH3COOH, furan, H2O, NO, NO2, HONO, NH3, HCN, HCl, and SO2. Emission factors for these species are presented for each vegetation type burned. Gas-phase nitrous acid (HONO), an important OH precursor, was detected in the smoke from all fires. The HONO emission factors ranged from 0.15 to 0.60 g kg−1 and were higher for the southeastern fuels. The fire-integrated molar emission ratios of HONO (relative to NOx) ranged from approximately 0.03 to 0.20, with higher values also observed for the southeastern fuels. The majority of non-methane organic compound (NMOC) emissions detected by OP-FTIR were oxygenated volatile organic compounds (OVOCs) with the total identified OVOC emissions constituting 61±12% of the total measured NMOC on a molar basis. These OVOC may undergo photolysis or further oxidation contributing to ozone formation. Elevated amounts of gas-phase HCl and SO2 were also detected during flaming combustion, with the amounts varying greatly depending on location and vegetation type. The fuels with the highest HCl emission factors were all located in the coastal regions, although HCl was also observed from fuels farther inland. Emission factors for HCl were generally higher for the southwestern fuels, particularly those found in the chaparral biome in the coastal regions of California.
Spatially explicit analyses of gastropod biodiversity in ancient Lake Ohrid
Authors: Hauffe T. , Albrecht C. , Schreiber K. , Birkhofer K. , Trajanovski S. , Wilke T.
Published: July 2010

Abstract. Spatial heterogeneity of biodiversity arises from evolutionary processes, constraints of environmental factors and the interaction of communities. The quality of such spatial analyses of biodiversity is improved by (i) utilizing study areas with well defined physiogeographical boundaries, (ii) limiting the impact of widespread species, and (iii) using taxa with heterogeneous distributions. These conditions are typically met by ecosystems such as oceanic islands or ancient lakes and their biota. While research on ancient lakes has contributed significantly to our understanding of evolutionary processes, statistically sound studies of spatial variation of extant biodiversity have been hampered by the frequently vast size of ancient lakes, their limited accessibility, and the lack of infrastructure around them. The small European ancient Lake Ohrid provides a rare opportunity for such a reliable spatial study. The comprehensive horizontal and vertical sampling of a species-rich taxon, the Gastropoda, presented here, revealed interesting patterns of biodiversity, which, in part, have not been shown before for other ancient lakes. In a total of 224 locations throughout the Ohrid Basin, representatives of 68 gastropod species with 50 of them being endemic (=73.5%) could be reported. The spatial distribution of these species shows the following characteristics: (i) within Lake Ohrid, the most frequent species are endemic taxa with a wide depth range, (ii) widespread species (i.e. those occurring throughout the Balkans or beyond) are rare and mainly occur in the upper layer of the lake, (iii) while the total number of species decreases with water depth, the share of endemics increases, (iv) the deeper layers of Lake Ohrid appear to have a higher spatial homogeneity of biodiversity and related environmental factors, (v) biotic interaction due to possible spillover effects may contribute to the establishment of hotspots, and (vi) eco-insularity within the Ohrid Basin occurs at two levels, at the level of the lake proper and at the level of the feeder-springs. It is also shown that large scale effects such as type of water body or water depth are mainly responsible for the distribution of biodiversity. In addition, small scale effects like environmental gradients or biotic interaction affect gastropod composition within a particular depth zone.
Testing the spatial and temporal framework of speciation in an ancient lake species flock: the leech genus Dina (Hirudinea: Erpobdellidae) in Lake Ohrid
Authors: Trajanovski S. , Albrecht C. , Schreiber K. , Schultheiß R. , Stadler T. , Benke M. , Wilke T.
Published: July 2010

Abstract. Ancient Lake Ohrid on the Balkan Peninsula is considered to be the oldest ancient lake in Europe with a suggested Plio-Pleistocene age. Its exact geological age, however, remains unknown. Therefore, molecular clock data of Lake Ohrid biota may serve as an independent constraint of available geological data, and may thus also help to refine age estimates. Such evolutionary data may also help unravel potential biotic and abiotic factors that promote speciation events. Here, mitochondrial sequencing data of one of the largest groups of endemic taxa in Lake Ohrid, the leech genus Dina, is used to test whether it represents an ancient lake species flock, to study the role of horizontal and vertical barriers in Lake Ohrid for evolutionary events, to estimate the onset of intralacustrine diversification in this group based on molecular clock analyses, and to compare this data with data from other endemic species for providing an approximate time frame for the origin of Lake Ohrid. Based on the criteria speciosity, monophyly and endemicity, it can be concluded that Lake Ohrid Dina, indeed, represents an ancient lake species flock. Lineage sorting of its species, however, does not seem to be complete. Analyses of population structures of Dina spp. in the Ohrid watershed indicate a horizontal zonation of haplotypes from spring and lake populations, corroborating the role of lake-side springs, particularly the southern feeder springs, for evolutionary processes in endemic Ohrid taxa. Vertical differentiation of lake taxa, however, appears to be limited, though differences between populations from the littoral and the profundal are apparent. Molecular clock analyses indicate that the most recent common ancestor of extant species of this flock is approximately 1.99±0.83 Ma old, whereas the split of the Lake Ohrid Dina flock from a potential sister taxon outside the lake is estimated at 8.30±3.60 Ma. Comparisons with other groups of endemic Ohrid species indicated that in all cases, intralacustrine diversification started ≤2 Ma ago. Thus, this estimate may provide information on a minimum age for the origin of Lake Ohrid. Maximum ages are less consistent and generally less reliable. But cautiously, a maximum age of 3 Ma is suggested. Interestingly, this time frame of approximately 2–3 Ma for the origin of Lake Ohrid, generated based solely on evolutionary data, well fits the time frame most often used in the literature by geologists. Future studies must show whether this concurrence holds true.
A new model of Holocene peatland net primary production, decomposition, water balance, and peat accumulation
Authors: Frolking S. , Roulet N. T. , Tuittila E. , Bubier J. L. , Quillet A. , Talbot J. , Richard P. J. H.
Published: July 2010

Abstract. Peatland carbon and water cycling are tightly coupled, so dynamic modeling of peat accumulation over decades to millennia should account for carbon-water feedbacks. We present initial results from a new simulation model of long-term peat accumulation, evaluated at a well-studied temperate bog in Ontario, Canada. The Holocene Peat Model (HPM) determines vegetation community composition dynamics and annual net primary productivity based on peat depth (as a proxy for nutrients and acidity) and water table depth. Annual peat (carbon) accumulation is the net balance above- and below-ground productivity and litter/peat decomposition – a function of peat hydrology (controlling depth to and degree of anoxia). Peat bulk density is simulated as a function of degree of humification, and affects the water balance through its influence on both the growth rate of the peat column and on peat hydraulic conductivity and the capacity to shed water. HPM output includes both time series of annual carbon and water fluxes, peat height, and water table depth, as well as a final peat profile that can be ``cored'' and compared to field observations of peat age and macrofossil composition. A stochastic 8500-yr, annual precipitation time series was constrained by a published Holocene climate reconstruction for southern Québec. HPM simulated 5.4 m of peat accumulation (310 kg C) over 8500 years, 6.5% of total NPP over the period. Vascular plant functional types accounted for 65% of total NPP over 8500 years but only 35% of the final (contemporary) peat mass. Simulated age-depth and carbon accumulation profiles were compared to a radiocarbon dated 5.8 m, c.9000-yr core. The simulated core was younger than observations at most depths, but had a similar overall trajectory; carbon accumulation rates were generally higher in the simulation and were somewhat more variable than observations. HPM results were sensitive to century-scale anomalies in precipitation, with extended drier periods (precipitation reduced ~10%) causing the peat profile to lose carbon (and height), despite relatively small changes in NPP.
Cyclones causing wind storms in the Mediterranean: characteristics, trends and links to large-scale patterns
Authors: Nissen K. M. , Leckebusch G. C. , Pinto J. G. , Renggli D. , Ulbrich S. , Ulbrich U.
Published: July 2010

Abstract. A climatology of cyclones with a focus on their relation to wind storm tracks in the Mediterranean region (MR) is presented. Trends in the frequency of cyclones and wind storms, as well as variations associated with the North Atlantic Oscillation (NAO), the East Atlantic/West Russian (EAWR) and the Scandinavian variability pattern (SCAND) are discussed. The study is based on the ERA40 reanalysis dataset. Wind storm tracks are identified by tracking clusters of adjacent grid boxes characterised by extremely high local wind speeds. The wind track is assigned to a cyclone track independently identified with an objective scheme. Areas with high wind activity – quantified by extreme wind tracks – are typically located south of the Golf of Genoa, south of Cyprus, southeast of Sicily and west of the Iberian Peninsula. About 69% of the wind storms are caused by cyclones located in the Mediterranean region, while the remaining 31% can be attributed to North Atlantic or Northern European cyclones. The North Atlantic Oscillation, the East Atlantic/West Russian pattern and the Scandinavian pattern all influence the amount and spatial distribution of wind inducing cyclones and wind events in the MR. The strongest signals exist for the NAO and the EAWR pattern, which are both associated with an increase in the number of organised strong wind events in the eastern MR during their positive phase. On the other hand, the storm numbers decrease over the western MR for the positive phase of the NAO and over the central MR during the positive phase of the EAWR pattern. The positive phase of the Scandinavian pattern is associated with a decrease in the number of winter wind storms over most of the MR. A third of the trends in the number of wind storms and wind producing cyclones during the winter season of the ERA40 period may be attributed to the variability of the North Atlantic Oscillation.
Fiber formation of a synthetic spider peptide derived from Nephila clavata
Authors: Hidaka Yuji , Kontani Ko‐Ichi , Taniguchi Rina , Saiki Masatoshi , Yokoi Sayoko , Yukuhiro Kenji , Yamaguchi Hiroshi , Miyazawa Mitsuhiro
Published: July 2010

Dragline silk is a high‐performance biopolymer with exceptional mechanical properties. Artificial spider dragline silk is currently prepared by a recombinant technique or chemical synthesis. However, the recombinant process is costly and large‐sized synthetic peptides are needed for fiber formation. In addition, the silk fibers that are produced are much weaker than a fiber derived from a native spider. In this study, a small peptide was chemically synthesized and examined for its ability to participate in fiber formation. A short synthetic peptide derived from Nephila clavata was prepared by a solid‐phase peptide method, based on a prediction using the hydrophobic parameter of each individual amino acid residue. After purification of the spider peptide, fiber formation was examined under several conditions. Fiber formation proceeded in the acidic pH range, and larger fibers were produced when organic solvents such as trifluoroethanol and acetonitrile were used at an acidic pH. Circular dichroism measurements of the spider peptide indicate that the peptide has a β‐sheet structure and that the formation of a β‐sheet structure is required for the spider peptide to undergo fiber formation. © 2010 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 96: 222‐227, 2011.
ChemInform Abstract: The Crystal Structure of YPdSi, the Isotypic Compounds LnPdSi (Ln: Gd—Lu), and Their Structural Relation to Some Other Equiatomic Compounds of the Rare Earth and Transition Metals with Main Group Elements.
Authors: PROTS' Y. M. , POETTGEN R. , JEITSCHKO W.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Chalcogenide Distribution in Microporous Layered Tin(IV) Thioselenide, TMA2Sn3SxSe7‐x, Materials.
Authors: AHARI H. , DAG OE. , PETROV S. , OZIN G. A. , BEDARD R. L.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: [NBu4n]4 [(Re6S5OCl7)2O], an Oxo‐Bridged Siamese Twin Cluster of Two Hexanuclear Oxochalcohalide Rhenium Clusters.
Authors: SIMON F. , BOUBEKEUR K. , GABRIEL J.‐C. P. , BATAIL P.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Synthesis and X‐Ray Diffraction Study of Nd1.4Ln0.2Sr0.4Ni1‐x CuxO4 .+‐. δ (Ln: Ce, Pr; 0 ≤ x ≤ 1) Solid Solutions.
Authors: NEDIL'KO S. A. , LISHKO T. P. , MANCHENKO O. F.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Condensed‐Phase Transitions During Effusion of Gallium Selenide.
Authors: VISWANATHAN R. , EDWARDS J. G.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Acidity of Substituted Mesoporous Molecular Sieve MCM‐48.
Authors: LANDMESSER H. , KOSSLICK H. , KUERSCHNER U. , FRICKE R.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: A Naphthalene‐Like Si1010‐ Unit in the Novel ∞2[Si2030‐] Planar Anion of Sr13Mg2Si20.
Authors: CURRAO A. , NESPER R.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Synthesis, Structure, and Properties of Zirconium Trivalent Metal (Al, Fe) Phosphates.
Authors: EGOR'KOVA O. V. , ORLOVA A. I. , PET'KOV V. I.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: The Room Temperature Conversion of Nickel Difluoride to Hexafluoronickelate(IV) Salts of Alkali Cations.
Authors: WHALEN J. M. , LUCIER G. M. , CHACON L. , BARTLETT N.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Strain Effects in Protonated Carbonyl Compounds. An Experimental and ab initio Treatment of Acyclic Carboxamides and Ketones
Authors: ABBOUD J.‐L. M. , ET AL. ET AL.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: P‐Chiral Bis(trialkylphosphine) Ligands and Their Use in Highly Enantioselective Hydrogenation Reactions.
Authors: IMAMOTO T. , WATANABE J. , WADA Y. , MASUDA H. , YAMADA H. , TSURUTA H. , MATSUKAWA S. , YAMAGUCHI K.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Optical Resolution by Preferential Crystallization of (RS)‐Bromosuccinic Acid
Authors: SHIRAIWA T. , OHKUBO M. , MIYAZAKI H. , KUBO M. , NISHIGAWA H. , TSUJIMOTO T. , KUROKAWA H.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Control of Both syn and anti Stereoselectivity in Michael Additions of Organotin Enolates.
Authors: SHIBATA I. , YASUDA K. , TANAKA Y. , YASUDA M. , BABA A.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Substituent Effects on Site Selectivity (C=C vs C=N) in Heterocumulene—Heterodiene [4 + 2] Cycloadditions: Density Functional and Semiempirical AM1 Molecular Orbital Calculations.
Authors: FABIAN W. M. F. , KOLLENZ G.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: A Novel Precursor for Per(poly)fluoroalkyl Heterocycles from N‐Aryl Per(poly)fluoroalkyl Imidoyl Iodides.
Authors: YU H.‐B. , HUANG W.‐Y.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Palladium‐Catalyzed Cyclization—Intermolecular Cyclopropanation versus Cyclization Friedel—Crafts Alkylation with Olefin Insertion.
Authors: BROWN D. , GRIGG R. , SRIDHARAN V. , TAMBYRAJAH V. , THORNTON‐PETT M.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Synthesis of 5,6,7,8‐Tetrahydro‐2H‐1‐benzopyran‐2,5‐diones and 1,5‐Dihydro‐2H‐pyrrol‐2‐ones.
Authors: MUSIC I. , GOLOBIC A. , VERCEK B.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.