bluuebunny/crossref_metadata_2025 huggingface dataset:
Microbial mediation of stromatolite formation in karst‐water creeks
Authors: Bissett Andrew , de Beer Dirk , Schoon Raphaela , Shiraishi Fumito , Reimer Andreas , Arp Gernot
Published: November 2010

Epilithic and endolithic biofilms were found to control the formation of stromatolites in karst‐water creeks. We used microsensors to determine the influence of biological processes on chemical conditions within the microenvironment of crystal nucleation sites: the stromatolite surface. Phototrophic members of the biofilms consisted of mainly cyanobacteria and diatoms. Oxygen, pH, calcium, and carbonate concentration microprofiles at the stromatolite surface and boundary layer showed a strong diurnal rhythm of calcium carbonate precipitation. During illumination, photosynthesis caused oxygen production, a marked increase in pH and CO32‐ concentrations, and a decrease in Ca2+ concentration at the stromatolite surface due to calcium carbonate precipitation. The opposite occurred in the dark, indicating decalcification. Calcite was approximately 16 times oversaturated in the bulk water, photosynthesis induced an increase of the supersaturation to <27 at the stromatolite surface under illumination, and respiration induced a decrease of the supersaturation to >10 in the dark. Photosynthetically stimulated calcium carbonate precipitation was confirmed by radioactive isotope (45Ca2+) uptake studies. Over a 24 h light : dark cycle, biofilms showed net calcification. Biotic activity within the stromatolite has a large effect on conditions at its surface and, therefore, contributes considerably to the stromatolite precipitation process.
Oligopeptide chemotypes of the toxic freshwater cyanobacterium Planktothrix can form sub‐populations with dissimilar ecological traits
Authors: Rohrlack Thomas , Edvardsen Bente , Skulberg Randi , Halstvedt Camilla B , Utkilen Hans C. , Ptacnik Robert , Skulberg Olav M.
Published: November 2010

Nonribosomal oligopeptides were used as qualitative and quantitative markers to test whether populations of the toxic freshwater cyanobacterium Planktothrix comprise subpopulations with dissimilar ecological traits. A field program was conducted in Lake Steinsfjorden (Norway), where Planktothrix has dominated the phytoplankton community for decades, allowing the present study to disregard other potential producers of nonribosomal oligopeptides. Four chemotypes with distinct cellular oligopeptide patterns were found in the lake. The chemotypes occurred largely unaltered throughout a period of up to 33 yr and differed with respect to seasonal dynamics, depth distribution, and participation in loss processes. Changes in the relative abundance of chemotypes occurred almost constantly and could not be explained with fluctuations in light, temperature, or concentration of macronutrients but might have been due to differences among chemotypes in depth regulation or interaction with grazers or pathogens. Chemotypes correlated weakly with taxonomic groups and genotypes defined on the basis of phycocyanin operon deoxyribonucleic acid (DNA) sequences. Our findings suggest that first, oligopeptide chemotypes can have dissimilar ecological traits and therefore interact differently with their environment; second, populations of toxic freshwater cyanobacteria can comprise multiple ecologically distinct subpopulations; and, third, the relative abundance of these may vary, causing a high variability in whole‐population properties. The latter was demonstrated for the microcystin‐related toxicity of Planktothrix. The consequences of the present findings for the taxonomy of Planktothrix are discussed.
Interactive influences of iron and light limitation on phytoplankton at subsurface chlorophyll maxima in the eastern North Pacific
Authors: Hopkinson Brian M. , Barbeau Katherine A.
Published: November 2010

The roles of iron and light as limiting and colimiting factors for phytoplankton growth in subsurface chlorophyll maxima (SCMs) were investigated in mesotrophic to oligotrophic waters of the Southern California Bight and the eastern tropical North Pacific using microcosm manipulation experiments. Phytoplankton responses indicative of iron‐light colimitation were found at several SCMs underlying macronutrient‐limited surface waters in the eastern Pacific. Iron additions led to a shift in the size and taxonomic structure of the phytoplankton community, where large diatoms dominated what was formerly a diverse community of relatively small phytoplankton. The strongest and most ubiquitous responses of diatoms to iron addition were found under elevated light conditions, indicating that iron availability may have the greatest potential to affect SCM phytoplankton communities when light levels increase rapidly, such as during eddy events or with strong internal waves. The results show that iron influences phytoplankton community structure at SCMs, which would have consequences for nutrient cycling and carbon export within the lower euphotic zone.
Hydrogeomorphic features mediate the effects of land use/cover on reservoir productivity and food webs
Authors: Bremigan Mary T. , Soranno Patricia A. , Gonzalez Maria J. , Bunnell David B. , Arend Kristi K. , Renwick William H. , Stein Roy A. , Vanni Michael J.
Published: November 2010

Although effects of land use/cover on nutrient concentrations in aquatic systems are well known, half or more of the variation in nutrient concentration remains unexplained by land use/cover alone. Hydrogeomorphic (HGM) landscape features can explain much remaining variation and influence food web interactions. To explore complex linkages among land use/cover, HGM features, reservoir productivity, and food webs, we sampled 11 Ohio reservoirs, ranging broadly in agricultural catchment land use/cover, for 3 years. We hypothesized that HGM features mediate the bottom‐up effects of land use/cover on reservoir productivity, chlorophyll a, zooplankton, and recruitment of gizzard shad, an omnivorous fish species common throughout southeastern U.S. reservoirs and capable of exerting strong effects on food web and nutrient dynamics. We tested specific hypotheses using a model selection approach. Percent variation explained was highest for total nitrogen (R2 = 0.92), moderately high for total phosphorus, chlorophyll a, and rotifer biomass (R2 = 0.57 to 0.67), relatively low for crustacean zooplankton biomass and larval gizzard shad hatch abundance (R2 = 0.43 and 0.42), and high for larval gizzard shad survivor abundance (R2 = 0.79). The trophic status models included agricultural land use/cover and an HGM predictor, whereas the zooplankton models had few HGM predictors. The larval gizzard shad models had the highest complexity, including more than one HGM feature and food web components. We demonstrate the importance of integrating land use/cover, HGM features, and food web interactions to investigate critical interactions and feedbacks among physical, chemical, and biological components of linked land‐water ecosystems.
Submarine discharge of nutrient‐enriched fresh groundwater at Stinson Beach, California is enhanced during neap tides
Authors: de Sieyes Nicholas R. , Yamahara Kevan M. , Layton Blythe A. , Joyce Elizabeth H. , Boehm Alexandria B.
Published: November 2010

The influence of fortnightly spring‐neap tidal variability on submarine discharge of fresh and saline groundwater was examined at Stinson Beach, California. Stinson Beach is a residential community that utilizes on‐site systems for wastewater disposal. Fresh, shallow groundwater at the site contains high concentrations of nutrients (dissolved inorganic nitrogen [DIN], soluble reactive phosphate [SRP], and silicate) and human fecal bacteria. A groundwater‐derived freshening and nutrification of the surf zone during neap tides was observed, followed by a 4‐d increase in chlorophyll a concentrations. Analytical models and a freshwater budget in the surf zone were used to estimate the saline and fresh discharge of submarine groundwater. We estimate fresh groundwater discharge between 1.2 and 4.7 L min‐1 m‐1 shoreline during neap tides compared with 0.1 and 0.5 L min‐1 m‐1 during spring tides. This compares with 15.9 and 22.0 L min‐1 m‐1 saline groundwater discharge (forced by waves and tides) during neap and spring tides, respectively. Despite the smaller total (fresh + saline) flux of groundwater during neap compared with spring tides, the larger fresh discharge component during neap tides raises surf zone silicate, DIN, and SRP by 14%, 35%, and 27%, respectively, relative to spring tides. This observed fortnightly pulsing of fresh groundwater‐derived nutrients was consistent with seaward hydraulic gradients across the fresh part of the beach aquifer, which varied due to aquifer overheight near the beach face. Darcy‐Dupuit estimates of seaward fresh groundwater flow in this area agreed well with the fresh discharge results of the mass balance.
Compound‐specific stable isotopes of organic compounds from lake sediments track recent environmental changes in an alpine ecosystem, Rocky Mountain National Park, Colorado
Authors: Enders Sara K. , Pagani Mark , Pantoja Silvio , Baron Jill S. , Wolfe Alexander P. , Pedentchouk Nikolai , Nuñez Lilian
Published: November 2010

Compound‐specific nitrogen, carbon, and hydrogen isotope records from sediments of Sky Pond, an alpine lake in Rocky Mountain National Park (Colorado, United States of America), were used to evaluate factors contributing to changes in diatom assemblages and bulk organic nitrogen isotope records identified in lake sediments across Colorado, Wyoming, and southern Montana. Nitrogen isotopic records of purified algal chlorins indicate a substantial shift in nitrogen cycling in the region over the past ~60 yr. Temporal changes in the growth characteristics of algae, captured in carbon isotope records in and around Sky Pond, as well as a ‐60‰ excursion in the hydrogen isotope composition of algal‐derived palmitic acid, are coincident with changes in nitrogen cycling. The confluence of these trends is attributed to an increase in biologically available nitrogenous compounds caused by an expansion of anthropogenic influences and temporal changes in catchment hydrology and nutrient delivery associated with meltwater dynamics.
A nitrate sink in estuaries? An assessment by means of stable nitrate isotopes in the Elbe estuary
Authors: Dähnke Kirstin , Bahlmann Enno , Emeis Kay
Published: November 2010

To elucidate the fate of river‐borne nitrate in the estuarine environment, we measured nitrate concentrations and Δ15N and Δ18O of nitrate along the salinity gradient in the estuary of the river Elbe, one of the largest German rivers discharging into the North Sea. Nitrate concentrations in river waters ranged from 78 µmol L‐1 to 232 µmol L‐1; Δ15N varied from 8.2‰ to 16.2‰, and the Δ18O values ranged from 20.1‰ to 3.2‰. The nitrate concentrations in the German Bight were between 2 µmol L‐1 and 34 µmol L‐1, with Δ15N between 8.0‰ and 12.2‰ and Δ18O between 0.3‰ and 9.5‰. Both riverine and marine end‐member concentrations showed seasonal variations, with lower nitrate concentrations and more enriched isotope values during spring and summer compared to winter months. We found no indication in either concentrations or isotopic composition for a significant loss of nitrate within the estuary, but we found a significant increase of nitrate in the maximum turbidity zone in summer. We attribute this to nitrification reflected in a change in the oxygen isotopic composition. The entire riverine nitrate load is entrained into the North Sea by conservative mixing; this conflicts with both the presumed role of estuaries as effective N‐sinks and with historical data from the Elbe estuary. Fundamental changes in the biogeochemical processes of the estuary have occurred over the past several decades due to extensive dredging and removal of sediment favorable for denitrification in the Elbe estuary that connects the port of Hamburg with the North Sea.
The interaction between inorganic iron and cadmium uptake in the marine diatom Thalassiosira oceanica
Authors: Lane Erin S. , Jang Kira , Cullen Jay T. , Maldonado Maria T.
Published: November 2010

We examined substrate‐saturated Fe(II) vs. Fe(III) uptake rates of Thalassiosira oceanica preconditioned to varying degrees of Fe limitation. Inorganic Fe(III) uptake rates by Fe‐sufficient T. oceanica were 2.4‐fold faster than the corresponding inorganic Fe(II) uptake rates. However, when cultures were severely Fe limited, the rate of Fe(II) uptake was upregulated 15‐fold, while that of Fe(III) uptake increased only fivefold. The interactions between substrate‐saturated uptake rates of inorganic Cd(II) and either Fe(II) or Fe(III) by Fe‐limited T. oceanica were also investigated. The addition of equimolar Cd(II) concentration to the Fe(II) uptake media resulted in a ~50% reduction of inorganic Fe(II) uptake rates compared with those in Cd‐free media. In turn, Cd uptake rates were inhibited ~36% in the presence of an equimolar Fe(II) concentration. In contrast to Fe(II), Fe(III) transport exhibited no interaction with Cd(II). T. oceanica thus has separate transporters for inorganic Fe(III) and Fe(II). Cadmium(II) and Fe(II) appear to enter the cell through a common putative divalent metal transporter that is upregulated under Fe deficiency. The interaction of Fe(II) and Cd(II) transport under Fe deficiency provides a plausible mechanism to explain some laboratory and field observations of higher Cd quotas in Fe‐limited phytoplankton.
Diversity in populations of free‐living Symbiodinium from a Caribbean and Pacific reef
Authors: Manning Mackenzie M. , Gates Ruth D.
Published: November 2010

The presence and diversity of free‐living dinoflagellates belonging to the endosymbiotic genus Symbiodinium were explored in seawater samples collected above coral reefs in KaneÂ'ohe Bay, OÂ'ahu, HawaiÂ'i, and Puerto Morelos, Quintana Roo, Mexico. Two genetic markers were used to assess Symbiodinium diversity in the water column: the internal transcribed spacer 2 region of the nuclear ribosomal array (ITS2), and a hypervariable region in domain V of the large subunit (23S) of the chloroplast ribosomal array (cp23S‐HVR). Sequencing of cloned gene fragments reveals that clades B, C, D, and H Symbiodinium are detectable in the seawater samples. In addition to the previously described types B1, C3, C15, C21, and D1, novel Symbiodinium sequences belonging to clades B and C were also retrieved. The majority of Symbiodinium sequences recovered from KaneÂ'ohe Bay belonged to clade C and those from Puerto Morelos to clade B, a pattern that reflects the dominant types of Symbiodinium found in endosymbiosis with scleractinian corals in these two areas. This study represents the first direct assessment of Symbiodinium diversity in waters adjacent to coral reefs located in the Caribbean and the Pacific and confirms the presence of Symbiodinium in this compartment of the ecosystem. These data provide context for future studies examining spatial and temporal patterns in the availability of Symbiodinium in the water column, work that will ultimately promote a greater understanding of the interactions between symbiotic dinoflagellates and their environmentally sensitive benthic hosts.
Spatial and temporal variability of solar ultraviolet exposure of coral assemblages in the Florida Keys: Importance of colored dissolved organic matter
Authors: Zepp Richard G. , Shank G. Christopher , Stabenau Erik , Patterson Karen W. , Cyterski Mike , Fisher William , Bartels Erich , Anderson Susan L.
Published: November 2010

Solar ultraviolet (UV) radiation can have deleterious effects on coral assemblages in tropical and subtropical marine environments, but little information is available on UV penetration into ocean waters surrounding corals. Here we provide an extensive data set of optical properties in the UV domain (280[en]400 nm) that were obtained during 1998‐2005 at sites located in the Lower and Middle Keys and the Dry Tortugas. Absorption coefficients of the colored component of the dissolved organic carbon (DOC; colored dissolved organic matter [CDOM]) were 6× to 25× larger than particulate absorption coefficients in the UV region, indicating that CDOM controls UV penetration in the inshore coastal waters and reef tract. CDOM absorption coefficients (αCDOM) and DOC were highly correlated to diffuse attenuation coefficients (Kd) in the UV spectral region. Measurements using moored sensors showed that UV penetration at the reef tract in the Lower Keys varies significantly from day to day and diurnally. The diurnal variations were linked to tidal currents that transport CDOM over the reef tract. Summertime stratification of Case 1 bluewaters near the reef tract during periods of low wind resulted in higher temperatures and UV penetration than that observed during well‐mixed conditions. This result suggests that higher UV exposure accompanying ocean warming during low‐wind doldrums conditions significantly contributes to coral bleaching. Modeling results indicate that changes in underwater sunlight attenuation over the coral reefs can affect UV‐induced deoxyribonucleic acid (DNA) damage and inhibition of coral photosynthesis much more strongly than changes in the stratospheric ozone layer.
Seaglider observations of blooms and subsurface chlorophyll maxima off the Washington coast
Authors: Perry M. J. , Sackmann B. S. , Eriksen C. C. , Lee C. M.
Published: November 2010

From September 2003 to December 2007, autonomous, underwater Seaglider continuously ran a V‐shaped transect off Washington State from about 200‐m water depth (i.e., at the break between the shelf and slope) to offshore waters with depths >2700 m. Seaglider visited the offshore vertex at 47°N, 128°W, where our observations concentrated, approximately monthly. Seaglider measured temperature, conductivity, and dissolved oxygen to 1000 m and also recorded chlorophyll a (Chl a) fluorescence and particulate optical backscatter to 150 m. Distinct interannual variation was documented in timing and depths of winter mixing, transition to a shallow summer pycnocline, and onset of mixed‐layer erosion in autumn. Chl a concentrations estimated from fluorescence were directly comparable among the seven laboratory‐calibrated sensors used, but their estimates exceeded concurrent, satellite‐derived concentrations by a factor of three. Seaglider optical profiles enabled interpretation of satellite imagery by revealing that the apparent autumn bloom after destratification was instead a vertical redistribution of phytoplankton from the subsurface maximum to a depth where they could be observed by satellites. Results of 4 yr of sampling within 25 km of the vertex demonstrate the value of gliders in ocean observing and their capability to carry out multiyear, fully autonomous operations under any sea state. The true power of glider programs will be realized in combination with other measurement platforms, including larger spatial coverage by satellites and more comprehensive biogeochemical measurements from moorings and occasional ship‐based sampling.
Net community production in the deep euphotic zone of the subtropical North Pacific gyre from glider surveys
Authors: Nicholson David , Emerson Steven , Eriksen Charles C.
Published: November 2010

Seagliders, deployed through most of 2005 in the subtropical North Pacific gyre, made measurements of temperature, salinity, and dissolved oxygen to quantify net community production (NCP) at Station A Long‐ Term Oligotrophic Habitat Assessment (ALOHA) of the Hawaii Ocean Time‐series (HOT) using an oxygen mass balance approach. A ‘bowtie’‐shaped pattern, 50 km by 50 km in size was repeatedly traversed at two week intervals with the goal of observing the influence of Rossby waves and eddies on the productivity of the study region. Rossby waves and eddies in the region cause a vertical displacement of isopycnal depth of ~±50 m at the base of the euphotic zone. Shoaling of isopycnals is demonstrated to drive productivity in the deep euphotic zone. Four mesoscale shoaling events were observed between February and November in 2005. During each event when isopycnals shoaled, oxygen concentrations on isopycnals increased, fluorescence in the deep euphotic zone was higher, and net community production was elevated. Productivity in the deep euphotic zone was strongly influenced by Rossby waves and eddies, but this influence was not observed to extend into the mixed layer.
Influence of water‐column depth and mixing on phytoplankton biomass, community composition, and nutrients
Authors: Jäger Christoph G. , Diehl Sebastian , Schmidt Gertraud M.
Published: November 2010

We independently manipulated mixing intensity (strong artificial mixing vs. background turbulence) and water‐column depth (2 m, 4 m, 8 m, and 12 m) in order to explore their separate and combined effects in a field enclosure experiment. To accentuate the vertical light gradient, enclosures had black walls, resulting in a euphotic depth of only 3.7 m. All enclosures were placed in a well‐mixed water bath to equalize temperature across treatments. Phytoplankton responded to an initial phosphorus pulse with a transient increase in biomass, which was highest in the shallowest, least light‐limited water columns where dissolved mineral phosphorus subsequently became strongly limiting. As a consequence, the depth‐averaged mineral phosphorus concentration increased and the seston carbon (C) : phosphorous (P) ratio decreased with increasing water‐column depth. Low turbulence enclosures became quickly dominated by motile taxa (flagellates) in the upper water column, whereas mixed enclosures became gradually dominated by pennate diatoms, which resulted in higher average sedimentation rates in the mixed enclosures over the 35‐d experimental period. Low turbulence enclosures showed pronounced vertical structure in water columns >4 m, where diversity was higher than in mixed enclosures, suggesting vertical niche partitioning. This interpretation is supported by a primary production assay, where phytoplankton originating from different water depths in low‐turbulence treatments had the relatively highest primary productivity when incubated at their respective depths of origin.
The spatial dynamics of vertical migration by Microcystis aeruginosa in a eutrophic shallow lake: A case study using high spatial resolution time‐series airborne remote sensing
Authors: Hunter P. D. , Tyler A. N. , Willby N. J. , Gilvear D. J.
Published: November 2010

Time‐series airborne remote sensing was used to monitor diurnal changes in the spatial distribution of a bloom of the potentially toxic cyanobacterium Microcystis aeruginosa in the shallow eutrophic waters of Barton Broad, United Kingdom. High spatial resolution images from the Compact Airborne Spectrographic Imager (CASI‐2) were acquired over Barton Broad on 29 August 2005 at 09:30 h, 12:00 h, and 16:00 h Greenwich mean time. Semiempirical water‐leaving radiance algorithms were derived for the quantification of chlorophyll a (R2 = 0.96) and C‐phycocyanin (R2 = 0.95) and applied to the CASI‐2 imagery to generate dynamic, spatially resolving maps of the M. aeruginosa bloom. The development of the bloom may have been fostered by a combination of the recent improvements in the ambient light environment of Barton Broad, allied to the acute depletion of bioavailable nutrient pools, and stable hydrodynamic conditions. The vertical distribution of M. aeruginosa was highly transient; buoyant colonies formed early morning and late afternoon near‐surface aggregations across the lake during periods of nonturbulent mixing (wind speed <4 m s‐1). However, the extent of these near‐surface aggregations was highly spatially variable, and nearshore morphometry appeared to be crucial in creating localized regions of nonturbulent water in which pronounced and persistent near‐surface aggregations were observed. The formation of these near‐surface scums would have been vital in alleviating light starvation in the turbid waters of Barton Broad. The calm water refuges in which persistent near‐surface accumulations occurred may have been an important factor in determining the persistence of the bloom.
Interactions between sediment resuspension and sediment quality decrease the TN:TP ratio in a shallow lake
Authors: Niemistö Juha , Holmroos Heidi , Pekcan-Hekim Zeynep , Horppila Jukka
Published: November 2010

The relative contributions of sediment resuspension and external nutrient loading to seasonal fluctuations of the total nitrogen to total phosphorus (TN : TP) ratio in the water column of the shallow Kirkkojarvi basin were studied. In May, the TN: TP mass ratio was above 30, but it decreased to below 10 in July‐August. In October, the ratio increased again. Water quality was regulated by external loading in spring, but the sharp decrease in the TN: TP ratio in July‐August resulted mainly from the elevated sediment resuspension rate. In May and October, the resuspension rate was below 20 g dry weight (wt) m−2 d−1, while in July‐August it exceeded 60 g dry wt m−2 d−1. Sediment resuspension decreases the TN: TP ratio in the water because the ratio in the surface sediment is low. The high resuspension rate in July‐August could not be explained by wind effects, water level fluctuations, or bioturbation, but was instead attributed to the seasonal change in the sediment quality. During the summer, fresh material having low critical shear stress settled on the bottom until the critical shear stress was lower than the actual shear stress, and the resuspension rate increased steeply, although no increment in wave effects occurred. For a shallow lake, a single representative TN: TP ratio is misleading, because the seasonally fluctuating resuspension rate substantially affects the ratio and may induce switches between N and P limitation. Seasonal fluctuations in the resuspension rate may have important effects on algal communities, because low N to P ratios can favor N‐fixing cyanobacteria over other algal groups. In Kirkkojarvi, cyanobacteria became the dominant algal group during the period of intensive resuspension.
Supersaturated N2O in a perennially ice‐covered Antarctic lake: Molecular and stable isotopic evidence for a biogeochemical relict
Authors: Priscu John C. , Christner Brent C. , Dore John E. , Popp Brian N. , Casciotti Karen L. , Lyons W. Berry
Published: November 2010

The east lobe of Lake Bonney, a permanently ice‐covered lake in the McMurdo Dry Valleys, Antarctica, has a mid‐depth maximum N2O concentration of 43.3 [mol N L‐1 (>700,000% saturation with respect to air), representing one of the highest concentrations reported for a natural aquatic system. δ15N and δ18O measurements indicate that this is the most isotopically depleted N2O yet observed in a natural environment (minimum δ15N‐N2O of ‐79.6‰ vs. air‐N2; minimum δ18O‐N2O of ‐4.7‰ vs. Vienna standard mean ocean water), providing new end points for these parameters in natural systems. The extremely depleted nitrogen and oxygen isotopes, together with nitrogen isotopic isomer data for N2O, imply that most of the N2O was produced via incomplete nitrification and has undergone virtually no subsequent consumption. However, molecular evidence provides little support for metabolically active nitrifying populations at depths where the maximal N2O concentrations occur and contemporary biogeochemical reactions cannot explain the extreme excesses of N2O in Lake Bonney. The gas appears to be a legacy of past biogeochemical conditions within the lake, and in the absence of a significant sink and the presence of a highly stable water column, gradients in N2O produced by past microbial activity could persist in the cold saline waters of Lake Bonney for >104 years.
Nickel limitation and zinc toxicity in a urea‐grown diatom
Authors: Egleston Eric S. , Morel François M. M.
Published: November 2010

When growing on urea as a nitrogen source, diatoms must accumulate nickel (Ni), a cofactor in the urease enzyme, which hydrolyzes urea. The uptake of Ni at low ambient concentrations is particularly challenging in view of the slow rate of reaction of the Ni2+ ion with uptake ligands. As expected, cultures of the model diatoms Thalassiosira weissflogii and Thalassiosira pseudonana become limited at very low Ni concentrations when growing on urea but not on nitrate or ammonium as a nitrogen source. At high Ni concentrations, urea‐grown cultures of T. weissflogii exhibit similar accumulation of various other metals to nitrate‐grown cultures and the same sensitivity to zinc and copper (Zn and Cu) concentrations. But at low Ni concentrations, T. weissflogii cells growing on urea accumulate excess Zn and exhibit extreme sensitivity to Zn toxicity. It appears that Zn accumulates in cells growing at low Ni concentrations by uptake through the up‐regulated Ni transport system. The resulting sensitivity of Ni‐limited cells to Zn (or to other metals that may be taken up via the Ni transport system) may limit the use of urea as a source of nitrogen in the oceans by some phytoplankton species.
Nitrogen and oxygen isotope fractionation during dissimilatory nitrate reduction by denitrifying bacteria
Authors: Granger Julie , Sigman Daniel M. , Lehmann Moritz F. , Tortell Philippe D.
Published: November 2010

We report the first measurements of coupled nitrogen (N) and oxygen (O) isotope fractionation of nitrate by laboratory cultures of denitrifying bacteria. Two seawater strains (Pseudomonas stutzeri, Ochrobactrum sp.) and three freshwater strains (Paracoccus denitrificans, Pseudomonas chlororaphis, Rhodobacter sphaeroides) were examined. Among four strains of facultative anaerobic denitrifiers, N and O isotope effects were variable, ranging from 5‰ to 25‰, with evidence for a drop in the isotope effects as nitrate concentrations approached the halfsaturation constant for nitrate transport. O isotope effects were similar to their corresponding N isotope effect, such that the progressive increase in nitrate δ18O, when plotted against that in δ15N (where δ18Osample = [(δ18O: δ16Osample/(δ18O:δ16O)reference ‐ 1] × 1000, and δ15Nsample × [(15N:14N)sample/(δ15N:δ14N)reference ‐ 1] × 1000), yielded slopes of 0.86 to 1.02, with a mean value of 0.96. R. sphaeroides, a photo‐heterotroph that possesses only a periplasmic (nonrespiring) dissimilatory nitrate reductase, showed less variability in nitrate N isotope effects, between 13‰ and 20‰, with a modal value of ~15‰. In contrast to the respiratory denitrifiers, R. sphaeroides consistently showed a distinct ratio of δ18O to δ15N change of ~0.62. We hypothesize that heavy N and O isotope discrimination during respiratory denitrification occurs during the intracellular reduction of nitrate by the respiratory nitrate reductase, and the observed magnitude of fractionation is likely regulated by the ratio of cellular nitrate efflux relative to uptake. The data for R. sphaeroides are consistent with isotope discrimination directly reflecting the N and O isotope effects of the periplasmic nitrate reductase NAP, without modification by nitrate uptake and efflux.
The role of organic acid exudates in liberating phosphorus from seagrass‐vegetated carbonate sediments
Authors: Long Matthew H. , McGlathery Karen J. , Zieman Joseph C. , Berg Peter
Published: November 2010

Sediment‐bound phosphorus (P) is a potential nutrient source for P‐limited seagrasses inhabiting carbonate sediments. We explored the role of organic acid (OA) exudation by seagrasses in liberating mineral P from carbonate sediments. Organic acids can act to increase available P by dissolving carbonate sediment, competing with P for binding sites and complexing dissolution end products, and also by fueling microbial processes that change pore‐water pH. We used dialysis tubing placed around individual roots in situ to quantify dissolved species immediately adjacent to roots (root zone) and compared these to bulk pore‐water concentrations in vegetated and nonvegetated sediments. Total OA concentrations were highest in the root zone (29.8 ± 1.8 [mol L−1) compared to bulk measures of 15.5 ± 1.9 and 7.5 ± 0.6 [mol L−1 in vegetated and nonvegetated sediments, respectively. Phosphate concentrations were also highest in the root zone and were linearly related to OA concentrations (R2 = 0.63). Organic acid concentrations increased along a seagrass productivity gradient, and ratios of OA concentrations to productivity showed a significant response to a gradient in P‐limitation of seagrasses. Organic acid concentrations found in and around roots, compared to those found in bulk sediment measures, indicate that seagrasses are a significant source of OA. Sampling at small spatial scales (mm) immediately adjacent to the roots is critical, because bulk sediment pore‐water measures did not capture the observed fluctuations caused by the rapid reaction and consumption of OA in the sediment. Root‐zone processes can liberate considerable quantities of P, and OA exudates likely contribute significantly to the success of T. testudinum in P‐limited environments.
A century of temperature variability in Lake Superior
Authors: Austin Jay , Colman Steve
Published: November 2010

A 100‐yr‐long time series of water temperature measured just downstream of Lake Superior is used to produce proxy time series of open‐lake temperature. This analysis suggests that open‐water Lake Superior summer temperatures have increased by roughly 3.5°C over the last century, most of that warming occurring in the last three decades. Correspondingly, the length of the positively stratified season has increased from 145 d to 170 d. The observed amount of warming is greater than the observed change in regional temperature over the same time period by roughly a factor of two. The discrepancy can be understood in the context of reduced winter ice cover, and implies that spatially and temporally averaged ice cover in Lake Superior has decreased from 23% to 12% over the last century.
A Soufflé Vision
Authors: Cleveland Penelope Moyers
Published: November 2010

This article was taken from Dr. Moyers Cleveland’s address given at the AOTA Annual Conference & Expo, held in Orlando, Florida, April 29–May 2, 2010.

In Orlando, I was introduced to the AOTA audience as American chef, author, and television personality Julia Child, who introduced French cuisine and cooking techniques to the American mainstream through her cookbooks and television programs. To underscore the metaphor of a soufflé representing the occupational therapy profession, I appeared onstage in an apron and holding a mixing bowl, pretending to be the great Julia Child.
Transformational Leadership and Substitutes for Management: An Exploratory Analysis
Authors: Weierter Stuart J. M.
Published: November 2010

Contemporary writers on management highlight the need for improved leadership within organisations. In this respect, this paper proposes and tests a model that incorporates leadership behaviours, situational variables, and traditional managerial behaviours. The results of this study indicated that, in highly formalised work environments, increasing work group cooperation reduces the need for direction provided by management. Furthermore, the transformational leader behaviours of individualised consideration and intellectual stimulation appeared to impact positively on perceptions of work group cooperation. These findings provide a basis for further research that examines the effects of transformational leader behaviours together with situational variables.
Expanding Management: Issues and Impacts of Women in Management Research
Authors: Pringle Judith
Published: November 2010

This paper reviews women in management research, as it moves from being a specialisation, to a source on influence on the mainstream. Specifically, there has been a shift from women to gender as a conceptual framework, which has led to explorations of identity issues in the workplace. There is a growing acceptance of organisations as manifestations of masculinity that is being differentiated into masculinities. The intersection of identities such as genders, race and ethnicity is beginning to be explored. The extensive work on sexual harassment is broadening to include research into the subtle but explicit presence of sexuality in organisations. Women have moved in management and are poised at the brink of senior management. At this point many women leave and studies are beginning to explore the functioning of women run organisations. Finally the potential ability of women in management research to expand the concept of management is noted.
Bringing a Client Focus to International Marketing: A Change Management Case Study
Authors: Patterson Paul
Published: November 2010

Consumers the world over are becoming more homogeneous thanks to the unifying forces of travel, media, technology, information transfer and the like. Furthermore, today customers have higher expectations than ever before regarding the quality of service they should receive from a wide range of service organisations (professional as well as non-professional). As customers are increasingly exposed to world best practice in a wide range of service industries, expectations spiral upwards. Slow, discourteous, unresponsive and unprofessional service will no longer be tolerated - but especially when the service is highly customised, complex, costly and high involvement, professional service.

Few, if any, studies have examined service quality issues for professional services in an international context. Hence, this case study documents the problems experienced by the Australian Trade Commission's (Austrade) Bangkok, Thailand Post in providing a level of service consistent with clients' (and senior managements') expectations, the steps taken to overcome
these long standing service quality shortcomings, as well as the key lessons to be learnt from the process. Today Austrade provides a professional consulting service and thus possesses similar characteristics to many professional service firms (project management, engineering consulting, general management consulting, etc.) and thus the lessons from this successful change management program may be generalisable to other professional services. Furthermore, the lessons should prove invaluable for Australian firms operating in South-East Asia staffed by expatriates and local nationals.
Quality Enhancement in Doctoral Education: Developing a More Public Process
Authors: Neumann Ruth , Guthrie James
Published: November 2010

Governments play an important role in providing an appropriate national framework and structure for the development of doctoral education. Nevertheless, ultimate responsibility for quality supervision processes lies with institutions, in particular with their departmental units and their policies and processes (DETYA, 1999c). This paper presents a case study of recent developments in the quality enhancement of doctoral supervision in the Macquarie Graduate School of Management (MGSM). In doing so it looks at three areas in particular: (1) the key role of infrastructure support, including the introduction of a code of practice in doctoral supervision; (2) the induction and acculturation processes; and (3) supervision quality, including the selection, development and training of supervisors. The aim of the developments is to make a recognized private process more public and transparent. MGSM currently enrolls a significant number of doctoral students and the enhancement of their doctoral experience is a key priority. The paper concludes by highlighting key issues for future development.
Calling on Compensation in Australian Call Centres
Authors: Crone Gary , Carey Lorraine , Dowling Peter
Published: November 2010

While there is a growing body of research on telephone call centre management in the U.K. and the U.S.A., empirical studies in Australia are at an embryonic stage. To date, most of the studies have focussed on the management of employee performance. The principal aim of this study was to provide data on current compensation practices in Australian call centres and to determine the extent of their strategic and best-practice orientation. A second aim was to explore whether the strategic management of compensation can help to balance the tension between commitment to customer service and commitment to employee motivation.

Using data collected through a mail questionnaire survey of telephone call centres operating in a range of industries in Australia, the paper explores the effect of compensation practices on employee performance, absenteeism and turnover. Following a review of the literature on call centre management and the literature on compensation strategies, the findings are presented. Key findings include: a) a significant negative correlation between annual salary and the number of calls handled by full-time customer service representatives (CSRs); b) a significant positive correlation between casual CSRs' pay rates and turnover; c) a significant negative correlation between full-time CSRs' pay and absenteeism; d) a highly significant difference between the compensation strategies currently practiced in Australian call centres and the strategies call centre managers think should be practiced and e) Australian call centre managers report their compensation strategies are not very effective in increasing performance or employee satisfaction.
Glacial cycles and solar insolation: the role of orbital, seasonal, and spatial variations
Authors: Kaufmann R. K. , Juselius K.
Published: November 2010

Abstract. We use a statistical model, the cointegrated vector autoregressive model, to evaluate the relative roles that orbital, seasonal, and spatial variations in solar insolation play in glacial cycles during the late Quaternary (390kyr – present). To do so, we estimate models of varying complexity and compare the accuracy of their in-sample simulations. Results indicate that variations in solar insolation associated with changes in Earth's orbit have the greatest explanatory power and that obliquity, precession, and eccentricity are needed to generate an accurate simulation of glacial cycles. Seasonal variations in insolation play a lesser role, while cumulative summer-time insolation has little explanatory power. Finally, solar insolation in the Northern Hemisphere generates the more accurate in-sample simulation of surface temperature while ice volume is simulated most accurately by solar insolation in the Southern Hemisphere.
Mid-level synoptic analysis of flood-generating systems in South-west of Iran (case study: Dalaki watershed river basin)
Authors: Sabziparvar A. A. , Parandeh A. , Lashkari H. , Yazdanpanah H.
Published: November 2010

Abstract. Flood is known as one of the most distractive natural disaster worldwide. Therefore, its prediction is of great importance from the socio-economical point of view. Despite the great improvement in computational techniques and numerical weather prediction approaches, so far, in Iran, an acceptable flood prediction method has not yet been introduced. The main aim of this study is to recognize and classify the patterns of synoptic systems leading to torrential rainfalls in a watershed basin located in south-west of Iran. In this research, 20 major floods characterized by high rainfall intensities and severe damage were selected. The pattern, extension, and the direction of movement of the selected synoptic maps from surface to 500 hPa pressure levels were identified. Furthermore, the position of cyclones, anti-cyclones and mid-level trough lines were carefully tracked and classified into different groups. The results show that the major severe floods occurring in Dalaki watershed river basin are mainly influenced by strengthening of the center of Sudan heat low (SHL) and the coincidence moisture feeding by the Indian Ocean and Mediterranean Sea. It was found that simultaneous merging of the SHL system and Mediterranean frontal system would intensify the flood intensities over the basin. The mean positions of high pressures, low pressures, the Red Sea trough lines and 1015 hPa isobars of the major floods are also discussed.
Reconstruction of the 1874 Santa Tecla's rainstorm in Western Catalonia (NE Spain) from flood marks and historical accounts
Authors: Balasch J. C. , Ruiz-Bellet J. L. , Tuset J. , Martín de Oliva J.
Published: November 2010

Abstract. The Santa Tecla flash flood, a very heavy event occurred in western Catalonia (NE Spain) in 1874, was reconstructed with hydraulic and hydrological modelling tools in three basins. The hydrograph obtained in a first step and the basin soil moisture information ultimately allowed the estimation of the range of the rainstorm magnitude which caused the flash flood. The reconstruction of historical floods has proved useful to improve the flood probability analysis, especially in ungauged basins.
The Influence of Deformation‐Induced Martensitic Transformations on the Mechanical Properties of Nanocomposite Cu‐Zr‐(Al) Systems
Authors: Fornell Jordina , Baró Maria Dolors , Suriñach Santiago , Gebert Annett , Sort Jordi
Published: November 2010

The microstructure and mechanical properties of Cu46.5Zr48.5Al5 and Cu50Zr50 rods are investigated. Cu50Zr50 is composed of nanostructured martensitic phases, while the Cu46.5Zr48.5Al5 alloy comprises micrometer‐sized dendrites (mainly austenitic phase) in an amorphous matrix. Both samples show considerable plasticity under compression and a work‐hardening ability. Martensitic phase transformations during deformation play a significant role with regard to the mechanical properties. Nanoindentation tests on the different phases comprising the alloys indicate that the amorphous matrix in Cu46.5Zr48.5Al5 is harder than the crystalline phases and has a less‐pronounced indentation‐size effect.
Cements with Embedded Living Microorganisms – A New Class of Biocatalytic Composite Materials for Application in Bioremediation, Biotechnology
Authors: Soltmann Ulrich , Nies Berthold , Böttcher Horst
Published: November 2010

Living bacteria (Rhodococcus ruber) and yeast (Saccharomyces cerevisiae) cells can be embedded within magnesium phosphate cement (MPC). The cements are prepared by the admixture of microorganisms to a water‐based slurry system of Mg3(PO4)2 powder and ammonium phosphate solution whereas the setting of the slurry occurs within few minutes. To test the biocatalytic activity of the embedded microorganisms the phenol degradation by R. ruber and the glucose conversion by S. cerevisiae are described. Embedded cells survived within the cements and remain active. However, the glucose or phenol consumption rate was clearly reduced after immobilization within the compact macroporous concrete matrix. By using leachable pore forming additives or by admixture of cellulose fibers the macroporous structure of the MPC can be improved. The bioactive composite material exhibits good mechanical and chemical stability. It can be used as new stable biocatalysts, e.g., for applications in bioremediation and biotechnology.
Catalytic Friedel–Crafts Acylation and Benzoylation of Aromatic Compounds Using Activated Hematite as a Novel Heterogeneous Catalyst
Authors: Sharghi Hashem , Jokar Mahboubeh , Doroodmand Mohammad Mahdi , Khalifeh Reza
Published: November 2010

Catalytic Friedel–Crafts acylation of benzene and unactivated benzenes such as chlorobenzene and nitrobenzene have been successfully carried out using activated hematite (α‐Fe2O3) as a new, heterogeneous and green catalyst. Sonication of neat α‐Fe2O3 in a water bath under air atmosphere at room temperature followed by heating at 200 °C, dramatically increase the activity of α‐Fe2O3. With the catalyst loading as low as 5.0 mol%, a wide variety of benzene derivatives were easily converted into the corresponding acylated products in a clean and high‐yielding acylation reaction. It was found that the activated α‐Fe2O3 could be efficiently recycled and reused several times by simple washing with ethyl acetate, this cannot be attained with most of the traditional catalysts.