bluuebunny/crossref_metadata_2025 huggingface dataset:
Light versus food supply as factors modulating niche partitioning in two pelagic mixotrophic ciliates
Authors: Modenutti Beatriz E. , Balseiro Esteban G. , Callieri Cristiana , Bertoni Roberto
Published: November 2010

We studied the vertical distribution of two mixotrophic ciliates, Ophrydium naumanni and Stentor araucanus in two contrasting summer seasons (strong vs. mild windy years) to determine whether differences in vertical mixing affect their success by changes in light availability for their endosymbiotic algae. Field experiments were done to evaluate the effect of light climate on the photosynthetic efficiency. To test for a potential overlap in food niche we studied prokaryote abundance and examined food vacuole contents of the ciliates, using the catalyzed reported deposition‐fluorescence in situ hybridization (CARD‐FISH). S. araucanus, a species resistant to ultraviolet radiation, was present in the epilimnion. In contrast, O. naumanni preferred the metalimnetic layers and was more abundant in years with deeper thermoclines. Variation in the diffuse extinction coefficient was significantly correlated with S. araucanus abundance, suggesting a shading effect of this dark ciliate. The expected extinction coefficient due to Stentor, measured by spectrophotometric analyses, did not differ from that observed in nature. O. naumanni was found to be photosynthetically efficient at low light intensities and susceptible to photoinhibition at epilimnetic light irradiances. Conversely, S. araucanus needed a high light supply to maintain endosymbiotic algal photosynthesis and was favored during years of relatively shallow thermocline and high epilimnetic mean irradiance. CARD‐FISH analysis revealed that O. naumanni fed on Archea, Eubacteria, and picocyanobacteria. In contrast, S. araucanus did not feed on prokaryotes. Based on these results, we suggest that light climate, created by temporal or spatial variations in thermocline depth, is a key factor modulating niche partitioning for mixotrophic ciliate species.
Influence of cell cycle phase on calcification in the coccolithophore Emiliania huxleyi
Authors: MÜller Marius N. , Antia Avan N. , LaRoche Julie
Published: November 2010

Calcification of the cosmopolitan coccolithophore species Emiliania huxleyi was investigated in relation to the cell division cycle with the use of batch cultures. With a 12 : 12 h light : dark cycle, the population was synchronised to undergo division as a cohort, simultaneously passing through the G1 (assimilation), S (DNA replication), and G2+M (cell division and mitosis) phases. Cell division was followed with the use of quantitative DNA staining and flow cytometry. Simultaneously, carbon‐14 (14C) assimilation in organic and inorganic carbon as well as cell abundance, size, and organic nitrogen content were measured at 2‐h intervals. In additional experiments, changes in calcification and cell cycle stages were investigated in nitrogen‐, phosphorus‐, and light‐limited cultures. Calcification occurred only during the G1 cell cycle phase, as seen by the very tight correlation between the percentage of cells in G1 and calcification during the dark period. When growth was limited by nitrogen, cells decreased in size, remained in the G1 phase, and showed a moderate increase in the cell‐specific calcite content. Limitation of growth by phosphorus, however, caused a significant increase in cell size and a dramatic increase in cellular calcite. Light limitation, by slowing the growth rate, prolonged the time cells spent in the G1 phase with a corresponding increase in the cellular calcite content. These results help explain the differing responses of coccolithophorid growth to nitrogen, phosphorus, and light limitation.
Effects of harmful algal blooms on competitors: Allelopathic mechanisms of the red tide dinoflagellate Karenia brevis
Authors: Prince Emily K. , Myers Tracey L. , Kubanek Julia
Published: November 2010

Because competitive interactions may have led to adaptations enabling bloom‐forming phytoplankton to dominate pelagic communities, we explored the allelopathic effects of one red tide dinoflagellate, Karenia brevis, on competing phytoplankton species. Exposure to waterborne compounds from natural 9;A. brevis blooms resulted in growth inhibition or death for four of five co‐occurring species tested, whereas compounds exuded by 9A. brevis cultures suppressed three of these same competitors (the diatoms Asterionellopsis glacialis and Skeletonema costatum and the dinoflagellate Prorocentrum minimum) plus one additional species (the dinoflagellate Akashiwo cf. sanguinea) that was unaffected by bloom exudates. 9A. brevis exudates lowered photosynthetic efficiency and damaged cell membranes of competing phytoplankton, but had no effect on competitor esterase activity, nor did they limit competitor access to iron. Overall, during blooms, 9A. brevis exudes potent allelopathic compounds, competitors vary in their susceptibility to 9A. brevis allelopathy, and 9A. brevis may achieve nearly monospecific blooms by lowering the photosynthetic efficiency of competitor species and increasing competitor membrane permeability, eventually resulting in competitor growth suppression or death.
Winter respiration of allochthonous and autochthonous organic carbon in a subarctic clear‐water lake
Authors: Karlsson Jan , Ask Jenny , Jansson Mats
Published: November 2010

We studied a small subarctic lake to assess the magnitude of winter respiration and the organic carbon (OC) source for this respiration. The concentration and stable isotopic composition (δ13C) of dissolved inorganic carbon (DIC) accumulating in the lake water under ice was analyzed over one winter (7 months). The DIC concentration increased and the δ13C of DIC decreased over time, with the greatest changes at the lake bottom. Winter respiration was 26% of annual respiration in the lake. Keeling plot analysis demonstrated that the δ13C of respired DIC varied spatially, high δ13C values occurring at shallow (2.5 m, 221.7‰%) compared with intermediate (4 m, 225.1‰) and deep (6 m, 227.8‰) locations in the lake. The variation in the δ13C of respired DIC was related to the variation in the δ13C of the sediments between locations, suggesting that sediment OC supported much of the winter respiration and that the dominant OC source for respiration was OC from benthic algae at shallow locations and settled OC, of predominately terrestrial origin, at deep locations. The respiration of OC from benthic algae constituted 55% of the winter respiration, equaling 54% of the primary production by benthic algae the previous summer. The study indicates the importance of temporal and spatial variation in respiration for the metabolism and net DIC production in unproductive high‐latitude lakes; both allochthonous and autochthonous carbon can contribute to winter DIC accumulation and, consequently, to spring CO2 emissions from lakes.
Nitrogen biogeochemistry of submarine groundwater discharge
Authors: Kroeger K. D. , Charette M. A.
Published: November 2010

To investigate the role of the seepage zone in transport, chemical speciation, and attenuation of nitrogen loads carried by submarine groundwater discharge, we collected nearshore groundwater samples (n = 328) and examined the distribution and isotopic signature (δ15N) of nitrate and ammonium. In addition, we estimated nutrient fluxes from terrestrial and marine groundwater sources. We discuss our results in the context of three aquifer zones: a fresh groundwater zone, a shallow salinity transition zone (STZ), and a deep STZ. Groundwater plumes containing nitrate and ammonium occurred in the freshwater zone, whereas the deep STZ carried almost exclusively ammonium. The distributions of redox‐cycled elements were consistent with theoretical thermodynamic stability of chemical species, with sharp interfaces between water masses of distinct oxidation : reduction potential, suggesting that microbial transformations of nitrogen were rapid relative to dispersive mixing. In limited locations in which overlap occurs between distribution of nitrate with that of ammonium and dissolved Fe2+, changes in concentration and in δ15N suggest loss of all species. Concurrent removal of NO3− and NH4+, both in freshwater and the deep STZ, might occur through a range of mechanisms, including heterotrophic or autotrophic denitrification, coupled nitrfication : denitrification, anammox, or Mn oxidation of NH4+. Loss of nitrogen was not apparent in the shallow STZ, perhaps because of short water residence time. Despite organic Cpoor conditions, the nearshore aquifer and subterranean estuary are biogeochemically active zones, where attenuation of N loads can occur. Extent of attenuation is controlled by the degree of mixing of biogeochemically dissimilar water masses, highlighting the critical role of hydrogeology in N biogeochemistry. Mixing is related in part to thinning of the freshwater lens before discharge and to dispersion at the fresh : saline groundwater interface, features common to all submarine groundwater discharge zones.
Observations of short‐circuiting flow paths within a free‐surface wetland in Augusta, Georgia, U.S.A.
Authors: Lightbody Anne F. , Avener Margaret E. , Nepf Heidi M.
Published: November 2010

Velocity heterogeneity is characteristic of wetland systems and results in some influent water remaining in the wetland for less than the expected residence time on the basis of volume and flow rate. This phenomenon, known as short‐circuiting, alters the distribution of the chemical and biological transformations that occur within the wetland. Field observations in a 1.5‐km2 constructed treatment wetland in Augusta, Georgia were used to quantify the size, distribution, velocity, and transport potential of fast flow paths, which cause short‐circuiting within wetlands. The flow paths were identified by a tracer study and velocity measurements. In each of the three cells examined, between three and six fast flow paths were found, most less than 4 m wide. These flow paths had an area‐averaged velocity on the order of 1 cm s‐1, at least 10 times the velocity observed where water passed through vegetation. Within different cells in this wetland, 20‐70% of the flow had a residence time less than one‐eighth of the nominal residence time. With this degree of short‐circuiting, uniform flow is a poor approximation for the flow through the wetland. In addition, tracer studies were used to make direct measurements of mixing within open‐water deep zones. Lateral mixing was sensitive to the direction of the wind. The average daily maximum temperature in the densely vegetated slow‐flow zones was 2.0°C cooler than that at the surface of the open water zones and 0.9uC cooler than that of the fast‐flow zones. The importance of short‐circuiting flow paths in this relatively simple wetland suggests that this phenomenon is likely of even greater significance in natural wetlands because they are typically much more complex.
Methylmercury cycling in estuarine sediment pore waters (Penobscot River estuary, Maine, USA)
Authors: Merritt Karen A. , Amirbahman Aria
Published: November 2010

Particulate mercury (Hg) sequestered in coastal marine sediments may be efficiently methylated to highly toxic methylmercury (MeHg), thereby placing exposed organisms at risk of MeHg bioaccumulation. The Penobscot River estuary in Maine, U.S.A., has been subject to Hg contamination from multiple industries including a recently closed chlor‐alkali production facility. Pore‐water depth profiles of total Hg, MeHg, and ancillary chemistry for the midestuary region were collected in August 2006 and June 2007. The profiles are divisible into kinetically discrete intervals with respect to MeHg dynamics. Dominant MeHg production occurs between ~2 and 7 cm in August and ~2 and 8 cm in June, with similar net MeHg production rates between 0.35 x 10‐20 and 4.9 x 10‐20 mol cm‐3 s‐1. A significant decrease in pore‐water MeHg concentration is observed in the vicinity of the sediment‐water interface (SWI). For August, a minimum MeHg consumption rate constant of 1.1 d‐1 may be estimated equal to the diffusive transport rate within a depth interval <0.75 cm. In June, the MeHg consumption zone extends from the SWI to a similar depth as for August, but the consumption rate is slower. MeHg consumption involves both sorption to sediment and demethylation. Intact sediment cores were incubated in the laboratory under various ponding regimes to study the influence of dominant geochemical parameters on in situ Hg methylation. The ponding regime changes the location of the redoxcline, which affects the depth of maximum methylation. Induced shoaling of the redoxcline brought about by the absence of any advective mixing of overlying water results in heightened MeHg efflux from the sediment.
13C dynamics in benthic algae: Effects of light, phosphorus, and biomass development
Authors: Hill W. R. , Fanta S. E. , Roberts B. J.
Published: November 2010

We performed three experiments in indoor streams and one experiment in a natural stream to investigate the effects of growth factors on δd13C levels in benthic microalgae. In the indoor streams, algae grown under conditions of high light and high phosphorus had δd13C values that were 16% higher than those in algae grown under conditions of low light and low phosphorus. Light effects were much stronger than phosphorus effects. The effects of both factors increased in strength as algal biomass accrued, and by the end of the experiments, algal δd13C and biomass were highly correlated. In the natural stream, algae exposed to direct sunlight were enriched 15% over shaded algae, corroborating the strong effect of light in the indoor streams. Growth factors such as light and nutrients probably reduce discrimination against δd13C (raising δd13C values) in benthic microalgae by causing CO2 depletion both within individual cells and within the assemblage matrix. However, because the most marked fractionation occurred in older and thicker assemblages, CO2 depletion within the assemblage matrix appeared to be more important than depletion within individual cells. In the absence of carbon‐concentrating mechanisms, elevated δd13C suggests that inorganic carbon may limit the growth of benthic algae. The extensive range of δd13C values (‐14‰ to ‐36‰) created by light and nutrient manipulations in this study easily encompassed the mean δd13C values of both C3 and C4 terrestrial plants, indicating the challenge aquatic ecologists face in identifying carbon sources for higher trophic levels when light and nutrient conditions vary.
Inorganic carbon uptake by Southern Ocean phytoplankton
Authors: Tortell Philippe D. , Payne Chris , Gueguen Celine , Strzepek Robert F. , Boyd Philip W. , Rost Björn
Published: November 2010

We report the results of laboratory and field studies examining inorganic carbon (Ci) utilization by Southern Ocean phytoplankton. Both in monospecific laboratory cultures of diatoms and Phaeocystis antarctica and in natural assemblages in the Ross Sea, Ci uptake by phytoplankton was dominated by direct HCO31 transport. The contribution of HCO31 transport to total Ci uptake ranged from 65% to 95%, with an overall average of ∼80%. There was no significant difference among diatoms and Phaeocystis in the extent of HCO31 transport. Extracellular carbonic anhydrase activity (eCA) was detected in eight of nine laboratory phytoplankton cultures and in all natural assemblages in the Ross Sea. The effective catalytic enhancement of HCO31 : CO2 interconversion ranged from 1.5‐ to 13‐fold (overall mean ∼4‐fold). Diatom‐dominated Ross Sea assemblages had significantly greater eCA levels than did Phaeocystis‐dominated assemblages. We found no strong correlations between Ci uptake parameters and in situ CO2 concentrations or chlorophyll a levels in the Ross Sea assemblages. Incubation experiments with natural assemblages showed that HCO31 uptake and eCA expression did not change significantly over an 8‐fold range in pCO2 (10.1‐81.1 Pa), although total short‐term C fixation rates increased under low CO2 conditions. Carbon‐concentrating mechanisms are widespread among Southern Ocean phytoplankton and constitutively expressed by natural assemblages in the Ross Sea.
Mate limitation in an estuarine population of copepods
Authors: Choi Keun-Hyung , Kimmerer Wim J.
Published: November 2010

We determined the probability of mating as a function of population density in the estuarine copepod Acartia hudsonica by combining experimental measurements with a simple model. Pairs of unmated copepods were confined in containers of various volumes to simulate variable population density, and experiments were run for 8, 16, and 24 h. Mating frequencies indicated that males search for females at an effective search volume rate of 0.34 ± 0.15 L h−1 or 8.2 ± 3.5 L d−1 and that males become ready to mate only after ~15 h exposure to the females. We applied these parameters in a simple population model to determine the critical density for zero population growth. With high egg production, zero mortality, and residence time of 60 d, the critical density for A. hudsonica was 0.01 m−3, at the low end of the range of observed population densities. Critical densities for less favorable conditions were well within the range of observed population densities, even allowing for the effects of aggregation. Thus, mate limitation in sexually reproducing organisms, or Allee effects, can cause negative density dependence in growth rate of these populations at low but realistic population densities. We applied these results to the introduction of exotic zooplankton via ships’ ballast water under various scenarios of initial dilution in harbors and subsequent conditions for reproduction and survival. Inocula resulting from the discharge of post‐exchange ballast water were often high enough to establish new resident populations.
Assessing the dynamics of dissolved organic matter (DOM) in coastal environments by excitation emission matrix fluorescence and parallel factor analysis (EEM‐PARAFAC)
Authors: Yamashita Youhei , Jaffé Rudolf , Maie Nagamitsu , Tanoue Eiichiro
Published: November 2010

The distributions of fluorescent components in dissolved organic matter (DOM) from Ise Bay, Japan, were determined by excitation emission matrix (EEM) fluorescence spectroscopy combined with parallel factor analysis (PARAFAC). Three terrestrial humic‐like, one marine humic‐like, and three non‐humic‐like fluorescent components were identified by PARAFAC, and the environmental dynamics of individual fluorescent components in the bay area were evaluated. The observed linear relationships between salinity and abundance of two of the three humic‐like components in the bay area indicate a terrestrial origin and conservative mixing behavior of these components. On the other hand, nonconservative mixing for the other terrestrial and the marine humic‐like components was observed, indicating that the sources of these were other than solely riverine inputs. Thus, in addition to riverine sources, this terrestrial humic‐like component may receive inputs from biogeochemical reworking of terrestrial DOM and/or particulate organic matter, while the most likely sources for the marine humic‐like component are estuarine biological activity and/or microbial reworking of plankton‐derived DOM. From the spatial distributions in the bay area as well as their relationships with salinity, two of the non‐humic‐like components were suggested to be of autochthonous estuarine origin and likely represent biologically labile components. Microbial degradation processes were suggested to be important factors driving the dynamics of another non‐humic‐like component. This study exemplifies the potential applicability of EEM‐PARAFAC in studies of fluorescent DOM dynamics in estuaries.
Physical processes and hypoxia in the central basin of Lake Erie
Authors: Rao Yerubandi R. , Hawley Nathan , Charlton Murray N. , Schertzer William M.
Published: November 2010

The circulation and exchange processes during summer stratification were examined using time‐series data of horizontal velocity, temperature, and dissolved oxygen profiles during 2004 and 2005 in the mid‐central basin of Lake Erie. The current and temperature spectra showed a prominent peak at around 18 h, indicating the presence of clockwise rotating inertial waves. The mean bottom currents were strong (>0.1 m s‐1) and flowed in opposite direction to winds because of the surface pressure gradient due to wind set‐up. The general range of horizontal exchange coefficients in the central basin is 0.2‐1.2 m2 s‐1. Vertical exchange coefficients varied from 1 × 10‐5 to 1 × 10‐4 m2 s‐1. The high values usually occurred in the surface layer because of surface winds. The source of turbulent energy is current shear due to near‐inertial oscillations in and above the thermocline and shearing stress due to the effect of mean currents and wave‐induced motions during energetic wind events at the lake bottom. During strong wind episodes significant wave‐induced currents were observed close to the bottom. The short‐term oxygen depletion rates varied considerably between +0.87 mg L‐1 d‐1 and ‐1.16 mg L‐1 d‐1 in 2004 mainly because of physical processes in the central basin. When the hypolimnion depth is sufficiently thick (4 m), shortterm changes in dissolved oxygen concentrations were partly due to vertical mixing and partly due to horizontal transport and mixing.
Preferential grazing of Oxyrrhis marina on virus infected Emiliania huxleyi
Authors: Evans Claire , Wilson William H.
Published: November 2010

We examined whether virus infection of Emiliania huxleyi with the lytic E. huxleyi‐specific virus, EhV‐86, influenced it's palatability to the heterotrophic dinoflagellate Oxyrrhis marina. E. huxleyi mortality was assessed by comparing changes in the algae's concentration between four different incubations: (1) Grazer O. marina plus an equal concentration of infected and healthy E. huxleyi prey (grazed‐infected); (2) the same equal concentration of healthy and infected E. huxleyi prey without grazer O. marina (infected); (3) healthy E. huxleyi prey (no infected cells) with grazer O. marina (grazed); and (4) healthy E. huxleyi prey alone (no grazer or infected cells; control). Grazing rates of O. marina increased in the presence of virus‐infected E. huxleyi prey. An adapted plaque assay protocol revealed that the amount of infected cells in grazed‐infected cultures was approximately one‐quarter (0.28) of that observed in infected (minus grazer) controls. Given that these assays were normalized to cell number, they demonstrate that O. marina was preferentially feeding on virus‐infected E. huxleyi over their healthy counterparts. The effects of marine viruses may have been misinterpreted since the likelihood of them being grazed during infection has not been previously considered. Preferential grazing of infected cells in the ocean would sequester more carbon in particulate form, making it available to higher trophic levels. Consequently, these results should be taken into consideration when modeling the ocean carbon budget.
Air‐sea CO2 flux variability in frontal regions of the Southern Ocean from CARbon Interface OCean Atmosphere drifters
Authors: Boutin J. , Merlivat L. , HÉnocq C. , Martin N. , SallÉe J. B.
Published: November 2010

Nine CARbon Interface OCean Atmosphere (CARIOCA) drifters were deployed in the Southern Ocean (south of the subtropical front, STF) between 2001 and 2006. They recorded 65 months of measurements in all seasons between 57°S and 40°S. Hydrological fronts detected by altimetry indicate that one buoy explored the polar zone (PZ) of the Atlantic Ocean and the western Indian Ocean; the remaining buoys explored the northern and southern parts of the subantarctic zone (SAZ) from the mid‐Indian Ocean (73°E) to the eastern Pacific Ocean (112°W). The air‐sea CO2 fluxes along the buoy trajectories are primarily driven by the spatial variability of the fugacity of CO2 in seawater, fCO2: in the SAZ, they vary between 21.1 and 24.2 mol m−2 yr−1, and the largest sinks occur close to the STF; in the PZ they vary between 21.6 and 0.6 mol m−2 yr−1. When spatially extrapolated over each region, the yearly fluxes amount to 20.8 Pg C yr−1 in the SAZ and to 20.1 Pg C yr−1 in the PZ, with very small seasonal variation. In winter‐spring, the sea‐surface salinity and sea‐surface temperature indicate mixing with deep water close to the subantarctic front and an episodic signature of north Atlantic deep water close to the polar front (PF). These events are associated with fCO2 close to equilibrium. On a small scale (of a few km), close to the STF, fCO2 variations of 1‐2 Pa (10‐20 µatm) are associated with the presence of compensated mixed layers.
Monsoon effects in the Bay of Bengal inferred from profiling float‐based measurements of wind speed and rainfall
Authors: Riser S. C. , Nystuen J. , Rogers A.
Published: November 2010

Both rainfall and wind have acoustic signatures that can be discerned at depths in the ocean well below the sea surface. We examine observations of rainfall and wind speed collected at a depth of 600 m in the Bay of Bengal from a specially modified Argo profiling float. In addition to the normal Argo sensors, the float carried a passive acoustic listener sensor package that monitored the spectrum of acoustic noise along the float trajectory at intervals of a few minutes and used a set of existing algorithms to estimate the wind speed and rainfall rate from these noise spectra. A comparison of the acoustically derived wind speed and rainfall estimates with analogous satellite‐derived data (rainfall from the Tropical Rainfall Measuring Mission and QwikScat winds) showed general agreement in both cases, although the float‐based measurements were representative of conditions a few kilometers around the float, whereas the remotely sensed observations were smoothed over much larger length scales. The strong monsoon signal in the Bay of Bengal is clearly present in the float‐based wind and rainfall data. The near‐surface salinity measured by the float varied because of both rainfall events and the proximity to strong coastal runoff from major rivers. The float profiles of temperature and salinity in the upper ocean, and the effects of wind and rainfall, were simulated in a version of the Price‐Weller‐Pinkel mixed‐layer model, which showed that the direct effects of most rainfall events are concentrated in the upper 20‐30 m of the water column.
Plume dispersion on a fringing coral reef system
Authors: Jones Nicole L. , Lowe Ryan J. , Pawlak Geno , Fong Derek A. , Monismith Stephen G.
Published: November 2010

A field program was implemented on a fringing reef located on Oahu, Hawaii, to investigate the dispersion characteristics of near‐bed dye plumes, tracked using an autonomous underwater vehicle (AUV) with an onboard fluorometer. The combination of moored and AUV‐based measurements collected synchronously in this study allowed us not only to observe the dispersion characteristics of individual plumes, but importantly to isolate the flow structures directly responsible for dispersion under a variety of forcing conditions. The evolution of several plumes was observed, each influenced by different wave (surface and internal), current, and stratification conditions. The observed dispersion was caused by both turbulent dispersion and plume meandering. Lateral turbulent dispersion coefficients were roughly an order of magnitude greater than previous observations on sandy beach sites, which is likely attributable to the enhanced surface wave‐induced mixing and the large physical roughness of the reef. For a large portion of the 2‐week experiment the effects of meandering dominated over turbulent dispersion (on average 1.5 times greater). The meandering was the result of large‐scale cross‐reef current variability. Moored thermistor chain data on the forereef suggest that the source of this cross‐reef flow variability were packets of solitary waves that accompanied the propagation of baroclinic bores up the reef slope. Baroclinic bores dissipated before they reached the inner reef when surface wave conditions were large, resulting in the reduction of plume meandering during this period.
Linking allochthonous dissolved organic matter and boreal lake sediment carbon sequestration: The role of light‐mediated flocculation
Authors: von Wachenfeldt Eddie , Sobek Sebastian , Bastviken David , Tranvik Lars J.
Published: November 2010

We measured flocculation of dissolved organic carbon (DOC) in the water from a humic lake (DOC = 14.9 mg C L‐1) and from an adjacent mire (DOC = 25.7 mg C L‐1), in in situ enclosure experiments with different light regimes. Light stimulated the formation of organic particles in both waters, and organic particle formation was observed at all incubation depths, even in the dark controls. Production of phytoplankton biomass was negligible, and allochthonous DOC was the most important precursor of the sinking particles. 8‐22% and 25‐ 60% of the loss of DOC in lake and mire water, respectively, could be accounted for by flocculation. Depthintegrated flocculation based on the enclosure experiments was 14.7 mg C m‐2 d‐1. Lake‐water DOC concentration and water color has been increasing during the last decade, and sediment trap studies show that gross sedimentation of organic carbon also increased. Thus flocculation of allochthonous DOC, stimulated by light, constitutes a pathway for the sequestration of carbon in lake sediments.
Tracing terrestrial organic matter by δ34S and δ13C signatures in a subarctic estuary
Authors: Alling Vanja , Humborg Christoph , Mörth Carl-Magnus , Rahm Lars , Pollehne Falk
Published: November 2010

A key issue to understanding the transformations of terrestrial organic carbon in the ocean is to disentangle the latter from marine‐produced organic matter. We applied a multiple stable isotope approach using δ34S and δ13C isotope signatures from estuarine dissolved organic matter (DOM), enabling us to constrain the contribution of terrestrial‐derived DOM in an estuarine gradient of the northern Baltic Sea. The stable isotope signatures for dissolved organic sulfur (δ34SDOS) have twice the range between terrestrial and marine end members compared to the stable isotope signatures for dissolved organic carbon (δ13CDOC); hence, the share of terrestrial DOM in the total estuarine DOM can be calculated more precisely. DOM samples from the water column were collected using ultrafiltration on board the German RV Maria S Merian during a winter cruise, in the Bothnian Bay, Bothnian Sea, and Baltic proper. We calculated the terrestrial fraction of the estuarine DOC (DOCter) from both δ13CDOC and δ34SDOS signatures and applying fixed C: S ratios for riverine and marine end members to convert S isotope signatures into DOC concentrations. The δ34SDOS signature of the riverine end member was +7.02‰, and the mean signatures from Bothnian Bay, Bothnian Sea, and Baltic proper were +10.27, +12.51, and +13.67‰, respectively, showing an increasing marine signal southwards (δ34SDOS marine end member 5 18.1‰). These signatures indicate that 87‰, 75‰, and 67‰, respectively, of the water column DOC is of terrestrial origin (DOCter) in these basins. Comparing the fractions of DOCter in each basin—that are still based on few winter values only—with the annual river input of DOC, it appears that the turnover time for DOCter in the Gulf of Bothnia is much shorter than the hydraulic turnover time, suggesting that high‐latitude estuaries might be efficient sinks for DOCter.
Modeling flow in coral communities with and without waves: A synthesis of porous media and canopy flow approaches
Authors: Lowe Ryan J. , Shavit Uri , Falter James L. , Koseff Jeffrey R. , Monismith Stephen G.
Published: November 2010

Both canopy flow and porous media theories have been developed independent of one another to predict flow through submerged porous structures. These approaches are very similar, albeit with some key differences in how canopy resistance forces are parameterized. Canopy models provide a means of parameterizing the shear stresses that occur at the top of the canopy, whereas porous media models can often provide a simpler and more tractable way of parameterizing turbulent form drag based on simple morphological metrics and empirical relationships already in the hydrology literature. We developed a set of equations combining aspects of both models and applied this hybridized model to predict the flow structure within an experimental canopy formed by the branching coral Porites compressa, using model parameter values obtained from the literature. Results from the model predictions agreed well with direct measurements of flow speed and flow forces derived from particle image velocimetry under conditions of both unidirectional and wave‐driven oscillatory flow.
Sediment‐mediated suppression of herbivory on coral reefs: Decreasing resilience to rising sea‐levels and climate change?
Authors: Bellwood David R. , Fulton Christopher J.
Published: November 2010

We describe a mechanistic basis for maintaining an alternative degraded stable state on coral reefs: sediment‐laden algal turfs. Using remote underwater video cameras we quantified rates of herbivory by coral reef fishes on epilithic algal turfs with natural and experimentally reduced sediment loads. Removal of sediment increased overall fish feeding rates 3.8‐fold, and resulted in a decrease in mean algal turf length of 64% within 4 h. After 4 h, sediment accumulated in the treatment plots, but only returned to 41% of the original depth. A total of 20 species actively fed on the sediment removal plots, compared with 12 species in control plots. Of the five numerically abundant herbivorous fish species, all increased feeding by at least 225% in the absence of sediment. Only juvenile Scarus spp. fed to any extent (28% of bites) on control plots. We suggest that naturally occurring sediment loads in epilithic algal turfs can suppress herbivory and that sediment‐laden algal turfs may be an alternative stable state on coral reefs. This may provide a mechanistic basis for the geological evidence of a sediment‐induced turn‐off of coral reef growth. With projected global sea‐level rises due to climate change, reef‐based sediment loads may be a critical factor in differentiating the relative resilience of coral reefs and identifying reef ecosystems that are at highest risk to rising sea levels.
Effectiveness of Cheek and Jaw Support to Improve Feeding Performance of Preterm Infants
Authors: Hwang Yea-Shwu , Lin Chyi-Her , Coster Wendy J. , Bigsby Rosemarie , Vergara Elsie
Published: November 2010

OBJECTIVE. We examined the effects of cheek and jaw support on the feeding ability of inefficient feeders born prematurely.

METHOD. Twenty preterm infants served as their own controls. Each infant received either intervention (feeding with oral support) or control (feeding without oral support) for 2 consecutive feedings per day on 2 consecutive days.

RESULTS. Infants displayed a greater intake rate during the intervention feedings, both during the first 5 min (p = .046) and throughout the entire feeding (p = .023). The percentage of leakage during the first 5-min feeding was smaller in the intervention condition than in the control condition (p = .040). No significant differences were found between the two conditions in the sucking, physiological, and alertness variables.

CONCLUSION. Findings confirm oral support as a safe and effective strategy to improve the feeding performance of preterm infants who are poor feeders.
Pattern Matching Organisational Cultures
Authors: Burchell Noel , Kolb Darl
Published: November 2010

There are numerous methods of organisational cultural analysis, ranging from quantitative surveys with structured questions that are relatively quick to complete, to in-depth qualitative ethnographic studies that are more thorough, yet very time-consuming. Concept Mapping and Pattern Matching are two research techniques that combine the strengths of interpretive (emic) methods with some of the efficiencies of survey (etic) research. While Trochim's Concept Mapping technique has been previously employed in a study of organisational culture, Pattern Matching has not. The results of a study employing Trochim's Pattern Matching technique suggest that it can be a useful tool for an in-depth analysis of organisational culture. In particular, visual pattern ‘matches’ and ‘mismatches’ of cultural elements were portrayed for interpretation.
Board Structure and Firm Performance: Evidence from Australia
Authors: Bonn Ingrid
Published: November 2010

The influence of corporate governance on firm performance has been discussed for a number of years, but mainly in a United States and European business context. This article investigates the composition of boards of directors in large Australian firms and analyses whether board structure has an impact on performance, as measured by return on equity and market-to-book value ratio. The results showed that outsider ratio and female director ratio were positively associated with firm performance, whereas board size and directors' age had no influence on firm performance.
Substrate effects in the photoenhanced ozonation of pyrene
Authors: Styler S. A. , Loiseaux M.-E. , Donaldson D. J.
Published: November 2010

Abstract. We report the effects of actinic illumination on the heterogeneous ozonation kinetics of solid pyrene films and pyrene adsorbed at air-octanol and air-aqueous interfaces. Upon illumination, the ozonation of solid pyrene films and pyrene at the air-aqueous interface proceeds more quickly than in darkness; no such enhancement is observed for pyrene at the air-octanol interface. Under dark conditions, the reaction of pyrene at all three interfaces proceeds via a Langmuir-Hinshelwood-type surface mechanism. In the presence of light, Langmuir-Hinshelwood kinetics are observed for solid pyrene films but a linear dependence upon gas-phase ozone concentration is observed at the air-aqueous interface. We interpret these results as evidence of the importance of charge-transfer pathways for the ozonation of excited-state pyrene. The dramatically different behaviour of pyrene at the surface of these three simple reaction environments highlights the difficulties inherent in representing complex reactive surfaces in the laboratory, and suggests caution in extrapolating laboratory results to environmental surfaces.
Investigation of trends in synoptic patterns over Europe with artificial neural networks
Authors: Michaelides S. , Tymvios F. , Charalambous D.
Published: November 2010

Abstract. The present study is a comprehensive application of a methodology developed for the classification of synoptic situations using artificial neural networks. In this respect, the 500 hPa geopotential height patterns at 12:00 UTC (Universal Time Coordinated) determined from the reanalysis data (ERA-40 dataset) of the European Centre for Medium range Weather Forecasts (ECMWF) over Europe were used. The dataset covers a period of 45 years (1957–2002) and the neural network methodology applied is the SOM architecture (Self Organizing Maps). The classification of the synoptic scale systems was conducted by considering 9, 18, 27 and 36 synoptic patterns. The statistical analysis of the frequency distribution of the classification results for the 36 clusters over the entire 44-year period revealed significant tendencies in the frequency distribution of certain clusters, thus substantiating a possible climatic change. In the following, the database was split into two periods, the "reference" period that includes the first 30 years and the "test" period comprising the remaining 14 years.
A robust method to identify cyclone tracks from gridded data
Authors: Kreienkamp F. , Spekat A. , Enke W.
Published: November 2010

Abstract. A system to derive tracks of barometric minima is presented. It is deliberately using coarse input data in space (order of 2°×2°) and time (6-hourly to daily) as well as information from just one geopotential level. It is argued that the results are, for one robust in the sense of an assumption of the IMILAST Project that the use of as simple as possible metrics should be strived for and for two tailored to the input from reanalyses and GCMs. The methodology presented is a necessary first step towards an automated storm track recognition scheme which will be employed in a second paper to study the future development of atmospheric dynamics in a changing climate. The process towards obtaining storm tracks is two-fold. In its first step cyclone centers are being identified. The performance of this step requires the existence of closed isolines, i.e., a topology in which a grid-point is surrounded by neighbours which all exhibit higher geopotential. The usage of this topology requirement as well as the constraint of coarse data may lead, though, to limitations in identifying centers in geopotential fields with shallow gradients that may occur in the summer months; moreover, some centers may potentially be missed in case of a configuration in which a small scale storm is located at the perimeter of a deep and very large low (a kind of "dent in a crater wall"). The second step of the process strings the identified cyclone centers together in a meaningful way to form tracks. By way of several examples the capability to identify known storm tracks is shown.
Temperature response functions introduce high uncertainty in modelled carbon stocks in cold temperature regimes
Authors: Portner H. , Bugmann H. , Wolf A.
Published: November 2010

Abstract. Models of carbon cycling in terrestrial ecosystems contain formulations for the dependence of respiration on temperature, but the sensitivity of predicted carbon pools and fluxes to these formulations and their parameterization is not well understood. Thus, we performed an uncertainty analysis of soil organic matter decomposition with respect to its temperature dependency using the ecosystem model LPJ-GUESS. We used five temperature response functions (Exponential, Arrhenius, Lloyd-Taylor, Gaussian, Van't Hoff). We determined the parameter confidence ranges of the formulations by nonlinear regression analysis based on eight experimental datasets from Northern Hemisphere ecosystems. We sampled over the confidence ranges of the parameters and ran simulations for each pair of temperature response function and calibration site. We analyzed both the long-term and the short-term heterotrophic soil carbon dynamics over a virtual elevation gradient in southern Switzerland. The temperature relationship of Lloyd-Taylor fitted the overall data set best as the other functions either resulted in poor fits (Exponential, Arrhenius) or were not applicable for all datasets (Gaussian, Van't Hoff). There were two main sources of uncertainty for model simulations: (1) the lack of confidence in the parameter estimates of the temperature response, which increased with increasing temperature, and (2) the size of the simulated soil carbon pools, which increased with elevation, as slower turn-over times lead to higher carbon stocks and higher associated uncertainties. Our results therefore indicate that such projections are more uncertain for higher elevations and hence also higher latitudes, which are of key importance for the global terrestrial carbon budget.
Water and nutrient balances in a large tile-drained agricultural catchment: a distributed modeling study
Authors: Li H. , Sivapalan M. , Tian F. , Liu D.
Published: November 2010

Abstract. This paper presents the development and implementation of a distributed model of coupled water nutrient processes, based on the representative elementary watershed (REW) approach, to the Upper Sangamon River Basin, a large, tile-drained agricultural basin located in central Illinois, mid-west of USA. Comparison of model predictions with the observed hydrological and biogeochemical data, as well as regional estimates from literature studies, shows that the model is capable of capturing the dynamics of water, sediment and nutrient cycles reasonably well. The model is then used as a tool to gain insights into the physical and chemical processes underlying the inter- and intra-annual variability of water and nutrient balances. Model predictions show that about 80% of annual runoff is contributed by tile drainage, while the remainder comes from surface runoff (mainly saturation excess flow) and subsurface runoff. It is also found that, at the annual scale nitrogen storage in the soil is depleted during wet years, and is supplemented during dry years. This carryover of nitrogen storage from dry year to wet year is mainly caused by the lateral loading of nitrate. Phosphorus storage, on the other hand, is not affected much by wet/dry conditions simply because the leaching of it is very minor compared to the other mechanisms taking phosphorous out of the basin, such as crop harvest. The analysis then turned to the movement of nitrate with runoff. Model results suggested that nitrate loading from hillslope into the channel is preferentially carried by tile drainage. Once in the stream it is then subject to in-stream denitrification, the significant spatio-temporal variability of which can be related to the variation of the hydrologic and hydraulic conditions across the river network.
Introduction to the Theory and Instrumentation for Vibrational Spectroscopy
Authors: Griffiths Peter R.
Published: November 2010

The theory of infrared and Raman spectroscopy is introduced, including factors that control the frequency, intensity, and shape of bands in these spectra. Factors that determine the quantitative aspects of vibrational spectroscopy, including Beer's law, the complex refractive index, and the effect of polarized radiation, are discussed. Finally, the instrumentation for mid‐infrared, near‐infrared, and Raman spectroscopy is discussed.
Vibrational Spectroscopy: Sampling Techniques and Fiber‐Optic Probes
Authors: Chalmers John M. , Griffiths Peter R.
Published: November 2010

This chapter focuses on the sampling techniques, their attributes and limitations, associated with the vibrational spectroscopic analysis and characterization of foodstuffs and beverages. Near‐ and mid‐infrared techniques covered include transmission, internal, external and diffuse reflection, interactance, and photoacoustic spectroscopy. Both macro‐ and micro‐sampling infrared and Raman spectroscopic techniques are discussed, and mapping and imaging approaches for each considered. The chapter closes with a discussion on the use and type of fiber‐optic probes with near‐ and mid‐infrared and Raman spectroscopy.