bluuebunny/crossref_metadata_2025 huggingface dataset:
Abiotic transformations of iron and phosphate in humic lake water revealed by double‐isotope labeling and gel filtration
Authors: de Haan Henk , Jones Roger I. , Salonen Kalevi
Published: April 2010

Abiotic transformations of Fe and PO43− in humic water from Finnish forest lakes were studied by Sephadex G‐100 gel filtration following incubation of filtered (0.2 µm) epilimnetic water samples to which both 55FeCl3·6H2O and 32PO43− had been added. The simultaneous movement of 55Fe and 32P to higher molecular‐weight fractions (10,000–20,000 MW) depended on the presence of dissolved humic substances (DHS). In the absence of DHS almost all 55Fe, probably as inorganic hydrolyzed iron particles, sorbed to the Sephadex. The binding of 55Fe by DHS was not affected by increasing the natural ionic strength (I = ∼3 × 10−4 M) by a factor of 102. In the absence of quasi‐equilibrium between free and DHS‐bound 32PO43−, the DHS‐Fe‐PO43− complex readily released 32PO43−‐P. Compared to the 32P binding, 55Fe binding was rapid. More than 20% of the Fe had been bound after only 1 min, whereas for labeled PO43− this percentage was reached only after 24 h.
Variability of diatom concentrations and accumulation rates in sediments of a small lake basin
Authors: Anderson N.J.
Published: April 2010

Diatom biostratigraphy was analyzed for 10 sediment cores covering a range of water depths in Lough Augher, Northern Ireland. Cores were zoned to permit correlation and transfer of a 210Pb chronology and calculation of diatom accumulation rates. There were clear differences in relative frequency of planktonic microfossils between littoral (<6‐m water depths) and profundal cores, but all cores gave a similar history of the eutrophication of the lake. Deep‐water cores, however, provided a clearer and higher resolution record. Diatom concentrations and percentages were horizontally nonuniform, contradicting the assumption that lake and sediment mixing creates homogeneous microfossil assemblages before deposition. Accumulation rates also showed considerable variation over time. Relative accumulation rates indicate that no single core accurately reflects the mean accumulation rate for the whole basin. Before 1900, diatoms were focused into deeper water, but after ∼1940 the pattern of diatom deposition and accumulation rates began to change. Redistribution of diatoms into the deepest part of the basin was reduced, perhaps due to reduced resuspension from the increasing influence of fringing macrophyte beds.
Greigite and the magnetic properties of sediments
Authors: Hilton J.
Published: April 2010

X‐ray diffraction spectra of freeze‐dried sediments from a lake in the English Lake District positively identified the presence of greigite, a magnetic iron sulfide (Fe3S4) mineral. The sediments also show considerable loss of magnetic intensity when wet samples are allowed to oxidize. Several hypotheses have been proposed elsewhere to explain the intensity loss, but an assessment of the evidence suggests that oxidation of greigite is responsible in these sediments.

Data from several lakes and from laboratory experiments are used to deduce the environmental requirements for greigite formation. These conditions of high labile C concentrations, good sources of labile Fe and S, and an oscillating oxycline depth in the sediments are likely to be found only in mono‐ or dimictic eutrophic lakes, estuaries, and salt marshes and are unlikely to be found in meromictic lakes, unstratified lakes, oligotrophic lakes, or deep‐sea sediments.
Evaluation ofbiologically harmful ultraviolet radiation in Antarctica with a biological dosimeter designed for aquatic environments
Authors: Karentz Deneb , Lutze Louise H.
Published: April 2010

A biological dosimeter has been developed for use in aquatic environments. This method is based on the sensitivity of a DNA repair‐deficient strain of Escherichia coli (CSR06) to ultraviolet (UV) radiation. The dosimeter permits evaluation of the penetration of biologically active UV radiation within a water column, reflecting the potential effect of exposure over selected time intervals. With the use of various filters, the biological dosimeter can discriminate between the effects of UV‐B (280–320 nm) and UV‐A (320–400 nm) or other selected portions of the solar UV spectrum. During springtime ozone depletion over the Antarctic in 1988, a general relationship was observed between stratospheric ozone concentration and the contribution of incident solar UV‐B radiation to lethality of dosimeter cells. The use of dosimeters within the water column indicated that significant amounts of UV‐B can be transmitted to a depth of 10 m and biological effects of UV could be detected to 20 and 30 m. Biological dosimeters may provide a means of standardizing in‐water UV measurements across all types of aquatic habitats and at any geographical location.
A comparison of the acidification efficiencies of nitric and sulfuric acids by two whole‐lake addition experiments
Authors: Rudd John W. M. , Kelly C. A. , Schindler D. W. , Turner M. A.
Published: April 2010

The acidification efficiencies of nitric and sulfuric acids were compared for 5 yr by separate experimental additions of the acids to the partitioned north and south basins of Lake 302. In the epilimnion, nitric acid was 70% as efficient as sulfuric acid in reducing alkalinity. On a whole‐lake basis, acidification by nitric acid was about half as efficient as by sulfuric acid. In‐lake processes removed 70 and 57% of the added nitric and sulfuric acids.

Before acidification, algal uptake and sediment SO42− uptake were of about equal importance in terms of in‐lake SO42− removal. NO3− was primarily removed by algal uptake and sedimentation. After acidification, algal uptake of NO3− and SO42− did not change, but rates of uptake in the sediments by bacterial processes increased and dominated in‐lake removal.

Nitric acid acidified the north basin because the acid additions exceeded the capacity of all biological removal processes. Algal uptake and sedimentation of N could not increase in proportion to increases in NO3− because of P limitation. Sediment‐denitrification rates increased tremendously (∼40‐fold) but only removed a portion of the incoming NO3− because denitrification was limited by the rate of transport to the sediment‐water interface.
Nitrification in reef corals
Authors: Wafar Mohideen , Wafar Sayeeda , David Jason J.
Published: April 2010

N‐Serve blockage of NH4+ oxidation showed that nitrification in reef corals is quantitatively important. Average NO3− production was 9.4±6.0 nmol (mg coral tissue N)−1 h−1 (mean ± 1 SE; n = 12), equivalent to 17% of the NH4+ consumption and 21% of the uptake by zooxanthellae showing an effective competition for NH4+ by nitrifiers. NH4+ utilization rates were equal to inorganic N production rates, and NO3− production rates were equal to NO3− uptake rates by zooxanthellae, suggesting close coupling betweenpocesses. Density nitrifying bacteria associated with living corals may vary from 4 to 260 × 103 cells (mg coral tissue N)−1.
A simple pore‐water sampler for coarse, sandy sediments of low porosity
Authors: Saager Paul M. , Sweerts Jean‐Pierre , Ellermeijer Hans J.
Published: April 2010

A simple, inexpensive, and highly efficient centrifuge tube allows nearly complete extraction of interstitial water from coarse, sandy sediments with porosities as low as 32%. The method is fast (5 min), efficient (55–92% of the available water is obtained), reliable, and can be peformed on board ship at only 1,500 × g. The efficiency of the method permits a high sampling resolution (millimeter scale). The centrifuge tube is made of polyethylene and can be used for trace metal determinations after cleaning with acid. Due to a built‐in filter, pore waters are clean and need not be filtered afterward, thus reducing the risk of contamination and possible oxidation artifacts.
Interannual fluctuations in primary production: Direct physical effects and the trohic cascade at Castle Lake, California
Authors: Jassby Alan D. , Powell Thomas M. , Goldman Charles R.
Published: April 2010

Direct physical effects and cascading trophic interactions operate together to determine interannual variability in the seasonal pattern of primary productivity at Castle Lake, California. Principal component analysis was used to investigate the depth‐time distributions of productivity for summers 1961–1986. Two characteristic patterns were found, together accounting for 60–70% of the year‐to‐year variability. The first pattern corresponds to the deep productivity maximum that forms in the hypolimnion in June and July. Variability in this first pattern arises from the direct effects on phytoplankton populations of year‐to‐year changes in timing of ice breakup and hydraulic flushing in spring. The first pattern is unusually strong or weak, compared to the long‐term average, during the phenomenon of El Niño‐Southern Oscillation. A second characteristic pattern corresponds to the mixed‐layer productivity maximum that develops in August and September. Variability in this second pattern arises from trophic interactions at higher levels: rainbow trout feed on late‐summer Daphnia rosea populations, which in turn graze on the mixed‐layer algal community. In addition, some of the variability in the rainbow trout population arises from year‐to‐year differences in angling pressure from humans. These results demonstrate how interannual variability in an ecosystem property (primary productivity) can be controlled by forces acting simultaneously through the top and the base of the food web.
Bacterial exopolymer utilization by a harpacticoid copepod: A methodology and results
Authors: Decho Alan W. , Moriarty David J. W.
Published: April 2010

Exopolymer mucus secretions of bacteria and diatoms are potential foods for benthic animals. These secretions are coincidently ingested by animals during consumption of microbial cells and sediments. The utilization of microbial secretions was investigated with exopolymer derived from a marine bacterium (Pseudomonas sp.) from seagrass beds and a harpacticoid copepod Laophonte sp. from the same habitat. A new technique was developed to examine ingestion, absorption, and absorption efficiencies of these bacterial secretions by consumers. Exopolymer mucus (from the bacterium in stationary phase) was labeled with 14C, collected, purified, and bound onto bacterium‐sized beads. The exopolymer slime coating mimicked the coatings associated with many marine bacteria. Results from feeding experiments where the coated beads were mixed with sediment demonstrated that the mucus‐exopolymer secretions of bacteria were ingested and utilized by Laophonte sp. Absorption efficiencies, determined directly, were > 80% in the presence of other food resources, indicating that the exopolymer is potentially a highly labile C resource for this animal.
Dynamic behavior of suspended sediment concentrations in a shallow lake perturbed by episodic wind events
Authors: Luettich Richard A. , Harleman Donald R. F. , SomlyÓdy LÁszlÓ
Published: April 2010

Field experiments were conducted in Lake Balaton, a large (surface area, 600 km2) but shallow (mean depth, 3.2 m) lake in Hungary, to quantify the resuspension and deposition of bottom sediment due to episodic storm events. Measurements were made of windspeed and direction, surface waves, mean water velocity, and suspended sediment concentration. During significant wind events, the computed bottom stress due to surface waves dominated that due to the mean current, and therefore surface waves were assumed to be the major cause of sediment resuspension. A simple model for the depth‐averaged suspended sediment concentration based on surface wave height was calibrated with about 10 h of data collected during one storm event and verified against 15 d of data collected at the same site. The success of the suspended sediment model, which assumes that the bottom sediment was noncohesive, is surprising since the bottom material was composed predominantly of sediment in the clay and fine‐silt size ranges. This fit may indicate the presence of a thin surface layer of loosely bound sediment that is continuously involved in resuspension. The suspended sediment model could easily be integrated into a water quality model (e.g. to predict light attenuation), provided that lateral transport is negligible, or it could be used to provide the bottom boundary condition for a more general suspended sediment transport model in which advective transport is included.
Light control of evening vertical migrations by Chaoborus punctipennis larvae
Authors: Haney James F. , Craggy Althea , Kimball Kenneth , Weeks Frank
Published: April 2010

Light control of vertical migration was examined with sonar recordings of the evening migration of Chaoborus punctipennis larvae. Frequently, a slow, upward drift in the afternoon preceded the rapid ascent of larvae. Movement out of the sediments was not consistently related to a fixed light intensity or rate of relative light change. Light intensities were variable at the initiation of and during the upward migration, whereas the beginning of rapid ascent was closely correlated with the timing of a relative light change of 1.7 ×10−1 s−1. The close relationship between the rate of relative change in light intensity and the rate of upward movement including the afternoon drift supports the stimulus‐velocity hypothesis that once larvae leave the sediments the speed and direction of the migration pattern is primarily regulated by relative light changes. Second‐ and third‐instar larvae migrated at higher light intensities than fourth instars, but did not differ in their rate of movement in relation to light change.
Trophic interactions of Leptodora in Lake Mendota
Authors: Lunte Cynthia C. , Luecke Chris
Published: April 2010

Using a series of field enclosure experiments, we investigated the trophic dynamics of Leptodora kindtii in Lake Mendota. Leptodora fed on both small and large Daphnia as well as on Diaphanosoma, Conochilus, and copepod nauplii. These results were combined with field data and a computer simulation model to examine how various densities of Leptodora might affect the densities of Daphnia and other zooplankton in Lake Mendota. Leptodora could account for all of the mortality calculated for Daphnia galeata mendotae in late June to early July. Reduced numbers minimized Leptodora’s potential, however, for direct control of Daphnia earlier in the year. The simulation model demonstrated that, because the dominant planktivorous fish in the lake fed on both Leptodora and daphnids, a decrease in planktivorous fish could result in higher Daphnia mortalities due to increased predation by Leptodora.
In situ filtering rates of Cladocera: Effect of body length, temperature, and food concentration
Authors: Mourelatos Spiros , Lacroix GÉrard
Published: April 2010

The individual filtering rates of the cladocerans in Créteil Lake were measured in the daytime with 14C‐labeled Chlorella during a seasonal survey. This mesotrophic, shallow, polymictic lake is characterized by small algae (<25 µm) and cladocerans (<1.3 mm). Multiple regression models were established for each genus and for all the cladocerans. Body length alone explained from 44 to 57% of the total variance in the filtering rates of Daphnia spp., Ceriodaphnia spp., and Diaphanosoma brachyurum. An additional 23–34% of the variance was attributable to temperature. The inclusion of the Chl a concentration finally yielded r2 values ranging between 0.79 and 0.84. On the other hand, body length and temperature explained only 16% of the total variance in filtering rate of Bosmina longirostris. By taking into account the effect of factors other than length of the animal, the fit of the model established for all cladocerans improved considerably (from r2 = 0.47 to r2 = 0.83). Species‐specific responses and thermal effects in the lake show the difficulty of applying models based solely on body length to obtain sufficiently accurate estimates of cladoceran filtering rates.
Denitrification and photosynthesis in stream sediment studied with microsensor and wholecore techniques
Authors: Nielsen Lars Peter , Bondo Christensen Peter , Revsbech Niels Peter , Sørensen Jan
Published: April 2010

The effect of light on benthic photosynthesis, denitrification, and assimilation of NH4+ and NO3− in stream sediments was studied with whole‐core techniques and with O2 and N2O microsensors. Photosynthetic oxygen production increased the thickness of the aerobic surface layer from 1.5 mm in the dark ∼3.5 mm at a light intensity saturating photosynthesis. The O2 flux changed concurrently from net uptake to net release and the overall rate of denitrification was reduced by 70%. Denitrification was always restricted to a narrow zone immediately below the aerobic‐anaerobic interface. Calculated NO3− microprofiles showed that overall denitrification was primarily dependent on the thickness of the aerobic layer which acted as a barrier for diffusion of NO3− from the overlying water. In the light, algal NO3− assimilation could exceed NO3− consumption by denitrification when availability of NH4+ was low. Assimilation of NO3−, however, had no influence on the flux of NO3− to the denitrification zone, since assimilation occurred relatively close to the sediment surface.
Digging with a vortex: Flow manipulation facilitates prey capture by a predatory stream mayfly
Authors: Soluk Daniel A. , Craig Douglas A.
Published: April 2010

The effect of rapid flow and substrate instability on the distribution of benthic organisms is viewed as negative. Larvae of the mayfly Pseudiron centralis McDunnough not only tolerate rapid flows and loosely consolidated shifting sands (typical features of the beds of large lowland rivers), but are unique in their ability to exploit these conditions to facilitate the capture of prey. Unusual posturing allows Pseudiron larvae to transform themselves from streamlined forms closely appressed to the sediment surface into bluff objects that project from the surface and cause local disruption of flow. By obstructing the flow in this way, a Pseudiron larva creates an energetic vortex whose erosive power is used to excavate pits in the loose sands. Small burrowing and interstitial invertebrates exposed by removal of sand grains in the pits are then attacked and consumed. Using a vortex as a digging tool allows Pseudiron larvae to exploit infaunal prey, although they lack morphologically specialized fossorial appendages.
An investigation ofhydrogen peroxide chemistry in surface waters of Vineyard Sound with H218O2 and 18O2
Authors: Moffett James W. , Zajiriou Oliver C.
Published: April 2010

18O‐labeled H2O2 and O2 have been used to determine absolute rates and pathways of peroxide formation and decay processes in surface waters of a coastal marine site. Reactions were followed by incubating seawater samples with 18O2 or H218O2 and following the chemical transformation of the isotope label.

Decomposition of H218O2 was dominated by biological processes and led to the formation of 18O2 and H218O; the product distribution indicates that 65–80% of the decay was due to catalase with 20–35% due to peroxidase activity. Photochemical oxidation of H218O2 to 18O2 was also observed.

Particle‐dependent, light‐independent peroxide production was also observed in freshly collected samples, with rates ranging from 0.8 to 2.4 nM h−1 . These rates are low relative to photochemical production rates in surface waters, but may be important under conditions of low light intensity. Experiments with a metabolic inhibitor suggest that at least some of this production was biologically mediated. However, there was no evidence for light‐dependent biological production.
Alkalinities of Maine lakes: Are they really changing?
Authors: Staufferl Robert E.
Published: April 2010

Alkalinity changes between 1938–1944 and 1985 were evaluated for Maine lakes (zmax ≳ 15 m) in granitic watersheds. Modern (late summer 1985) Gran alkalinities for the hypolimnion were compared with historical alkalinities computed using:

urn:x-wiley:00243590:media:lno19903561238:lno19903561238-math-0001

where pH(T) is the historic reported colorimetric pH at each hypolimnetic sampling depth and temperature, pK'1(T) the temperature‐dependent negative logarithm of the first dissociation constant for carbonic acid, and H2CO3* represents initial CO2 at last spring overturn, plus the change in CO2 associated with the hypolimnetic oxygen deficit developed over summer (estimated from the historic oxygen data). With modern data for representative Maine lakes and historical (1932) data on dissolved gases reported for northern Wisconsin lakes, the apparent respiratory quotient relating ΔCO2 to ΔO2 = 0.92. The above model yields alkalinity estimates with a relative root‐mean‐square (RMS) error of ∼15%.

The alkalinities of the Maine lakes have increased by 15–50 µeq liter−1 (>30%) since the original surveys. Lake alkalization is not the result of differences in antecedent weather, since abnormally dry weather predating 1942 would have acted to elevate alkalinities.
Cross‐flow filtration of colloids from aquatic environments
Authors: Yeats P. A. , Strain P. M. , Whitehouse B. G.
Published: April 2010

In recognition of problems associated with traditional ultrafiltration techniques, cross‐flow ultrafiltration has been adapted to isolate colloidal material from natural aquatic environments, both freshwater and marine. The procedure is capable of delivering filtration rates on the order of tens of liters per hour without introducing significant quantities of organic or trace‐metal contaminants, and thus is suitable for large‐volume and trace‐component applications. Mass balance experiments in which concentrations were measured in ultrafiltrate and retained fractions show that both organic material and several trace metals are recovered without significant losses on the filters.
Subsidence. accretion. and sea level rise in south San Francisco Bay marshes
Authors: Patrick Wm. H. , R. D. DeLaune
Published: April 2010

Accelerated sea level rise that is predicted to occur as a result of the greenhouse effect is likely to have a significant effect on the world’s salt marshes. For salt‐marsh vegetation to remain productive and even to survive in a period of rising sea level, the marsh must accrete sufficient sediment to maintain the marsh surface within an appropriate tidal range. Accretion and subsidence were studied in three south San Francisco Bay salt marshes that differed greatly in subsidence over the past few decades. Marsh accretion as a result of sedimentation and peat formation has been able to compensate for high rates of subsidence and the low rate of sea level rise and to maintain the elevation of the marsh surface above mean high water (MHW). South San Francisco Bay appears to be a sediment‐rich system that transports enough sediment by tidal action and during storm events to compensate for sea level rise and subsidence in the fringing salt marshes.
Evidence against incorporation of exogenous thymidine by sulfate‐reducing bacteria
Authors: Gilmour C. C. , Leavitt M. E. , Shiaris M. P.
Published: April 2010

The uptake of exogenous [3H]thymidine by SO42−‐reducing bacteria (SRB) was tested in both pure culture and in marine sediments. Ten cultures isolated from mesohaline sediments of Chesapeake Bay, plus ATCC strain Desulfovibrio desulfuricans aestuarii, were incubated in SO42−‐reducing media with [3H]TdR concentrations ranging from 2 to 100 nM. In most cases [3H]TdR uptake levels were no more than a few times higher than Formalin‐killed controls; SRB cells took up a maximum of 1.7 × 10−22 moles TdR cell−1 h−1. Across all incubations, an average of 3.3 × 1023 SRB cells were produced (mol [3H]TdR)−1 taken up, compared to an average value of ∼2 × 1018 cells (mol [3H]TdR)−1 in natural, oxic waters. In anoxic sediments the addition of molybdate, an inhibitor of SO42− reduction, significantly reduced amino acid metabolism but did not decrease [3H]TdR incorporation into TCA‐insoluble material. These data suggest that the thymidine uptake method may drastically underestimate bacterial production in samples where SO42− reduction is quantitatively important, such as nonsurficial marine and estuarine sediments and anoxic saline waters.
An encounter model to predict natural planktonic bioluminescence
Authors: Buskey Edward J. , Swift Elijah
Published: April 2010

Natural bioluminescence results from the emissions of bioluminescent organisms in the absence of man‐made disturbance. Most epipelagic and mesopelagic bioluminescence is caused by planktonic organisms. Limited attempts to measure natural bioluminescence in situ with surface deployed and moored instruments have recorded much higher levels of natural bioluminescence than have been observed from submersibles. We present a model predicting the frequency of interactions among planktonic organisms leading to natural bioluminescent emissions. The results suggest that natural bioluminescent flashes caused by interactions between zooplankters may be rare events in the Sargasso Sea, with our model predicting a maximum of nearly 600 flashes h−1 m−3 at night in surface waters of the northern Sargasso Sea where there was an unusually high concentration of euphausiids and small bioluminescent dinoflagellates, but <1 flash h−1 m−3 in the southern Sargasso Sea. In both locations most of the natural bioluminescence was predicted to be caused by euphausiids and copepods of the genus Pleuromamma and natural bioluminescence generally decreased with depth. The more intense displays of natural bioluminescence are probably the result of the bioluminescence of numerous smaller dinoflagellates common in coastal waters and may also be the result of disturbances caused by interactions of larger organisms with bioluminescent plankters.
Formation of carbonyl compounds from UV‐induced photodegradation of humic substances in natural waters: Fate of riverine carbon in the sea
Authors: Kieber Robert J. , Zhou Xianliang , Mopper Kenneth
Published: April 2010

Low‐molecular‐weight (LMW) carbonyl compounds, e.g. formaldehyde, acetaldehyde, and the α‐keto acid glyoxylate, were produced in a wide variety of natural waters upon irradiation with sunlight. Production rates were linearly related (r2 > 0.98) to initial absorbance at 300 nm and initial fluorescence (360/460 nm) in all waters tested. Photochemical production was also linearly related to loss (photobleaching) of absorbance and fluorescence during irradiation, irrespective of irradiation time and prior photobleaching history of the sample. These results were attributed to absorption of light by humic substances in the waters, as determined by experiments where purified humic and fulvic extracts were added to open‐ocean water. The wavelengths in the solar spectrum responsible for photoproduction of LMW carbonyl compounds and bleaching of dissolved organic matter light absorbance are in the UV‐B region (280–320 nm). These results, plus results from time‐course irradiations, suggest that photoproduction of carbonyl compounds from humic substances is closely related to photobleaching of absorbance. Based on our photoproduction rates of LMW carbonyl compounds, we estimate that the half‐life of humic‐rich riverine dissolved organic C in the oceanic mixed layer is 5–15 yr.
Ammonium recycling versus denitrification in Chesapeake Bay sediments
Authors: Kemp W. M. , Sampou P. , Caffrey J. , Mayer M. , Henriksen K. , Boynton W. R.
Published: April 2010

Contemporaneous measurements are reported for nitrification, denitrification, and net sediment— water fluxes of NH4+ and NO3− in the mesohaline region of Chesapeake Bay. Seasonal cycles over a 2‐yr period were characterized by a midsummer maximum in NH4+ efflux to the overlying water and a May peak in NO3− removal from water by sediments. Coherent temporal patterns for nitrification and denitrification were observed, with relatively high values in spring and fall and virtual elimination of both processes in summer. Indirect measurements indicate that nitrification was limited by the shallow O2 penetration (<1 mm) here compared to reports for other marine sediments (2–6 mm). In addition, a strong positive correlation between the two processes suggested that denitrification was generally controlled by nitrification. Comparisons of NO3− fluxes and net nitrification rates (nitrification minus NO3− reduction to NH4+) revealed that measurements of denitrification with the acetylene block method systematically underestimated actual rates. Rates of N2 loss in denitrification were similar to NH4+ recycling fluxes to the overlying water in spring and fall, but in summer negligible denitrification contributed to enhanced NH4+ recycling. These results suggest that inhibition of denitrification in eutrophic estuaries such as Chesapeake Bay may reinforce the effects of nutrient enrichment by allowing increased rates of NH4+ recycling.
Overwintering development, growth, and feeding of larval Euphausia superba in the Antarctic marginal ice zone
Authors: Daly Kendra L.
Published: April 2010

Seasonal extent of pack ice has enormous influence on the Antarctic ecosystem. An investigation of the marginal ice zone in winter took place in the Scotia‐Weddell Seas, a major nursery ground for the Antarctic krill Euphausia superba. Krill larvae were abundant at the ice edge and on the undersurfaces of ice floes where the pack ice provided greater concentrations of food and a superior refuge compared to the water column. Larval development and growth, which is dependent on food supply, progressed steadily from June through August. In early June, furcilia stages F3–F5 were most abundant but, by August, F6s and juveniles predominated. Krill molted about every 20 d and growth rates (0.07 mm d−1) were similar to reported summer rates. Gut fullness indicated that 98% of the larvae were feeding both day and night. Ingestion rates based on gut pigments, however, were inadequate to meet respiratory requirements. Dietary analysis revealed that in addition to diatoms, larvae ingest protozoans and possibly detritus. If heterotrophic C is considered, larval krill feeding on sea ice biota could ingest sufficient C to support observed growth. Seasonal pack ice coverage over nursery grounds thus plays an important role in the overwintering of larval krill.
Seasonal spillover and varve formation in the Santa Barbara Basin, California
Authors: Reimers Clare E. , Lange Carina B. , Tabak Marialana , Bernhard Joan M.
Published: April 2010

A temporal record of oxygen and NO3− concentrations in the bottom water of the Santa Barbara Basin indicates that outside waters spill over into the basin seasonally. It is proposed that an annual bottom‐water cycle leads ultimately to varve production.

As evidence in support of a benthic mechanism for varve formation, we present results of surface sediment and pore‐water analyses, from box‐core collections during three seasons in 1988. The greater degree of bottom‐water oxygen depletion that occurs regularly in late summer and fall was coincident with a smaller pool of pore‐water Fe, penetration of ∑H2S up to the sediment‐water interface, maximal numbers of benthic Foraminifera, and bacterial mat growth. The latter was indicated by increases in concentrations of extractable ATP, organic C, and total N in sediments from the depth intervals 0–0.25 and 0.25–0.5 cm. The greatest numbers of siliceous phytoplankton skeletons were found on the sea floor soon after the late spring, surface‐water, Chl a maximum. This event coincides with additions of new and more‐oxygenated seawater to the deep basin.
Nitrate use by plankton in the eastern subtropical North Atlantic, March‐April 1989
Authors: Eppley Richard W. , Koeve Wolfgang
Published: April 2010

Nitrate concentration was measured in seawater samples from the euphotic zone at the beginning and end of 12‐h, daytime, in situ incubations. The changes in concentration are considered to be measurements of new production. During periods of 2–3 weeks in March–April 1989, important time scales for NO3− input to the euphotic zone (i.e. residence times) and new production were ~26 d at 18°N, 31°W and ~10 d near 33°N, 21°W. The average rate of NO3− use in the two areas was 2.63 and 0.62 mmol N m−2 (12 h)−1, or, in carbon equivalents 209 and 49 mg C m−2 d−1, respectively. These values bracket the large‐scale estimate by Jenkins of new production in the nearby beta triangle of 150 mg C m−2 d−1.
Heterotrophic, autotrophic, and mixotrophic nanoflagellates: Seasonal abundances and bacterivory in a eutrophic lake
Authors: Sanders Robert W. , Porter Karen G. , Bennett Susan J.
Published: April 2010

Abundances of heterotrophic (HF), autotrophic (AF), and mixotrophic (MF) nanoflagellates in Lake Oglethorpe, Georgia, were in the range 102–104 cells ml−1. Pigmented and nonpigmented flagellate abundances were positively correlated with each other in samples spanning a year, but were not significantly correlated to the same physical parameters (temperature, oxygen, light). The highest density of nonpigmented flagellates (> 1 × 104 ml−1) was found in spring 1986 at the surface, although most abundance peaks ranged from 4 to 7 × 103 cells ml−1 and occurred in the metalimnion during summer stratification. Abundances of pigmented flagellates (AF + MF) were greatest (9 × 103 cells ml−1) in surface waters in early spring and late fall when the lake was not stratified. Up to 38% (avg 10%) of all pigmented flagellates at any depth also ingested particles, while the percentage of HF that were identified as bacterivores ranged from 30 to 100%. In situ grazing rate measurements indicated strong seasonal differences in the relative grazing impact of pigmented and nonpigmented flagellates, with HF dominating grazing on picoplankton except in winter.
Adaptive Internal Model Control with fractional order parameter
Authors: Ladaci S. , Loiseau J. J. , Charef A.
Published: April 2010

In this paper we have introduced as a model in the adaptive Internal Model Control (IMC) structure a fractional order system to obtain a fractional adaptive IMC scheme. We have shown that this adaptive control scheme always provides theoretical guarantees of stability when a stable fractional order transfer function is used as an IMC parameter and that the use of this fractional IMC parameter can improve the performances of the control system along with its robustness against noises. A comparative simulation example is given to illustrate the efficiency of the proposed fractional order adaptive control scheme. Copyright © 2010 John Wiley & Sons, Ltd.
Mechanisms, Kinetics, and Dynamics of Oxidation and Reactions on Oxide Surfaces Investigated by Scanning Probe Microscopy
Authors: Altman Eric I. , Schwarz Udo D.
Published: April 2010

Advances in scanning probe microscopies (SPM) have allowed the mechanisms and rates of adsorption, diffusion and reactions on surfaces to be characterized by directly observing the motions of the individual atoms and molecules involved. The importance of oxides as thermal and photocatalysts, chemical sensors, and substrates for epitaxial growth has motivated dynamical SPM studies of oxide surfaces and their formation. Work on the TiO2 (110) surface is reviewed as an example of how dynamic SPM studies have revealed unexpected interactions between adsorbates and defects that influence macroscopic reaction rates. Studies following diffusion, adsorption and phase transitions on bulk and surface oxides are also discussed. A perspective is provided on advanced SPM techniques that hold great promise for yielding new insights into the mechanisms and rates of elemental processes that take place either during oxidation or on oxide surfaces, with particular emphasis on methods that extend the time and chemical resolution of dynamical SPM measurements.
Nanoelectronic Biosensing of Dynamic Cellular Activities Based on Nanostructured Materials
Authors: Huang Yinxi , Chen Peng
Published: April 2010

Detecting subtle cellular activities that occur dynamically as regulated temporally and spatially by molecular machinery is of obvious importance in fundamental biology as well as in drug discovery. Additionally, it demands fast and sensitive detection modality. The emerging nanoelectronic biosensors based on nanostructured materials have shown promising potential to resolve the dynamic biological processes of living cells with high sensitivity and high temporal and spatial resolution. Here, the recent advances in the nanoelectronic biosensing of regulated secretion of biomolecules and bioelectrical activities of ion channels using carbon nanotubes and silicon nanowires are briefly reviewed. The perspectives and key issues of future development are also discussed.
Hydrothermal Synthesis of Ionic Liquid [Bmim]OH‐Modified TiO2 Nanoparticles with Enhanced Photocatalytic Activity under Visible Light
Authors: Hu Shaozheng , Wang Anjie , Li Xiang , Wang Yao , Löwe Holger
Published: April 2010

TiO2 nanocomposites modified with the ionic liquid [Bmim]OH are synthesized by a hydrothermal procedure. X‐ray diffraction, Zeta‐potential measurement, TEM, thermogravimetric analysis, photoluminescence, UV/Vis, FTIR, and X‐ray photoelectron spectroscopy are used to characterize the TiO2 nanocomposites. The TiO2 nanocomposites consist of pure anatase particles of about 10 nm. The modification of [Bmim]OH on the surface of the TiO2 particles extends the TiO2 absorption edge to the visible‐light region. The electrochemical redox potentials indicated that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of [Bmim]OH match well with the valence band (VB) and conduction band (CB) of the TiO2 semiconductor. [Bmim]OH‐modified TiO2 is much more active than pristine TiO2 under visible‐light irradiation in the photocatalytic degradation of methylene blue in aqueous solution. [Bmim]OH is chemically bonded to the surface TiOH of TiO2 particles rather than adsorbed on the surface. A possible mechanism for the photocatalysis is proposed.
Water Accessibility to the Binding Cleft as a Major Switching Factor from Entropy‐Driven to Enthalpy‐Driven Binding of an Alkyl Group by Synthetic Receptors
Authors: Matsumoto Sayaka , Iwamoto Hiroya , Mizutani Tadashi
Published: April 2010

Free energy, enthalpy, and entropy changes in the binding of alkyl pyridines to water‐soluble zinc porphyrin receptors with varying accessibility of water to the binding cleft were determined to explain why the driving force of hydrophobic effects is enthalpic in some occasions and entropic in others. Zinc porphyrins bearing four alkyl pillars with terminal solubilizing poly(oxyethylene) (POE) chains of molecular weight of 750 (1), with eight alkyl pillars with terminal solubilizing POE chains of molecular weight of 350 (3), and with eight alkyl pillars with POE of molecular weight of 750 (4) had a binding cleft with decreasing water accessibility in this order as revealed by binding selectivity of imidazole/pyridine. Although all these porphyrins showed that the free energy of binding (−ΔGo) increases linearly as the alkyl group of the guest is lengthened (−ΔGo per CH2 was 2.6, 2.8, and 2.6 kJ mol−1 for 1, 3, and 4, respectively), the origin of the free energy gain was much different. Receptor 1 with the most hydrophilic binding site bound the alkyl group by an enthalpic driving force (4‐pentylpyridine favored over 4‐methylpyridine by ΔΔHo=−16.4 kJ mol−1), while receptor 4 with the most hydrophobic binding site by an entropic driving force (4‐pentylpyridine favored over 4‐methylpyridine by ΔΔSo=39.6 J K−1 mol−1). Receptor 3 showed intermediate behavior: both enthalpic and entropic terms drove the binding of the alkyl group with the enthalpic driving force being dominant. The binding site of the four‐pillared receptor (1) is open and accessible to water molecules, and is more hydrophilic than that of the eight‐pillared receptor (4). We propose that the alkyl chains of 1 are exposed to water to produce a room to accommodate the guest to result in enthalpy‐driven hydrophobic binding, whereas 4 can accommodate the guest without such structural changes to lead to entropy‐driven hydrophobic binding. Therefore, accessibility of water or exposure of the binding site to the water phase switches the driving force of hydrophobic effects from an entropic force to an enthalpic force.
Involvement of an influx transporter in the blood–brain barrier transport of naloxone
Authors: Suzuki Toyofumi , Ohmuro Aya , Miyata Mariko , Furuishi Takayuki , Hidaka Shinji , Kugawa Fumihiko , Fukami Toshiro , Tomono Kazuo
Published: April 2010

Naloxone, a potent and specific opioid antagonist, has been shown in previous studies to have an influx clearance across the rat blood–brain barrier (BBB) two times greater than the efflux clearance. The purpose of the present study was to characterize the influx transport of naloxone across the rat BBB using the brain uptake index (BUI) method. The initial uptake rate of [3H]naloxone exhibited saturability in a concentration‐dependent manner (concentration range 0.5 µMto 15 mM) in the presence of unlabeled naloxone. These results indicate that both passive diffusion and a carrier‐mediated transport mechanism are operating. Thein vivokinetic parameters were estimated as follows: the Michaelis constant,Kt, was 2.99±0.71 mM; the maximum uptake rate,Jmax, was 0.477±0.083 µmol/min/g brain; and the nonsaturable first‐order rate constant,Kd, was 0.160±0.044 ml/min/g brain. The uptake of [3H]naloxone by the rat brain increased as the pH of the injected solution was increased from 5.5 to 8.5 and was strongly inhibited by cationic H1‐antagonists such as pyrilamine and diphenhydramine and cationic drugs such as lidocaine and propranolol. In contrast, the BBB transport of [3H]naloxone was not affected by any typical substrates for organic cation transport systems such as tetraethylammonium, ergothioneine orL‐carnitine or substrates for organic anion transport systems such asp‐aminohippuric acid, benzylpenicillin or pravastatin. The present results suggest that a pH‐dependent and saturable influx transport system that is a selective transporter for cationic H1‐antagonists is involved in the BBB transport of naloxone in the rat. Copyright © 2010 John Wiley & Sons, Ltd.
Effects of homogeneous and inhomogeneous static magnetic fields combined with gamma radiation on DNA and DNA repair
Authors: Kubinyi Györgyi , Zeitler Zsuzsanna , Thuróczy György , Juhász Péter , Bakos József , Sinay Hanna , László János
Published: April 2010

The aim of this study was to reveal whether static magnetic fields (SMFs) influence the repair of radiation‐damaged DNA on leukocytes or has any effect on DNA. After 4 Gy of 60Co‐γ irradiation, some of the samples were exposed to inhomogeneous SMFs with a lateral magnetic flux density gradient of 47.7, 1.2, or 0.3 T/m by 10 mm lateral periodicity, while other samples were exposed to homogeneous SMF of 159.2 ± 13.4 mT magnetic flux density for a time period of 0.5 min, 1, 2, 4, 6, 18, 20, or 24 h. Another set of samples was exposed to the aforementioned SMFs before gamma irradiation. The following three groups were examined: (i) exposed to SMF only, (ii) exposed to SMF following irradiation by 60Co‐γ, and (iii) exposed to SMF before 60Co‐γ irradiation. The analysis of the DNA damage was made by single‐cell gel electrophoresis technique (comet assay). Statistically significant differences were found at 1 h (iSMF), 4 h (hSMF), and 18 h (hSMF) if samples were exposed to only SMF, compared to control. When the SMF exposure followed the 60Co‐γ irradiation, statistically significant differences were found at 1 h (iSMF) and 4 h (hSMF). If exposure to SMF preceded 60Co‐γ irradiation, no statistically significant difference was found compared to 4 Gy gamma‐irradiated group. Bioelectromagnetics 31:488–494, 2010. © 2010 Wiley‐Liss, Inc.
A comparative study of solid and liquid non‐aqueous phases for the biodegradation of hexane in two‐phase partitioning bioreactors
Authors: Hernández María , Quijano Guillermo , Thalasso Frédéric , Daugulis Andrew J. , Villaverde Santiago , Muñoz Raúl
Published: April 2010

A comparative study of the performance of solid and liquid non‐aqueous phases (NAPs) to enhance the mass transfer and biodegradation of hexane by Pseudomonas aeruginosa in two‐phase partitioning bioreactors (TPPBs) was undertaken. A preliminary NAP screening was thus carried out among the most common solid and liquid NAPs used in pollutant biodegradation. The polymer Kraton G1657 (solid) and the liquid silicone oils SO20 and SO200 were selected from this screening based on their biocompatibility, resistance to microbial attack, non‐volatility and high affinity for hexane (low partition coefficient: K = Cg/CNAP, where Cg and CNAP represent the pollutant concentration in the gas phase and NAP, respectively). Despite the three NAPs exhibited a similar affinity for hexane (K ≈ 0.0058), SO200 and SO20 showed a superior performance to Kraton G1657 in terms of hexane mass transfer and biodegradation enhancement. The enhanced performance of SO200 and SO20 could be explained by both the low interfacial area of this solid polymer (as a result of the large size of commercial beads) and by the interference of water on hexane transfer (observed in this work). When Kraton G1657 (20%) was tested in a TPPB inoculated with P. aeruginosa, steady state elimination capacities (ECs) of 5.6 ± 0.6 g m−3 h−1 were achieved. These values were similar to those obtained in the absence of a NAP but lower compared to the ECs recorded in the presence of 20% of SO200 (10.6 ± 0.9 g m−3 h−1). Finally, this study showed that the enhancement in the transfer of hexane supported by SO200 was attenuated by limitations in microbial activity, as shown by the fact that the ECs in biotic systems were far lower than the maximum hexane transfer capacity recorded under abiotic conditions. Biotechnol. Bioeng. 2010;106: 731–740. © 2010 Wiley Periodicals, Inc.
Enhancement of DNA uptake in FUT8‐deleted CHO cells for transient production of afucosylated antibodies
Authors: Wong Athena W. , Baginski Tomasz K. , Reilly Dorothea E.
Published: April 2010

Removal of the core α1,6 fucose from the glycans in the Fc region of IgG1 antibodies has been demonstrated to improve antibody‐dependent cellular cytotoxicity (ADCC) activity. In order to produce afucosylated antibodies using transient transfection, a FUT8 knockout (FUT8KO) cell line was generated in a CHO host cell line using the zinc finger nuclease technology. Transient transfection of DNA into mammalian cells using the cationic polymer, polyethylenimine (PEI), is commonly used for rapid generation of recombinant proteins. FUT8KO cells evaluated in PEI transfections yielded lower titers than parental CHO WT cells. FACS and HPLC analyses revealed that the FUT8KO cells had lower cell surface heparan sulfate (HS) levels than CHO WT. Removal of cell surface HS resulted in reduced uptake of PEI‐transfected DNA (PEI:DNA) and lower transfection titers suggesting that PEI:DNA relies on HS for binding and cellular entry. The absence of cell surface HS did not severely impact transfections performed with cationic liposomes. We undertook two approaches to improve transient production of afucosylated antibodies. First, we evaluated transfection of FUT8KO cells with cationic liposomes, which were observed to be less dependent on HS levels for uptake. Transfection of FUT8KO cells using the cationic liposome, DMRIE‐C, produced similar titers to CHO WT in both shake flask and large‐scale 10 L bioreactors. The second approach was to engineer a cell line overexpressing exostosin‐1 (EXT1), an enzyme responsible for HS chain elongation, to increase HS content. EXT1‐FUT8KO and CHO WT cells produced comparable levels of antibody from PEI transfections. Biotechnol. Bioeng. 2010;106: 751–763. © 2010 Wiley Periodicals, Inc.