bluuebunny/crossref_metadata_2025 huggingface dataset:
High DON bioavailability in boreal streams during a spring flood
Authors: Stepanauskas Ramūnas , Laudon Hjalmar , Jørgensen Niels O. G.
Published: June 2010

Riverine inputs of nitrogen is an important factor that controls productivity of coastal marine waters. Dissolved organic nitrogen (DON) comprises most of the N in boreal rivers. During spring floods, DON flux may exceed the baseflow flux by several orders of magnitude. However, little is known about the biological availability of spring flood DON and, thus, its potential effect on coastal productivity.

We have investigated the dynamics of DON bioavailability and chemical composition during a spring flood in two streams in northern Sweden. Potential bioavailability was determined by employing bacterial regrowth bioassays with brackish medium and a coastal bacterial inoculum. In addition, concentrations of urea and amino acids and the proportion of D‐isomers in total dissolved amino acids were analyzed because a high proportion of D‐isomers is suggested to indicate old and refractory organic material.

During the flood, potential DON bioavailability increased from 19–28% at baseflow to 55–45% during peak flow in the two streams, while DON concentration remained relatively constant. At the end of the flood, bioavailability returned to the baseflow values. Potential DON bioavailability was positively correlated with the concentration of dissolved combined amino acids and the proportion of L‐enantiomers of amino acids. However, only 5–18% of DON was identified as urea and free and combined amino acids, suggesting that bacteria also utilized other DON compounds. Our results imply that a major portion of the annual export of labile nitrogen occurred during a few weeks of spring flood.
High concentrations of complexed metals in the guts of deposit feeders
Authors: Chen Zhen , Mayer Lawrence M. , Quétel Christophe , Donard Olivier F. X. , Self Robert F. L. , Jumars Peter A. , Weston Donald P.
Published: June 2010

Sediment particles passing through the guts of deposit feeders are subject to an environment unusually rich in dissolved organic material, especially proteinaceous materials, capable of binding metals. Concentrations of many heavy metals are high in gut fluids of various deposit feeders from pristine environments. Concentrations of Cu and Cd show strong correlations with total acid‐hydrolyzed amino acids (TAHAA) in gut fluids in a cross‐phyletic survey of 35 deposit feeder species. Similar correspondence with TAHAA obtains among individuals, along longitudinal gut sections, and among molecular weight fractions. Multiple incubations of sediments with a commercial protein solution having similar TAHAA concentration as gut fluid solubilized many metals, showing convergence toward similar composition as gut fluid. Adherence of gut‐dissolved metal concentrations to the Irving‐Williams order suggests that the rich milieu of soft ligands contained in gut fluids provides a mechanism for mobilization of softer metals in sediments.
Changes in a tidepool fish assemblage on two scales of environmental variation: Seasonal and El Niño Southern Oscillation
Authors: Davis Jana L. D.
Published: June 2010

Intertidal organisms are influenced by the tidal, daily, and seasonal environmental variability of their habitat. Interannual variability, although often less severe than shorter‐scale variability, may also be important in structuring intertidal systems. This study compares the magnitude of changes in a rocky intertidal fish guild occurring on a seasonal scale with those occurring during an El Niño Southern Oscillation (ENSO). I examined tidepool fish assemblage structure and habitat use in two southern California sites approximately every 3 months from 1996 to 2000, a period including non‐ENSO conditions, the 1997–1998 El Niño, and the 1998–1999 La Niña. During each sampling period, I censused fish abundance in 105 tidepools of differing intertidal height, depth, and surface area. Several aspects of habitat use varied seasonally for the four most common species: Clinocottus analis (woolly sculpin), Girella nigricans (opaleye), Gobiesox rhessodon (California clingfish), and Hypsoblennius gilberti (notch‐brow blenny). All four species migrated vertically within the intertidal zone on a seasonal scale, corresponding to seasonal changes in sea level. The assemblage dominant, C. analis, occupied tidepools of different sizes depending on season. Although seasonality in habitat use suggests an influence of environmental variability on seasonal scales, fish habitat was generally not altered by temperature and sea level changes imposed by the El Niño. Species assemblage, however, differed among climate conditions. C. analis declined in abundance during the El Niño because of lack of recruitment but increased immediately after its conclusion. Paraclinus integripinnis (reef finspot), usually rare, was more abundant during the El Niño. Effect of the El Niño on the other four species was not detected. Assemblage changes suggest that although intertidal fishes regularly experience large tidal, daily, and seasonal environmental fluctuations, interannual changes in environmental factors, even when relatively small in magnitude, can perturb the system. Perturbations in the present system, however, did not persist beyond the end of the El Niño event as they often do in lower‐latitude nearshore areas.
Expansion of a moraine‐dammed glacial lake, Tsho Rolpa, in Rolwaling Himal, Nepal Himalaya
Authors: Sakai Akiko , Chikita Kazuhisa , Yamada Tomomi
Published: June 2010

Across the surface of debris‐covered glaciers in the Nepal Himalayas there are many lakes on the order of 1 km in scale. Some of the lakes, dammed by the end/lateral moraine, have been expanded from ponds on the order of 100 m in length. Tsho Rolpa Glacier Lake in the headwater region of the Rolwaling Valley, Eastern Nepal, was probably a small pond in the early 1950s. The present expansion rate of the glacial lake is unknown. From our investigation of the hydrological and meteorological conditions in 1993–1994, the calculated heat balance in the lake showed a deepening rate of about 1.2 m yr−1 all through the year. This is comparable to the mean deepening rate of the bottom basin since 1952. The vertical expansion thus is still continuing. Annual volume expansion including the calving ice (horizontal expansion) volume was 3% of the present total volume of the lake.
Paleogenetic evidence for a past invasion of Onondaga Lake, New York, by exotic Daphnia curvirostris using mtDNA from dormant eggs
Authors: Duffy Meghan A. , Perry Linda J. , Kearns Colleen M. , Weider Lawrence J. , Hairston, Nelson G.
Published: June 2010

Cladocerans possess traits such as resistant diapausing eggs and rapid parthenogenetic reproduction that make them efficient invaders of new habitats. Nearly all known invasions have been successful, perhaps because failed invasions are difficult to detect. It is possible, however, to identify past failed invasions, by studying the diapausing egg bank. Daphnia ephippia were found in the sediments of Onondaga Lake, New York that could neither be hatched nor identified using egg‐case morphology. Instead, we used sequences of the 12S ribosomal ribonucleic acid (rRNA) gene of mitochondrial deoxyribonucleic acid (mtDNA) extracted from diapausing eggs to identify the unknown Daphnia. We compared these DNA sequences with those generated from morphologically identified Daphnia species collected in Onondaga Lake, and with published sequences for other North American Daphnia species. The invader was identified as Daphnia curvirostris, a Eurasian species that has been only reported once before from North America, in extreme northwestern Canada. The discovery of it in Onondaga Lake signifies a greater than 4,500‐km range extension for this species. On the basis of the sediment ephippial data, D. curvirostris first appeared in the lake about 1952, reached maximum abundance during the period of peak pollution (1950s–1980s), and then essentially disappeared after 1983 when lake water quality improved. As with the finding of another exotic cladoceran, D. exilis, in Onondaga Lake (Hairston et al. 1999a), it is likely that chemical industry activities on the lakeshores were the original source of invading D. curvirostris, that pollution allowed this species to become established in the lake, and that the reduction in pollution ultimately led to its disappearance from the water column.
Bacterial growth and grazing on diatom aggregates: Respiratory carbon turnover as a function of aggregate size and sinking velocity
Authors: Ploug Helle , Grossart Hans‐Peter
Published: June 2010

Bacterial growth, respiration, particulate organic carbon (POC), and particulate organic nitrogen (PON) were measured directly on differentially sized diatom aggregates incubated individually in suspension in order to study the coupling between these parameters under controlled conditions. After 3 d ofincubation, bacteria, flagellates, and ciliates were present on aggregates in the ratio of 1,100:30:1. Bacterial generation times ranged from 0.4 to 2 d, but these short generation times did not result in an increase of bacterial abundance because bacteria were grazed approximately at similar rates. The entire microbial community respired 2.90 carbon units for each carbon unit incorporated by the bacteria. Bacterial production, community respiration, POC, and PON increased with increasing aggregate size, and respiration was proportional to POC and PON content. The POC specific respiration rate on aggregates was 0.083 d−1, and 40% of the initial POC content was respired after 6 d. From simple calculations combining carbon‐specific respiration rates and aggregate sinking velocities, it is concluded that a tight coupling between POC and microbial respiration may control the carbon fluxes of sinking diatom aggregates in the ocean.
Calcification by crustose coralline algae on the northern Great Barrier Reef, Australia
Authors: Chisholm John R. M.
Published: June 2010

Calcification by four species of crustose coralline algae was estimated on the windward reef at Lizard Island, northern Great Barrier Reef, Australia, by combining measurements of O2, pH, and total alkalinity with equations describing the seawater carbonate equilibrium. Calcification (C) was regressed against irradiance (I) and modeled using a general exponential function. C‐I models yielded estimates of gross calcification that ranged from 9.6 mmol CaCO3 m−2 h−1 at 0 m to 2.0 mmol CaCO3 m−2 h−1 at 18 m. A significant proportion of all samples exhibited CaCO3 dissolution in the dark. Integration of C‐I models with half sine‐curve approximations of whole‐day irradiance yielded estimated net deposition rates of 0.82 to 9.1 g CaCO3 m−2 d−1. Net 24‐h calcification was linearly correlated with noontime irradiance. Daily CaCO3 deposition as a function of reef surface relief (3.1 for the crest and 5.0 for the slope) indicated potential contributions to reef accretion of 4.1 to 28.1 g m−2 d−1, assuming 100% coralline cover. These estimates predict annual deposition rates of 1.5 to 10.3 kg CaCO3 m−2 yr−1, provided that measurements made between late summer and mid‐winter are representative of calcification throughout the year. Since observed accretion falls far short of the quantities predicted by these measurements, erosive agencies must remove much of the CaCO3 deposited annually by crustose coralline algae on windward reef margins.
Inorganic carbon acquisition in coastal Pacific phytoplankton communities
Authors: Tortell Philippe D. , Rau Greg H. , Morel François M. M.
Published: June 2010

Despite significant advances in the understanding of carbon acquisition in eukaryotic algae and cyanobacteria, very little information is available on the mechanisms of C uptake in natural phytoplankton communities or the effects of CO2 variations on marine primary productivity. In this article, we present the results of a 3‐yr study of C acquisition in coastal Pacific phytoplankton populations and their responses to experimental CO2 manipulations. Diatom‐dominated phytoplankton assemblages collected without incubation showed photosynthetic characteristics indicative of a carbon concentrating mechanism. Cells possessed a high affinity for external inorganic C (apparent Km ~1 µM CO2) and accumulated internal inorganic C pools that were ~3–5.5‐fold higher than those in the external medium. Evidence of in situ carbonic anhydrase expression was found in some of the phytoplankton populations we examined, and inhibitor experiments showed that this enzyme was essential for C fixation by cells. The presence of carbon concentrating mechanisms enabled the phytoplankton to maintain rapid growth rates over a wide range of CO2 concentrations (3–32 µM). In five of six long‐term (~2–5‐d) CO2 manipulation experiments, no difference in growth rates could be detected across treatments. However, a significant decrease in growth rate (30%) was observed in one experiment at the lowest CO2 level tested (3 mM). Although phytoplankton growth rates were generally unaffected by the CO2 manipulations, significant CO2‐dependent changes occurred in the cellular biochemistry and physiology of two assemblages that were examined. Cells grown at low CO2 showed higher short‐term rates of C uptake (indicative of transport system up‐regulation), as well as enhanced expression of Rubisco and carbonic anhydrase. In one of these two incubation experiments, lower C:N and carbohydrate:protein ratios were observed at low CO2 . Phytoplankton from both incubations showed low C isotope discrimination relative to the 13C/12C of the available CO2. Photosynthetic fractionation factors (ϵp) ranged from ~3.5‰ to 7.5‰ and were independent of both cellular growth rates and aqueous CO2 concentrations. Our data indicate that nutrient‐replete, rapidly growing coastal phytoplankton can use carbon concentrating mechanisms and respond physiologically and biochemically to changing dissolved CO2 concentrations. Future field studies should examine the effects of CO2 on the growth of nutrient‐limited phytoplankton and assess the potential long‐term ecological shifts that may result from CO2 variations.
Seasonal evolution of the basin‐scale internal wave field in a large stratified lake
Authors: Antenucci Jason P. , Imberger Jörg , Saggio Angelo
Published: June 2010

The response of the water column to varying conditions of stratification and wind forcing was investigated in Lake Kinneret (Israel) using data collected from thermistor chains and acoustic Doppler current profilers during 1997 and 1998. The strong daily sea breeze was found to generate a vertical mode 1 internal Kelvin wave and basin‐scale internal Poincaré waves of vertical modes 1, 2, and 3. The Kelvin wave, the dominant component of the internal wave field, was responsible for alongshore velocities in the nearshore regions. In the upwind nearshore regions, velocities were dominated by the forced response to the wind and were cross‐shore in nature. In the lake interior, the Kelvin wave effect on the horizontal velocity field was minor compared to the higher vertical mode Poincareé waves. The Kelvin wave is shown to exist in resonant and nonforced states with the wind, whereas the vertical mode 1 Poincaré wave energy remained relatively constant, despite large variability in the forcing conditions. The energy in the higher mode Poincaré waves varied greatly, both on daily and seasonal timescales. The results demonstrate that the wind energy forces multiple basin‐scale internal wave modes and that prior motion in the water column must be considered when determining the subsequent internal wave response in periodically forced systems.
The production of chemical heterogeneity in Upper Mystic Lake
Authors: Knauer K. , Nepf H. M. , Hemond H. F.
Published: June 2010

Chemical heterogeneity in a lake may arise from spatially and temporally nonuniform inputs or from spatially nonuniform transformation rates within the water body. The potential for heterogeneity to persist at a given spatial scale then depends on the relative magnitudes of the hydraulic residence time, the timescale for mixing, and the timescale for transformations to and from the chemical species of interest. Through simple scaling arguments, the potential for heterogeneity in total arsenic (As) and arsenic speciation were predicted for Upper Mystic Lake, a small urban lake near Boston, Massachusetts. Specifically, heterogeneity in total arsenic was expected during periods of high inflow—which are typical of spring conditions—given a sufficient magnitude of inflow variation. Heterogeneity in As(III) was expected throughout the year, whenever spatial variations in the net As(V)‐to‐As(III) trans‐formation rate exceeded a few percent per day. Observed heterogeneity was consistent with these predictions. Although modest, heterogeneity in total As was highest in early spring (7%, expressed as the spatial standard deviation divided by the lakewide mean). By contrast, heterogeneity of As(III) was as high as 36%, indicating that spatial variation in oxidation and reduction rates is sufficient to contribute to heterogeneity. Heterogeneity in As(III) varied significantly from month to month.
Carbon versus iron limitation of bacterial growth in the California upwelling regime
Authors: Kirchman David L. , Meon Benedikt , Cottrell Matthew T. , Hutchins David A. , Weeks Debra , Bruland Kenneth W.
Published: June 2010

The importance of iron versus dissolved organic carbon (DOC) in limiting the growth of heterotrophic bacteria is unresolved, even though iron, DOC, and heterotrophic bacteria are recognized to be critical components of oceanic biogeochemical cycles and food web dynamics. We used enrichment experiments to examine the roles of organic carbon and iron in limiting bacterial growth in the California upwelling regime, where phytoplankton can be iron limited depending on the time and location of the upwelling‐induced phytoplankton bloom. In no‐addition controls and in incubations with added Fe, bacterial production and abundance did not change substantially over time. In contrast, in all eight experiments, addition of glucose alone stimulated bacterial production and growth rates as much as tenfold. In Fe‐replete areas (>1 nM), bacterial production and growth rates in glucose plus Fe treatments were similar to those incubations receiving only glucose. However, in low‐Fe regions, addition of glucose plus Fe enhanced bacterial production and growth rates significantly more than glucose alone. We were unable to detect any impact of iron on glucose and amino acid catabolism, and the data offer no support for the hypothesis that bacteria are colimited by Fe and DOC. Rather, these results suggest that growth of heterotrophic bacteria is limited primarily by organic carbon even in Fe‐poor waters, but when DOC limitation is relieved Fe may rapidly become a limiting factor.
Seasonal and vertical difference in negative and positive effects of grazers on heterotrophic bacteria in Lake Biwa
Authors: Gurung Tek Bahadur , Nakanishi Masami , Urabe Jotaro
Published: June 2010

Grazers affect prey abundance negatively through grazing and positively through releasing nutrients and substrates. In the present study, the relative importance of these positive and negative effects of grazers on bacterial abundance was examined seasonally at 2.5 m and 30 m depths in Lake Biwa. We used a method by Elser and Goldman to estimate in situ growth rate, grazing rate, and the fraction of growth rate that was stimulated by grazers smaller than 100 µm. At 2.5 m, the bacterial grazing rate showed clear seasonal changes with higher values in summer. At 30 m, bacterial grazing was significant but consistently low throughout the year. The fraction of the growth rate stimulated by grazers was changed with season and depth. At 2.5 m, bacteria compensated 30–40% of grazing loss by using deficient nutrients released by the grazers from May to October. During that period, bacterial growth rate was severely limited by phosphorus, and it is most likely that phosphorus release by grazers was stimulating bacteria. At 30 m, however, the bacterial growth rate was not stimulated by the grazers in the majority of the cases. Bacterial growth rate was limited by low temperature at this depth, so nutrient return from grazers does not have a beneficial effect on bacterial growth. These results indicate that the relative importance of positive and negative effects of grazers on bacterial abundance differs seasonally and vertically, and that positive effect becomes important when bacterial growth is limited by nutrients. In a given habitat, bacterial abundance changes less than one order of magnitude in spite of high growth rates. The present study suggests that grazers contribute to numerical stability of bacterial assemblages not only through grazing but also by regenerating deficient nutrients.
Atmospheric CO2 evasion, dissolved inorganic carbon production, and net heterotrophy in the York River estuary
Authors: Raymond Peter A. , Bauer James E. , Cole Jonathan J.
Published: June 2010

Direct measurements of the partial pressure of CO2 (pCO2) and dissolved inorganic carbon (DIC) were made over a 2‐yr period in surface waters of the York River estuary in Virginia. The pCO2 in surface waters exceeded that in the overlying atmosphere, indicating that the estuary was a net source of CO2 to the atmosphere at most times and locations. Salinity‐based DIC mixing curves indicate there was also an internal source of both DIC and alkalinity, implying net alkalinity generation within the estuary. The DIC and alkalinity source displayed seasonal patterns similar to that of pCO2 and were reproducible over a 2‐yr study period.

We propose that the source of inorganic carbon necessary for both the sustained CO2 evasion to the atmosphere and the advective export of DIC is respiration in excess of primary production (e.g., net heterotrophy). The rates of CO2 evasion and DIC export were estimated to provide an annual rate of net heterotrophy of ~100 g C m−2 yr−1. Approximately 40% of this excess inorganic carbon production was exported as DIC to the coastal ocean, whereas 60% was lost as CO2 evasion to the atmosphere. The alkalinity generation needed to sustain the export of inorganic carbon, as HCO3− , is most likely provided by net sulfate reduction in sediments. Accumulation of sulfide in the sediments of a representative site directly adjacent to the York River estuary is sufficient to account for the net export of alkalinity. The seasonality of net heterotrophy causes large variations in annual CO2 and DIC concentrations, and it stresses the need for comprehensive temporal data sets when reporting annual rates of CO2 evasion, DIC advection, and net heterotrophy.
Persistence of net heterotrophy in lakes during nutrient addition and food web manipulations
Authors: Cole Jonathan J. , Pace Michael L. , Carpenter Stephen R. , Kitchell James F.
Published: June 2010

Net ecosystem production (NEP) is the difference between gross primary production (GPP) and community respiration (R). We estimated in situ NEP using three independent approaches (net CO2 gas flux, net O2 gas flux, and continuous diel O2 measurements) over a 4–7 yr period in a series of small lakes in which food webs were manipulated and nutrient loadings were experimentally varied. In the absence of manipulation, these lakes were net heterotrophic according to all three approaches. NEP (NEP = GPP‐R) was consistently negative and averaged −35.5 ± 3.7 (standard error) mmol C m−2 d−1. Nutrient enrichment, in the absence of strong planktivory, tended to cause increases in estimates of both GPP and R (estimated from the continuous O2 data) but resulted in little change in the GPP/R ratio, which remained <1, or NEP, which remained negative. When planktivorous fish dominated the food web, large zooplankton were rare and nutrient enrichment produced positive values of NEP by all three methods. Among lakes and years, daily values of NEP ranged from −241 to +175 mmol m−2 d−1; mean seasonal NEP was positive only under a combination of high nutrient loading and a planktivore‐dominated food web. Community R is significantly subsidized by allochthonous sources of organic matter in these lakes. Combining all lakes and years, we estimate that ~26 mmol C m−2 d−1 of allochthonous origin is respired on average. This respiration of allochthonous organic matter represents 13 to 43% of total R, and this fraction declines with increasing GPP.
Functional separation of colloids and gravitoids in surface waters based on differential settling velocity: Coupled cross‐flow filtration—split flow thin‐cell fractionation (CFF‐SPLITT)
Authors: Gustafsson Örjan , Düker Anders , Larsson Jenny , Andersson Per , Ingri Johan
Published: June 2010

Given recognized challenges with shallow sediment trap and 234Th‐based particle flux studies, it behooves us to test the picture of surface ocean fluxes provided by such investigations with alternative and new analytical techniques. To this end, cross‐flow filtration (CFF) has been coupled with split flow thin‐cell fractionation (SPLITT) to afford active but mild separation of aquatic particles through a dynamic settling‐velocity discrimination. Operation parameters have been developed to yield accurate settling‐velocity cutoffs in the range >0.1–>10 m d−1, element recoveries in the range 85–110%, and minimal influence of CFF preconcentration up to at least a factor 110. Chemical fingerprints of truly settling matter (i.e., gravitoids) in coastal waters provided by the CFF‐SPLITT technique demonstrated that gravitoidal particles settling out of surface waters exhibit distinctly different compo‐sition than the bulk filterable particles. For instance, both gravitoidal POC and P belonged in a coastal Baltic regime largely to a slowly settling (1–2 m d−1) particle pool (presumably amorphous organic aggregates), which was decoupled from a more rapidly settling (>4 m d−1) Si‐containing particle pool (presumably diatom dominated). Both of these biogenic gravitoid pools were in turn distinct from an Fe‐containing gravitoid pool settling >4 m d−1, which, in contrast to POC, P, and Si gravitoids, had a geochemical composition similar to that of bulk particles.
Intertidal marsh as a source of dissolved inorganic carbon and a sink of nitrate in the Satilla River‐estuarine complex in the southeastern U.S.
Authors: Cai Wei‐Jun , Wiebe William J. , Wang Yongchen , Sheldon Joan E.
Published: June 2010

Total dissolved inorganic carbon (DIC), total alkalinity (TA), pH, and nitrate + nitrite (NOx) data collected during the summer of 1996 in the Satilla River estuary in the southeastern U.S. were used to assess fluxes of DIC and NOx between intertidal marshes and estuarine waters and to model system NOx dynamics. Nitrate and nitrite are produced in the low‐salinity portion of the estuary. The intertidal marshes are sites of intensive respiration that export DIC to the estuary and remove NOx. An integrated view is presented on the nitrification and denitrification processes in the marsh/estuarine complex and their relationship to CO2 generation rates. The distribution of NOx in the marsh and estuarine waters indicates that all NOx generated in the marsh‐estuary system is removed in the intertidal marshes, most likely via denitrification. Model analysis of NOx and river flow data for three seasons indicates that NOx distribution in the estuarine water is also determined by river flow rates. Export fluxes of NOx to the coastal ocean are insignificant in all seasons when compared to NOx production rates in the entire system; however, they are significantly higher than NOx inputs from the river end member in October 1996. Although only a small fraction (~10%) of DIC generated in the marshes is exported to the coastal sea and around 90% is lost to the atmosphere, it represents a nearly threefold increase in riverine DIC flux to the ocean.
The response of Chesapeake Bay salinity to climate‐induced changes in streamflow
Authors: Gibson Jody R. , Najjar Raymond G.
Published: June 2010

Autoregressive statistical models of monthly salinity variations in the mainstem of Chesapeake Bay are developed for use in climate change applications. Observations of salinity and Susquehanna River flow from 1984 to 1994 are used to calibrate the models. Up to 93% of the variance in salinity is captured by these models, with the best fits occurring in the middle of the bay, where submonthly fluctuations due to river flow and oceanic currents are damped. Our salinity models use output from a climate‐forced hydrological model under a doubling of present‐day atmospheric CO2. This coupling scheme predicts salinity changes between +3.5% and −27.5% near the mouth of the Susquehanna River, to between +0.1% and −0.7% near the ocean. These ranges demonstrate the uncertainty in climate model predictions, although three of the four scenarios used indicate increased Susquehanna River flow and therefore decreased salinity. In the highest flow scenario (a 32% annual increase) our results show that the bay's isohalines may recede by approximately 6.3 km (about 2% of the length of the bay) near the Susquehanna River, to as much as 55 km (about 17% of the length of the bay) near the middle bay. This shift implies that climate change may have consequences for organisms with low‐salinity thresholds, including oysters and crabs.
Influence of mycosporine‐like amino acids (MAAs) on UV absorption by particulate and dissolved organic matter in La Jolla Bay
Authors: Whitehead Kenia , Vernet Maria
Published: June 2010

Experimental work with cultures of the red tide dinoflagellate Lingulodinium polyedrum suggested mycosporine‐like amino acids (MAAs) are a component of the organic matter excreted by cells. MAAs in dissolved organic matter (DOM) also may have a large influence on absorption of ultraviolet (UV) light through the water column. To test these hypotheses in a natural setting, data were collected from March 1995 through April 1996 in coastal waters off California, U.S.A. During this time, a large red tide of L. polyedrum occurred in March and April 1995. In this field study, we show that MAAs are a quantifiable component of DOM, particularly during the period following the red tide events. Absorption spectra of particulate organic matter (POM) and DOM samples revealed disproportionately high levels of UV absorption relative to visible wavelengths. UV absorption by POM at 330 nm was linearly related to phytoplankton biomass (between 0–10 µg chlorophyll [Chl] a L−1), measured as Chl a, accounting for 71% of the variability in absorption. Chromatographic analyses revealed the presence of various MAAs in both POM and DOM pools. MAAs were observed in 83% (n = 53) and 47% (n = 13) of the samples analyzed with concentrations ranging from 0 to 2.75 µM (0–696.00 µmol µg−1 Chl a) in the POM and 0 to 111.40 nM in the DOM fraction. Absorption by dissolved MAAs, as calculated from the measured concentrations, correlated with DOM UV absorption (r2 = 0.77) and accounted for up to 10% of the total DOM absorption at 330 nm. Thus, MAAs are a small but quantifiable component of the DOM pool in the field and contribute to UV absorption.
Evidence of homing behavior in the coral reef mysid Mysidium gracile
Authors: Twining Benjamin S. , Gilbert John J. , Fisher Nicholas S.
Published: June 2010

Mysid swarms at benthic coral reef sites disperse into the water column in the evening and reform at the exact same location the following morning, possibly reflecting homing behavior of individual mysids. To facilitate tracking of individual mysids, we radiolabeled part of a swarm of Mysidium gracile with the gamma‐emitting radioisotope 65Zn and released the labeled animals back to the focal swarm on a reef in Discovery Bay, Jamaica. We collected the focal swarm and surrounding swarms the next morning to determine the location of the labeled individuals following nighttime dispersal. Seventy‐seven percent of the radiolabeled mysids returned to the same site the next day, and 13% of the labeled individuals were recovered from other nearby swarms. This recovery rate cannot be attributed to random reaggregation and suggests that mysids use a homing behavior to facilitate swarm reformation. This is the first unequivocal evidence of homing behavior in demersal zooplankton.
Regulation of nitrification in aquatic sediments by organic carbon
Authors: Strauss Eric A. , Lamberti Gary A.
Published: June 2010

Nitrification, the microbial conversion of ammonium to nitrate, is an important transformation in the aquatic nitrogen cycle, but the factors regulating nitrification rates in freshwater ecosystems are poorly understood. We investigated the effects of organic carbon quantity and quality on nitrification rates in stream sediments. First, we hypothesized that when environmental C: N ratios are high, heterotrophic bacteria are subject to N limitation and will outcompete nitrifying bacteria for available NH4+, thereby reducing nitrification rates. In laboratory experiments, organic carbon amendments (30 mg C L−1, as glucose) to stream sediments completely inhibited nitrification with or without addition of NH4+ (P < 0.0001), whereas amendment with NH4+ only (0.75 mg N L−1) increased nitrification by 40% compared with unamended controls (P < 0.0001). Carbon amendments also increased microbial respiration rates over controls by 4–6 times. Therefore, organic carbon additions significantly decreased nitrification rates but increased total microbial activity. Second, we hypothesized that carbon of high quality would have a stronger negative effect on nitrification than would carbon of low quality. To stream sediments, we added organic carbon as either glucose (higher quality) or sugar maple leaf extract (lower quality). Nitrification rates were reduced by the addition of either organic carbon source but were more severely inhibited by glucose (P = 0.001). Our results suggest that organic carbon is an important regulator of nitrification rates and is of key importance in understanding N dynamics in freshwater ecosystems.
Thiotaurine is a biomarker of sulfide‐based symbiosis in deep‐sea bivalves
Authors: Pruski A. M. , Médioni A. Fiala , Prodon R. , Colomines J. C.
Published: June 2010

A simple biochemical approach for demonstrating the presence of symbionts in deep‐sea bivalves and for discriminating between thiotrophic and methylotrophic symbioses is described. Correspondence analysis (CA) of the free amino compound composition of nine bivalve species living in hydrothermal vents and cold seeps successfully discriminates symbiotic species from nonsymbiotic ones, and sulfur‐oxidizing symbiont from methylotrophic symbionts. CA was also used to infer the metabolism of Bathymodiolus azoricus, B. boomerang, and two new species of Mytilid and Vesicomyid from the Barbados. These results were consistent with the evidence obtained by ultrastructural observations of the gills and enzymatic studies, and show that CA of amino acid profiles might be a useful tool to determine the type of endosymbionts present in deep‐sea bivalves. Among all the free amino acids, thiotaurine appears as the main discriminating one and is proposed as a biomarker of sulfide‐based endosymbiosis in deep‐sea bivalves from hydrothermal vents and cold seeps.
Evidence of trace metal limited photosynthesis in eutrophic estuarine and coastal waters
Authors: Zhang Jing
Published: June 2010

Based on field observations and incubation experiments, this study provides evidence that trace metal limited (e.g., Fe) photosynthesis may function in eutrophic coastal waters. In the Zhujiang (Pearl River) Estuary and the adjacent coastal area, analyses of water samples indicate that phytoplankton photosynthesis is apparently phosphorus limited in the freshwater and upper estuary and nitrogen and/or silica limited in the coastal waters farther offshore. The incubation experiments using in situ water samples show, however, that in both cases photosynthesis can be enhanced by addition of trace elements (e.g., Fe and Cu). This is presumably because exogenous influx of major plant nutrients has skewed the primary production toward trace‐element limitation, which in turn limits the increase in chlorophyll biomass and full consumption of major nutrients in eutrophic coastal waters as compared to the nutrient‐poor oligotrophic open ocean.
In Vivo Reactive Astrocyte Imaging in Patients With Schizophrenia Using Fluorine 18–Labeled THK5351
Authors: Kim Minah , Choi Woori , Choi Sunah , Oh Harin , Kim Jongrak , Lee Jungha , An Su-Jin , Hwang Jun Seo , Lee Yun-Sang , Song In Chan , Moon Sun-Young , Lho Silvia Kyungjin , Cho Sang Soo , Kwon Jun Soo
Published: May 2024

Importance

In vivo imaging studies of reactive astrocytes are crucial for understanding the pathophysiology of schizophrenia because astrocytes play a critical role in glutamate imbalance and neuroinflammation.

Objective

To investigate in vivo reactive astrocytes in patients with schizophrenia associated with positive symptoms using monoamine oxidase B (MAO-B)–binding fluorine 18 ([18F])–labeled THK5351 positron emission tomography (PET).

Design, Setting, and Participants

In this case-control study, data were collected from October 1, 2021, to January 31, 2023, from the internet advertisement for the healthy control group and from the outpatient clinics of Seoul National University Hospital in Seoul, South Korea, for the schizophrenia group. Participants included patients with schizophrenia and age- and sex-matched healthy control individuals.

Main Outcomes and Measures

Standardized uptake value ratios (SUVrs) of [18F]THK5351 in the anterior cingulate cortex (ACC) and hippocampus as primary regions of interest (ROIs), with other limbic regions as secondary ROIs, and the correlation between altered SUVrs and Positive and Negative Syndrome Scale (PANSS) positive symptom scores.

Results

A total of 68 participants (mean [SD] age, 32.0 [7.0] years; 41 men [60.3%]) included 33 patients with schizophrenia (mean [SD] age, 32.3 [6.3] years; 22 men [66.7%]) and 35 healthy controls (mean [SD] age, 31.8 [7.6] years; 19 men [54.3%]) who underwent [18F]THK5351 PET scanning. Patients with schizophrenia showed significantly higher SUVrs in the bilateral ACC (left, F = 5.767 [false discovery rate (FDR)–corrected P = .04]; right, F = 5.977 [FDR-corrected P = .04]) and left hippocampus (F = 4.834 [FDR-corrected P = .04]) than healthy controls. Trend-level group differences between the groups in the SUVrs were found in the secondary ROIs (eg, right parahippocampal gyrus, F = 3.387 [P = .07]). There were positive correlations between the SUVrs in the bilateral ACC and the PANSS positive symptom scores (left, r = 0.423 [FDR-corrected P = .03]; right, r = 0.406 [FDR-corrected P = .03]) in patients with schizophrenia.

Conclusions and Relevance

This case-control study provides novel in vivo imaging evidence of reactive astrocyte involvement in the pathophysiology of schizophrenia. Reactive astrocytes in the ACC may be a future target for the treatment of symptoms of schizophrenia, especially positive symptoms.
Hybrid Ceramic Polymer Electrolytes Enabling Long Cycling in Practical 1 Ah‐Class High‐Voltage Solid‐State Batteries with Li Metal Anode
Authors: Boaretto Nicola , Meabe Leire , Lindberg Simon , Perez‐Furundarena Haritz , Aldalur Itziar , Lobato Elias , Bonilla Francisco , Combarro Izaskun , Gutiérrez‐Pardo Antonio , Kvasha Andriy , Lechartier Marine , Vincent Rémi , Cognard Jérôme , Genies Sylvie , Daniel Lise , Martinez‐Ibañez María
Published: May 2024

Solid polymer electrolytes offer a safer alternative to organic liquid electrolytes in high‐voltage lithium metal batteries, yet challenges remain in achieving adequate cyclability, energy density, scalability, and safety. This study presents the cycling performance of 1 Ah high‐voltage lithium polymer batteries featuring a hybrid ceramic polymer electrolyte (HCPE), a lithium metal anode, and a LiNi0.8Mn0.1Co0.1O2 (NMC‐811)‐based positive electrode. The HCPE stands out for its remarkable mechanical properties, with a Young's modulus exceeding 200 MPa at room temperature, providing robust resistance against dendrite formation. The Li||Li symmetric cells exhibited outstanding performance, cycling for over 1000 hours at a capacity of 2 mAh cm−2, highlighting the exceptional attributes of HCPE. Full cell testing is conducted under practical conditions, utilizing various cell configurations, from coin cells to large pouch cells with a 1 Ah capacity, achieving an energy density of nearly 250 Wh kg−1 and promising cyclability with 80% capacity retention after 110 cycles. The study also investigated thermal runaway characteristics, showing comparability with commercial lithium‐ion batteries. This research underscores the scalability and performance of high‐voltage lithium metal polymer batteries, advancing their potential for commercial viability.
A Soft‐Tissue Driven Bone Remodeling Algorithm for Mandibular Residual Ridge Resorption Based on Patient CT Image Data
Authors: Zhong Jingxiao , Huang Wenwei , Ahmad Rohana , Chen Junning , Wu Chi , Hu Jingrui , Zheng Keke , Swain Michael V. , Li Qing
Published: May 2024

The role of the biomechanical stimulation generated from soft tissue has not been well quantified or separated from the self‐regulated hard tissue remodeling governed by Wolff's Law. Prosthodontic overdentures, commonly used to restore masticatory functions, can cause localized ischemia and inflammation as they often compress patients’ oral mucosa and impede local circulation. This biomechanical stimulus in mucosa is found to accelerate the self‐regulated residual ridge resorption (RRR), posing ongoing clinical challenges. Based on the dedicated long‐term clinical datasets, this work develops an in‐silico framework with a combination of techniques, including advanced image post‐processing, patient‐specific finite element models and unsupervised machine learning Self‐Organizing map algorithm, to identify the soft tissue induced RRR and quantitatively elucidate the governing relationship between the RRR and hydrostatic pressure in mucosa. The proposed governing equation has not only enabled a predictive simulation for RRR as showcased in this study, providing a biomechanical basis for optimizing prosthodontic treatments, but also extended the understanding of the mechanobiological responses in the soft‐hard tissue interfaces and the role in bone remodeling.
A Homochiral Porous Organic Cage‐Polymer Membrane for Enantioselective Resolution
Authors: Wang Fanmengjing , He Kaiqiang , Wang Ruoxin , Ma Hongyu , Marriott Philip J. , Hill Matthew R. , Simon George P. , Holl Mark M. Banaszak , Wang Huanting
Published: May 2024

Membrane‐based enantioselective separation is a promising method for chiral resolution due to its low cost and high efficiency. However, scalable fabrication of chiral separation membranes displaying both high enantioselectivity and high flux of enantiomers is still a challenge. Here, the authors report the preparation of homochiral porous organic cage (Covalent cage 3 (CC3)‐R)‐based enantioselective thin‐film‐composite membranes using polyamide (PA) as the matrix, where fully organic and solvent‐processable cage crystals have good compatibility with the polymer scaffold. The hierarchical CC3‐R channels consist of chiral selective windows and inner cavities, leading to favorable chiral resolution and permeation of enantiomers; the CC3‐R/PA composite membranes display an enantiomeric excess of 95.2% for R‐(+)‐limonene over S‐(−)‐limonene and a high flux of 99.9 mg h−1 m−2. This work sheds light on the use of homochiral porous organic cages for preparing enantioselective membranes and demonstrates a new route for the development of next‐generation chiral separation membranes.
Combating Atherosclerosis with Chirality/Phase Dual‐Engineered Nanozyme Featuring Microenvironment‐Programmed Senolytic and Senomorphic Actions
Authors: Ding Chengjin , Min Jiao , Tan Yongkang , Zheng Liuting , Ma Ruxuan , Zhao Ruyi , Zhao Huiyue , Ding Qingqing , Chen Hongshan , Huo Da
Published: May 2024

Senescence plays a critical role in the development and progression of various diseases. This study introduces an amorphous, high‐entropy alloy (HEA)‐based nanozyme designed to combat senescence. By adjusting the nanozyme's composition and surface properties, this work analyzes its catalytic performance under both normal and aging conditions, confirming that peroxide and superoxide dismutase (SOD) activity are crucial for its anti‐aging therapeutic function. Subsequently, the chiral‐dependent therapeutic effect is validated and the senolytic performance of D‐handed PtPd2CuFe across several aging models is confirmed. Through multi‐Omics analyses, this work explores the mechanism underlying the senolytic action exerted by nanozyme in depth. It is confirm that exposure to senescent conditions leads to the enrichment of copper and iron atoms in their lower oxidation states, disrupting the iron‐thiol cluster in mitochondria and lipoic acid transferase, as well as oxidizing unsaturated fatty acids, triggering a cascade of cuproptosis and ferroptosis. Additionally, the concentration‐dependent anti‐aging effects of nanozyme is validated. Even an ultralow dose, the therapeutic can still act as a senomorphic, reducing the effects of senescence. Given its broad‐spectrum action and concentration‐adjustable anti‐aging potential, this work confirms the remarkable therapeutic capability of D‐handed PtPd2CuFe in managing atherosclerosis, a disease involving various types of senescent cells.
A Rational Design of Bio‐Derived Disulfide CANs for Wearable Capacitive Pressure Sensor
Authors: Yang Ding , Zhao Kai , Yang Rulin , Zhou Shang‐Wu , Chen Meng , Tian He , Qu Da‐Hui
Published: May 2024

Classic approaches to integrate flexible capacitive sensor performance are to on‐demand microstructuring dielectric layers and to adjust dielectric material compositions via the introduction of insoluble carbon additives (to increase sensitivity) or dynamic interactions (to achieve self‐healing). However, the sensor's enhanced performances often come with increased material complexity, discouraging its circular economy. Herein, a new intrinsic self‐healable, closed‐loop recyclable dielectric layer material, a fully nature‐derived dynamic covalent poly(disulfide) decorated with rich H bonding and metal‐catechol complexations is introduced. The polymer network possesses a mechanically ductile character with an Arrhenius‐type temperature‐dependent viscoelasticity. The assembled capacitive pressure sensor is able to achieve a sensitivity of up to 9.26 kPa−1, fast response/recovery time of 32/24 ms, and can deliver consistent signals of continuous consecutive cycles even after being self‐healed or closed‐loop recycled for real‐time detection of human motions. This is expected to be of high interest for current capacitive sensing research to move toward a life‐like, high performance, and circular economy direction.
Superfast Zincophilic Ion Conductor Enables Rapid Interfacial Desolvation Kinetics for Low‐Temperature Zinc Metal Batteries
Authors: Cheng Xiaomin , Zuo Yinze , Zhang Yongzheng , Zhao Xinyu , Jia Lujie , Zhang Jing , Li Xiang , Wu Ziling , Wang Jian , Lin Hongzhen
Published: May 2024

Low‐temperature rechargeable aqueous zinc metal batteries (AZMBs) as highly promising candidates for energy storage are largely hindered by huge desolvation energy barriers and depressive Zn2+ migration kinetics. In this work, a superfast zincophilic ion conductor of layered zinc silicate nanosheet (LZS) is constructed on a metallic Zn surface, as an artificial layer and ion diffusion accelerator. The experimental and simulation results reveal the zincophilic ability and layer structure of LZS not only promote the desolvation kinetics of [Zn(H2O)6]2+ but also accelerate the Zn2+ transport kinetics across the anode/electrolyte interface, guiding uniform Zn deposition. Benefiting from these features, the LZS‐modified Zn anodes showcase long‐time stability (over 3300 h) and high Coulombic efficiency with ≈99.8% at 2 mA cm−2, respectively. Even reducing the environment temperature down to 0 °C, ultralong cycling stability up to 3600 h and a distinguished rate performance are realized. Consequently, the assembled Zn@LZS//V2O5‐x full cells deliver superior cyclic stability (344.5 mAh g−1 after 200 cycles at 1 A g−1) and rate capability (285.3 mAh g−1 at 10 A g−1) together with a low self‐discharge rate, highlighting the bright future of low‐temperature AZMBs.