bluuebunny/crossref_metadata_2025 huggingface dataset:
Ciliategrazing on picoplankton in a eutrophic reservoir during the summer phytoplankton maximum: A study at the species and community level
Authors: Šimek Karel , Bobková Jitka , Macek Miroslav , Nedoma Jiři , Psenner Roland
Published: May 2010

In late summer 1993 an intensive study was carried out on protozoan grazing in the epilimnion and metalimnion of the eutrophic Rímov Reservoir in south Bohemia. On average, ∼ 70% of bacterial production was consumed by heterotrophic flagellates and 20% by ciliates. Ciliate numbers increased from 5 to 70 cells ml−1 over the 5‐week study period. Ciliates <30 µm in size were numerically dominant in both layers and included Halteria grandinella and Strobilidium hexakinetum (Oligotrichida), Cyrtolophosis mucicola (Cyrtolophosida), Cinetochilum margaritaceum (Scuticociliatida), Urotricha spp., and Coleps sp. (Prostomatida). Ciliate species‐specific grazing rates on bacteria and picocyanobacteria were determined. The highest individual cell grazing rates, 4,200 bacteria and 560 picocyanobacteria cell−1 h−1, were observed in Vorticella aquadulcis‐complex. Oligotrichs ingested on average 360–2,130 bacteria and 76–210 picocyanobacteria cell−1 h−1, with H. grandinella (1,560 bacteria cell−1 h−1), due to its high abundance, as the most important ciliate bacterivore within the system. C. mucicola ingested on average 173 bacteria and 27 cyanobacteria cell−1 h−1; C. margaritaceum, 57 bacteria and 7 picocyanobacteria cell−1 h−1; and prostomatids, 23–100 bacteria and 2–14 picocyanobacteria cell−1 h−1. Although there was a tight relationship between grazing rates on bacteria and picocyanobacteria (r = 0.89, n = 12, P < 0.001), most of the ciliate species preferred larger picoplankton (i.e. picocyanobacteria), as indicated by their clearance rates. According to our data, several oligotrichous ciliate species and Cyclidium sp. can grow in pelagic conditions and exclusively on picoplankton food at rates of one doubling every 24–75 h.
Size‐fractionated NH4+ regeneration in the pelagic environments of two mesotrophic lakes
Authors: Haga Hiroki , Nagata Toshi , Sakamoto Mitsuru
Published: May 2010

Seasonal variation in NH4+ regeneration rates was examined by means of 15N‐isotope dilution for different size fractions of organisms (<1 µm, <20 µm, <100 µm, and >100 µm) in samples from mesotrophic Lakes Kizaki and Biwa, Japan. In both lakes, nanoflagellates and microzooplankton (mainly rotifers) accounted for a large fraction (17–55 and 0–67%, respectively) of total NH4+ regeneration (L. Kizaki, 0.011–0.261 µmol liter−1 h−1; L. Biwa, 0.040–0.163 µmol liter−1 h−1), suggesting that microbial food webs were primarily important in NH4+ regeneration. Contributions of crustacean mesozooplankton to NH4+ regeneration were generally minor (<16%), except on one occasion in early summer when crustaceans accounted for 62% of total NH4+ regeneration in Lake Kizaki. The weight‐specific NH4 regeneration rates (sR) of nanoflagellates and rotifers‐ciliates were 20–30‐fold greater than the corresponding rates for crustacean mesozooplankton, consistent with the general relationship between sR and body size of grazers. Bacterial contributions to NH4+ regeneration were high (26–51%) in summer but low (<10%) in spring and winter, which was explained in part by the strong dependency of bacterial sR on temperature. Our data demonstrate that rates and major pathways of NH4+ regeneration may vary greatly depending on the size structure of planktonic food webs.
Quantifying anoxia in lakes
Authors: Nürnberg Gertrud K.
Published: May 2010

The anoxic factor (AF, days per year or per season) can be used to quantify anoxia in stratified lakes. AF is calculated from oxygen profiles measured in the stratified season and lake surface area (A0) as

urn:x-wiley:00243590:media:lno19954061100:lno19954061100-math-0001

AF represents the number of days that a sediment area, equal to the whole‐lake surface area, is overlain by anoxic water. Average AF for 56 central Ontario lakes, 19 additional eastern North American lakes, including the Laurentian Great Lakes and several acidified lakes, ranged from 0 to 83 d per summer. Of this variation, 65% (54%) is accounted for by average phosphorus (nitrogen) concentration and an indicator of lake shape, z̄/A00.5 (where z̄ is mean depth). Only 17% on average was explained by annual dissolved organic C (DOC) concentration. Annual variation within lakes was large and partly ascribed to variable annual loading of DOC. AF was not correlated with areal hypolimnetic oxygen depletion, because of the opposing dependency on lake shape, but was correlated with Reckhow’s probability of anoxia in eutrophic lakes. AF was also correlated with the redox potential of anoxic water at the end of summer stratification, especially after inclusion of an estimate of iron concentration in the sediment.
Methane dynamics across a tidally flooded riverbank margin
Authors: Kelley Cheryl A. , Martens Christopher S. , Ussler William
Published: May 2010

The cycling of methane across the soils of the tidally flooded bank margins in the tidal freshwater portion of the White Oak River estuary, North Carolina, was investigated from October 1990 to November 1991. A comparison between these bank edges and adjacent submerged stations was made. The bank stations showed large seasonal variations in methane production rates, with very little being produced in winter and large amounts (up to 1,000 mg m−2 d−1) during summer. This seasonality seems to be linked to the cycle of growth and senescence of vascular plants growing in these soils. In contrast, the submerged stations produced smaller amounts of methane year‐round, with moderate increases during summer. Vascular plants are not rooted in these submerged sediments.

Seasonal variations in methane production rates at the tidally flooded bank stations led to significant changes in the dissolved methane pool sizes. Although production rates and pore‐water concentrations increased with seasonal increases in soil temperatures, the flux of methane to the atmosphere remained fairly low and variable. Methane flux varied with stage of the semidiurnal tidal cycle and exhibited a bimodal distribution, with fluxes greatest when the water level was nearest the soil surface. During summer months, methane production was up to 10 times greater than its flux to the atmosphere. This large difference between production and flux is attributed mainly to bacterially mediated methane oxidation at the soil surface during low‐tide exposure and(or) in the root zone of plants. However, in midsummer, lateral export of dissolved methane from the bank soils, driven by tidal flushing, may account for almost 30% of this discrepancy between production and flux.
A novel, nondestructive bioassay for assessing areal chlorophyll a in hermatypic cnidarians
Authors: Thieberger Y. , Kizner Z. , Achituv Y. , Dubinsky Z.
Published: May 2010

Changes in coral coloration caused by various environmental factors such as eutrophication, thermal pollution, and rise in sedimentation levels prompted us to develop nondestructive tools for the early detection of destabilization of the zooxanthellae‐coral symbiosis. We describe a method that can be used to assess coral pigmentation. This method is based on a correlation between the areal Chl a measurement and spectrophotometric analysis of a photographic slide of the same coral. Optical density values of the color slide are then converted into corresponding Chl a concentrations. This method can be used for the nondestructive assessment of chlorophyll concentration. A visual field bioassay based on this relationship is demonstrated. A laminated photograph of common corals of different shades of color and different chlorophyll content is used for the underwater evaluation of the pigmentation of living corals.
Trophic relations between cyclopoid copepods and ciliated protists: Complex interactions link the microbial and classic food webs
Authors: Wickham Stephen A.
Published: May 2010

Two field experiments examined the effects of cyclopoid copepods on ciliates. The presence or absence of Cyclops abyssorum, Cyclops kolensis, and zooplankton > 64 µm was manipulated to determine the relative importance of direct cyclopoid predation on protists vs. indirect effects mediated through cyclopoid predation on other metazooplankton. In the second experiment, presence or absence of C. abyssorum was cross‐classified with five concentrations of the metazooplankton community. Cyclopoid effects on ciliates were dependent on predator and prey species and on the abundance of alternate prey for cyclopoids. A trophic cascade was also observed, but only for two small ciliates, and only with the larger C. abyssorum. C. abyssorum had a stronger predation effect on oligotrich ciliates when metazooplankton had been removed, and this effect appeared at a lower metazooplankton concentration with a larger ciliate, compared to a smaller species of the same genus. These results suggest that for cyclopoid‐ciliate interactions, switching behavior in the predator may be at least as important as a trophic cascade.
Algal nutrient limitation affects rotifer growth rate but not ingestion rate
Authors: Rothhaupt Karl O.
Published: May 2010

The food algae Scenedesmus acutus and Cyclotella meneghiniana were grown in chemostats in a modified WC medium at identical growth rates (0.4 d‒1) but under different nutrient regimes. Nitrate or phosphate was reduced to produce N‐ or P‐limited algae. Brachionus rubens did not differentiate between nonnutrient‐limited and nutrient‐limited Scenedesmus and ingested both at comparable rates. The rotifers reached highest maximum growth rates with nonnutrient‐limited Scenedesmus. N‐limited Scenedesmus permitted similar growth rates at low food concentrations (below the incipient limiting level, ILL), but maximum growth rates at high food concentrations (above the ILL) were significantly reduced. With regard to the high N content of Brachionus, direct mineral N deficiency of the food appears to be possible. P‐limited algae (Scenedesmus and Cyclotella) permitted no positive growth rates of the rotifers at all. P‐limited algae that were short‐term enriched with phosphate contained similar amounts of P as nonnutrient‐limited algae but still were of lower nutritional quality, thus suggesting the importance of essential biochemical constituents.
Biochemical versus mineral limitation in Daphnia
Authors: Müller‐Navarra Dörthe C.
Published: May 2010

Laboratory growth experiments were used to test whether observed phosphorus limitation in Daphnia is a direct effect of P availability. Daphnia was fed the algae Cyclotella and Scenedesmus, each P saturated or P limited. The algal species were chosen because of their distinct fatty acid composition, particularly with respect to their eicosapentaenoic acid (20:5ω3) content. Although both algal species had reduced 20:5ω3 content under P limitation, P‐limited Cyclotella had a substantially higher 20:5ω3 content than did P‐saturated Scenedesmus. In keeping with its P and 20:5ω3 content, P‐limited Scenedesmus was the lowest quality of food. Inconsistent with mineral P limitation in Daphnia but in agreement with the 20:5ω3 content, P‐starved Cyclotella was a better quality of food than was P‐sufficient Scenedesmus. Thus P limitation seems to be a rather indirect effect of changes in algal biochemical composition in response to nutrient stress.
Distribution of holothurian larvae determined with species‐specific genetic probes
Authors: Medeiros‐Bergen Dorothy E. , Olson Richard R. , Conroy Janet A. , Kocher Thomas D.
Published: May 2010

Identification of marine invertebrate larvae to the species level is often difficult due to morphological similarity and phenotypic plasticity. To study dispersal of morphologically indistinguishable holothurian larvae, we developed a simple detection protocol that uses a series of oligonucleotide probes for the 16S rRNA portion of the mitochondrial DNA genome; this protocol may be feasible for use onboard research vessels. Using our technique, we analyzed >1,800 larvae from collections made during spring 1993 in the western Gulf of Maine. Of the three species present in the plankton, Cucumaria frondosa larvae dominated the samples, often comprising >90% of the larval pool and 95% of new recruits. Temporal differences in planktonic distribution suggest the southward transport of C. frondosa. The vertical distribution of larvae over time suggests that larvae are located primarily in the upper coastal waters. The presence of C. frondosa larvae in the coastal waters of New Hampshire represents a loss to recruitment because C. frondosa adults are extremely rare in this area.
The measurement of microbial carbohydrate exopolymers from intertidal sediments
Authors: Underwood G. J. C. , Paterson D. M. , Parkes R. J.
Published: May 2010

Measurements of microbial extracellular polymeric substances (EPS) of natural field populations are required to understand the processes of biogenic stabilization and the microbial ecology of intertidal sediments. EPS in sediments can be measured by the phenol‐sulfuric acid assay to measure carbohydrate concentration in sediment samples. We conducted comparative studies of storage and extraction methods for carbohydrate fractions on intertidal estuarine sediments. Measurements of both total and colloidal (material remaining in suspension after aqueous extraction and centrifugation) carbohydrate concentrations were highly dependent on storage conditions, sample size, extraction media, and time. Precipitation (in 70% ethanol) of EPS from saline (25‰) extractions of colloidal carbohydrate (colloidal S) from four different sediment microbial assemblages showed that 20% of colloidal carbohydrate present in extracts consisted of EPS. Concentrations of colloidal S were highly correlated with diatom biomass as determined by chlorophyll a concentrations. Extractions that used 100 mM Na2EDTA as the extracting medium (colloidal EDTA) increased the concentrations of colloidal carbohydrate obtained and, in sediments dominated by bacteria and cyanobacteria, increased the percentage of EPS in the material to 38%. Uronic acids comprised 20% of the total amount of carbohydrate measured in both total sediment and colloidal‐S extracts but increased to 65% in colloidal‐EDTA extracts, suggesting that colloidal‐EDTA extractions remove bacterial capsular EPS and EPS more closely associated with sediment particles.
Origin and distribution of inositol hexaphosphate in estuarine and coastal sediments
Authors: Suzumura Masahiro , Kamatani Akiyoshi
Published: May 2010

In order to clarify the origin and the fate of inositol hexaphosphate (IP6) in coastal sediments from Tokyo Bay, we determined IP6 in several potential source materials, such as plankton, soil, riverine, and estuarine samples. IP6 was not found in zoo‐ and phytoplankton samples, thus eliminating these as a source to the sediments. Soils collected from the catchment areas of major rivers flowing into the bay contained high concentrations of IP6 (0.25–5.65 µmol P g‒1). Samples of suspended solids and estuarine sediments from the rivers also had significant amounts of IP6. The distribution pattern of IP6 in Tokyo Bay sediments exhibited relatively high concentrations in the estuarine areas, decreasing gradually toward the mouth of the bay. The IP6 in coastal sediments was composed of three isomers in the same order of abundance as those found in the terrestrial and riverine samples: myo‐ » scyllo‐ > chiro‐. From these results, IP6 in Tokyo Bay sediments was ascribed to soils transported by rivers from land into the bay. The IP6 concentration ranged from 0.01 to 0.10 µmol P g ‒1 in surface sediments (0–2.5 cm), accounting for <1.2% of the total organic P; it was completely decomposed in the subsurface. Consequently, this compound is quite ephemeral in coastal marine environments.
An experimental test of the intermediate disturbance hypothesis using cultures of marine phytoplankton
Authors: Sommer Ulrich
Published: May 2010

Connell's intermediate disturbance hypothesis (IDH) predicts that species richness and diversity within a community are maximal at intermediate frequencies and intensities of disturbances. The predictions of the IDH were tested experimentally by semicontinuous multispecies cultures of marine phytoplankton. Disturbances consisted of dilutions at fixed intervals. The disturbances eliminated parts of the experimental populations but supplied fresh nutrients. Intervals between disturbances ranged from 1 to 14 d. The magnitude of dilutions ranged from 30 to 99% removal. The IDH was fully supported when the results were expressed as species numbers or as Shannon's diversity index based on biomass. On the other hand, the IDH was only partially supported when the results were expressed as Shannon's diversity index based on cell numbers.
Encounter rates and swimming behavior of pause‐travel and cruise larval fish predators in calm and turbulent laboratory environments
Authors: MacKenzie Brian R. , Kiørboe Thomas
Published: May 2010

We observed the feeding and swimming behavior of freely swimming cod (Gadus morhua) and herring (Clupea harengus) larvae in calm and turbulent (ɛ = ~7.4 × 10 ‒8 m2 s‒3) laboratory environments at limiting and satiating abundances of Acartia tonsa prey. Attack position rates (a measure of prey encounter rate in unsatiated larvae) were significantly higher in turbulent than in calm water at low food abundances for two size groups of cod. The difference in cod attack position rate between calm and turbulent water was much less when prey was more abundant. Attack position rates of herring larvae were higher in turbulent water than in calm water, but the difference was not significant. Interspecific differences in swimming and pausing behavior were related to differences in prey search strategy used by the two species (cod: pause‐travel; herring: cruise). We used a newly developed search model for pause‐travel predators in calm and turbulent environments to compare encounter rates for predators using cruise and pause‐travel search strategies. Encounter rates for cod and herring larvae, estimated with respective search models, were similar in calm and low turbulence water; at high turbulence levels, the pause‐travel model predicts higher encounter rates than does the cruise model. In terms of prey encounter rate, cod larvae benefit more from turbulent motion than do herring larvae. However, aspects of larval behavior other than prey search strategy (e.g. prey capture success) need to be examined experimentally before the overall effects of turbulence on larval fish feeding rates can be fully evaluated.
Differentiation between littoral and pelagic food webs in lakes using stable carbon isotopes
Authors: France Robert L.
Published: May 2010

As a result of exposure to low water turbulence, periphyton are enriched in 13C compared to phytoplankton. Because of this, benthic consumers in marine coastal environments are also 13C enriched relative to planktonic consumers. I analyzed the δ13C values for biota from four Canadian Shield lakes and similarly found 13C enrichment in littoral compared to pelagic consumers. A compilation of literature data indicates that an uncoupling of carbon flows between benthic and planktonic food webs may be a characteristic feature of lakes worldwide.
Influences of absorption and scattering on vertical changes in the average cosine of the underwater light field
Authors: Berwald Juli , Stramski Dariusz , Mobley Curtis D. , Kiefer Dale A.
Published: May 2010

The average cosine of the underwater light field (µ̄) is a simple quantity that describes the angular distribution of radiance at a given point. A model of the rate of vertical change of µ̄ in the ocean was developed in order to examine the influences of light absorption and scattering. We made calculations of radiative transfer based on invariant imbedding theory assuming an optically homogeneous ocean with a typical scattering phase function and the simple boundary conditions of the sun overhead in a black sky and a flat ocean surface. Under such conditions, the decrease of µ̄ throughout the water column is well approximated by a single exponential function. The dependence of the parameter Pτ, which describes the rate of change of µ̄ with optical depth, on the single‐scattering albedo ωo, is well approximated by a quadratic function. By applying a linearization technique to the Pτ vs. ωo relationship, we identified the contributions of absorption and scattering to Pτ. Our results indicate that scattering is the more important process, contributing > 50% to Pτ for typical situations when ωo > 0.1. Absorption dominates Pτ when ωo < 0.1, which occurs only in very clear oceanic water at long wavelengths (>650 nm). Our analysis of the effect of scattering phase function shows that the scattering into the middle angles, approximately between 20° and 45°, largely determines the magnitude of Pτ. Using spectral bio‐optical models with several Chl concentrations, we also examined the rate of change in µ̄ with geometric depth Pz for various water types with realistic values of the absorption and scattering coefficients. This analysis shows large variations in both the magnitude and the spectral behavior of Pz with varying Chl concentration.
The attenuation of solar UV radiation in lakes and the role of dissolved organic carbon
Authors: Morris Donald P. , Zagarese Horatio , Williamson Craig E. , Balseiro Esteban G. , Hargreaves Bruce R. , Modenutti Beatriz , Moeller Robert , Queimalinos Claudia
Published: May 2010

Diffuse attenuation coefficients (Kd) for solar UV radiation (UVR) (305, 320, 340, 380 nm, and PAR) were measured in the mixed layer of 65 lake sites in Alaska, Colorado, and Pennsylvania and the Bariloche region of Argentina. Integrated mixed layer samples of lake water were concurrently collected, and a multivariate approach was used to model Kd with a number of optical and chemical variables.

Substantial variation in transparency was observed among lakes. Attenuation depths (z1%) for UV‐B radiation ranged from several centimeters to > 10 m. In some shallow, low DOC (dissolved organic C) lakes typical of high elevation ecosystems, substantial fluxes of UVR penetrated the entire water column. In deeper lakes with low DOC concentrations, high fluxes of UVR were found in a significant proportion of the mixed layer. Much of the among‐lake variation in Kd (87–96%) was explained by differences in DOC concentration, which strongly influenced dissolved absorbance. On average, dissolved absorbance accounted for between 33% (for PAR) and 68% (for 305 nm) of Kd measured in situ. Throughout the solar UV‐A and UV‐B range, Kd was best estimated with a univariate power model based solely on DOC concentration. Models are also presented that relate absorption coefficients to Kd. These models can be used with archival DOC or color data to provide approximate estimates of UV transparency of lakes.
Regeneration of trace metals from picoplankton by nanoflagellate grazing
Authors: Twiss Michael R. , Campbell Peter G. C.
Published: May 2010

Rapid regeneration of trace metals from the particulate to the dissolved phase (<0.2 µm) was observed in the laboratory with a simplified microbial food web composed of mixotrophic chrysophycean nanoflagellates (Ochromonas danica) grazing on picocyanobacteria (Synechococcus leopoliensis) that had been previously exposed to the radionuclides 153Gd(III), 65Zn(II), 109Cd(II), and 137Cs(I). These trace metals were chosen to represent a range of surface reactivities with particles (Gd>Zn, Cd»Cs). Grazing experiments and the appropriate nongrazing controls were carried out in batch cultures over 43–49 h in defined, inorganic freshwater medium; metal partitioning among the consumer, prey, and dissolved phases was determined by sequential filtration (3 µm, 0.2 µm) at timed intervals. Most of the trace metals consumed as radioactive prey were regenerated into the dissolved phase. Regenerated Gd, Zn, and Cd present in the dissolved phase were less available for resorption by plankton than were the same radionuclides added in inorganic form to fresh growth medium. Our results suggest that where this grazing activity exists, it will serve to increase trace metal residence times in the water column.
Aerobic and anaerobic decomposition of organic matter in marine sediment: Which is fastest?
Authors: Kristensen Erik , Ahmed Saiyed I. , Devol Allan H.
Published: May 2010

The enigma of aerobic vs. anaerobic decomposition in marine sediments was addressed by means of a thin‐layer incubation technique. Two different 14C‐labeled plant materials, aged diatoms (Skeletonema costatum) and fresh barley hay, were each mixed into intertidal sediment and spread in a 1.5‐mm layer on the bottom of oxic and anoxic chambers. After a 27‐d incubation, conditions in all chambers were switched from aerobic to anaerobic and vice versa for 11 d. Rates of 14CO2 evolution in diatom chamhers showed that aerobic carbon mineralization was ~10 times faster than anaerobic both before and after the switch. Low rates of [14C]DOC release suggested that the limiting step of anaerobic decay was the initial hydrolytic and fermentative enzymatic attack the predecomposed diatoms. Initial carbon mineralization of barley hay was not affected by the presence or absence of oxygen. Leaching of DOC from the fresh barley hay supplied anaerobic respirers with labile substrates. When leaching ceased and after the aerobic‐anaerobic switch, the rate of anaerobic mineralization was reduced. Mineralization of leachable and easily hydrolyzable compounds from fresh plant detritus is equally fast under aerobic and anaerobic conditions. When structural components dominate the particulate remains, anaerobic processes are hampered by inefficient and slow bacterial hydrolysis of structurally complex macromolecules.
Acidification signals in estuarine sediment cores
Authors: Egeberg Per Kristian
Published: May 2010

The hypothesis that estuarine sediment cores contain signals which can be used to reconstruct shifts in the concentration of riverine humic matter (HM) and dissolved aluminum (Al) during acidification is examined. Dated sediment cores from Topdal Fjord (southern Norway) were analyzed for humic matter and alkaline extractable Al. The proportions of riverine and marine HM were estimated from carbon‐to‐nitrogen ratios (C: N). The results agree qualitatively and quantitatively with predictions based on Al and HM behavior in estuaries and the suspected effect of acidification on the concentration of these parameters. The doubling in the concentration of riverine Al and 50% reduction in riverine HM in sediment cores from the Topdal estuary coincide with an abrupt increase in the proportion of Topdal River discharge originating from areas in which the critical loads of acidity have been exceeded by sulfur deposition. HM started to decrease and Al started to increase concurrently with declining catches of Atlantic salmon around a.d. 1900.
Generation of a Chattonella antiqua bloom by imposing a shallow nutricline in a mesocosm
Authors: Watanabe Masataka , Kohata Kunio , Kimura Toshihiko , Takamatsu Takejiro , Yamaguchi Shin‐ichiro , Ioriya Teru
Published: May 2010

A mesocosm was installed in the Seto Inland Sea where outbreaks of Chattonella antiqua (red tide) have frequently been observed. An artificial, shallow (6‐m depth) nutrient stratification analogous to that observed with C. antiqua in nature was imposed. The initial bottom temperature of 20–22°C was optimum for C. antiqua excystment as seeding, and the surface temperature of 25–27°C was optimum for growth. Excess nitrogen and phosphate compared with silicate changed the phytoplankton community from a mixture of diatoms and dinoflagellates to one of dinoflagellate dominance. Absence of copper toxicity was essential for growth of C. antiqua. Cessation of vertical circulation promoted accumulation of dinoflagellates at the water surface, and selective grazing toward small‐size dinoflagellates by zooplankton controlled the population of dinoflagellates.

C. antiqua could reach a depth of 7.5 m during diel vertical migration, and its migration speed was ~0.8 m h‒1; upward and downward speeds were the same. Outbreaks of C. antiqua were favored by artificial eutrophication and subsequent maintenance of a stable, shallow nutricline at a depth (6 m) such that C. antiqua could take up nutrients in the nutrient‐rich lower layer at night.
Influence of turbulence on bacterial production in the sea
Authors: Moeseneder Markus M. , Herndl Gerhard J.
Published: May 2010

The role of turbulence on heterotrophic bacterial production (BP) was tested in batch cultures in the laboratory and under in situ conditions. BP was significantly higher under stagnant conditions (∼19%) in the presence of particles such as phytoplankton. Turbulence in the upper mixed layer of the sea significantly altered in situ BP over a 14‐d period. During calm periods, BP was significantly (P ≤ 0.0025) higher in the stagnant treatment, while during a period of high turbulence, BP was not significantly (P = 0.13) different in either experimental treatment. In laboratory experiments, BP was higher under turbulent conditions (P = 0.064) after agitating seawater for 24 h, while in the undisturbed control, BP was significantly higher (P = 0.009) under stagnant conditions. Removing particles other than bacteria led to BP that was similar in both stagnant and turbulent treatments. Additions of glucose or leucine (100 µM and 1 mM final concn) to seawater containing phytoplankton generally reduced the difference in BP between stagnant and turbulent conditions. Our results suggest that variations in turbulence modify bacterioplankton community structure in the upper layer of the sea.
Impacts of an introduced predatory fish on mayfly grazing in New Zealand streams
Authors: McIntosh Angus R. , Townsend Colin R.
Published: May 2010

The replacement of native common river galaxias (Galaxias vulgaris Stokell) by introduced brown trout (Salmo trutta L.) in many streams of the Taieri River system, New Zealand, has altered the predation regime for Deleatidium mayfly nymphs. Brown trout present a higher predation risk to mayfly prey during the day than at night but common river galaxias present similar risks both day and night. To determine whether this alteration has changed mayfly grazing behavior, we investigated the diel gut fullness of Deleatidium nymphs in five galaxias streams and five trout streams. Gut fullness was measured by the fluorescence of algal pigments extracted from Deleatidium guts. Nymphs from trout streams generally had fuller guts at night, whereas nymphs from galaxias streams tended to have more in their guts during the day or similar amounts both day and night. The difference reflects the high predation risk presented by brown trout during the day, restricting mayfly access to the algae‐rich upper surfaces of stones. These results indicate that the influence of predatory fish on mayfly grazing is detectable at a large spatial scale in the Taieri River system.
Dispersal dynamics in a wind‐driven benthic system
Authors: Commito J. A. , Thrush S. F. , Pridmore R. D. , Hewitt J. E. , Cummings V. J.
Published: May 2010

Bedload and water column traps were used with simultaneous wind and water velocity measurements to study postlarval macrofaunal dispersal dynamics in Manukau Harbour, New Zealand. A 12‐fold range in mean wind condition resulted in large differences in water flow (12‐fold), sediment flux (285‐fold), and trap collection of total number of individuals (95‐fold), number of the dominant infaunal organism (84‐fold for the bivalve Macomona liliana), and number of species (4‐fold). There were very strong, positive relationships among wind condition, water velocity, sediment flux, and postlarval dispersal, especially in the bedload. Local density in the ambient sediment was not a good predictor of dispersal. Results indicate that postlarval dispersal may influence benthic abundance patterns over a range of spatial scales.
Natural dispersion in a small lake
Authors: Lawrence Gregory A. , Ashley Ken I. , Yonemitsu Noboru , Ellis Joanne R.
Published: May 2010

Videotapes of dye dispersion experiments in the epilimnion of a small lake were successfully analyzed with image‐processing techniques. The rate of horizontal dispersion from dye releases in the center of the lake was consistent with previous observations in oceans and large lakes. We derive a power‐law relationship that relates the apparent diffusivity to the characteristic length scale of the dye patch. This relationship applies to all three data sets and is valid over length scales ranging from 10 m to more than 100 km. Dye releases from a point on the shore of the same lake dispersed slightly faster than the central releases. This observation, while clearly not universal, has prompted the successful shore‐based fertilization of several small lakes.
A new method for measuring spectral absorption coefficients of marine particles
Authors: Allali Karima , Bricaud Annick , Babin Marcel , Morel André , Chang Patrick
Published: May 2010

A new method has been developed to measure the light absorption coefficients of marine particles. The procedure, adapted from one proposed earlier for microscopic observation of nanoplankton, consists of concentrating particles onto a Nuclepore filter, transferring the filtered material to a glass microscope slide using liquid nitrogen freezing, and finally measuring the particle absorption spectrum on the slide. Measurements on various phytoplanktonic species show that the transfer efficiency is 94–98% and that no alteration of absorption spectra occurs. Our new method has been tested successfully on both phytoplankton‐dominated and detritus‐dominated field samples. In comparison with the widely used glass‐fiber filter technique, the major advantage of our procedure is to provide more accurate absorption coefficients, since the pathlength amplification effect (β factor) and its attached uncertainties are completely eliminated.
Black carbon aerosols and the third polar ice cap
Authors: Menon S. , Koch D. , Beig G. , Sahu S. , Fasullo J. , Orlikowski D.
Published: May 2010

Abstract. Recent thinning of glaciers over the Himalayas (sometimes referred to as the third polar region) have raised concern on future water supplies since these glaciers supply water to large river systems that support millions of people inhabiting the surrounding areas. Black carbon (BC) aerosols, released from incomplete combustion, have been increasingly implicated as causing large changes in the hydrology and radiative forcing over Asia and its deposition on snow is thought to increase snow melt. In India BC emissions from biofuel combustion is highly prevalent and compared to other regions, BC aerosol amounts are high. Here, we quantify the impact of BC aerosols on snow cover and precipitation from 1990 to 2010 over the Indian subcontinental region using two different BC emission inventories. New estimates indicate that Indian BC emissions from coal and biofuel are large and transport is expected to expand rapidly in coming years. We show that over the Himalayas, from 1990 to 2000, simulated snow/ice cover decreases by ~0.9% due to aerosols. The contribution of the enhanced Indian BC to this decline is ~36%, similar to that simulated for 2000 to 2010. Spatial patterns of modeled changes in snow cover and precipitation are similar to observations (from 1990 to 2000), and are mainly obtained with the newer BC estimates.
A climatological perspective of deep convection penetrating the TTL during the Indian summer monsoon from the AVHRR and MODIS instruments
Authors: Devasthale A. , Fueglistaler S.
Published: May 2010

Abstract. The impact of very deep convection on the water budget and thermal structure of the tropical tropopause layer is still not well quantified, not least because of limitations imposed by the available observation techniques. Here, we present detailed analysis of the climatology of the cloud top brightness temperatures as indicators of deep convection during the Indian summer monsoon, and the variations therein due to active and break periods. We make use of the recently newly processed data from the Advanced Very High Resolution Radiometer (AVHRR) at a nominal spatial resolution of 4 km. Using temperature thresholds from the Atmospheric Infrared Sounder (AIRS), the AVHRR brightness temperatures are converted to climatological mean (2003–2008) maps of cloud amounts at 200, 150 and 100 hPa. Further, we relate the brightness temperatures to the level of zero radiative heating, which may allow a coarse identification of convective detrainment that will subsequently ascend into the stratosphere. The AVHRR data for the period 1982–2006 are used to document the differences in deep convection between active and break conditions of the monsoon. The analysis of AVHRR data is complemented with cloud top pressure and optical depth statistics (for the period 2003–2008) from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua satellite. Generally, the two sensors provide a very similar description of deep convective clouds. Our analysis shows that most of the deep convection occurs over the Bay of Bengal and central northeast India. Very deep convection over the Tibetan plateau is comparatively weak, and may play only a secondary role in troposphere-to-stratosphere transport. The deep convection over the Indian monsoon region is most frequent in July/August, but the very highest convection (coldest tops, penetrating well into the TTL) occurs in May/June. Large variability in convection reaching the TTL is due to monsoon break/active periods. During the monsoon break period, deep convection reaching the TTL is almost entirely absent in the western part of the study area (i.e. 60 E–75 E), while the distribution over the Bay of Bengal and the Tibetan Plateau is less affected. Although the active conditions occur less frequently than the break conditions, they may have a larger bearing on the composition of the TTL within the monsoonal anticyclone, and tracer transport into the stratosphere because of deep convection occurring over anthropogenically more polluted regions.
What do satellite backscatter ultraviolet and visible spectrometers see over snow and ice? A study of clouds and ozone using the A-train
Authors: Vasilkov A. P. , Joiner J. , Haffner D. , Bhartia P. K. , Spurr R. J. D.
Published: May 2010

Abstract. In this paper, we examine how clouds over snow and ice affect ozone absorption and how these effects may be accounted for in satellite retrieval algorithms. Over snow and ice, the Aura Ozone Monitoring Instrument (OMI) Raman cloud pressure algorithm derives an effective scene pressure. When this scene pressure differs appreciably from the surface pressure, the difference is assumed to be caused by a cloud that is shielding atmospheric absorption and scattering below cloud-top from satellite view. A pressure difference of 100 hPa is used as a crude threshold for the detection of clouds that significantly shield tropospheric ozone absorption. Combining the OMI effective scene pressure and the Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) cloud top pressure, we can distinguish between shielding and non-shielding clouds. To evaluate this approach, we performed radiative transfer simulations under various observing conditions. Using cloud vertical extinction profiles from the CloudSat Cloud Profiling Radar (CPR), we find that clouds over a bright surface can produce significant shielding (i.e., a reduction in the sensitivity of the top-of-the-atmosphere radiance to ozone absorption below the clouds). The amount of shielding provided by clouds depends upon the geometry (solar and satellite zenith angles) and the surface albedo as well as cloud optical thickness. We also use CloudSat observations to qualitatively evaluate our approach. The CloudSat, Aqua, and Aura satellites fly in an afternoon polar orbit constellation with ground overpass times within 15 min of each other. The current Total Ozone Mapping Spectrometer (TOMS) total column ozone algorithm (that has also been applied to the OMI) assumes no clouds over snow and ice. This assumption leads to errors in the retrieved ozone column. We show that the use of OMI effective scene pressures over snow and ice reduces these errors and leads to a more homogeneous spatial distribution of the retrieved total ozone.
Fast and simple model for atmospheric radiative transfer
Authors: Seidel F. C. , Kokhanovsky A. A. , Schaepman M. E.
Published: May 2010

Abstract. Radiative transfer models (RTMs) are of utmost importance for quantitative remote sensing, especially for compensating atmospheric perturbation. A persistent trade-off exists between approaches that prefer accuracy at the cost of computational complexity, versus those favouring simplicity at the cost of reduced accuracy. We propose an approach in the latter category, using analytical equations, parameterizations and a correction factor to efficiently estimate the effect of molecular multiple scattering. We discuss the approximations together with an analysis of the resulting performance and accuracy. The proposed Simple Model for Atmospheric Radiative Transfer (SMART) decreases the calculation time by a factor of more than 25 in comparison to the benchmark RTM~6S on the same infrastructure. The approximative computation of the atmospheric reflectance factor by SMART has an uncertainty ranging from about 5% to 10% for nadir spaceborne and airborne observational conditions. The combination of a large solar zenith angle (SZA) with high aerosol optical depth (AOD) at low wavelengths lead to uncertainties of up to 15%. SMART can be used to simulate the hemispherical conical reflectance factor (HCRF) for spaceborne and airborne sensors, as well as for the retrieval of columnar AOD.
An overview of measurement comparisons from the INTEX-B/MILAGRO airborne field campaign
Authors: Kleb M. M. , Chen G. , Crawford J. H. , Flocke F. M. , Brown C. C.
Published: May 2010

Abstract. As part of the NASA's INTEX-B mission, the NASA DC-8 and NSF C-130 conducted three wing-tip to wing-tip comparison flights. The intercomparison flights sampled a variety of atmospheric conditions (polluted urban, non-polluted, marine boundary layer, clean and polluted free troposphere). These comparisons form a basis to establish data consistency, but also should also be viewed as a continuation of efforts aiming to better understand and reduce measurement differences as identified in earlier field intercomparison exercises. This paper provides a comprehensive overview of 140 intercomparisons of data collected during INTEX-B. For interpretation and most effective use of these results, the reader is strongly urged to consult with the instrument principle investigator.
Satellite traces, range spread-F occurrence, and gravity wave propagation at the southern anomaly crest
Authors: Cabrera M. A. , Pezzopane M. , Zuccheretti E. , Ezquer R. G.
Published: May 2010

Abstract. Range spread-F (RSF) and occurrence of "satellite" traces prior to RSF onset were studied at the southern peak of the ionospheric equatorial anomaly (EA). Ionograms recorded in September 2007 at the new ionospheric station of Tucumán, Argentina (26.9° S, 294.6° E, dip latitude 15.5° S), by the Advanced Ionospheric Sounder (AIS) developed at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), were considered. Satellite traces (STs) are confirmed to be a necessary precursor to the appearance of an RSF trace on the ionograms. Moreover, an analysis of isoheight contours of electron density seems to suggest a relationship between RSF occurrence and gravity wave (GW) propagation.
Rainfall leads to increased pCO2 in Brazilian coastal lakes
Authors: Marotta H. , Duarte C. M. , Pinho L. , Enrich-Prast A.
Published: May 2010

Abstract. The variation of partial pressure of CO2 (pCO2), pH, salinity and dissolved organic carbon (DOC) in surface waters of 12 coastal Brazilian lakes was examined following periods of contrasting rainfall. Periods of high rainfall were followed by a large, almost 10 fold, increase in pCO2 and a one unit decrease in pH in the lakes, whereas no consistent changes in DOC were observed. CO2 emissions to the atmosphere from the Brazilian coastal lakes studied here were highly enhanced, on average, from 28.5 ± 6.0 mmol C m−2 d−1 in dry periods to 245.3.1 ± 51.5 mmol C m−2 d−1 following periods of heavy rainfall. The increased inputs of pCO2 following periods of high rainfall are believed to be derived from increased inputs of pCO2 from groundwaters to the lakes.
Synthesis and characterization of polyacrylamides containing meso‐2,3‐dimercaptosuccinic acid end groups
Authors: Özeroğlu Cemal , Bi̇rdal Arzu
Published: May 2010

By using meso‐2,3‐dimercaptosuccinic acid‐cerium(IV) sulfate and meso‐2,3‐dimercaptosuccinic acid‐potassium permanganate redox systems, the polymerization reaction of acrylamide (AAm) monomer was examined in aqueous acidic medium at low temperatures. Water‐soluble polyacrylamides bearing meso‐2,3‐dimercaptosuccinic acid end groups were synthesized using meso‐2,3‐dimercaptosuccinic acid as a reducing agent. The effects of parameters such as the molar ratio of acrylamide to initiator, temperature, polymerization time, and sulfuric acid concentration on the yields and molecular weights of polymers were investigated. The augmentation in initiator concentration resulted in a decrease in molecular weight but an increase in the yield of polymers. The increase in reaction temperature from 20 to 60°C led to a decrease in the yield from 56.80% to 20.58%. Ce(IV) and Mn(VII) ions are reduced to Ce(III) and Mn(II) ions in the polymerization reaction and the synthesized acrylamide polymers containing meso‐2,3‐dimercaptosuccinic acid end groups can absorb these ions at the end of the polymerization reaction. Ultraviolet‐visible and atomic absorption measurements of polymer solutions were performed to indicate complexation between polyacrylamide and Ce(III) ions or Mn(II) ions. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:45–53, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20180
Systematic optimization for the evaluation of the microinjection molding parameters of light guide plate with TOPSIS‐based Taguchi method
Authors: Su Te‐Li , Chen Hua‐Wei , Lu Chieh‐Fu
Published: May 2010

A back light module is a key product for providing sufficient light source for a liquid crystal display (LCD). The light guide plate (LGP), used to increase the light usage rate, is a key component in the back light module. This study researches the microinjection molding process parameters and the quality performance of the LGP. Its purpose was to develop a combining Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) with the Taguchi method. This is to optimize the multiquality performance of the LGP for the injection molding manufacturing process, in which both the LCD and the LGP spontaneously produce the best quality performance for V‐cut depth and angle. First, an L18 orthogonal array was planned for the manufacturing parameters that affect the microinjection molding process. These included cooling time, mold temperature, melt temperature, injection speed, injection pressure, packing pressure, packing switching, and packing time. The TOPSIS was used to deal with the single‐quality optimization disadvantage of the Taguchi method. Then, the TOPSIS response table was used to obtain the optimized manufacturing parameters combination for a multiresponse process optimization. From the analysis of variance, the significant factors for the quality performance of the LGP could be obtained. In other words, by controlling these factors, it was possible to efficiently control the quality performance of the LGP. Finally, with the five verified experiments, the optimized processing parameters came within a 95% confidence interval. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:54–63, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20181