bluuebunny/crossref_metadata_2025 huggingface dataset:
An evaluation of wet chemical methods for quantifying sulfur fractions in freshwater wetland peat1
Authors: Wieder R. Kelman , Lang Gerald E. , Granus Valerie A.
Published: April 2010

The specificity and efficiency of procedures for fractionating total S into inorganic and organic constituents were evaluated by analyzing a series of known standards. Acid volatilization was specific for FeS. Chromium reduction recovered over 90% of the S from FeS, S0, and FeS2. Acetone extraction followed by chromium reduction of the filtrate was specific for S0. Hydriodic acid reduction recovered > 90% of the S from FeS, SO42−, and p‐nitrophenyl sulfate, an organic aryl ester sulfate analog. The Zn‐HCl reduction procedure is of questionable value, only partially recovering S from SO42−, S0, and FeS2. None of these procedures affected l‐methionine. Analyses were performed on both moist and oven‐dried peat from Big Run Bog, West Virginia. Oven‐drying of peat samples increased estimates of ester sulfate S and SO42−‐S and decreased estimates of carbon‐bonded S, which was calculated by difference.
Effects of El Niño on local hydrography and growth of the giant kelp, Macrocystis pyrifera, at Santa Catalina Island, California1
Authors: Zimmerman Richard C. , Robertson Deborah L.
Published: April 2010

Deepened isotherms associated with El Niño resulted in severe nutrient limitation and very low kelp productivity during the last half of 1983. Frond growth rates were so low that terminal blades formed before reaching the surface, eliminating the canopy. Frond initiation rates were also extremely low, resulting in significant reductions in mean plant size. Plants growing above 10 m were more severely affected than plants at 20 m. These results suggest that nutrient pulses associated with internal waves are critical for survival of Macrocystis pyrifera in nutritionally marginal habitats in southern California.
Measurement of the carbon balance in Daphnia1
Authors: Lynch Michael , Weider Lawrence J. , Lampert Winfried
Published: April 2010

Short term measures of assimilation and respiration rates of four species of Daphnia consistently lead to the prediction that the relation between body mass and net carbon intake, F(B), should be close to linear. Yet a more direct estimation of F(B) based on observed investments in growth and reproduction indicates that the true relationship is nonlinear with a roughly constant value of F maintained beyond the size at maturity. Several experiments demonstrate that our direct measures of F(B) are not greatly influenced by the experimental protocol. Hence, we conclude that short term measures of physiological parameters cannot be extrapolated to estimate growth and reproductive rates of Daphnia. Despite the existence of significant physiological differences between species, our results further reveal a conservative relation between age and the pattern of energy allocation to growth and reproduction in the genus and suggest that the evolution of Daphnia life histories is strongly regulated by one key character— the size at maturity.
An empirical analysis of zooplankton community size structure across lake trophic gradients1
Authors: Pace Michael L.
Published: April 2010

The hypothesis was tested that zooplankton community size structure shifts toward an increased relative biomass of microzooplankton with increased lake trophy at 12 sites in Quebec. The seasonal mean abundance and biomass of ciliates, rotifers, nauplii, cladocerans, and cyclopoid copepods were significantly (P < 0.1) related to lake trophy, but calanoid copepod abundance and biomass varied independently of lake trophy. Regressions of microzooplankton and macrozooplankton biomass with total phosphorus (TP) were highly significant (P < 0.0001), and TP explained a large proportion of the total variation (microzooplankton: r2 = 0.72; macrozooplankton: r2 = 0.86). The regression models for microzooplankton and macrozooplankton were not significantly different, refuting the hypothesis that relative biomass changes with lake trophy. Further analysis with a community structure index (the slope of the log weight‐log abundance relationship) and mean lengths of various taxa indicated that zooplankton community size structure was not correlated with either TP or chlorophyll. On average, about 40% of the total zooplankton biomass is accounted for by microzooplankton in the Quebec lakes. The inverse relationship between body size and specific flux rates suggests that microzooplankton account for the major portion of zooplankton community rates.
Biogeochemical cycling of lignocellulosic carbon in marine and freshwater ecosystems: Relative contributions of procaryotes and eucaryotes1
Authors: Benner Ronald , Moran Mary Ann , Hodson Robert E.
Published: April 2010

The relative contributions of procaryotes and eucaryotes to the degradation of the lignin and polysaccharide components of lignocellulosic detritus in two marine and two freshwater wetland ecosystems were determined. Two independent methods—physical separation of bacteria from fungi and other eucaryotes by size fractionation, and antibiotic treatments— were used to estimate procaryotic and eucaryotic contributions to the degradation of [14C‐lignin]lignocelluloses and [14C‐polysaccharide]lignocelluloses in samples of water and decaying plant material from each environment. Both methods yielded similar results; bacteria were the predominant degraders of lignocellulose in each of the aquatic ecosystems. Fungi and other eucaryotes contributed only minimally to the overall degradation of lignocellulose in both marine ecosystems and in the Okefenokee Swamp but did contribute significantly to the degradation of lignocellulose in the Big Cypress Swamp. These results indicate a basic difference between the microbial degradation of lignocellulosic material in terrestrial and aquatic environments. Fungi have long been considered the predominant degraders of lignocellulose in terrestrial systems; our results indicate that in aquatic systems bacteria are the predominant degraders of lignocellulose.
Dissolved hydrocarbon metabolism: The concentration‐dependent kinetics of toluene oxidation in some North American estuaries1
Authors: Button D. K. , Robertson B. R.
Published: April 2010

The metabolism of toluene by natural populations of marine bacteria, stored to enhance their activity, gave hyperbolic kinetics with saturation at only Kt = 0.6 to 3.4 µg liter−1. Similarly Kt in fresh seawater was 0.26 µg toluene liter−1. Freshly collected populations could be moderately active toward toluene, affinity a2A = 1.1−37.5 liters g‐cells−1 h−1. These moderate affinities taken together with the small Kt values give an explanation for the failure of most marine bacteria to grow at the expense of a single hydrocarbon.

In two experiments there was a significant first‐order region in toluene in the 10–50 µg liter−1 range. When cultures of Pseudomonas sp. strain T2 were cast in suspended agar blocks to impede diffusion, toluene oxidation still followed hyperbolic kinetics although CO2 production and organic product formation were characterized by larger Michaelis constants.

A large widespread population of bacteria with inducible capacity to metabolize hydrocarbons is indicated. Observed turnover times for toluene were 0.2–40 years with growth rates of 10−6 h−1 from toluene at 1 µg liter−1.
Mechanisms of hydrogen ion neutralization in an experimentally acidified lake
Authors: Cook R. B. , Kelly C.A. , Schindler D.W. , Turner M. A.
Published: April 2010

The experimental acidification of Lake 223 (Experimental Lakes Area, northwestern Ontario) with sulfuric acid in 1976–1983 allowed a detailed examination of the capacity of the lake to neutralize hydrogen ion. A whole‐lake alkalinity and ion budget for Lake 223 showed that 66– 81% of the added sulfuric acid was neutralized by alkalinity production in the lake. Nearly 85% of in situ alkalinity production was accounted for by net loss of sulfate through bacterial sulfate reduction, coupled with iron reduction and iron sulfide formation, in littoral sediments (60%) and in the hypolimnion (25%). Exchange of hydrogen ion for calcium and manganese in the sediments accounted for 19% of the alkalinity generated, while other cations were net sinks for alkalinity. Alkalinity input from the watershed of Lake 223 was very small, averaging about 5% of that produced in the lake.

The seasonal production of 1,000 µeq liter−1 alkalinity in the anoxic hypolimnion of this softwater lake could be attributed to bacterial sulfate reduction coupled with iron sulfide formation, ammonium production, and iron (II) production. Only the alkalinity produced from bacterial sulfate reduction coupled with iron sulfide formation remained throughout the annual cycle.
Cladoceran filtering rate: body length relationships for bacterial and large algal particles
Authors: Knoechel Roy , Holtby L. Blair
Published: April 2010

In situ filtering rates were determined for six cladocerans and one calanoid fed either 1‐µm bacteria or 20‐µm algae. Food‐specific regressions of filtering rate vs. body length for all cladocerans together produced explained variances of 87 and 95% while a combined regression for both food particles plus 6‐µm yeast produced an explained variance of 87%. All animals could filter particles of all sizes but were most efficient at filtering the medium‐sized food. Large animals maintained a higher filtering efficiency on large algal particles than on small bacteria, while small animals did the opposite, providing some basis for niche differentiation. The regression equations permit the indirect estimation of grazing impact on bacterioplankton and phytoplankton populations and should facilitate studies of energy flow and plankton population dynamics in lakes.
A method for obtaining in situ growth rates of larval Chironomidae (Diptera) and its application to studies of secondary production1
Authors: Huryn Alexander D. , Wallace J. Bruce
Published: April 2010

Methods and growth chambers are described which permit in situ estimates of the growth rates of chironomid larvae inhabiting litter accumulations in lotic habitats. Instantaneous growth rates (IGRs) for larvae of different sizes ranged from 0.01 to 0.24 mg mg−1 ash‐free dry mass (AFDM) d−1 at stream temperatures of 2.9°– 15.1°C. IGRs were significantly and linearly related to temperature. Regression equations relating IGRs and temperature, combined with field‐derived data for chironomid standing stock and stream temperature, enabled calculation of the production of chironomids inhabiting litter accumulations (15‐g DM litter bags) in a temperate mountain stream. The annual production per litter bag was about 224 mg AFDM yr−1 and the annual P:B was 42, indicating rapid turnover of chironomid biomass. The annual production of chironomids exceeded the mean standing crop biomass of all macroinvertebrates by 4.6 ×.
Isolation of symbiotic dinoflagellates by centrifugal elutriation1
Authors: Bird A. E. , Quinn R. J.
Published: April 2010

Centrifugal elutriation, a method combining centripetal liquid flow with centrifugal force, has been used to isolate symbiotic dinoflagellates from a cnidarian host. The elutriated cells were shown to be viable by photosynthetic incorporation of 14CO2 and low release of photosynthetic products into the incubation medium. The level of contamination by clinging debris was low and by host solids was negligible.
Predation on rotifers by the suspension‐feeding calanoid copepod Diaptomus pallidus1
Authors: Williamson Craig E. , Butler Nancy M.
Published: April 2010

Predation on rotifers by the small suspension‐feeding calanoid copepod Diaptomus pallidus was examined in order to quantify the effects of prey density, prey type, and the presence of algal food resources on ingestion rates, and to determine whether ingested rotifer biomass could be utilized to enhance the survival and reproduction of the copepods. Clearance and ingestion rates of D. pallidus on rotifers were 5.5–6.2 times greater than on algae presented at the same concentration and similar to the maximum rates previously reported for more carnivorous cyclopoid copepods preying on rotifers. The survival and reproduction of D. pallidus were substantially enhanced by the addition of rotifers to a threshold algal diet. When presented with a natural assemblage of plankton, D. pallidus preferentially ingested certain rotifer species over others. Predation on rotifers by such diaptomids may form an important trophic link in freshwater planktonic food webs.
Relationships between chlorophyll and ocean color constituents as they affect remote‐sensing reflectance models1
Authors: Carder K. L. , Steward R. G. , Paul J. H. , Vargo G. A.
Published: April 2010

Good agreement between satellite‐derived and shipboard measurements of chlorophyll a + pheophytin a concentrations results from the covariance of each of the nonwater color constituents of the ocean with pigment concentration. The specific absorption coefficient at 440 nm varies directly with the submicron chlorophyll fraction, which itself varies inversely with total chlorophyll concentration. Both the backscattering coefficient for particles and the Gelbstoff absorption coefficient increase with chlorophyll pigments. An analytical remote‐sensing reflectance model for chlorophyll concentrations in the eastern Gulf of Mexico is developed from these relationships and tested against an independent data set. By this approach, remote‐sensing algorithms can be developed that respond to regional and seasonal differences in runoff (e.g. terrigenous Gelbstoff and detritus), phytoplankton size, and pigment color groups.
In situ particle generation in a southern Swedish stream1
Authors: Petersen Robert C.
Published: April 2010

An increase in the number of particles was measured below a waterfall in a southern Swedish stream. POC increased below the falls by 0.12 mg C liter−1, 5% of the total POC present. DOC decreased by 0.1 mg C liter−1 but was not significant and inorganic content remained unchanged. The number of Celloscope‐measured particles in the size range of 2–20 µm increased below the falls, with a 66% increase in particles of 4–6‐µm diameter. Although POC generation was small it was greater than published allochthonous input rates to streams. Abiotic particle generation, although extremely difficult to measure, may be far more important to carbon dynamics in stream ecosystems than previously thought.
Oxygen budget of a perennially ice‐covered Antarctic lake1
Authors: Wharton Robert A. , McKay Christopher P. , Simmons George M. , Parker Bruce C.
Published: April 2010

A bulk O2 budget for Lake Hoare, Antarctica, is presented. Five years of seasonal data show the lake to be persistently supersaturated with O2. Oxygen is carried into the lake in glacial meltstreams and is left behind when this water is removed as ice by ablation and sublimation. A diffusive loss of O2 from the lake through the summer moat is suggested. Measured values of the total O2 in the water column indicate that the time scale of O2 turnover is much longer than a year. Based on these results we suggest that the amount of O2 in the water does not change significantly throughout the year and that the lake is also supersaturated with N2.
Fish‐flamingo‐plankton interactions in the Peruvian Andes1
Authors: Hurlbert Stuart H. , Loayza Washington , Moreno Tomas
Published: April 2010

The zooplankton and flamingo populations of 20 high elevation (3,700–4,700 m) lakes in the Andes of southern Peru were assessed on one to three occasions each. Some of these lakes have cyprinodont fish (Orestias spp.), others do not. Lakes with fish usually have a sparse zooplankton dominated by cyclopoid copepods and chydorid cladocerans; the others tend to have an abundant zooplankton dominated by calanoid copepods and daphnids or by Artemia. Chilean flamingos (Phoenicopterus chilensis) are usually absent or scarce on lakes with fish and present in large numbers where fish are absent. We suggest that the distribution of this flamingo in the Central Andes, and in South America generally, is determined primarily by the distribution of fish, with which it competes for invertebrate prey. The patterns above are complicated by the impact on Orestias populations of man, of fish‐eating birds, and of introduced, non‐native fish (Salmo gairdneri, Basilichthys bonariensis).
Phytoplankton control by grazing zooplankton: A study on the spring clear‐water phase1
Authors: Lampert Winfried , Fleckner Walter , Rai Hakumat , Taylor Barbara E.
Published: April 2010

We tested the hypothesis that a clear‐water period, regularly observed in many meso‐ and eutrophic lakes, is caused by grazing herbivorous zooplankton. Such a clear‐water phase occurs during mid‐May in the moderately eutrophic Schöhsee and involves a rapid increase in Secchi transparency, and a drop in chlorophyll and particulate organic carbon in size fractions <35 µm. Maxima of zooplankton biomass and community grazing rates (170% of volume cleared per day) coincided with the greatest transparency. The algal decline was not related to nutrient depletion or climatic events. Before the clear‐water phase small phytoplankton contributed up to 88% of the primary production, but the contribution of large particles was more important after the zooplankton maximum. The effects of herbivory by zooplankton were examined in a series of time‐overlapping enclosure experiments. Concentrations of small (<35 µm) particles were always higher in the bags lacking zooplankton than in the controls. A mass development of small algae occurred in the zooplankton‐free bags initiated during the clear‐water phase, although the presence of zooplankton stimulated the growth of large (>35 µm) algae.
Properties of the seawater‐air interface. 3. The electrification and energy transfer through surface films1,2
Authors: Dragčević Dj. , Pravdić V.
Published: April 2010

Surface tension and contactless surface potential were measured simultaneously in model systems and in samples of original seawater films from the northern Adriatic area. The films were brought into a steady state in a Langmuir trough, and the electric and nonelectric components of the total energy transferred through the film were determined from hysteresis curves of surface potential vs. area of film and of curves of surface tension vs. area. The films studied were negatively charged, but the direction of energy transfer depended on the concentration of the film‐forming material and on the rate of perturbation. At low concentrations the electrical component of interfacial energy transfer is predominant, at higher concentrations the nonelectric predominates. The description of the phenomenology of film behavior indicates that the enrichment of elements in the microlayer could be influenced by the concentration of film‐forming material and by rates of perturbation of the microlayer by mechanical forces.
The carbon cycle for Lake Washington—A stable isotope study1
Authors: Quay P. D. , Emerson S. R. , Quay B. M. , Devol A. H.
Published: April 2010

We investigate the carbon cycle in Lake Washington for the year 1980 using monthly measurements of the dissolved inorganic carbon (DIC) and its 13C : 12C isotopic composition. Mass balances of DIC and 13C : 12C yield estimates of CO2 gas exchange rates and net organic carbon production rates. Between 24 June and 13 August, the calculated CO2 gas invasion rate of 0.80 × 106 mol C d−1 is nearly equal to the river DIC inflow rate. The calculated epilimnetic net organic carbon production rate is 0.68 × 106 mol C d−1, about 20–30% of primary productivity estimated from 14C‐fixation experiments and ETS‐derived respiration rates. Metalimnetic and hypolimnetic DIC increase rates and porewater DIC gradients in hypolimnetic sediments indicate that remineralization of particulate organic carbon (POC) previously deposited in the sediments is a major (0.5 × 106 mol C d−1) DIC source to the lake during summer.

For the whole year, summertime CO2 gas invasion balances wintertime CO2 gas evasion and DIC and POC outflow balance DIC and POC inflow rates, implying no net carbon burial in the sediments during 1980. This contrasts with the measured long term sedimentation‐rate‐derived carbon burial rate of 0.8 × 106 mol C d−1. Year‐to‐year variability in summertime primary production rates largely determines net gains or losses of carbon via CO2 gas exchange and sedimentation.
Long range vertical migration of Volvox in tropical Lake Cahora Bassa (Mozambique)
Authors: Sommer Ulrich , Maciej Gliwicz Z.
Published: April 2010

Volvox sp. performed diel vertical migrations in Lake Cahora Bassa, the amplitude of which greatly exceeded those reported for other species of freshwater algae. Migration velocities even exceeded the maxima attained by marine dinoflagellates. The daytime depth distribution is attributed to the light regime and the nighttime depth distribution to phosphorus uptake in deeper water layers.
Comparison of mechanisms enhancing biodegradability of refractory lake water constituents1
Authors: Geller Annette
Published: April 2010

Bacterial degradation of macromolecular DOM, aged under weakly photolytic conditions (daylight > 300 nm), was compared to that of the original compounds before and after provision of a cosubstrate. Bacteria, Pseudomonas sp., Flavobacterium sp., and Erwinia sp., and macromolecules (apparent mol wt ≥ 1,500) were isolated from the same lake water samples, one taken in winter and one in summer. Decomposition was determined by DOC measurements, since UV absorbance A200–300nm did not give an accurate indication of loss rates. Both aging and the pulse dose of nutrients enhanced the accessibility of the refractory DOM to Pseudomonas sp. and Erwinia sp., while Flavobacterium sp. utilized the original substances most effectively. The original macromolecules were decomposed 12–22%, aging increased the available portions by a further 5–10%, and provision of the cosubstrate, glutamic acid, enhanced degradation by 3–8% and by 20% (Erwinia sp. and DOM fraction, both isolated in summer). The constituents of the macromolecules in the winter sample rendered accessible by photolysis were energetically advantageous to Pseudomonas sp. and Erwinia sp. The degradable portions of the original and aged macromolecules were consumed within the first week of incubation, and the remainder was persistent. Provision of a nutrient pulse did not result in the production of enzymes that might have enabled the bacteria to assimilate the refractory remainder. Both mechanisms are thought to reduce the longevity of the refractory DOM in a stepwise manner in natural waters.
Sediment stability around animal tubes: The roles of hydrodynamic processes and biotic activity1
Authors: Luckenbach2 Mark W.
Published: April 2010

Experiments on the entrainment of surface sediments around polychaete tubes at natural and manipulated densities were conducted in a recirculating seawater flume. Intact cores with either 0 or 8 Diopatra cuprea tubes per 0.01 m2 plus associated assemblages were collected in the field. Sediments which contained D. cuprea tubes had natural macrofaunal densities >5 x those of sediments without tubes. To distinguish between organism‐induced sediment effects and the hydrodynamic effects of tubes on the critical entrainment velocities of these sediments I used cores with eight tubes per 0.01 m2 (tubes and high macrofaunal density), similar cores with tubes removed (no tubes and high macrofaunal density), cores with eight tubes added (tubes and low macrofaunal density), and cores without tubes (no tubes and low macrofaunal density). Critical entrainment velocities for natural cohesive sediments in these treatments were 46% lower in the cores with high densities of macrofauna than in those with low densities. The implication is that biotically mediated sedimentological changes around D. cuprea tubes, rather than alterations of near‐bed flow by the tubes, are responsible for lowering erosion thresholds in this system.
The pH of estuarine waters
Authors: Millero Frank J.
Published: April 2010

The emf measurements for the TRIS buffer in seawater have been used to define buffer solutions that can be used to determine the pH on a free or total proton scale for estuarine waters. The pH is related to the stoichiometric dissociation constant (K*) of TRISH, the concentration of buffer (mTRIS) and salinity (S) by
urn:x-wiley:00243590:media:lno19863140839:lno19863140839-math-0001
where a = −9.73 × 10−5 and b = 6.988 × 10−5. The values of pK* were fit to equations of the form
urn:x-wiley:00243590:media:lno19863140839:lno19863140839-math-0002
where A, B, and C are functions of salinity and T is the absolute temperature.

An electrode system with liquid junction was used to measure these buffers to compare the various pH scales.
Phytoplankton pigment patterns in the California Current as determined by satellite1
Authors: Peláez José , McGowan John A.
Published: April 2010

The satellite images of phytoplankton pigments off California show a high degree of heterogeneity. However, recurrent phytoplankton pigment structures can be identified in the California Current. The major ones are: two sharp boundaries several hundreds of kilometers long; low pigment eddies far offshore interwoven with higher pigment structures immediately inshore; a low pigment intrusion in the Southern California Bight, and a higher pigment region farther offshore; eddies “attached” to shallow coastal areas; and California Current rings spawned far offshore.

The larger scale structures of phytoplankton pigments show a remarkable continuity throughout a year, but there is shifting, wobbling, and erosion of these structures. The structures are strong and distinct in spring and summer, weaken through fall (except for a slight intensification in October), and become weakest and poorly defined in late fall‐early winter. The patterns of distribution of phytoplankton pigments for a given season tend to reappear from one year to another in the 3 years analyzed. Such recurrency is significant because these patterns may change, and some disappear, within any given year.

Clear similarities of the phytoplankton pigment distributions to the field of dynamic height and to an infrared image of sea surface temperature indicate the very important role of ocean circulation, and of phytoplankton nutrient content of the waters, in the generation and maintenance of the observed patterns.
Multivariate statistics applied to phytoplankton data from two Gulf Stream warm core rings1
Authors: Gould, Jr. R. W. , Balmori E. R. , Fryxell G. A.
Published: April 2010

Multivariate statistical techniques were used on data from two cruises to Gulf Stream warm core rings to reveal patterns and relationships between phytoplankton species abundance and environmental parameters. Principal component analysis (PCA) was performed on each cruise separately and on the combined data to help delineate groups of stations, depths, and species. A ring center station with high numbers of diatoms and a Slope Water station formed separate groups. Deep samples from all the stations grouped together. We consistently observed strong similarities in phytoplankton abundance and species composition between fall samples from the two rings. Inverse analysis was performed using presence or absence data, and the values of the first three principal components were then used in a cluster analysis to determine species co‐occurrences. This analysis resulted in separate groupings of a large number of diatom species found at the center of the rings, of deep species, and of the most abundant and the most frequently observed taxa.

Simple correlations, multiple regressions, and canonical correlations were performed with the phytoplankton log abundance data and the environmental data. The canonical coefficients and correlations suggest that high numbers of dinoflagellates and other algae are associated with lower salinity in the Slope Water and at the ring edge, and that higher temperatures and low values of silica (dissolved) are reflected in higher numbers of diatoms and coccolithophorids at ring center.
Predator‐prey interactions of nanozooplankton and bacteria in an oligotrophic marine environment1
Authors: Rassoulzadegan F. , Sheldon R. W.
Published: April 2010

Population interactions between nanoplankton and bacteria were investigated by means of long (ca. 5 day) incubations of prescreened seawater samples. Evidence is presented to show that population development is controlled by the predation of larger organisms on smaller ones. The development of the bacterial populations seems to be totally controlled by predation by nano‐sized organisms (flagellates and ciliates) and by picoflagellates. It is possible, though less certain, that picoflagellate development is controlled by nanociliate predation.
Hypothesized resource relationships among African planktonic diatoms
Authors: Kilham Peter , Kilham Susan S. , Hecky Robert E.
Published: April 2010

Several hypotheses are advanced for resource relationships among planktonic diatoms in African freshwater lakes that are consistent with the light and nutrient conditions of the lakes and the extant and fossil distributions of the diatom species in them. The hypotheses are all testable and are potentially powerful tools for interpreting past climatic conditions. A ranking is proposed along a Si: P gradient: at the high end are the planktonic Synedra spp. with the highest Si requirements and lowest P requirements (high Si : P), the planktonic Nitzschia spp. are intermediate, and the Stephanodiscus spp. are at the low end with the lowest Si requirements and highest P requirements (low Si : P). Melosira species may be ranked along a light: P gradient. We suggest that Melosira distans and Melosira ambigua grow under high light and have low P requirements, Melosira agassizii and Melosira granulata are intermediate, and Melosira nyassensis has the lowest light and highest P requirements. There also appears to be a relationship between pore size and the light regime for growth among the Melosira species; thus, M. distans and M. ambigua have the smallest pores and highest light requirements, M. nyassensis has the largest pores and lowest light requirements. Melosira granulata is intermediate and seems to be very variable in pore size, depending on the light environment. One diatom, Nitzschia fonticola, lives in and on colonies of Microcystis and is considered to be an obligate nitrogen heterotroph.
Wind‐induced internal seiches in Lake Zurich observed and modeled1
Authors: Horn W. , Mortimer C.H. , Schwab D.J.
Published: April 2010

During August and September 1978, 31 current meters and 120 temperature sensors were deployed to record every 10 or 20 min at various depths at 12 moorings (with wind speed and direction at three moorings) in Lake Zurich. We explore here the baroclinic (internal seiche) response to wind impulses, observed as fluctuations in isotherm depth and current speeds. Those fluctuations and their energy spectra are compared with the predictions of two models fitted to basin topography and to the observed average thermal structure: a two‐layered variable‐depth (TVD) model developed by D. J. Schwab, fitted to basin topography and incorporating a two‐dimensional horizontal grid, and C. H. Mortimer’s two‐layered modification of a simpler procedure originally developed for surface seiche calculations by A. Defant.

The dominant responses to wind impulses were internal seiches of the first longitudinal mode (average period 44 h). Weaker signals from the second (24 h) and third (17 h) modes were also seen in spectra of temperature and current fluctuations. The models displayed patterns of thermocline displacement and current which, in periodicity and structure, were closely similar to those observed. Predictions of the Defant model were less precise, particularly for current.

Founded on linear theory and neglecting the effects of rotation, the models were unable to reproduce two features occasionally seen in the lake motions: clockwise or anticlockwise rotation of current direction; and internal surges arising when storms induced large‐amplitude downstrokes of the thermocline at one basin end or the other. The lake’s internal response was principally dependent on the timing, strength, and duration of the wind impulse, relative to and interacting with internal seiche motions already in progress.
Currents in Lake Geneva1
Authors: Bohle‐Carbonell M.
Published: April 2010

The first synoptic measurements of currents and temperatures in Lake Geneva and the wind field on its shoreline have been analyzed to derive mean characteristics of the internal motions. The observations cover the periods from October to March of 1981/1982, 1982/1983, and 1983/ 1984.

The lake responds to a very inhomogeneous diurnal and gradient wind field with high‐energy, statistically nonstationary fluctuating currents superimposed on a weak mean state. Current fluctuations of periods between 24 and 12 h appear to propagate cyclonically. Clockwise‐turning current vectors, mainly at near‐inertial frequencies, and a tendency to high energy at low frequencies at nearshore locations are found. Only a portion of the observed details can be explained by features of gravity waves modified by rotation.
Phosphorus transfer from sediments by Myriophyllum spicatum1
Authors: Smith Craig S. , Adams Michael S.
Published: April 2010

The uptake of phosphorus, the biomass, and the standing P stock were measured over the course of a year in roots and shoots of the Eurasian watermilfoil, Myriophyllum spicatum, from Lake Wingra, Wisconsin. The resulting data were used to estimate the relative contributions of root and shoot uptake to the phosphorus economy of the plant and to examine the role of the plant in moving phosphorus between sediment and water.

The total yearly uptake of P by a square meter of Myriophyllum was 3.0 g P m−2. Root uptake accounted for 2.2 g, shoot uptake only 0.8 g. The rate of P release from healthy shoots was insignificant, but about 2.8 g P m−2 yr−1 was lost due to shoot turnover.

Since most of the P uptake is by the roots and much of the plant P is transferred to and lost by the shoots, Myriophyllum is a potentially important vector in the movement of P from the sediments to the water. The net transfer of P from the sediments to shoots of Myriophyllum in Lake Wingra is about 2.0 g P m−2 yr−1. Release of this P during decay makes Myriophyllum an important source of P for pelagic phytoplankton and can explain much of the previously reported P export from the littoral zone of Lake Wingra.
Comparison of methods for measuring production by the submersed macrophyte, Potamogeton perfoliatus L.1,2
Authors: Kemp W. Michael , Lewis Marlon R. , Jones Thomas W.
Published: April 2010

Six conventional methods for measuring primary production of submersed vascular plants were compared to test for previously suggested inherent shortcomings in the O2‐exchange techniques. Production was measured for experimental populations of Potamogeton perfoliatus L., from upper Chesapeake Bay in five comparative studies, each including an O2‐exchange method. All techniques tested (14C incorporation and O2 evolution for both bottle incubations and undisturbed populations; biomass accumulation and inorganic carbon consumption for intact populations) compared favorably, with mean (molar) ratios of oxygen to carbon production ranging from 0.9 to 1.6. In addition, direct measurements indicated that rhizosphere release of O2 would introduce only small errors (<5%) in O2 production estimates. Although changes in lacunal storage of O2 can result in brief (5–25 min) delays between O2 production and evolution to the external water, simple methodological precautions can overcome such problems. We conclude that all available methods for measuring productivity of this and related species are potentially useful, each having its particular strengths and weaknesses, and the use of more than one method is recommended.
A simple fiber‐optic microprobe for high resolution light measurements: Application in marine sediment1
Authors: Jergensen Bo Barker , Des Marais David J.
Published: April 2010

A fiber‐optic microprobe is described which is inexpensive and simple to build and use. It consists of an 80‐µm optical fiber which at the end is tapered down to a rounded sensing tip of 20–30‐µm diameter. The detector is a hybrid photodiode/amplifier. The probe has a sensitivity of 0.01 µEinst m−2 s−1 and a spectral range of 300–1,100 nm. Spectral light gradients were measured in fine‐grained San Francisco Bay sediment that had an undisturbed diatom coating on the surface. The photic zone of the mud was only 0.4 mm deep. Measured in situ spectra showed extinction maxima at 430–520, 620–630, 670, and 825–850 nm due to absorption by chlorophyll a, carotenoids, phycocyanin, and bacterio‐chlorophyll a. Maximum light penetration in the visible range was found in both the violet and the red at ≤400 and ≥700 nm.
The theory of secondary production calculations for continuously reproducing populations
Authors: Kimmerer W. J.
Published: April 2010

Definitions and mathematical expressions currently used to calculate secondary production are based on the observation of development in cohorts. Most populations of marine zooplankton and many benthic populations do not meet the strict conditions necessary for measurement of growth and mortality in cohorts, and application of the mathematics used in cohort methods to such populations can lead to errors. A better approach is to assume approximate steady state and to determine integrated production (IP) over a time period from observations of the instantaneous production rate, PR.

The determination of IP consists of two steps: measurement of PR, usually by a direct method, and integration. The value of IP determined from PR over a given time interval depends on assumptions about the trajectory of PR between samples. I use several simple models to demonstrate that mortality need not be measured and that IP can be determined from sample data on PR. The best estimate of IP is a simple sum of PR values multiplied by appropriate time intervals.
Predator‐prey interactions between omnivorous diaptomid copepods and rotifers: The role of prey morphology and behavior1
Authors: Williamson Craig E.
Published: April 2010

Suspension‐feeding diaptomid copepods feed selectively on several rotifer species. Predator‐prey interactions between Diaptomus pallidus and seven species of rotifers were quantified and behavioral probabilities computed. Prey size was a good predictor of the probability of Diaptomus avoiding a prey following an encounter but had little or no predictive value in subsequent levels of interaction (capture, ingestion). Three of the rotifers exhibited escape responses which were specifically based on rheotaxis, suggesting they may have evolved primarily in response to selection pressures exerted by suspension‐feeding zooplankton. Other prey defense mechanisms included a tough integument and long spines—defense mechanisms often used by crustacean prey in response to large predatory calanoids.
Sestonic bacteria as a food source for filtering invertebrates in two southeastern blackwater rivers1
Authors: Edwards R. T.
Published: April 2010

Bacterial cell concentrations and biomass within seven size classes of seston in the Ogeechee River and Black Creek, two blackwater rivers in southeastern Georgia, were measured for 19 months. The proportion of sestonic carbon in bacteria was determined to assess the relative food. quality of the various fractions for filtering invertebrates. Cell concentrations were unusually high in both rivers, with values ranging from 2.03 × 109 to 1.10 × 1011 total cells liter−1 with a mean of 1.48 × 1010. Concentrations of attached cells varied from 1.20 × 108 to 1.70 × 109 cells liter−1. Most cells were small, coccoid forms not attached to particles. Mean mass per cell in the Ogeechee River was 1.86 × 10−14 g C and in Black Creek 8.28 × 10−15. Total bacterial biomass was also high, ranging from 19.1 to 1,105.0 mg C m−3. Most of the bacterial biomass was in the particle size range from 0.30 to 12 µm. The bacterial carbon composition of the seston was <1% in both rivers for all seston > 12 µm. Percentages in the < 12‐µm fraction were much higher, ranging from 1.4 to 28.9% in Black Creek and 15.5 to 99.9% in the Ogeechee River. Cell concentrations and biomass varied with river discharge and were higher during periods of floodplain inundation. The high bacterial content of the smallest fraction of seston may be an important food source for filter‐feeding invertebrates such as blackflies and chironomids, which are abundant in these rivers.
The role of gas exchange in the inorganic carbon, oxygen, and 222Rn budgets of the Amazon River1
Authors: Devol Allan H. , Quay Paul D. , Richey Jeffrey E. , Martinelli Luiz A.
Published: April 2010

Dissolved oxygen, 222Rn, pCO2, alkalinity, respiration rate, and discharge have been measured at eight mainstem and seven tributary stations during February–March 1984 in a 1,700‐km stretch of the Amazon River between Vargem Grande and Obidos in Brazil. Air–water gas exchange rates were estimated two ways: measurements of the flux of 222Rn into floating domes yielded an average boundary layer thickness of 78 µm, and oxygen mass balance calculations resulted in an average of 38 µm. Given a boundary layer thickness on the order of 50 µm, CO2 loss to the atmosphere in the entire reach would have been 37.4 kmol s−1, which is about equal to the total tributary dissolved inorganic carbon (DIC) input (43 kmol s−1) and is about half of the total fluvial DIC input to the section (97.7 kmol s−1). Thus, CO2 evasion is a major component of Amazon River DIC balance. Because gas exchange within the section was rapid relative to water travel time through the section, a quasi‐steady state was maintained between respiratory input and evasion of CO2. Dissolved 222Rn activities in the mainstem varied from 3.5 to 8.3 dpm liter−1 and were always highly supersaturated with respect to the atmosphere. Dissolved radon was also not supported by decay of 226Ra (0.59–0.70 dpm liter−1) in the mainstem. A 222Rn mass balance indicated that direct groundwater input into this stretch of the Amazon mainstem probably accounted for no more than 1% of water discharge.
On the ecology of a Cryptomonas phaseolus population forming a metalimnetic bloom in Lake Cisó, Spain: Annual distribution and loss factors1
Authors: Pedrós‐Alió Carlos , Gasol Josep M. , Guerrero Ricardo
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Sedimentation and bioturbation in a salt marsh as revealed by 210Pb, 137Cs, and 7Be studies12
Authors: Sharma P. , Gardner L. R. , Moore W. S. , Bollinger M. S.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Absorption of light by yellow substance in freshwater lakes
Authors: Davies‐Colley R. J. , Vant W. N.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Rates of phosphate uptake by coral reef flat communities1
Authors: Atkinson M. J.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Estimating periphyton growth parameters using simple models1
Authors: Rodriguez Marco A.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Extraction with DMSO to simultaneously measure periphyton photosynthesis, chlorophyll, and ATP1,2
Authors: Palumbo Anthony V. , Mulholland Patrick J. , Elwood J. W.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
On fluorometric determinations of filter‐retained pigments1
Authors: Venrick Elizabeth L.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Limitation of N2 fixation in coastal marine waters: Relative importance of molybdenum, iron, phosphorus, and organic matter availability1
Authors: Paerl Hans W. , Crocker Kenneth M. , Prufert Leslie E.
Published: April 2010

Phytoplankton growth in many coastal and pelagic marine waters is chronically limited by nitrogen availability. Such conditions potentially favor the establishment of N2‐fixing microorganisms (eubacteria and cyanobacteria). However, planktonic and benthic N2 fixation is often either absent or present at ecologically insignificant rates. It has been proposed that deficiencies in inorganic nutrient (specifically molybdenum) availability could help explain this paradox. We examined both inorganic and organic nutrient limitations of marine N2 fixation in nitrogen‐deficient coastal North Carolina waters. Inorganic nutrient (phosphorus, iron, and molybdenum) availability consistently exceeded demands by N, fixers. In contrast, enrichment with the sugars fructose, glucose, sucrose, and maltose and the sugar alcohol mannitol either elicited N2 fixation or enhanced existing rates of N2 fixation. Supplementation with particles (organic detritus) also enhanced N2 fixation potentials; the combined addition of particles and organic compounds yielded maximum rates of N2 fixation. This combination promotes the development of O2‐reduced microenvironments (microzones) in which N2 fixers can reside. A functional explanation for the observed stimulation of N2 fixation is that it is an anaerobic process which, in aerobic marine waters, can only proceed in O2‐poor microzones. Hence, deficiencies in organic matter rather than inorganic nutrient availability may play key roles in limiting and regulating marine N2 fixation.
Measurement of free cupric ion concentration in seawater by a ligand competition technique involving copper sorption onto C18 SEP‐PAK cartridges1
Authors: Sunda William G. , Hanson Alfred K.
Published: April 2010

Knowledge of ion speciation and free ion concentrations is important in predicting the biological availability and geochemical behavior of trace metals. Here we describe a new technique for measuring free cupric ion concentration in seawater based on sorption of copper onto SEP‐PAK C18 cartridges and internal free cupric ion calibration. Calibration was achieved by adding cupric ion buffers, consisting of copper and excess concentrations of synthetic chelator, ethylenediaminetetraacetic acid (EDTA). EDTA competes with natural organic ligands for copper complexation, but its copper chelate is not retained by the C18 cartridges. This latter property allows EDTA to be used for free cupric ion calibration.

Titrations in seawater utilizing the new technique revealed that copper was highly complexed. Free cupric ion concentrations in three samples of seawater from lower Narragansett Bay, Rhode Island, and one from off the coast of Peru were measured to be 10−12.3, 10−12.0, 10 12.1, and 10−11.5 M at total dissolved copper concentrations of 26.7, 16.5, 19.4, and 3.7 nM. From these values and from computed and experimental values for inorganic complexation, we compute that only 0.03–2% of the dissolved copper can be accounted for as inorganic species (Cu2+, CuCO3, CuOH +, etc.). The remainder, 99.97–98%, appears to be organically complexed. These results are in general agreement with several other recent studies, using several techniques, of copper complexation in seawater.