bluuebunny/crossref_metadata_2025 huggingface dataset:
Concentration of Serratia in the surface microlayer1
Authors: Syzdek Lawrence D.
Published: March 2010

Concentrations of Serratia marcescens and Serratia marinorubra were measured in the surface microlayer by a floating Nuclepore filter technique. Controlled removal of the filters permitted comparisons of bacterial concentrations in various thicknesses of the microlayer from 8 to 100 µm. Serratia became enriched in the microlayer by a factor >4 during the process of preparing suspensions by dilution and vortex mixing. Enriched concentrations were found only in the upper 20 µm and reached enrichment factors >15 within 1 h, but EF values >120 were obtained from the upper 10 µm of suspensions aged undisturbed for 18 h. Rates of increase of EF were greater for uncleaned water surfaces than for cleaned surfaces, indicating a relationship between microlayer concentration and surface films.
Genetic variability and spatial patterns of genetic differentiation in the reproductive rates of the marine coccolithophores Emiliania huxleyi and Gephyrocapsa oceanica1,2
Authors: Brand Larry E.
Published: March 2010

The acclimated reproductive rates of 73 clones of Emiliania huxleyi and 19 clones of Gephyrocapsa oceanica were measured. Statistically significant genetic variability in reproductive rates was found among clones from single water bottles in both species. Genetic differentiation was found between populations from different water masses, but not within water masses. The spatial patterns of genetic differentiation appear to be different in the two species.
The effect of temperature and density on the amplitude of vertical migration of Daphnia magna
Authors: Calaban M. J. , Makarewicz J. C.
Published: March 2010

The amplitude of vertical migration of Daphnia magna from warm to cold water was inhibited in thermally stratified columns in acrylic tubes. Changes in water density alone did not affect vertical movement. Abolition of the descending blue dance could not explain the results because the light source had a spectrum shifted to the red region. The magnitude of vertical migration may be reduced by an avoidance reaction to cold temperatures commonly observed in temperate lakes during summer stratification.
Daphnia in Lake Washington1
Authors: Edmondson W. T. , Litt Ami H.
Published: March 2010

In 1976 Daphnia, a genus that had been inconspicuous in the zooplankton of Lake Washington, suddenly became dominant. The mean summer transparency of the lake doubled. The major change affecting the success of Daphnia evidently was a decrease in the abundance of the predatory Neomysis mercedis in the mid‐1960s. Daphnia probably did not increase at that time because of the continued persistence of significant quantities of Oscillatoria until 1975. Eight species of Daphnia have been seen in the lake, but only three have become abundant. Daphnia pulicaria has been continuously present since its appearance in May 1976, although it becomes very scarce in winter. Daphnia galeata mendotae and Daphnia thorata have had much more limited occurrence. In each year from 1976 to 1980, two species formed separate population maxima, except in fall 1979 when D. thorata, although present, failed to increase. Instead, the plankton became dominated by the rotifer Conochilus hippocrepis which had been increasing for several years. In 1980 D. thorata and D. pulicaria made maxima, but in reverse order from earlier years. Several other species of zooplankton have been less abundant since the resurgence of Daphnia than during the period of eutrophication and recovery.
Reproductive cycle and fecundity of Euphausia pacifica in Puget Sound, Washington1
Authors: Ross Robin M. , Daly Kendra L. , English T. Saunders
Published: March 2010

The length and timing of the spawning season and the fecundity of Euphausia pacifica in northern Puget Sound, Washington, were investigated by analyzing preserved samples and by observing spawning of euphausiids in the laboratory. Gravid females (stage IV) and ripe females (spawning within 24 h) first appeared in mid‐April. Spawning of the overwintered females was most intense in April and May, but continued at a low level throughout most of June. No ripe females <19 mm were found after mid‐May. Larger females disappeared by the end of summer. Females born in April began to develop ovaries (stage I) in mid‐June, and although a few matured to stage IV and released eggs in late July‐early August, most of the population was stage II (with immature eggs in the ovaries) in the fall, overwintered as stage II, and began to mature again in late winter or early spring. The brood size, brood frequency, and length of the spawning season varied with female size. Small females released a maximum of 11–12 broods (≃1,000 eggs) over a 1‐month period from mid‐April to mid‐May. Over a 2‐month period large females released a maximum of 25–31 broods (≃3,700 eggs). A comparison of laboratory and field data suggested a method which may lead to accurate estimates of fecundity from preserved samples.
The density and composition of hypersaline waters of a Mexican lagoon1
Authors: Fernendez Hugo , Vazquez Felipe , Millero Frank J.
Published: March 2010

The composition of the major components (Na+, K+, Mg2+, Ca2+, Cl−, SO42−, Br) of a Mexican lagoon has been determined during evaporation (S = 44−186‰). Above a salinity of ≈90‰, the ratios of Ca:Cl and SO4:CI decreased, due to precipitation of CaSO4. The ratios of the other major constituents to CI were reasonably constant over the entire evaporation period. The initial Ca:Cl and HCO3:Cl ratios were lower than average seawater values, apparently due to precipitation of CaCO3. The densities of the lagoon waters were measured from 20° to 40°C and fit to an equation of the form (σ = 86 × 10−6 g·cm−3)

urn:x-wiley:00243590:media:lno19822720315:lno19822720315-math-0001

where d0 is the density of water and A, B, and C are temperature parameters. The densities of the lagoon waters calculated from the composition data by using apparent molal volume data were in reasonable agreement with the measured values (within 600 × 10−6 g·cm−3)
Cell division periodicity and the nitrate environment of a marine diatom
Authors: Yoder James A. , Martin James , Nill Andrew
Published: March 2010

Cell division periodicity of a marine diatom grown with a 12:12 light/dark cycle was influenced by the manner in which a limiting nutrient (nitrate) was supplied to the external environment of the cell. When nitrate was provided by changing the medium once a day, cell division was periodic, beginning after the nitrate concentration reached the apparent steady state level (about 12 h after the addition). When the same daily ration of nitrate was supplied at 2‐h intervals, periodicity was eliminated in <1 day, and cell division occurred continuously throughout the 24‐h period.
A fluid dynamics study of seawater flow through Gelidium nudifrons1
Authors: Anderson S. Miles , Charters A. C.
Published: March 2010

Gelidium nudifrons, growing in the subtidal region of semiexposed coasts has a thallus composed of rodlike branches which are closely spaced, but the structure is sufficiently open so that water flows freely through it. The turbulence of the water before and after passing through the plant was measured by hot‐film anemometry in a water tunnel in the laboratory and observed by a dye stream technique in the tunnel and in situ in the sea. The flow after passing through the plant was smooth at velocities up to a critical value, but turbulent for velocities above an abrupt transition. Turbulence in the flow entering the plant did not change this result.

Analysis of the results demonstrates that the plant strongly suppresses turbulence in the flow entering its thallus and at the same time generates microturbulence of its own at velocities above critical values varying from 6 to 12 cm·s−1, depending on the diameters and spatial density of the branches, due to the formation of systematic vorticity in the wakes of the individual branches. The transition in the flow induced by the branches of a marine plant is probably a phenomenon of considerable adaptive significance, because the turbulence generated by the plant itself or by neighboring plants may be the only turbulence in water motion past the plant that is of the right scale to enhance nutrient uptakes and effect the exchange of gases and solutes.
Phosphorus release by submerged macrophytes: Significance to epiphyton and phytoplankton1,1
Authors: Carignan R. , Kalff J.
Published: March 2010

The contribution of nine species of macrophytes to the phosphorus nutrition of their epiphytes and the rates of P release by Myriophyllum spicatum L. were measured in situ on fully labeled (32P) plants. The epiphytes derived only 3.4–9.0% of their P from the supporting macrophyte, indicating that previously suggested macrophyte‐epiphyte nutrient interactions are of relatively minor importance. Although high diurnal P release rates (x̄ = 3.24 µg·g‒1·h‒1) were observed for the Myriophyllum‐epiphyte complex, Myriophyllum accounted for only 9.9% (0.32 µg·g−1·h−1) of the total P released: The Myriophyllum‐derived P was, however, released in a highly available soluble form (minimum estimate: 60.3%). During the growing season, Myriophyllum thus appears to be principally important as a physical support for an active microbial community rather than as a P source to its epiphyton and surrounding waters.
Comparative photoheterotrophy, chemoheterotrophy, and photolithotrophy in a eutrophic reservoir and an oligotrophic lake1
Authors: Ellis Bonnie K. , Stanford Jack A.
Published: March 2010

Autoradiography was used to determine the role in the uptake of NaH14CO3 and [3H]glucose of specific microorganisms of two sizes (0.45–10 µm and 10–165 µm) in a eutrophic reservoir and an oligotrophic lake. Ultraplankton (0.45–10 µm) dominated plankton numbers and metabolic activity in both systems. An increase in photolithotrophy during the fall was due to an increase in the activity, numbers·ml−1, or both, of specific phytoplankters rather than an increase in the percentage of viable cells. Many of the most abundant species were not the most productive in terms of inorganic C fixation. Single species dominated total inorganic C fixation in both systems.

Light‐mediated uptake of [3H]glucose was extensive in Flathead Lake; light bottle uptake averaged 365% of dark bottle uptake. Autoradiographs indicated that bacteria were responsible for the observed light‐mediated uptake of [3H]glucose in both lakes. Chemoheterotrophy dominated all Lake Texoma samples. Simultaneous in situ NaH14CO3 and [3H]glucose incubations in Lake Texoma revealed an ability of Oscillatoria agardhii (Gomont) to be mixotrophic as well as photoheterotrophic.
Secondary benthic production in a tropical island stream
Authors: Bright Greg R.
Published: March 2010

Benthic samples were collected monthly during 1978–1979 at two sites in a tropical stream in Palau, Caroline Islands. Secondary production was measured by the size‐frequency method. At both sites, a riffle and an outcrop, the majority of matter and energy flowed through the decapod crustaceans, especially the shrimp Atya pilipes. Atya had a univoltine life cycle, possibly tuned to seasonal precipitation changes. The highest annual benthic production in this stream (7.70 g· m−2·yr−1 at the outcrop) did not differ greatly from production estimates in some temperate climate streams.
Total organic carbon in Lake Superior sediments: Comparisons with hemipelagic and pelagic marine environments1
Authors: Johnson Thomas C. , Evans James E. , Eisenreich Steven J.
Published: March 2010

Seventeen box cores from Lake Superior were analyzed for total organic carbon (TOC), porosity, and 210Pb activity. The data were used to determine relationships among bulk sedimentation rates, TOC sedimentation rates, and TOC degradation rates with depth in the core. Results are compared with predictive equations for TOC sedimentation rates and degradation rates in the oceans and show some striking similarities between the behavior of TOC in Lake Superior and in hemipelagic and pelagic marine environments.
Turbidity and its causes in a narrow glacial lake with winter ice cover1
Authors: Stewart Kenton M. , Martin Patricia J. H.
Published: March 2010

Results from a field investigation of seasonal variations in turbidity are presented for a narrow (≈12 × ≈1 km) glacial Finger Lake south of Rochester, N.Y. The turbidity structure is primarily vertical in summer and under winter ice cover; during spring and fall mixing horizontal gradients dominate. Inflows from the large drainage area at the southern end of the lake show a Coriolis influence. Vertical mixing of this inflow correlates well with density. During most of the year turbidity seems to be associated principally with suspended inorganic material.
Feeding selectivities and relative ingestion rates of Daphnia and Bosmina1
Authors: DeMott William R.
Published: March 2010

The feeding selectivities and feeding rates of Daphnia rosea and Bosmina longirostris were measured in mixtures of 4C‐labeled algae (Chlamydomonas reinhardi) and 3H‐labeled bacteria (Aerobacter aerogenes). Daphnia showed no preference for one over the other. Selectivity coefficients (algal clearance : bacterial clearance rate) for Bosmina ranged from 2.8 to 13.7 depending on both previous feeding history and the relative abundance of the two foods. At high concentrations of Chlamydomonas alone the ingestion rates of the two cladocerans per unit body weight were not significantly different, while at low food concentrations (500–10,000 cells ml−1) the relative ingestion rate of Bosmina was 4.8 to 1.6× higher than that of Daphnia. Differences in feeding behavior are attributed to interspecific differences in morphology and feeding mode. The ability of Bosmina to feed efficiently at low food concentrations and to feed selectively may invalidate inferences about zooplankton competition from theoretical models of optimal body size alone.
Transient situations in nitrate assimilation by marine diatoms. 2. Changes in nitrate and nitrite following a nitrate perturbation1
Authors: Colios Yves
Published: March 2010

Nitrate uptake and the excretion arid subsequent uptake of nitrite by nitrogen‐limited cells of Skeletonema costatun and Phaeodactylum tricornutum following the addition of nitrate were measured under low light intensity. Nitrate uptake kinetics in the light period were markedly different from those in the dark period. The influence of the previous nitrogen source on initial nitrate uptake rates was species‐ and light‐dependent. Nitrite excretion was related to external nitrate in a hyperbolic way. The relationship between nitrite uptake and external nitrate was not affected by light, but by temperature. When nitrate concentrations decreased below 1 µM, nitrite was taken up, except when a temperature change was imposed. These results are discussed in relation to the estimation of kinetic parameters of nitrate uptake and the origin of the primary nitrite maximum in oligotrophic oceanic areas.
Measurement of the metal complexing ability of exudates of marine macroalgae
Authors: Sueur S. , van den Berg C. M. G. , Riley J. P.
Published: March 2010

The metal complexing capacity of organic material‐released by three macroalgae was measured by the MnO2 exchange method. After 30 days of growth the concentration of metal complexing ligands released into the media, and their conditional stability constants (log K′) for complexes with copper, were: Ectocarpus siliculosus, 1.01 × 10−6 M, 10.15; Audouinella purpurea, 0.27 × 10−6 M, 9.95; Antithamnion spirographidis, 0.75 × 10−6 M, 9.77. Bioassay experiments with two planktonic microalgae in the presence of the released compounds were inconclusive and failed to confirm a free copper ion related response, The ecological effects of organic material released by macroalgae are probably not restricted to its chelating ability, but also arise from the toxicity of the material itself.
Metal contamination and its effect on primary production measurements1
Authors: Fitzwater Steve E. , Knauer George A. , Martin John H.
Published: March 2010

Minute amounts of trace elements can affect phytoplankton metabolic processes. Consequently, 14C primary productivity measurements may be adversely affected by contaminant metals inadvertently added during sampling and handling procedures. We analyzed various components used in the standard 14C method for metals; significant amounts of contaminants were found in many of the stock solutions used in this procedure and in associated containers. 14C uptake rates were lower under contaminated conditions than those with clean techniques. The latter are described in detail; their adoption is urged for more accurate and precise estimates of this fundamentally important process.
Electron flow via sulfate reduction and methanogenesis in the anaerobic hypolimnion of Lake Mendota1
Authors: Ingvorsen K. , Brock T. D.
Published: March 2010

The rate of dissimilatory sulfate reduction during summer stratification in Lake Mendota was estimated from sulfate and sulfide profiles. The electron flow via sulfate reduction in the anaerobic hypolimnion was about 25% of the electron flow via methanogenesis. There is a possible stoichiometric relationship between anaerobic electron flow and anaerobic carbon mineralization.
A microcalorimeter with a range of 0.1‐1.0 calories
Authors: Scott J. M. , Marlow J. A.
Published: March 2010

Details are given of the construction of a microcalorimeter which measures samples with calorific values in the range of 0.1–1.0 (0.4–4.0 J). A printed circuit board, with the copper surface forming one side of a thermocouple array, provided the basis for the instrument. The potential difference produced across the thermocouples from the combustion of a sample is amplified a hundredfold and fed into any laboratory chart recorder within the range of 10–100‐mV fullscale deflection. The operation and calibration procedures are described together with linearity and repeatability experiments. A regression coefficient of 0.997 was obtained for the former and a standard deviation of <±4% for repeatability.
Chesapeake Bay nutrient and plankton dynamics. 1. Bacterial biomass and production during spring tidal destratification in the York River, Virginia, estuary1,2
Authors: Ducklow Hugh W.
Published: March 2010

Bacterial abundance, biomass, and [3H]thymidine incorporation rates were studied during spring tidal destratification of the York River, Virginia, estuary. Monthly high spring tides cause salinity destratification in the moderately stratified estuary, which oscillates between stratified (top‐to‐bottom salinity difference >1‰) and vertically homogeneous (salinity difference <1‰) conditions on a time scale of 1–10 days. Bacterial abundance and carbon biomass ranged from 1 to 8 × 109 cells · liter’ and 20 to 100 µg C · liter−1. Thymidine incorporation into cold TCA‐insoluble fractions ranged from 1 to 10 × 10−9 mol · liter 1 · d−1; bacterial carbon production rates and specific growth rates were estimated at 7–75 µg C· liter−1 · d−1 and 0.2–1.1 · d−1. Biomass increased steadily during the destratification process while production remained constant. Production then increased twofold to threefold in 12 h during the period of maximum water‐column homogeneity. Increased vertical mixing and possibly stimulation of phytoplankton production are suggested as the major causes of this bacterial response to destratification.
Diel changes in numbers and activities of bacterioplankton in a reservoir in relation to algal production
Authors: Straskrabova Vera , Fuksa Josef
Published: March 2010

The changes in bacterial numbers, relative growth rates, and glucose uptake kinetics were studied in the surface layer of a reservoir during several 24‐h observation periods at intervals of 3 or 6 h, and once a day at intervals of 4 or 6 weeks from April through October. Microscopic and plate counts did not show any diel periodicity. All the other measures had regular diel patterns and the range of diel variation increased with increasing algal production. The diurnal average relative growth rates, Kt + Sn values, and turnover times were distinctly higher than the nocturnal ones and there were also characteristic diel changes in glucose uptake kinetics during the periods of algal activity. The diel changes in bacterial net uptake rate of algal extracellular products in autumn samples were twice as high as the maximum glucose uptake rate. Only for microscopic counts and maximum glucose net uptake rates were the diel variations significantly lower than the seasonal variation. For other parameters, the diel and seasonal variations were similar.
Production dynamics of some arctic Chironomus larvae
Authors: Butler Malcolm G.
Published: March 2010

Production and standing stock were determined for a two‐species population of Chironomus larvae in a tundra pond near Barrow, Alaska, from 1975 through 1977. These larvae take 7 years from recruitment to adult emergence, and a multicohort population was always found. Cohort‐specific values for standing stock and annual production were calculated from size and abundance data for seven cohorts found in each sample. Total standing stock ranged from 6.7 to 12.3 g·m−2 (dry wt), and total annual production values were 5.4, 3.6, and 3.4 g·m−2 in the 3 years. Low temporal variation in both standing stock and annual production results from the multicohort structure of the population.

Life table methods were used to estimate a value of 4.5 g·m−2 for cohort production over a 7‐year life cycle. Cohort P:B was 3.6, which is typical for Chironomus. Annual P:B values averaged only 0.49 because annual standing stock is about seven times greater than average cohort biomass over the life cycle, while annual production is comparable to cohort production.
Particulate matter resuspension via metabolically produced gas bubbles from benthic estuarine microalgae communities
Authors: Durako Michael J. , Medlyn Richard A. , Moffler Mark D.
Published: March 2010

Gas bubbles originating from interstitial and epibenthic organisms in Thalassia testudinum culture and field systems were observed to rise and resuspend adsorbed particulate matter. In culture, 307.9 ml of gas were evolved and 0.97 g dry wt of particulate matter was resuspended·m−2·24 h−1. In situ studies in Tampa Bay, Florida, yielded similar values for gas production, but higher particulate loads. Chromatographic analyses of the bubbles indicated that the major component was photosynthetically produced oxygen. The resuspended particulate matter was 70–96% inorganic; the organic fraction consisted of living organisms and detrital material. This phenomenon may be important in the sediment kinetics and nutrient cycles of estuarine systems.
Monosaccharide composition of acid‐hydrolyzable carbohydrates in particulate matter during a plankton bloom1
Authors: Ittekkot Venugopalan , Degens Egon T. , Brockmann Uwe
Published: March 2010

Monosaccharide composition of acid‐hydrolyzable carbohydrates was analyzed in particulate matter collected during a plankton bloom in the northern North Sea. Concentrations of total particulate carbohydrates varied from 50 nmol·liter−1 to >600, with maximum concentrations in the upper layers above 1% light depth. The monosaccharide spectra, considered in conjunction with those of dissolved carbohydrates from the same samples, suggest that the variations observed were caused by variations in the production of carbohydrates by phytoplankton and significant loss of produced carbohydrates into the dissolved fraction. Two loss phases could be discerned: first, labile glucose polymers, followed by the relatively stable structural polysaccharides.
Comparative rapid ammonium uptake by four species of marine phytoplankton1
Authors: Goldman Joel C. , Glibert Patricia M.
Published: March 2010

A series of 15NH4+ uptake studies with four species of marine phytoplankton, Dunaliella tertiolecta (Dun), Phaeodactylum tricornutum (TFX‐1), Chaetoceros simplex (BBsm), and Thalassiosira weissflogii (Actin), maintained in NH4+‐limited continuous cultures at varying specific growth rates (µ) and temperatures, was done to examine the time‐dependency of NH4+ uptake and the relationship between physiological state and NH4+ uptake. The effect of growth rate on short term NH4+ uptake varied tremendously with species, but the trend of increasing V′M: µ̂ with decreasing relative growth rate (µ:µ̂) was demonstrated by all species down to µ ≃ 0.25% of µ̂. The diatoms, especially, were capable of sustaining a high V′M:µ̂ even at very high relative growth rates. Growth rate also influenced the time‐course of NH4+ uptake: for cells grown at ≈ 0.20–0.35 µ̂ an enhancement in NH4+ uptake was observed in the first 5 min of incubation, but not for cells at >0.90 µ̂. These data are consistent with the hypothesis that phytoplankton may be able to exploit short‐lived nutrient micropatches and may be growing at relatively rapid rates in oceanic waters.
Phosphorus dynamics of the procaryotic nannoplankton in a Michigan lake1
Authors: Lehman John T. , Sandgren Craig D.
Published: March 2010

The small‐celled cyanobacteria that dominate Third Sister Lake, Michigan, during summer have extraordinary uptake capabilities for phosphate. Under enriched conditions, the cells can double their phosphorus content in 2 min or less but can sustain the high rates for only a few minutes. With equal initial access to the nutrient, the small procaryotes are ultimately more successful than are coexisting eucaryotes in converting the nutrient into new cell biomass.
Pyrolysis mass spectrometry of some Scirpus species and their decomposition products1
Authors: Boon Jaap J. , Wetzel Robert G. , Godshalk Gordon L.
Published: March 2010

Four species of bulrushes (Scirpus acutus, Scirpus subterminalis, Scirpus validus, and Scirpus americanus) and the particulate decomposition products of S. acutus and S. subterminalis were analyzed by Curie‐point pyrolysis low‐voltage ionization mass spectrometry. The mass pyrograms of the emergent foliage of the fresh plants showed similarity in distribution of the pyrolysis products from polysaccharides, lignin, and protein. Mass peak m/z 120 differed markedly in relative abundance in these plants and was identified by pyrolysis gas‐chromatography MS as parahydroxystyrene, a pyrolysis product of paracoumaric esters. Decomposition was carried out in the laboratory under aerobic and anaerobic conditions at 10° and 25°C for 180 days. The mass spectra of the senescent S. acutus differed only slightly from the decomposition stages after 180 days at 25°C, but the mass spectra of decomposed senescent submersed foliage of S. subterminalis showed a reduction in pyrolysis products of neutral polysaccharides and an increase in products from proteins and bacterial amino sugar polymers especially after anaerobic decomposition. Large amounts of paracoumaric esters and lignin derivatives were found in all species. These compounds were resistant to degradation, suggesting that paracoumaric esters can influence the slow decay of emergent plants in the littoral zone of lakes.
Seasonal patterns of feeding by natural populations of Keratella, Polyarthra, and Bosmina: Clearance rates, selectivities, and contributions to community grazing1
Authors: Bogdan Kenneth G. , Gilbert John J.
Published: March 2010

Seasonal changes in individual clearance rates, selective feeding behavior, and population grazing rates of Keratella cochlearis, Polyarthra vulgaris, Polyarthra dolichoptera, and Bosmina longirostris were investigated in a eutrophic lake using five tracer foods (Aerobacter, Rhodotorula, Chlorella, Chlamydomonas, and Euglena) and by in situ radioisotope techniques. Clearance rates ranged from <0.002 to 13 µl·ind −1·h−i depending on type of cell and water temperature. Keratella and Bosmina ingested all foods; they preferred Chlamydomonas but differed in their preferences for other species. Polyarthra ingested only Chlamydomonas and Euglena. Significant direct relationships between clearance rates and temperature were found for Keratella, P. vulgaris, and Bosmina feeding on Chlamydomonas and for Keratella feeding on Rhodotorula. The clearance rates of Keratella and Bosmina were inversely related to the concentration of both tracer cells and natural particles (2.5–15‐µm ESD). Temperature and food concentrations accounted for 87 and 89% of the seasonal variation in the clearance rates of Keratella and Bosmina. Although there were days and depths when Bosmina or Polyarthra populations dominated community grazing on Chlamydomonas‐like cells, Keratella populations accounted for about 80% of the grazing pressure on such cells during the year.
Does the surface film of lakes provide a source of food for animals living in lake outlets?
Authors: Wotton R. S.
Published: March 2010

The surface film of lakes is rich in compounds with surface‐active properties. Larvae of the blackfly Simulium noelleri Fried., which aggregate at very high densities on sluice gates below lakes and ponds, can intercept, and ingest, surface film. This is the first report of a lotic animal able to feed on this potential source of nutrients.
Selective impact of filter‐feeding gizzard shad on zooplankton community structure1
Authors: Drenner Ray W. , de Noyelles Frank , Kettle Dean
Published: March 2010

Comparison of ponds containing gizzard shad with control ponds without fish showed that gizzard shad predation suppressed populations of Keratella sp., Diaphanosoma brachyurum, copepod nauplii, Chaoborus sp., and cyclopoid copepodids and adults, but enhanced populations of Diaptomus pallidus copepodids and adults. These results confirm previous laboratory studies which showed that filter‐feeding gizzard shad are not size‐selective predators, as is typically assumed of planktivorous fish, but instead feed on those animals which have little ability to escape, so that their predation results in a community shift toward the more evasive prey.
Measurement of total inorganic carbon in seawater by a substoichiometric assay using NaH14CO3
Authors: Horner S. M. J. , Smith D. F.
Published: March 2010

The total 12CO2 concentration of

a seawater sample can be accurately measured by adding a tracer quantity of NaH14CO3 in solution, acidifying the labeled seawater, and trapping a fraction of the gaseous 14CO2 + 12CO2 with a substoichiometric quantity of a quaternary amine (carbamate). If the same quantity of radioisotope is added to each of a set of standards and unknowns, the radioactivity of the carbamate will depend only on the specific activity of the label in the seawater sample.

The decrease in carbamate radioactivity with increasing total 12CO2 in seawater is described by a simple functional relationship which is readily transformed to a linear equation. The method is well suited to the measurement of minute quantities of CO2 such as might arise from oxidation of dissolved organic carbon.
The dynamics of iron and manganese in a seasonally anoxic lake; direct measurement of fluxes using sediment traps
Authors: Davison W. , Woof C. , Rigg E.
Published: March 2010

Twenty sediment traps were deployed for a year in five arrays at three locations in a seasonal anoxic basin in Esthwaite Water, U.K. Accumulated iron and manganese were measured fortnightly, as were vertical profiles of temperature, oxygen, total iron and manganese, polarographically determined Fe(II) and Mn(II), and light attenuance.

Most of the iron and manganese flows into the lake in winter and is nearly all caught in sediment traps in deep hypolimnetic water, indicating that both elements are transported to the sediment. Accumulation rates in the sediments show that the iron is retained with minimal loss. Although dissolved iron increases to very high concentrations in the hypolimnion during the period of summer anoxia, this accumulation only accounts for a small fraction of the annual iron loading to the lake. The overall cycling of iron in the lake is consistent with a simple conception of sediment‐water interactions. When a redox boundary exists in the water column there is a separate cycle of iron due to vertical transport of ferrous iron by eddy diffusion, oxidation to Fe(III) by oxygen, sinking of the resultant ferric particles, and redissolution to ferrous iron. The manganese cycle contrasts markedly with that of iron. The manganese which reaches the sediment in winter is rapidly reduced and released to the overlying oxic water so that <10% is permanently accumulated in the sediment. During summer the manganese never reaches the sediment because it is reduced and accumulated in the anoxic hypolimnion. Relatively little manganese is supplied from the sediment during this time because the supply of particles is interrupted. Although most of the manganese which enters the lake is washed out again it will nearly all have undergone a redox cycle.
Microbially mediated manganese oxidation in a freshwater lake1
Authors: Chapnick Susan D. , Moore Willard S. , Nealson Kenneth H.
Published: March 2010

Geochemical and microbiological studies support the hypothesis that bacteria mediate manganese oxidation in aerobic bottom waters of Oneida Lake, N.Y. In lake water samples maintained in the laboratory, decreases in soluble Mn2+ and the formation of oxidized manganese (MnO2) occurred only in summer samples which supported metabolically active Mn‐oxidizing bacteria. The eff’ect of initial Mn2+ concentrations on Mn oxidation and on the disappearance of soluble Mn2+ (binding) was studied in water enriched from natural levels (1.2 ± 0.4 µM in June and 0.48 µM in August 1979) to 9.1–200 µM Mn2+. Highly enriched lake water (⩾65 µM Mn2+) inhibited Mn oxidation. Binding and oxidation of Mn was inhibited in filtered samples when particles >0.4 µm were removed, and inhibition persisted when the particles were first ethanol treated and then reintroduced into filtered lake water. Within the range of 0–20 µM Mn2+ rates of Mn2+ binding varied with the initial Mn2+ concentrations in August water samples.
On the free surface oscillations of Lake Ontario
Authors: Hamblin P. F.
Published: March 2010

Standard 1‐h readings of water level are shown to be unsuitable for determining the periods of seiches of Lake Ontario due to contamination by high‐frequency noise (aliasing). During an extensive study of the physical limnology of Lake Ontario, readings of water level at 17 tidal gauges and at 5‐min intervals were used to form smoothed 30‐min estimates of water level. Spectral analyses of these data revealed that numerically calculated periods by the finite element method were within several percent of observed periods and that computed distributions of amplitude and phase of the four lowest gravitational modes generally agreed with field data.
Artificial surface films in the sea area near Sylt1
Authors: Brockmann Uwe H. , Huhnerfuss Heinrich , Kattner Gerhard , Broecker Hans‐Christoph , Hentzschel Gunter
Published: March 2010

An artificial surface film of oleyl alcohol was produced in the North Sea off Sylt Island to investigate the chemical uniformity of the surface film and its influence on gas exchange. Oleyl alcohol concentrations found at the sea surface were in good agreement with previously calculated values. Significant differences between fatty acid concentrations before and after production of the artificial film indicated that the natural surface‐active substances were pushed aside by the spreading oleyl alcohol, with small amounts replenished from the underlying water later. The same displacement effect was inferred from the strong reduction in the number of colony‐forming units of organotrophic bacteria in the presence of an oleyl alcohol slick. Gas exchange, in this case desorption of CO2, was determined before and after formation of the artificial surface film. In the one experiment performed inhibition of exchange was significant when the film was present: without the film equilibrium was achieved after 3.7 min, whereas under the influence of the film, it took 5.7 min to reach equilibrium.
Photosynthetically produced dissolved organic carbon: An important carbon source for planktonic bacteria1
Authors: Cole Jonathan J. , Likens Gene E. , Strayer David L.
Published: March 2010

A serial filtration technique was used to estimate microbial assimilation of photosynthetically produced dissolved organic carbon (PDOC) in Mirror Lake, New Hampshire. A single filtration at one pore size did not separate all heterotrophic microorganisms from photosynthetic algae. It was possible, however, to calculate microbial assimilation of PDOC if filters of several pore sizes were used simultaneously in combination with an independent estimate of heterotrophic activity in each size class.

Microbial net assimilation of algal PDOC in the epilimnion in summer (about 2 µg C·liter−l d−1) was of a magnitude comparable to that of total bacterial production (4–8 µg C·liter−1 d−1) as estimated by the 35SO4 technique. This comparison suggests that PDOC is an important source of carbon for planktonic microbes.

The amount of PDOC measured in the water is smaller than the amount actually released by phytoplankton because microbes metabolize PDOC rapidly. Failure to account for microbial utilization could lead to a serious underestimate of gross PDOC during measurements of primary production.
The sources of alkalinity in Lake Miklavatn, north Iceland
Authors: Einarsson Stefan , Stefánsson Unnsteinn
Published: April 2010

Lake Miklavatn, north Iceland, is highly stratified with an 8–9‐m layer of freshwater overlying saline and anoxic deeper water. Sulfide and ammonia concentrations are high in the stagnant and saline layer, and titration alkalinity exceeds conservative alkalinity in the deepest part of the lake by a factor of 3–4. Reduction of sulfate was estimated by direct measurement of the sulfate concentration. With one exception the decrease in sulfate was found to exceed the measured sulfide concentration. This is explained by partial oxidation of sulfide due to mixing with oxygenated water from the upper layer. The excess alkalinity is 92–93% accounted for by sulfate reduction and formation of ammonia, whereas excess metal carbonates do not seem to be a source.
Coprecipitation of phosphate with calcite in a naturally eutrophic lake
Authors: Murphy T. P. , Hall K. J. , Yesaki I.
Published: April 2010

Phosphorus‐rich deposits of Eocene volcanic rock have caused some lakes in the interior of British Columbia to become eutrophic without direct human influence. In Black Lake the soluble reactive phosphorus (SRP) usually exceeds 250 µg P · liter−1. When calcite precipitation occurred during blooms of Aphanizomenon, SRP was completely removed from the photic zone. In blooms with no calcite formation, SRP changed little. These observations were replicated by splitting the lake with a curtain. Calcite precipitation was also observed several times in four large enclosures (limnocorrals). The subsequent disappearance of phosphate was correlated with an increase in pH and a reduction of Ca and alkalinity and not necessarily with primary production or algal biomass.
Sulfate reduction in the salt marshes at Sapelo Island, Georgia1
Authors: Howarth Robert W. , Giblin Anne
Published: April 2010

Sulfate reduction rates were measured in stands of Spartina alterniflora at Sapelo Island, Georgia, in November 1980 by injecting tracer amounts of 35SO42− into cores, incubating overnight, and analyzing for the incorporation of 35S into reduced sulfur compounds. Qualitatively, sulfate reduction in the Georgia marsh is very similar to that in the Massachusetts marshes we have studied: FeS2 (pyrite or marcasite) is the major end product. Lesser amounts of soluble sulfides, iron monosulfides, and elemental sulfur are also formed. The rate of sulfate reduction (determined by the same method) is significantly lower during November in Georgia than in the Great Sippewissett Marsh in Massachusetts, 0.090 vs. 0.27 moles SO42− · m−2 · d−1 in stands of short Spartina. The lower rates in Georgia may reflect a lower rate of organic carbon input by belowground production. Sulfate reduction appears to be the major form of respiration in the sediments of salt marshes in Georgia as well as in Massachusetts.
Grazing on epiphytes1
Authors: Cattaneo A.
Published: April 2010

A correlation was found between the seasonal epiphyte cycle in Lake Memphremagog (Québec‐Vermont), with a maximum in mid‐June, and the abundance of grazers (mainly oligochaetes and chironomids). Evidence for a cause and effect relationship was provided by exclosure‐enclosure experiments. When grazers were excluded epiphyte biomass did not decline as it did in the lake. Addition of grazers to a dense epiphyte cover resulted in a decline qualitatively and quantitatively similar to that in the lake. Grazing pressure, calculated from general empirical equations for aquatic deposit feeders, was of the required order of magnitude to explain the decline in epiphyte biomass.

Because similar seasonal epiphyte cycles have been described elsewhere these findings should have a wider relevance.
Failure of a sediment‐trapping device
Authors: Reynolds Colin S. , Godfrey Rrian M.
Published: April 2010

Theoretical and practical aspects of the construction of a new apparatus for intercepting sedimentary particulate fluxes are described. Twenty‐five square boxes, brim‐filled with artificial sediment, were positioned on a table about 1 m above the bottom of a lake so that, collectively, they presented a continuous (0.7 m2) interface with the water which was intended to generate boundary‐layer characteristics modeling those of natural lacustrine sediments. Results indicate that the box traps nevertheless seriously underestimated the net sedimentary flux.
Consideration of errors in estimating kinetic parameters based on Michaelis‐Menten formalism in microbial ecology
Authors: Li W. K. W.
Published: April 2010

When microbial heterotrophic activity appears to conform to Michaelis‐Menten kinetics, it is usual to estimate parameters of the model from linearly transformed, but unweighted, data. Theoretical error analysis indicates that if the uncertainties associated with untransformed data are homogeneous within a given experiment, it is inappropriate to fit transformed data in the usual manner. In such cases, an alternative method is proposed whereby untransformed and unweighted data are directly fit to an equivalent nonlinear equation. Results from experiments in the eastern Canadian arctic illustrate this alternative method of estimating kinetic parameters. A comparison of the two methods based on goodness‐of‐fit and precision of parameter estimates shows the alternative method to be more satisfactory.
The chemical composition of lakes in the north‐central United States1
Authors: Gorham Eville , Dean Walter E. , Sanger Jon E.
Published: April 2010

Lake waters of the north‐central U.S.A. are classified into five groups, based on increasing specific conductivity and changes in ionic composition from east to west, from Wisconsin through Minnesota to North and South Dakota. The most dilute group of waters has specific conductivities <29 µmhos · cm−1 at 25°C; the most concentrated group has specific conductances that range from 7,000 to 73,000 µmhos. As conductivity increases all major ions increase, but there is a shift in cation dominance from Ca2 + to Mg2+ to Na+, and in anion dominance from HCO3− to SO42−. This shift partly reflects a westward increase in climatic aridity, and partly a westward sequence of glacial drifts from noncalcareous to calcareous and thence to calcareous with abundant sulfur‐bearing minerals. Levels of pH, K, Cl, F, B, and SiO2 also show a distinct westward increase. Concentrations of NO3− and Mn increase from east to west, but the trend is less distinct. Concentrations of Fe vary widely without any trend over the range of conductivity. Color, mostly from dissolved organic matter, is controlled chiefly by lake depth, except for lakes with extensive peatlands in their drainage basins.
Trophic relationships of the freshwater jellyfish Craspedacusta sowerbyi Lankester 1880
Authors: Dodson Stanley I. , Cooper Scott D.
Published: April 2010

The medusae of the hydrozoan Craspedacusta sowerbyi appear in September in a variety of ponds and lakes in Wisconsin. Short term laboratory feeding trials in about 1 liter of water indicate that the medusae (11.6‐mm diam) consume zooplankton ranging in size from about 0.2 to 2.0 mm and kill but do not eat nekton up to 8.8 mm long. Clearance rate coefficients are as high as 0.9 liter·medusa−1·d−1 for ingested prey and up to 64 liters·medusa−1·d−1 for larger nekton which were killed but not ingested. Neither invertebrate planktonic predators nor fish eat the medusae. Crayfish readily eat medusae which are resting on the bottom of an aquarium. The medusae probably do not reduce zooplankton stocks enough to compete with fish. If Craspedacusta has an effect on zookplankton stocks, it is by reducing the density of other invertebrate predators such as the rotifer Asplanchna.
Selective predation by the backswimmer, Notonecta1
Authors: Scott Mary Ann , Murdoch William W.
Published: April 2010

In laboratory experiments Notonecta hoffmani was size‐selective, although prey size alone did not explain its preference between prey species. When Notonecta was fed mosquito larvae, its preference first increased and then decreased with increasing prey size. Its consistent preference for the larger size class of a given species of zooplankton presumably reflects the fact that all zooplankton were small relative to the predator.

Preference was determined mainly by differences in the relative attack rates on the different prey, but in two instances relative success rates of attacks were equally or more important. Although differences in the frequency of encounter influenced attack rates, the main determinant appeared to be the differences in the predator’s response to different prey once they were encountered. The results suggest that the behavior underlying Notonecta’s preferences is stereotyped and inflexible. The results help explain the effects of Notonecta on field populations of prey.
Dissolved organic materials in surface microlayers: Temporal and spatial variability and relation to sea state
Authors: Carlson David J.
Published: April 2010

Microlayer samples were collected to assess the temporal and spatial variability of their dissolved organic materials (DOM). Dissolved organic carbon (DOC) was often enriched in microlayers but concentration differences between microlayers and bulkwaters were generally small. Ranges of DOC enrichments were large in oceanic samples. Enrichments diminished with increasing bulkwater DOC concentrations in coastal waters and were not influenced by wave states from Beaufort 0 to 4. Microlayer depletions of DOC occurred, but the removal processes responsible for them are unknown. UV‐absorbing phenolic fractions of microlayer DOM were consistently enriched, with the enrichments described by a partitioning relationship, and showed evidence of decreasing enrichment with increasing wave states. In general, over the temporal and spatial scales considered, microlayer DOM variabilities in clean surfaces were not greater than equivalent bulkwater variabilities.