bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions of marine plankton with transuranic elements. 1. Biokinetics of neptunium, plutonium, americium, and californium in phytoplankton
Authors: Fisher Nicholas S. , Bjerregaard Poul , Fowler Scott W.
Published: April 2010

The abilities of seven clones of marine phytoplankton, belonging to six different algal classes, to accumulate transuranic elements were evaluated in laboratory culture experiments. Plutonium, americium, and californium were rapidly concentrated by all species, resulting in volume/volume concentration factors generally >105 for all species and all isotopes. Two natural assemblages from the coastal Mediterranean behaved like the algal cultures. Isotopes associated with cells by a passive adsorption to cell surfaces, with equilibrium between cells and water reached in 3–4 days. Uptake of isotope was directly proportional to the number of suspended particles and the isotope concentration in the culture. Equilibrium isotope concentrations differed between species, reflecting different numbers of transuranic binding sites on the cell surfaces. Generally, the green and blue‐green cells had less reactive surfaces than the diatoms. Once accumulated, Am was lost more rapidly by green algae than by diatoms. Elimination proceeded in two phases, a rapid initial loss and then a slower release. The biological half‐life for Am turnover in the slowly exchanging compartment in the diatom was 10–12 days. No substantial differences in uptake were noted between cultures receiving Pu in the III–IV and V–VI oxidation states. In contrast to the other elements, neptunium showed no detectable accumulation by any of the cells. The results suggest that Pu, Cf, and Am would associate with marine particles which could transport them vertically, transfer them into the marine food web, or both, while Np would behave essentially conservatively in seawater.
Phosphorus and calcium carbonate solubilities in Lake Kinneret
Authors: Avnimelech Yoram
Published: April 2010

Phosphate and calcium carbonate solubilities were calculated from data obtained for near‐bottom water samples from Lake Kinneret during the years 1975–1977. A potential diagram technique was used to determine which solid phase is in equilibrium with the solution.

Both phosphorus and calcium carbonate solubilities are controlled, during the January–August period, through equilibrium with calcium‐carbonate‐phosphate, Ca3(HCO3)3PO4. The calcium carbonate ionic product changes, depending on the phosphoric acid potential, during this period. The solubility product, (Ca2+)3 ×(HCO3−)3 ×(PO43−) is 10−28.5. Calcium carbonate activity is constant (10−8.56) during the last months of the stratified period (September–December).

These findings support the hypothesis that the first and most reactive product of the reactions occurring between CaCO3 and phosphorus is a CaCO3H3PO4 surface complex.
Starvation in Daphnia: Energy reserves and reproductive allocation1
Authors: Tessier Alan J. , Henry Linda L. , Goulden Clyde E. , Durand Mark W.
Published: April 2010

The relationship between energy reserves (biomass and triacylglycerol) and starvation time is investigated for two planktonic Cladocera, Daphnia. galeata mendotae and Daphnia magna. Triacylglycerol storage is correlated to total individual biomass independently of body size. Adult biomass increases twofold to threefold during the intermolt, with triacylglycerol accounting for 16% of the total increase. The amount of triacylglycerol transferred into each egg depends on the adult’s feeding success.

Starvation time is correlated to body mass; however, triacylglycerol storage and reproductive allocation modify the relationship. Although adult biomass and percentage of lipid both increase during intermolt, animals in late intermolt starve sooner than those in early‐middle intermolt because of the transfer of energy reserves to the ovaries for reproduction. Daphnia magna neonates with high maternal lipid survived twice as long as neonates with low maternal lipid but similar body mass.
Photosynthetic parameters of arctic marine phytoplankton: Vertical variations and time scales of adaptation
Authors: Gallegos Charles L. , Platt Trevor , Harrison W. G. , Irwin Brian
Published: April 2010

In the eastern Canadian arctic the photosynthesis‐irradiance curves of phytoplankton from the 50% and 1% light levels differ mainly in their susceptibility to photoinhibition. The photoinhibition parameters of deep populations and the intensity of the deep chlorophyll maximum were correlated with N2, the bulk stratification parameter of the water column. Comparison of data from the same region in different periods suggests that the characteristic susceptibility to photoinhibition requires 2–6 weeks to develop once a population is isolated below a pycnocline.

Insensitivity to photoinhibition developed much more quickly when a population from the chlorophyll maximum was exposed to surface light. The threshold of photoinhibition increased rapidly, reaching surface intensities within 4–6 h. The adaptation is sufficiently rapid that phytoplankton from the chlorophyll maximum should be stressed only briefly when transported to the surface by a mixed‐layer‐deepening event.
Alkaline phosphatase inhibition by copper: Implications to phosphorus nutrition and use as a biochemical marker of toxicity1
Authors: Rueter John G.
Published: April 2010

Alkaline phosphatase activity is inhibited by copper in phytoplankton cultures, cell‐free enzyme preparations, and natural populations of phytoplankton. Inhibition in all these systems is rapid and a function of cupric ion activity, supporting the hypothesis that the cellular enzyme is directly exposed to the aqueous medium. These characteristics of the enzyme allow two applications: purified bacterial enzyme can be used to assay the cupric ion activity in filtered water samples, and the inhibition of the activity in natural populations is a biochemical marker for overall toxicity.
Photosynthesis of benthic microflora measured with high spatial resolution by the oxygen microprofile method: Capabilities and limitations of the method1
Authors: Revsbech Niels Peter , Jorgensen Bo Barker
Published: April 2010

The photosynthetic rates of the microflora in sediments were determined by a new oxygen microprofile method which involves the use of 2–10‐µm‐thick oxygen microelectrodes. The spatial resolution of the measurements is ca. 0.1 mm when the photosynthesis is determined within 1 s. The high resolving power of the method makes it possible to analyze in detail the vertical distribution of photosynthetic activity in sediments. Gas bubbles within the sediment normally interfere with the measurement of photosynthetic rate by oxygen methods, but the high spatial resolution of this method makes such interference negligible.
Unknown chlorophyll a derivatives in the North Sea and the tropical Atlantic Ocean revealed by HPLC analysis1
Authors: Gieskes Winfried W. , Kraay Gijsbert W.
Published: April 2010

Concentrations of chlorophylls and major carotenoids were measured in algal cultures and particulate matter from the neritic North Sea and the tropical Atlantic Ocean by conventional spectrophotometric and fluorescence acidification methods and by quantitative high‐performance liquid chromatography (HPLC). In cultures, the Chl a concentration was similar whether measured by HPLC or conventional methods. In natural samples from the North Sea and the coastal zone of the central Atlantic Ocean several pigments with light‐absorbance and fluorescence properties resembling Chl a, but chromatographically different, were responsible for overestimates of up to 40% with the conventional methods. An even greater discrepancy between methods occurred in tropical open oceanic water, where a green pigment with absorption maxima in diethyl ether at 436 and 661 nm explained >85% of the difference between HPLC and the conventional methods. This unidentified Chl a derivative was associated with particles <1 µm which contained zeaxanthin as the major carotenoid. Its concentration was up to three times that of “normal” Chl a, assuming identical extinction coefficients.
The temperature optimum of the nitrate reductase assay for marine phytoplankton1
Authors: Kristiansen S.
Published: April 2010

Nitrate reductase in crude extracts of phytoplankton from cultures and from natural populations from the Oslofjord (Norway) was assayed at different incubation temperatures. The temperature optimum of the enzyme was 10°–15°C and 15°–20°C for cultures and about 10°C for natural plankton. The utility of the nitrate reductase assay as an ecological tool is greatly diminished unless performed at the temperature optimum.
Instrumentation for the measurement of phytoplankton production1
Authors: Taylor Craig D. , Molongoski John J. , Lohrenz Steven E.
Published: April 2010

Automated instrumentation is described that performs time‐course incubation experiments directly in situ where natural conditions of temperature, light, hydrostatic pressure, etc. can be maintained. The sampler incubation device (SID) takes a 1‐liter sample from the water and simultaneously introduces an appropriate radiotracer. During subsequent in situ incubation, 50‐ml subsamples are withdrawn from the main sample at equally spaced intervals and preserved for laboratory analysis. Representative experiments revealed nonlinear carbon uptake within 0.5–1.0 h, emphasizing that even brief end‐point analyses can lead to large errors in estimating phytoplankton production rates. Studies of the rapid fluctuation in phytoplankton activity resulting from cloud‐induced variations in light intensity and the application of cellular fractionation methods for measuring the intracellular distribution of newly fixed carbon illustrated the utility of instrumental time‐course techniques for studying phytoplankton physiology and community metabolism in situ.
A new incubator for measuring photosynthetic activity of phototrophic microorganisms, using the amperometric oxygen method1
Authors: Zevenboom Wanda , Post Anton F. , Van Hes Udo M. , Mur Luuc R.
Published: April 2010

A new incubator was developed for measuring photosynthesis under strictly controlled conditions, using the amperometric oxygen technique. The most important feature is an incubation vessel equipped with a cooling circuit to keep temperature constant at any desired value ±0.05°C. The shape of the vessel and the virtually parallel light bundle allow determination of the light irradiance experienced by the algae. Samples can be exposed to five different irradiance values (0–1,250 W · m−2) simultaneously, without affecting light quality. The photosynthetic response is continuously registered for the study of time‐dependent processes in oxygen evolution.
Time and space scales of vertical mixing and advection of phytoplankton in the upper ocean
Authors: Denman K. L. , Gargett A. E.
Published: April 2010

The dependence of phytoplankton photosynthesis on light intensity may be altered by the range and frequency of variations in light intensity recently experienced by the organisms. A major source of the fluctuations in light intensity experienced by phytoplankton in the upper ocean is vertical motion. We estimate time and space scales for vertical displacements of phytoplankton caused by turbulent mixing, internal waves, Langmuir circulations, and double diffusive processes. In the surface layer, depending on windspeed, current shear and stratification, we find that time scales for cycling of phytoplankton by turbulent eddies and mixing vary from about 0.5 h to hundreds of hours for vertical displacements of the order of 10 m. In the seasonal thermocline, turbulent diffusive time scales for displacements as small as several meters are weeks to months, whereas similar displacements by internal waves occur over periods of several minutes to several hours, according to the strength of the density stratification, and are then dominant. Langmuir cells seem to scale as the large turbulent eddies and need not be treated separately, and double diffusive processes seem to be of minor importance. The formulation used here of a vertical turbulent diffusion coefficient Kz as a function of observable quantities—ε the rate of dissipation of turbulent kinetic energy, arid N the local buoyancy frequency—should also be useful for estimating vertical fluxes of nutrients. In addition, this formulation is reversible in time and can be used to estimate the recent depth and light history of phytoplankton taken from the upper ocean.
The production of bacteria attached to particles suspended in a freshwater pond1
Authors: Kirchman David
Published: April 2010

The biomass and activity of particle‐bound bacteria in a small freshwater pond were examined during 2 years. The percentage of total bacteria attached to particles was highest (3%) in the months of July through October. During this period the number of bacteria per particle and the number of particles per milliliter were also relatively high. An average attached bacterium was larger than an unattached bacterium in July and August but not in February and May. Cell volumes of both populations were larger in summer than in winter. The uptake of three 14C‐labeled compounds and the incorporation of [3H]thymidine into macromolecules were also examined. Although there was no seasonal pattern in the percentage of activity contributed by the >3.0‐µm fraction, this fraction took up relatively more glucose (21% of total uptake) than glutamate (12%) or acetate (6.8%). Thymidine incorporation by the large bacteria was relatively low (2.8%). The production of bacteria attached to particles was estimated from rates of thymidine incorporation and used to estimate the remineralization rate of detrital carbon by particle‐bound bacteria. Detrital carbon in Ice House Pond was apparently not remineralized substantially by particle‐bound bacteria.
Estimates of the resistance to chemical transport posed by the deep‐sea boundary layer1,2
Authors: Santschi Peter H. , Bower Peter , Nyffeler Urs P. , Azevedo Antonia , Broecker Wallace S.
Published: April 2010

A strategy has been developed to permit the in situ calibration of measurements made with benthic chambers of chemical fluxes across the sediment‐water interface. The resistance to chemical transport posed by the boundary layer is estimated using chemical transport techniques in benthic flux chamber mock‐ups and on the sea floor. Dissolution from gypsum (alabaster) plates is measured both inside and outside the flux chambers. CaCO3 dissolution and radioisotope uptake techniques are suitable for laboratory and deep‐sea calibration of benthic fluxes. Broadly concordant resistance estimates have been achieved within flux chambers with these three quite different approaches. An estimate of 470 µ for the equivalent stagnant boundary film thickness has been made by the alabaster method on the sea floor at MANOP site H in the eastern Pacific. The transport of Mn2+ from the bottom waters to site H nodules, if controlled by diffusion through a film of this thickness, would be sufficient to explain their growth rates.
Effect of competitive interactions between manganese and copper on cellular manganese and growth in estuarine and oceanic species of the diatom Thalassiosira1,2
Authors: Sunda William G. , Huntsman Susan A.
Published: April 2010

We investigated the relationship between growth rate and cellular manganese concentrations for an estuarine diatom Thalassiosira pseudonana (clone 3H) and a related oceanic species Thassiosira oceanica (clone 13‐1). Both species were exposed to a matrix of low manganese and cupric ion activities using ethylenediaminetetraacetic acid (EDTA)‐trace metal ion buffered seawater media. The growth rate of Mn‐limited cultures was related to the cellular concentration of Mn, which in turn was directly related to manganese ion activity and inversely to cupric ion activity. The interaction between manganese and cupric ion activities in controlling cellular manganese and growth rate could be explained quantitatively by competitive binding models in which copper competitively blocked either cellular manganese uptake or the binding of manganese within intracellular pools.

Clone 13‐1, isolated from Mn‐poor Sargasso seawater, was able to grow more rapidly at low manganese ion activities than clone 3H, isolated from a eutrophic estuary, provided that cupric ion activity remained below ca. 10‒11 mol·liter‒1. Adaptation of 13‐1 to growth at low Mn activities appeared to involve two mechanisms: a greater ability for cellular uptake of manganese and a lower cellular manganese requirement (i.e. Mn cell quota) for growth. Comparison of our data with estimates of manganese and cupric ion activities in marine waters suggests that manganese deficiency could be important in controlling phytoplankton growth rate or community composition in some marine waters.
Diel cycles of reproduction and vertical migration in the rotifer Keratella crassa and their influence on the estimation of population dynamics1
Authors: Magnien Robert E. , Gilbert John J.
Published: April 2010

Diel cycles of reproduction and vertical migration were observed in the rotifer Keratella crassa. Egg‐hatching synchrony was pronounced during summer, when 73–93% of eggs hatched during a 6–7‐h period. Reproductive synchrony was evident before the egg development stage and may have arisen during oogenesis in response to diel changes in lake temperature. Vertical migration was generally upward at night and downward during the day. These movements differed in timing, however, for ovigerous and nonovigerous females. Ovigerous animals reached their lowest and highest positions in the water column about 4 and 6 h later than nonovigerous animals. This differential migration produced diel changes in the depth profile of egg ratio. These findings of egg‐hatching synchrony and vertical migration have important implications for studies of zooplankton population dynamics. In the 2 years of this study, sampling at different times of day produced daily variations in egg ratios and calculated instantaneous birth rates that approached an order of magnitude.
The carbonate system in hypersaline solutions: Alkalinity and CaCO3 solubility of evaporated seawater
Authors: Lazar B. , Starinsky A. , Katz A. , Sass E. , Ben‐Yaakov S.
Published: April 2010

Changes in total alkalinity and in pH during the evaporation of seawater in the laboratory were studied for an evaporation range extending between 1.1 and 26 (as defined by the concentration ratio of Mg in the evaporated sample relative to mean ocean water).

The evaporation experiments were performed with and without suspended aragonite. The results of the two experimental sets define an alkalinity field for evaporated, marine‐derived brines. Data from naturally formed marine brines fall within the experimental field. Deviations therefrom can be explained by changes in alkalinity unrelated to CaCO3 precipitation/ dissolution reactions.
Comparison of different procedures for the simulation of temperature oscillations in Radunia Lake, Poland
Authors: Jedrasik J. , Simons T. J.
Published: April 2010

Two‐layer models and multilevel temperature models are compared for simulating internal oscillations in Radunia Lake, Poland, and calculations on a two‐dimensional horizontal grid covering the lake are compared with one‐dimensional calculations applied to a longitudinal section of the lake. Effects of the free surface, rotation, depths, and density gradients on the periods of thermocline oscillations are evaluated.
Horizontal diffusivity in a small, ice‐covered lake1
Authors: Colman John A. , Armstrong David E.
Published: April 2010

A horizontal eddy diffusivity (Kx) value of 0.47 cm2 · s‒1 was calculated from tracer cloud expansion data from a previous experiment in which a 24Na solution was introduced as a point source under ice cover in Tub Lake, Wisconsin. This Kx value, the first from a lake where surface wind stress was not a factor, is lower than any lake Kx previously reported. The constancy of Kx found for the 48‐h period of monitoring implied mixing eddy lengths <1.6 m, the diffusion cloud size found at first monitoring. Surface seiches or convective flows appeared to be probable sources of mixing energy.
Buoyancy regulation in a natural population of Oscillatoria spp. in fishponds1
Authors: van Rijn Jaap , Shilo Moshe
Published: April 2010

The effect of light, CO2, and in organic nitrogen on buoyancy were examined in a natural population of Oscillatoria spp. in fishponds. CO2 and inorganic nitrogen had opposite effects on buoyancy while light was an overriding factor regulating buoyancy. Under normal pond conditions in which both CO2 and inorganic nitrogen become limiting, most of the Oscillatoria spp. were positively buoyant. The addition of CO2 at this stage decreased buoyancy, while the further addition of NH4Cl led to a regaining of high buoyancy.
Chlorophyll determinations with filter fluorometer: Lamp/filter combination can minimize error1
Authors: Baker Karen S. , Smith Raymond C. , Nelson James R.
Published: April 2010

A correct lamp/filter combination is essential in order to optimize the accuracy of chlorophyll measurements made with filter fluorometers. For example, a nonoptimum lamp in a Sequoia‐Turner 111A fluorometer can affect the acid ratio. The magnitude of the acid ratio factor dictates the size of the error propagation from calibration to chlorophyll determination. A low value of the acid ratio causes a greater uncertainty in the chlorophyll determination. As long as the acid ratio is ≥2.0, any error in the acid ratio, which is determined at the time of instrument calibration, is not amplified in the calculations of chlorophyll concentration.
Population dynamics of halobacteria in the Dead Sea water column1
Authors: Oren Aharon
Published: April 2010

A bloom of halobacteria in the Dead Sea is described, and the factors triggering its rise and decline are analyzed. The bloom developed in summer 1980, reaching population densities of up to 1.9 × 107 cells·ml‒1 and imparting a red color to the water. The bloom was restricted to the upper 10–25 m of the water column. After a sharp decrease in cell numbers during the last months of 1980 the population density stabilized at values of around 5 × 106 cells·ml‒1 surface water for more than a year. Enrichment experiments performed during that period showed that the nutrients limiting bacterial development were phosphate and suitable carbon sources. The turnover of phosphate appeared to be extremely slow (estimated turnover times as long as 240–1,200 days), suggesting that the population, a significant part of which proved viable, existed in a state of very little activity.
Spatial and temporal fluctuations of methane production in anoxic coastal marine sediments
Authors: Crill Patrick M. , Martens Christopher S.
Published: April 2010

In vitro rates of net methane production and sulfate reduction were measured at various depths from October 1979 to November 1981 in anoxic coastal marine sediments from Cape Lookout Bight, N.C. In sulfate‐rich surface sediments at 1–4 cm, calculated methane production rates were within the experimental error of 0.011 mM CH4·d‒1. The depth of maximum methane production rate varied from 7–30 cm from summer to winter with summer maxima at the shallower depth. A maximum rate of 0.305 mM CH4·d‒1 was measured at 7–10 cm during July 1981. At intermediate depths low rates of methane production were observed in the presence of low concentrations of dissolved sulfate; however, these rates were near or within experimental error. Integrated rates of sediment column methane production ranged from 20 µmol·m‒2·h‒1 in April to 2,000 in August. These rates compared well with previously measured CH4 sediment— water fluxes measured in sediments from the same field site in 1977. The total methane flux then ranged from 50 to 2,600 µmol CH4·m‒2·h‒1.
Bacterial utilization of algal extracellular products. 3. The specificity of algal‐bacterial interaction
Authors: Bell Wayne H.
Published: April 2010

Kinetic analyses were made of the utilization of 14C‐labeled algal extracellular products (EP) by bacterial populations in continuous algal cultures containing steady state Skeletonema costatum or Dunaliella tertiolecta. The development of bacteria adapted to the respective algal species was revealed by gradual evolution of a common X‐intercept for net EP uptake and respiration lines from initially disparate estimates. When the adapted populations were given labeled EP prepared from other algal species, linear kinetics were retained but the X‐intercepts for net uptake and respiration failed to coincide. Bacterial response to a given algal EP pool does not necessarily preclude enzyme‐mediated utilization of organic substrates from other species. Rapid utilization of algal EP appears to be a consequence of bacterial adaptation to existence under dilute nutrient conditions rather than a response to a specific alga. Prolonged exposure to a single alga may favor the development of bacterial populations in which metabolism is limited by enzyme‐mediated transport of the compounds available in its EP pool, but this phenomenon is less significant ecologically than the general stimulation of bacterial activity effected by the increased supply of these compounds.
A simple model to predict extinction coefficients and phytoplankton biomass in eutrophic waters1
Authors: Wofsy S. C.
Published: April 2010

Data from nutrient‐saturated rivers, estuaries, and coastal upwelling zones imply a simple relationship between phytoplankton standing crop, depth of the mixed layer, and extinction due to nonliving material. Systems evolve to a steady state where the optical depth of the mixed layer is between 5 and 10. The observations are interpreted using a model for light‐limited growth of phytoplankton. Model parameters can be evaluated using measurements of total extinction coefficient, mixed layer depth, chlorophyll concentration, and suspended sediment concentration. Simple equations are derived for the capacity of polluted rivers to assimilate anthropogenic nutrients. These relations may be used to assess the effects of water pollution control projects on water quality.
Primary production of marine snow during and after an upwelling event1
Authors: Prgzelin Barbara B. , Alldredge Alice L.
Published: April 2010

Marine snow (flocculent macroscopic particles) collected during an upwelling event near Santa Barbara, California, was recently formed and inhabited by phytoplankton physiologically similar to those free‐living in the water. At least 20% of all primary production, Chl a, and phytoplankton occurred on this marine snow, suggesting that a significant fraction of new organic carbon entering the upwelling food chain is available to large‐particle feeders or passes directly through the detrital food chain on particles. In contrast, marine snow collected 2 weeks after the upwelling event was inhabited by a physiologically distinct community of aging, senescent phytoplankton; <1% of total primary production and Chl a occurred on this marine snow. High dark fixation rates, high RUBPCase activity on photosynthetically depressed snow, and high ammonium concentrations within this snow suggest that chemoautotrophic bacteria, possibly nitrifying bacteria, may be particularly active on these macroscopic particles.
Limitation of marine phytoplankton reproductive rates by zinc, manganese, and iron1
Authors: Brand Larry E. , Sunda William G. , Guillard Robert R. L.
Published: April 2010

The reproductive rates of 21 species of marine phytoplankton were measured in media in which free zinc, manganese, and iron ion activities were controlled at different levels using EDTA‐trace metal ion buffer systems. In general, the reproductive rates of neritic species were limited by zinc activities below 10‒11.5 M, while those of oceanic species were either not limited or only slightly limited at the lowest zinc activity attained in the experiment, ca. 10‒13 M. The reproductive rates of oceanic coccolithophores were either not limited or only slightly limited by the lowest manganese ion activity attained, ca. 10‒11 M, but those of a neritic coccolithophore and all diatoms, both neritic and oceanic, were limited below a manganese activity of 10‒10 M. Neritic species had reduced reproductive rates in media containing <10‒7 M iron while oceanic species reproduced at maximal or close to maximal rates in the media with the lowest iron concentrations, ca. 10‒9 M. The habitat‐related patterns in zinc, manganese, and iron requirements of oceanic and neritic species are consistent with the oceanic‐neritic distributions of concentrations of these metals. This similarity in requirement and distributional patterns provides evidence that Zn, Mn, and Fe availability have been important selective forces on marine phytoplankton populations and communities.
Problems with accurate carbon measurements in marine sediments and particulate matter in seawater: A new approach1
Authors: Weliky Karen , Suess Erwin , Ungerer C. Andre , Muller Peter J. , Fischer Kathy
Published: April 2010

The determination of carbon concentrations in marine sediments and particulate matter is hindered by the difficulty in analytically partitioning the total carbon between organic carbon and carbonate carbon phases. Attempts to “selectively” remove organic carbon by burning the sample at 500°C, or carbonate carbon by acidifying with HCl, usually affect the carbon of the remaining phase as well.

A new approach permits direct measurement of both organic and carbonate carbon in a single sediment sample. The carbonate carbon concentration is determined from the CO2 evolved during phosphoric acid treatment. Subsequently, a concentrated dichromate/sulfuric acid solution is added to the remaining sediment‐acid mixture, and the CO2 liberated from the oxidation of organic carbon is measured. Total carbon is calculated as the sum of organic and carbonate carbon. A LECO carbon analyzer is modified so that the amount of CO2 evolved can be measured by the instrument’s thermal conductivity detector. In addition, total carbon content is determined on another subsample using the LECO dry combustion furnace. This provides a check on the values determined by the H3PO4/dichromate technique. Any other commercially available instrument relying on combustion furnace and thermal conductivity or infrared absorption for CO2 detection could be converted in an analogous manner.
Determination of nitrate and nitrite in seawater by flow injection analysis1
Authors: Johnson Kenneth S. , Petty Robert L.
Published: April 2010

An inexpensive and very reliable technique for the determination of nitrate and nitrite in seawater is based on the conventional method of reducing nitrate to nitrite and the colorimetric determination of the nitrite as an azo dye, with a modification of the technique of flow injection analysis used to automate the processing of samples. More than 75 determinations can be made per hour on a flowing stream of seawater, such as the effluent from an in situ pump. Discrete samples can be run at a rate of 30·h‒1 with duplicate determinations of each sample. The detection limit is 0.1 µM. Precision is better than 1% at concentrations >10 µM.
Peru upwelling region sediments near 15°S. 1. Remineralization and accumulation of organic matter1
Authors: Henrichs Susan M. , Farrington John W.
Published: April 2010

Six cores were obtained along a 70‐km transect perpendicular to the Peru coast in the highly productive upwelling region near 15°S, at depths ranging from 90 to 5,300 m. All of the sediments sampled were diatomaceous oozes. Three cores overlain by poorly oxygenated water had Thioploca‐like filamentous bacteria in surface sediments. Total organic carbon and total nitrogen contents of the sediments ranged from 0.8 to 10% and from 0.1 to 1% (dry wt). For the 90‐m and 268‐m cores, which had 210Pb surface sediment accumulation rates of about 0.6 and 1.1 cm · yr‒1, surface sediment organic carbon accumulation rates were 40 and 70 g C·m‒2·yr‒1. The organic carbon and total nitrogen distributions in the three cores from the oxygen minimum zone indicate that there have been variations in the rate of accumulation of organic matter over time. These variations may be related in part to the frequency and intensity of El Niño events.

Porewater ammonium, nitrate, nitrite, total carbon dioxide, sulfate, and sulfide concentrations were measured. Remineralization rates in sediments calculated from the dissolved carbon dioxide profiles range from 0.6 to 20 g C·m‒2·yr‒1. Total carbon dioxide concentrations in porewaters of two oxygen‐minimum‐zone sediments were modeled using both steady state and nonsteady state distributions of metabolizable organic matter.
Peru upwelling region sediments near 15°S. 2. Dissolved free and total hydrolyzable amino acids1
Authors: Henrichs Susan M. , Farrington John W. , Lee Cindy
Published: April 2010

Dissolved free and total hydrolyzable amino acid concentrations were measured in five cores of Peru coastal sediments collected along a 70‐km transect perpendicular to the coast in the upwelling region near 15°S at depths of 92, 268, 506, 1,428, and 5,300 m. Total hydrolyzable amino acids (THAA) made up 20–70% of the total nitrogen in these sediments, with the highest proportions in surface sediments of the 92‐, 268‐, and 506‐m cores. Variations in THAA content with depth were attributable to a combination of remineralization and varying inputs to the sediment surface over time. The individual amino acid residue composition was remarkably uniform, both with depth in core and between stations.

Dissolved free amino acid (DFAA) concentrations ranged from about 1 µM to µM. The highest concentrations were found near the sediment‐water interface of sulfide‐containing sediments. Concentrations generally decreased with depth in sediment. Glutamic acid was a major constituent of nearly all samples, suggesting a bacterial source for most of the DFAA. A nonprotein amino acid, β‐aminoglutaric acid, was also a major component and was the most abundant DFAA below 20‐cm depth in the 92‐, 268‐, and 506‐m cores. The major trends in DFAA concentration and composition appear to be the net result of biological (largely bacterial) sources and sinks.
Transport and breakdown of fecal pellets: Biological and sedimentological consequences1
Authors: Taghon Gary L. , Nowell Arthur R. M. , Jumars Peter A.
Published: April 2010

Fecal pellets of benthic animals are important in sediment transport processes, yet few quantitative data are available on their salient physical characteristics. We measured, directly and independently, the densities (specific gravities), sizes, and settling velocities of pellets produced by Amphicteis scaphobranchiata, a deposit‐feeding polychaete worm. Pellet density was measured by an isosmotic density gradient technique. Densities ranged from 1.086 to 1.282 g·cm‒3 and settling velocities from 3.03 to 5.94 cm·s‒1. Pellets transported as bedload for variable distances; the oldest pellets tested (6 h after production) traveled a median distance of 3.1 m, while freshly egested pellets traveled 9.5 m before disintegrating. Worms would reingest disaggregated pellets, but feeding rates correlated positively with pellet age, consistent with previous findings that this species feeds at a faster rate on energetically more profitable sediment. These results suggest substantial interactions among benthic animals, fecal pellets, and sediment transport processes.
Phenotypic associations in the Bosminidae (Cladocera): Zoogeographic patterns1
Authors: Sprules W. Gary , Carter John C. H. , Ramcharan Charles W.
Published: April 2010

The hypothesis that enlarged antennules and mucrones in Bosminidae are adaptations to invertebrate predation pressure is tested in a range of physically diverse and geographically disparate lakes. In lakes with many abundant invertebrate predators, small bosminids tend to have longer mucrones, for a given body size, than they do in low‐predator lakes; larger, less vulnerable bosminids show no such pattern. There is a much weaker, inverse relation between antennule length and predator abundance. Given that many of the study lakes are large and presumably ecologically complex, our data suggest not only that invertebrate predation is a considerable force in freshwater ecosystems but also that there is an enormous survival advantage for small prey species in the modification of their morphology.
The relative importance of bacterioplankton and phytoplankton in phosphorus uptake in freshwater1
Authors: Currie David J. , Kalff Jaap
Published: April 2010

In several studies of orthophosphate cycling in lakes, most of the phosphorus uptake has been associated with the smallest limnetic particles. The hypothesis that bacteria rather than phytoplankton are responsible for most P uptake in situ was tested in Lake Memphremagog by means of size fractionation of [32P]orthophosphate uptake, [14C]glucose uptake (as an indicator of bacterial activity), and both [14C]bicarbonate uptake and chlorophyll a (as indicators of algal activity). In biweekly samples from May to October, particles <3.0 µm accounted for 72–98% (median 94%) of the uptake of orthophosphate. There was no diel variation in the fraction of uptake by particles <3.0 µm. The bacterial contribution to the total community uptake of orthophosphate was estimated to range between 97 and 100% over all samples collected. However, the phosphorus released (shown not to be orthophosphate) was taken up almost entirely by the phytoplankton. The bacterioplankton apparently strongly dominates orthophosphate cycling in situ, while the phytoplankton seems to obtain most of its phosphorus from excreted organic P compounds.
Effect of flavor and size on selection of food by suspension‐feeding plutei1
Authors: Rassoulzadegan Fereidoun , Fenaux Lucienne , Strathmann Richard R.
Published: April 2010

Plutei ingested plastic spheres previously incubated with algal cells at higher rates than plastic spheres incubated with filtered seawater. The attractive factor overrode or modified preferential ingestion of spheres of different sizes. The cultured algae were centrifuged and resuspended before the plastic spheres were exposed to the algal cells, so it is probable that natural materials associated with the algal cells were transferred to the plastic spheres and triggered the selective ingestion of particles. Capture on the basis of flavor could be especially important for those suspension feeders that actively respond to particles in order to capture them; if they concentrate only nutritious particles, then they avoid subsequent problems of sorting and handling. Preconditioning plutei by feeding with algal cells of one of two sizes does not increase preference for untreated spheres of the algal size.
Uptake of sediment ammonium and translocation in a marine green macroalga Caulerpa cupressoides1
Authors: Williams Susan Lynn
Published: April 2010

15NH4+ was taken up by algal rhizoids and translocated to photosynthetic portions of the thalli. The half‐saturation constant for NH4+ uptake (Ks = 107 µM N) was similar to concentrations in interstitial waters, indicating algal adaptation to nutrient sources in the sediment rather than those of the nutrient‐limited water.
Extraction, identification, and quantitation of phycobiliprotein pigments from phototrophic plankton
Authors: Stewart Dianne E. , Farmer Franklin H.
Published: April 2010

The water‐soluble phycobiliprotein (phb) pigments are confined to two important taxa of photosynthetic microorganisms (Cyanobacteria, Cryptophyta). Detection and quantitation of these pigments in a manner analogous to that of chlorophyll can provide more information about the composition of the plankton population than chlorophyll analysis alone. A technique is described for the extraction, identification, and quantitation of phycoerythrins and phycocyanins from cultures and seawater samples. A means of distinguishing the predominant phb‐containing component of a sample is suggested. Analysis of estuarine samples indicates an average phycocyanin content of 0.043 µg·liter‒1 from cyanobacteria and a phycoerythrin average of 0.005 µg·liter ’ from cryptophytes.
A simple plankton splitter with i note on its reduced subsampling variance
Authors: George D. G. , Hurley M. A. , Winstanley B.
Published: April 2010

A simple compartment‐type devicefor splitting plankton samples is described which can split small volumes of liquid with an accuracy of about 1% and provides unbiased subsamples of the plankton in suspension. The variance generated by the device is much less than expected from binomial theory and remains relatively constant over a range of sample sizes. Possible reasons for this characteristic are discussed, and an empirical estimate of the reduced variance is used to calculate narrower confidence intervals.
Physical factors controlling summer distribution of chlorophyll a off southwestern Nova Scotia1
Authors: Fournier R. O. , Van Det M. , Hargreaves N. B. , Wilson J. S. , Clair T. A. , Ernst R.
Published: April 2010

Three cruises were taken in summer off southwestern Nova Scotia to elucidate the mechanisms which contribute to the high levels of biological productivity in this area. Biological processes are dominated during summer by the turbulent dissipation of tidal energy which produces a nutrient‐rich inshore zone at the surface which gradually becomes stratified in the offshore region. The center of the transitional zone, which separates well mixed from strongly stratified, is marked by a front where chlorophyll concentrations are usually highest. On three occasions over 4 years these regions of high chlorophyll showed considerable spatial similarity, although concentrations varied by a factor of three.
Seasonal dynamics of nutrient limitation in a tropical high‐altitude lake (Lake Titicaca, Peru‐Bolivia): Application of physiological bioassays1
Authors: Vincent Warwick F. , Wurtsbaugh Wayne , Vincent Connie L. , Richerson P. J.
Published: April 2010

Five types of physiological assay were applied to samples from three sites in Lake Titicaca, Peru‐Bolivia (16°S), to assess the magnitude and seasonality of N or P limitation of algal growth. Phosphorus appeared to be in abundant supply relative to growth requirements throughout 1982. Alkaline phosphatase levels were low (<3 nmol substrate converted·µg‒1Chl a·liter‒1), 32PO43‒ turnover times were always long (> 103 min in the main body of the lake), and little or no phosphorus was accumulated by the seston during short term enrichments. Ammonium enhancement assays suggested a persistent cellular shortage of nitrogen throughout all seasons in the plankton of a large shallow bay, and in the main basin when the water was stratified. High ammonium uptake capacities, as measured with the NH4+ analogue [14C]methylammonium, and selective accumulation of nitrogen from N plus P enrichments provided supportive evidence of cellular N deficiency. Winter mixing brought large quantities of NO3‒ and SRP into the surface euphotic zone of the main basin, and throughout this period neither N nor P appeared to be limiting. Polymixis in the shallow bay resulted in large variations in nitrogen supply and deficiency, and these effects were modulated in part by changes in depth of the euphotic zone. Nitrogen was always in low abundance relative to phosphorus in Lake Titicaca, but the extent of nutrient control on algal growth varied considerably with site and time of year.
A model of the vertical mixing in Lake Erie in summer
Authors: Ivey G. N. , Patterson J. C.
Published: April 2010

A vertical one‐dimensional model is proposed to describe the vertical mixing in the central portion of the central basin of Lake Erie in summer. The model explicitly describes the various mechanisms which operate in the well mixed upper and bottom layers. The model predictions are in good agreement with the observed thermal structure over the entire water column during a month‐long simulation period.
Pyrite formation and the measurement of sulfate reduction in salt marsh sediments1
Authors: Howarth Robert W. , Merkel Susan
Published: April 2010

A new method was used to study the formation of pyrite plus elemental sulfur during 35SO42‒ reduction experiments in salt marsh sediments: the reduction with chromium(II) of pyrite and elemental sulfur to hydrogen sulfide. It is both more specific and more sensitive than our previous method, the oxidation of pyrite and elemental sulfur to sulfate by aqua regia, which measures the formation of refractory organic sulfur compounds as well as pyrite and elemental sulfur. A direct comparison of the two methods in salt marsh sediments in Georgia and in Massachusetts showed that they compare very well. The chromium(II) reduction method, combined with our previous results, conclusively shows that pyrite is the major product of 35SO42‒ reduction measurements in these sediments. The agreement between the two methods indicates that the formation of 35S‐labeled, refractory organic matter is a minor process if it occurs at all. Our results suggest that both the aqua regia oxidation method and the chromium(II) reduction method, if used with care, are suitable for measuring incorporation of 35S into pyrite and elemental sulfur during 35SO42‒ reduction measurements in salt marsh sediments. Failure to explicitly measure the formation of 35S‐labeled pyrite can result in the rate of sulfate reduction being underestimated by 2‐fold to 10‐fold or more.
Are the phosphatases released by Daphnia magna components of its food?1
Authors: Boavida M. J. , Heath Robert T.
Published: April 2010

A laboratory culture of Daphnia magna was fed an axenic culture of Chlamydomonas acidophila. The predominant enzyme released by the zooplankter was a soluble alkaline phosphatase but it also released a smaller quantity of acid phosphatase. Five enzymes were released from the alga by the neutral detergent Triton X‐100: two alkaline phosphatases and three acid phosphatases. Alkaline and acid phosphatases from each organism differed in Michaelis constant (p‐nitrophenylphosphate as substrate), degree of inhibition by o‐phosphate, and anion exchange chromatographic behavior. We conclude that D. magna produces its own phosphatases, suggesting that it participates directly in the phosphorus regeneration mechanisms that aid the growth of its food resource.
Denitrification in a deep‐sea sediment core from the eastern equatorial Atlantic1
Authors: Sørensen Jan , Hydes David J. , Roger T. , Wilson S.
Published: April 2010

Shipboard measurements of denitrification were made in sediment from the eastern equatorial Atlantic using an acetylene inhibition technique. Undisturbed subcores were incubated for 1–9 days at 4°C in a N2:C2H2 atmosphere (9:1 mixture by volume, 1 atm) and denitrification rates were determined from the observed accumulation of N2O. In contrast to the predictions of several recent diagenetic models, no denitrification activity was observed in the region directly beneath the nitrate maximum. However, activity was concentrated lower in the sediment at a depth coincident with an organic‐rich layer.