bluuebunny/crossref_metadata_2025 huggingface dataset:
Symbiotic photosynthesis in a planktonic foraminiferan, Globigerinoides sacculifer (Brady), studied with microelectrodes1
Authors: Jørgensen Bo Barker , Erez Jonathan , Revsbech Peter , Cohen Yehuda
Published: April 2010

The chemical environment and the symbiotic photosynthesis of the spinose foraminiferan, Globigerinoides sacculifer, from the Gulf of Aqaba, northern Red Sea, were studied with O2 and pH microelectrodes at a resolution of 50–100 µm. In the dark, the foraminiferan respiration lowered the O2 concentration at the shell surface to 50% of air saturation, while pH was lowered from the ambient value of 8.23 to 8.15. In the light, the O2 increased to 2.5 times air saturation while pH reached 8.62. These steep chemical gradients were established over a diffusive boundary layer between the spines, which partly separated the animal from the bulk seawater. The O2 pool around the shell was very dynamic, with residence times down to 5 s in the light. Photosynthetic rates were mapped around and within the animal. The compensation light intensity of the symbiont‐host system was 26–30 µEinst m−2 s−1, while the light saturation intensity, Ik, was 160–170 µEinst m−2 s−1. The action spectrum of symbiont photosynthesis showed peaks at 450 and 670 nm due to chlorophyll a as well as a broad peridinin peak at 500–550 nm. Total respiration of one symbiont‐host system was 3.0 nmol O2 h−1 and was not significantly different between dark and light. Gross photosynthesis at light saturation was 18.1 nmol O2 h−1 per foraminiferan. The high net photosynthesis showed that the zooxanthellae could theoretically provide all organic carbon required for growth and respiration of the host. Model calculations indicated, however, that the foraminifera were diffusion‐limited in the uptake of dissolved nitrogen and phosphorus. The capture of prey was therefore a necessary source of these nutrients, while symbiotic photosynthesis could cover the energy requirements and allow efficient internal recycling of nutrients.
Grazing, respiration, excretion, and growth rates of tintinnids1
Authors: Verity Peter G.
Published: April 2010

Clearance, ingestion, and growth rates of two coastal tintinnid ciliates were measured in batch culture as a function of temperature and phytoplankton concentration. Oxygen consumption and ammonium excretion rates were determined at food concentrations which supported maximum growth rates at each temperature. Clearance, ingestion, respiration, excretion, and growth rates of both species increased with temperature. Clearing rates declined with increasing phytoplankton abundance. Ingestion and growth rates increased asymptotically with phytoplankton abundance and declined at high food concentrations. Gross growth efficiency was highest at phytoplankton concentrations which supported maximum growth rates. Over a range of temperatures, respiration and excretion were linearly related and exhibited significant linear relationships with ingestion and curvilinear relationships with growth. O : N ratios were 4–7, assuming an RQ of 1.0. The metabolic data were combined with previous measurements of in situ production by tintinnids to estimate their potential carbon requirements and NH4+ regeneration in Narragansett Bay, Rhode Island. Tintinnids ingested a carbon equivalent of 16–26% of the total annual net primary production and 32–52% of <10‐µm nanoplankton production. Nitrogen excretion was sufficient to support 11–18% of net primary production.
Discrimination between types of pigments in marine Synechococcus spp. by scanning spectroscopy, epifluorescence microscopy, and flow cytometry1
Authors: Wood A. Michelle , Horan P. K. , Muirhead K. , Phinney D. A. , Yentsch C. M. , Waterbury J. B.
Published: April 2010

The in vivo spectral properties of nine clonal isolates of marine Synechococcus spp. were compared to identify characteristics associated with intact cells from each of three major pigment groups. In vivo absorption and fluorescence excitation and emission spectra could differentiate between phycoerythrin (PE)‐lacking clones, clones containing a PE composed of phycoerythrobilin and phycourobilin chromophores, and clones containing a PE composed of only phycoerythrobilin chromophores. These differences can be detected analytically by both epifluorescence microscopy and flow cytometry and were observed in clones grown in different environments and at different stages of growth and nutrient limitation. These spectral characters thus reflect intrinsic differences between the three pigment groups and can be used to identify genetically distinct subpopulations of marine Synechococcus spp. in natural waters.
Nitrogen uptake by size‐fractionated phytoplankton populations in Antarctic surface waters1
Authors: Probyn T. A. , Painting S. J.
Published: April 2010

Nitogen uptake experiments in surface waters off the coast between Cape Ann and Mawson indicate that reduced nitrogen (ammonium and urea) supplied an average of 58% of phytoplankton requirements. Size‐fractionation studies provided evidence for nitrogen resource partitioning between the algae of different size classes at three of the five stations. On average, regenerated production amounted to 62% for the nanoplankton and 75% for the picoplankton.
Analytic models of NH4+ uptake and regeneration experiments1
Authors: Laws Edward A.
Published: April 2010

Differential equations describing the uptake and regeneration of NH4+ in both laboratory and field experiments are shown to have analytic solutions which can easily be inverted to determine the rate constants of interest. The solutions are used to study the descriptive ability of two fundamentally different models of NH4+ cycling, one in which NH4+ regeneration is regarded as a process that transfers N from particulate N to NH4+, the other in which regeneration is regarded as a process that introduces NH4+ to the dissolved phase without removing N from the particulate phase. The former model was found to give a good description of experimental field data and reasonable parameter values in all cases studied. The latter model was much less successful in describing the data and in producing reasonable parameter values. It is concluded that transfer of nitrogen from particulate N to NH4+ is a process which must be taken into account in analyzing NH4+ uptake and regeneration experiments.
Construction and validation of a body‐length‐based model for the prediction of cladoceran community filtering rates
Authors: Knoechel Roy , Blair Holtby L.
Published: April 2010

The in situ filtering rates of individual crustacean zooplankton were determined with radioactively labeled yeast cells. In six cladoceran species (Bosmina longirostris, Ceriodaphnia lacustris, Chydorus sphaericus, Daphnia galeata, Daphnia pulex, and Eubosmina coregoni), 93% of the variation in filtering rate could be explained as a power function of body length, completely disregarding species identity, temperature, and time of day. Community filtering rates for individual depths and for the entire water column were calculated from the regression model using body length and abundance estimates derived from various collection devices. Sampling variability contributed a greater proportion of the error in community grazing rate than did error in estimates of individual filtering rates. The model produced accurate predictions for the original study lake and for a nearby lake and also accurately simulated community grazing observations from the literature. The 95% confidence interval around the mean water column clearing rate was about 10–15% d−1 for clearing rates between 10 and 200% d−1. It is proposed that the model be utilized to study and evaluate the trophic interactions between the zooplankton, phytoplankton, and bacterioplankton communities.
Recent shifts in Daphnia community structure in southeastern Lake Michigan: A comparison of the inshore and offshore regions1,2
Authors: Evans Marlene S. , Jude David J.
Published: April 2010

Before 1982, Daphnia retrocurva and Daphnia galeata mendotae were the dominant species of Daphnia in Lake Michigan. Between 1972 and 1981, Daphnia community structure in the offshore region shifted toward greater dominance of the larger D. galeata mendotae, with Daphnia pulicaria, another large species, dominating by 1982. This continued through summer 1984. Shifts in offshore Daphnia community structure appear to be related to a reduction in predation pressure by declining alewife (Alosa pseudoharengus) populations and a hypothesized increase in relative predation pressure by Mysis relicta. From 1972 to 1984, Daphnia community structure changed only slightly in the inshore region; D. retrocurva generally remained the summer and autumn dominant. However, summer Daphnia abundances decreased after 1980 as yellow perch (Perca flavescens) and bloater (Coregonus hoyi) increased. From an examination of historic data we conclude that inshore region Daphnia populations probably have changed little since the late 1880s. The 1982–1984 offshore Daphnia complex, however, differed markedly from the earliest (mid‐1950s) record of zooplankton community structure in this region of southeastern Lake Michigan.
The dominant processes of sediment distribution and focusing in a small, eutrophic, monomictic lake
Authors: Hilton J. , Lishman J. P. , Allen P. V.
Published: April 2010

There is evidence for 10 mechanisms of sediment distribution in small lakes. The sediment accumulation rates measured from a common horizon in cores from 64 sites on Esthwaite Water, U.K., were used to determine the relative importance of these mechanisms on the distribution of sediment in the lake.

River inflows generally produced localized effects but there were indications of periodic turbidity flows to the deepest point of the lake from the major inflow. Active sediment focusing processes were the dominant distribution mechanisms, a major resuspension of sediment at autumn overturn probably being the most important. The remaining variance was much greater than observed in similar work elsewhere, suggesting that redistribution of sediment by direct and indirect wave action may be taking place all over the lakebed during isothermal periods. The relative contributions of the different processes were corroborated by analysis of previously published sediment trap data.
Recruitment of individuals into the plankton: The importance of bioturbation1
Authors: Marcus Nancy H. , Schmidt‐Gengenbach Jutta
Published: April 2010

The eggs of many planktonic copepods sink to the bottom in coastal waters and become buried beneath several centimeters of sediment where they cannot hatch. Bioturbation by three polychaetes, Nephtys incisa, Cistenides gouldii, and Clymenella torquata, promoted the burial of diapause eggs of the planktonic copepod Labidocera aestiva in a laboratory study. More important feeding by the two conveyor‐belt‐feeding species, C. gouldii and C. torquata, promoted the return of buried eggs to the water and water‐sediment interface. The viability of the eggs was unaffected by the translocation process and in these new positions eggs were able to hatch. We suggest that in the field bioturbation directly influences the recruitment of individuals into planktonic populations.
Optimal allocation of effort in studies using the size‐frequency method of estimating secondary production
Authors: Heisey Dennis M. , Hoenig John M.
Published: April 2010

Secondary production estimates based on the size‐frequency method can be improved through the use of optimal sample allocation without increasing the total sampling effort. We advocate a two‐step procedure. First, sampling dates should be chosen to minimize bias. Then, sample sizes on each date should be allocated in such a way as to minimize variance. Calculating the optimal sample allocation requires some prior variance information, but even rather imperfect information will usually result in improved estimates. An example is presented using published data on the mayfly Ephemerella dorothea.
The effects and implication of tides and rainfall on the circulation of water within salt marsh sediments1
Authors: Carr Alan P. , Blackley Michael W. L.
Published: April 2010

The response of the water table of an intertidal salt marsh in NW England has been investigated. During neap tides, water seeps upward from the underlying sand‐silt‐clay interface. This effect continues as the marsh is overtopped during spring tides but is then dwarfed by penetration of water downward from the surface.

Under “typical conditions” the delay between high water in the river and maximum apparent water level for the marsh becomes less as the spring‐tide cycle maximum is approached. Lags also appear smaller during summer, probably mainly due to desiccation cracks. Precipitation effects are only important when rainfall is significant in quantity and coincides with low water during neap tides.
1
Authors: Revsbech Niels Peter , Madsen Bent , Jørgensen Barker
Published: April 2010

Microprofiles of oxygen and oxygenic photosynthesis were measured in a photosynthetically active sediment by an oxygen microelectrode. The diffusion coefficient of oxygen in the uppermost 1 mm of the sediment was determined in poisoned sediment by microelectrode measurement of changes in the oxygen profile during nonsteady state conditions. The experimentally obtained data were inserted into computer models to calculate the vertical profile of the oxygen consumption rate. The calculations showed that the rate of oxygen consumption was highest at the oxic‐anoxic boundary where sulfide was oxidized and in the lowest part of the photic zone. Computer models were also used to obtain more accurate profiles of oxygen production. The oxygen profiles calculated by the computer were very close to those obtained experimentally both during the steady state developed under light and during the transient conditions developed at the onset of darkness.
Bacterial utilization of total in situ dissolved carbohydrate in offshore waters1
Authors: Burney Curtis M.
Published: April 2010

Total dissolved carbohydrate declined steadily at rates of 1.5 and 2.6 µg C liter−1 h−1 during 12–24‐h dark in situ incubations in the Sargasso Sea and Gulf of Maine, indicating rapid bacterial metabolism. The source of this carbohydrate appears to be the extracellular release of phytoplankton photosynthate fixed during the most recent photoperiod. Observed rates require substantially greater primary production than indicated by the 14C method.
Modeling the diurnal mixed layer
Authors: Spigel Robert H. , Imberger Jorg , Rayner Kenneth N.
Published: April 2010

The numerical model presented here is based on the one‐dimensional equations for momentum,
heat, salt, and turbulent kinetic energy integrated over the diurnal mixed layer. Two noteworthy
features are the inclusion of the energetics of billowing due to Kelvin‐Helmholtz instability at the
base of the mixed layer, and a closure hypothesis which retains average mixed‐layer turbulent
kinetic energy as an explicit variable, rather than assuming it to be a fixed proportion of external
energy input. The importance of both these features is illustrated in the application of the model
to the data for 1 day which included several mixing processes: a fairly calm morning with uninterrupted
solar heating, followed by rapid mixed‐layer deepening during a strong afternoon sea
breeze, and finally a relatively cool night with little wind. The data contain rapidly changing
meteorological inputs as well as evidence of strong billow formation and collapse and thus provide
an ideal test of the importance of both billow energetics and the temporal effects in the turbulent
kinetic energy budget. The model does not account for processes occurring below the mixed layer
nor for the effects of horizontal advection. Within these constraints, model results agree well with
measured temperatures and represent an improvement over the results of a slab model without
billow energetics.
Dilution of 210Pb by organic sedimentation in lakes of different trophic states, and application to studies of sediment‐water interactions1
Authors: Binford Michael W. , Brenner Mark
Published: April 2010

Lake sediments reflect conditions in the water column and can be used for rapid, integrative measurements of limnological variables. Examination of 210Pb‐dated cores from 12 Florida lakes of widely differing trophic state (expressed as Carlson’s trophic state index: TSI) shows that net accumulation rate of organic matter is related to primary productivity in the water column. In 26 other lakes the activity of unsupported 210Pb g−1 organic matter in surficial sediments is inversely related to trophic state and, therefore, to organic accumulation rate. From this observation we develop a new method that uses fallout 210Pb as a dilution tracer to calculate net sedimentary accumulation rates of any material in surface mud. We demonstrate strong relationships between net loss rates of biologically important materials (C, N, P, and pigments) and their respective water concentrations (expressed as TSI). Multiple regression models incorporating net sediment accumulation rates of all four variables explain up to 70% of the lake‐to‐lake variation of TSI. The 210Pb‐dilution method has applications for studies of material cycling, paleolimnology, and sediment accumulation processes.
Organic carbon in the Caura River, Venezuela1
Authors: Lewis William M. , Saunders James F. , Levine Suzanne N. , Weibezahn Franz H.
Published: April 2010

Samples were taken weekly over a 2‐year period near the mouth of the Caura River, which drains a large watershed on Precambrian shield covered with tropical moist forest. The concentrations of dissolved organic carbon were essentially static despite a 10‐fold seasonal change in discharge. Particulate carbon showed an unexpected but relatively weak inverse relationship to discharge. Yield of total organic carbon (12.3 g C m−2 yr−1) was higher than would have been expected from the literature. Yield can be predicted accurately from discharge because of the strong homeostasis in concentration of dissolved organic carbon.
A method for determining enzymatically hydrolyzable phosphate (EHP) in natural waters1
Authors: Chrost Ryszard J. , Siuda Waldemar , Albrecht Dieter , Overbeck Jurgen
Published: April 2010

A method for determining enzymatically hydrolyzable phosphate (EHP) in natural waters is described, based on the determination of released inorganic phosphate after the hydrolysis of organophosphoric esters by free, dissolved phosphohydrolases (mainly phosphatase) produced by the biota. The method gives higher values in highly eutrophic waters than the classical procedure of Strickland and Parsons; in samples from less eutrophic habitats the two methods give similar results. The new method is simple, accurate, and can be used in both freshwater and marine studies. It is particularly recommended for determination in hypereutrophic waters, when Pi concentrations exceed 25 µg P liter−1. Representative field data from the euphotic zone of seven lakes and two marine habitats are presented.
The use of 15N to measure nitrogen uptake in eutrophic oceans; experimental considerations1,2
Authors: Dugdale R. C. , Wilkerson F. P.
Published: April 2010

The use of 15N to measure the flux of nitrogen compounds has become increasingly popular as the techniques and instrumentation for stable isotope analysis have become more widely available. Questions concerning equations for calculating uptake, effect of isotope dilution (in the case of ammonium), duration of incubation, and relationship between disappearance of a nitrogen compound and the 15N uptake measurement have arisen, especially for the research conducted in oligotrophic regions. Fewer problems seem to have occurred in eutrophic areas. However, sufficient literature now exists to allow some generally accepted experimental procedures for 15N studies in eutrophic regions to be laid down.

Incubation periods of 2–6 h appear to avoid problems related to isotope dilution and to overcome the bias introduced in some cases by initial high rate or surge uptake. During such incubation periods, assimilation is measured rather than uptake or transport into the cell. Incorporation of 15N into the particulate fraction is usually linear with time over the periods currently used. The 15N method provides a better estimate of incorporation into phytoplankton than 14N disappearance, but a small fraction appears to be lost. Although most workers suggest the loss to be a result of dissolved organic nitrogen production, direct evidence is lacking.

If the considerations discussed here are applied with the 15N techniques currently available, reliable estimates of phytoplankton nitrogen flux in eutrophic areas can be obtained.
Bioluminescence displays induced by pulsed light
Authors: Lapota David , Losee Jon R. , Geiger Mark L.
Published: April 2010

Unusual displays of bioluminescence apparently stimulated by pulsed light from a handheld flashlight were observed from the surface in an ice pond in the Beaufort Sea and from a submersible at a depth of 600 m 64 km off the east coast of Florida.
Diel epibenthic activity of mayfly nymphs, and its nonconcordance with behavioral drift1
Authors: Allan J. D. , Flecker A. S. , McClintock N. L.
Published: April 2010

Diel changes in the numbers and activity of mayfly (Ephemeroptera) nymphs on the substrate surface in a stony‐bottom stream were determined by direct observations, to investigate the relationship between benthic activity and drift. Individuals were viewed through a glass box (0.1 m2 area) at 2‐h intervals for 24 h; dim red light was used during darkness. Baetis was relatively unaffected by the presence of the observer, whereas Cinygmula was very easily disturbed. The number of individuals in view, activity per individual, and total activity all were greatest by day and least during the night for both species. Each of these measures was significantly correlated with temperature, which varied 6°–8°C over the diel cycle. Drift activity, in contrast, was strongly nocturnal and generally peaked immediately after nightfall. Because of the clear lack of correspondence between drift and the activity of mayfly nymphs on stone tops, behavioral drift in this system cannot be explained as the passive consequence of foraging.
Horizontal sedimentation differences in a eutrophic Swiss lake
Authors: Bloesch Jurg , Uehlinger Urs
Published: April 2010

Settling fluxes measured by means of sediment traps were 887 g dry wt m−2 yr−1, 113 g POC m−2 yr−1, and 2.6 g PP m−2 yr−1 in 1982–1983 at a central station in eutrophic Lake Hallwil, Switzerland. Nearshore settling rates were higher by a factor of 1.4–3.4. Since particulate organic carbon (POC), particulate phosphorus (PP), and biomass concentration in the lake water showed vertical rather than horizontal differences, this result was attributed to permanent bottom sediment resuspension and redeposition in the littoral zone. Horizontal sediment transport (sediment focusing) and sediment resuspension in the profundal zone in winter, when wind and turbulence are increased, accounted for only about 20% of the sedimentation rates. Because 70–80% of the total sedimentation for the year occurred during summer, such processes are of minor importance in Lake Hallwil, although a “nepheloid” layer with increased POC and PP concentrations 5–8 m above the bottom was present. It is stressed that the mechanisms of sediment transport must be known to permit interpretation of trap results and to understand lake metabolism.
Measurement of the lipid ovary index on stored zooplankton samples1
Authors: Bjorkman Bjorn , Shapiro Joseph
Published: April 2010

Use of lipophilic dyes allows evaluation of the lipid‐ovary index in Formalin‐preserved zooplankton samples for as long as 6 months, in contrast to the 48‐h period possible without dyeing.
The storage of reactive silicate samples by freezing
Authors: Macdonald R. W. , McLaughlin F. A. , Wong C. S.
Published: April 2010

Improper attention to thawing can result in severe negative and variable bias in seawater determination for silicate when samples have been stored by freezing. To control bias requires an adjustment of the length of time between thawing the sample and analyzing it, depending on salinity, silicate concentration, and length of time frozen. Figures are given which allow the optimum selection of thaw time.
Productivity in upwelling areas deduced from hydrographic and chemical fields1
Authors: Minas Hans Joachim , Minas Monique , Packard Theodore Train
Published: April 2010

A combination of Broenkow’s nutrient oxygen model and Bowden’s residence time evaluation of upwelled waters enabled us to calculate the “net community production” (NCP) in coastal upwelling areas (NW Africa, SW Africa, Peru) and in an open upwelling (Costa Rica Dome). Since NCP represents mainly new production in terms of phosphorus or nitrogen, and since it derives from integrated nutrient consumption over the main production area, a good picture of the average fertility of these zones is obtained. In terms of carbon, NCP averaged 0.6 g C m−2 d−1 off Peru, 1.1 off SW Africa, and 2.3 off NW Africa. However, production budget per kilometer of coastline is greater for both Peru and SW Africa than it is for NW Africa. The lower activities off Peru and off SW Africa correspond to a relatively high nutrient‐low chlorophyll (HNLC) situation, characterized by a slowly growing phytoplankton standing stock. Such HNLC situations are greatly pronounced in the Costa Rica Dome, with NCP values as low as 0.14g C m−2 d−1. Herbivorous grazing in the freshly upwelled source water appears to be the most plausible explanation for the low chlorophyll. This mechanism for cropping phytoplankton and retarding nutrient uptake provides a way to spread nutrient input to the open ocean. It also explains the prevalence of oxygen undersaturation (and CO2 oversaturation) in the surface waters of the equatorial upwelling. By using the NW African data and NCP and ammonium excretion rates from the literature we could calculate an Eppley f factor (ρNO3− : ρNO3− + ρNH4+) of 0.64.
Biological fixation of atmospheric nitrogen in the Mediterranean Sea
Authors: Béthoux J. Pierre , Copin‐Montégut Gérard
Published: April 2010

Nutrient concentration in the Mediterranean Sea is controlled by water exchanges through the Strait of Gibraltar and by atmospheric and terrestrial inputs. Various peculiarities in the nitrogen and phosphorus geochemical cycles are pointed out, namely a low N: P atomic ratio (6.4) in terrestrial discharges, and a budget well balanced for phosphorus (where terrestrial discharges amount to about 80% of the outflow) but apparently very deficient in nitrogen, despite a high N: P atomic ratio (22), in Mediterranean deep waters. This suggests the possibility of a surprisingly high rate of direct atmospheric N uptake by the Mediterranean ecosystem (possibly seagrasses Posidonia oceanica and pelagic bacterioplankton species).
Accumulation of Th, Pb, U, and Ra in marine phytoplankton and its geochemical significance1
Authors: Fisher N. S. , Teyssié J.‐L. , Krishnaswami S. , Baskaran M.
Published: April 2010

The bioaccumulation of U, Th, Ra, and Pb in four diverse nanoplanktonic algal species and a picoplanktonic blue‐green alga was determined with radiotracers. Among the nanoplankton, differences of 1–2 orders of magnitude in volume/volume concentration factors (VCFs) were observed for a given nuclide, but larger differences were observed among the four nuclides, with VCF values of Th > Pb > Ra ≃ U. The picoplankton cells, with greater surface: volume ratios, had significantly higher VCF values. The mean VCF values in the nanoplankton of Th and Pb were 1.5 × 105 and 3.6 × 104 in the light and 2.8 × 105 and 7.3 × 104 in the dark. The VCFs of Th and Pb in the picoplankton were both about 2 × 106, irrespective of light. Retention half‐times of 228Th and 210Pb in fecal pellets of Artemia salina, fed radiolabeled diatoms, were 20–50 d, but >120 d for 228Th at 4°C. The results suggest that sinking plankton and their debris could account for most of the natural series radionuclides sedimenting out of oceanic surface waters.
Simultaneous measurement of primary production by whole‐lake and bottle radiocarbon additions1
Authors: Bower Peter M. , Kelly Carol A. , Fee Everett J. , Shearer John A. , DeClercq Doug R. , Schindler David W.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Dissolved hydrogen, facultatively anaerobic, hydrogen‐producing bacteria, and potential hydrogen production rates in the western North Atlantic Ocean and Gulf of Mexico1,2
Authors: Schropp Steven J. , Scranton Mary I. , Schwarz John R.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Variations in the spectral values of specific absorption of phytoplankton
Authors: Sathyendranath Shubha , Lazzara Luigi , Prieur Louis
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Calculation of cell production of coastal marine bacteria based on measured incorporation of [3H]thymidine1,2
Authors: Riemann Bo , Bjørnsen Peter Koefoed , Newell Steven , Fallon Robert
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Thymidine incorporation and microbial respiration in the surface sediment of a hypereutrophic lake1
Authors: Bell Russell T. , Ahlgren Ingemar
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Temporal variations of phosphate and inorganic nitrogen compounds in central Baltic deep waters
Authors: Nehring Dietwart
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Measurement of net growth rates of herbivorous benthic animals using periphyton labeled simultaneously with 13C and 15N1
Authors: Otsuki A. , Seki H. , McAllister C. D. , Levings C. D.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Vertical eddy diffusivity determined with 222Rn in the benthic boundary layer of ice‐covered lakes1
Authors: Colman John A. , Armstrong David E.
Published: April 2010

Concentration gradients of 222Rn and 226Ra were analyzed in the benthic boundary of seven ice‐covered lakes to investigate vertical eddy diffusivity, Kz. Sediment‐free samples, retrieved with a tubing sampler from as close to the bottom as 14 cm, showed that sharp 222Rn gradients persist over the sediments. A three‐dimensional analytical mixing model indicated horizontal mixing would not supply significant amounts of 222Rn to midlake profiles in some flat‐bottomed lakes under ice cover. One‐dimensional analysis of the profiles permitted observation of change in Kz with height above the sediments. Computed Kz values usually decreased in a given lake toward the sediments. The range in Kz from all lakes studied was 0.30 cm2 s−1 at 3.61 m above the bottom to 3.2 × 10−4 cm2 s−1 at 0.23 m, both in Lake Mendota. The correlation between Kz and the buoyancy density, N2, was computed: K = 1.2 × 10−5 (N2)−0.63. This relationship indicates turbulence arising from shear flow influences the vertical mixing in the winter boundary layer. Retarded mixing in the profundal boundary layer restricts vertical solute transport in some ice‐covered lakes.
Short‐term changes in the biology of a warm‐core ring: Zooplankton biomass and grazing1
Authors: Cowles T. J. , Roman M. R. , Gauzens A. L. , Copley N. J.
Published: April 2010

Gale force winds in September 1981 deepened the mixed layer and introduced nutrients to the surface waters of Gulf Stream warm‐core ring 81D. Phytoplankton nitrate uptake rates, primary productivity, and chlorophyll a in the mixed layer of ring 81D increased after the mixing event. Microzooplankton biomass (64–333 µm) doubled after the storm, with the cyclopoid copepods having the largest numerical increase. Data on zooplankton biomass, numbers of naupliar and copepodite stages of copepods, zooplankton grazing rates inside the ring, and measurements of high egg production rates by ring copepod species suggest that enhanced phytoplankton production and biomass in ring 81D was utilized by the ring zooplankton. The data support the hypothesis that in situ processes dominate the biological dynamics of warm‐core rings. Our findings also indicate that oceanic zooplankton respond to physical events on relatively brief time scales (<10 d) and that such events may enhance secondary production.
Cladoceran juvenile growth1
Authors: Tessier Alan J. , Goulden Clyde E.
Published: April 2010

We examined juvenile growth of five species of Daphniidae raised at several food levels. For each species, an exponential model with a species‐specific exponent accurately described the weight gain of preadult instars. This finding indicates that weight‐specific net production within a species is constant throughout juvenile development; early and late instars are equal in exploitative ability.

Among clones born at different body weights, specific net production depended on food level. At high food levels, larger bodied animals displayed greater exploitative ability (larger exponents). However, as food level was lowered, specific net production of large‐bodied animals was depressed more severely than that of small‐bodied animals. At the lowest food level, smaller bodied animals exhibited greater exploitative ability.
A method for quantitative determination of volatile organic compounds in marine macroalgae1
Authors: Newman Kathleen A. , Gschwend Philip M.
Published: April 2010

Volatile organic compounds from macroalgae are collected by vacuum distillation and cryogenic trapping, transferred by closed‐loop stripping to Tenax‐GC traps, and thermally desorbed and analyzed by gas chromatography‐mass spectrometry. Nonpolar compounds exhibiting boiling points between 60° and 180°C are measured quantitatively with detection limits near 1 ng g−1 dry tissue. Several halogenated and sulfur‐containing volatiles, including some previously not detected in seawater in which the macroalgae were growing, are found in such tissue analyses.
Methane in surface waters of Oregon estuaries and rivers1
Authors: de Angelis Marie A. , Lilley Marvin D.
Published: April 2010

Methane concentrations in surface waters of Oregon rivers and estuaries were measured over a 4‐yr period. Geographic variations in riverine CH4 were observed. Results from undisturbed forest streams indicate that rivers can contain high natural levels of CH4 not attributable to pollution. Lateral diffusion and runoff from saturated forest and fertilized agricultural soils may be important in determining methane levels in rivers. Methane concentrations in well‐flushed estuaries appear to be controlled mainly by mixing between high CH4‐containing river water and low CH4‐containing seawater endmembers. Rivers and estuaries were found to be sources of methane to the atmosphere. Calculated daily fluxes to the atmosphere ranged from 1.2 to 71 mg CH4 m−2 for rivers and from 0.04 to 21 mg CH4 m−2 for estuarine samples.
Determination of phosphorus in natural water using hydride generation and gas chromatography1
Authors: Hashimoto Shinya , Fujiwara Kitao , Fuwa Keiichiro
Published: April 2010

A new hydride‐generation method was applied to the determination of phosphorus in seawater and pond water. A sample solution containing phosphate was mixed with a 6% sodium borohydride solution in a quartz vessel and dried under an incandescent light at 40°C for 2 h. Phosphine was reproducibly generated from phosphate by heating this vessel at 460°C. Total phosphorus and total dissolved phosphorus were determined by this method with small sample volume (about 100 µl) without any digestion procedure. Good agreement was found between the hydride‐generation method and ordinary colorimetry with sample digestion.
The potential contribution of primary production by red tides to the west Florida shelf ecosystem1
Authors: Vargo G. A. , Carder K. L. , Gregg W. , Shanley E. , Heil C. , Steidinger K. A. , Haddad K. D.
Published: April 2010

Production rates and the potential annual carbon input for blooms of the red‐tide dinoflagellate, Ptychodiscus brevis, on the west Florida shelf were estimated from field and laboratory measurements, a published value, and Coastal Zone Color Scanner (CZCS) imagery. Daily production rates during blooms based on measured and calculated values ranged from 0.8 to 3.8 g C m−2 d−1 and were 2–5 times higher than literature values or rates measured during nonbloom periods. Total production for blooms which ranged in size from 5.2 to 12.4 × 103 km2 was calculated as 2.9–7.1 × 105 t C month−1. Annual production (12 months) during nonbloom periods could have a range of 30–150 g C m−2 which yields an annual range of 6.9–35.2 × 105 t C yr−1 within a shelf area of 2.33 × 104 km2. Blooms dominated by P. brevis can therefore contribute a significant fraction of the annual production of the water column on the central west Florida shelf.
Microbial biomass and respiratory activity in the surface waters of the east Banda Sea and northwest Arafura Sea (Indonesia) at the time of the southeast monsoon
Authors: Vosjan J. H. , Nieuwland G.
Published: April 2010

In August 1984, in the eastern part of the Banda Sea and the western Arafura Sea, we measured biomass as ATP and respiration as ETS activity of organisms <50 µm. Biomass integrated over the upper 300 m of the water column ranged from 1.4 to 4.4 g C m−2 and the respiratory rate, calculated to real respiration at in situ temperatures, ranged from 1 to 4.2 g C m−2 d−1. In the water column, maximal biomass and respiration were found at depths <50 m. The horizontal distribution of biomass and respiration showed highest values in the northeast portion of the study area, south of Irian Java. The respiration: biomass ratio (R : B) lies between 0.5 and 1.7 d−1, implying a rapid turnover of organic matter.
The effect of food limitation on vertical migration in Daphnia longispina1
Authors: Johnsen Geir Helge , Jakobsen Per Johan
Published: April 2010

Diel vertical migration of a natural population of Daphnia longispina was investigated experimentally in enclosures twice in 1985. The amount of available food was manipulated and vertical distributions were recorded at times of low (night) and high (day) risk of predation from fish. In the first experiment, the large D. longispina displayed diel migrations. When food was depleted experimentally, however, the large animals were near the surface during both day and night. In the second experiment, large D. longispina first began to migrate after being provided with ingestion‐rate‐saturating concentrations of food. Vertical migrations in D. longispina seemed to reflect a trade off between two conflicting interests: avoiding predation and risking starvation. This trade off was balanced by the overall amount of available food, restricting migrations of the large animals when food was scarce.
The feeding condition of Calanus pacificus and other zooplankton in relation to phytoplankton pigments in the California Current
Authors: Håkanson John L.
Published: April 2010

Calanus pacificus copepodite V stages were taken from 40 stations in the California Current between Los Angeles and San Francisco in April 1984. Wax ester and triglyceride contents of the copepods were determined as indices of their feeding condition. The regions with high Chl a concentrations had copepods with high lipid contents and dry weights, while the low Chl a region farther offshore had copepods with low lipid levels and dry weights. The Southern California Bight generally had intermediate to low Chl a concentrations, which was also reflected in the copepod parameters.

Wax ester content and dry weight of Calanus had higher correlations with primary production (r = 0.86; r = 0.89) than with total integrated Chl a (r = 0.65; r = 0.55). Lipid content of field‐caught copepods was much higher than that of laboratory animals reared at a high concentration of food.

Additional species were taken in a subarea south of Point Conception. Lipid content of the grazing copepod Rhincalanus nasutus was also significantly related to pigment concentration and showed good concordance with Calanus. Lipid contents of furcilia stages of Euphausia pacifica and chaetognaths, on the other hand, were not significantly correlated with the pigment concentrations or the lipid contents and dry weights of the copepods.
In situ culturing as a test of the larval starvation hypothesis for the crown‐of‐thoms starfish, Acanthaster planci1
Authors: Olson Richard Randolph
Published: April 2010

As a test of the hypothesis that larvae of the crown‐of‐thorns starfish, Acanthaster planci, are severely food limited, larvae were reared in situ in natural seawater and in natural seawater enriched with cultured phytoplankton. Although phytoplankton levels remained below the minimum threshold needed to support A. planci larval development in the laboratory (0.4 µg Chl a liter−1), there was no evidence of starvation. Larvae began settling at 14 d after fertilization, which is 2 d sooner than the shortest time to settlement reported for A. planci from laboratory rearing. Enrichment of diet resulted in no significant difference in survivorship (compared to larvae feeding only on natural seawater) and only a slight difference in development rate. These data, along with other indirect evidence, suggest that A. planci larvae develop at near‐maximal rates under normal conditions (i.e. in the absence of phytoplankton blooms) and that fluctuations in larval food resources may be of little importance in explaining interannual variation in their larval recruitment.
On the radiative transfer in the sea, including fluorescence and stratification effects
Authors: Dirks R. W. J. , Spitzer D.
Published: April 2010

A general two‐flow (sunlight and fluorescence emission) radiative transfer model in the sea is developed. It treats radiation sources (fluorescence) and particle stratification within the water column. With a given set of input parameters, model computations are performed and compared to measured data. Both experiments and computations reveal substantial depth dependence of irradiance reflectance and attenuation functions in the chlorophyll fluorescence wavelength region, even in the case of homogeneous particle distributions with low concentrations.
Electrophoretic mobility of natural particles and cultured organisms in freshwaters1
Authors: Gerritsen Jeroen , Bradley Susan W.
Published: April 2010

Electrophoretic mobility (EM) was measured on natural particles from 11 southeastern U.S. lakes and streams. The mobility decreased with increased conductivity, increased with dissolved organic carbon (DOC), and increased with pH. EM was further measured in each water sample with pH adjusted over the pH range 3–10. In general, mobility increased with pH, but particles in hard waters were only slightly affected, while particles in soft waters with high DOC showed a sharper rise in EM due to increase of pH. The experiments were repeated with the cyanobacterium Microcystis aeruginosa, the green alga Chlorella vulgaris, and the bacterium Klebsiella sp. in filtered water from several of the sites. Cultured cells showed greater homeostasis of EM in the pH gradient than the natural particles, but cells in soft water with high DOC had greater mobility than those in hard water. The three species differed in their mobility: Microcystis consistently had the highest EM and Chlorella the lowest; Chlorella was neutral in the hard waters. Klebsiella was intermediate in EM. The results indicate that individual habitats and particle species may represent different challenges to filter feeders, based on particle surface chemistry.
The relationship between chemically analyzed phosphorus fractions and bioavailable phosphorus1
Authors: Bradford Marie E. , Peters Robert Henry
Published: April 2010

To identify available phosphorus, phosphorus was measured by 2‐week bioassay in water from 39 sites in Ontario and Québec and regressed against total phosphorus and the phosphorus (P) in 11 analytically measured fractions (total soluble, total reactive, particulate, and soluble reactive P, both before and after autoclaving; and soluble reactive P after exposure to enzymes, to UV radiation, and to both). Covariance analysis showed that low‐P (<30 µg TP liter−1) lakes and rivers, P‐rich lakes, and P‐rich rivers required separate analysis. Total P was a consistently poor correlate of available P (r2 = 0.44–0.72). A best estimator for various subsets of the data was identified in terms of descriptive power (r2, F), normality, and analytical ease. At low concentrations of P, the fraction of choice is total reactive phosphorus, which explained 73% of the total variation in bioassay P. Total soluble phosphorus was the most useful correlate of bioassay P in eutrophic lakes (r2 = 0.98) and rivers (r2 = 0.95). The applicability of these regressions to waters other than those sampled or as predictors of lake eutrophication remains to be evaluated.
Measurements of groundwater seepage flux onto a coral reef: Spatial and temporal variations
Authors: Lewis John B.
Published: April 2010

Rates of groundwater discharge onto coral reefs at Barbados, West Indies, were measured with seepage meters and miniature piezometers. Seepage flux varied spatially, was correlated with water depth, and was about twice as high during the wet season as during the dry. Groundwater nitrogen concentrations were correlated with salinity but phosphate concentrations were not. Nitrate content of the discharge was much higher than was phosphate content. Measured fluxes were consistent with groundwater discharge estimates from aquifer models, but a large data set would be required to make accurate predictions of areal groundwater discharge and nutrient loading.
Seasonal and longitudinal variations in apparent deposition rates within an Arkansas reservoir1
Authors: James William F. , Kennedy Robert H. , Montgomery Robert H. , Nix Joe
Published: April 2010

Seasonal and spatial differences in apparent sediment trapping rates were related to the establishment of longitudinal gradients in water quality at DeGray Lake, Arkansas. Gradients in turbidity developed during winter and spring due to high suspended loads, which settled primarily in the headwater region. Gradients in apparent deposition of allochthonous organic carbon and chlorophyll a also influenced detrital processing and hypolimnetic dissolved oxygen conditions. Hypolimnetic dissolved oxygen depletion started in May in the headwater region, due to a high volumetric dissolved oxygen demand, and spread slowly to the dam by winter. These patterns indicated that riverine inputs and deposition influenced biological activity along the longitudinal axis of the lake.