bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the activity of epiphytic bacteria of Elodea canadensis and Chara vulgaris following treatment with the herbicide, paraquat1
Authors: Fry John C. , Ramsay Angela J.
Published: March 2010

The heterotrophic activity of the bacterial epiphytes of Elodea canadensis and Chara vulgaris was studied by measuring the mineralization of 14C‐glucose in situ. In a field experiment in which the plants were treated with the herbicide, paraquat, there was an increase in both Vmax and K +Sn of the epiphytic bacteria of Elodea and turnover time remained fairly constant. The epiphytic bacteria of Chara, which was resistant to paraquat, did not show any appreciable change in these parameters.

The values for the mean Vmax per bacterium calculated from acridine orange counts, viable counts, and autoradiographic counts of bacteria labeled with 3H‐glucose showed greater increases after herbicide treatment for Elodea than for Chara.
Aquatic metabolism of the communities associated with attached dead shoots of salt marsh plants1
Authors: Gallagher John L. , Pfeiffer William J.
Published: March 2010

Rates of respiration of the community associated with the attached dead shoots of Spartina alterniflora and Juncus roemerianus were highest during the warmer season except in midsummer when rates dropped. The rates for the Spartina community. were about twice those for Juncus. Within the S. alterniflora “dead plant community” high respiration rates were associated with low net DOC release rates.
Diurnal fluctuations of O2, N2, and CH4 in the rhizosphere of Thalassia testudinum1
Authors: Oremland Ronald S. , Taylor Barrie F.
Published: March 2010

Gas bubbles in the sediments and gases in the internal spaces of the rhizomes of T. testudinum contained O2, N2, and CH4. CH4 was a minor component. The percentage composition of the major components, O2 and N2, varied from 2.3% O2 + 94% N2 (sediment bubbles, early morning) to 30% O2 + 69% N2 (rhizome gases, midafternoon). The variations probably reflected changes in O2 content of the gases caused by diurnal variations in photosynthetic and oxidative activities of the seagrasses and sediments. Apparently there is a net transfer of O2 from T. testudinum, via its rhizome system, to the sediments.
A method for obtaining more precise measures of excreted organic carbon1
Authors: McKinley Kelton R. , Ward Amelia K. , Wetzel Robert G.
Published: March 2010

A new method for concentrating and measuring excreted organic carbon by lyophilization and scintillation counting is efficient, improves measurable radioactivity, and increases precision for estimates of organic carbon excreted by phytoplankton and macrophytes.
Dissolved organic carbon: Spectral relationships in coastal waters1
Authors: Wheeler John R.
Published: March 2010

Caution should be observed in using photometry to estimate concentrations of dissolved organic carbon in coastal waters, even within very limited geographical regions.
Geothermal gradients in British lake sediments
Authors: Pugh D. T.
Published: March 2010

Temperatures have been measured in the water and sediments of Loch Ness and Windermere to investigate the possibility of determining the geothermal heat flow through the bottom of deep British lakes. The accuracy is limited by corrections for annual and long term variations in bottom water temperatures.

In Loch Ness (max depth 232 m) the annual temperature variation of the deep water is normally <0.5°C. There is evidence of a benthic water layer overlying the sediments in the deepest parts of the loch in which the annual variations are probably not more than 0.2°C. When corrections are made, the mean of 13 measurements of heat flow in Loch Ness is 1.45 µcal cm−2 s−1. Values increase steadily from 1.03 µcal cm−2 s−1 in the northeast to 1.74 in the southwest, with local high values near the Foyers granite intrusion.

Annual variations in bottom water temperature in Windermere (max depth 65 m) are >2.5°C, though variations in the benthic layer are less than this. Reliable geothermal heat flow measurements were only possible because an extended series of measurements was available. The mean of three acceptable results was 1.69 µcal cm−2 s−1.
Solar Lake (Sinai). 3. Bacterial distribution and production1
Authors: Cohen Yehuda , Krumbein Wolfgang E. , Shilo Moshe
Published: March 2010

The relations between photosynthetic and nonphotosynthetic (chemoorganotrophic and chemolithotrophic) microorganisms in Solar Lake were studied during the annual limnological cycle. Six different bacterial plates were observed during stratification by direct and viable bacterial counts, light and dark CO2 incorporation, chlorophyll a, protein, ATP, and ETS determinations. A maximal dark CO2 incorporation of 1,014 mg C m−3 d−1 may represent as much as 16,900 mg C m−3 d−1 of chemoorganotrophic bacterial production, on the assumption that these bacteria assimilate an average of 6% CO2 of their total carbon uptake. This calculated production is very high in comparison to the recorded photosynthetic maximum of 4,960 mg C m−3 d−1. The organic carbon needed for such a high chemoorganotrophic production may be supplied by the benthic cyanobacterial mats. Extremely high specific activities of ATP and ETS for the layer immediately above the thermocline indicate a very active bacterial plate at this layer.
Solar Lake (Sinai). 4. Stromatolitic cyanobacterial mats1
Authors: Krumbein Wolfgang E. , Cohen Yehuda , Shilo Moshe
Published: March 2010

Cyanobacterial mats of Solar Lake, studied in the field and by microscopic methods, are classified into four types: flat shallow‐water mat, pinnacle mat on the upper slope, cyanobacterial and other photosynthetic bacterial films on the lower slope, and flocculose mat at the bottom. The annual cycle and development of the four types are described. Measurements of photosynthesis by the flat shallow‐water mat in the field and the laboratory yielded an average value of 10 g C m−2 d−1. In the flocculose anaerobic bottom mat 5 g C m−2 d−1 was measured. Total accretion rates including organogenic material for the four mat types range between 5 and 50 cm 100 yr−1; aerobic and anaerobic degradation of the organic production of the shallow‐water mat remineralizes more than 99% of the biomass. In the deeper parts of the mat, organic matter is transformed into carbonates. The role of bacteria in this process is demonstrated by ultramorphological analyses and by comparison to laboratory experiments with bacterial isolates.
Solar Lake (Sinai). 5. The sulfur cycle of the bcnthic cyanobacterial mats1
Authors: Jørgensen Bo Barker , Cohen Yehuda
Published: March 2010

The littoral sediments of Solar Lake (Sinai) consist of cyanobacterial mats up to 1 m thick. The vertical distributions in these mats of sulfur compounds, organic carbon, carbonate, and of sulfate‐reducing and other anaerobic, heterotrophic bacteria are presented. The in situ rate of sulfate reduction, measured with a radiotracer technique, decreased 10,000‐fold from 5,400 nmol SO42‐ cm−3 d−1 at the surface to <1 at the bottom of the mats. Turnover rates of inorganic sulfur compounds and of organic matter were estimated. A high influx down into the cyanobacterial mats of dissolved organic compounds produced by the epibenthic algae and bacteria could be deduced from the anaerobic respiration rates. A quantitative flow diagram of the sedimentary sulfur and carbon cycle is presented.
Biogenic meromixis and stability in a soft‐water lake1
Authors: Culver David A.
Published: March 2010

Hall Lake, Washington, was studied during a period of mcromixis (1950–1953) and during a period of holomixis (1968–1972). Comparisons of thermal cycles, light penetration, chemical distribution, and productivity indicate that the lake had a greater productivity while meromictic, even though the seasonal accumulation of dissolved materials in the deep waters was greater during the holomictic period. Calculations showed that the stability due to chemical stratification was actually greater during the holomictic period, supporting the idea that in biogenic meromictic lakes circulation may be controlled more by thermal phenomena than by chemical stratification. Turbid inflows during winter tended to destroy meromixis, but low transparencies due to algal blooms in summer tended to encourage it and may be the primary way by which biogenic meromictic lakes become permanently stratified.
Internal free oscillations in Lake Ontario1
Authors: Schwab David J.
Published: March 2010

A numerical procedure is used to calculate some of the internal free modes of oscillation in a two‐layer model of Lake Ontario, assuming a uniform equivalent depth. The modes fall into two categories, one set resembling Kelvin‐type waves and the other resembling Poincaré‐type waves. Observational evidence from Lake Ontario agrees qualitatively with the properties of these two types of modes.
Analysis of variations in ocean color1
Authors: Morel Anclré , Prieur Louis
Published: March 2010

Spectral measurements of downwelling and upwelling daylight were made in waters different with respect to turbidity and pigment content and from these data the spectral values of the reflectance ratio just below the sea surface, R(λ), were calculated. The experimental results are interpreted by comparison with the theoretical R(λ) values computed from the absorption and back‐scattering coefficients. The importance of molecular scattering in the light back‐scattering process is emphasized. The R(λ) values observed for blue waters are in full agreement with computed values in which new and realistic values of the absorption coefficient for pure water are used and presented. For the various green waters, the chlorophyll concentrations and the scattering coefficients, as measured, are used in computations which account for the observed R(λ) values. The inverse process, i.e. to infer the content of the water from R(λ) measurements at selected wavelengths, is discussed in view of remote sensing applications.
Diel variations in the photosynthetic parameters of coastal marine phytoplankton
Authors: MacCaull Wendy A. , Platt Trevor
Published: March 2010

The diel variations in the assimilation number, PmB, of natural assemblages of coastal marine phytoplankton were examined and a working model proposed to characterize the apparent diel rhythm. No rhythm could be distinguished for the initial slope of the light saturation curve, α, although α and PmB were highly correlated and the daily and hourly variations in α were as great as those in PmB. Diel variations in the derived parameter Ik(≡PmB/α) were described by a model similar to that proposed for PmB. The rhythm PmB was found to have a significant effect on the estimation of daily productivity. Correlations with environmental covariates support the hypothesis that the photosynthetic rhythms observed in the field result both from intrinsic oscillations within the phytoplankton cells and from varying environmental factors.
A comparative study of the diurnal carbon fixation patterns of nannoplankton and net plankton
Authors: Paerl Hans W. , Mackenzie Lincoln A.
Published: March 2010

Autoradiographs of nannoplankton show high photosynthetic fixation rates relative to net plankton during early daylight hours. However, net plankton contribute increasingly to community fixation during the afternoon and early evening. During darkness nannoplankton show losses of fixed 14C greatly exceeding those from net plankton. This lack of uniformity in [14C]CO2 fixation and losses will affect the short term daylight 14C measurements routinely used to assess long term trends in eutrophication.
The polarographic measurement of O2, Fe2+, Mn2+, and S2− in hypolimnetic water
Authors: Davison W.
Published: March 2010

Anoxic hypolimnetic waters can he investigated by differential pulse and DC sampled polarography. A single scan can measure dissolved oxygen and ferrous, manganous, and sulfide ions in less than 3 min. The unique properties of the hypolimnion, enhanced concentrations and freedom from oxygen, enable direct measurement without pretreating the water sample. Filtration is unnecessary because an electrochemical kinetic technique measures only labile ionic species of a single oxidation state.
The determination of ferrous iron in natural waters with 2,2′ bipyridyl
Authors: Heaney S. I. , Davison W.
Published: March 2010

Measurements of ferrous iron, in water containing both ferrous and ferric iron, by the 2,2′ bipyridyl method and polarography are compared. When samples are protected from strong solar irradiation and contact with air, and measurements are made quickly, the 2,2′ bipyridyl method can distinguish the oxidation states of iron in anoxic waters containing ferrous iron.
Determination of total nitrogen in aqueous samples using persulfate digestion1
Authors: D'Elia Christopher F. , Steudler Paul A. , Corwin Nathaniel
Published: March 2010

Determination of total nitrogen in aqueous samples after potassium persulfate digestion compared favorably in both precision and nitrogen recovery with determinations obtained using Kjeldahl digestion.
Incomplete extraction of rapidly settling particles from water samplers1
Authors: Gardner Wilford D.
Published: March 2010

Many particles captured in water bottles settle below the sampling spigots and escape detection when the sampler design does not allow for removal of all the enclosed water. Particles lost from 30‐liter Niskin bottles can increase the measured total concentration of particulate matter by a factor of 1.1–1.7 in open ocean samples. Large numbers of particles as small as 4 µm are lost. Scanning electron microscopy showed a significant loss of diatoms, Acantharia, Foraminifera, coccospheres, dinoflagellates, fecal pellets, organic matter, carapaces, and aggregates of particles.
A closing, replicate‐sample, sediment trap1
Authors: Kimmel Bruce L. , Axler Richard P. , Goldman Charles R.
Published: March 2010

A device for collecting sedimenting seston in pelagic systems is described which permits remote closure, sample replication, correction for attached growth, and use in vertical series. The data presented indicate a significant amount of horizontal heterogeneity in seston sedimentation within a small lake basin.
Kinetic models of diagenesis in disturbed sediments. Part 1. Mass transfer properties and silica diagenesis
Authors: Vanderborght Jean‐Pierre , Wollas Roland , Bitten Gilles
Published: March 2010

The results of chemical analysis of the interstitial water of several samples of sediments from a large muddy zone along the Belgian North Sea coast are reported. When special care is taken to collect the cores without disturbing the water‐sediment interface, the vertical concentration profiles display typical patterns that cannot be explained by constant diffusivity models and suggest the existence of two distinct sedimentary layers with different mass transfer properties. A two‐layer model is proposed to describe the vertical silica profiles. It assumes that the mass transfer coefficient in the first 3.5 cm of the sediment upper layer is 100 times higher than in the compacted lower layer. This large increase is mainly due to turbulent processes induced by the movement of the overlying water. From this model, the flux of dissolved silica across the water‐sediment interface is calculated.
Kinetic models of diagenesis in disturbed sediments. Part 2. Nitrogen diagenesis
Authors: Vanderborght Jean‐Pierre , Wollas Roland , Bitten Gilles
Published: March 2010

A two‐layer mass transfer model developed to describe the vertical silica profile in the sediments of a muddy zone of the North Sea along the Belgian coast is applied to the description of the microbiological processes involved in nitrogen diagenesis in the same sediments. Intense aerobic heterotrophic activity and nitrification are postulated in the upper layer. Denitriification and sulfate reduction are assumed to be preponderant in the lower layer. Vertical profiles of oxygen, sulfate, nitrate, and ammonium are then calculated according to the model and adjusted to experimental profiles. The fluxes of nitrate and ammonium across the water‐sediment interface and the rates of ammonification, nitrification, and denitrification in the two layers are calculated from the results of the models.
Nitrification and denitrification in marine sediments from Puget Sound1
Authors: Grundmanis Varis , Murray James W.
Published: March 2010

The anomalous interstitial water chemistry in Puget Sound sediments (200‐m water depth) indicates an intermediate zone at 20‐ to 30‐cm depths which consists of a mixture of 90% interstitial water and 10% bottom water. Irrigation by burrowing benthic organisms is believed responsible. The vertical distribution of interstitial ammonia, nitrate, and nitrite indicates that nitrification is occurring in this intermediate sedimentary zone, with oxygen being supplied by the irrigation process. Above and below this zone denitrification predominates.
The sulfur cycle of a coastal marine sediment (Limfjorden, Denmark)1
Authors: Jørgensen Bo Barker
Published: March 2010

The cyclic transformations of inorganic sulfur compounds in the sediments of a Danish fjord were followed for 2 years. The in situ rate of sulfate reduction measured with a radiotracer technique together with chemical determinations of various sulfur compounds are used to calculate a budget of the complete sulfur cycle. Sulfate reduction rates were high at the sediment surface (25–200 nmol SO42‐ cm−3 d−1) and there was still measurable activity at a depth of 1.5 m. Sulfate reduction is also compared with the benthic community metabolism measured as the oxygen uptake rate of the sediment. Sulfate reduction accounted for 53% of the total mineralization of organic matter in the sediment. Only 3% of the sulfide was derived from organic sulfur. Of all the sulfide produced, 10% was precipitated by metal ions within the anoxic sediment while the rest was reoxidized at the surface. The results demonstrate the dynamic nature of the sulfur cycle, with turnover times for sulfate of 4–5 months and for free sulfide of 1–5 days.
The Flax Pond ecosystem study: Exchanges of carbon in water between a salt marsh and Long Island Sound1
Authors: Woodvoell G. M. , Whitney D. E. , Hall C. A. S. , Houghton R. A.
Published: March 2010

Flax Pond, a tidal marsh on the north shore of Long Island, New York, was used to examine the exchanges of carbon in its various forms between a salt marsh and the coastal waters. The marsh removed fine particulate carbon from the tidal water throughout the year; it tended to be a small source of C as total CO2 and dissolved organic carbon during summer, and a sink for both forms in winter. The net flux of total carbon over a year, measured as total CO2 and as particulate and dissolved organic C, was a small input into the marsh, estimated as about 51 g C m−2. The data were consistent with others showing the marsh to be a net consumer of chlorophyll throughout the year and a strongly heterotrophic system in summer and do not support the conventional view of marshes as net sources of fixed carbon to coastal waters.
Biological transport of zinc‐65 into the deep sea1
Authors: Pearcy W. G. , Krygier E. E. , Cutshall N. H.
Published: March 2010

The specific activities of zinc‐65 (65Zn: Zn) in pelagic and benthic animals collected off Oregon were correlated with depth of capture to estimate vertical biological transport rates. Results suggest that about 2 yr are required for transport of 65Zn from near‐surface to abyssobenthic animals. Vertical transport appears to be slower in upper waters, suggesting recycling of zinc within biological communities, and more rapid below 500 m. The long vertical transport time for zinc contrasts with the shorter times estimated for transport of zinc and other elements by fecal pellets. This raises questions about the importance of fecal pellets as a rapid transport mechanism for biologically required materials into the deep sea.
Diurnal vertical migration: Adaptive significance and timing. Part 1. Selective advantage: A metabolic model1
Authors: Enright J. T.
Published: March 2010

The diurnal vertical migrations of herbivores usually result in a major decrease in their exposure to food, a sacrifice widely considered warranted because visually orienting predators make daylight hours unsafe for grazers to feed near the surface. A new alternative to that hypothesis is proposed which emphasizes the photosynthetic rather than the visual significance of the day‐night cycle. Among the critical assumptions for this model are: that photosynthetic rate is great enough for algal biomass to increase appreciably from dawn to dusk; that the metabolic needs of grazers can be reduced by resting during nonfeeding hours in cooler waters at depth; and that the grazing rate of herbivores, following an extended interval of nonfeeding, is initially greater than steady state rate and then declines in a matter of a few hours. Calculations based on these assumptions demonstrate that nocturnal feeding by a grazer might be able to provide a greater net energy gain for growth and reproduction than continuous feeding.

An unexpected prediction of this approach is that if maximizing net energetic gain is of greater selective importance than avoidance of visually orienting predators, grazers ought to migrate upward and begin feeding well before sunset, rather than after as the predation hypothesis presumes. The exact timing of the postulated feeding optimum depends on assumed values of several parameters, but most of the calculated advantage seems attainable by an onset of grazing 1–2 h before sunset. This prediction provides a simple first test of the general hypothesis.
Diurnal vertical migration: Adaptive significance and timing. Part 2. Test of the model: Details of timing1
Authors: Enright J. T. , Honegger H.‐W.
Published: March 2010

The hypothesis that vertical migration has evolved primarily as a means of avoiding visually orienting predators is based on the common impression that grazers migrate upward and begin feeding in darkness, after sunset. An alternative hypothesis predicts that grazers might gain significant metabolic advantages if they began to feed a couple of hours before sunset. In three field sampling programs each of 3‐days duration undertaken to distinguish between these alternative behavioral patterns, duplicate samples were taken at 30‐min intervals during late afternoon and evening. The data for the abundant herbivorous copepod Calanus helgolandicus (pacificus) have been analyzed in detail. In one of the sampling programs, in early summer and at lowest herbivore abundance, migration began only after sunset, for both adults and immatures, suggesting that avoidance of predators was of overriding importance under those circumstances. In another sampling program, in late spring and at highest herbivore abundance, the onset of migration for adults as well as immatures began consistently an hour or two before sunset, suggesting that predator avoidance was relatively unimportant under that set of circumstances. Migration of immatures in the third sampling program, in midspring, began an hour or two before sunset but that of adults began only after sunset, suggesting that the appropriate trade off between improved survivorship by predator avoidance and possible metabolic advantage may depend on the developmental stage of the animal.
Uptake of glycine by natural phytoplankton communities
Authors: Wheeler P. , North B. , Littler M. , Stephens G.
Published: March 2010

Uptake of [14C]glycine by various size fractions of natural plankton communities was measured to determine if phytoplankton can compete effectively with other members of the plankton community for the free amino acids in seawater. The simultaneous occurrence of glycine uptake, plant pigments, and photosynthetic activity in the same size fractions, as well as autoradiography of the plankton samples, indicated that in some cases phytoplankton were responsible for 50% or more of glycine uptake. Comparison of prefiltration and postfiltration procedures for this type of study provided an explanation for the discrepancy between these results and those of previous studies.
Chemical composition and productivity of Scenedesmus abundans in nitrogen limited chemostat cultures1
Authors: Giddings Jeffrey M.
Published: March 2010

Particulate nitrogen (PN), particulate carbon (PC), chlorophyll a, and cell numbers were measured in nitrate and ammonium limited chemostat cultures of Scenedesmus abundans. With increasing growth rate, PN : PC increased but PN : cell did not vary. Variations in PN : PC are interpreted as reflections of relative rates of nitrogen and carbon assimilation. Net particulate carbon production was a positive linear function of growth rate. Eighty percent of the increase in net carbon production with increasing growth rate was attributable to synthesis of nitrogenous compounds, while production of nonnitrogenous compounds remained nearly constant.
The use of the 13C and 15N isotopes for the simultaneous measurement of carbon and nitrogen turnover rates in marine phytoplankton1
Authors: Slawyk Gerd , Collos Yves , Auclair Jean‐Christian
Published: March 2010

A stable carbon isotope (13C) is used to estimate carbon assimilation by phytoplankton. Limited modifications to the existing mass spectrometric 15N method allow the simultaneous measurement of carbon and nitrogen uptake by phytoplankton. Details of the 13C procedure are given. Data on simultaneously obtained 15N, 13C, and 14C uptake rates are presented for three species of marine algae grown under varying conditions of light and nutrients. A good agreement between 13C and 14C uptake rates was found (correlation coefficient of 0.91 was calculated from the data). The 13C method should be useful in investigating the relationship between photosynthesis and inorganic nitrogen assimilation in natural phytoplankton and laboratory cultures.
Growth of Capitella capitata cultured on various levels of detritus derived from different sources1
Authors: Tenore Kenneth R.
Published: March 2010

Capitella capitata was cultured on three levels of five organic sources of detritus (Spartina alterniflora, Zostera marina, mixed cereal, Fucus, and Gracilaria sp.). Standing crops increased with increasing food levels of all types of detritus, with a general gradation in the nutritional value of marsh grass < eelgrass < mixed cereal < rockweed < Gracilaria.

The best index of nutritional value was the amount of nitrogen supplied to the polychaetes. The biomass obtained at the highest feeding level of nitrogen‐poor eelgrass was about the same as that at the medium feeding level of rockweed. Once a given level of nitrogen (50 mg m−2 d−1) was available, caloric value apparently affected the nutritive quality of the detritus: the high feeding levels of rockweed resulted in greater standing crop of the polychaete than diets of Gracilaria containing similar levels of nitrogen but fewer calories.
A flow‐through heavy fraction zooplankton sorting column1
Authors: Wormuth John H.
Published: March 2010

A system has been developed to permit separation of an average of 95% of shelled molluscs (and other heavy organisms) from zooplankton samples. The medium used is water rather than dense salt solutions.
Nutrients and production of giant kelp, Macrocystis pyrifera, off southern California1
Authors: Jackson George A.
Published: March 2010

Concentrations of nutrients in the vicinity of the giant kelp (Macrocystis pyrifera) off San Diego, California, varied seasonally. Surface nitrate concentrations were low for most of the year (usually <1 µM), higher during winter. Nitrate concentrations below 4.5‐m depth usually exceeded 1 µM and were highest during spring upwelling, lowest during summer. Nutrients in the kelp bed were not depleted by the kelp nor enhanced by sediment regeneration, implying relatively fast exchange between water in the bed and outside waters. Nutrient concentrations varied at different longshore locations. The condition most limiting to M. pyrifera was probably the low concentration of dissolved nutrients, especially nitrogenous substances, near the sea surface. Translocation of nitrogenous compounds by the kelp plant from depths where concentrations are higher could compensate for this limitation. The summer die‐off of the surface canopy may be caused by the inability of plants to translocate nutrients due to low availability of nutrients in the deeper water. The maximum change in dissolved oxygen measured was 0.43 mol O2 m−2 between 0900 and 1130 PST; extrapolated to 1 day this yields a production of 1.0 mol O2 m−2 d−1 (9.5 g C m−2 d−1).
Nitrogenous nutrition of the plankton in the Chesapeake Bay. 1. Nutrient availability and phytoplankton preferences
Authors: McCarthy James J. , Taylor W. Rowland , Taft Jay L.
Published: March 2010

Eight stations in the main body of Chesapeake Bay and one on the continental shelf were sampled seven times over a period of 13 months to investigate the nitrogenous nutrition of the phytoplankton. The rates at which the phytoplankton were utilizing NO3−, NO2−, NH4+, and urea N were determined. The data demonstrate that for a large portion of the year there is inadequate N nutrient available to permit a single doubling of the particulate N.

Over temperatures from 4°–28°C and salinities from 2–32‰, there was a universally high phytoplankton preference for NH4+ and urea N over NO3− and NO2−. A relative preference index indicated that NH4+ concentrations in excess of 0.5–1.0 µg‐atom N liter−1 almost totally suppressed NO3− utilization. Urea N was used after NH4+ in order of preference, and when the sum of available NH4+ and urea N was insufficient to meet the phytoplankton N nutrient demand, NO3− was used. When the sum of all available N nutrients was less than that required to satiate the phytoplankton demand, NH4+, urea N, NO3−, and NO2− were all utilized at rates proportional to their availability.

For the midbay region in October 1973, NO2− was the dominant N nutrient present both in the water and in the diet of the phytoplankton.
Phosphorus absorption, translocation, and secretion in Nuphar luteum1
Authors: Twilley Robert R. , Brinson Mark M. , Davis Graham J.
Published: March 2010

Absorption, translocation, and subsequent secretion of phosphorus by Nuphar luteum was studied under laboratory and field conditions. Laboratory studies showed that absorption rates (per gram dry weight of absorbing organ) differed with the absorbing organ (roots > submersed leaves > floating leaves). Uptake rates for submersed leaves gave a hyperbolic curve, saturating at high P concentrations. In the Chowan River, North Carolina, native plants were enclosed in chambers for 24 h while simultaneously exposing submersed leaves to ‘Y and roots of the same plant to 32P. Translocation was bidirectional, with the acropetal pathway (roots to leaves) dominating. Translocation rates were affected more by seasons (summer > spring > winter) than were absorption rates by roots. Seasonal differences in translocation rates were significant (P < 0.05), but absorption rates for roots were not. About four times more P moved acropetally than basipetally during summer. Translocated P was secreted by roots and submersed leaves during summer only.
The chlorophyll fluctuation spectrum in the sea1,2
Authors: Denman Kenneth , Okubo Akira , Platt Trevor
Published: March 2010

The spatial heterogeneity of phytoplankton abundance in the sea is controlled both by the turbulent motions of the water and by the rate of reproduction of the organisms themselves. An expression is derived for the shape of the chlorophyll fluctuation spectrum as a function of wavenumber based on an approach first used in the study of reacting mixtures in a turbulent fluid. Unlike an earlier version, this spectrum has a maximum value at a wavenumber km = (6rε−1/3/5)3/2, where r is the rate of growth of the phytoplankton and ε is the rate of dissipation of turbulent kinetic energy. For wavenumbers k ≫ km the spectrum is proportional to k−5/3, not unlike that for a passive scalar such as temperature. The significance of the existence of the spectral peak is that it implies a preferred size for phytoplankton patches in the sea. For typical oceanic conditions, km−1 ≈ 5–10 km.
Lake Tahoe geochemical study. 1. Lake chemistry and tritium mixing study
Authors: Imboden Dieter M. , Weiss Ray F. , Craig Harmon , Michel Robert L. , Goldman Charles R.
Published: March 2010

The study of vertical mixing in Lake Tahoe by temperature and oxygen measurements is limited to the top layer of the lake, since vertical gradients are extremely small at greater depth. Below 200 m the temperature gradient is about −1.6 ✕ 10−4 °C m−1, with little or no seasonal variation. A tritium profile was taken at a midlake station in 1973 together with samples for measurements on lake chemistry. Oxygen, nitrate, total inorganic carbon, and pH showed the effects of photosynthetic activity to a depth of about 80 m, well below the thermocline; average planktonic composition was calculated from these data. Silicate and carbonate alkalinity profiles were essentially uniform, showing that biological removal is negligible in comparison to the rate of vertical mixing.

Essentially no variation in tritium concentration with depth was observed. Tritium measurements and input estimates in Crater Lake were used to calculate tritium concentration in Lake Tahoe between 1954 and 1973 and to estimate a ratio in tritium input of 32% precipitation to 68% vapor exchange. The tritium profile gives strong evidence for at least occasional complete mixing of Lake Tahoe. The last complete mixing may have occurred in March 1973 and at least one other such event took place between 1964 and 1968.
Epibenthic and benthic microcrustaceans (copepods, cladocerans, ostracods) from a nearshore area in southeastern Lake Michigan1
Authors: Evans Marlene S. , Stewart John A.
Published: March 2010

Cores of bottom sediments and overlying waters were collected from depths of 6 and 9 m in southeastern Lake Michigan. Copepod, cladoceran, and ostracod abundances were assessed in terms of known plankton. Species could be roughly divided into euplanktonic species showing no affinity for the sediments, epibenthic species occurring in the plankton but concentrated near the sediments, and benthic species inhabiting the sediments and rarely encountered in the plankton. While several epibenthic species left the sediments at night to enter the plankton, only a small fraction of the benthic species showed this migration. Epibenthic and benthic microcrustaceans in the lower 0.3 m of the water column accounted for 33–39% of the standing stock (by numbers) of the microcrustaceans within the 9‐m depth contour. Preliminary information on the local food web indicates that the microcrustaceans have a significant role in the trophodynamics of the inshore area. Several of the species found in southeastern Lake Michigan are tolerant of eutrophic, mesotrophic, or moderately saline waters.
Mechanical adaptations of a giant kelp
Authors: Koehl M. A. R. , Wainwright S. A.
Published: March 2010

Unusually high extensibility of the kelp Nereocystis luetkeana minimizes breakage by waves and tidal currents. Cellulose fibrils in cortical cell walls have a preferred angle of 60° to the stipe axis; this may be the structural basis of stipe extensibility. Although undamaged plants can sustain drag due to most waves and tides, breakage of single plants occurs most often at flaws in the stipes caused by sea urchin grazing or by abrasion.
Observed resultant circulation of Lake Ontario
Authors: Pickett R. L. , Bermick S.
Published: March 2010

Vector‐averaged current dataergy in summer winds and currents and more low frequency energy in winter winds and currents. from June–October 1972 suggest that Lake Ontario’s resultant circulation during the stratified period consists of a dominant counterclockwise gyre together with a small clockwise gyre in the northwest portion of the lake. Current speeds are lowest in spring and have maximum vertical shear in early autumn. Spectra comparing summer and winter winds and currents show more high frequency energy in summer winds and currents and more low frequency energy in winter winds and currents.
The thermal structure of the Dead Sea
Authors: Ben‐Avraham Zvi , Hënel Ralph , Assaf Gad
Published: March 2010

The thermal structure of the Dead Sea was measured with a sensitive probe (2 ✕ 10−3°C accuracy). It displays a horizontal uniformity below a depth of about 100 m. An adiabatic temperature distribution was found from the bottom (335 m) to a depth of 185 m.
A note on winter temperature variations in a shallow seagrass flat1
Authors: Smith Ned P.
Published: March 2010

Hourly temperature readings over a 69‐day period in winter 1973–1974 are used to characterize both diurnal and longer period temperature variations in a shallow seagrass flat along the Texas coast. The average diurnal temperature variation has a range of about 2.4°C and includes 8 h of warming, starting at about 0800, followed by 16 h of relatively slow cooling. Longer term, quasi‐periodic temperature variations occur at intervals of 11–13 days in response to frontal passages. Temperatures fall between 8° and 14°C in the first 2 days following the frontal passage, before rapid warming begins.
Measurements by geomagnetic induction of volume transport in a salt marsh drainage channel1,2
Authors: Sanford Thomas B.
Published: March 2010

Volume transport of seawater through a salt marsh drainage channel is obtained by geomagnetic induction. The electric potential difference across the channel is interpreted in terms of water motion through the vertical component of the earth’s magnetic field. A model is formulated relating volume transport to induced potential differences and a salt bridge technique described for measuring the weak voltages. Calibration requires independent measurements of the volume transport. Using surface flow, rather than volume transport, for calibration results in method errors as large as 25%. Calibration against directly measured volume transport would reduce these errors.
Diel cycles of inorganic nitrogen uptake in a natural phytoplankton population dominated by Gonyaulax polyedra1
Authors: MacIsaac J. J.
Published: March 2010

The diel characteristics of nitrate and ammonium uptake in a Gonyaulax polyedra bloom were observed during a field program along the west coast of Baja California. The simultaneous presence of light and inorganic nitrogen (especially nitrate) appeared necessary to generate uptake rates sufficiently high to allow growth of these dinoflagellate populations to bloom proportions. Field data from this and other areas revealed no significant differences in the light requirements of diatoms and dinoflagellates.
Kinetics of phosphate uptake by aquatic microorganisms: Deviations from a simple Michaelis‐Menten equation 1
Authors: Brown Edward J. , Harris Robin F. , Koonce Joseph F.
Published: March 2010

The uptake kinetics of dissolved inorganic phosphate (31P1) by lake water microorganisms and a green alga (Selenastrum capricornutum) were determined as a function of uptake rates of radiophosphate (32P1) at added 31P1 levels ⩾ 0. The data did not follow a simple Michaelis‐Menten equation.
Seasonal changes in respiratory enzyme activity and productivity in Lake Washington microplankton 1
Authors: Devol Allan H. , Packard T. T.
Published: March 2010

The seasonal cycle of respiratory electron transport system (ETS) activity, 14C uptake, chlorophyll, temperature, and nutrient concentration in the euphotic zone of Lake Washington during 1974 shows minimum ETS activity (4.2 mg Oeqm−2h−1), 14C uptake (84 mg C m−2d−1), and chlorophyll (10.1 mg m−2) occurred in the first few months of the year and coincided with minimum temperature (≃6.2°C) and maximum nutrient concentrations (PO43− = 250 mg m−2, NO3− = 3.5 g m−2). Maximum ETS activity (109.8 mg Oeqm−2h−1), 14C uptake (2,126 mg C m−2d−1) and chlorophyll (121.7 mg m−2) were observed during the spring bloom. Values were intermediate during the fall period of thermal stratification and nutrient depletion. Respiration rates were calculated from ETS activities and used to calculate production:respiration ratios (P:R). The P:R ratios were low in late summer and fall and high in winter. The percentage of primary production oxidized during a 12‐h dark period varied from >100% to 7%: high percentages in summer, low in late winter.
Phytoplankton extracellular release and its relation to the seasonal cycle of dissolved organic carbon in a eutrophic lake 1
Authors: Storch Thomas A. , Saunders George W.
Published: March 2010

The concentration of total dissolved organic carbon (TDOC), the daily rates of release of extracellular dissolved organic carbon (DOC) by viable phytoplankton, and the daily rates of assimilation of the phytoplankton extracellular DOC by bacteria were investigated simultaneously from April through October in Frains Lake, Michigan. The concentration of TDOC varied aperiodically. The release of DOC by phytoplankton and its utilization by bacteria fluctuated markedly, but these processes did not play a significant role in causing the seasonal variations of TDOC. Increases in the concentration of TDOC greatly exceeded the amounts accumulated from release by the phytoplankton, even when maximum rates of phytoplankton DOC release were calculated by assuming release exclusively from a large intracellular pool not at isotopic equilibrium. In addition, bacterial utilization of the phytoplankton DOC alone could not account for decreases in TDOC concentration. Therefore, there must be other major sources of dissolved organic matter than that provided by the mechanism of extracellular release by phytoplankton. The littoral flora and the decomposition of dead particulate organic materials are the most likely sources of fluctuations of TDOC in Frains Lake.
Phosphorus loadings to lakes and some of their responses. Part 2. Regression models of summer phytoplankton standing crops, winter total P, and transparency of New York lakes with known phosphorus loadings 1
Authors: Oglesby R. T. , Schaffner W. R.
Published: March 2010

An interrelated series of regression equations is derived to define the response of lake ecosystems to mixed zone phosphorus loadings in terms of simple and readily determinable parameters. Data used were collected over 1–4 yr for 16 lakes in central New York State characterized by a wide variety of morphometries, hydrologies, and phosphorus loadings.

The regressions describing the dependence of summer phytoplankton standing crop and winter total P concentration on loading and of standing crop on total P were linear. Those characterizing water transparency as a function of standing crop and winter total P were parabolic. All regressions showed high correlation coefficients.

The overall model composed of these regressions establishes a quantitative basis for the concept that phosphorus supplied to lakes exerts a uniquely controlling role on phytoplankton standing crop. The regressions may he used for trophic state description and in the development of management strategies for lakes.
Sulfate uptake as a measure of bacterial production 1
Authors: Jordan Marilyn J. , Peterson Bruce J.
Published: March 2010

The [35S]SO4 uptake method forestimating bacterial production was tested on two isolates from a freshwater lake. The rate of S (as SO4) uptake multiplied by the cell C:S ratio was an accurate estimate of bacterial carbon production over a wide range of growth rates. The C:S weight ratios ranged from 98 to 110 for five isolates (< x > = 103) and was 218 for a sixth, assuming an isotopic discrimination of 4% for 35S vs. 32S uptake. Further investigation is required before SO4 uptake can be used as a measure of bacterial production in field studies.
Difficulties in interpretation of microbial heterotrophy from sulfate uptake data: Laboratory studies 1
Authors: Monheimer Richard H.
Published: March 2010

Inorganic carbon uptake (primary production) and sulfate uptake were studied in axenic cultures of a Chlorella sp., a Nannochloris sp., and a Scenedesmus sp. All of the cultures took up significant amounts of sulfate in the dark, and it is concluded that the direct use of dark sulfate uptake as a measure of in situ bacterial heterotrophic production is probably not valid. The C:S uptake ratios of the algal cultures in the light also varied widely so that the indirect use of a single C:S value for calculating microbial heterotrophic production is also not valid. Carbon:sulfur uptake ratios appear to have some regular but complex relationship to primary production.
Improved filtration procedures for freshwater [35S]SO4 uptake studies 1
Authors: Jordan Marilyn J. , Daley Ralph J. , Lee Kenneth
Published: March 2010

Procedural improvements suggested in the use of [35S]SO4 uptake as a possible measure of microbial production include: prompt filtration and sterilization of stock solutions, use of polycarbonate Nuclepore filters, prewetting filters, addition of Na2SO4 to samples before filtration, rinsing filters with 1 g liter−1 (0.01 M) Na2SO4, removal of filter edges before liquid scintillation counting, and dissolving Nuclepore filters in phenethylamine before adding scintillation cocktail. This procedure results in control filter counts of 0–200 cpm above background at isotope concentrations of up to 2.0 µCi ml−1 of sample.
Tritiated thymidine incorporation as a measure of microbial activity in lake sediments
Authors: Tobin Richard S. , Anthony D. H. J.
Published: March 2010

Cell proliferation, determined by incorporation of tritiated thymidine into DNA, was used as a measure of microbial activity in lake sediments. Microbial activity in surface and sediment samples from Lake Erie was compared by this technique; activity was greatest in the surface 7 cm of core samples and geographically in a central basin core. The specificity, sensitivity, and low background inherent in the method make it suitable for routine estimates of microbial activity.
An improved method for the extraction of adenosine triphosphate from marine sediment and seawater
Authors: Bulleid N. C.
Published: March 2010

A method is described for extracting adenosine triphosphate (ATP) from both marine sediment and seawater with MeIlvaine (phosphate‐citrate) buffer at pH 7.70. This method compares favorably with techniques using tris and bicarbonate buffers and avoids the disadvantages of mobilized cations produced by an acidic extracting medium. Recovery of ATP added as stationary phase bacteria was 94.5% from sediment and 97% from seawater.
Optical classification of natural waters 1
Authors: Smith Raymond C. , Baker Karen S.
Published: March 2010

A technique has been developed that leads to an optical classification of natural waters in terms of the dissolved and suspended biogenous material present. As a first approximation, this classification has been made in terms of the total chlorophyll‐like pigment concentration.

A relationship between the spectral diffuse attenuation coefficient for irradiance and the chlorophyll‐like pigment concentration has been found with spectral irradiance data from diverse types of ocean waters. The specific spectral attenuation coefficient due to phytoplankton is shown to be consistent with laboratory measurements of the diffuse absorption coefficient of various lot cultures of phytoplankton.