bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sustained viability of aphotic phytoplankton in Lake Tahoe (California‐Nevada)
Authors: Tilzer Max M. , Paerl Hans W. , Goldman Charles R. 
Published: March 2010

Biomass, chlorophyll a, and photosynthetic potential of phytoplankton were measured year‐round throughout a 450‐m water column of ultraoligotrophic Lake Tahoe. Phytoplankton biomass was uniform from the surface to the maximum depth while the lake mixed completely in March, but was lower in aphotic waters during thermal stratification. Aphotic chlorophyll a concentrations decreased progressively in fall and reached a minimum of 17% of mean euphotic concentrations in January, before the mixing depth exceeded the euphotic depth. Photosynthetic rates measured in an incubator under constant light conditions were significantly correlated with pigment concentrations in both euphotic and aphotic phytoplankton and demonstrated viability of the aphotic phytoplankton throughout the year.High surface : volume ratios of the small species dominating the phytoplankton assemblage suggest low sinking velocities. Extremely slow decomposition is postulated to explain the vertical pigment concentration gradients in the aphotic zone.Re‐entry of viable aphotic phytoplankton into the euphotic zone during deep mixing of the lake can diminish the dilution of euphotic phytoplankton, thereby increasing the magnitude of the subsequent vernal bloom.
A device for measuring seepage flux in lakes and estuaries1
Authors: Lee David Robert 
Published: March 2010

Seepage flux can be measured and samples of groundwater flowing into lakes and estuaries collected by enclosing an area of bottom with a cylinder vented to a plastic bag. The method has the advantage of not requiring measurements of permeability of bottom sediments. Seepage velocities from −0.1–2.58 µm s−1 were measured in Minnesota and Wisconsin lakes and in Nova Scotia and North Carolina estuaries.Where seepage inflow was rapid (0.4–0.8 s−1), water collected with the seepage meter was chemically similar to water from wells on the same flow path, and the distribution and chemistry of the seepage concurred with a theoretical flow net. The rate and direction of seepage flux were correlated with water surface elevation during a tidal cycle.
Dynamics of O2 and CO2 exchange, photosynthesis, and respiration in rivers from time‐delayed correlations with ideal sunlight
Authors: Schurr J. M. , Ruchti J. 
Published: March 2010

The oxygen exchange constant, photosynthetic rate, and respiration rate for several Swiss rivers have been determined using only the continuous data record of a single oxygen electrode, the measured temperature, and an assumed ideal light intensity curve in conjunction with a simple model rate equation and a novel cross‐correlation computational technique. The method can, in favorable circumstances, be extended to determine also total carbonate dynamics from continuous pH measurements.For the Aare at Bern in March 1974, the oxygen exchange constant was 0.38 h−1, the respiration rate was 0.6 mg liter−1 h−1, and mean photosynthetic rate was 0.28 mg liter−1 The exchange rate for dissolved (but not hydrated or ionized) CO2 was 0.91 times that for dissolved oxygen, and the ratio of O2 molecules released to CO2 molecules consumed during photosynthesis was about 1.2.
The uptake and release of dissolved phosphorus by reef corals1,2
Authors: D'Elia Christopher F. 
Published: March 2010

The fluxes of dissolved reactive, organic, and total phosphorus into and out of non‐feeding corals were measured by chemical and radiochemical techniques. A net uptake of reactive phosphorus from seawater by corals containing zooxanthellae was not, at typical ambient phosphorus levels, sufficient to offset simultaneous losses of organic P. Consequently, there was a net loss of total P. A coral without zooxanthellae was unable to remove net amounts of reactive P from solution even at levels above ambient. Reactive phosphorus uptake was light sensitive, was highly temperature dependent, showed characteristics of Michaelis‐Menten kinetics, and could be inhibited by arsenate. An active transport mechanism appears to be involved. The kinetics of net reactive phosphorus uptake were described by a Michaelis‐Menten equation modified to include a correction for an efflux of reactive P accompanying uptake. The mean half‐saturation (K) for uptake was 377 nM and the mean maximum rate of uptake (vmax) was 293 ng atoms P · mg Chl a−1 · h−1.Although the symbiotic corals tested cannot obtain all of the phosphorus they require by means of reactive phosphorus uptake at typical environmental concentrations, the ability of corals to obtain part of it in this manner, and the presence of mechanisms for efficient recycling of phosphorus within the symbiotic association, may help enable corals to flourish in waters low in phosphorus sources.
Chromatographic and SCDP measurements of fossil phorbins and the postglacial history of Little Round Lake, Ontario
Authors: Daley R. J. , Brown S. R. , McNeely R. N. 
Published: March 2010

Estimates are compared of total chlorophyll derivatives from the sediments of meromictic Little Round Lake, Ontario, as determined by the relative SCDP procedure and by quantitative paper chromatographic fractionation. Contrasting profiles of total phorbins were obtained with the two techniques. By comparing SCDP:chromatographic phorbin ratios with extinction coefficients of purified derivatives, the discrepancies are tentatively ascribed to errors in the SCDP procedure resulting from variations in a phorbin composition, interference by b phorbins, and possible interference by nonphorbin contaminants in the 90% acetone extracts. SCDP data must, therefore, be interpreted with great care.From the algal phorbin data and additional information on bacterial phorbins, bacterial carotenoids, and the contemporary limnology of Little Round Lake, it appears that primary productivity increased to a maximum early in postglacial time and then declined progressively to the present low levels. The decline began with the probable onset of biogenic meromixis shortly after the early production maximum. The a:b phorbin ratio indicates strong differential diagenesis of the a phorbins in the lake and also the dominance of plankton containing only chlorophyll a (probably cyanophytes) since the beginning of agriculture in the area.
The dynamics of aquatic systems. 2. The effects of nutrient enrichment on model plankton communities1,2
Authors: Lam Patricia , Levins Richard 
Published: March 2010

When results of laboratory experiments on the effects of nutrient enrichment of algal cultures are extrapolated to field conditions, the predictions of the experiments are seldom fulfilled, because the behavior of a species in a network of interacting variables in nature is quite different from its behavior under controlled conditions.The method of loop analysis is used to demonstrate the properties of a set of models containing three kinds of algae and three kinds of nutrients. Many unexpected effects develop from the interactions within the network, and one‐link physiological effects cannot be extrapolated to ecological situations. For these situations, it is recommended that Liebig’s law of the minimum be replaced by a more holistic approach.
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.
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.
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.
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.
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.
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.
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.
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.
Copper sensitivity of Gonyaulax tamarensis1
Authors: Anderson D. M. , Morel F. M. M. 
Published: March 2010

The copper sensitivity of the dinoflagellate Gonyaulax tamarensis was examined in artificial seawater medium. Two short term responses of the organism to copper toxicity are rapid loss of motility and reduced photosynthetic carbon fixation. The chelators tris(hydroxymethylamino)methane (Tris) and ethylenedinitrilotetraacetic acid (EDTA) were used to demonstrate that copper toxicity is a unique function of cupric ion activity. Copper additions to medium containing EDTA equilibrated with the chelator relatively slowly, resulting in misleading short term data. This kinetic effect was not seen when the major copper chelator was Tris or when the copper was added in a chelated form with EDTA. Variations in manganese concentrations over two orders of magnitude did not alter the results.Cells of G. tamarensis are 100% nonmotile at a calculated cupric ion activity of 10−9.7 M with 50% of the cells nonmotile at 10−10.4 M. Nonmotile cells do not divide or grow larger. Gonyaulax tamarensis growth is totally inhibited at cupric ion activities that only partially inhibit the growth of four other species that have been studied extensively. Furthermore, this toxicity occurs at the calculated copper activity of natural waters, assuming only inorganic copper complexation. Thus organic chelation may be necessary before G. tamarensis can successfully compete with other algal species in coastal waters.
An equilibrium model describing the influence of humic materials on the speciation of Cu2+, Zn2+, and Mn2+ in freshwaters
Authors: Wilson Donald E. 
Published: March 2010

A model for the speciation of Cu2+, Mn2+, and Zn2+ ions in freshwaters was constructed. The solubilities of CuO, MnCO3, and Zn2SiO4 are assumed to control the free metal ion concentrations. Model variables are pH, alkalinity, concentrations of competing cations, chemical characteristics and concentrations of humic substances, and inorganic ligand concentrations. The inorganic anions considered are Cl−, SO42−, OH−, HPO42−, HCO3−, and CO32−.Calculations indicate that all three metals exist primarily as bicarbonate and carbonate ion pairs in waters of 10−2 eq·liter−1 alkalinity. Except for Cu, the uncomplexed ions are predominantly low‐alkalinity species (10−4 eq· liter−1). Humic complexes did not form in appreciable amounts in waters having small quantities of organic material. At high organic concentrations (15 mg·liter−1) the amount of metal ion bound by humic substances is substantial and could control micronutrient availability in freshwaters.
Silicic acid incorporation in marine diatoms on light:dark cycles: Use as an assay for phased cell division 1
Authors: Chisholm S. W. , Azam F. , Eppley R. W. 
Published: March 2010

The timing of silicon incorporation in diatom populations grown on light:dark cycles was monitored using [68Ge]Ge(OH)4 as a tracer for Si(OH)4. The time‐course of frustule formation closely followed the time‐course of cell division in all species examined, and the timing of these processes relative to the light:dark cycle was different for each species. Total uptake of Si(OH)4 was found to be higher than Si(OH)4 incorporation in some species.Seawater samples from the Gulf of California and the Southern California Bight also showed periodicity in Si(OH)4 incorporation when incubated outside under ambient light and surface temperature. The degree of periodicity seems to be inversely correlated with diatom species diversity in the samples, which is consistent with the hypothesis that the pulses in Si(OH)4 incorporation reflect phased cell division in individual species of diatoms.
Interstitial water chemistry of anoxic Long Island Sound sediments. 2. Nutrient regeneration and phosphate removal 1
Authors: Martens Christopher S. , Berner Robert A. , Rosenfeld Jeffrey K. 
Published: March 2010

The stoichiometry of nutrient regeneration in anoxic Long Island Sound sediments is examined through changes in the concentration of dissolved sulfate, ammonia, reactive phosphate, and other chemical species with depth in interstitial waters. In offshore sediments the mean ΔSO4:ΔNH4:Δ∑P ratio is —53:4.6:0.37; in shallow harbor sediment it is −53:19:3.3 and ΔNH4:Δ∑P ratios are half the offshore ratio. These indicated shoreward changes probably reflect more rapid deposition, and thus less preferential stripping of P and N from organic material before burial in shallow water harbor sediments, or selective stripping in the heavily bioturbated upper sediment layers offshore, or both. The effects of differential diffusion and adsorption of ammonia and phosphorus are considered.Phosphate concentration maxima in ammonia‐ and phosphate‐rich shallow harbor sediments yield evidence for possible equilibrium with respect to vivianite, Fe3(PO4)2·8H2O, and struvite, MgNH4PO4·6H2O.
Cadmium in northeast Pacific waters 1
Authors: Bruland Kenneth W. , Knauer George A. , Martin John H. 
Published: March 2010

Northeast Pacific water was collected by five different methods and the Cd in it was preconcentrated by both chelex‐ion exchange and chelation‐organic extraction techniques. All sampling and preconcentration methods yielded essentially the same data. Cadmium was very significantly correlated with phosphate and nitrate at all depths and it appears that the resulting equations, ng Cd · liter−1 = −3.6 + 34.9 (µmol PO4 · liter−1) and ng Cd · liter−1 = 5.1 + 2.45 (µmol NO3 · liter−1), can be used to predict oceanic Cd values.Cadmium concentrations are lowest in nutrient‐depleted surface waters (4.5 ± 0.4 ng · liter−1) and greatest (125 ng Cd · liter−1) at the depths of the PO4 and NO3 maxima. Hence, Cd has one of the highest deep enrichment:surface depletion ratios (≃30) yet observed. Cadmium and phosphorus are also correlated in microplankton, and it is apparent that these organisms and their organic remains are a dominant factor in the biogeochemical cycling of this element.