bluuebunny/crossref_metadata_2025 huggingface dataset:
Competition in zooplankton communities: Suppression of small species by Daphnia pulex1
Authors: Vanni Michael J.
Published: April 2010

The hypothesis that a large zooplankton herbivore, Daphnia pulex, can competitively reduce the abundance of resident zooplankton when colonizing a community of small species was tested in two lakes. When introduced to enclosures in eutrophic Larimore Pond, D. pulex decreased phytoplankton abundance by an order of magnitude, resulting in drastically reduced densities of Tropocyclops prasinus and Mesocyclops edax, the two dominant crustaceans in the pond. Daphnia pulex was also added to enclosures in oligo‐mesotrophic Dynamite Lake, along with nutrients, in a factorial design. Three Dynamite Lake zooplankters were reduced in density by D. pulex under both enriched and unenriched conditions: Bosmina longirostris, Trichocerca multicrinis, and copepod nauplii. Nutrient additions allowed these taxa to overcome some effects of competition with D. pulex. Daphnia pulex reduced the densities of copepods and rotifers common to both lakes more in eutrophic Larimore Pond than in unenriched Dynamite Lake enclosures.

These results show that a large herbivore can reduce the density of some small zooplankton species and therefore contribute to the scarcity of small species in lakes dominated by large herbivores. Furthermore, the results suggest that the competitive effects of a large herbivore on rotifers and copepods may be more pronounced in eutrophic systems because the large species can attain a higher population density, and subsequently alter the resource base to a greater extent, in eutrophic systems.
The effect of food concentration on fecal pellet size in marine copepods1
Authors: Dagg Michael J. , Walser W. Edward
Published: April 2010

Three species of copepods, Temora turbinata, Eucalanus pileatus, and Neocalanus plumchrus, were fed cultures of the diatom, Thalassiosira weissflogii, at concentrations ranging from 0.3 to 14.5 µg Chl liter−1 to determine whether fecal pellet size was related to food concentration. In all three copepods, pellet size increased with food concentration up to about 3 µg Chl liter−1. At higher concentrations pellet size was constant. Pellets were less compact and appeared to be more fragile at low food concentrations.

The level of gut contents in these copepods was also related to food concentration up to about 3 µg Chl liter−1. Below this concentration, ingestion and defecation were balanced in such a way that the gut did not fill, and therefore pellet size was smaller. Food concentrations sufficient to allow a copepod to fill its gut result in the production of fecal pellets of maximum size.

It is concluded that fecal pellets produced by large copepods under conditions of low food availability are less likely to sink out of the euphotic zone than pellets produced by the same copepods under conditions of higher food availability.
Littoral slope as a predictor of the maximum biomass of submerged macrophyte communities1,1
Authors: Duarte Carlos M. , Kalff Jacob
Published: April 2010

The hypothesis that the morphometric characteristics of the littoral zone of lakes are a major determinant of submerged macrophyte biomass was tested in Lake Memphremagog (Québec‐Vermont) by studying the relationship between maximum biomass of submerged macrophytes and physical and sediment characteristics of the littoral zone. The slope of the littoral zone accounted for 72% of the observed variability in maximum submerged macrophyte biomass (MSMB). By also incorporating sediment organic matter the variance explained was raised to 88% (P < 0.0001). A model based on only slope as predictor of MSMB was improved by considering slopes ≷5.33%:

urn:x-wiley:00243590:media:lno19863151072:lno19863151072-math-0001

The power of these two equations to predict the MSMB in a variety of temperate lakes was high (r = 0.90, P < 0.0001). However, the temperate zone model overestimates the MSMB in highly turbid lakes where irradiance rather than slope is pre‐eminent and underestimates the biomass in semitropical and tropical lakes.
Fallout plutonium in two oxic‐anoxic environments1
Authors: Sanchez Arthur L. , Murray James W. , Schell William R. , Miller Laurence G.
Published: April 2010

The profiles of soluble fallout plutonium in two partially anoxic waters revealed minimum concentrations at the O2‐H2S interface, indicating Pu removal onto particulate phases of Fe and other oxidized species that form during the redox cycle. In Saanich Inlet, an intermittently anoxic fjord in Vancouver Island, Canada, the concentration of soluble Pu in the anoxic zone was slightly less than in the oxygenated surface layer. In Soap Lake, a saline meromictic lake in eastern Washington State, Pu concentrations in the permanently anoxic zone were at least an order of magnitude higher than at the surface. Differences in the chemical characteristics of these two waters suggest important chemical species that influenced the observed Pu distribution. In the permanently anoxic zone of Soap Lake, high values of total alkalinity ranging from 940 to 1,500 meq liter−1, sulfide species from 38 to 128 µM, dissolved organic carbon from 163 to 237 mg liter−1, and total dissolved solids from 80 to 140 ppt, all correlated with the observed high concentration of Pu. In Saanich Inlet, where total alkalinity ranged from 2.1 to 2.4 meq liter−1 and salinity from 25 to 32‰ and H2S concentration in May 1981 showed a maximum of 8 µM, the observed Pu concentrations were significantly lower than for the Soap Lake monimolimnion.
Filtering activity of Daphnia in low concentrations of a pesticide
Authors: Gliwicz Maciej Z. , Sieniawska Agnieszka
Published: April 2010

A concentration of lindane (γ‐hexachlorocyclohexane) of 0.05 mg liter−1, much lower than the 48‐h lethal concentration (LC50) of 3.8 mg liter−1, resulted in a 25% depression in the frequency of movements of filtering limbs and mandibles of Daphnia pulex in a food‐free medium. Different instars (from 2nd to 8th) were affected to the same extent. Animals 6–12 h after molting were more sensitive than those 30–36 h after molting. Due to the greater number of molts before reproduction in larger Daphnia species, the effect of low pesticide concentrations may be size‐selective and, therefore, responsible in part for the disappearance of large cladocerans from eutrophic lakes enriched from agriculture.
Tests of an extension to internal seiches of Defant's procedure for determination of surface seiche characteristics in real lakes1
Authors: Lemmin U. , Mortimer C. H.
Published: April 2010

The success of A. Defant's method of calculating surface seiche periods and structures in real lakes is well known. To test whether it can be adapted and applied with similar success in studies of internal seiches in stratified lakes, in which density structure is simulated by two homogeneous layers, we compare the predictions of a computerized version of Mortimer's modified Defant procedure against observations of internal seiche motion in eight lake basins and (in three examples) against the results of more elaborate models. The acceptably close agreement inspires confidence that the modified method is useful for practical predictions which, although approximate, described the principal characteristics of the often large water mass displacements and oscillations. Through their influence on mixing and dispersal, those motions profoundly affect the chemical and biological economies of many lakes. To aid in microcomputer and even pocket calculator applications, we set out steps in the calculation in tabular flow‐chart form. A comparable table for surface seiche calculation is added.

The procedure is not applicable to large lakes in which effects of the earth's rotation are dominant; but for the two largest basins tested here (Léman and Ness) a modification is introduced to take approximate account of rotation.
Microbial consumption of nitric and sulfuric acids in acidified north temperate lakes1
Authors: Rudd John W. M. , Kelly C. A. , St. Louis Vincent , Hesslein R. H. , Furutani A. , Holoka M. H.
Published: April 2010

Rates of sulfate reduction and denitrification were measured in the sediments of unacidified, experimentally acidified, and atmospherically acidified lakes in North America and Norway. These data, plus profiles of porewater and sediment chemistry, demonstrated that in all of the lakes H was being actively consumed by both sulfate reducers and denitrifiers. Both of these microbial activities were assayed in sediments overlaid by oxygenated water, demonstrating that anoxic hypolimnia are not required for in situ alkalinity production. Neither short term experimental acidification nor long term atmospheric acidification had detectably inhibited the activity of these two types of bacteria. Both processes were active at pH 4.5. In lakes that were receiving significant quantities of both nitric and sulfuric acids, short term H+ consumption from denitrification was 1.5–2 times faster than H consumption by sulfate reduction. However on an annual basis, because of loss of reduced sulfur during fall and winter, long term H+ consumption by denitrification was estimated to be 4–5 times as large as H+ consumption by sulfate reduction.
Is “structural” growth of Calanus potentially exponential?
Authors: McLaren Ian A.
Published: April 2010

Evidence is presented that maximal, weight‐specific growth rate of well fed Calanus copepodites is constant, if stored lipid is discounted. This pattern may be true of calanoid copepods in general.
A simple method to detect bacterial associations in bivalve gills
Authors: Thiriot‐Quievreux C. , Soyer J.
Published: April 2010

Recent discoveries have shown that endosymbiotic bacteria may be widespread among bivalve species in different habitats. A simple method is described which allows the detection of bacterial‐gill association with an ordinary light microscope.
Internal waves of the second vertical mode in a stratified lake
Authors: Wiegand Ronald C. , Chamberlain Vivian
Published: April 2010

A time series of measurements of thermal structure and near‐bottom currents in a stratified lake revealed both first and second vertical mode internal seiching. The transition into second‐mode seiching occurred after first‐mode waves, usually generated by pulses of strong winds, died down. We describe the major features of the second‐mode seiche and discuss its effects on mixing in the lake below the thermocline. On the basis of calculations of eddy diffusion coefficients, there is only weak mixing in the interior of the hypolimnion. Scaling arguments suggest that mixing at the lake’s edges due to motion of the isotherms is not significant despite the larger amplitudes of the second‐mode seiche. The most important mixing region appears to be a turbulent bottom boundary layer driven by seiche currents. However, resuspension of bottom sediments did not occur, probably due to a combination of sediment nature and low current speeds.
The structure and dynamics of internal waves in Baldeggersee1
Authors: Lemmin U.
Published: April 2010

Analysis of long records of temperature/depth distribution determined at 10‐ or 20‐min intervals at several stations and extending over three stratification seasons, provides a detailed picture of the characteristics, dynamics, and seasonal variation in activity of internal waves in a small lake (Baldeggersee, Switzerland). Wind stress in general was low, with occasional bursts of higher energy. The ensuing, slightly damped internal seiches govern the dynamics of the stratified lake. The vertical structure displays a dominant response of the first vertical mode. Responses in the second vertical mode, hitherto rarely recorded, are also demonstrated with the help of spectral analysis and models. The horizontal structure of the seiches motion displays dominance and persistence of the fundamental basin mode. Spectral analysis also discloses responses of the second and third basin modes. Multiplying of the spectra with the local buoyancy frequency leads to a collapse of all spectra into a narrow band, pointing toward the possibility of a universal spectrum. New light is shed on apparently common examples of waveform asymmetry and on their interpretation. It is concluded that, in this small‐basin, low‐energy example, internal waves provide motions at all levels, but little vertical mixing.
Surface manifestations of internal oscillations in a highly saline lake (the Dead Sea)1
Authors: Sirkes Ziv
Published: April 2010

The manifestation of internal oscillations at the surface of the Dead Sea during summer 1981 is described. During that time the Dead Sea was highly stratified, with a density difference of 1.7 × 10−2 g liter−1 between its two layers. Measurements of lake level (limnograms) show oscillations with periods of internal seiches as confirmed by thermistor‐chain measurements as well as by a numerical model of internal oscillations. Wind measurements exhibit predominantly diurnal and semidiurnal periods. During autumn 1984 the Dead Sea turned over and its layered structure thereby destroyed. In contrast to the measurements of summer 1981 the limnograms for this timespan show only oscillations associated with periods corresponding to surface seiches, but no sign of internal oscillations.
Carbon isotope fractionation and changes in the flux and composition of particulate matter resulting from biological activity during a sediment trap experiment in Lake Greifen, Switzerland1
Authors: Lee Cindy , McKenzie Judith A. , Sturm Zurich Michael
Published: April 2010

Sediment traps were deployed in Lake Greifen, a hard‐water eutrophic, Swiss lake, for 2 weeks in May and June 1983. Oxygen, pH, and suspended particle concentrations indicated a sharp increase in productivity during the experiment. Carbon isotope composition of the dissolved inorganic carbon recorded the balance between photosynthesis and respiration and showed possible evidence of diffusion of atmospheric CO2 across the water‐atmosphere interface, most likely to replace CO2 used during photosynthesis. Allochthonous mineral debris from resuspended sediments or river input was a major component of the sedimenting material. Due to removal of CO2, large, newly formed calcite crystals precipitated when photosynthesis increased. The carbon isotope ratio of trap calcite and the composition of trap amino acids showed the influence of the detrital input on the more dominant isotopic signal of authigenic calcite. Sediment calcite is enriched in 13C relative to authigenic calcite in the sediment traps. This enrichment is likely due to fractionation during precipitation in the surface waters or during dissolution in the water and sediments due to CaCO3 undersaturation. We found extensive loss of material from unpoisoned sediment traps in the cuphotic zone, most likely due to zooplankton feeding.
Ingestion, gut passage, and egestion by the copepod Neocalanus plumchrus in the laboratory and in the subarctic Pacific Ocean12
Authors: Dagg Michael J. , Walser W. Edward
Published: April 2010

The relationships between ingestion rate, gut content, gut passage time, and egestion rate in the copepod Neocalanus plumchrus were determined in laboratory experiments over a wide range of food concentrations. Ingestion, gut content, and egestion were related to food concentration in a rectilinear manner; increases were linear up to about 4.0 µg Chl liter−1 of Thalassiosira weissflogii and constant at higher concentrations. Gut passage time was constant at food concentrations >4.0 µg Chl liter−1, but passage slowed dramatically at lower concentrations.

Levels of gut pigments in N. plumchrus collected from the central subarctic Pacific Ocean during June 1983 and May 1984 were very low. There was no diel periodicity in gut contents, and no vertical spatial patterns in gut fullness were observed in copepods collected from the upper 80 m. The gut pigment levels were converted to in situ ingestion rates using a gut passage time derived from laboratory and field experiments. Resultant ingestion rates, although extremely low, were approximately what laboratory experiments predicted for the low food concentrations available in this oceanic region. Budgetary considerations suggest that N. plumchrus in the subarctic Pacific Ocean must be supplementing its ingestion of phytoplankton with microzooplankton or that metabolic expenditures must be less than reported for the same species in the Bering Sea.
Food energy supply and demand: A discrepancy between particulate organic carbon flux and sediment community oxygen consumption in the deep ocean1
Authors: Smith K. L.
Published: April 2010

Sediment community oxygen consumption (SCOC) and particulate organic carbon (POC) flux to the benthic boundary layer were concurrently measured at five deep‐sea stations on a transect across the eastern and central North Pacific at various times of year. A free vehicle grab respirometer and Alvin‐manipulated grab respirometer were used to measure SCOC. Paired particle interceptor traps (PITs) were used to collect sedimenting small POC at 100 and 600 m above the bottom. SCOC decreased across the transect from the eutrophic coastal areas off southern California to the oligotrophic central Pacific gyre. These rates were generally highest in June and lowest between fall and early spring across the transect with a recurrent pattern in the magnitude of rates measured during the same months but different years. Flux of POC into the benthic boundary layer decreased across the transect from the eutrophic eastern to the oligotrophic central Pacific. No consistent temporal trends were evident in POC flux across the transect, possibly because of small sample sizes, high intra‐station variability, and short‐term deployments (≤7 d). Comparison of concurrently measured supply of POC with organic carbon demand of the sediment community as estimated from SCOC reveals a supply deficit across the transect for all seasons measured. For one nearly synoptic sampling period across the transect in June 1982, the supply‐to‐demand ratio is lowest at the two nearshore stations where current speeds are highest. A predictive equation for SCOC with a least‐squares regression analysis and log‐transformed data revealed that POC flux as the independent variable accounted for only 59% of the variability in SCOC. Direct coupling between SCOC and POC flux is not confirmed by these results, which may be attributed to the limitations of the measurements or other organic carbon sources.
Photoadaptations of photosynthesis and carbon metabolism by phytoplankton from McMurdo Sound, Antarctica. 1. Species‐specific and community responses to reduced irradiances12
Authors: Rivkin Richard B. , Voytek Mary A.
Published: April 2010

Irradiance‐dependent rates of photosynthesis and photosynthate labeling patterns were measured for phytoplankton in McMurdo Sound, Antarctica. Species‐specific and traditional whole‐water techniques were used to compare the physiological responses of algae collected in a high light environment at the ice edge and from a low light environment under the annual sea ice. There were differences among species within the same sample, for the same species isolated from high and low light environments, and when species‐specific responses were compared with that of the natural assemblage. For algae collected beneath the sea ice, photosynthesis generally saturated at a lower irradiance, and the light‐limited region of the P vs. I relationship had a steeper slope than for the same species collected at the ice edge. Low‐light‐adapted algae incorporated significantly less 14C into proteins and more into low molecular weight compounds and lipids than the same species isolated from a high light environment. Under conditions where reduced rates of protein synthesis were coupled with high rates of carbon uptake, the measurement of photosynthesis may not accurately reflect the physiological condition of the phytoplankton.
Photosynthate distribution by microplankton in permanently ice‐covered Antarctic desert lakes1
Authors: Priscu John C. , Priscu Linda R. , Vincent Warwick F. , Howard‐Williams Clive
Published: April 2010

The distribution of 14C‐labeled photosynthate by microplankton in Lakes Vanda and Fryxell, Antarctica, was measured during the 1984–1985 austral summer. Both lakes had conspicuous deep chlorophyll maxima near the bottom of the oxygenated zone. DCMU sensitivity experiments revealed that photosynthesis below the chlorophyll maximum in Lake Fryxell was partially due to photosynthetic bacteria. These bacteria had notably higher protein and lower lipid labeling than overlying oxic microalgae. Protein labeling in the oxic microalgae had lower Ik and higher α values than for other photosynthetic end products, indicating that protein is synthesized more efficiently at low photosynthetic photon flux density than the other metabolites. The Ik values for complete photosynthesis (<20 µEinst m−2 s−1) are among the lowest yet recorded for phytoplankton.
Algal phagotrophy: Regulating factors and importance relative to photosynthesis in Dinobryon (Chrysophyceae)1
Authors: Bird David F. , Kalff Jacob
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Resuspension in the shallow sublittoral zone of a macrotidal estuarine environment: Wind influence1
Authors: Demers Serge , Therriault Jean‐Claude , Bourget Edwin , Bah Abdourrahmane
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Acceleration of nutrient uptake by phytoplankton in a coastal upwelling ecosystem: A modeling analysis1,1
Authors: Zimmerman Richard C. , Kremer James N. , Dugdale Richard C.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
The use of large shipboard barrels and drifters to study the effects of coastal upwelling on phytoplankton dynamics1, 2
Authors: Wilkerson F. P. , Dugdale R. C.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Slow uptake of 32P over a barrier reef flat
Authors: Atkinson M. J. , Smith D. F.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
A diver‐operated device for the capture of mobile epibenthic organisms1
Authors: Carleton J. H. , Hamner W. M.
Published: April 2010

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
Specific in vivo absorption coefficient of chlorophyll a at 675 nm1
Authors: Haardt Hauke , Maske Helmut
Published: April 2010

Spectral absorption of phytoplankton from cultures and natural samples was measured by means of an integrating‐sphere photometer. Measurements on suspension yielded specific absorption coefficients for healthy phytoplankton cultures in collimated light at 675 nm between 0.007 and 0.013 m2 (mg Chl a)−1. These values were independent of cell density and cell wall material.

Natural samples of Kiel harbor water yielded specific absorption coefficients at 675 nm of 0.009 and 0.017 m2 (mg Chl a)−1. The specific absorption coefficients in suspension were dependent on the optical properties of the individual cells (packaging effect), decreasing (ca. 1/r) with increasing cell size (r radius) and increasing chlorophyll a content per cell as predicted by theory, but are significantly lower than theoretically expected. Comparison with published values shows that specific absorption coefficients of cell suspensions are often overestimated, presumably because of methodological problems.
Effects of a Gulf Stream warm‐core ring on summer seabird distribution in the northwest Atlantic Ocean1
Authors: Haney J. Christopher
Published: April 2010

Species composition, distribution, and abundance of seabirds at a Gulf Stream warm‐core ring differed from water masses of the northwest Atlantic slope, shelf, and Sargasso Sea during August 1984. Mean seabird abundance within the 2‐month‐old ring (12.3 birds km−2) was similar to Slope Water (13.0 birds km−2). Mean biomass of the seabird assemblage within the ring (0.85 kg km−2 wet wt) was intermediate between biomass values in Sargasso Sea and Slope Water. The seabird assemblage within the ring was comprised of one nekton‐feeding species (Puffinus lherminieri) displaced from the parent water mass (Gulf Stream), and the storm‐petrels Oceanites oceanicus and Oceanodroma leucorhoa common in adjacent Slope Water.
Effects of fish grazing on nutrient release and succession of primary producers1
Authors: Hansson Lars‐Anders , Johansson Lars , Persson Lennart
Published: April 2010

Macrophytes (Anacharis canaden sis) growing in aquaria were eliminated by the grazing activity of the omnivorous rudd (Scardinius erythrophthalmus). The phosphorus content in both the water column and periphyton was greater in those aquaria that contained fish. Grazing activity of rudd caused 33PO43− that was injected into the sediment and taken up by A. canadensis through their roots to be released into the water phase. In a pond experiment, grazing rudd reduced the biomass of A. canadensis, which in turn caused the biomass of epiphytic algae to increase. We suggest that nutrients, which are taken up by macrophytes from the sediments, are released by grazing fish. This nutrient pathway may thus promote a succession from submersed macrophytes to other primary producers and accelerate the eutrophication process.
Alkalinity dynamics in an unacidified alpine lake, Sierra Nevada, California1
Authors: Stoddard John L.
Published: April 2010

Gem Lake, a small, unacidified, high elevation lake in the Sierra Nevada, undergoes an annual cycle of low alkalinity (between 30 and 40 µcq liter−1) during the ice‐free season and high alkalinity (>240 µeq liter−1) in fall and winter. Both pH and alkalinity decrease drastically (up to one unit for pH and 200 µeq liter 1 for alkalinity) during spring snowmelt, but chemistry of the snow, snowmelt, and runoff indicate that the declines in alkalinity are due to dilution rather than acidification. The hydraulic residence time in the lake increases from about 135 d in winter to <7 d during snowmelt; high alkalinity water is simply flushed from the lake and replaced by water with an ionic composition very near that of the snowmelt runoff.

Increases in alkalinity in fall and winter can be accounted for by the rates of weathering in the watershed. A mass balance approach is used to reconstruct weathering reactions in the basin; it suggests that the lake receives both surface runoff, with the weathering products of the hydrolysis of granodiorite minerals to kaolinite, and deep water from subterranean circulation, with the products of granodiorite weathering to both kaolinite and smectite. The relative importances of low alkalinity surface runoff and high alkalinity groundwater to the recharge of the lake are proposed as factors controlling the seasonal bicarbonate concentration of the lake.
Spatial scales in CZCS‐chlorophyll imagery of the southeastern U.S. continental shelf1
Authors: Yoder James A. , McClain Charles R. , Blanton Jackson O. , Oeymay Lie‐Yauw
Published: April 2010

A 1‐yr time series of Coastal Zone Color Scanner (CZCS) imagery of continental shelf waters off the southeastern U.S. was statistically analyzed to determine dominant scale lengths in the range from 2 to 100 km for near‐surface chlorophyll (Chl) variability. For each image, we extracted two‐dimensional matrices of CZCS‐Chl concentrations from each of 10 study areas. Variograms (structure functions) were calculated for both the along‐ and across‐shelf dimension of each data matrix, although we designed the study areas to focus on along‐shelf variability. The variograms were used to determine whether the images contained nonrandom structure and, if so, to estimate its scale lengths. Outer shelf CZCS‐Chl distributions lacked apparent spatial structure in about 50% of the data matrices vs. <10% for the inner shelf matrices. In general, scale length increased with distance offshore and did not change with season. For example, the mean scale length (n = 30 images) for along‐shelf CZCS‐Chl variability on the inner shelf off Georgia was 32 km vs. 84 km (n = 18 images) for the outer shelf. We propose that Gulf Stream frontal eddies are the principal determinants of outer shelf scale length and that topographic effects on the position of a coastal salinity front determine scale length on the inner shelf off Georgia and South Carolina.
Oxygen consumption in the Baltic proper1
Authors: Rahm Lars
Published: April 2010

Total oxygen consumption rate, averaged over 1957–1982, and its variations with salinity in the deep water of the Baltic proper are calculated by a system of diagnostic advection‐diffusion equations in a “natural” coordinate frame of reference. Although the data set used is not ideal for a more thorough investigation of the sensitivity of the model, an oxygen budget is formulated. A gross consumption rate of 3 × 10−9 mol m−3 s−1 is obtained. Further, a total consumption of about 0.14 × 10−6 mol m−2 s−1 is found, which is equivalent to an annual carbon input of 50 g C m−2 yr−1.
Dynamics of epiphyton on eelgrass (Zostera marina L.) leaves: Relative roles of algal growth, herbivory, and substratum turnover1
Authors: Borum Jens
Published: April 2010

Biomass accumulation of epiphytic algae on eelgrass leaves with leaf age was measured during three periods in Roskilde Fjord, Denmark. Epiphyte biomass increased exponentially with leaf age during the first 10–14 d of colonization. On older leaves epiphyton gradually approached a phase with only small changes in biomass. Algal doubling times, calculated from biomass accrual, were between 3.6 and 4.6 d on young leaf segments and increased to more than 14 d on old leaves. When corrected for biomass losses due to invertebrate grazing, algal doubling time was only 5.8 d on old leaves in August 1983. In this period grazing accounted for the bulk of epiphyte biomass losses and was a more important factor than eelgrass leaf renewal in reducing epiphytic load. As a conservative estimate, the epiphyte community contributed 4–5 times more to total aboveground production in the eelgrass bed than was indicated by its biomass contribution.
A fluorochrome‐staining technique for counting bacteria in saline, organically enriched, alkaline lakes
Authors: Harvey R. W.
Published: April 2010

A procedure is described for epifluorescence direct‐counting of planktonic bacteria in an alkaline, hypersaline, organically enriched lake. To preclude precipitation and staining of dissolved organic material (DOM), the procedure involved isotonic dilution of unfixed samples at in situ pH and filtration before fluorochrome staining. Fluorochrome‐DOM complexes remaining on the filter were removed by sequential rinses with isotonic 0.1 M citrate (pH 6.6). With the modified procedure, the dye acridine orange (AO) yielded better specimen‐background contrast and higher overall cell counts than did ethidium bromide, Hoechst dye No. 33258, or 4,6‐diamidino‐2‐phenylindole (DAPI).
Bacterioplankton in Lake Michigan: Dynamics, controls, and significance to carbon flux1
Authors: Scavia Donald , Laird Gwenyth A.
Published: April 2010

Lake Michigan bacterial production, based on [3H‐methyl]thymidine (TdR) incorporation and empirically determined conversion factors (5–25 × 109 cells nmol−1), decreased with distance from shore (∼ 2 × over 30 km), was higher at night (1.4 × –2.2 ×), and decreased with depth (∼ 10 × over 100 m). TdR‐based growth rates were consistent with independent antibiotic‐ and dilution‐based estimates. Population size varied little and appeared controlled by balanced growth (0.02–0.33 h−1) and grazing (0.039–0.12 h−1). Growth correlated with temperature only below 10°C. Cell size ranged from 0.015 to 0.072 µm3. Carbon content averaged 0.154 ± 0.047 pg C µm−3. Net annual carbon production was 142 g C m−2 yr−1. Summer averages were 28.9 (epilimnion), 10.4 (10–35 m), 1.6 (hypolimnion) µg C liter− d−1, and 652 mg C m−2 d−1 for the water column. Flux to microconsumers averaged 8.4 µg C liter−1 d−1 in the summer epilimnion.

Annual areal bacterial carbon demand is met by autotrophic production only if little of the latter is lost by other means. This suggests that external loads are needed, our conversion factors are high, or autotrophic production is underestimated. Although only small adjustments of those factors will satisfy the annual balance, the summer imbalance is still too large. We suggest that temporal and spatial disequilibrium of labile organic carbon supply and bacterial use is responsible for the apparent discrepancy during summer.
A comparison of four methods for determining planktonic community production1
Authors: Bender Michael , Grande Karen , Johnson Kenneth , Marra John , Williams Peter J. LeB. , Sieburth John , Pilson Michael , Langdon Chris , Hitchcock Gary , Orchardo Joseph , Hunt Carleton , Donaghay Percy , Heinemann Kristina
Published: April 2010

Samples from two coastal experimental ecosystems were incubated in vitro and sampled over 24 h. Production rates were measured by the 14C method, the O2 and CO2 light‐dark bottle methods, and the18O method. O2 production in the experimental enclosures (volume ∼ 1.3 × 104 liters) was also measured directly.

Photosynthetic and respiratory quotients were close to 1.0. Gross production values determined by O2 light‐dark experiments, CO2 light‐dark experiments, and 18O were similar. 14C production ranged from 60 to 100% of gross production measured in CO2 light‐dark experiments, indicating that 14C uptake is not precisely fixed with respect to other measures of community metabolism. There was no evidence that 14C or any other method underestimated the rate of primary production in vitro by more than 40%. Productivities in vitro ranged from 35 to 100% of those in the mesocosm at similar light intensities.

In samples from one of the ecosystems, the rate of respiration in the light (calculated from 18O data) was an order of magnitude greater than the rate in the dark. This difference may be ascribed to either photorespiration or light enhancement of mitochondrial respiration.
Volumetric estimates of phytoplankton production in newly upwelled waters of the southern Benguela Current1
Authors: Olivieri Emilia T. , Hutchings Laurence
Published: April 2010

Production, in terms of volume of particulate matter, was studied in four developing phytoplankton communities in newly upwelled waters of the southern Benguela Current. Growth (max doublings d−1 2.9, max C production ∼21 g m−2 d−1) of phytoplankton upwelled from source water was rapid, with little evidence of a lag phase. The growth pattern differed for each community encountered and was related to the rate of mixing of the water column and the nutrient and light regimes. Production rates were highest in newly upwelled waters and lowest under limiting light and during periods of nitrate depletion in the upper mixed layer. Changes in growth rates were also attributed to short‐term wind variations that caused water bodies to mix and change the nutrient regimes.

Growth occurred over a wide size range of particles, mostly in the range 20–80‐µm equivalent spherical diameters (ESD), corresponding to chains of diatoms, but occasionally also in the range of 6–14‐µm ESD, suggesting some growth of small‐celled algae and microflagellates. A diel variation was observed, with volume increases during the day greatly exceeding those at night except under extreme limiting conditions when there was some growth in the dark.
Determination of amino acid production rate of a marine phytoplankton population with 13C and gas chromatography‐mass spectrometry1
Authors: Hama Takeo , Handa obuhiko , Hama Junko
Published: April 2010

Combined 13C and gas chromatography ‐mass spectrometry (GC‐MS) were applied to determine the rate of amino acid production of marine phytoplankton populations. The accuracy of the estimate of the 13C ratio in each amino acid using the relative intensity of isotope peaks was investigated with 13C‐enriched amino acid standards. Production rates of 12 amino acids of a natural phytoplankton population were determined. The gross amino acid composition of photosynthetic products is generally comparable with previous reports. Production of amino acid at night was confirmed by the increase in 13C atom%; glucose appeared to supply carbon for amino acid production at night. The ratio of carbon : amino acid nitrogen in photosynthetic products showed a marked diurnal change, due mainly to the loss of glucose carbon at night and the continuing uptake of nitrogen.
A simple and reliable method for making permanent mounts of phytoplankton for light and fluorescence microscopy1
Authors: Crumpton W. G.
Published: April 2010

A simple and reliable method is described for making permanent mounts of phytoplankton for critical microscopy and cell counting. Phytoplankton are fixed with glutaraldehyde, concentrated by gentle vacuum onto cellulosic membrane filters, and mounted directly in a water‐soluble, methacrylic resin. The resulting mounts are permanent and suitable for even very delicate nanoflagellates. Chlorophyll autofluorescence is preserved as is the structural integrity of cells. Resolution is very good and mounts can be examined with bright‐field, phase contrast, differential interference contrast, and fluorescence microscopy.
The influence of host contamination on maltose release by symbiotic Chlorella1
Authors: Douglas A. E.
Published: April 2010

Symbiotic Chlorella cells freshly isolated from green hydra were substantially freed of host cell debris by two methods: washing with 0.05% sodium dodecyl sulfate and centrifugation through a gradient of Percoll. Neither treatment reduced the viability or photosynthetic rate of the algal cells, but maltose release by the native symbionts of green hydra was abolished.
Hydrogen peroxide production by a marine phytoplankter1
Authors: Palenik Brian , Zafiriou O. C. , Morel F. M. M.
Published: April 2010

Hymenomonas carterae, a calcified marine phytoplankter, produces hydrogen peroxide extracellularly. Hydrogen peroxide production by a washed cell suspension occurs in the dark and is inhibited by cell‐impermeable protein modification reagents. A cell‐surface redox enzyme is thus likely responsible for production of H2O2. The physiological function of this potentially toxic compound is unknown. If the production rate of 1–2 × 10−14 mol cell−1 h−1 measured in cultures of H. carterae could be generalized, marine phytoplankton would be an important source of the hydrogen peroxide found in the marine environment.
Relation between photosynthetically available radiation and total insolation at the ocean surface under clear skies1
Authors: Baker Karen S. , Frouin Robert
Published: April 2010

A radiative transfer model is used to investigate the relationship between photosynthetically available radiation, Epar(0+) and total incoming solar radiation, Etot(0+) at the ocean surface. The ratio of Epar(0+) to Etot(0+) lies between 0.42 and 0.50 for most clear sky conditions. The simulations indicate that the parameters governing the variability of Epar(0+): Etot(0+) are the solar zenith angle, the amount of water vapor in the atmosphere, and the aerosol optical thickness. The influence of ozone and other gaseous constituents is insignificant. Comparisons between model results and field data show close agreement. Given the solar zenith angle and an estimate of both the total water vapor amount and the aerosol optical thickness, Epar(0+) can be accurately predicted from Etot(0+) for studies of aquatic photosynthesis.
Photosynthetic action, absorption, and quantum yield spectra for a natural population of Oscillatoria in the North Atlantic1
Authors: Lewis Marlon R. , Ulloa Osvaldo , Platt Trevor
Published: April 2010

Measurements of the photosynthetic action and absorption spectra were made of marine Oscillatoria (Trichodesmium) from a summer surface bloom in the North Atlantic. The absorption spectrum was typical of those of other phytoplankton but with small peaks at 627 and 567 nm and a large peak at 493, consistent with the presence of phycocyanin, phycoerythrobilin, and phycourobilin respectively.

The photosynthetic action spectrum was determined by measurement of the initial slope of the photosynthesis‐irradiance curve every 25 nm from 400 to 675 nm (25‐nm bandpass); it was dominated by the phycourobilin waveband. Calculations of quantum yield indicated that it was constant from 475 to 650 nm and was near maximal theoretical values. In wavebands corresponding to chlorophyll absorption (400‐450 and 675 nm), quantum yield dropped off sharply. Photosynthesis‐irradiance curves determined on both whole colonies and individual trichomes in “white” light indicated that both the initial slope and the degree of photoinhibition at high light were enhanced when the colonies were disrupted‐the former by a factor of ten, although the maximum rate of photosynthesis was unchanged. These optical and photosynthetic characteristics of marine Oscillatoria are consistent with adaptation to the high light environment where they typically bloom.
Optical properties of benthic photosynthetic communities: Fiber‐optic studies of cyanobacterial mats
Authors: Jørgensen Bo Barker , Des Marais David J.
Published: April 2010

A fiber‐optic microprobe was used to analyze the spectral light gradients in benthic cyanobacterial mats with 50‐µm depth resolution and 10‐nm spectral resolution. Microcoleus chthonoplastes mats were collected from hypersaline, coastal ponds at Guerrero Negro, Baja California. Gradients of spectral radiance, L, were measured at different angles through the mats and the spherically integrated scalar irradiance, Eo, was calculated. Maximal spectral light attenuation was found at the absorption peaks for the dominant photosynthetic pigments: chlorophyll a at 430 and 670 nm, carotenoids at 450–500 nm, phycocyanin at 620 nm, and bacteriochlorophyll a at 800–900 nm. Scattered light had a marked spectral effect on the scalar irradiance which near the mat surface reached up to 190% of the incident irradiance. The spherically integrated irradiance thus differed strongly from the incident irradiance both in total intensity and in spectral composition. These basic optical properties are important for the understanding of photosynthesis and light harvesting in benthic and epiphytic communities.
Effects of competitive interactions on the biomass development of planktonic and periphytic algae in lakes1
Authors: Hansson Lars‐Anders
Published: April 2010

In laboratory and field experiments I investigated the influence of competitive interactions on biomass development of planktonic and periphytic algae. In the laboratory periphytic algae, covering the sediment surface, reduced the outflow of labeled phosphorus (33PO43‒) from sediment to water. The reduced outflow caused a decrease in phosphorus content as well as in biomass of planktonic algae. An enclosure field experiment showed that the biomass of periphyton decreased as the density of planktonic algae increased. These results suggest that periphytic algae have a competitive advantage with respect to nutrients released from sediments, whereas phytoplankton are competitively superior with respect to light. The imbalance in competitive ability between the two life‐forms predicts a decrease in periphytic and an increase in planktonic algal biomass with increasing trophic state of lakes. This prediction was corroborated with a field study of Swedish lakes. My investigations suggest that competitive interactions influence the balance between planktonic and periphytic primary production in lakes.
Trophic interactions between heterotrophic nanoflagellates and bacterioplankton in manipulated seawater enclosures1
Authors: Bjørnsen Peter Koefoed , Riemann Bo , Horsted Steen Jesper , Nielsen Torkel Gissel , Pock‐Sten Jan
Published: April 2010

Biomasses of bacterioplankton and heterotrophic flagellates and bacterial net production rates were measured intensively during three periods of 16–25 d in estuarine experimental enclosures manipulated by additions of inorganic nutrients, fish, and mussels. Tightly coupled oscillations in biomasses of bacteria and flagellates were found, particularly during summer. The amplitude of the oscillations increased in response to artificial eutrophication with inorganic nutrients and decreased in response to predation control from added mussels. Losses of bacterioplankton by grazing were assessed indirectly with carbon balances for each enclosure and directly with procaryotic inhibitors and with 3H‐labeled bacteria. Estimates obtained by these three independent approaches showed clearance rates averaging 1.5–2.5 nl h−1 flagellate−1. Comparison of grazing rates to increases in flagellate biomass revealed minimum estimates of flagellate carbon yield averaging 33%. High minimum yields were found in some enclosures during summer. Carbon sources other than bacteria may have been used by heterotrophic flagellates in these situations.
Inorganic nitrogen uptake by marine picoplankton: Evidence for size partitioning
Authors: Harrison W. G. , Wood Laura J. E.
Published: April 2010

A series of size‐fractionation experiments was carried out in coastal waters around Georges Bank and in the oligotrophic NW Atlantic to assess the relative importance of picoplankton (< 1 µm) to community nitrogen utilization and to determine if there is a partitioning of the form of nitrogen used (NO3− or NH4+) based on organism size. Results indicate that picoplankton nitrogen uptake was substantial in coastal and oceanic waters, averaging >30% of the combined nitrate and ammonium uptake by the intact communities; the picoplankton portion of total community N uptake increased offshore. Of the summed nitrate and ammonium used across all sizes, ammonium was favored disproportionately by the picoplankton fraction. On average, however, the differences in preference for nitrogen form were relatively small. The size partitioning of photosynthetic activity and nitrogen uptake was similar.
Biogenic gases and the oxidation and reduction of carbon in Amazon River and floodplain waters
Authors: Richey Jeffrey E. , Devol Allan H. , Wofsy Steven C. , Victoria Reynaldo , Riberio Maria N. G.
Published: April 2010

Concentrations of CO2, O2, CH4, and N2O in the Amazon River system reflect an oxidation‐reduction sequence in combination with physical mixing between the floodplain and the mainstem. Concentrations of CO2 ranged from 150 µM in the Amazon mainstem to 200–300 µM in aerobic environments and up to 1,000 µM in oxygen‐depleted environments of the floodplain. Apparent oxygen utilization (AOU) ranged from 80 to 250 µM. Methane was highly supersaturated with respect to atmospheric equilibrium. Concentrations ranged from 0.06 µM in the mainstem to 100 µM on the floodplain. Concentrations of N2O were slightly supersaturated in the mainstem (∼13 nM) but were undersaturated on the floodplain (averaging 9 nM). Fluxes calculated from these concentrations indicated decomposition of 1,600 g C m−2 yr−1 of organic carbon in Amazon floodplain waters. Analysis of relationships between CH4, O2, and CO2 concentrations indicated that about 50% of carbon mineralization on the floodplain is anaerobic, with 20% lost to the atmosphere as CH4. The predominance of anaerobic metabolism leads to consumption of N2O on the floodplain. Elevated concentrations of CH4 in the mainstem probably reflect input from the floodplain, while high levels of CO2 in the mainstem are derived from a combination of floodplain drainage and in situ respiration.