bluuebunny/crossref_metadata_2025 huggingface dataset:
Depositional fluxes of metals and phytoplankton in Windermere as measured by sediment traps1
Authors: Hamilton‐Taylor J. , Willis M. , Reynolds C. S.
Published: April 2010

Monthly sediment trap samples collected from a deep water station (42 m) in Windermere for a period of 1 year were analyzed for 0.5 M HCl extractable and total Fe, Mn, Al, Pb, Cu, Zn, total C, N, and total solids. Concomitant algal counts showed the year to be fairly typical in terms of the known sequence of phytoplankton.

The annual depositional fluxes are compared with previously determined values based on sediment studies. The ratio of the annual trap to sediment flux for Al (≤ 1) indicates the absence of local sediment resuspension. The ratios for Fe, Pb, and Zn (1.1, 1.4, and 1.5, but not significantly > 1) suggest some possible biogeochemical cycling at the sediment‐water interface. The deposition of Fe, Al, and Pb is predominantly associated with detrital material and occurs mainly during winter. The behavior of Zn is largely independent of other variables examined. The ratios for C (1.8), total solids (2.2), N (3.2), Mn (8.6), and Cu (9.5) are all significantly > 1. The C and N values are thought to reflect the microbial breakdown of organic matter at the sediment surface and more particularly the preferential degradation of proteinaceous (i.e. N rich) material. The major influence on the deposition and recycling of Mn is its well known redox cycle involving oxidative precipitation and reductive remobilization. Cu undergoes an independent deposition‐remobilization cycle, probably related to uptake by diatoms and their rapid microbial decomposition after sedimentation.
Turbulent mixing in the hypolimnion of Baldeggersee (Switzerland) traced by natural radon‐2221
Authors: Imboden D. M. , Joller Th.
Published: April 2010

Three analytical diffusion models are used to describe the distribution of a nonconservative tracer in the hypolimnion of a lake: The one‐dimensional vertical (1‐DV) model, developed for tracers in the deep sea, leads to a significant overestimation of vertical diffusivity Kz in lakes; the one‐dimensional topographic vertical (1‐DTV) model, applicable if horizontal mixing is fast compared to in situ decay, demonstrates that, except for the deepest layers, vertical tracer distributions are insensitive to Kz; the one‐dimensional topographic horizontal (1‐DTH) model, in which horizontal mixing is incomplete and vertical diffusion is disregarded, is the appropriate model for the interpretation of vertical excess 222Rn profiles a few meters above the lake bottom. The radon flux F from the bottom is calculated from 226Ra in the sediments and corrected for depth variation of porosity and radium activity. In Baldeggersee (Switzerland), F is 390 ± 70 dpm·m‒2·d‒1. Radium activities in the sediments are 0.7 ± 0.2 dpm·g‒1 dry mass, similar to those in other Swiss lakes and in coastal areas of the ocean but 20–50 times smaller than in the deep Pacific. Horizontal diffusivity in the hypolimnion decreases from June (5,000 m2·d‒1) to October (1,000 m2·d‒1); vertical diffusivity is between 1 and 10 m2·d‒1, roughly 10 times larger than values calculated from temperature in the upper hypolimnion. Vertical buoyancy flux is between 10‒11 and 10‒10 m2·s‒3, i.e. between values for the deep ocean and the small ELA lakes in Canada. The large Kz and the transient, often irregular shape of the radon profiles are the result of horizontal bottom currents previously measured by other methods.
The light response of nitrogen fixation in Lake Valencia, Venezuela1
Authors: Lewis William M. , Levine Suzanne N.
Published: April 2010

Water samples from six depths in the upper water column of Lake Valencia, Venezuela, were incubated in situ with acetylene at several depths corresponding to different light exposures. On five dates there was sufficient nitrogen fixation to define the light‐response curve for samples taken at 2 and 100 cm. The light response of nitrogen fixation was modeled successfully with an equation previously developed for the light response of photosynthesis. All parameter values of the response curves for samples originating at a given depth were relatively stable across dates, but differed between depths. Rates of increase of N fixation with irradiance in the subsaturation range (α) were much lower than is typical of photosynthesis. While the general shape of nitrogen fixation curves was similar to that of photosynthesis curves, critical parameters were more sensitive to the light history (depth of origin) of cells than would be expected for photosynthesis.
Particle production by planktonic ciliates1
Authors: Stoecker Diane K.
Published: April 2010

Favella sp. (a tintinnid) and Balanion sp. (a nonloricate ciliate) produce fecal aggregates which overlap in size with their dinoflagellate food. These aggregates have a higher C:N ratio than the dinoflagellates. As the aggregates disintegrate, smaller particles are produced. For Favella grazing on the thecate dinoflagellate, Heterocapsa triquetra, the volume of the fecal material produced is 22–23% of the volume of algae consumed.

The similarity in size of microplanktonic algae and ciliate fecal aggregates makes the Coulter Counter inappropriate for use in determining clearance or ingestion rates in ciliate feeding experiments unless egestion rates can be estimated. Visual counts were compared with Coulter Counter data for an experiment in which Favella and Balanion grazed Heterocapsa. The Coulter Counter underestimated ingestion rates by 30% for Favella and by 18% for Balanion and confounded the results in respect to particle size selectivity. However, because electronic particle counting measures the net change in particle concentration (ingestion — egestion) it can be used to measure assimilation rates. The assimilation efficiencies for Favella and Balanion eating Heterocapsa were thus estimated to be 70 and 82%.
Selective particle ingestion by a filter‐feeding fish and its impact on phytoplankton community structure1
Authors: Drenner Ray W. , Mummert John R. , deNoyelles Frank , Kettle Dean
Published: April 2010

The ingestion rates of filter‐feeding gizzard shad for different sizes of suspended particles were measured using mixtures of microspheres and zooplankton. Ingestion rate increases as a function of particle size, leveling off at 60 µm. The particle‐size‐dependent ingestion rates were consistent with a model of filtering efficiency based on the cumulative frequency of interraker distances of gizzard shad gill rakers.

Comparison of ponds containing gizzard shad with control ponds without fish showed that gizzard shad suppressed Ceratium, the only phytoplankton species large enough to be ingested at a maximum rate. Gizzard shad did not have a significant effect on populations of Synedra, Peridinium, Navicula, Kirchneriella, Cyclotella, and Chlamydomonas. Populations of Ankistrodesmus, Cryptomonas, Cosmarium, Rhodomonas, and algae and bacteria from 2‐4 µm were enhanced by gizzard shad.
Utilization of detritus by the copepod, Acartia tonsa1
Authors: Roman Michael R.
Published: April 2010

Ingestion, survivorship, and growth experiments were conducted with the marine calanoid copepod, Acartia tonsa, various concentrations of the diatom, Thalassiosira weissflogii, and detritus derived from the macrophyte, Thalassia testudinum. Copepod ingestion rates of detritus increased with detritus concentration from <50 to > 1,700 µg C·liter−1.

Copepod survival in detritus suspensions was significantly greater than in filtered seawater controls. The instantaneous mortality coefficient, z, of A. tonsa was a linear (negative) function of the diatom concentration (r2 = 0.7831). When T. weissflogii suspensions were supplemented with detritus (1,000 µg C·liter−1), the copepod instantaneous mortality rate decreased (0.3002–0.1362 in 50 µg C liter−1 T. weissflogii; 0.1345–0.0406 in 200 µg C·liter−1 T. weissflogii). The growth rate of A. tonsa was a linear function of diatom concentration (r2 = 0.8816). When the diatom suspensions were supplemented with T. testudinum detritus, the growth rate of the copepod increased.

Thalassiosira weissflogii contained 12 × the protein, 8 × the fatty acids, and a greater amount and diversity of amino acids and polyunsaturated fatty acids per unit dry weight than T. testudinum detritus. Although A. tonsa could not grow from egg to adult on a detrital diet, T. testudinum detritus did supplement algal diets to increase copepod production rates.
Dissolved iodine species in a British freshwater system
Authors: Jones S. D. , Truesdale V. W.
Published: April 2010

Results are presented of a 16‐month study of the spatial and temporal variations of dissolved iodine species in rain, river, and oxic and anoxic lake waters, collected from the same freshwater system in the English Lake District. The interconversion of iodine species during their passage through the system is compared with data from marine basins. Iodate and iodide are the principal forms of dissolved iodine in all the freshwaters tested. Iodine is lost from solution in the soils of the catchment, whereas both iodate‐reduction and iodide‐oxidation processes operate in the water of the lakes. Overall the lacustrine behavior of iodine is similar to that in marine basins.
Carbon flow through oxygen and sulfate reduction pathways in salt marsh sediments1
Authors: Howes Brian L. , Dacey John W. H. , King Gary M.
Published: April 2010

We measured surface O2 uptake, 35SO42− reduction, and total sediment metabolism (CO2 production) in sediments (0–30 cm) supporting stands of short Spartina alterniflora in a New England salt marsh. Sediment CO2 production was highest at the surface where O2 was present and declined rapidly with depth. In deeper sediments (below 5 cm) CO2 production was equal to 35SO42− reduction as determined by the Cr2+ reduction technique. Time‐course experiments using CO2 production and 35SO42− reduction (by Cr2+ reduction and aqua regia digest) indicate that the aqua regia technique is not reliable for measuring SO42− reduction and that the rate of SO42− reduction is much less than previously reported for this marsh.

Our estimates of annual O2 uptake conform with those for CO2 production and belowground production. We estimate carbon mineralization to average about 180 mmol C·m−2·d 1, among the highest measured for marine sediments. Our simultaneous measurements of O2 uptake, CO2 production, and SO42− reduction suggest that at least half of this decomposition occurs via SO42− reduction. We conclude that the mechanisms underlying carbon and sulfur cycling in salt marsh sediments are much more similar to subtidal sediments than previously recognized.
Genetic material in the marine environment: Implication for bacterial DNA
Authors: Paul John H. , Carlson David J.
Published: April 2010

Particulate DNA content (DNAp) in water samples from freshwater, estuarine, and marine environments was measured with the DNA‐specific fluorochrome Hoechst 33258. A good correlation (r = 0.94) was found between DNA content and bacterial number for all samples. Size fractionation with 12‐, 3‐, and 1‐µm Nuclepore filters indicated that the 0.2‐–‐µm fraction contained 40–54% of the total DNAp of fresh/brackish and 71–91% of that of oceanic waters. This fraction also contained most of the bacterioplankton, while the phytoplankton (as indicated by Chl a) was found primarily in the 12–110‐µm fraction. The results suggest that most of the DNAp in the marine environment is associated with bacterioplankton and not with phytoplankton.
Planktonic larvae 05 act like passive particles in turbulent near‐bottom flows1
Authors: Hannan Cheryl Ann
Published: April 2010

The hypothesis that infaunal polychaete larvae (Mediomastus ambiseta) sink through the water like passive particles in turbulent near‐bottom flows was tested in the field with two geometrically different sediment traps. Laboratory flume experiments dictated the a priori prediction that larvae would be significantly overcollected by one trap design relative to the other. In field experiments, this a priori prediction was always supported. Thus, Mediomastus larvae may be distributed in near‐bottom waters according to the hydrodynamical processes governing the distribution of fine suspended sediments. Other processes that could have produced the patterns of larval collections between the trap designs now must be tested against the passive sinking hypothesis. Because the passive sinking hypothesis could not be falsified in these field experiments, considerations of hydrodynamical phenomena must be included in future studies of larval settlement. For example, larvae may first reach the seabed at sites where sediments with similar fall velocities would initially settle.
TMicroorganisms and detritus in the diet of a typical neotropical riverine detritivore, Prochilodus platensis (Pisces: Prochilodontidae)1
Authors: Bowen Stephen H. , Bonetto Argentino A. , Ahlgren Molly O.
Published: April 2010

Quantitative analyses of stomach

contents indicate Prochilodus platensis depends on detritus rather than microorganisms for its nutrition. Chemical data suggest that this detritus is of a different origin than previously supposed.
An examination of lipid reserves and the nutritional status of Daphnia pulex fed Aphanizomenon flos‐aquae1
Authors: Holm Nancy Peterson , Shapiro Joseph
Published: April 2010

The usefulness of the lipid index to determine the nutritional adequacy of Aphanizomenon flos‐aquae for Daphnia pulex was assessed. Lipid reserves, growth, survival, and reproduction of animals fed A. flos‐aquae and other foods were monitored. Lipid reserves were a good indication of the nutritional state of animals fed the different diets and were totally depleted in those fed A. flos‐aquae or not fed. Growth, survival, and reproductive success paralleled the magnitude of the lipid index. Aphanizomenon flos‐aquae was not toxic but was inadequate by itself to sustain D. pulex.
Phosphorus versus nitrogen limitation in the marine environment1
Authors: Smith S. V.
Published: April 2010

Limnological and marine geochemical opinion favors phosphorus limitation of organic production in aquatic environments, while marine biological opinion favors nitrogen limitation. Clues in the literature and nutrient budgets for selected marine ecosystems suggest that phosphorus vs. nitrogen limitation is a function of the relative rates of water exchange and internal biochemical processes acting to adjust the ratio of ecosystem N:P availability.
Estim ation of intracellular carbon and silica content of diatoms from natural assemblages using morphometric techniques1
Authors: Sicko‐Goad Linda M. , Schelske Claire L. , Stoermer Eugene F.
Published: April 2010

Electron microscopic morphometric techniques were used to measure accurately the cytoplasm and frustule volumes of 12 naturally occurring planktonic diatoms in the Laurentian Great Lakes. In addition, cytoplasm volumes were measured in 6 other algal species. Estimates of carbon content were then made by converting measured cytoplasm volumes to carbon biomass. From these measurements and conversions, the average percent carbon by dry weight was found to be 19% (range 10–30%) for diatoms and 35% (range 29–43%) for the nondiatom species. These values are lower than those previously reported. This is probably due to two facts: our estimates do not include extracellular carbon that may be associated with the cells, and vacuole relative volume (% of total cell volume) ranged from 22 to 70% in diatoms and 2 to 29% for nondiatoms. The carbon content of cells with lower vacuole volumes more closely approximate those previously reported. Our estimations of percent silica by dry weight of diatoms averaged 60% (range 40–78%). Our values for silica content are closer to those reported for naturally occurring populations than to those for cultured populations.
Effects of sediment transport on deposit feeding: Scaling arguments1
Authors: Miller Douglas C. , Jumars Peter A. , Nowell Arthur R. M.
Published: April 2010

At least five dimensionless variables are needed for dimensional analysis of an individual surface‐deposit feeder using particles containing microbial food both locally produced (by in situ growth) and advected (via sediment transport). From scaling arguments which provide the relationships among these variables, it is apparent that food availability is determined primarily by the ratios of geophysical sediment transport rate into the particle pool from which the animal feeds to its ingestion rate, and of particle residence time in the feeding pool to the microbial doubling time. Increasing sediment transport can either increase or decrease local food availability. Transport patterns beneath waves have dramatic effects: wave mixing makes available to the animal particles which otherwise would be literally out of reach. Specialization on advected particles and reliance on microbial gardening are favored under different environmental conditions, specified in terms of dimensionless ratios. The scaling model also places previous models of deposit feeding in an environmental context. It contrasts with an alternative, nutrient spiraling approach in having a basis in natural selection for its optimization arguments.
Relationships between phosphorus loading and trophic state in calcareous lakes of southeast Wisconsin
Authors: Stauffer Robert E.
Published: April 2010

The relationships among external phosphorus loading, lake phosphorus concentrations, and indices of lake trophic state are investigated for four calcareous and one noncalcareous lake in southeast Wisconsin. The total P and molybdate‐reactive P concentrations during winter and spring overturn are significantly higher in the calcareous lakes than predicted by models based on regional studies of Canadian Shield (ELA) lakes and the central New York Finger Lakes. The calcareous Wisconsin lakes have relatively low phosphorus retention coefficients and are eutrophic despite their low or only moderate external P loadings. By contrast, noncalcareous Devils Lake is oligotrophic; it is also adequately represented by the ELA loading vs. response equations.

The calcareous Wisconsin lakes and edaphically similar Lake Minnetonka, Minnesota, have lower epilimnetic chlorophyll concentrations in summer than predicted by the Dillon and Rigler equation (based on lake mean total P at spring overturn). Because these stratified lakes are frequently phosphorus‐limited in midsummer, the failure of the Dillon‐Rigler model may be related to seasonal cycles of mixed‐layer concentrations of total P (and SRP) and also to the seasonal patterns of loading. From other studies I suggest that these observations may be part of a larger edaphic pattern related to low phosphorus binding tendencies of certain calcareous lake sediments.
Tissue condition and growth rate of corals associated with schooling fish1
Authors: Meyer Judy L. , Schultz Eric T.
Published: April 2010

Juvenile french and white grunts (Haemulon flavolineatum and Haemulon plumieri) form diurnal resting schools over colonies of Porites furcata and Acropora palmata in St. Croix. We studied the effect of these grunts on the tissue composition and growth rate of corals, Porites furcata colonies with grunts had significantly more tissue cm−2, N cm−2 and zooxanthellae cm−2 than colonies without grunts. Acropora palmata colonies with grunts also showed elevated amounts of N cm−2 and P cm−2. Seasonal changes were also observed in these parameters and in coral growth rates and skeletal density, apparently related to light availability. Several measures of coral growth rate were significantly greater in P. furcata colonies with grunts. Grunts were removed from two colonies, and growth rates before and after removal were compared to rates in reference colonies. Before removal most growth rate measures were greater in the colonies with grunts; after removal growth rates were lower or not significantly different. These data demonstrate that schools of resident fishes can stimulate coral growth, perhaps by providing nitrogen supplements.
Control of Keratella populations by interference competition from Daphnia1
Authors: Gilbert John J. , Slemberger Richard S.
Published: April 2010

The cladocerans Daphnia galeata mendotae and Daphnia rosea inhibit population growth of the rotifer Keratella cochlearis even when shared food is abundant. Keratella swept into the branchial chamber of Daphnia may be immediately killed, mortally wounded, or lose attached eggs before or while being rejected. The chance of a Keratella being injured decreases with its age and increases with its retention time in the chamber. Such mechanical interference competition, described for the first time among zooplankton, may be very important in controlling natural populations of some rotifers.
Photosynthesis, photorespiration, and productivity in Lemna minor L.1
Authors: Filbin Gerald J. , Hough R. Anton
Published: April 2010

The roles of aqueous vs. atmospheric CO2 fixation, photorespiration, dark respiration, and organic release in the primary productivity of Lemna minor L. were investigated experimentally in field populations and in the laboratory. The mean rate of net photosynthesis through the growth season was 2.48 mg C g−1 h−1 during which an average of 86% of carbon fixed was from aqueous inorganic carbon. Seasonal variations in photosynthesis correlated principally with light intensity and temperature. Presence of photorespiration was suggested by early afternoon depressions of photosynthesis, by experimental enhancement and inhibition of photosynthesis with low and high oxygen, respectively, and by enhancement of light:dark respiration ratios with high oxygen. However, under natural conditions L:D ratios were below unity most of the time, and CO2 loss in the light was never >4% of photosynthate fixed per hour. Experimental enhancement of photorespiration with oxygen was never as great as the inhibition of photosynthesis at comparable oxygen concentrations. Although plants exhibited a low CO2 compensation point and high light and temperature optima, photosynthesis enzymology and fixation products indicated that C4 photosynthesis was not a significant factor in maintenance of the low photorespiration rates.
Does settling seston release soluble reactive phosphorus in the hypolimnion of lakes?
Authors: Gächter René , Mares Antonin
Published: April 2010

Organic material collected with sediment traps at depths of 20, 40, and 60 m in mesotrophic, phosphorus‐limited Lake Lucerne was decomposed aerobically at a rate of about 0.01 day−1 at 6°C. However, this material is not a source, but rather a sink, for soluble reactive phosphorus (SRP). As a consequence, during stratification, in the upper part of the hypolimnion concentrations of oxygen and SRP decrease simultaneously, and the ratio POC:PP (particulate organic carbon: particulate phosphorus) decreases significantly with increasing sampling depth and hence with increasing age of the seston. Once deposited at the aerobic sediment surface, the particulate matter continues to accumulate SRP.

Since settling particles and the aerobic sediment surface both act as sinks for SRP, anaerobic subsurface sediments are the only possible source for the SRP accumulating in the hypolimnion during summer stagnation. The aerobic sediment layer may however become an apparent source for SRP if the supply from deeper anoxic sediments exceeds its biological‐chemical sorption capacity.

Based on these observations and on additional information from the literature it is hypothesized that in phosphorus‐limited lakes decomposing organisms do not release, but rather take up, SRP while mineralizing phosphorus‐poor organic material.
Effects of pH and plant source on lignocellulose biodegradation rates in two wetland ecosystems, the Okefenokee Swamp and a Georgia salt marsh1,2,3
Authors: Benner Ronald , Moran Mary Ann , Hodson Robert E.
Published: April 2010

The microbial mineralization of synthetic [14C]lignin, specifically radiolabeled [14C‐lignin]‐lignocellulose and [14C‐polysaccharide]‐lignocellulose from a variety of aquatic herbaceous and woody plants was investigated in water and sediment from a salt marsh on Sapelo Island, Georgia, and from the Okefenokee Swamp, an acidic peat‐forming freshwater swamp in southern Georgia. Rates of microbial degradation of lignocellulose were depressed in the Okefenokee relative to those in the salt marsh. About 50% of the difference in mineralization rates was attributable to the low ambient pH (3.9) of Okefenokee water relative to the pH of salt marsh water (pH 7.1). Rates of mineralization of the lignin component of lignocellulose were only minimally affected within the range of pH 4–8, whereas mineralization of the polysaccharide component increased severalfold with increasing pH. Differences in the biodegradability of the various lignocelluloses were also observed; lignocelluloses from herbaceous plants were mineralized several times faster than lignocellulose from wood.
Experimental manipulation of nutrients and water in a freshwater marsh: Effects on biomass, decomposition, and nutrient accumulation
Authors: Bayley Suzanne E. , Zoltek John , Hermann Albert J. , Dolan Thomas J. , Tortora Louis
Published: April 2010

Experimental freshwater marsh plots (2,000 m2) received 9.6, 3.7, and 1.5 cm wk−1 of treated sewage effluent and the control plot received 4.4 cm wk−1 potable water during a 2‐year study. Surface water elevation above the peat substrate averaged 0.2 m in the second year. During the first year the marsh surface remained dry. Application of treated effluent increased net primary production only during the dry year. During the wet year there was no significant difference between the highest effluent plot and the control plot in aboveground biomass, or in phosphorus content in the aboveground live or dead vegetation and in the belowground vegetation. Based on the 2 years of the study, a natural increase in water level above the marsh surface had the same effect on the marsh production and nutrient accumulation as did application of 42 g P m−2 yr−1 in treated effluent. This was presumably due to the release of P from the peat substrate under flooded conditions.
Diel migrations of a zooplanktivorous fish (Menidia beryllina) in relation to the distribution of its prey in a large eutrophic lake1
Authors: Wurtsbaugh Wayne , Li Hiram
Published: April 2010

Diel changes in the distribution of the tidewater silverside (Menidia beryllina) and its prey were measured in Clear Lake, California, a large, shallow, eutrophic lake. Zooplankton prey densities were low in the littoral zone, but increased rapidly to near peak abundances 50–200 m from shore. Gill netting, trawling, and visual observations showed that tidewater silversides migrated both horizontally and vertically to feed in areas of high zooplankton abundance. At night the fish concentrated near shore and did not feed. At dawn (8 × 108−2 × 1010 photons cm−2 nm−1 s−1) the fish migrated lakeward at least 50–1,000 m, and littoral abundance decreased from more than 100 m−2 to only 0.1 m−2. The migration preceded the initiation of feeding by 30–60 min. After feeding 2–4 h, the fish returned to the littoral zone and swam rapidly (6–11 body lengths s−1) parallel to shore in narrow, continuous schools until resting aggregations formed. The fish returned to shore before they were satiated, perhaps to balance predation losses in offshore areas against foraging gains. A second period of offshore activity and feeding occurred in the afternoon and evening.
The fauna associated with drift algae captured with a plankton‐mesh purse seine net1
Authors: Kingsford M. J. , Choat J. H.
Published: April 2010

A plankton‐mesh purse seine used to encircle drift algae in open coastal waters was compared with seines in open water and conventional ichthyoplankton hauls. Densities of small fish and invertebrates were higher in association with drift algae than in open water. Most fish that occurred with drift algae were well pigmented. The fauna of drift algae differed from that of attached algae. Large numbers of epiphytic animals vacated attached algae which were experimentally detached from the substratum. The fauna on drift algae, therefore, is largely the result of colonization from open water. Fish and invertebrates were quickly attracted to clumps of experimental algae that were left to drift. This suggested that drifting algae may quickly influence the distribution of animals in open water.

Appreciable quantities of drift algae may influence the survivorship and recruitment processes of species which associate with algae during the planktonic phase of their life cycles.
The nutrition of radiolarians: Trophic activity of some solitary Spumellaria1
Authors: Swanberg Neil R. , Anderson O. Roger
Published: April 2010

Four species of radiolarians were kept in the laboratory under different feeding regimes. Spongodrymus sp. and two species of Thalassicolla showed no difference in survivorship between herbivorous, carnivorous, omnivorous, or nonfed conditions as long as they were kept in the light. The longest surviving individuals of the three species lived 32, 44, and 34 d. All these species bear copious numbers of algal symbionts, suggesting a significant algal role in host nutrition. A fourth species, Physematium muelleri, survived significantly longer on an omnivorous diet and was found to feed omnivorously in nature, with a diet reflecting the locally available microplankton.
Growth dynamics of Olisthodiscus luteus in outdoor tanks with flowing coastal water and in small vessels
Authors: Honjo Tsuneo , Tabata Kenji
Published: April 2010

Growth rates and periodicity of division of Olisthodiscus luteus were studied in outdoor tanks provided with a continuous flow of coastal water carrying a low density of wild plankters including O. luteus, during summer in 1981–1983. Cells collected from the tanks were individually cultured in small tissue culture chambers in the laboratory to observe growth rates and periodicity of division. A portion of an O. luteus patch on the wall of the tank was also cultured in a 1,000‐m1 volumetric flask hung in the tank. High growth rates, 2.0–5.0 div d−1, were observed in the tank. There was a strong tendency for large cells to dominate in the tank at the beginning of their fast growth phases and to be replaced by small cells toward the end of these growth phases. In small chambers O. luteus attained a growth rate of 3.3 div d−1; growth rates of large cells inoculated into these chambers were much higher than those of small cells. Growth rate in the flask was 2.3 div d−1. Olisthodiscus luteus showed a great preference for dark‐associated cell division. An apparent reciprocal codominance was observed between O. luteus and diatoms in the tank.
Lack of an effect of light on methylamine uptake by phytoplankton1
Authors: Balch William M.
Published: April 2010

Light‐dependent ammonium up take was studied with an analogue of ammonium, methylamine. This analogue is nonassimilable by phytoplankton so far examined; a low percentage is incorporated into macromolecules, so that the uptake or membrane transport process can be measured with little complication from assimilatory process. Single label incubations ([14C] methylamine) and dual label incubations ([3H] methylamine and [14C]bicarbonate) were used to show that there is no light‐dependent MeA uptake in an oceanic diatom, dinoflagellate, coccolithophorid, or in natural populations (particles > 1‐µm diam).
A new bell jar/microelectrode method to measure changing oxygen fluxes in illuminated sediments with a microalgal cover1
Authors: Lindeboom Han J. , Sandee Adri J. J. , Driessche Hetty A. J. de Klerk‐v.d.
Published: April 2010

Primary production of microalgae is usually measured by subtracting the recorded oxygen release in bell jars over lighted sediments from those over darkened sediments. We show that the oxygen uptake in illuminated sediments is higher than in dark sediments, indicating that past measurements have underestimated production and mineralization rates (for our system by a factor of 1.2–1.3). We introduce a combined bell jar/microelectrode method to measure in situ primary production, mineralization, and apparent diffusion coefficients in sediments with an active population of benthic microalgae.
Factors controlling the concentrations of soluble phosphorus in the Mississippi estuary1
Authors: Fox Lewis E. , Sager Shawn L. , Wofsy Steven C.
Published: April 2010

Sediments from the Mississippi River estuary were suspended in solutions with a range of salinities and various initial concentrations of phosphate. After 42 days the suspensions had nearly uniform values for the ion activity product of calcium times biphosphate, [Ca2+] [HPO42−] ≈ 10−9 M2. Similar values were observed for this ion product in the Mississippi River and in the upper estuary, suggesting that the concentration of soluble phosphorus may be controlled by an equilibrium with sedimentary material. The data are consistent with a mechanism where soluble phosphorus is controlled by hydrolysis on the surface of hydroxyapatite particles:

urn:x-wiley:00243590:media:lno19853040826:lno19853040826-math-0001

Phosphorus levels in the lower estuary are controlled primarily by dilution with low‐nutrient waters from the Gulf of Mexico.
Analyses of the in situ growth rates of Cryptophyceae by use of the mitotic index technique
Authors: Braunwarth C. , Sommer U.
Published: April 2010

Growth rates of Rhodomonas minuta v. nannoplanctica and Cryptomonas ovata were estimated by determining the fraction of cells undergoing cell division during 24 h. Acetocarmine was very useful for identifying stages of division (especially double nuclei). Division stages of R. minuta were found in Lake Constance during the night over a period of 16 or 17 h, of C. ovata over almost the entire 24‐h cycle. A comparison of potential growth rates with observed changes in population density indicates that the higher temporal variability of loss rates is more influential for changes in population size.
The effect of redox changes on the magnetic susceptibility of sediments from a seasonally anoxic lake
Authors: Hilton J. , Lishman J. P.
Published: April 2010

Sediments from Esthwaite Water, U.K., were allowed to oxidize while the magnetic susceptibility (MS) was recorded. The MS was reduced in the oxidized sediment more than in anoxic controls. The mineral responsible for these changes is formed by a diagenetic process and is probably a crystalline iron sulfide.
The rise and decline of a bloom of halobacteria in the Dead Sea1
Authors: Oren Aharon
Published: April 2010

A massive bloom of halobacteria that had developed in the upper water layers of the Dead Sea in summer 1980 together with a bloom of the unicellular green algae Dunaliella was present for more than 2 years. Simulation experiments performed in ponds in the Dead Sea area showed that the availability of phosphate, the extent of dilution with less saline water, and the availability of a suitable carbon source determine the extent of the development of halobacteria in Dead Sea water.

The number of particles resembling bacteria per milliliter of surface water decreased more than fivefold between November and December 1982, while the particulate protein decreased to below detection limits. This sudden decrease was correlated with a change in the physical structure of the water column from stratification to overturn.
Intrusions of outer shelf and slope water within the nearshore zone off Long Island, New York1,2
Authors: Churchill J. H.
Published: April 2010

From 1974 through 1978 studies were made of temperature, salinity, and water velocity, by hydrographic surveys and from moored instruments, in the waters within 15 km of the southern Long Island coastline. Data of late summer reveal frequent intrusions of anomalous water which appear to be of slope or outer shelf origin. Three intrusions of notably differing character are described. Two occurred at middepth, within the pycnocline. Concurrent hydrographic and current meter data suggest that these water masses were transported shoreward due to circulation forced by wind stress and by longshore density gradients. The third intrusion was initially observed near the surface and was of anomalously high temperature. Its T/S relation was similar to a warm and salty bolus detected 12 days earlier in the midshelf region. Hydrographic data suggest that this bolus may have been a detached parcel of slope water. Such intrusions may commonly occur during summer and fall and may be related to the appearance of tropical fish in the Long Island vicinity during these seasons.
Nitrogen uptake by natural populations of phytoplankton and primary production in the Pacific Ocean: Regional variability of uptake capacity1
Authors: Kanda Jota , Saino Toshiro , Hattori Akihiko
Published: April 2010

Uptake of nitrogenous nutrients (ammonium, nitrate, and urea) and inorganic carbon by natural populations of phytoplankton in surface waters of the Pacific Ocean was measured by a 13C‐15N dual tracer technique. Regional variability of uptake capacity and its correlation with environmental parameters were examined. The uptakes proceeded linearly with time for at least 3 h. Half‐saturation constants for uptake of ammonium, nitrate, and urea were generally low (about 0.1 µg‐atom N liter−1). The maximum uptake rate of nitrate was well correlated with the uptake of inorganic carbon; these two rates expressed on a chlorophyll a basis were relatively lower at higher latitude stations. Maximum uptake rates of ammonium and urea clearly covaried with the ambient water temperature. The estimated turnover times of ammonium at subtropical and tropical stations ranged from 1 to 3 days. The contribution of uptake in the dark was larger at low latitude stations. Regional variation of uptake capacity is correlated with temperature and possibly light, but not with nutrient supply.
Secondary production of the harpacticoid copepod Paronychocamptus nanus in a brackish‐water habitat
Authors: Herman Peter M. J. , Heip Carlo
Published: April 2010

The secondary production of the harpacticoid copepod Paronychocamptus nanus (Sars, 1908) in a shallow, brackish‐water pond was estimated during spring and summer 1980. The population was sampled every 5 d. Production of copepodites and adults, calculated by the size‐frequency method, amounts to 1.91 g m−2 dry wt over the sampling period (March–November). Egg production is 1.23 g m−2; naupliar production is roughly 1.09 g m−2. The production efficiency (ratio of production to production plus respiration) of copepodites and adults is 0.37; for the total population it is 0.42. P : B of the population is 24.45 over the sampling period, or 3.2 per generation.
Particulate and optical properties during CaCO3 precipitation in Otisco Lake1
Authors: Weidemann Alan D. , Bannister T. T. , Effler Steven W. , Johnson David L.
Published: April 2010

In late June 1983, Secchi depth d was 3.5 m and the vertical attenuation coefficient K was ≤ 0.5 m−1 in Otisco Lake. By 2 August, near the peak of a “whiting,” the values were 1.4 m and 0.64 m−1, and calcium‐containing, acidlabile particles >4 µm comprised ∼ 65% of total analyzed inorganic particles. From measured values of K and of the reflectance ratio R, the volume‐scattering coefficient b was calculated to be 2.88 m−1 and the volume absorption coefficient a, 0.31 m−1. Turbidity measurements confirmed the value of b and indicated ∼ 60% of the value was due to CaCO3. Of the value of a, water, Gelbstoff, and chlorophyll‐bearing particles contributed 54, 25, and 21%, respectively. The observed changes in d and K, from June to August, are theoretically consistent with an approximate doubling of b (due to CaCO3), with little or no change of a.
Assimilation efficiency in herbivorous aquatic organisms—The potential of the ratio method using 14C and biogenic silica as markers1
Authors: Tande Kurt S. , Slagstad Dag
Published: April 2010

A method for measuring assimilation efficiencies based on the change in the Si : 14C ratio in food and feces is proposed. Since this indicator method uses biogenic silica as the inert substance, the method is restricted to aquatic herbivores that consume food containing it. The method has been demonstrated on adult female Calanus hyperboreus fed the diatom Thalassiosira anguste‐lineata; assimilation efficiency decreases from 87.7 to 84.2% during a threefold increase in ingestion rate. The effect of errors in the estimate of Si : C ratios is slight when assimilation efficiency is high, but with decreasing values of assimilation efficiency, the sensitivity to errors in the estimates of silicon and carbon is increased.
An instrument for measuring small bottom currents in lakes1
Authors: Lemmin U. , Schurter M. , Imboden D. M. , Joller Th. , Abegglen H.
Published: April 2010

An instrument capable of recording bottom currents between 0.3 and 3 cm s−1 consists of an inverse pendulum with a slightly buoyant sphere and a light thread. At predetermined intervals a super‐8 movie camera operating in single‐frame exposure records the position of the sphere with reference to a fixed point. Illumination is provided by an electronic flash. The sphere excursions are digitized by a computerized digitizing table upon which each frame is projected. Calibration in a tow tank yields a power law between excursion and current speed. Deviation from the theoretical curve demonstrates that the drag forces on the thread cannot be disregarded. Overall accuracy of the instrument is ± 5% for speed, ±15° for direction. The instrument has been successfully deployed in several Swiss lakes.
The thermally forced circulation in a small, ice‐covered lake1
Authors: Rahm Lars
Published: April 2010

A simple, one‐dimensional model of the stratification in a small, ice‐covered lake is developed. It is shown that the heat flux from the sediments gives rise to a stable stratification and an organized circulation pattern. Data from a field study are compared with the predictions of the model. The good agreement found suggests that the buoyancy layer at the nonhorizontal boundaries is essential in modeling the thermal circulation in this type of lake.
Access pipes for multiple sampling under ice1
Authors: Baird Fay , Buso Donald C. , Hornbeck James W.
Published: April 2010

Access pipes are described for quickly collecting large numbers of samples from under the ice with minimal disturbance to the water column. We used a network of 35 such pipes on a small New Hampshire pond to follow temporal and spatial patterns of pH in winter and spring 1984. A network of pipes can be installed early in the season, used throughout the winter, and recovered after ice‐out.
A conceptual framework for predicting the occurrence of sediment focusing and sediment redistribution in small lakes
Authors: Hilton J.
Published: April 2010

Four processes are important in causing either sediment focusing or overestimation of sediment accumulation rates by traps, or both. A simple model to predict the occurrence of these events was constructed from published data for monomictic and polymictic lakes which contained sufficient detail to identify the major redistribution process. Boundaries between the regions where different mechanisms dominate were calculated from the expected mode of operation of the processes. The model was tested using sediment trap and accumulation rate vs. water depth data from the literature. Other published work is in general agreement with the predictions of the model.
Magnetic studies of erosion in a Scottish lake catchment. 1. Core chronology and correlation1
Authors: Appleby P. G. , Dearing J. A. , Oldfield F.
Published: April 2010

Magnetic susceptibility, 210Pb, 137Cs, 14C, and paleomagnetic secular variation are used to establish the chronology of sedimentation in a set of cores from Loch Frisa in western Scotland. The 14C dates obtained are not compatible with the chronology derived from all the other techniques and this is ascribed to inwash of “old” particulate carbon from the watershed. Central cores show little evidence of changes in sedimentation rate over the last 150 years whereas marginal cores contain evidence of major increases arising from ploughing and from drainage associated with catchment afforestation since 1935. The results illustrate the value of a multiple core approach to sedimentation and erosion studies even where complex lake morphometry precludes calculation of sediment budgets.
The effects of interaction of rate of food supply and population density on the bioenergetics of the opportunistic polychaete, Capitella capitata (type 1)1
Authors: Tenore Kenneth R. , Chesney Edward J.
Published: April 2010

Weight‐specific growth rates, population production, and trophic transfer efficiency (worm production/food supply) of different size classes of the polychaete Capitella capitata (type 1) were measured in the laboratory at 20°C under varying conditions of population density and rate of food supply (ration). A hyperbolic tangent function was fitted to the response of individual growth to unit nitrogen of food supply available per unit nitrogen biomass of worm (R : B̄). Maintenance ration, where growth = 0%, occurred at an R : B̄ = 0.08; i.e. a 0.08 g N daily ration of food was needed to maintain 1 g N biomass of C. capitata. Maximum daily individual growth rates of 21, 19, and 15% were predicted for small, medium, and large worms. The individual growth data were combined with long term‐population data collected at three food rations (50, 100, and 150 mg N m−2 d−1) to estimate long term population production. Changes in population density and the presence of meiofauna reduce the actual worm production for a given rate of food supply. Population production and trophic transfer efficiency changed dramatically as a function of rate of food supply, worm size, and biomass.
The horizontal heterogeneity of nitrogen fixation in Lake Valencia, Venezuela1
Authors: Levine Suzanne N. , Lewis William M.
Published: April 2010

Spatial and temporal variability of nitrogen fixation in Lake Valencia, Venezuela, were quantified on the basis of duplicate water samples collected from a depth of 0.5 m at 16 sites on 10 dates. The concentration of heterocysts in samples was determined and the samples were incubated with acetylene in situ. Two‐way ANOVA was used to separate the variance associated with site (fixed spatial patchiness), date (temporal variation), the interaction between site and date (ephemeral spatial patchiness), and sampling error. The nitrogen fixers in Lake Valencia are arranged in large (40–200 km2), ephemeral patches with distinctive fixation rates per heterocyst. Both variability in fixation per heterocyst and variability in heterocyst concentration contribute significantly to variation in fixation per unit volume of lake water, but the variability attributable to heterocyst abundance is greater. Spatial variation in fixation and heterocyst concentration exceeds temporal variation in these parameters, and the ephemeral component of patchiness is much greater than the fixed component.