bluuebunny/crossref_metadata_2025 huggingface dataset:
A nitrogen‐15 isotope dilution study of ammonium production and consumption in a marsh sediment1
Authors: Bowden William B.
Published: April 2010

Gross rates of ammonium production and consumption by microbes were estimated from isotope dilution of extractable 15NH4+ in surface sediment samples from a tidal freshwater marsh in Massachusetts. At 13°C gross ammonium production was 11.6 ± 2.9 nmol N · (cm3 fresh sediment)−1 · h−1. This rate equaled or exceeded gross ammonium consumption in the absence of plant root uptake [6.4 ± 4.0 nmol N ·( cm3 fresh sediment)−1 · h−1] so that ammonium accumulated linearly for 50–70 h in the sediment samples [5.2 ± 1.6 nmol N · (cm3 fresh sediment)−1 ·h−1]. In the field, this excess ammonium is presumably available for plant uptake. Ammonium production and consumption rates were highest in surface sediments and fell rapidly with depth. Temperature has a strong influence on both rates (Q10 = 2.6). Substrate quality and availability, both of which generally decrease with sediment age or depth, are probably more important than end‐product inhibition as rate‐controlling factors in these sediments. In particular, the relationship between ammonium production and consumption rates at different depths and sediment ligin content is clearer than between these rates and dry weight or ash‐free dry weight sediment.

The annual, net rate of ammonium production in the top 10 cm of unmixed, surface sediments was estimated from short term ammonium accumulation rates to be about 1.7 mol N · m−2. However, net ammonium production severely overestimated the true turnover time of ammonium as estimated by isotope dilution (5 days). Most important, while isotope dilution of ammonium is a good indicator of ammonium turnover rates, it may be a poor indicator of total nitrogen turnover in sediments (and so of total microbial activity) because it is insensitive to the nitrogen that microbes assimilate directly from the solid substrates to which they adhere.
Radiometric ages of brachyuran crabs from the Galapagos spreading‐center hydrothermal ventfield
Authors: Bennett J. T. , Turekian K. K.
Published: April 2010

The ages of four crab carapaces from the Galapagos spreading‐center hydrothermal ventfield were determined radiometrically using members of the U and Th decay chains. One animal had an age of 0.1 years and therefore had undergone molting just before collection; the other three had last molted 3–4 years before collection.
Needlelike projectiles observed issuing from lysing Trichodesmium (Cyanophyta) cells1
Authors: Borstad Gary A. , Borstad Lorraine E.
Published: April 2010

During cell lysis of the filamentous

cyanophyte Trichodesmium (=Oscillatoria), some cells (5–12 µm) produce 60‐µm‐long needlelike projectiles that exit the cells at rates up to 50 µm · s−1. We can offer no explanation for this previously unreported phenomenon but feel that it may be related to the fragility of the organism and the difficulty of culturing it.
Coral reef fish larvae: Patch size estimation and mixing in the plankton1
Authors: Victor Benjamin C.
Published: April 2010

The daily pattern of settlement of larvae of the bluehead wrasse, Thalassoma bifasciatum, onto a number of coral reefs was reconstructed with the daily otolith increment aging technique. Larvae settled simultaneously onto reefs within an area of about 1,000 km2. The planktonic patch size of bluehead wrasse larvae is inferred to be at least 46 km wide. Larvae settling onto a reef at the same time were not the same age, indicating that planktonic dispersal results in mixing of cohorts of larvae.
A subsurface flexible plastic enclosure for the in situ study of short term microbiological and chemical dynamics1
Authors: Burney Curtis
Published: April 2010

A simple nonmetallic device is described which allows the gentle enclosure of a few hundred liters of water from discrete depths in flexible plastic bags for in situ time‐series studies. The disposable bags close without rigid moving parts, remain in situ, and are pump‐sampled from the surface. The system can be deployed at sea and used for radiotracer experiments.
The marine biogeochemistry of selenium: A re‐evaluation1
Authors: Cutter Gregory A. , Bruland Kenneth W.
Published: April 2010

Vertical and horizontal profiles from the North and South Pacific Oceans demonstrate the existence of three species of dissolved selenium: selenite, selenate, and organic selenide (operationally defined). In surface waters, organic selenide makes up about 80% of the total dissolved selenium, selenite concentrations are uniformly low, and selenate concentrations rise with increased vertical mixing. The organic selenide maximum (thought to consist of seleno‐amino acids in peptides) coincides with the maxima of primary productivity, pigments, bioluminescence, and dissolved free amino acids. Deep ocean waters are enriched in selenite and selenate, while organic selenide is nondetectable. In suboxic waters of the tropical northeastern Pacific, organic selenide concentrations rise, while selenite values decrease. The downward flux of particulate selenium generally decreases with depth, and fluxing particulate selenium is found to be primarily in the (−2) oxidation state. These data allow a re‐evaluation of the internal biogeochemical cycle of selenium. This cycle includes selective uptake, reductive incorporation, particulate transport, a multistep regeneration, and kinetic stabilization of thermodynamically unstable species.
An individual particle analysis and budget study of Onondaga Lake sediments1
Authors: Yin Chengqing , Johnson David L.
Published: April 2010

The sedimentation of particles in Onondaga Lake, N.Y., was examined by scanning electron microscopy with automated image analysis and X‐ray energy spectroscopy (SAX), a technique of individual particle characterization. The composition of the particles coming into the lake and those present in the sediments was analyzed to calculate an annual sediment budget. An allochthonous sediment input of 21,800 tonnes·yr−1 and a sediment output of 3,300 tonnes·yr−1 were calculated from flow rates, sediment loads, and concentrations. A sediment mass budget yielded an autochthonous sediment formation of 15,900 tonnes·yr−1 and a net sedimentation of 34,500 tonnes·yr−1. Calcite particles comprised a majority of these autochthonous sediments and were found in the epilimnion. In addition, measurable amounts of iron sulfide were formed in the hypolimnion. Such budgets provide information, based on different particle classes, for studies of particle formation, transport, and deposition processes in limnetic environments.
Acidification of headwater streams in the New Jersey Pinelands: A re‐evaluation1
Authors: Morgan Mark D.
Published: April 2010

Previous reports of significant acidification of two headwater streams in the New Jersey Pinelands, presumably by acid deposition, are not supported by more recent data and a re‐evaluation of the original data. For one stream, McDonalds Branch, there has been no significant decline in pH from 1958 to 1982. For the other, Oyster Creek, a significant decline in pH was observed from 1965 to 1982, but the data indicate that a return to normally low pH levels following a short term watershed disturbance in the mid‐1960s is more likely to have been responsible than acid deposition.
Stable nitrogen isotopes in zooplankton: Some geographic and temporal variations in the North Pacific1
Authors: Mullin Michael M. , Rau Gregory H. , Eppley Richard W.
Published: April 2010

Copepods and chaetognaths from the Southern California Bight had higher 15N:14N ratios than did those from the North Pacific Central Gyre. Within the bight, zooplankters were more enriched in 15N when NO3− was the major nitrogenous nutrient for phytoplankton than at other times. The 15N enrichment is related to the degree of exchange of nitrogen between the euphotic zone and deeper water, and the low 15N:14N ratio in the central gyre is probably also related to the importance of nitrogen fixation. In contrast, little geographic or temporal variation was observed in zooplanktonic δ13C.
Evidence of ectocarpene and dictyopterenes A and C′ in the water of a freshwater lake1
Authors: Jüttner Friedrich , Wurster Karl
Published: April 2010

During a study of volatile organic substances in the waters of eutrophic shallow Federsee, ectocarpene and dictyopterenes A and C’ were detected for the first time in a freshwater lake. These substances were found in only one fortnightly sample during the year, indicating that marked short term chemical changes occur in small lakes. The origin of these substances could not be determined, although a common source from one organism seems likely due to their synchronous appearance and biosynthetic relationship.
Predation on jellyfish and their associates by seabirds
Authors: Harrison Nancy M.
Published: April 2010

Scyphozoan jellyfish are preyed on by 11 species of birds in the Bering Sea: Fulmarus glacialis, Puffinus griseus, Puffinus tenuirostris, Oceanodroma furcata, Larus hyperboreus, Rissa tridactyla, Rissa brevirostris, Uria aalge, Uria lomvia, Cyclorrhynchus psittacula, and Aethia cristatella. Parasitic amphipods on scyphomedusae also contribute to avian diets.
A method for nitrate and phosphate in saline water1
Authors: Tyree S. Y. , Bynum Mary Ann O.
Published: April 2010

Ion chromatography, in combination with sample pretreatment, is shown to be useful as a method for the determination of phosphate and nitrate at ppm levels in saline water samples.
A technique for the removal of estuarine seston from Nuclepore filters1
Authors: Tramontano J. M. , Church T. M.
Published: April 2010

A rapid, quantatative, and trace‐metal‐clean method of seston removal from Nuclepore filters by acetone soaking is described. The removal efficiency of this technique is > 97% by weight.
Chlorophyll budgets: Zooplankton grazing and phytoplankton growth in a temperate fjord and the Central Pacific Gyres1
Authors: Welschmeyer Nicholas A. , Lorenzen Carl J.
Published: April 2010

The processes controlling the daily production and fate of phytoplankton pigments were evaluated in a moderately productive fjord (Dabob Bay, Washington) and the oligotrophic open ocean (North and South Central Pacific Gyres). The processes included phytoplankton growth, macrozooplankton grazing, microzooplankton grazing, the downward vertical flux of pheopigments, photodegradation, dark degradation, cell sinking, cell senescence, and physical mixing. A model was constructed describing the dynamic budget of chlorophyll and pheopigments within the euphotic zone. The model provides estimates of phytoplankton growth, macrozooplankton grazing, and microzooplankton grazing based on field measurements of the vertical distribution of pigments, the vertical flux of pigments out of the euphotic zone, and the flux of solar radiation through the water column. The pigment‐specific rates (d−1) provided by the model are derived in situ without manipulation of either the phytoplankton or zooplankton, and the experiments are largely container‐free. Growth rates, averaged over the whole euphotic zone, varied seasonally in Dabob Bay (0.05–0.9 d−1) and ca. 67% of the total daily grazing rate was due to macrozooplankton herbivores. Phytoplankton growth rates, averaged over the whole euphotic zone, were ca. 0.2 d−1 in the oceanic gyres, regardless of season or location, and ca. 95% of daily grazing was due to microzooplankton herbivores. The model suggests that grazing and growth are in balance.
Regulation of cellular manganese and manganese transport rates in the unicellular alga Chlamydomonas1
Authors: Sunda William G. , Huntsman Susan A.
Published: April 2010

The cellular accumulation and uptake kinetics of manganese by Chlamydomonas sp. were studied in model chelate buffer systems. Cellular manganese concentrations and uptake rates were related to the computed free manganese ion concentration and were independent of the total or chelated manganese concentration. Cellular manganese was constant at about 1 mmol liter−1 of cellular volume at free manganese ion concentrations of 10−7.6−10−6.3 mol liter−1 and decreased below this range. Manganese uptake rates followed saturation kinetics and Vmax, but not Ks(10−7.0 mol liter−1), varied with the free manganese ion concentration in the growth medium. Vmax appeared to be under negative feedback control and increased with decreasing manganese ion concentration. Variations of up to 30‐fold in this parameter seemed to be instrumental in limiting the variation in cellular manganese to a sixfold range (0.18–1.0 mmol liter−1) despite a 1,000‐fold variation in free manganese ion concentration in the growth medium (10−9.5–10−6.3 mol liter−1).
Maerozooplankton of a deep sea hydrothermal vent: In situ rates of oxygen consumption1
Authors: Smith K. L.
Published: April 2010

Oxygen consumption rates of mixed macrozooplankton from the vicinity of a deep sea hydrothermal vent system were measured with a three‐chambered slurp‐gun respirometer manipulated by the submersible Alvin at one vent station, clam acres (2,615‐m depth), on the axis of the East Pacific Rise at 21°N. Diffuse warm‐water effluents (≤25°C) along crevices between pillow lava formations were densely populated with epibenthic megafauna. In sharp contrast, the surrounding nonvent area had similar physical features but few visible fauna. Four plankton collections were made in the vent area and two in the nonvent area on two separate dives. Vent and nonvent plankton were dominated, numerically and gravimetrically, by a calanoid copepod, Isaacsicalanus paucisetus. Abundance and biomass of the mixed plankton were highest over the vent area and decreased by as much as two orders of magnitude over the nonvent area. Although weight‐specific oxygen consumption rates of plankton from the vent and nonvent areas, measured at the same ambient temperature (1.6°C) were of similar magnitude (1.68–4.26 µl O2 mg−1 dry wt d−1), both were one to two orders of magnitude lower than published rates for surface‐water mixed plankton. Oxygen consumption rates per cubic meter ranged from 564.5 µl O2 m−3 d−1 at one vent site to 4.3 over the nonvent area. Vent and nonvent rates of oxygen consumption per cubic meter fall within the range of values previously measured for mixed macrozooplankton from surface waters to bathypelagic depths.
Migrating haemulid fishes as a source of nutrients and organic matter on coral reefs1
Authors: Meyer Judy L. , Schultz Eric T.
Published: April 2010

Juvenile french and white grunts (Haemulon flavolineatum and Haemulon plumieri) rest over coral colonies during the day and feed only at night in surrounding seagrass beds. We examined the amount of nitrogen, phosphorus, particulate organic carbon, and calories which these fishes deposited over the coral colonies that were their resting sites. Weight‐specific rates of nitrogen excretion by grunts decreased with increasing fish size. Rates of phosphorus excretion were not related to fish size. Excretory products were rich in nitrogen (molar N:P = 48), primarily ammonium, whereas fecal material was richer in phosphorus (N:P = 8). Feces leached over half of their phosphorus content within the first day. Half of the daily excretion and defecation occurred during the first 4 h after grunts returned to the reef, in which time they doubled the amount of NH4+ available to corals under calm conditions. Seasonal patterns of nutrient and particulate organic carbon (caloric) input to coral colonies varied with grunt biomass on the colony. The maximum input to colonies of Porites furcata from grunts occurred during August, which coincided with the time of highest coral growth rate. Grunts deposited an average of 164 and 251 mg m−2 d−1 of particulate organic carbon (feces) on the P. furcata and Acropora palmata colonies over which they rested, an energy supplement to the colonies of 0.8 and 1.2 kcal m−2 d−1. Rates of nutrient and organic matter input from grunts are comparable to or greater than rates observed in other naturally or artificially enriched ecosystems.
Factors regulating the reproductive phenology of Onychodiaptomus birgei (Copepoda: Calanoida)1
Authors: Walton William E.
Published: April 2010

Reproduction in a population of Onychodiaptomus birgei inhabiting a shallow montane pond consisted of alternating pulses of subitaneous and diapausing eggs. Unlike the single seasonal transition from subitaneous to diapausing eggs typical of many populations of diaptomids, female O. birgei tend to switch from the production of subitaneous eggs as they age regardless of time of year. The reproductive phenology of individual females was investigated in the laboratory to determine the proximate factors inducing diapausing egg production. Dissolved oxygen concentrations below the minimum observed in the field (<3 mg liter−1) had no effect on diapause induction. Photoperiod (L:D 8:16, 12:12, 16:8 h) had a detectable effect only at very high copepod densities (>1,000 individuals liter−1). High copepod densities increased and low food levels decreased the incidence of diapausing egg production. Increases in the proportion of subitaneous clutches in the field were preceded by peaks in fifth copepodid abundance. Field studies with in situ enclosures corroborated the finding that young females initially produce subitaneous eggs and then switch to diapausing egg production.
Physical, chemical, and biological consequences of episodic aluminum additions to a stream1
Authors: Hall Ronald J. , Driscoll Charles T. , Likens Gene E. , Pratt J. Michael
Published: April 2010

AlCl3 was added to a second‐orderroborated field results, added Al producing a 20% reduction in surface tension. We suggest that added Al may have associated with organic functional groups, rendering DOC more hydrophobic and less soluble. Some of these alumino‐organic substances subsequently may have accumulated at the air‐water interface. Terrestrial and aquatic invertebrate drift was also altered with elevated Al; we attribute drift to responses to chemical changes in the stream such as Al and H+ toxicity or to a physical change in surface film. stream to simulate episodic increases in Al concentration during acidic snowmelt. Significant decreases in pH and DOC and accumulation of foam at the surface (visible evidence of reduced surface tension) accompanied a stepwise increase in Al in the water. Laboratory experiments cor
Tritiated thymidine incorporation and the growth of heterotrophic bacteria in warm core rings1
Authors: Ducklow Hugh W. , Hill Suzanne M.
Published: April 2010

The time‐course of the incorporation rate of [methyl‐3H]thymidine ([3H]TdR) was established during 6–12‐h incubations of natural bacterial populations sampled from the surface layers of warm core Gulf Stream rings. Parallel estimates of changes in cell numbers were made in order to examine the relationships between TdR incorporation and population growth for oceanic bacterial populations. Our results indicate that a conversion factor of 4 × 1018 cells produced per mole of [3H]TdR incorporated yielded estimates of bacterial production which were within a factor of 2 or 3 of production estimates derived from changes in cell numbers in seawater cultures. We observed a significant, direct relationship between the initial rates of TdR incorporation per cell and specific growth rates and conclude that initial short term (15–45 min) assays of TdR incorporation are a valuable tool for studying bacterial production in oceanic waters.

In most incubations, the rate of TdR incorporation increased more rapidly than did cell numbers. Analyses of the time‐courses of TdR incorporation rates yielded estimates of specific growth rates for the actively dividing bacteria ranging from 0.08 to 0.51 h−1. Very large conversion factor values were derived from these data. The discrepancy between “growth” determined from TdR incorporation rates and total bacterial numbers in seawater cultures has not been observed in previous studies of coastal, estuarine, or lacustrine bacteria, but was a consistent feature of our studies on oceanic populations. We suggest that this may reflect the opportunistic character of oligotrophic bacteria. Rapid enhancement of TdR incorporation may indicate the capability of oligotrophs to grow rapidly when favorable conditions arise.
Vertical light attenuation and phytoplankton development in Lake Zürich1
Authors: Schanz Ferdinand
Published: April 2010

Many light‐depth profiles based on measurements of photosynthetically available radiation (PAR) in the 0–20‐m zone of Lake Zürich were analyzed with respect to phytoplankton development in the epilimnion and the thermocline. Variations in the average value of the vertical attenuation coefficient with time were closely related to variations in biomass. Inspection of the depth distribution of the natural logarithms of light intensity reveals several straight‐line segments. These correspond to zones with differing phytoplankton densities. During the spring bloom and the late summer phytoplankton maximum the biomass development can be followed in detail by interpreting the light‐depth curves. The results show that the vertical attenuation coefficient Kd(PAR) is influenced considerably by chlorophyll a; nonchlorophyll‐related organic and inorganic suspensoids, however, also seem to be of some importance during periods of low productivity.
Comparison between steady state and non‐steady state competition: Experiments with natural phytoplankton
Authors: Sommer Ulrich
Published: April 2010

Chemostat competition experiments with natural phytoplankton communities are compared to experiments in which either one (phosphorus) or two (phosphorus and silicon) key nutrients were added discontinuously at 1‐week intervals. In all types of experiments wide ranges of Si:P ratios were tested. Deviation from steady state was found not only to increase the number of coexisting species, but also to shift the regions of dominance of species and of higher taxa along the gradient of Si:P ratios. Pulsed nutrient addition was mainly to the advantage of green algae and to the disadvantage of diatoms.
Relationship of egg production of Calanus pacificus to seasonal changes in phytoplankton availability in Puget Sound, Washington1
Authors: Runge Jeffrey A.
Published: April 2010

Two methods of estimating daily, in situ egg production rate for Calanus pacificus, a planktonic marine copepod that releases its eggs directly into the sea, were developed. The model for both methods separates egg production rate into daily frequency of spawning (% day−1) and clutch size (eggs female−1). One method involves direct observations of spawning frequency and clutch size in a random sample of females held in controlled conditions for a 12–24‐h period immediately after capture. The second method involves a visual assessment of the ovaries of live or preserved females and uses the observation that egg laying in Calanus occurs at night to predict daily rates of spawning. The methods were used to examine the relationship between egg production rate and phytoplankton availability in two areas of Puget Sound with different seasonal patterns of phytoplankton abundance and size composition. Egg production rate was hyperbolically related to phytoplankton concentration. The results show the potential for factors influencing phytoplankton standing stock to influence the timing and magnitude of recruitment into Calanus populations.
Regulation of cladoceran filtering rates in nature by body size, food concentration, and diel feeding patterns1
Authors: Haney James F.
Published: April 2010

Relationships of body length (L) and filtering rate (F) of four Daphnia species and Holopedium gibberum were examined in situ during the day and night. During the day filtering rates were low and variable. At night filtering rates were higher and more consistent, with large animals filtering at disproportionately high rates. This resulted in regressions of log F vs. log L with intercepts, slopes, and correlation coefficients that were generally lower in the day than at night. Feeding rates (f) of Daphnia were calculated with seston <31 µm dry weight as a measure of food concentration (C). There were striking differences in the day and night response of feeding rates to food concentration. In the day Daphnia feeding rates increased slowly with increasing food level, reaching fmax at a relatively high incipient limiting food concentration (ILC), whereas at night feeding rates rose rapidly with food concentration to a maximum about twice the day fmax, at about half the day ILC. Multiple regression equations were developed to predict F from L and C. Exceptionally high filtering and feeding rates shortly after the upward migration of Daphnia may be due to a daily hunger cycle, although hunger alone does not account for the high filtering activity sustained throughout the night. Diel feeding patterns of large and small D. pulex were asynchronous, resulting in a reversal of the F:L relationship in the early morning when small animals filtered more rapidly than did large animals.
Synechococcus spp. as likely zeaxanthin‐dominant ultraphytoplankton in the North Atlantic1
Authors: Guillard R. R. L. , Murphy L. S. , Foss P. , Liaaen‐Jensen S.
Published: April 2010

We present four lines of evidence consistent with the suggestion of Gieskes and Kraay that the < 1‐µm particles observed in North Atlantic seawater associated with the carotenoid zeaxanthin are cyanobacteria (Synechococcus spp.). First, four quite different clones of marine Synechococcus contain zeaxanthin as their main carotenoid (50–80% of total carotenoids). Second, none of the other ultraplankters we have yet studied contains more than traces of zeaxanthin, though they contain other pigments potentially useful as chemosystematic markers. Third, none of these other “diagnostic” carotenoids was reported by Gieskes and Kraay. Fourth, the latitudinal gradient of zeaxanthin reported correlates well with our observations of the abundance of Synechococcus, but not of other ultraplankters in the North Atlantic. The circumstantial evidence is strong and merits direct confirmation.
Variations in Melosira islandica valve morphology in Lake Ontario sediments related to eutrophication and silica depletion1
Authors: Stoermer E. F. , Wolin J. A. , Schelske C. L. , Conley D. J.
Published: April 2010

Different types of valves are found in Melosira islandica populations preserved in Lake Ontario sediments. Three morphotypes were distinguished, the more coarsely structured of which are most abundant in assemblages deposited before 1840. Finely structured forms become more abundant upcore, reaching maximum abundance ca. 1962. These changes appear to be related to increased phosphorus loading and consequent silica depletion in Lake Ontario waters.
Control by organic coatings of the surface charge of estuarine suspended particles1
Authors: Loder T. C. , Liss P. S.
Published: April 2010

Particles in suspension in fresh, sea, and estuarine waters appear uniquitously to exhibit a small range of negative surface charge, as measured by electrophoresis. This uniformity is often attributed to the presence of organic or oxide surface coatings on the particles. Here we present experimental results which lend direct support to the idea of control of the particle surface charge by organic coatings. Iron oxide particles formed in situ in organic‐free water exhibit the expected positive charge but, on immersion in water containing its natural organic material, rapidly acquire the negative charge normally found for field samples.
Phosphorus limitation of lotic periphyton growth rates: An intersite comparison using continuous‐flow troughs (Thompson River system, British Columbia)1
Authors: Bothwell Max L.
Published: April 2010

Periphyton growth rates and relative degrees of phosphorus deficiency were compared with onsite, continuous‐flow troughs in three parts of the Thompson River system. Soluble reactive phosphorus (SRP) in the lower Thompson, North Thompson, and South Thompson Rivers averaged 3.4, 1.1, and 0.7 µg liter−1. Several physiological and chemical composition parameters ranked the degree of P deficiency in the rivers in the same sequence as did SRP. Among these were alkaline phosphatase activity, Vmax for 32PO43− uptake, and cellular N:organic P, Chl a:ATP, C:ATP, and C:organic P. Specific growth rates (µ) estimated by biomass accrual and by 14CO2 uptake usually, but not always, indicated higher µ with greater availability of P. However, relative specific growth rates (µ:µmax) consistently reflected the influence of P limitation. As assessed from N:organic P and by application of the Droop and Goldman‐Carpenter equations, µ:µmax was 0.8–0.9 at the lower Thompson, 0.3–0.6 at the North Thompson, and 0.0–0.3 at the South Thompson sites. Hence, periphyton growth rates in the lower Thompson River were near the maximum set by temperature and light at ambient SRP of only 3–4 µg liter−1. Evidence of P‐limited growth rates in the South Thompson and North Thompson Rivers was found at temperatures approaching 0°C.
Seasonal excretion rates of macrozooplankton from the Swedish west coast
Authors: Båmstedt Ulf
Published: April 2010

Weight‐specific excretion rates of ammonium, urea, inorganic phosphate, and total dissolved phosphorus by 19 species of zooplankton were measured during March–October 1981. Excretion rates of two copepods Calanus finmarchicus and Metridia longa showed similar trends during spring and summer, but diverged in autumn when C. finmarchicus had much lower rates. Excretion rates of most species were highest in spring and relatively low during summer. The high rates of excretion in spring corresponded with the spring phytoplankton bloom, but later blooms did not affect the excretion rates of the zooplankton. The average excretion rates varied considerably between species; ammonium from 3.2 to 68.1, urea from 0.9 to 6.3, inorganic phosphate from 0.3 to 8.2, and organic phosphorus from 0 to 3.5 nmol excreted per mg of body protein per hour. The average atomic N:P ratio ranged between 2.4 and 46.3, but was <20 for all species except Sagitta elegans. Estimation of the regenerative importance of nitrogen and phosphorus from macrozooplankton excretion indicated that between 4 and 50% of the phytoplankton nitrogen demands could be fulfilled, with the highest percentage demand being met during autumn. For phosphorus the range was 14–102% of the phytoplankton requirements.
Distribution and characteristics of carboxypeptidase activity in pond, river, and seawaters in the vicinity of Tokyo1
Authors: Hashimoto Shinya , Fujiwara Kitao , Fuwa Keiichiro , Saino Toshiro
Published: April 2010

Enzymatic hydrolysis of the peptide bond between glycine and tryptophan was measured in river water, pond water, and seawater near Tokyo. Enzymatic activities were in the range between 0.1 and 3 mU liter−1, 10–50% of the activity was due to cell‐free (dissolved) enzymes (1 mU expresses the rate of hydrolyzing substrate at 1 nM min−1 at 25°C). According to gel permeation chromatography, the dissolved activity included several macromolecules with molecular weights between 30,000 and 500,000 daltons. The horizontal and vertical distributions of this activity were measured in Tokyo Bay and the open sea, where an appreciable amount was detected even at 1,400‐m depth. Among various factors investigated (including pH, salinity, water temperature, metal ions, and phosphorus concentrations), total organic carbon, particulate organic carbon, and especially chlorophyll a were positively correlated to the enzymatic activity in Tokyo Bay. The slope of regressions of chlorophyll a on carboxypeptidase activity for individual sampling points showed that the activity per unit of chlorophyll a increased when the sampling station was closer to the open sea. Although whole protein molecules are not decomposed in the dissolved state, small peptides may be degraded by the free dissolved enzymes.
A diatom chronology for sediments in a high accumulation rate environment: Rupert Inlet, British Columbia1
Authors: Hay Alex E. , Waters Rosemary
Published: April 2010

Concentration profiles of large diatoms in gravity cores from the rapidly accumulating mine tailing deposit in Rupert Inlet exhibit variations with sediment depth which are ascribed to seasonal effects. Time‐series of near‐surface chlorophyll a measurements and phytoplankton cell counts, together with observations of an unusually massive bloom of Coscinodiscus gigas, are used to attribute peak concentrations of frustules of C. gigas, Coscinodiscus centralis, and Coscinodiscus radiatus in the sediments to late spring‐midsummer and early fall blooms of these species. Sediment accumulation rates estimated from the frustule concentration profiles range from 57 to 120 cm yr−1 and are similar to rates obtained from bathymetric and continuous seismic profiling surveys. From these rates it is inferred that very fine laminae (about 0.1 mm thick) may be tidally induced, and a rough estimate of 5 m d−1 is made for the in situ settling velocity of C. gigas.
Diel cycle of metabolism of phototrophic purple sulfur bacteria in Lake Cisó (Spain)1
Authors: van Gemerden Hans , Montesinos Emilio , Mas Jordi , Guerrero Ricardo
Published: April 2010

During a bloom of purple sulfur bacteria in Lake Cisó (Spain) data were collected on diel changes in the concentrations of sulfide, sulfur, glycogen, and poly‐β‐hydroxybutyrate (PHB), the rates of CO2 fixation and H2S oxidation, and the viability of cells along the vertical profile. During the day, sulfide oxidation resulted in the intracellular accumulation of sulfur and glycogen. At night, the concentrations of glycogen and sulfur decreased concomitant with the production of sulfide and PHB. Throughout the day, CO2 fixation and H2S oxidation were maximal in the zone of maximal population density (peak of the layer); however, in the top of the layer the specific rates were 2–6 times higher. The ratio of CO2 fixation to H2S oxidation, the sulfur content of the cells, and their specific density all indicated that sulfide was predominantly oxidized to sulfur. In the top and the peak of the layer cell viability was high but decreased rapidly with increasing depth. It was concluded that the existence of the bloom is the combined result of slow growth at the peak of the layer and a much faster rate of reproduction at the top of the layer. The cells at the top stored sulfur extensively and then sank to deeper layers where they could not oxidize the sulfur because of insufficient light.
Shifts in phytoplankton size structure and community composition during grazing by contrasting zooplankton assemblages1
Authors: Bergquist Ann M. , Carpenter Stephen R. , Latino John C.
Published: April 2010

Contrasting zooplankton assemblages consistently produced different compositional shifts in a phytoplankton community. Two experiments in 120‐liter enclosures were used to assess the responses of the algae to two different‐sized zooplankton communities. Grazing by a mixture of small copepods, Bosmina longirostris, and rotifers led to increased growth of phytoplankters with greatest axial linear dimensions <25 µm and ratios of surface area to volume <2.6, such as Chlamydomonas and Chlorococcales. Larger phytoplankton taxa such as Asterionella formosa, Closteriopsis longissimus, and Synedra sp. declined in the presence of small zooplankters. In contrast, a mixture of large zooplankters dominated by Daphnia pulex and Diaptomus oregonensis caused declines in phytoplankters with greatest axial linear dimensions <60 µm and ratios of surface area to volume <2.75, while larger algae such as Aphanocapsa and Dinobryon increased. Discriminant analyses showed that volume and surface area were the most effective characters for determining the response of algae to grazers. Zooplankton community structure was important in determining the responses of algal assemblages to grazing.
The life cycle and productivity of the amphipod Gammarus mucronatus on a northern Massachusetts salt marsh
Authors: LaFrance Katherine , Ruber Ernest
Published: April 2010

Gammarus mucronatus was the dominant amphipod found in the salt marsh pools of the Parker River National Wildlife Refuge. Densities were positively and highly associated with the presence of floating algal mat dominated by Cladophora spp.

Gammarus mucronatus is multivoltine with some overlap of cohorts. The first juveniles appeared in April, first adults matured in May at 3.5–4.5‐mm length (77% mature at 4.5 mm). Individuals from the last cohort, which began in November, matured at larger sizes (15% at 4.5 mm, 100% at 6.5 mm). The equation of egg number (N) against length of female (L) was N = 9.00L – 36.31 for overwintered females and N = 3.05L – 3.38 for the smaller summer females. Egg production was equivalent to 2.5 kcal m−2 yr−1.

The mean cohort interval was 112 days and mean cohort turnover rate (P : B) was 4.3. The two midsummer cohorts had the lowest growth efficiencies, 0.34 and 0.37. The first cohort, spanning 77 days (21 April–9 July), contributed the highest daily rates, more than half the annual production (8.7 g m−2), and the highest growth efficiency, 0.56. Several approaches to the calculation of annual production yielded a range of 12.4–15.8 g m−2 yr−1 dry wt with turnover rates also from 12.4 to 15.8.

Mean annual production was equivalent to 64.1 and respiration to 67.0 kcal m−2. When coupled with egg production this gave a mean growth efficiency of 0.50. When the values for respiration, growth, and reproduction are summed, the energy flow through G. mucronatus is equivalent to 5.8% of the net annual primary production in these pools.
Sulfur constituents and cycling in waters, seston, and sediments of an oligotrophic lake
Authors: David Mark B. , Mitchell Myron J.
Published: April 2010

Organic and inorganic sulfur constituents in streams, the water column, seston, and sediments of an oligotrophic Adirondack lake were measured for 2 years (1981–1983). Soluble organic S constituents (C‐bonded S and ester sulfate) were 1–18% of total S in streams, the water column, and lake outlet. Seston S (0.3–1.2% dry mass) in South Lake consisted of ester sulfate (44–59%), C‐bonded S (32–43%), sulfate (10–16%), and nonsulfate inorganic S (<2%). Rates of S deposition measured in sediment traps were highest after spring turnover. The organic matter content (52– 81% dry mass) of traps at 5, 8, and 15.5 m showed no significant differences.

Net mineralization of seston inputs was 26% based on mass balance calculations, with 43% of the ester sulfate input mineralized. Because most of the S input to the sediments was not mineralized, organic S accumulated and constituted the major (74% of total S) S component of the sediment.
Carbohydrate fluctuations, gas vacuolation, and vertical migration of scum‐forming cyanobacteria in fishponds1
Authors: van Rijn Jaap , Shilo Moshe
Published: April 2010

Natural populations of the scum‐forming cyanobacteria Oscillatoria, Spirulina, and Microcystis showed a diel vertical migration pattern in fishponds. This migration was governed by two factors, light and nitrogen. Light penetrates only into the upper layers of these shallow waterbodies, while combined nitrogen is detectable only in the pond sediment. Migration between these two layers was correlated with cellular carbohydrate accumulation at the top layer and its degradation at the bottom. Gas‐vacuole collapse was not mediated by turgor pressure and gas vesicles re‐formed at an extremely slow rate. Thus it seems likely that a change in ballast due to carbohydrate loading at the lighted surface and unloading at the dark, nitrogen‐rich bottom actively influences vertical migration.
Nitrogen fixation in an oligotrophic, saline desert lake: Pyramid Lake, Nevada
Authors: Horne A. J. , Galat D. L.
Published: April 2010

High rates of nitrogen fixation by a short‐lived but dense unialgal bloom of the planktonic blue‐green Nodularia spumigena provided 99.5% of the alga’s needs and 81% of Pyramid Lake’s annual total combined nitrogen input in 1979. The bloom was spatially very heterogeneous. Bloom size, duration, and presumably N2 fixation vary from year to year, but in 1979 about 900 t of nitrogen were fixed in 2 months in this large deep lake. The annual rate of N2 fixation was about 2 g m−2. In this year of low inflow the Truckee River provided 54 t of inorganic nitrogen and 83 t of organic nitrogen. Planktonic N2 fixation has not been measured during high inflow years and may have been small relative to river input. Lakewide average heterocyst to vegetative cell (h : c) ratios followed seasonal trends in N2 fixation, but synoptic samples showed only a weak relation between h : c and N2 fixation. N2 fixation was induced by low epilimnetic levels of inorganic nitrogen and ended before lake overturn in the fall. High rates of N2 fixation were confined to the upper 5% of the epilimnetic volume and thus occurred only in calm weather when Nodularia colonies floated to the lake surface. Access to freshly dissolved atmospheric CO2 may account for the near‐surface dependence, since the lake pH is normally about 9.2. We predict that Nodularia will not show the same degree of near‐surface dependence in near‐neutral lakes or in the ocean.
In vivo spectrophotometric analysis of photosynthetic pigments in natural populations of phytoplankton
Authors: Faust Maria A. , Norris Karl H.
Published: April 2010

An in vivo spectrophotometric method has been developed for rapid measurement of photosynthetic pigments of estuarine phytoplankton. A specially designed spectrophotometer recorded the diffuse transmittance spectra of phytoplankton assemblages concentrated on glass‐fiber filters. Spectral curves stored in a digital computer as log(l/T) were transformed to second derivative of log(l/T) for correlation with data on concentrations of pigments in extract. Linear regression analyses were used to test for the optimum wavelengths for predicting pigment concentration. The derivative treatment with a single‐term linear regression program combined provided equations giving correlation coefficients of 0.966 for Chl a, 0.943 for Chl c, and 0.964 for carotenoids. The advantages of the new method over solvent extraction are that natural samples are processed rapidly with a high degree of precision, no extraction of pigments is needed, several pigments are determined at the same time, and errors due to pigment loss in extraction methods are minimized.
Vertical flux and biogeochemical turnover regulate nutrient limitation of net organic production in the North Pacific Gyre
Authors: Smith S. V. , Kimmerer W. J. , Walsh T. W.
Published: April 2010

Water samples collected at a station in the North Pacific Gyre near Hawaii precisely define the temporal average vertical profile of dissolved inorganic and organic N and P (DON and DOP). DON and DOP concentrations decrease with depth. As shown by other studies, the regression of NO3− (with or without NH4−) vs. PO43− yields an approximately Redfield slope and a negative nitrogen intercept. If DON and DOP are included in the regression equation, the intercept approaches 0.

Vertical flux ratios of dissolved materials are calculated with a one‐dimensional diffusion model. Downward mixing of DON offsets about 6% of the upward NO3− flux; downward DOP mixing offsets only about 4% of the upward PO43− flux. Net production of particulate organic matter in the euphotic zone is N limited because of slow biochemical turnover of dissolved organic N relative to that of dissolved organic P and to downward mixing.
Small‐scale spatial heterogeneity in dissolved nutrient concentrations1
Authors: Smith David F.
Published: April 2010

Water samples collected <2 m apart and within seconds of each other from above a shallow‐water limestone reef system may have concentrations of dissolved organic nitrogen that differ by as much as three orders of magnitude. These differences are not due to analytical artifact, sampling method, or sample history, but reflect a structuring in the surface water. Variation between samples meant to be replicates is an inverse function of sample volume, both the mean values and the associated standard deviations decreasing sharply if sample volumes are increased from hundreds of milliliters to liters.
Regularly spaced rows of medusae in the Bering Sea: Role of Langmuir circulation1
Authors: Hamner William M. , Schneider David
Published: April 2010

In summer at night in the Bering Sea hydromedusae and scyphomedusae formed dense aggregations at the surface in convergences apparently produced by Langmuir circulation cells. During strong winds distance between parallel rows regularly exceeded 100 m; densities of medusae within rows reached 1,000 m−3. Physical and behavioral factors can increase spatial aggregation and thereby alter the rate of encounter of medusae with prey, predators, and competitors. The importance of Langmuir circulation in rough seas has been underestimated.
Small, aloricate ciliates as a major component of the marine heterotrophic nanoplankton1
Authors: Sherr Evelyn B. , Sherr Barry F. , Fallon Robert D. , Newell Steven Y.
Published: April 2010

Small, aloricate ciliates with equivalent spherical cell diameters <20 µm (biovolume <4,000 µm3) compose, on average, 4–57% of the total biomass of heterotrophic (apochlorotic) nanoplankton in diverse marine systems. Biomass production of nanoplanktonic ciliates in a southeastern U.S. estuary was also a significant part of the total production of heterotrophic microprotozoa. During summer in a salt marsh tidal creek, the production of small ciliates exceeded the production of heterotrophic microflagellates. Bacteria and coccoid cyanobacteria were frequently observed in the food vacuoles of the ciliates, while ingested nanoplanktonic algae were rarely seen. We suggest that small, aloricate ciliates can be an important component of the biomass of heterotrophic nanoplankton and deserve further attention as potential consumers of picoplanktonic cells in marine pelagic systems.
Capture of small cells by the copepod Eucalanus elongatus1
Authors: Price Holly J. , Paffenhöfer Gustav‐Adolf
Published: April 2010

Calanoid copepods feed by detecting and actively responding to relatively large individual cells and by accumulating smaller cells in a relatively passive manner by low amplitude flapping of the second maxillae. Films of Eucalanus elongatus passively collecting 13‐µm Thalassiosira weissflogii cells show that cells flow between the setae from the outer to the inner surface of the second maxillae. They are then funneled medially toward the setal tips and mouth, usually without adhering to the setae. The observed patterns of water flow contradict both the early descriptions of filter feeding and the expectation of negligible flow through setae in a low Reynolds number environment.
Enhancement of Mercenaria mercenaria densities in seagrass beds: Is pattern fixed during settlement season or altered by subsequent differential survival?1
Authors: Peterson Charles H.
Published: April 2010

The hypothesis that the passive hydrodynamic influence of projecting seagrasses on larval and postlarval settlement is sufficient to explain the higher Mercenaria mercenaria densities inside a seagrass habitat was tested by comparing the between‐habitat ratio of 0‐year‐class recruits after each of two settlement seasons to the between‐habitat ratio of densities of all older age classes. Differential survival after settlement must be invoked to explain at least half of the seagrass enhancement in Mercenaria population density.