bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbonate production by benthic Foraminifera and accumulation in the western Baltic 1
Authors: Wefer Gerold , Lutze Gerhard F.
Published: March 2010

Carbonate production and accumulation of the major species of calcareous benthic Foraminifera have been calculated for a defined area in the Bay of Kiel (western Baltic). Data from 440 surface samples and 6 cores show that carbonate production by Foraminifera is 10–33 mg·m−2·yr−1 in the turbulent zone and up to 3,117 mg·m−2·yr−1 in the basins. Epiphytic species only produce 2–4 mg·m−2·yr−1. Between 0 and 4% of the produced tests are accumulated; the rest are destroyed by mechanical breakage, dissolution, or ingestion by miacro‐ and meiofauna. Dissolution is not selective by species. Although few of the tests produced are accumulated, the sediment assemblage allows a realistic assessment of the paleoenvironment.
Nutrient exchange and oxygen consumption by deepߚsea benthic communities: Preliminary in situ measurements1,2
Authors: Smith K. L. , G. A. White , M. B. Laver , J. A. Haugsness
Published: March 2010

Rates of nutrient exchange and oxygen consumption by benthic communities were measured in situ at two deep‐sea stations in the NW Atlantic (2,200–2,750 in) by a grab respirometer operated from the submersible Alvin. Ammonia was regenerated but nitrate and phosphate were taken up by the sediments. Nutrient exchange rates and total oxygen uptake by the sediments were two to four orders of magnitude lower than rates at a shallow station in the NE Pacific. Observed nutrient exchange rates were significantly different from predicted rates. Compartmentalization of benthic community metabolism is possible with the grab respirometer which collects the sediment and biota on which the measurements are made.
A device to collect supernatant water for measurement of the flux of dissolved compounds across sediment surfaces1
Authors: Hargrave B. T. , Connolly G. F.
Published: March 2010

A bell jar chamber with a clock‐driven release mechanism was designed to collect samples of water trapped over undisturbed sediments. Samples taken at 3‐h intervals over 24 h were analyzed for dissolved oxygen, carbon dioxide, and total phosphorus and in situ flux across the subtidal sediment surface was calculated.
Influence of benthic macroinvertebrates on mixing of profundal sediments in southeastern Lake Huron1
Authors: Krezoski John R. , Mozley Samuel C. , Rohhins John A.
Published: March 2010

Vertical distributions of size classed benthic macroinvertebrates were investigated in centimeter‐thick sections of twelve cores from each of two stations in southern Lake Huron. Stations were selected on the basis of radioactivity profiles indicating surface sediment mixing to 3 and 6 cm. The corresponding occurrence of major taxonomic groups (amphipods and oligochaetes) to 2 cm at the first station and to 4 cm at the second suggests that these organisms play a significant role in sediment redistribution. Comparison of published tubificid defecation rates with sedimentation rates determined radiometrically indicates the extent to which benthic macroinvertebrates can mix surficial sediments.
Warm bottom water in Lake Michigan1
Authors: Marmorino George
Published: March 2010

A temperature increase of about 0.02°C was measured with a freely falling probe in the bottom 12 m at a 100‐m station in Lake Michigan in September 1977 and meter‐thick temperature inversions were observed higher in the water column. The origin of the warmer water is unknown.
Substrate size selection by stream invertebrates and the influence of sand
Authors: Williams D. Dudley , Mundie J. H.
Published: March 2010

A field experiment showed that benthic invertebrates in running water exhibit preferences for different substrate particle sizes. Maximum numbers and biomass occurred on medium gravel (24.2‐mm mean diam), whereas diversity was greatest on large gravel (40.8 mm). Individual species fell into four groups: upper, medium, and lower size preference, and no preference. The addition of a limited quantity of sand to medium gravel affected only a few species.
In situ measurements of clearance rates for the freshwater sponge Spongilla lacustris1
Authors: Frost Thomas M.
Published: March 2010

Clearance rates for Spongilla lacustris were determined in situ for three particle types. Mean values for Chlamydomonas reinhardti, Escherichia coli, and Rhodotorula glutinis are 0.055, 0.043, and 0.050 ml · s−1 · g−1 wet wt. Comparisons with a number of other freshwater filter feeders show that the rates for sponges are of similar magnitude.
Daphnia grazing on natural bacteria1
Authors: Peterson Bruce J. , Hobbie John E. , Haney James F.
Published: March 2010

Ten to sixteen Daphnia were placed in small vials filled with natural water from a lake and incubated for 0.5 to 2.0 h. The small (ca. 0.10 µ3) bacteria were counted on Nuclepore filters by an Acridine Orange direct count method with epifluorescence. Filtering rates were calculated from counts of bacteria before and after the incubations.

For D. pulex, D. middendorffiana, and D. longiremis the filtering rates ranged from 0.2 to 1.5 · ml animal−1 · h−1 depending on the size of the animal and temperature. Simultaneous comparisons with rates of filtering on larger yeast cells indicated that these bacteria were filtered at about 30% the rate for yeast.
Carotenoid interference in the spectrophotometry determination of chlorophyll degradation products from natural populations of phytoplankton1
Authors: Riemann B.
Published: March 2010

Pigments extracted from natural populations of diatoms showed increased absorption between 600–750 nm after acidification with HCl at concentrations above 3 × 10 M, both in 90% acetone and absolute methanol. This increase in absorption, due to spectral changes in fucoxanthin, made reliable spectrophotometric distinction between chlorophyll a and pheopigments impossible. Changes in absorption spectra of chlorophyll a, pheophytin a, diatoxanthin, and carotene were of minor importance. Corrections for chlorophyll degradation products should be made with care to ensure that the presence of pheopigment a is legitimate and not a function of the ratios of epoxidic carotenoids to chlorophyll a.
A rapid and precise method for determining sulfate seawater, estuarine waters, and sediment pore waters1
Authors: Hoioarth Robert W.
Published: March 2010

Sulfate can be rapidly and accurately measured by means of an indirect titration. Barium sulfate is precipitated in acid EDTA solution, the precipitate filtered and dissolved in an excess of EDTA at high pH, and the excess EDTA titrated with MgCl2. Interferences from chloride, iron, or phosphate are negligible. Sulfides may interfere, but there is a procedure to remove this interference. The method determines the sulfate concentration in 1.0 ml of seawater with a standard deviation consistently <0.5% of the mean determination of three replicates.
Microfluorometric method to measure ammonium in natural waters1
Authors: Gardner Wayne S.
Published: March 2010

Ammonium can be measured fluorometrically after a simple chromatographic separation from amino acids and reaction with o‐phthalaldehyde. The method (<0.5‐ml sample required) is sensitive down to 0.2 µm NH4+ in seawater. Fluorescence is proportional to concentration over the range of 0–100 µm NH4+ and analysis time is 6 min per sample.
Determination of submicromolar concentrations of ammonia in natural waters by a standard addition method using a gas‐sensing electrode1
Authors: Garside Christopher , Hull Gretchen , Murray Susan
Published: March 2010

A standard addition technique using a gas‐sensing electrode with a modified electrode filling solution provides a rapid and convenient method suitable for both field and laboratory measurement of ammonia. The method has a detection limit of 0.2 µM of NH3, a precision of ±0.1 µM of NH3, and no measurable salt error. Calibration is stable for a period of days and analytical rates of 15 samples per hour are possible.
Combat between predatory copepods and their prey: Cyclops, Epischura, and Bosmina1
Authors: Kerfoot W. Charles
Published: March 2010

Predatory copepods are not imprecise hunters: they are capable of sophisticated behavior. Pelagic species (Cyclops, Epischura) usually sense approaching prey from a distance and must judge approach angle and prey speed, reorient during attack, and often vary their handling responses. Below certain crucial sizes that trigger avoidance responses in the predator, attack distances are related to prey size and speed. Cyclopoids and predatory calanoids (Epischura) capture and handle prey differently, and the morphology of the first maxillae reflects these modes. Apparently, the coexistence of certain small‐bodied cladocerans (Bosmina, Chydorus) with predatory copepods results more from the evolution of effective defenses in the prey than from the clumsiness of the predator.
Predatory feeding behavior of a marine copepod, Labidocera trispinosa1
Authors: Landry M. R.
Published: March 2010

The behavior of Labidocera feeding on early developmental stages of five common species of planktonic calanoid copepods was investigated to determine its species‐specific impact on a mixed copepod community. Feeding rates on individual prey were not affected by prey density or the availability of alternate prey; threshold feeding behavior was not observed. Capture rates of naupliar prey of all species increase as a function of their size even though larger nauplii appear better able to avoid capture. In general, the ability of Labidocera to capture individuals of a prey species decreases abruptly after the prey develop to the copepodid stages. As a consequence of the limited susceptibility of copepodid stages to capture by Labidocera and higher feeding rates on larger nauplii, the predatory impact of Labidocera is greatest on the largest of the prey species.
Limnetic feeding behavior of juvenile sockeye salmon in Lake Washington and predator avoidance 1
Authors: Eggers Douglas M.
Published: March 2010

Patterns of limnetic feeding behavior (vertical movement, schooling, diel feeding chronology, zooplankton prey selectivity) of Lake Washington juvenile sockeye salmon are described. A general hypothesis to explain the relative fitness of alternative behaviorial decisions is presented. The limnetic feeding behavior of the salmon appears to minimize their vulnerability to predation by the visual piscivore, northern squawfish. Seasonal variation indicates that sockeye feeding behavior is a short term optimization process involving foraging success and encounters with northern squawfish. Lake Washington sockeye salmon can afford to spend a large amount of their time engaged in antipredator behavior at the expense of foraging success because Lake Washington is comparatively zooplankton‐rich and the energy demands of the fish can be met in short foraging periods. Sockeye in other less productive systems show a more aggressive exploitation of the zooplankton.
Comparison between five coexisting species of marine copepods feeding on naturally occurring particulate matter
Authors: Poulet S. A.
Published: March 2010

Grazing by five species of copepods on naturally occurring particles has been investigated over a 1‐yr period. The consumption of particles by each species was associated with changes in both total concentration and composition of suspended particulate material. All the copepods reacted similarly and simultaneously to the changes of the particle size spectrum by shifting their grazing pressure from one size range to another. They all behaved as opportunistic particle feeders, seeking and keeping track of the most abundant particles. No species seemed to behave as a selective grazer with respect to particle sizes. There were quantitative differences between the ingestion rates per body dry weight of the copepods, and the ingestion per body dry weight was inversely proportional to the body dry weight. The feeding behaviors of the species should lead to rather severe interspecific competition. The apparently sustained coexistence of the five sympatric species is attributable to several physical and biological mechanisms working simultaneously.
The importance of the time factor in the response of zooplankton to varying concentrations of naturally occurring particulate matter 1
Authors: Mayzaud Patrick , Poulet Serge A.
Published: March 2010

Over the course of a year a linear relationship was found between feeding rates of five species of neritic copepods and their probable food supply, the naturally occurring particulate matter. However, a saturation‐type curve was obtained when a range of food concentration was offered to Pseudocalanus minutus over a short period of time (18–20 h). Digestive enzyme levels of the copepod population were also found to vary linearly on a seasonal basis. The affinity (1/Km) appeared to vary with time, indicating acclimation in the digestive system. A new model, linear for variations of food concentrations over an extended period of time (weeks to a year) and curvilinear for variations over a time smaller than the one needed for acclimation, is developed.
Transport of particulate organic matter by bubbles in marine waters 1
Authors: Wallace Gordon T. , Duce Robert A.
Published: March 2010

Flotation experiments with surface marine waters collected from estuarine, continental shelf, slope, and open ocean waters showed that about half of the originally present particulate organic carbon and nitrogen was adsorbed and transported by bubbles to the surface froth. Recovery values were a function of primary production and other environmental parameters. In only one instance was there evidence of selective removal of particles with C:N ratios differing from those left behind.

The estimated open ocean transport of POC by bubbles was five times higher than an earlier estimate due to the unexpected efficiency of the flotation column at low concentrations of open ocean POC. Budget calculations indicated little or no conversion of dissolved to particulate organic carbon. Large macroscopic particles quickly formed in the froth produced by bubbling, an aggregation phenomenon which may be of importance in the transport of large particle POC to deep waters.
Production and release of N2O from the Potomac Estuary 1
Authors: McElroy M. B. , Elkins J. W. , Wofsy S. C. , Kolb C. E. , Durán A. P. , Kaplan W. A.
Published: March 2010

Measurements of dissolved O2, N2O, NH4+, NO2−, and NO3− are used to study the biogeochemistry of nitrogen in the Potomac River near Washington, D.C. The nutrient budget of the Potomac is dominated by sewage inputs from treatment plants at Blue Plains and Alexandria. Measurements taken in July and September 1977 indicate large supersaturated concentrations of N2O and exhibit significant short‐period variations over distances >40 km. Concentrations of N2O and O2 appear to be inversely correlated and there are indications that N2O may be produced primarily near the sediment‐water interface. Nitrous oxide is released to the air on a time scale of about 1 day and gas exchange may occur mainly in shallow embayments in response to turbulence associated with tidal currents. Release of N2O to the atmosphere takes place at a rate of about 103 kg·d−1 and may be attributed to prompt conversion to N2O of between 1 and 5% of the total nitrogen input.
Transport of nutrients and carbon from the Nanaimo River to its estuary 1
Authors: Naiman Robert J. , Sibert John R.
Published: March 2010

Over an annual cycle, concentrations of inorganic nitrogen, phosphorus, and organic carbon were measured slightly upstream from the confluence of the Nanaimo River, British Columbia, and its estuary. Inorganic nitrogen and phosphorus concentrations in river water are low most of the year and may not be important in supplying these nutrients to the estuarine mudflat. Large amounts of dissolved organic carbon (DOC) and fine particulate organic carbon (FPOC) are exported from the river to the mudflat (about 2,000 and 56 g C·m−2·yr−1), but the actual amount retained and utilized by the mudflat community is not known. Comparison with in situ primary production on the mudflat shows that fluvial DOC may be the greatest source of carbon to the system. A conceptual hypothesis is presented relating basin morphometry and retention structures to estuarine efficiency in retaining nutrient and carbon inputs.
Ferrous iron‐sulfide interactions in anoxic hypolimnetic waters
Authors: Davison W. , Heaney S. I.
Published: March 2010

Seasonal polarographic measurements of sulfide and ferrous iron concentrations in the hypolimnion of a thermally stratified lake show that the inorganic chemistry in the waters nearest the sediment is dominated by ferrous sulfide precipitation. There is no evidence for supersaturation or organic interactions. The solubility product for ferrous sulfide at 10°C and near zero ionic strength was 0.9–2.0·10−17 M2, which agrees with an independent laboratory determination for fine‐grained freshly precipitated FeS. Although the solution concentrations of iron II and carbonate suggest that ferrous carbonate precipitation may just be possible, analysis of the particulate matter gave no evidence for this.
In situ methane production in a small, hypereutrophic, hard‐water lake: Loss of methane from sediments by vertical diffusion and ebullition 1
Authors: Strayer Richard F. , Tiedje James M.
Published: March 2010

The rate and quantity of methane produced by sediments of Wintergreen Lake were estimated by separately measuring methane lost by ebullition using bubble traps and by estimating methane lost to the water column by diffusion. The maximum rates of methane loss by ebullition occurred in late summer and were 35 mmol·m−2·d−1 in 1972 and 37 in 1973. The average dissolved methane flux for 1972 was estimated to be in the range of 10–46 mmol·m−2·d−1. The minimum value was estimated by summing dissolved methane concentrations in the water column for each sampling date. The maximum value was estimated using the eddy diffusion coefficient of 4.9 × 10−3 cm2·s−1, calculated from the temperature method of Hutchinson. This methane diffusion rate was about two times the average rate of methane lost by ebullition (21 mmol·m−2·d−1) over the same time period. Dissolved methane was detected only in anoxic waters during summer stratification and within a meter of both the sediment and ice during winter. Ebullition also occurred during winter.
Consumption of dissolved methane in the deep ocean 1
Authors: Scranton Mary I. , Brewer Peter G.
Published: March 2010

Oceanic dissolved methane concentrations are normally in excess of atmospheric equilibrium values in surface waters but show a rapid decrease with depth. Deep North Atlantic waters have only ca. 30% of their atmospheric equilibrium values of methane and deep North Pacific waters have only ca. 10%. Methane consumption rates calculated from methane analyses and water mass ages derived from published data on 3H/3He ages, 14C ages, and model calculations show that both methane and oxygen are rapidly consumed in “young” water but, while oxygen consumption continues at a low rate throughout the deep ocean, methane consumption virtually ceases within about 100 years of isolation from the surface ocean.
Sessile bacteria: An important component of the microbial population in small mountain streams 1
Authors: Geesey G. G. , Mutch R. , Costerton J. W. , Green R. B.
Published: March 2010

Direct counts by epifluorescence microscopy demonstrated that epilithic bacteria were numerically more important than free‐floating bacteria in unpolluted mountain streams. Concentrations of sessile bacteria associated with the upper surfaces of submerged rocks coincided with fluctuations in epilithic algal biomass. Electron microscopy of thin‐section preparations of natural samples showed that the attached algae provided a surface for bacterial colonization. This close physical relationship between the bacteria and algae was mediated by a network of fibers which, in mass, appeared as a layer of slime covering the streambed. The relationship between sessile bacterial concentratons and epilithic algal biomass in one tributary suggested that, in some cases, factors other than epilithic primary production governed the attached microbial population.
Variation in sexual dimorphism in nonmarine Calanoid copepods and its ecological significance
Authors: Bayly I. A. E.
Published: March 2010

Significant differences exist in the degree of sexual dimorphism in a series of closely related nonmarine calanoid copepods. Strongest dimorphism is found in species that occur exclusively in temporary waters. No species known only from permanent waters is strongly dimorphic except where it typically occurs as the sole calanoid in such waters. It is suggested that, in situations where interspecific competition is likely to be minimal, pronounced sexual dimorphism enhances efficiency of food exploitation by allowing the consumption of an exceptionally wide range of particle sizes.
Trout predation and the size composition of stream drift 1
Authors: Allan J. David
Published: March 2010

Nocturnal drift of stream invertebrates is examined as a predator avoidance adaptation via the hypothesis that those taxa or growth stages which are large, and thus subject to intense predation relative to smaller forms, should be most strongly constrained to nocturnal drift activity. Smaller taxa or stages may be aperiodic or day active. Data from an alpine stream document for the abundant and widespread mayfly Baetis bicaudatus that, on a continuum from small to large size, the risk of predation increases while the propensity to drift during the day decreases. There is supporting and some contrary evidence from the literature for the generality of this pattern.
Size dependence of phosphorus and nitrogen subsistence quotas in unicellular microorganisms 1
Authors: Shuter B. J.
Published: March 2010

Literature values for the phosphorus and nitrogen subsistence quotas of several bacteria and unicellular algae are presented in a comparable form. Both of these parameters depend on cell size.
Copepod swarms: Attributes and role in coral reef ecosystems
Authors: Hamner W. M. , Carleton J. H.
Published: March 2010

Monospecific aggregations of copepods were observed and sampled from eleven coral reefs, two sea grass habitats, and several marine lakes in the Central and Northern Great Barrier Reef Provinces of Australia and in Palau, Western Caroline Islands. Acartia australis, Acartia bispinosa, Oithona oculata, and Centropages orsinii regularly occurred at swarm densities of from 500,000·m−3 (A. australis) to 1,500,000·m−3(O. oculata). During the day copepods swarmed over white sand on the lagoon side of windward reefs, adjacent to or downstream from isolated coral outcrops, with size of swarm dependent on size and shape of the nearby coral head. Swarms 1–2 m in diameter were common; they occasionally exceeded 30 m3. Seasonally these large swarms coalesced and carpeted the lagoon floor with copepods. In Palau O. oculata also swarmed near the surface in a continuous linear band in the solution notch that undercuts the limestone islands. Acartia bispinosa swarmed at the surface in open water in the marine lakes of Palau and over sea grass beds in the lagoon at low water. Swarming probably serves several adaptive functions, but protection from predators appears of major importance. Visual behavior and orientation to surrounding objects maintained swarm integrity, as did mechanical winnowing by currents. At night, swarms dispersed throughout the water column and swarming species sometimes dominated the nocturnal plankton within the reef lagoon. Previous investigations of coral reef zooplankton have not sampled swarming copepods properly and prior estimates of food available to the reef community must be re‐evaluated.
The adaptive significance of color polymorphism in two species of Diaptomus (Copepoda)1
Authors: Hairston Nelson G.
Published: March 2010

In the Lower Grand Coulee, Washington, Diaptomus nevadensis in Soap Lake contains larger amounts of the carotenoid astaxanthin than in Lake Lenore. During winter, Diaptomus sicilis contains larger amounts of pigment in both lakes, but in summer individuals from Lake Lenore are much reduced in pigment while those from Soap Lake are unchanged. The amount of astaxanthin might be a reflection of the amount of pigment in the copepods’ diet or might reflect the relative importance of selective forces acting for and against pigmentation. Seasonal variations in copepod carotenoid content did not correspond with variations in total lipid content. Algal abundance was measured by chlorophyll a and plant carotenoids correlated with copepod carotenoids only in the case of D. nevadensis in Soap Lake. The percent of D. nevadensis guts containing algae was correlated with their pigment content in both lakes. Visually oriented predators, such as damselfly nymphs from both lakes and salamander larvae from Lake Lenore, selected red copepods, but few predators from Lake Lenore contained D. nevadensis. Since members of this species were rare, the probability of finding a predator that had consumed one was low. When fed identical diets, copepods from Lake Lenore were a fifth to a thirtieth as efficient at assimilating carotenoid as those from Soap Lake. This supports the hypothesis that the pigment differences are the result of natural selection. Selective predation is implicated as the explanation for the small amounts of pigment in Lake Lenore copepods.
The relationship between pigmentation and reproduction in two species of Diaptomus (Copepoda)1
Authors: Hairston Nelson G.
Published: March 2010

Adult Diaptomus sicilis and Diaptomus nevadensis in two central Washington lakes show a seasonal range in body pigmentation: from high throughout the year to markedly seasonal with a winter and early spring peak. Both species have winter‐spring peaks in reproduction in both lakes. Pigment is accumulated by adult females and concentrated in their eggs and nauplii. During the day, the nauplii are at the surface of the lakes where visible light is intense, and it is suggested that the carotenoid functions as photoprotection. Seasonality of adult pigment content varies as a function of predation pressure. In a population experiencing little predation, adults are highly pigmented throughout the year; as predation pressure on the populations increases, the timing of pigmentation maxima contracts to the period of reproduction.
Bioenergetics of a stream “collector” organism, Tricorythodes minutus (Insecta: Ephemeroptera)1,2
Authors: McCullough Dale A. , Minshall G. Wayne , Cushing Colbert E.
Published: March 2010

The energy budget of a fine‐particle collector organism, Tricorythodes minutus Traver (Ephemeroptera: Tricorythidae), was determined under conditions (flow, substratum, temperature) representative of its natural habitat. Digestion time (gut clearance) was rapid (30 min). Ingestion values ranged widely: 33–220 µg dry wt·mg dry wt−1·h−1(= wW·h−1), depending on the type of food provided. Assimilation rates were lowest ∼2 µg ash‐free dry wt·mg dry wt−1·h−1 (= aW·h−1), with mixed diatoms, intermediate with the blue‐green alga Anabaena (∼23), and high with the blue‐green Lyngbya (∼61) and with a pure culture of Nitzschia (∼62). Assimilation efficiencies showed a much narrower spread, being 33, 34, and 57% for mixed diatoms, blue‐green algae, and Nitzschia. A mean respiration rate of 2.51 µl O2·mg dry wt−1·h−1 was derived for T. minutus at 20°C. Growth, estimated from length‐weight relationships, was 4.5 wW·h−1. The instantaneous growth rate for T. minutus (0.126) is higher than those reported for any other mayfly (0.034–0.060) except Tricorythodes atratus (0.153). Cast skins accounted for over 30% of the total production (G + Ex = 6.5 wW·h−1). Comparison with Stenonema pulchellum, the only other mayfly for which complete energy budget information is available, showed respiration rates to be similar and assimilation and growth of Tricorythodes to be 2.9 and 5.3 times higher. However, the major distinction between the two was the high ingestion rate for Tricorythodes compared with that for Stenonema (7 wW·h−1).
Biological interactions as determinants of distributions of benthic invertebrates within the substrate of stony streams
Authors: Peckarsky Barbara L.
Published: March 2010

Stainless steel screen cages were buried in the substrate of Otter Creek, Wisconsin, during spring 1976 and 1977 and the East River, Colorado, during summer 1977 and stocked with known densities of benthos, Cages were retrieved after 3 days of colonization and attrition from a given direction and species densities and distributions compared to those initially present. With increasing initial benthic density, the net change in numbers of invertebrates per cage decreased linearly, the net immigration decreased linearly, and the net emigration increased linearly. Benthic invertebrates preferred low density areas of substrate to high density areas of comparable physical‐chemical quality. Theoretical equilibrium cage densities indicated that given a consistent habitat, a consistent number and assemblage of benthic invertebrates will colonize. The most abundant species in both streams were categorized according to their observed immigration patterns as density‐dependent or density‐independent species; overall trends showed that most species were density‐dependent.
Effect of hydrologic fluctuations on the transport of fine particulate organic carbon in a small stream1
Authors: Bilby Robert E. , Likens Gene E.
Published: March 2010

Investigations into the pattern of fine particulate organic carbon (FPOC) concentration and export during periods of rapidly changing discharge in a small, mountain stream revealed maximum values before peak discharge. FPOC was washed out of the stream very rapidly with increasing discharge. A peak in FPOC concentration also occurred at the onset of rainfall during summer storms, before discharge began to rise; rainfall itself rather than increasing flow appeared to be responsible for this early peak. The length of time since the last storm determined, in part, the concentration of FPOC achieved during that discharge event.
A comparison between the cell division rate of natural populations of the marine diatom Skeletonema costatum (Greville) Cleve grown in dialysis culture and that predicted from a mathematical model1
Authors: Yoder James A. , Yoder James A.
Published: March 2010

At weekly intervals from January through May 1977, during the winter‐spring phytoplankton bloom in Narragansett Bay, Rhode Island, a phytoplankton sample was collected from the bay, encapsulated in dialysis bags, incubated in flowing seawater for 2–5 days at two different light levels, and the cell division rate of Skeletonema costatum was determined. Light intensity, water temperature, and the ambient concentrations of dissolved inorganic nitrogen, phosphorus, and silicon were measured during each experiment. Observed cell division rates were compared with those predicted from a mathematical model incorporating terms for the effect on growth of light intensity, temperature, and silicate concentration.

Regression analysis revealed that equations incorporating only the effect of temperature and light intensity were sufficient to explain the observed cell division rate in many experiments, hut the inclusion of silicate concentration improved the relationship. The cell division rate of these natural populations of S. costatum grown in dialysis bags in flowing seawater could thus be predicted with reasonable accuracy with a simple mathematical model primarily formulated from the results of a batch culture study of a single clone of this species.
Diel and vertical patterns of alkaline phosphatase activity in the oceanic dinoflagellate Pyrocystis noctiluca1
Authors: Rivkin Richard B. , Swift Elijah
Published: March 2010

Alkaline phosphatase activity (APA) was measured at stations in the Caribbean and Sargasso Seas on batches of 100–150 Pyrocystis noctiluca isolated from double‐closing net tows at various depths at 4–6‐h intervals. A diel pattern of activity was suggested, with the highest activity during the day and the lowest several hours before sunrise. The APA was highest in the mixed layer and lowest at the base of the euphotic zone. The dissolved N:P ratio declined 2–3‐fold when hydrolyzable organic phosphorus was included as part of the phosphorus pool, implying that organic phosphorus could contribute significantly to the phosphorus available to phytoplankton having alkaline phosphatase. In laboratory experiments the activity of the enzyme was depressed at an orthophosphate concentration as low as 0.05 µM, and 3.0 µM completely repressed alkaline phosphatase within 120 min. APA was proportional to the light intensity during preconditioning rather than during incubation. A diel pattern of activity was observed in laboratory cultures of P. noctiluca due to changes in light cycle alone. In the field, daily variations in light, mediated by associated changes in cell metabolism, appear to be the effectors of the observed diel rhythm of APA in P. noctiluca.
Relationship between productivity and N2 (C2H2) fixation in a Thalassia testudinum community1
Authors: Capone2 Douglas G. , Penhale3 Polly A. , Oremland4 Ronald S. , Taylor Barrie F.
Published: March 2010

N2 (C2H2) fixation and primary production were measured in communities of Thalassia testudinum at two sites in Bimini Harbor (Bahamas). Production was determined by uptake of [14C]NaHCO3, by leaf growth measurements, and by applying an empirical formula based on leaf dimensions. The last two methods gave similar results but the 14C method gave higher values. Anaerobic sediment N2 fixation supplied about ¼ to ½ of the nitrogen demand for leaf production (by leaf growth method) and there was a significant correlation between N2 fixation and CO2 fixation rates when all components of the communities were considered (macrophyte, phyllosphere epiphytes, and detrital leaves). N2 fixation is important to production in Thalassia communities and the plant and its leaf epiphytes may be distinct entities in terms of nitrogen and carbon metabolism.
Nitrogen fixation by rhizosphere and free‐living bacteria in salt marsh sediments1
Authors: Teal John M. , Valiela Ivan , Berlo Diane
Published: March 2010

The rates of nitrogen fixation by rhizosphere and free‐living bacteria are highest near the surface of a variety of salt marsh sediments and in the warm part of the year. The highest rates were found in vegetated habitats, reaching up to about 500 ng N·cm−2·h−1. Bacterial N2 fixation for the entire marsh is more than 10 times larger than algal fixation and less than a third of the N required to support growth of the vegetation.
Enrichment of Zn, Cd, Pb, and Cu in the surface microlayer of Lakes Michigan, Ontario, and Mendota1
Authors: Elzerman Alan W. , Armstrong David E.
Published: March 2010

Measurements of surface film pressure in areas of Lakes Michigan, Ontario, and Mendota with capillary wave damping ranged from <2 to >22 dyn·cm−1, but were typically 2–10. Screen‐collected surface microlayer samples generally contained higher concentrations of Zn, Cd, Cu, and especially Ph, than samples from 30‐cm depth at the same site. Areas with a film pressure >1 dyn·cm−1 showed greater surface enrichments of Zn, Cd, Pb, and Cu than areas with no apparent surface‐accumulated material. Variations in surface enrichment between individual samples suggest that local conditions are important in controlling surface enrichment, but some similarities between metals and sites were apparent. Foam samples collected on Lake Michigan also contained higher concentrations of Zn, Cd, Pb, and Cu than the bulk water.
On the variability of water properties in the surface mixed layer at Station P
Authors: Tabata S.
Published: March 2010

Temperature, salinity, and oxyty data collected from the surface mixed layer at Station P (50°N, 145°W) in the northeast Pacific Ocean from August 1956 through October 1976 have been examined for their variabilities within the layer. The layer is isothermal to within ±0.02°C during the cooling season (October through March) and to within ± 0.03°C during the heating season (April through September). It is isohaline to within ±0.003‰ and iso‐oxygenic to within ±0.04 to ±0.05 ml·liter−1 during both seasons. Determination of the actual variability of salinity within the layer is limited throughout the year by the accuracy of the instrumentation used; in the case of temperature, determination of the variability is limited in this way at least during the cooling season. The variability of oxyty is somewhat larger than would be indicated by the precision associated with the methods used; this is attributed to sampling errors.
A modification of the Hynes method for estimating secondary production with particular significance for multivoltine populations
Authors: Benke Arthur C.
Published: March 2010

The accepted procedure for de termining production of multivoltine invertebrates by use of the Hynes method is to multiply the Hynes value by the number of generations per year. For aquatic insects, if pupal, adult, or egg stages comprise a significant portion of total generation time, this procedure will underestimate production. For crustaceans, if reproduction occurs before attaining the final size class, the procedure, using generation time, will overestimate production. It is necessary to multiply the Hynes value by 365/CPI, where CPI is the cohort production interval (in days) from hatching to the attainment of the largest aquatic size class.
Methods of calculating cohort production from field data‐some relationships
Authors: Gillespie D. M. , Benke A. C.
Published: March 2010

Four commonly used methods of directly computing cohort production are increment‐summation, removal‐summation, instantaneous growth, and the Allen curve. These may be used in either instantaneous exponential form or discrete linear form. The instantaneous exponential forms of the four methods are shown to be exactly equivalent. In discrete linear forms, the increment‐summation and removal‐summation methods are exactly equivalent, while the instantaneous growth and Allen curve methods are approximations of the other two. Simplified computational equations are given for calculating production by the various methods.
A versatile method for the rapid and accurate determination of carbon by high temperature combustion1
Authors: Salonen Kalevi
Published: March 2010

A method is described for determining carbon by combustion at high temperature. Samples are transferred to the furnace without contamination thus allowing a sensitivity of 0.01 µg C. The precision is good (C.V. 0.5% at 1 µg of C level) and 1–3 samples can be analyzed in 1 min. No prior treatment of samples is necessary for determining total carbon. The method is suitable for routine analysis of carbon in single particles, homogenates, suspensions, and solutions.
A method for the determination of chlorophyll a in samples containing degradation products1
Authors: Whitney David E. , Darley W. Marshall
Published: March 2010

The traditional spectrophotometric acidification technique used to measure Chl a in the presence of pheopigments is improved by addition of a phase‐separation step which removes chlorophyllides and pheophorbides.
An improved apparatus for use with the 14C acid‐bubbling method of measuring primary production
Authors: Chris Wessels , Eliezer Birnbaum
Published: March 2010

An improved apparatus is described for acidifying and degassing 14C‐labeled samples for measurement of primary production. Large numbers of samples can be handled safely, quickly, and reproducibly.
Techniques for sampling the air‐sea interface for estuarine and coastal waters
Authors: Hamilton Eric I. , Clifton Robert J.
Published: March 2010

A freezing probe impacted onto the surface of the sea had a very high efficiency for the removal of most materials present, surface water, and any suspended particulate material present to a depth of about 1,000 µm. A PVC film cast on the sea surface removed solid materials and various organic compounds, such as lipids and hydrocarbons, floating on the surface but excluded aqueous phases.
A filling‐box model of river‐dominated lakes
Authors: Killworth Peter D. , Carmack Eddy C.
Published: March 2010

A dynamical model of river‐lake interaction is used to quantitatively examine the physical behavior of the Kamloops Lake‐Thompson River system in British Columbia. Analysis is based on the so‐called filling‐box method which predicts the thermal stratification of the lake relative to hydrological conditions; specifically the river's effect on thermocline formation and decay, convective overturn, heat exchange, and particle residence time are examined. The model can be used to simulate the effects of hypothetical developments in the watershed and to examine physical processes relevant to the release of pollutants upstream.
Acoustical estimation of zooplankton populations1
Authors: Greenlaw Charles F.
Published: March 2010

Acoustical estimates of zooplankton abundance can be made rigorously if the scattering behavior as a function of size and frequency for the zooplankters is known. Measurements of scattering at a single frequency can be used to estimate abundance if the mean zooplankter size is known. Measurements at two frequencies can be used to estimate the dominant size as well as abundance if a single size zooplankter dominates the acoustical scattering. Measurements at several frequencies can be used to estimate size distributions and abundances. In a field experiment, acoustical scattering was measured at three frequencies for zooplankton layers composed largely of euphausiids (for which an approximate scattering model is known). These data are analyzed by each method and estimates of numerical abundance given.
Zooplankton grazing and phytoplankton species richness: Field tests of the predation hypothesis1
Authors: McCauley Edward , Briand Frédéric
Published: March 2010

The hypothesis that herbivory plays a major role in the maintenance of high algal diversity was tested over a 2‐year period in polyethylene enclosures at Heney Lake, Quebec. Reduction of grazing pressure resulted in a significant decrease in the number of inedible species, whereas the diversity of edible algae remained unaffected. Lowering the herbivore levels may cause an intensification of exploitative competition among phytoplankton, which favors edible species and a few inedible algae like Synedra at the expense of many inedible species that are eliminated.
Predation, competition, and zooplankton community structure: An experimental study1,2
Authors: Lynch Michael
Published: March 2010

An experimental investigation of the zooplankton community of a small Minnesota pond was conducted for 2 years to determine the mechanisms maintaining its structure and to show that it is predictably organized. A mechanistic interpretation of the structure of this community cannot be made solely on the basis of predation, but also requires evaluation of the relative competitive abilities of the herbivores. The presence of Chaoborus and fish place predictable constraints on the abundance of zooplankton species in this pond. The competitive dominant (Ceriodaphnia reticulata) is of intermediate size and is removed when either predator is abundant. In the presence of intense Chaoborus predation, Ceriodaphnia is replaced by a larger subordinate competitor, Daphnia pulex; when fish predation is intense, smaller species (Bosmina longirostris and rotifers) increase. These small species are also able to maintain large populations in vertebrate‐free environments when Chaoborus is rare. When these small herbivores are abundant, two additional invertebrate predators (Cyclops vernalis and Asplanchna priodonta) arrive, neither of which seems able to reduce its prey to extinction.
Growth, feeding, and mortality of larval and early postlarval stages of the oceanic shrimp Sergestes similis Hansen
Authors: Omori M.
Published: March 2010

Sergestes similis Hansen released from 670 to 1,140 eggs under laboratory conditions and was, for the first time, successfully reared from the egg to the 8th postlarval stage. Hatching viability, growth, mortality, and feeding during various developmental stages were investigated at four temperatures. Four phytoplankton and three zooplankton species were used as food. The optimum temperature range for larval development was 10°–15°C. The protozoeal stages, particularly the first and third, were the most critical in the development of S. similis. Growth rates were higher in the protozoeal and zocal than in the naupliar and postlarval stages. Average coefficients of daily exponential growth ranged from 0.021 to 0.098 during the larval and early postlarval stages. Filtering, clearance, and ingestion rates increased with increasing body weight and with particle size. Filtering rates changed with concentration of algal cells, suggesting the existence of a threshold value at lower algal density. However, the clearance rates were affected not by the density but only by the size of prey. When animals began predation, at the 2nd protozoeal stage, the size range of food particles and the volume over which the animals searched for food increased abruptly. The maximum daily ration ranged from 24 to 110% of body weight; it was highest in the protozoeal stages and gradually decreased afterward. The gross growth efficiency was 10–50% (average 32%) in the larval and postlarval stages.
A population dynamics analysis of the cladoceran disappearance from Lake Tahoe, California‐Nevada1
Authors: Goldman Charles R. , Morgan Mark D. , Threlkeld Stephen T. , Angeli Nadine
Published: March 2010

A comparison of the population dynamics of Daphnia pulicaria and Daphnia rosea in 1967–1969 and during their decline from Lake Tahoe in 1970 showed that the decline resulted from a combination of increased death rates and decreased birth rates. The remaining cladoceran, Bosmina longirostris, disappeared from the plankton in 1971. The elimination of cladocerans coincided with high densities of the opossum shrimp, Mysis relicta, and the kokanee salmon, Oncorhynchus nerka. Predation by these two introduced species is believed to have increased cladoceran death rates. Changes in the timing of the peaks of primary productivity are a possible cause for the decline in birth rates.

A brief resurgence of Bosmina in late 1974 was associated with a dramatic decline of the mysid population and the continued decline of kokanee which began in 1970. The mysids recovered by late 1975 but Bosmina again disappeared and has remained absent since. The failure of Daphnia to reappear suggests that factors in addition to predation by kokanee and Mysis exclude them from Lake Tahoe. Changes in the phytoplankton community composition may have altered the ability of the cladocerans to maintain birth rates sufficiently high to offset increased losses due to predation.