bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships between bacteria and grain surfaces in intertidal sediments1
Authors: DeFlaun Mary F. , Mayer Lawrence M.
Published: April 2010

Seasonal changes in total bacterial numbers and their associated mucus coatings in surficial sediments were examined. Bacterial numbers followed the temperature cycle, with highest numbers in summer. The specific surface areas of the sediments were measured rather than inferred from other granulometric properties; bacterial numbers were proportional to surface areas only for sample suites collected at the same time. Bacteria inhabited shallow depressions on sand and silt grains; they were not found on grains smaller than about 10 µm or inside smaller pores like those on weathered feldspar grains. Mucus coatings also followed a seasonal cycle, increasing in abundance and coalescence from spring into summer. These coatings accumulated clay grains, suggesting that the relationship of bacteria to surface area may be due to bacterial control of surface area rather than the reverse. Organic carbon concentrations in grain size separates of these sediments increased with decreasing size until the fine silt fraction, and decreased in the clay fraction; it is not clear, however, whether this trend is a result or a cause of bacterial colonization patterns.
Variability in the benthic Mn flux in coastal marine ecosystems resulting from temperature and primary production1
Authors: Hunt Carlton D.
Published: April 2010

The flux of Mn2+ from estuarine sediments contained in large cylinders was studied over a 14‐month period by periodically capping the entire 2.5‐m2 sediment surface with a benthic chamber. The seasonal magnitude in the Mn2+ flux could be described by an exponential function of the temperature. However, the flux at a given temperature varied by a factor of 6–10. During summer (June–September), Mn flux was strongly correlated not to temperature but to the average primary productivity during the month preceding the flux determination. Significant correlations between Mn flux and primary productivity were also obtained for discrete 15‐day intervals up to 68 days before the flux measurement. Postflux correlations were not significant except for a 2‐week interval immediately following the measurement when annual data were considered. The results suggest that the input of new organic matter to the sediments exerts a major control over the production of Mn2+ in anoxic sediments and that temperature relationships alone do not predict the magnitude nor variability in benthic Mn flux.
Autotrophic processes in meromictic Big Soda Lake, Nevada
Authors: Cloern James E. , Cole Brian E. , Oremland Ronald S.
Published: April 2010

Daily rates of oxygenic photosynthesis (OP) by phytoplankton, anoxygenic photosynthesis (AP) by purple sulfur bacteria, and chemoautotrophic productivity (CP = dark CO2 assimilation) were measured once each season in saline, meromictic Big Soda Lake. Total daily productivity and the relative importance of each autotrophic process varied with seasonal changes in vertical mixing, light availability, and the biomass of phototrophs. Daily productivity was highest (2,830 mg C·m‒2) and was dominated by OP in winter when the mixolimnion was isothermal, the biomass of phytoplankton was high, and the biomass of purple sulfur bacteria was low. During the summer‐fall period of thermal stratification, phytoplankton biomass decreased, a plate of purple sulfur bacteria formed below the oxycline, and daily rates of dark CO2 assimilation (CP = 390–680 mg C·m‒2) exceeded phototrophic productivity (OP + AP = 200–370 mg C·m‒2). Total annual productivity was about 500 g C·m‒2, of which 60% was produced by phytoplankton (mostly in winter), 30% by chemoautotrophs (nitrifying and sulfur‐oxidizing bacteria), and only 10% by photosynthetic bacteria.
Microelectrode studies of the photosynthesis and O2, H2S, and pH profiles of a microbial mat1
Authors: Revsbech Niels Peter , Jorgensen Bo Barker , Blackburn T. Henry , Cohen Yehuda
Published: April 2010

The profiles of O2, H2S, and pH within a microbial mat of the hypersaline pond Solar Lake, Sinai, were measured by 2–200‐µm‐thick microelectrodes during diurnal and artificial light cycles. The oxygen concentration in the photic layer varied from a maximum of 1,400 µM during the day to 0 during the night. The pH in the same layer varied between 9.6 in the early afternoon and 7.7 in the early morning. Sulfide was not present in the photic zone during the day, but built up to about 50 µM during the night. The diffusion gradients of sulfide and oxygen were very steep and the two compounds coexisted in a layer only 0.25 mm thick during the day. Diffusion flux calculations showed that the average turnover time of sulfide within this layer was 21 s. The rapid turnover indicated that the oxidation of sulfide must be biologically mediated. Oxygenic photosynthesis was measured by a new oxygen microprofile method which accurately determines the vertical distribution of photosynthetic activity. There was no difference in the efficiency of photosynthesis between morning and afternoon. The photosynthetic efficiency of the whole mat was about fourfold higher at low light intensities, <120 µEinst· m‒2·s‒1, than at high light intensities, 120–1,600 µEinst·m‒2·s‒1. Anoxygenic photosynthesis within the mat was not quantitatively important.
Photosynthesis and structure of benthic microbial mats: Microelectrode and SEM studies of four cyanobacterial communities1
Authors: Jorgensen Bo Barker , Revsbech Niels Peter , Cohen Yehuda
Published: April 2010

The microzonation of photosynthetic organisms in four cyanobacterial mats of Solar Lake, Sinai, was studied by light and scanning electron microscopy. The zonation was compared to the distribution of photosynthesis and of O2, H2S, and pH. Microelectrodes were used to measure the chemical gradients as well as the photosynthetic rates by a newly developed technique which allows a spatial resolution of 100 µm. In one of the mats, the photic zone was only 0.8 mm thick and there was a maximum photosynthetic rate of 50 µmol O2·cm‒3·h‒1 at 0.3–0.4‐mm depth. Three other mats had photosynthesis down to 2.5, 4.5, and >10 mm. Photosynthetic rates in the shallow water mats ranged from 13.3 to 17.6 mmol O2·m‒2·h‒1. Two‐dimensional maps of oxygen and photosynthesis distribution at the mat surface demonstrated a strong heterogeneity with rapid oxygen production within dense diatom tufts of 0.2–0.5‐mm diameter overgrowing the cyanobacteria. The photosynthesis in the tufts reached 100 µmol O2·cm‒3·h‒1, which led to an oxygen turnover time of only 23 s. Gas bubbles within the mat served as dynamic reservoirs for oxygen during light‐dark cycles and buffered against extreme diurnal variations between oxygen and sulfide.
Microbial degradation of dissolved proteins in seawater1
Authors: Hollibaugh J. T. , Azam F.
Published: April 2010

An experimental protocol using radiolabeled proteins was developed to investigate the rates and mechanisms whereby dissolved proteins are degraded in natural marine plankton communities. The results of field observations and laboratory experiments indicate that proteins are degraded by a particle‐bound, thermolabile system, presumably bacteria‐associated enzymes, with an apparent half‐saturation constant of ca. 25 µg bovine serum albumin (BSA) per liter (ca. 1.7 × 10‒10 M). Gel permeation chromatography indicates that peptides of chain length intermediate between BSA and the final products of degradation (MW < 700) do not accumulate in the medium. Competition experiments indicate that the system is relatively nonspecific (affinity: proteins > large peptides ≫ small peptides). Turnover rates for the protein pool in samples collected in the Southern California Bight were of the same order of magnitude as the turnover rate of the l‐leucine pool and were correlated with primary productivity, chlorophyll a concentrations, bacterial abundance and biomass, and l‐leucine turnover rate. These data suggest that amino acids derived from proteins are utilized preferentially and do not completely mix with the amino acids in the bulk phase.
Methane consumption in Framvaren, an anoxic marine fjord1
Authors: Lidstrom Mary E.
Published: April 2010

The biological consumption of methane has been studied in Framvaren, a Norwegian fjord 177 m deep with a well defined and stable sulfide interface at 18 m. The methane profile from the water column suggested that methane might be consumed at two depths, an aerobic zone between 12 and 16 m, and an anaerobic zone between 150 and 177 m. Water samples were incubated in bottles and poisoned with either Formalin or acetylene at four different times. Methane disappearance was detectable only in the 16‐, 150‐, 160‐, 170‐, and 177‐m samples. This disappearance was inhibited by both Formalin and acetylene in the 16‐m sample, but only by Formalin in the 150‐and 177‐m samples. These results suggest that both aerobic and anaerobic consumption of methane occur in this environment.
A simple device for recording the maximum force exerted on intertidal organisms1
Authors: Denny Mark W.
Published: April 2010

A new dynamometer records the magnitude and direction of the maximum force imposed on individual organisms by rapid water flow. These measurements allow “exposure” to be accurately quantified, and maximum water velocity to be estimated. The device is rugged, simple to build, inexpensive, and can be used in a variety of habitats.
The prediction of internal phosphorus load in lakes with anoxic hypolimnia1
Authors: Nürnberg Gertrud K.
Published: April 2010

Lakes with anoxic hypolimnia (anoxic lakes) have significantly lower values for phosphorus retention than do lakes with aerobic hypolimnia (oxic lakes). This difference may reflect an increased internal phosphorus load from the anoxic hypolimnia.

Two models are given to predict internal phosphorus load (Lint) in such lakes. The first predicts internal load as the difference between the observed phosphorus retention in anoxic lakes and that predicted (Rpred) by a formula that adequately describes phosphorus retention in oxic lakes. The second predicts internal load as the product of an average rate of phosphorus release from anoxic sediments, the surface area of the anoxic sediment, and the period of anoxia. Predictions of the first model compare favorably with 17 observed values of internal load; further data are required to test the second model. These models suggest that mean phosphorus concentration (TP) in anoxic lakes can be predicted in two ways. One can use whole‐lake phosphorus budget models which implicitly incorporate internal phosphorus load, because they include a measurement of phosphorus retention. Alternatively, a term to account for the internal load can be added to current models based on external load (Lext) and predicted retention (Rpred) where qs is areal water load:

urn:x-wiley:00243590:media:lno19842910111:lno19842910111-math-0001
Carbon‐14 labeling of phytoplankton carbon and chlorophyll a carbon: Determination of specific growth rates1
Authors: Welschmeyer Nicholas A. , Lorenzen Carl J.
Published: April 2010

The pattern of photosynthetic 14C labeling over time is described for phytoplankton. The carbon‐specific growth rate (d‒1) is defined explicitly by changes in the specific activity (dpm·µg‒1 C) of the algae. For Skeletonema costatum, growing in axenic batch culture, the specific activities of both total cellular carbon and chlorophyll carbon increase at equal rates and the change in specific activity with time follows the predicted pattern. The specific activity of 14C‐labeled chlorophyll a was used to estimate phytoplankton growth rates and C:Chl ratios of field samples in Dabob Bay (Puget Sound), Washington. Growth rates decreased with depth and C:Chl ratios were higher for samples incubated under high light intensity. In several instances the C:Chl ratio increased from the beginning to the end of the incubation; this trend was most conspicuous near surface light intensities and for days of high total incident radiation. On these occasions, Chl a was actively 14C labeled, yet little (or even negative) change was noted in the concentration of Chl a. These results suggest that some process (or processes) of chlorophyll degradation must be active at the same time that chlorophyll is being synthesized.
Control of diel vertical migration: Photoresponses of a larval crustacean1
Authors: Forward Richard B. , Cronin Thomas W. , Stearns Donald E.
Published: April 2010

The lower threshold for phototaxis of dark‐adapted larvae of the crab Rhithropanopeus harrisii is 10‒7 W·m‒2 at 500‐nm light. This threshold does not change throughout development. In the Newport River estuary (North Carolina), larvae show a pattern of nocturnal vertical migration in which the distribution of later‐stage zoeal larvae centers on the 10‒7 W·m‒2 isolume during the day. The behavioral responses underlying this relationship include a negative geotaxis in darkness which changes to a sinking response in light with a natural underwater distribution. The minimum increase in intensity above the lower threshold which evokes sinking decreases progressively with age. The intensity is well above the phototactic response threshold for stage I zoeae, but within one log unit of threshold for the other three zoeal stages. Thus, during the day larvae are associated with a preferred light level. This association results from a negative geotaxis in darkness that changes to a sinking response upon an increase in light intensity.
The April distribution of murres and prey patches in the southeastern Bering Sea1
Authors: Woodby Douglas A.
Published: April 2010

Murres were abundant over the continental shelf and scarce over deep oceanic water in the southeastern Bering Sea during April 1978 and 1979. They occurred in scattered flocks and in patches averaging 26 birds·km‒2 within a 300‐ × 450‐km area. Thick‐billed murres (Uria lomvia), the most common species, concentrated between shelfbreak and a middle front at the 100‐m isobath, where a trophically rich pelagic system supports shallow patches of fish and zooplankton. There were fewer murres inshore of the middle front, and these were mostly common murres (Uria aalge). The densest patches of fish and zooplankton in the study area were as long as 50 and 35 km. The distribution of murres was not closely tied to that of fish in either year and corresponded to zooplankton distribution in the second year only. Murres may be feeding where prey concentrations are low or minimal, and frequent storms interfere with feeding.
Importance of ultraviolet radiation in photoinhibition of microalgal growth1
Authors: Jokiel P. L. , York R. H.
Published: April 2010

Algae vary greatly in their long termability to adapt to levels of natural solar ultraviolet radiation encountered near the surface of the sea. Photosynthetically active radiation (where PAR is defined as quantum flux between 400 and 700 nm) produced little or no growth inhibition even at full surface intensity. In some species the capacity to tolerate intense PAR did not carry into the range of UV‐A (315–400 nm) or of UV‐B radiation (280–315 nm) or both. Photoinhibition became increasingly severe above 20% of surface intensity among the species sensitive to UV radiation. PAR flux in excess of that required for maximum growth was not inhibitory, but rather the higher levels of associated UV radiation reduced growth rate. These results support a previous suggestion that other molecules besides chlorophyll sensitize or shield algae in the UV portion of the solar spectrum.
Apparent 15N uptake kinetics resulting from remineralization1,2
Authors: Garside C.
Published: April 2010

A computer model of phytoplankton 15N uptake experiments in which simultaneous remineralization is occurring is used to demonstrate potential artifacts if remineralization is disregarded. In simulated experiments where a range of 15N additions is made to obtain population kinetics, apparent kinetics can be obtained where none exist. Similarly, in simulated experiments where samples are taken over time there is an apparent decrease in uptake rates with time, which, when plotted against inferred changes in substrate concentration, gives rise to similar kinetics. In actual experiments, such artifacts could obscure any real kinetics and would lead to erroneous estimates of population characteristics.
The role of sedimentary organic matter in bacterial sulfate reduction: The G model tested1
Authors: Westrich Joseph T. , Berner Robert A.
Published: April 2010

Laboratory study of the bacterial decomposition of Long Island Sound plankton in oxygenated seawater over a period of 2 years shows that the organic material undergoes decomposition via first‐order kinetics and can be divided into two decomposable fractions, of considerably different reactivity, and a nonmetabolizable fraction. This planktonic material, after undergoing varying degrees of oxic degradation, was added in the laboratory to anoxic sediment taken from a depth of 1 m at the NWC site of Long Island Sound and the rate of bacterial sulfate reduction in the sediment measured by the 35S radiotracer technique. The stimulated rate of sulfate reduction was in direct proportion to the amount of planktonic carbon added. This provides direct confirmation of the first‐order decomposition, or G model, for marine sediments and proves that the in situ rate of sulfate reduction is organic‐matter limited. Slower sulfate reduction rates resulted when oxically degraded plankton rather than fresh plankton was added, and the results confirm the presence of the same two fractions of organic matter deduced from the oxic degradation studies.

Near‐surface Long Island Sound sediment, which already contains abundant readily decomposable organic matter, was also subjected to anoxic decomposition by bacterial sulfate reduction. The decrease in sulfate reduction rate with time parallels decreases in the amount of organic matter, and these results also indicate the presence of two fractions of organic carbon of distinctly different reactivity. From plots of the log of reduction rate vs. time two first‐order rate constants were obtained that agree well with those derived from the plankton addition experiment. Together, the two experiments confirm the use of a simple multi‐first‐order rate law for organic matter decomposition in marine sediments.
The characteristics of ammonium and nitrate uptake by phytoplankton in Lake Kinneret1
Authors: Berman T. , Sherr B. F. , Sherr E. , Wynne D. , McCarthy J. J.
Published: April 2010

Seasonal and diurnal patterns of NH4+ and NO3‒ uptake were determined for Lake Kinneret phytoplankton. Nanoplankton generally, but not always, had a higher uptake of NH4+ and NO3‒ than did net plankton. Ammonium was always taken up preferentially and the phytoplankton had lower apparent affinity (Ks) for this ion than for NO3‒. However, during the annual dinoflagellate bloom of Peridinium (February–May), when ambient levels of NH4+ were low and those of NO3‒ were high, a considerable portion of the total N flux was derived from NO3‒. The observed daily fluctuations of specific uptake rates for both NH4+ and NO3‒ can be partially explained by changes in light intensity. The finding that NO3‒ was utilized by the dinoflagellates implies that control of the amounts of this nutrient, which is predominantly supplied from watershed sources, could be important in limiting eutrophication in Lake Kinneret.
A comparison of the abilities of freshwater algae and bacteria to acquire and retain phosphorus1
Authors: Currie David J. , Kalff Jaap
Published: April 2010

Extant physiological and in situ data provide contradictory answers to the question of whether the bacterioplankton can outcompete the phytoplankton for phosphorus at natural concentrations. Two phytoplankton species and three bacterial species isolated from the epilimnion of Lake Memphremagog, Québec, were grown in phosphorus‐limited continuous cultures and their abilities to take up and retain phosphorus compared. The algae showed orthophosphate uptake kinetics comparable to those reported elsewhere. In contrast, the specific orthophosphate uptake rates (i.e. uptake per unit cell P) by the bacteria were variable, but much higher than the algal rates at the low P concentrations characteristic of natural waters. Algal and bacterial alkaline phosphatase activities were similar and provided no evidence that the algae could utilize organic P more efficiently than the bacteria. The bacteria showed some tendency to excrete P more readily than the algae but mixed culture experiments indicated that excretion did little to alter the long term partitioning of phosphorus between the algae and the bacteria. The kinetic data suggest that planktonic bacteria are unlikely to be limited by phosphorus in situ. Furthermore, our results are consistent with the hypothesis that the bacteria should be markedly superior competitors at natural phosphate concentrations.
Underwater radiant energy absorbed by phytoplankton, detritus, dissolved organic matter, and pure water
Authors: Kishino Motoaki , Booth Charles R. , Okami Noboru
Published: April 2010

The spectral irradiance distribution at five stations on lakes and at sea was measured with a portable underwater spectral irradiance meter. Chlorophyll a concentration and the absorption coefficient of the water were concurrently measured. From measured spectral irradiance distributions, radiant energy absorbed per unit volume was computed. At these stations, the effect of upward irradiance on total quanta absorbed by the water was negligibly small for all layers. The relative contributions of phytoplankton, detritus, dissolved organic matter, and pure water to the total absorbed quanta were also computed by taking into consideration the spectral dependency of each component: the contribution of quanta absorbed by phytoplankton was about 3–10% in clear water and about 30–40% in the plankton‐rich water.
The energetic cost of response to blue‐green algal filaments by cladocerans1
Authors: Porter Karen Glaus , McDonough Robert
Published: April 2010

Specific differences in behavior and energy expenditure in response to blue‐green algal filaments were examined as a possible cause of the shift from large‐ to small‐bodied cladocerans during eutrophication and seasonal succession. Mandible rate increased with body size among species and was maximal and independent of filament concentration within a species. Carapace gape increased with body size among species and was independent of filament concentration for Daphnia parvula, Ceriodaphnia lacustris, and Bosmina longirostris while it decreased with increasing concentration for Daphnia magna. An increase in Anabaena filament concentration caused a significant increase in rejection and respiration rates only for the largest species, D. parvula.
Biochemical composition and short term nutrient incorporation patterns in a unicellular marine cyanobacterium, Synechococcus (WH7803)1
Authors: Cuhel Russell L. , Waterbury John B.
Published: April 2010

Exponentially growing cells of a marine Synechococcus incorporate C, N, P, and S at a ratio of 95:16:3:1. Subcellular distributions of C, S, and P emphasized its low phospholipid and carbohydrate content. Short term carbon and sulfur incorporation accurately measured biosynthesis, but phosphorus was slow to reach isotopic equilibrium. Acetate and adenine were assimilated, but glucose and thymidine were not.
Quantitative grain density autoradiography and the intraspecific distribution of primary productivity in phytoplankton
Authors: Davenport James B. , Maguire Bassett
Published: April 2010

Analysis of a method of grain density autoradiography demonstrates that reliable measurements of the primary productivity of individual phytoplankton species can be obtained with this technique. Grain density autoradiography is particularly useful for providing an estimate of the intraspecific distribution of primary productivity. As an example, the productivity distribution of the marine diatom Chaetoceros curvisetus became positively skewed during a period of population decline.
Water temperature as an indicator of environmental variability on a coral reef
Authors: Potts D. C. , Swart P. K.
Published: April 2010

The magnitude and spatial extent of variation in water temperatures commonly experienced by corals were examined on several temporal scales to evaluate the association between environmental stability and habitat favorability. Shallow reef‐top sites were exposed to surface waters modified by prevailing weather conditions; the deeper outer slopes lay permanently within a well buffered, relatively oceanic water mass. Thermal stability and relative water movement were poor predictors of coral growth and survival. The most stable and the most unstable thermal environments were both poor habitats for corals.
The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere1
Authors: Benson Bruce B. , Krause Daniel
Published: April 2010

Previous work on the solubility of oxygen in freshwater has been extended to seawater. Measurements of the Henry coefficient in the ranges 0° < t < 45°C and 0< S < 50 fit the Setschenow relationship for the variation with salinity. The temperature dependence of the Setschenow coefficient for oxygen is found to be K = 0.0225034 ‒ 13.6083/T + 2,565.68/T2. The equation for the Henry coefficient as a function of temperature and salinity is used to calculate values for unit standard atmospheric concentrations (USAC) in freshwater and seawater in equilibrium with air at a total pressure of 1 atmosphere. It is estimated that the possible error in the new USAC values is no greater than ±0.1% and probably less. Tables and equations are presented for obtaining accurate USAC values in the ranges 0° < t < 40°C and 0 < S < 40. Simple procedures are given for calculating standard atmospheric concentrations at pressures different from 1 atm. The presence of sea salt has a negligible effect on the fractionation of the oxygen isotopes during solution.
The paradox of the plankton: Fluctuations of phosphorus availability maintain diversity of phytoplankton in flow‐through cultures1
Authors: Sommer Ulrich
Published: April 2010

Competition experiments with phytoplankton under steady state conditions have largely verified the competitive exclusion principle. Coexistence of species limited by different resources contributes little to the explanation of the natural diversity of phytoplankton. It is shown by multispecies experiments in flow‐through cultures that pulsed input of a key nutrient allows the coexistence of species competing for the same resource.
Carbon and nitrogen determinations of carbonate‐containing solids1
Authors: Hedges John I. , Stern Jeffrey H.
Published: April 2010

Two methods are described for determination of organic carbon, inorganic carbon, and total nitrogen in sediments, sediment trap materials, and plankton. Both methods discriminate organic and inorganic carbon by acidification, avoid losses of acid‐soluble organic and inorganic matter, and utilize an automated CHN analyzer for all elemental determinations. Short‐term precisions for organic carbon and total nitrogen are about ± 1% of the measured value with blank levels < 1.5 µg for each element.
Interstitial water sampling by dialysis: Methodological notes
Authors: Carignan R.
Published: April 2010

The dialysis technique for sampling interstitial waters is subject to several potential sources of error. Cellulose‐based membranes can lead to the underestimation or overestimation of porewater solutes. Polycarbonate was found unsuitable for dialyzer construction because of iron precipitation problems. The initial presence of dissolved O2 in the compartments can significantly affect sample composition. Equilibration times of 15–20 days were found adequate for most sediments. An efficient technique for pH measurement in small volumes of porewater is described.
A sediment porewater sampler used in root zone studies of the submerged macrophyte, Myriophyllum spicatum1
Authors: Bottomley E. Z. , Bayly I. L.
Published: April 2010

An in situ cylindrical porewater sampler, with interval stackers and a nondegradable membrane, is described. Both horizontal and vertical gradients of dissolved constituents in porewater can be assessed. Sampling at 4‐cm intervals within Myriophyllum spicatum root zones showed that steep depletion contours of dissolved phosphate occur, delimiting the zone of root influence.
Effects of lake acidification on rates of organic matter decomposition in sediments
Authors: Kelly C. A. , Rudd J. W. M. , Furutani A. , Schindler D. W.
Published: April 2010

Summer hypolimnetic and whole‐lake under‐ice measurements in an experimentally acidified lake suggested that rates of in situ decomposition in sediments (measured as methane and inorganic carbon release) were unaffected over an epilimnetic pH range of 6.7–5.1. This was apparently because microbial processes kept the pH at 6.0 or above just a few millimeters below the sediment surface even after lake water had been acidified for 8 years. In laboratory studies where the pH of mixed, fresh lake sediment was controlled at reduced levels, decomposition rates of carbon that had been in the sediments for several months were unaffected at pH values as low as 4.0. However, decomposition rates of newly sedimented material began to decrease at pH 5.25–5.0. Decomposition processes were less affected during the acidification of Lake 223 than were higher life forms.
Nickel, cadmium, and copper in the northeast Pacific off the coast of Washington1,2
Authors: Jones Carolyn J. , Murray James W.
Published: April 2010

The distributions of nickel, cadmium, and copper have been determined in northeast Pacific waters off the coast of Washington. Nickel concentrations average 5.5 nmol·kg‒1 at the surface and 10 nmol·kg‒1 in deep water. Although nickel shows a dual covariance with phosphate and dissolved silicon, a strong concentration gradient away from the coast cannot be explained by variations in the nutrient concentrations alone; an additional source in the sediments is suggested. The geochemistry of cadmium is controlled by the biological cycling of organic matter. Concentrations are depleted to levels of 0.1 nmol·kg‒1 at the surface but increase to a maximum of 1.27 nmol·kg‐1 at the depth of the phosphate and nitrate maxima. Cd‐phosphate and Cd‐nitrate correlations are significantly different in nearshore and offshore waters. Copper shows no correlation with the nutrients. An apparent surface maximum may result from the upwelling and offshore advection of Cu‐rich shelf water. Copper is rapidly stripped from subsurface waters but is then returned to bottom waters via a flux of dissolved copper from the sediments.
Night synthesis of protein by algae1
Authors: Cuhel Russell L. , Ortner Peter B. , Lean David R. S.
Published: April 2010

Dunaliella tertiolecta in culture showed rates of net protein synthesis at night nearly equal to those during the day. In night protein synthesis carbon stored in carbohydrates and metabolite pools was used, whereas sulfate was assimilated from the medium as needed. As a result, whole cell C:S ratios varied systematically over the diel cycle, while the C:S ratio of isolated protein remained constant. In the stationary phase, sulfate incorporation into protein, unlike carbon incorporation, measured net protein synthesis rather than turnover.

Diel experiments with natural populations of marine and freshwater algae demonstrated that night protein synthesis is a general phenomenon in phytoplankton. For samples previously exposed to saturating light, day and night rates of protein synthesis were similar. The use of carbohydrate and metabolic pool carbon for night protein synthesis not only increased protein to the food web, but also altered ratios of protein, carbohydrate, and lipid to one another. The latter might result in changes in the nutritional value of phytoplankton to herbivores.
Classification and dynamic simulation of the vertical density structure of lakes1
Authors: Patterson J. C. , Hamblin P. F. , Imberger J.
Published: April 2010

Field data from two lakes of widely differing geometry and size are analyzed in terms of four nondimensional numbers which allow the principal mixing processes in each lake to be identified. The numbers are based on basin geometry, density stratification, wind stress, and rates of inflow and outflow. The procedure highlights the differences in the dynamics of the two lakes and allows assessment of the validity of the assumption of one‐dimensionality. The result is that both lakes were dominated by one‐dimensional, but different processes. The dynamics of the epilimnion of the smaller lake were dominated by stirring from surface wind and cooling, whereas shear at the pycnocline was also significant in the larger lake. In neither case did the effects of the earth’s rotation, inflow, or outflow generate significant horizontal gradients. A one‐dimensional numerical model (DYRESM) was used to simulate the vertical temperature and salinity structures of both lakes over lengthy periods, with good results. The model is based on the parameterization of the important physical processes in a framework of horizontal layers of variable thickness and was applied in both lakes without alteration. The interpretative power of the model is demonstrated by examination of the formation and erosion of a thermal inversion in the larger lake.
Diel variation of nitrogen fixation in Lake Valencia, Venezuela1
Authors: Levine Suzanne N. , Lewis William M.
Published: April 2010

During 1981 we examined the diel variations of nitrogen fixation in Lake Valencia, Venezuela. Four species of heterocyst‐bearing blue‐green algae were common but subdominant in the phytoplankton. In samples taken from and incubated at 0.5 m, the rate of nitrogen fixation per unit volume of water was lowest at night (<6% of the maximum daytime rate), increased from dawn until early afternoon, and then diminished between late afternoon and the first hour of darkness. This pattern was caused partly by diel changes in light intensity and partly by diel migrations of heterocystous blue‐green algae. Heterocyst concentrations at 0.5 m increased between midmorning and early afternoon and then decreased from late afternoon until evening. The heterocyst‐specific nitrogen fixation rates (nitrogen fixed per heterocyst per unit time) at 0.5 m were much less variable than the nitrogen fixation rates per unit volume of water. Heterocyst‐specific rates rose rapidly in early morning and fell slowly in the evening, but were almost constant over much of the day. Heterocyst‐specific nitrogen fixation rates were very close to those predicted by a model based on the light dependency of nitrogen fixation. There was no evidence for temporal changes in the light response of nitrogen fixation.
Direct and inverse irradiance models in hydrologic optics1
Authors: Preisendorfer Rudolph W. , Mobley Curtis D.
Published: April 2010

It is shown how the direct irradiance model for stratified source‐free light fields in natural and laboratory hydrosols may be inverted so as to obtain from in situ irradiance measurements the volume absorption coefficient and mean backscatter coefficient consistent with the irradiance field. That is, the resultant optical properties may be arbitrary functions of depth in the hydrosol and the corresponding direct model will nevertheless exactly reproduce the original light field using the optical properties determined by the inverse model. In this way we obtain compatible light fields and optical properties within a hydrosol so that, given one, we can reproduce the other. The properties of the inversion algorithm are illustrated through its application to artificially generated light fields, and the effects of noise in the light field are studied. The algorithm is then used to obtain depth‐dependent absorption and backscatter coefficients from in situ irradiance measurements in the Sargasso Sea.
Reassessment of exudation by fucoid macroalgae1
Authors: Carlson David J. , Carlson Mary L.
Published: April 2010

Dissolved organic materials (DOM) exuded by Ascophyllum nodosum and Fucus sp. were collected in situ by minimally disruptive techniques. Exposed macroalgae released relatively large amounts of DOM during the first several minutes of submersion and then exuded at slower rates. There was considerable day‐to‐day and within‐day variation in short term exudation, occasionally among fronds of single plants. Exudation was not consistently related to desiccation of the algae. Average exudation was calculated to be ≈1 g C · m−2 substratum · d−1, only 2–5% of daily production by the macroalgae.
Particle flux and trace metal residence time in natural waters1,1
Authors: Santsch Peter H.
Published: April 2010

A simple inverse relationship between trace metal residence time and particle flux through the water column is tested on the trace metals Zn2+ in freshwater and Th(IV) in ocean water systems with available data on the vertical flux and concentration of particulate matter and of Zn2+ in lakes or on the disequilibrium of U/Th nuclides in the ocean. Natural or model aquatic ecosystems with different chemical compositions and particle fluxes confirm the concept that the particle flux through the water column is the major factor regulating trace metal concentrations in natural waters.
Seasonal changes of dissolved organic matter (C, N, P) in permanently well mixed temperate waters
Authors: Wafar Mohideen , Le Corre Pierre , Birrien Jean‐Louis
Published: April 2010

Seasonal changes of dissolved organic carbon (DOC), nitrogen (DON), phosphorus (DOP), chlorophyll a, and primary production were followed for 17 months in the permanently well mixed waters of the English Channel. There was a proportionality between the intensities of Chl a and the subsequent DOC peaks and the increase in DOC from a previous low value, showing that a major part of the DOC is produced through degradation of particulate organic matter. This DOC production was equivalent to 66 g C · m−2 · yr−1. Phytoplankton excretion may add about 16 g C · m−2 · yr−1 to the DOC pool. The DOM production following a phytoplankton bloom was characterized by a sequential appearance of DON, DOC, and DOP.
Cellulose digestion by freshwater microcrustacea1
Authors: Schoenberg Steven A. , Maccubbin Alexander E. , Hodson Robert E.
Published: April 2010

Representatives of three diverse families of Cladocera incorporated [14C(U)]cellulose with efficiencies of 2.3–11.5%, corrected for gut retention on the basis of chloroform‐ and methanol‐soluble label in tissue homogenates. This finding supports recent speculation that some detrital carbon may be used by consumers or affiliated symbionts without exogenous microbial transformation.
Organic matter degradation and biogenic element cycling in a nearshore sediment (Kiel Bight)1
Authors: Balzer Wolfgang
Published: April 2010

Benthic degradation of organic matter and the cycling of its C, N, P components was investigated at a coastal station (20 m) in Kiel Bight (western Baltic). Annual rates of carbon combustion and nutrient release from the sediment were derived from a comparison of input and burial of organic matter in the top sediment layers and from sediment oxygen consumption and nutrient release rates as determined by in situ enclosure experiments (2.9 mol O2·m−2 yr 1, 0.16 mol N·m−2·yr−1, 0.020 mol P·m−2·yr−1, and 0.58 mol Si·m−2·yr−1). A long term incubation was used to simulate chemical changes during the transition to anoxic conditions. The comparison of diffusive fluxes calculated from porewater profiles with total release rates indicates that the sediment surface is the major site of organic matter degradation, as a consequence of low sedimentation rate. From the organic matter reaching the bottom via sedimentation only 22% of the organic carbon (13% Norg and 15% Porg) is accumulated below 10 cm as sedimentary carbon and its reduced sulfur equivalent. While 75% of the carbon and 66% of the organic phosphorus input are returned to the water column, only half of the nitrogen input is released from the bottom; the rest is probably lost due to denitrification. Benthic flux contributes <20% to the annual P and N requirements for the pelagic primary producers.
The inwash of catchment diatoms as a source of error in the sediment‐based reconstruction of pH in an acid lake1
Authors: Battarbee R. W. , Flower R. J.
Published: April 2010

Diatom analysis of the recent sediments of an acid lake in Galloway, southwest Scotland, suggests that there was an increase in lake water pH following the ploughing of catchment soils in 1961 before conifer plantation. It is argued that the increase is an artifact resulting from the erosion and transfer of soils containing mainly nonacidobiontic diatoms to the sediments and the consequent depression of autochthonous acidobiontic taxa in the percentage diatom counts. This interpretation is supported by the data for diatom accumulation rates which indicate no decrease in the accumulation rates of the acidobiontic taxa over this period.
Can iron defecation from fish influence phytoplankton production and biomass in eutrophic lakes?1
Authors: Brabrand Age , Faafeng Bjørn , Källqvist Torsten , Nilssen Jens Petter
Published: April 2010

The supply of iron by fish feces to the phototrophic zone can provide a link in the biogeochemical cycle between the sediments and phytoplankton in eutrophic lakes. Fish feces stimulate growth in iron‐limited algal cultures. However, a factor related to the presence of the fish, probably epidermal mucus, inhibits algal growth rate by chelation of iron.
Species‐specific rates of growth and grazing loss among freshwater algae1
Authors: Lehman John T. , Sandgren Craig D.
Published: April 2010

Recent investigations into the population dynamics of phytoplankton communities have emphasized the variabilities of loss rates rather than growth rates in governing the changes that occur. Many freshwater phytoplankton, however, grow at rates that are measurably less than their maximum physiological capability because of nutrient limitation. At any moment the nutrient most limiting in situ division rates varies from species to species within an assemblage and the extents of limitation change with time. Rates of mortality inflicted by herbivorous zooplankton are likewise species‐specific, but the size of algal particles is a good predictor of whether the particle will be grazed at all. We manipulated grazer abundances and nutrient concentrations in enclosures to examine the effects on algal net growth rates. Grazed species were usually unicellular organisms. Some colonial species showed increased growth rates in the presence of grazers; in all cases these species were limited by N or P in situ. The variability of algal growth rates was much greater than that of measured loss rates due to grazing. Alternate loss rates, primarily sinking, seem to exhibit variability similar to growth rates in comparisons among all species in the assemblage.
Biosynthesis of dimethylsulfide and dimethylpropiothetin by Hymenomonas carterae in relation to sulfur source and salinity variations
Authors: Vairavamurthy A. , Andreae M. O. , Iverson R. L.
Published: April 2010

The marine coccolithophorid phytoplankton species Hymenomonas carterae (class Prymnesiophyceae) produces both dimethylpropiothetin (DMPT) and dimethylsulfide (DMS) in axenic cultures. The rate of DMS production is closely regulated by the cell; it remains independent of environmental sulfate concentration down to levels of 2.5% of the seawater value. Below this sulfate level, DMS production decreases with decreasing sulfate concentration, but significant amounts of DMS are released even under conditions of sulfate‐limited growth. Hymenomonas carterae can grow on sulfite, thiosulfate, and cysteine as sulfur sources, but not on methionine. The rate of DMS output is similar for the different sulfur sources.

Both the intracellular concentration of DMPT and the rate of output of DMS by H. carterae increase with increasing salinity of the medium. This increase is observed when either salt or sucrose is used to control the osmolarity of the growth medium. Variations in DMPT levels and DMS output were observed within hours after transferring cells to a medium of different osmotic pressure. The intracellular DMPT concentration is of the order of 0.3 mole per liter and contributes significantly to the osmotic pressure in the cell. These results suggest that DMPT plays an important role in osmoregulation by H. carterae.
Manganese fluxes in the benthic boundary layer1
Authors: Sundby Bjørn , Silverberg Norman
Published: April 2010

Diagenetic modeling and mass‐balance calculations were applied to box‐core and sediment‐trap data from three stations at 300–400‐m depth in the Laurentian Trough to estimate downward and upward fluxes of manganese across the sediment‐water interface, fluxes across the redox boundary in the sediment, rates of dissolution and precipitation of manganese, and rates of manganese accumulation. At all stations the cycling of manganese between the oxidizing and the reducing zone of the sediment was quantitatively more important than the cycling between the sediment and the water column. The redox boundary was the site of the largest fluxes. Downward fluxes across this boundary (0.45, 1.23, and 13.9 mmol m−2 d−1) were 3–50 times the rates of sedimentation or accumulation of manganese. The production of dissolved manganese turns over the inventory of particulate manganese in the sediment surface layer in 43–207 days. A small proportion of the dissolved manganese produced (13–29%) escapes the sediment, reprecipitates in the water column and, in part, returns to the sediment. Increased rates of bioturbation increase the rate of internal manganese cycling more than they do the rate of cycling across the sediment surface.
Use of radio‐controlled miniature aircraft for drifter and dye current studies in a tidal inlet1,2
Authors: Hess F. R. , Aubrey D. G.
Published: April 2010

A commercially available radio‐controlled miniature aircraft (wingspan 2.4 m) was modified and deployed as part of a field study of the ebbtidal flow characteristics of a natural, unstructured tidal inlet. To complement Eulerian current measurements within the main inlet channel, surface drifter and rhodamine dye patches were observed from the miniature aircraft and recorded with a 35‐mm camera. Position reference was provided with an array of precisely located markers on land and in the water. The miniature aircraft is an inexpensive, accurate alternative for Lagrangian studies in tidal inlets and estuaries, with many advantages over alternate techniques (such as hot‐air balloons, fixed platforms, manned aircraft, or chaser boat).
Rapid determination of chlorophylls and their degradation products by high‐performance liquid chromatography1
Authors: Bidigare R. R. , Kennicutt M. C. , Brooks J. M.
Published: April 2010

A shipboard HPLC system is described which can provide quantitative determinations of chlorophylls a, b, c and their degradation products. The technique is rapid (<20 min), precise, and can detect chlorophyll a concentrations as low as 13 pg per injection. Representative field data from the Southern Ocean are presented and briefly discussed.