bluuebunny/crossref_metadata_2025_split huggingface dataset:
Denitrification and nitrous oxide production in a coastal marine ecosystem1
Authors: Seitzinger Sybil P. , Nixon Scott W. , Pilson Michael E. Q. 
Published: April 2010

Denitrification was measured directly as the flux of N2 from sediment cores collected at various times of year at three stations in the Narragansett Bay, R.I., area. Rates of N2 production ranged from about 10 to 115 µmol N·m‒2·h‒1, with lowest values at 2°C in winter and highest at 15°C in summer. Denitrification represents a major sink for fixed N in the bay; annually the N2 production is equal to about 50% of the fixed inorganic N loading to the bay from rivers, land, and sewage. About 35% of the organic nitrogen mineralized in the sediments is removed from the ecosystem by denitrification.The percentage of organic nitrogen being mineralized in the sediments as N2O relative to N2 or NO3‒ + NO2‒ is higher in polluted sediments than in relatively unpolluted sediments, but in all cases is < 10%.
Chesapeake Bay nutrient and plankton dynamics. 2. Sources and sinks of nitrite1
Authors: McCarthy James J. , Kaplan Warren , Nevins John L. 
Published: April 2010

The transformations of inorganic nitrogenous nutrients that can lead to the frequently observed high levels of nitrite in the Chesapeake Bay and York River were investigated by a combination of 15N tracer techniques and assays of the concentrations of chemical constituents (NH4+, NO2‒, NO3‒, O2, N2O, and CH4).During destratification, uptake and remineralization of NH4+ in the York River followed a diel cycle, but nitrification was not as closely coupled to the light regime. The distributions of N2O, NO2‒, and CH4 in the York River suggest that the primary source of N2O and NO2‒, both produced during nitrification, was in the water rather than in the sediments. Rates of nitrification inferred from N2O gas flux calculations are consistent with measured in situ rates.Experiments at a series of stations in the mid‐Chesapeake Bay were designed to look at transformations among N pools. The yield of N2O‐N relative to NO2‒ ‐N during nitrification ranged from 0.2 to 0.7%, in agreement with previously published laboratory results.Our 15N data indicate that oxidized N can be formed in the water of the bay when physical events cause the mixing of NH4+‐rich bottom water with more oxygenated surface layers. We also found that N3‒ was reduced to NH4+ at unexpectedly rapid rates in well oxygenated surface waters.The magnitude and duration of high concentrations of N2O and NO2‒ in these estuarine waters during mixing events might be expected to increase if anthropogenic loading of nutrients causes anoxic conditions in the bay to become more widespread.
The asphyxiation technique: An approach to distinguishing between molecular diffusion and biologically mediated transport at the sediment—water interface
Authors: van der Loeff Michiel M. Rutgers , Anderson Leif G. , Hall Per O. J. , Iverfeldt Åke , Josefson Alf B. , Sundby BjÅrn , Westerlund Stig F. G. 
Published: April 2010

On the assumption that lack of oxygen will cause the activity of benthic infauna to cease and thereby limit solute transport to that accomplished by molecular diffusion, we have measured the flux of dissolved silicate across the sediment‐water interface of sediments incubated in situ under parallel benthic flux chambers. In one chamber the oxygen concentration was allowed to go to zero, and in the other the oxygen and pH remained at ambient values.As long as oxygen was present in the chambers, the measured summer and fall fluxes were 2– 10 times those calculated from porewater profiles assuming one‐dimensional molecular diffusion. The differences in fluxes predicted from the densities of macrobenthos at two different sites agree well with the flux measurements. After oxygen depletion, the silicate fluxes decreased and approached the values calculated on the basis of molecular diffusion. In one experiment the ratio between the oxic and anoxic fluxes was nearly identical to the ratio between the effective diffusion coefficient, as measured under oxic conditions using 22Na as a tracer, and the whole‐sediment molecular diffusion coefficient. In winter (‒1°C) measured and calculated Fickian fluxes agreed closely, indicating a negligible effect of benthos on solute transport.
Small‐scale nutrient patchiness: Some consequences and a new encounter mechanism1
Authors: Scavia Donald , Fahnenstiel Gary L. , Davis Judith A. , Kreis Russell G. 
Published: April 2010

Semicontinuous cultures of Lake Michigan algal assemblages were run at 0.15·day‒1 dilution rates under P limitation for 41 days. In control cultures, nutrients were supplied to the entire culture once per day. In patch cultures, 10% of the cultures received a high concentration 10‐min pulse each day. Patch and control cultures received equal nutrient flux and achieved equal biomass levels; however, their species composition was different. Patch cultures were dominated by the filamentous blue‐green alga Schizothrix calcicola and control cultures were dominated equally by S. calcicola, Nitzschia acicularis, and a group of phytoflagellates. These results, as well as shifts in subdominants, demonstrate the effect of small‐scale, short term nutrient patches on species composition. Similar patch and control unialgal cultures revealed lower cell nutrient quotas for patchy cultures.Microvideographic observations of Daphnia magna suspended in three concentrations of Chlamydomonas sp. allowed quantification of rates at which algal cells were collected, swept close by, and released via bolus rejection or outwashing of unpacked cells. Outwashing release rates of presumably unharmed cells increased from 31 to 71% of the collection rate as food concentration increased. It appears that algal outwashing is a significant mechanism for eliminating excess food. An important implication is the potential algal nutritional consequence of this very close nondestructive encounter.
Above‐ and belowground emergent macrophyte production and turnover in a coastal marsh ecosystem, Georgia1
Authors: Schubauer J. P. , Hopkinson C. S. 
Published: April 2010

Seasonal patterns of aboveground plant mass and the depth distribution of live roots, rhizomes, and dead belowground organic matter were measured for Spartina alterniflora and Spartina cynosuroides in Georgia tidal marshes. Peak live aboveground biomass was 1.6 × higher for S. cynosuroides than for S. alterniflora. Live biomass was 2.4 × more belowground than aboveground for S. cynosuroides and 1.7 × for S. alterniflora. Rhizomes made up 76 and 87% of live belowground biomass during the year. Mirrored patterns of biomass accumulation and loss in above‐ and belowground tissues during the year suggest the importance of seasonal storage and redistribution of organic matter.Belowground production was measured with a technique that partially accounts for midseason decomposition. Total plant production was estimated to be 7,620 g dry mass·m−2·yr−’ for S. alterniflora and 7,708 for S. cynosuroides. Belowground production was roughly 1.6 × aboveground production. Turnover rates for belowground live material were 1.42 · yr−1 for S. cynosuroides and 3.22·yr−1 for S. alterniflora. The fate of root and rhizome material, including the extent to which such material enters the estuarine or nearshore food webs, is not clear.
Organic matter diagenesis in freshwater sediments: The alkalinity and total CO2 balance and methane production in the sediments of Lake Washington1,2
Authors: Kuivila Kathryn M. , Murray James W. 
Published: April 2010

The interstitial water chemistry of Lake Washington sediments collected with an in situ sampler was studied. The depth where the sulfate concentration reaches a low background value appears to delineate a transition within the sediments above and below which profiles of total CO2, alkalinity, methane, and ammonium are linear, suggesting zones dominated by diffusion separated by a narrow zone of reaction.A stoichiometric model is used to identify the increase of alkalinity with depth in the interstitial waters. Ammonium production, followed by iron reduction, makes the largest contribution to this increase; about 30–40% is due to ammonia that has been produced but subsequently adsorbed by the sediments. The measured and calculated ammonia exchange constants agree well.The C:N ratio of the decomposing organic matter increases systematically, from 3.9 at 5 cm to over 14 at 50 cm. The organic matter being decomposed becomes nitrogen‐poor with age.Flux calculations for the lake‐sediment system show good agreement between the flux of carbon to the sediments and the sum of the diffusive loss from the sediments of CH4 and total CO2 and the permanent burial in the sediments. About a fourth of the detrital rain of carbon is recycled to the lake as a diffusive flux of CO2 and CH4.
The atmospheric correction and measurement of chlorophyll concentration using the coastal zone color scanner1
Authors: Guan Fumin , Peláez José , Stewart Robert H. 
Published: April 2010

The Coastal Zone Color Scanner on the Nimbus‐7 satellite produces images of the sea in five colors (bands) of light, and these can be used to measure chlorophyll concentrations in the water, to visualize chlorophyll patterns, and to observe how these patterns change through time. However, 80–90% of the light observed by the instrument comes from the atmosphere, and removing this air light is difficult and usually requires considerable processing of the data. We describe here a new method to remove the influence of air light that is accurate, independent of external information, and requires far fewer computations than previous methods. This procedure should facilitate the use of CZCS data in biological oceanography, especially by investigators who may not have access to large computers and elaborate atmospheric correction procedures.The technique has been tested by comparing ship and satellite estimates of chlorophyll; the comparison shows very good agreement. In addition, a comparison of sequential chlorophyll images shows that the technique produces stable chlorophyll estimates under changing atmospheric conditions.
Nutrient internal cycling and the trophic regulation of Green Lake, Wisconsin1
Authors: Stauffer Robert E. 
Published: April 2010

Algal nutrients (Si, N, P) and dissolved oxygen were studied in Green Lake, Wisconsin, in 1971– 1972, and in 1978–1980 following a reduction of about 35% in total external P loading in December 1976.Despite oxic conditions, there is more P in the hypolimnion than would be expected from the dissolved oxygen and from classical Redfield stoichiometry. Because of a metalimnetic dissolved oxygen minimum in late summer, the calculation and interpretation of the hypolimnetic oxygen deficit is affected by turbulent transport of dissolved oxygen.Vertical fluxes of P into the mixed layer are important in late spring and early summer, but, owing to metalimnetic P depletion, negligible between mid‐July and mid‐October. Vertical transport of Si into the mixed layer is negligible in summer and early fall compared with inputs from the land drainage basin.Although P is high at spring turnover, epilimnetic concentrations of P are low and Secchi transparency is high by mid‐to‐late summer. These seasonal changes are caused by sedimentation of P and low seasonal inputs from the drainage basin. This P is recovered in the hypolimnion and recirculated throughout the lake at fall overturn. It causes silica limitation of the diatom bloom each succeeding spring.The total P content of Green Lake and its seasonal partition among the layers were remarkably stable between 1971 and spring 1980, despite the reduction in external loading in 1976. The hypolimnetic oxygen deficit also showed no significant change between the first and eighth decades of this century.
Nitrogenous nutrient uptake, primary production, and species composition of phytoplankton in the Carmans River estuary, Long Island, New York1
Authors: Carpenter Edward J. , Dunham Susan 
Published: April 2010

Uptake of NH4+, NO3−, and urea was measured at four stations in a small temperate‐zone estuary over a 10‐month period. Considering all four stations, NO3− accounted for 45% of all N taken up, followed by NH4+ (43%) and urea (12%). Nitrogen uptake was highly temperature‐dependent (r = 0.82), and an exponential relationship was apparent. Recycling was very important as a source of nitrogen, and mean NH4+ pool turnover times were rapid, ranging from 4.3 to 6.8 h in the lower estuary in summer. PN turnover times in the lower estuary were also rapid, averaging 28.8 h in summer and being as short as 3.1 h in July and August.An analysis of N uptake using the relative preference index (RPI) indicated that NH4+ was the preferred nutrient. However, high NO3− concentrations appeared to override the repressive effect of NH4+ concentrations on nitrate reductase, and NO3− uptake was significant even at relatively high NH4+ concentrations. Urea uptake did not appear to be affected by NH4+ concentration.
Phototrophic sulfur bacteria in two Spanish lakes: Vertical distribution and limiting factors1
Authors: Guerrero R. , Montesinos E. , Pedrós‐Alió C. , Esteve I. , Mas J. , van Gemerden H. , Hofman P. A. G. , Bakker J. F. 
Published: April 2010

The anaerobic zones of Lakes Cisó and Vilar (Banyoles karstic area, NE Spain) had mass developments of purple sulfur bacteria during summer 1982. In Lake Vilar, Chromatium spp. was dominant (up to 92% of the microbial biovolume). In Lake Cisó, the predominant microorganisms were Chromatium spp. (up to 71%) and another purple sulfur bacterium forming aggregates (20%).The bacterial layer could be divided according to the physiological state of the cells into a top part of maximal specific activity, a peak of maximal abundance, and a bottom part of inactive cells. The bacteria in the peak were predominantly limited by light; sulfide, phosphate, and acetate were not limiting in the middle of the day. The light limitation started at the depth having the maximal concentration of cells; the top of the layer appeared to be sulfide‐limited. Specific contents of photopigments, elemental sulfur, and reserve polymers decreased from the top to the bottom of the bacterial layer. These phenomena point to the crucial role of light in the development of layers of phototrophic bacteria in stratified lakes.
The role of eopepod fecal pellets in the deposition of diatoms in Lake Tanganyika1
Authors: Haberyan Kurt A. 
Published: April 2010

Fecal pellets from a 16,000‐year sediment core from southern Lake Tanganyika account for over 40% of all diatom deposition and about 30% of total bulk sedimentation. Comparison of diatoms inside pellets with those in the surrounding sediment indicates that small, blunt species like Fragilaria brevistriata and Gomphonema clevei are preferentially ingested by grazing copepods. Long, fragile species like Nitzschia spiculum are strongly avoided. Filamentous Melosira spp. seem to be an important food of copepods.This grazing selectivity, coupled with the enhanced sinking rates and preservation of fecal pellets, could distort the fossil diatom record. Relative diatom abundances in pelletized, nonpelletized, and pooled stratigraphies indicate that pellets actually cause shifts of <4% of total diatom abundance in Lake Tanganyika. Even with selective grazing, F. brevistriata and G. clevei are rare in sediments (<2% of all diatoms).
Micromethod for lipids in aquatic invertebrates1
Authors: Gardner Wayne S. , Frez William A. , Cichocki Elizabeth A. , Parrish Christopher C. 
Published: April 2010

Microtechniques with disposable,calibrated, capillary pipets were developed to measure amounts and classes of lipids in individual Lake Michigan benthic invertebrates. After lipids from an animal were partitioned into 100 µl of extraction solvent and purified, measured portions were weighed with an electrobalance. Lipids in some samples were also characterized by thin layer chromatography with flame ionization detection (TLC‐FID). The extraction method was calibrated gravimetrically with cod liver oil and evaluated with a dry, ground fish sample. Lipid content was proportional (r = 0.99) to fish tissue dry weight over the range of 0.3–13 mg. TLC‐FID measurements correlated well (r = 0.98) with gravimetric analysis for portions of extracts of individual amphipods (Pontoporeia hoyi) and oligochaetes (Stylodrilus heringianus). TLC‐FID analysis indicated that <5% of the measured gravimetric weights was due to the inclusion of nonlipid material in the extracts.
Dissolved hydrocarbon metabolism: The concentration‐dependent kinetics of toluene oxidation in some North American estuaries1
Authors: Button D. K. , Robertson B. R. 
Published: April 2010

The metabolism of toluene by natural populations of marine bacteria, stored to enhance their activity, gave hyperbolic kinetics with saturation at only Kt = 0.6 to 3.4 µg liter−1. Similarly Kt in fresh seawater was 0.26 µg toluene liter−1. Freshly collected populations could be moderately active toward toluene, affinity a2A = 1.1−37.5 liters g‐cells−1 h−1. These moderate affinities taken together with the small Kt values give an explanation for the failure of most marine bacteria to grow at the expense of a single hydrocarbon.In two experiments there was a significant first‐order region in toluene in the 10–50 µg liter−1 range. When cultures of Pseudomonas sp. strain T2 were cast in suspended agar blocks to impede diffusion, toluene oxidation still followed hyperbolic kinetics although CO2 production and organic product formation were characterized by larger Michaelis constants.A large widespread population of bacteria with inducible capacity to metabolize hydrocarbons is indicated. Observed turnover times for toluene were 0.2–40 years with growth rates of 10−6 h−1 from toluene at 1 µg liter−1.
Mechanisms of hydrogen ion neutralization in an experimentally acidified lake
Authors: Cook R. B. , Kelly C.A. , Schindler D.W. , Turner M. A. 
Published: April 2010

The experimental acidification of Lake 223 (Experimental Lakes Area, northwestern Ontario) with sulfuric acid in 1976–1983 allowed a detailed examination of the capacity of the lake to neutralize hydrogen ion. A whole‐lake alkalinity and ion budget for Lake 223 showed that 66– 81% of the added sulfuric acid was neutralized by alkalinity production in the lake. Nearly 85% of in situ alkalinity production was accounted for by net loss of sulfate through bacterial sulfate reduction, coupled with iron reduction and iron sulfide formation, in littoral sediments (60%) and in the hypolimnion (25%). Exchange of hydrogen ion for calcium and manganese in the sediments accounted for 19% of the alkalinity generated, while other cations were net sinks for alkalinity. Alkalinity input from the watershed of Lake 223 was very small, averaging about 5% of that produced in the lake.The seasonal production of 1,000 µeq liter−1 alkalinity in the anoxic hypolimnion of this softwater lake could be attributed to bacterial sulfate reduction coupled with iron sulfide formation, ammonium production, and iron (II) production. Only the alkalinity produced from bacterial sulfate reduction coupled with iron sulfide formation remained throughout the annual cycle.
The carbon cycle for Lake Washington—A stable isotope study1
Authors: Quay P. D. , Emerson S. R. , Quay B. M. , Devol A. H. 
Published: April 2010

We investigate the carbon cycle in Lake Washington for the year 1980 using monthly measurements of the dissolved inorganic carbon (DIC) and its 13C : 12C isotopic composition. Mass balances of DIC and 13C : 12C yield estimates of CO2 gas exchange rates and net organic carbon production rates. Between 24 June and 13 August, the calculated CO2 gas invasion rate of 0.80 × 106 mol C d−1 is nearly equal to the river DIC inflow rate. The calculated epilimnetic net organic carbon production rate is 0.68 × 106 mol C d−1, about 20–30% of primary productivity estimated from 14C‐fixation experiments and ETS‐derived respiration rates. Metalimnetic and hypolimnetic DIC increase rates and porewater DIC gradients in hypolimnetic sediments indicate that remineralization of particulate organic carbon (POC) previously deposited in the sediments is a major (0.5 × 106 mol C d−1) DIC source to the lake during summer.For the whole year, summertime CO2 gas invasion balances wintertime CO2 gas evasion and DIC and POC outflow balance DIC and POC inflow rates, implying no net carbon burial in the sediments during 1980. This contrasts with the measured long term sedimentation‐rate‐derived carbon burial rate of 0.8 × 106 mol C d−1. Year‐to‐year variability in summertime primary production rates largely determines net gains or losses of carbon via CO2 gas exchange and sedimentation.
The pH of estuarine waters
Authors: Millero Frank J. 
Published: April 2010

The emf measurements for the TRIS buffer in seawater have been used to define buffer solutions that can be used to determine the pH on a free or total proton scale for estuarine waters. The pH is related to the stoichiometric dissociation constant (K*) of TRISH, the concentration of buffer (mTRIS) and salinity (S) by
urn:x-wiley:00243590:media:lno19863140839:lno19863140839-math-0001
where a = −9.73 × 10−5 and b = 6.988 × 10−5. The values of pK* were fit to equations of the form
urn:x-wiley:00243590:media:lno19863140839:lno19863140839-math-0002
where A, B, and C are functions of salinity and T is the absolute temperature.An electrode system with liquid junction was used to measure these buffers to compare the various pH scales.
Phytoplankton pigment patterns in the California Current as determined by satellite1
Authors: Peláez José , McGowan John A. 
Published: April 2010

The satellite images of phytoplankton pigments off California show a high degree of heterogeneity. However, recurrent phytoplankton pigment structures can be identified in the California Current. The major ones are: two sharp boundaries several hundreds of kilometers long; low pigment eddies far offshore interwoven with higher pigment structures immediately inshore; a low pigment intrusion in the Southern California Bight, and a higher pigment region farther offshore; eddies “attached” to shallow coastal areas; and California Current rings spawned far offshore.The larger scale structures of phytoplankton pigments show a remarkable continuity throughout a year, but there is shifting, wobbling, and erosion of these structures. The structures are strong and distinct in spring and summer, weaken through fall (except for a slight intensification in October), and become weakest and poorly defined in late fall‐early winter. The patterns of distribution of phytoplankton pigments for a given season tend to reappear from one year to another in the 3 years analyzed. Such recurrency is significant because these patterns may change, and some disappear, within any given year.Clear similarities of the phytoplankton pigment distributions to the field of dynamic height and to an infrared image of sea surface temperature indicate the very important role of ocean circulation, and of phytoplankton nutrient content of the waters, in the generation and maintenance of the observed patterns.