bluuebunny/crossref_metadata_2025 huggingface dataset:
Availability of nitrogen from municipal biosolids for dryland forage grass
Authors: Zebarth B. J. , McDougall R. , Neilsen G. , Neilsen D.
Published: April 2011

A 3-yr study, initiated in 1996, evaluated the availability of N from applied biosolids for dryland forage grass production under the cool, continental climatic conditions in central British Columbia. Treatments included 600 (LB), 1200 (MB) and 1800 (HB) kg total N ha−1 applied as municipal biosolids, a single application of 150 kg N ha−1 as urea in the first year of the experiment (SF), a multiple application of 150, 60 and 30 kg N ha−1 as urea in the first, second, and third years of the experiment (MF), and a control that received no biosolids or urea. All treatments were roto-tilled to 15-cm depth and seeded to a mixture of four grasses. The LB treatment was predicted to supply a similar quantity of plant-available N as the MF treatment, assuming 25, 10, and 5% of biosolids N is available in the first, second, and third year, respectively. Soil N fertility was poor as indicated by the very low forage yield and N uptake in the control, and minimal apparent net soil N mineralisation. Recovery of urea N in the crop over 3 yr averaged only 27%, likely reflecting net immobilisation in this recently broken site and accumulation of N in non-harvested portions of the crop. Cumulative recovery of N from biosolids in the harvested forage averaged only 11%. However, the fertiliser N equivalency of the biosolids N (ratio of recovery of biosolids N to urea N) was estimated at 41%, close to the predicted value of 40%. Forage yield and N uptake were similar for the LB and MF treatments, suggesting that actual biosolids N availability was similar to that predicted. Limited forage yield increase for the HB compared with the MB treatment early in the experiment, and high forage nitrate content for the HB treatment in the first year, suggest that the HB treatment initially supplied an excessive quantity of N. Both urea and biosolids applications increased cumulative uptake of other macro- and micro-nutrients, with forage Cu concentrations reaching values in the establishment year that may be of concern for some animal species. Monitoring of forage NO3 and Cu concentrations is advisable where biosolids are applied. Key words: Phleum pratense L., Dactylis glomerata, Bromus inermis, Bromus biebersteinii, soil N mineralisation, NO3 toxicity
Red soils of different origins from southwest Nigeria: Characteristics, classification, and management considerations
Authors: Okusami T. A. , Rust R. H. , Alao A. O.
Published: April 2011

Representative profiles of the Owena, Egbeda, Alagba, and Balogun series were studied. The Owena soil is formed in amphibolite whereas Egbeda and Balogun soils are formed in biotite gneiss derived parent materials. The Alagba soil is formed in sandstone parent rock. The main objectives were to characterize the soils and their clay fraction, and to classify and interpret soil properties for agricultural land use. Most soils exhibit 2.5 YR hues in subsurface horizons. A pedon formed in biotite gneiss has the highest dithionite Fe content and Fed/clay ratio. The relationships between clay content and Fed values vary according to parent material origin and, therefore, would have to be interpreted differently for soil weathering processes. Clay coatings were noticeable in some soil horizons of all pedons studied. Soils are generally medium to slightly acid with sandstone-derived soils being the most acid. The clay mineral suite in all soils is dominated by kaolinite with traces of 2:1 and 2:2 clay minerals, goethite, hematite, anatase, maghemite, and rutile. In addition, some soils contain trace amounts of gibbsite. Kandic horizons have been identified in all soils. The low charge properties of the soils reflect the intensely weathered clay mineral suite. The base status is probably influenced by the cropping system and therefore may tend to unnecessarily differentiate highly weathered soils at the order level. The Egbeda and Balogun series were classified as Rhodic Kandiudults, clayey-skeletal, oxidic and Rhodic Kandiudalfs, clayey-skeletal, oxidic, respectively. Others, Owena, and Alagba series, were classified as Typic Kanhaplohumults, clayey, oxidic and Rhodic Kanhaplustults, fine loamy or clayey, oxidic, respectively. In the FAO-Unesco legend, all soils become Rhodic Ferralsols. In addition, the Owena (with its nitic properties) is further classified as niti-rhodic Ferralsol. The two classification systems are at variance for highly weathered (variable charge property) soils and this difference will definitely influence management decisions depending on which system is used at any particular time. Soil attributes favorable for agricultural use include thick sola and favorable structures. Chemical properties suggest minimal fixation of phosphorus.

Key words: Dithionite Fe, kandic, oxidic, variable charge, ferralic, exchangeable Al
Nitrous oxide emission from agricultural soils
Authors: Beauchamp E. G.
Published: April 2011

A review of the salient features of N2O emissions from agricultural soils was done to assess our current understanding and associated problems. Nitrous oxide is an important globe warming gas and a destructive agent of ozone in the stratosphere. A major concern is the increasing contribution of chemical fertilizers to atmospheric N2O buildup. There is only a limited understanding of the contributions from manures, biological N2 fixation and crop residues. A recent estimate suggests that agriculture's share of N2O emissions is 80% although such estimates are highly uncertain because of imprecise data and the physical and biological complexities of the production process. As a product of the nitrification and denitrification process in soils, a major problem is our understanding of the proportion of N2O produced, i.e. the product ratios, although there is a good general understanding of the processes involved. Measurements of N2O emissions from the soil surface fail to take into account N2O flux from the bottom of the root zone into the subsoil and aquifers although they are generally considered to be significant. There is a need to apply newly available methodology and for combining this methodology and modelling together to predict N2O emissions on the landscape (or field) scale taking climate, soil and cropping variables into account. There is enough information available now to exercise some control of N2O emissions from cultivated soils. It is suggested that this be done focusing on factors that directly affect the soil microbes involved with the nitrification (NH4+, O2) and denitrification (NO3−, C, O2) processes. Cropping practices and some soil characteristic amendments are suggested herein for this purpose.

Key words: Denitrification, nitrification, emission control, gas ratios
Estimates of nitrous oxide emissions from agricultural fields over 28 months
Authors: Wagner-Riddle C. , Thurtell G. W. , Kidd G. K. , Beauchamp E. G. , Sweetman R.
Published: April 2011

Field studies conducted throughout the calendar year are needed to improve flux estimates for the greenhouse gas nitrous oxide (N2O). In this study, we report monthly N2O emissions measured using micrometeorological techniques and a Tunable Diode Laser Trace Gas Analyzer (TDLTGA). Nitrous oxide fluxes were measured at the Elora Research Station (20 km north of Guelph, Ontario) from July to November 1992, and from March 1993 to February 1995, giving a total of 2445 daily averages obtained during the full length of the experiment. The soil at the experimental site was a Conestogo silt loam (Gleyed melanic brunisol). Several fields were monitored including fallow, manured fallow, Kentucky bluegrass, alfalfa, barley, canola, soybeans and corn plots. Spring thaw emissions from fallow or ploughed plots measured from March to April ranged from 1.5 to 4.3 kg N ha−1, corresponding to approximately 65% of the total annual emission. Similar effects were not observed on the vegetated (alfalfa and grass) plots. The lowest total annual N2O emissions were measured for second year alfalfa (1 kg N ha−1 yr−1) and bluegrass (0 to 0.5 kg N ha−1 yr−1). Higher annual emissions (2.5 to 4.0 kg N ha−1 yr−1) were observed for corn, barley, canola, and fallow plots. Highest annual emissions were measured after addition of nitrogen in the form of animal manure on a fallowed plot (5.7 to 7.4 kg N ha−1 yr−1), and alfalfa residue by fall-ploughing (6.1 kg N ha−1 yr−1). Plot management during the previous year affected N2O emissions, particularly on the soybean plot (5.9 kg N ha−1 yr−1) that followed a manured fallow treatment. The micrometeorological technique used in this study was successful at quasi-continuous monitoring of N2O fluxes from several plots, and therefore, useful for detecting long-term effects of management on emissions.

Key words: Nitrous oxide, N2O fluxes, trace gases, agriculture, greenhouse gases
Les temps de résidence du carbone et le potentiel de stockage de carbone dans quelques sols cultivés français
Authors: Balesdent Jérôme , Recous Sylvie
Published: April 2011

In order to predict the potential of soils to store carbon in response to land use or climate changes, we measured the fluxes and distribution of residence times of C in French cultivated soils. We used the natural abundances in 13C and 14C to measure this distribution in long-term experiments of maize cultivation in France. 75% of the topsoil carbon had a mean residence time of 40 yr. Coarse particle-size fractions contained most of the younger carbon. A compartment of stable C was estimated using radiocarbon dating. Belowground plant material inputs stored as much as C as aboveground inputs. The effect of temperature on soil carbon mineralization affected only rate constants, with a Q10 = 3.1 constant in the range 1–25 °C. The data were summerized in a simple simulation model, which predicted a nil or low effect of climatic change on soil carbon storage in the next 50 yr. In France, land use changes will have more influence than atmospheric changes on C storage.

Key words: France, greenhouse gases, mineralization, model, soil carbon, storage, temperature
Deinking sludge influences biomass, nitrogen and phosphorus status of several grass and legume species
Authors: Fierro A. , Norrie J. , Gosselin A. , Beauchamp C. J.
Published: April 2011

In a greenhouse study, deinking sludge was evaluated as a soil amendment supplemented with four nitrogen (N) fertilization levels for the growth of the grasses Agropyron elongatum (Host.) Beauv. (tall wheatgrass), Alopecurus pratensis L. (meadow foxtail), Festuca ovina var. duriuscula (L). Koch (hard fescue), and four levels of phosphorus (P) for the growth of the legumes Galega orientalis Lam. (galega), Medicago lupulina L. (black medic), Melilotus officinalis (L.) Lam (yellow sweet clover). Fertilizers were applied on the basis of sludge level to maintain uniform carbon (C)/N or C/P ratios across sludge treatments. In one experiment, sand was mixed with 0, 10, 20 or 30% sludge while, in a second experiment, mineral soil was mixed with 0, 27, 53 or 80% sludge (vol/vol). In sand mixtures of 30 and 20% sludge, grasses had similar or greater growth than in unamended mineral soil when N was added at about 6.5 and 8.4 g kg−1 deinking sludge, respectively. For all legumes but Medicago lupulina, P at about 0.8 g kg−1 sludge was required for these sand mixtures. In soil mixtures of 53 and 27% sludge, grasses grew well when supplemental N was about 5.3 and 6.9 g kg−1 sludge, respectively. Legumes required P at 0.5 and 1.2 g kg−1 sludge, respectively. In general, growth was closely related to total amount of added N or P in spite of the wide range of C/N or C/P ratios. When growing in media amended with sludge, grasses needed higher tissue N concentration for an equivalent growth than in control soil; legumes had similar tissue P concentration. The grasses Agropyron elongatum and Alopecurus pratensis as well as the legumes Melilotus officinalis and Galega orientalis are promising species for field testing, based on dry matter production. Deinking sludge can be used as soil amendment when adequate N and P supplements are provided. Key words: Soil amendment, papermill sludge, Agropyron elongatum, Alopecurus pratensis, Festuca ovina, Medicago lupulina, Galega orientalis, Melilotus officinalis
Soil biological activity in recent clearcuts in west-central Alberta
Authors: Startsev N. A. , McNabb D. H. , Startsev A. D.
Published: April 2011

Soil biota response to changes in the soil physical environment following forest harvesting is relatively unknown in boreal forests. Soil biological activity was measured at four sites with Luvisolic soil following clear-cut forest harvesting. Aerobic respiration rate and cellulose decomposition in flooded soils were measured on soil samples collected from treatment plots subjected to tree removal only and tree removal associated with three levels of skidding activity immediately after clear-cut harvesting and after 1 and 2 yr. More than half of variation in respiration and cellulose decomposition rates was related to soil properties. Soil respiration rate increased significantly after 1 yr but was not affected by skidder traffic. Cellulose decomposition was highest in soil with air-filled porosity <0.10 m3m−3, and increased significantly with skidder traffic. Air-filled porosity measured in the field at the time of harvest indicated a poorly aerated environment that becomes wetter in subsequent years. The results imply that soil had biota well adapted to poor soil aeration. The development of a fully anaerobic soil environment following forest harvesting only occurred on compacted soil after heavy precipitation, but partial anaerobiosis of these boreal forest soils was common. Although partial anaerobiosis increased decomposition rate, it is considered sufficient to adversely affect the growth of plant roots and change the availability and mobility of nutrients. Key words: Forest harvesting, soil compaction, biological activity, respiration rate, decomposition rate, Alberta, boreal forests
Soil chemical changes and plant succession following experimental burning in immature jack pine
Authors: Lynham T. J. , Wickware G. M. , Mason J. A.
Published: April 2011

In 1975 and 1976, an experimental burning program was conducted in an immature stand of boreal jack pine (Pinus banksiana Lamb.) growing on level, granitic outwash sands in northern Ontario. Nine 0.4-ha plots were burned under a range of fire weather conditions and sampling was conducted to examine the effect of fire on soil chemical changes and revegetation. Results indicated that depth of burn (DOB) affected both soil chemical changes and plant succession on these pine sites. Vaccinium angustifolium Ait., Oryzopsis spp,. Waldsteinia fragarioides (Michx.) Tratt, Salix spp. and Viola adunca Sm. increased in cover at two levels of DOB but the increase was greatest at the lower DOB and decreased to pre-burn levels after 10 yr. Comptonia peregrina (L.) Coult., Epilobium angustifolium L., Polytrichum commune Hedw. and Amelanchier sanguinea (Pursh) DC. were not found in the pre-burn surveys but appeared after burning. Vegetation cover for these species was always higher at the deeper DOB but decreased almost to zero after 10 yr. Other species such as Pleurozium schreberi (Brid.) Mitt., Linnaea borealis L., Corylus cornuta Marsh., Cladina rangiferina (L.) Nyl. and Aralia nudicaulis L. were eliminated from the site and did not recover even after 10 yr. Soil pH increased 0.3 to 1.0 pH units in the organic and mineral soil layers. The rate of increase in pH was always steeper at the higher DOB and pH returned to pre-burn levels in the mineral soil layers after 10 yr. Immediately after burning, exchangeable Ca in the mineral soil layers doubled but 10 yr later, Ca returned to pre-burn levels. Phosphorus and K increased in the mineral soil, leveled off and were still elevated after 10 yr. Total Kjeldahl N was reduced by 50% in the organic soil while N in all mineral soils increased, and was still increasing after 10 yr. Except for immediate post-fire increases in pH, Ca and N, soil chemical changes were small or they rebounded to pre-burn levels 10 yr after burning. Therefore it is unlikely that these changes were the cause of the plant cover changes that persisted to 10 yr. Key words: Soil nutrients, plant succession, fire, depth of burn, jack pine
Seasonal trends in selected soil biochemical attributes: Effects of crop rotation in the semiarid prairie
Authors: Campbell C. A. , Biederbeck V. O. , Wen G. , Zentner R. P. , Schoenau J. , Hahn D.
Published: April 2011

Measurements of seasonal changes in soil biochemical attributes can provide valuable information on how crop management and weather variables influence soil quality. We sampled soil from the 0- to 7.5-cm depth of two long-term crop rotations [continuous wheat (Cont W) and both phases of fallow-wheat (F–W)] at Swift Current, Saskatchewan, from early May to mid-October, 11 times in 1995 and 9 times in 1996. The soil is a silt loam, Orthic Brown Chernozem with pH 6.0, in dilute CaCl2. We monitored changes in organic C (OC) and total N (TN), microbial biomass C (MBC), light fraction C and N (LFC and LFN), mineralizable C (Cmin) and N (Nmin), and water-soluble organic C (WSOC). All biochemical attributes, except MBC, showed higher values for Cont W than for F–W, reflecting the historically higher crop residue inputs, less frequent tillage, and drier conditions of Cont W. Based on the seasonal mean values for 1996, we concluded that, after 29 yr, F–W has degraded soil organic C and total N by about 15% compared to Cont W. In the same period it has degraded the labile attributes, except MBC, much more. For example, WSOC is degraded by 22%, Cmin and Nmin by 45% and LFC and LFN by 60–75%. Organic C and TN were constant during the season because one year's C and N inputs are small compared to the total soil C or N. All the labile attributes varied markedly throughout the seasons. We explained most of the seasonal variability in soil biochemical attributes in terms of C and N inputs from crop residues and rhizodeposition, and the influences of soil moisture, precipitation and temperature. Using multiple regression, we related the biochemical attributes to soil moisture and the weather variables, accounting for 20% of the variability in MBC, 27% of that of Nmin, 29% for LFC, 52% for Cmin, and 66% for WSOC. In all cases the biochemical attributes were negatively related to precipitation, soil moisture, temperature and their interactions. We interpreted this to mean that conditions favouring decomposition of organic matter in situ result in decreases in these attributes when they are measured subsequently under laboratory conditions. We concluded that when assessing changes in OC or TN over years, measurements can be made at any time during a year. However, if assessing changes in the labile soil attributes, several measurements should be made during a season or, measurements be made near the same time each year. Key words: Microbial biomass, carbon, nitrogen, mineralization, water-soluble-C, light fraction, weather variables
The return of the "other" soil scientists
Authors: Warkentin B. P.
Published: April 2011

Soils knowledge through the ages accumulated from direct experience through contact with the soil, whether preparation of a seed bed, building roads, or founding buildings. Soil uses were tied with religious observances. Gatherers proceeding to become settled agriculturalists would have used soils knowledge to choose farming sites. The knowledge accumulated by practitioners was written down and extended to others in print during the past two millennia. This changed about 150 years ago, when research studies using the scientific method became the dominant source of soils information. By 1900 this pattern of analytical thought was set. This was fostered by, or at least coincided with, increasing application of technology to use of soils during the second third of the 20th century, and became the dominant source of soil knowledge. We are now seeing a return to the importance of the "other" soil scientists in increasing soil knowledge. There is increasing appreciation of the importance of indigenous soil knowledge; on-farm research where soil users perform their own controlled experiments is becoming an important source of information on soil management. Parallelling this change have been changes in attitude toward soil as a resource, toward conservation, and toward the appreciation of soil performing unique ecological and spiritual functions of concern to mankind. Holistic approaches to soil are again becoming mainstream. As we grapple with global problems such as soil degradation, we will see all soil scientists making contributions to soil knowledge. Key words: Soil knowledge, soil users, ecological functions
Nutrient losses to soil from field storage of solid poultry manure
Authors: Zebarth B. J. , Paul J. W. , Chipperfield K.
Published: April 2011

The study was done to quantify the effect of uncovered field storage of solid poultry manure in south coastal British Columbia on a site where solid Turkey manure was stored uncovered each fall and winter for approximately 6 yr. The soil was sampled to 370 cm depth in a transect with six sampling locations: two in the manure storage area, and two on either side of the manure storage area. The soil was analyzed for the concentrations of total organic C, total Kjeldahl N, ammonium, nitrate, K, P, Mg, and Na in addition to soil pH and electrical conductivity. The mass of nutrients to 370 cm depth was 39 700 and 330 kg NH4+–N ha−1, 500 and 480 kg NO3−–N ha−1, 36 400 and 1440 kg K ha−1, 12 100 and 2190 kg P ha−1, 3150 and 1140 kg Mg ha−1 and 9850 and 975 kg Na ha−1 for the manure storage and non-storage sampling locations, respectively. The depth weighted average soil pH was 8.4 and 4.7 and average soil electrical conductivity was 3.3 and 0.3 dS m−1 for the manure storage and non-storage sampling locations, respectively. The lack of an increase in soil nitrate concentration in the manure storage area was attributed to concentrations of free ammonia in soil solution toxic to nitrifying bacteria. The results highlight the high potential for nutrient loss from uncovered fall and winter field storage of poultry manure in south coastal British Columbia. Key words: Turkey manure, soluble C, soil ammonium, free ammonia, electrical conductivity
Economics of N and P fertilization to restore wheat yields on three artificially eroded sites in southern Alberta
Authors: Smith E. G. , Peng Y. , Lerohl M. , Larney F. J.
Published: April 2011

An important economic concept in the evaluation of soil conservation is the ease with which production inputs can be substituted for one another. This concept and economic optimum application rates of N and P fertilizer for wheat grown after fallow were applied to three artificially eroded soils in southern Alberta. Each site had topsoil removed to depths of 0, 10 and 20 cm. Four rates of N (0, 50, 75 and 100 kg ha−1) and three rates of P (0, 11 and 22 kg ha−1) were applied to each eroded depth. There were four replications. Fertilizer N and P did not easily substitute for the loss of topsoil. The economic optimum level of N and P was nearly constant across depths of eroded topsoil. Increases in fertilizer N and P applied to eroded soils were primarily to replace lost soil nutrients. It was not economical to apply inorganic fertilizer on these eroded soils at rates that would restore grain yields. Key words: Eroded soil, economics, inorganic fertilizer, wheat
Indicator of risk of water contamination by P for Soil Landscape of Canada polygons
Authors: Bolinder M. A. , Simard R. R. , Beauchemin S. , MacDonald K. B.
Published: April 2011

The indicator of risk of water contamination (IROWC) is a component of the Agriculture and Agri-Food Canada Agri-Environmental Indicator project. The IROWC measures progress in reducing the risk of water contamination from agricultural activities, focusing on N and P. The objective of this study was to propose a methodology for an IROWC-P applicable at the Soil Landscape of Canada (SLC) polygon level (1:1 000 000 map scale) using an indexing approach. The sources of data included Census of Agriculture, SLC and soil survey databases and provincial soil test data. The IROWC-P considers the following site characteristics: soil erosion and potential for overland flow, annual P balance (crop residues, manure and inorganic fertilizer), soil test P (STP) and degree of soil P saturation (DSPS). IROWC-P classifies polygons for their potential risk of P transfer to surface waters according to five vulnerability classes (i.e., very low, low, medium, high and very high). The methodology was tested on a pilot basis for selected SLC polygons in the province of Quebec using 1981 and 1991 census data. Preliminary results indicated that the proposed methodology showed some sensitivity to changes in agricultural practices between 1981 and 1991 and reflected differences in risk of P contamination from areas of intensive compared to areas of extensive agriculture. The difference between the selected areas was mainly attributed to the STP, DSPS, manure and inorganic fertilizer P polygon characteristics. The temporal variations in the IROWC-P ratings were attributed mainly to the manure and inorganic fertilizer P polygon characteristics. Key words: Degree of soil P saturation, soil P index, environmental risk, soil test P
Use of moored acoustic instruments to measure short‐term variability in abundance of Antarctic krill
Authors: Brierley Andrew S. , Saunders Ryan A. , Bone Douglas G. , Murphy Eugene J. , Enderlein Peter , Conti Stéphane G. , Demer David A.
Published: April 2011

Upward‐looking acoustic Doppler current profilers (ADCPs) (300 kHz) and echosounders (125 kHz) were deployed on moorings at South Georgia to measure abundance of Antarctic krill continuously over several months. Echoes from krill were identified using the theoretical difference in echo intensity at 300 and 125 kHz and scaled to krill density using target strengths appropriate for krill in the region: krill size was determined from diet samples from furseals and penguins foraging near the moorings. A method using water flow past the moorings was developed to convert time‐based acoustic observations of krill to area‐based abundance estimates. Flow past the stationary moorings was treated analogously to motion along‐track of a research vessel through a nominally stationary body of water during a conventional survey. The moorings thus provide a Eulerian view of variation in krill abundance. This is ecologically instructive for South Georgia, where krill are generally passive drifters on currents and where temporal fluctuations in abundance have significant consequences for krill‐dependent predators. Moorings were positioned on routine research vessel survey transects, and validity of the mooring method was assessed by comparison of mooring and vessel observations. Krill density estimates from the moorings were not statistically different from vessel estimates in adjacent time periods. A time series of krill density from a mooring revealed step‐changes that were not seen during short‐term vessel surveys. Moorings deliver data over time scales that cannot be achieved from research vessels and provide insight on environmental factors associated with variation in krill abundance at South Georgia. Mooring data may aid ecosystem‐based management.
Evaluation of effective shore level as a method of characterizing intertidal wave exposure regimes
Authors: Gilman Sarah E. , Harley Christopher D.G. , Strickland Denise C. , Vanderstraeten Olivier , O'Donnell Michael J. , Helmuth Brian
Published: April 2011

Wave splash modifies the duration and timing of aerial exposure of intertidal organisms, influencing patterns of vertical zonation, thermal stress, and the consequences of climate change. Harley and Helmuth (Limnol. Oceanogr. 48:1498‐1508, 2003) described a method for measuring effective shore level (ESL), a metric that combines the influence of wave splash and tidal regime on patterns of emersion and immersion. They identified immersion events as sharp drops in temperature recorded by submersible dataloggers and compared the tide height at the time of the temperature drop to the wave height recorded by an offshore buoy. Here we explore the generality of this method at 10 sites along the Pacific coast of North America spanning 14° of latitude. We deployed miniature temperature loggers at fixed intertidal heights at each site and recorded temperatures at intervals of 5 to 15 min for periods of up to 5 years. We use these data to explore the effects of different approaches to calculating temperature drops and wave heights, as well as variation in the buoy location, on ESL calculations. We present a software program (SiteParser) that can be used to identify temperature drops in a datalogger time series and also calculate daily and monthly summary statistics of temperature. We show that ESL parameters provide a useful metric for comparing the effects of wave action on immersion patterns within sites. We also introduce a metric of average wave run‐up that can be used to compare the effect of wave action on immersion patterns among more distant locations.
Accurately measuring the abundance of benthic microalgae in spatially variable habitats
Authors: Grinham Alistair R. , Carruthers Tim J. B. , Fisher Paul L. , Udy James W. , Dennison William C.
Published: April 2011

Although many studies measure the abundance of benthic microalgae (BMA), at the meters squared scale, comparing these studies is difficult due to the variety of sampling, extraction, and analysis techniques. This difficulty is exacerbated by the fact that BMA abundance has high spatial and temporal variability, at all spatial scales. A suitable standard sampling regimen would reduce variation in estimates due to different sample collection and processing greatly facilitating comparisons between studies. This study examined the effect of varying the volume of extraction solvent, sampling core diameter, and sample replication on BMA biomass estimates. Key findings, applicable to all spatial scales, to accurately determine biomass were the use of a minimum sediment to extraction solvent ratio of 1:2 and use of a sampling core diameter of 19 mm. Across a wide range of sediment types, at the meters squared scale and using spectrophotometric techniques, a minimum replication number of 8 was found to be appropriate. We report the significant effect coring depth and units of expression have on BMA biomass estimates across a range of sediment types, highlighting the potential pitfalls when comparing studies.
Measurements of optical absorption by chromophoric dissolved organic matter using a point‐source integrating‐cavity absorption meter
Authors: Röttgers Rüdiger , Doerffer Roland
Published: April 2011

The light absorption of 0.22‐µm filtered seawater samples from the North Sea and the Atlantic Ocean was measured by a point‐source integrating‐cavity absorption meter (PSICAM), and the results were compared with measurement in a spectrophotometer. The absorption coefficient of this Gelbstoff or chromophoric dissolved organic matter (CDOM) ranges from high values of 0.103 to 0.519 m−1 at 442 nm for samples from the North Sea to very low values of 0.004 to 0.046 m−1 for samples from the Atlantic Ocean. At these low values, the influence of sample temperature and salinity on water absorption was significant. Hence, instrument‐specific temperature and salinity coefficients were determined and, subsequently, used for correcting absorption data. Spectrophotometrically determined absorption was significantly higher at shorter wavelengths (< 442 nm) than absorption measured by the PSICAM, probably showing a significant influence of scattering by small particles remaining in the sample after filtration. At wavelengths between 442 and 500 nm, the correlation of PSICAM and spectrophotometer followed the 1:1 correspondence, whereas at longer wavelengths, the absorption was below the detection limit of the spectrophotometer. A similar agreement was obtained for the exponential slope of the CDOM absorption. The PSICAM matches the spectrophotometer results but is more sensitive and not affected by scattering. It will improve our ability to determine CDOM absorption in oligotrophic waters for the visible light spectral region.
Assessing pelagic and benthic metabolism using free water measurements
Authors: Van de Bogert Matthew C. , Carpenter Stephen R. , Cole Jonathan J. , Pace Michael L.
Published: April 2011

Automated in situ sensors for measuring changes in dissolved oxygen (DO) at high frequency have facilitated estimates of gross primary production (GPP) and respiration (R) in aquatic systems. Lake researchers usually rely on a single sensor for these estimates, but such point measurements may miss important spatial heterogeneity in within‐lake processes and may not accurately represent systemwide values of metabolism. Here we combine simultaneous measurements of metabolism using DO sensors along transects from the shore to the center of a lake with a spatial model to better understand the underlying heterogeneity in processes contributing to whole‐lake epilimnetic metabolism. We use this model to achieve better estimates of epilimnetic GPP and R and to determine the relative contributions of benthic‐littoral vs. pelagic processes to these estimates. We compared the spatially explicit process‐based model to estimates of metabolism from both a single sensor at the lake's center and a spatially explicit averaging of multiple sensor sites. Estimates of both GPP and R varied on average 2.5‐ to 3.2‐fold from site to site within the same lake, whereas variations were sometimes as high as 6‐ to 7‐fold. Estimates of GPP and R near the perimeter of lakes were on average greater than measurements in the middle of the lake. Our model estimates that benthic‐littoral processes accounted for ~40% of epilimnetic GPP and R. A single, centrally located sensor often misses a significant component of this benthic metabolism and accounts for only ~81% of lakewide GPP and R.
Estimating the contribution of organic bases from microalgae to the titration alkalinity in coastal seawaters
Authors: Martín Hernández‐Ayon J. , Zirino Alberto , Dickson A. G. , Camiro‐Vargas Tania , Valenzuela‐Espinoza E.
Published: April 2011

This study reports the potential contribution of organic bases to the alkalinity of seawater samples. The concentration of organic bases in these samples was inferred from the difference between the measured alkalinity and that calculated from a knowledge of pH and concentrations of the various inorganic acid‐bases species such as total carbon, total boron, and so on. Significant concentrations of such organic bases were measured in cultures of the marine microalgae Rhodomonas sp. (800 µmol kg−1) and Isochrysis aff. Galbana (400 µmol kg−1), as well as in three marine environments (northern gulf of California, México; San Quintín Bay, B.C., Mexico; and San Diego Bay). These three sites are characterized by significant biological activity and restricted mixing, and the organic bases were found at concentrations greater than 50 µmol kg−1 in each of these three locations.
Measurement of the stable isotope ratio of dissolved N2 in 15N tracer experiments
Authors: Hamilton Stephen K. , Ostrom Nathaniel E.
Published: April 2011

Stable isotope addition experiments seeking to trace the denitrification of combined forms of nitrogen (N) to gaseous N2 in aquatic environments typically need to measure the stable isotope ratio of dissolved nitrogen gas. This measurement presents challenges because of the potential for contamination of samples by N in air, and because field experiments conducted in situ often do not produce a marked enrichment in the isotope ratio of the N2 pool. Field experiments also require numerous samples, sometimes processed under arduous conditions, and thus methods have to be convenient and low in cost. This paper describes the methods for sampling and measurement of the N isotope ratio of dissolved nitrogen that were developed for the isotope addition experiments in the Lotic Intersite Nitrogen Experiment (LINX), a cross‐site study examining N biogeochemistry in headwater streams. Headspace equilibration was performed in the field and gas samples were stored in re‐evacuated glass vials (Exetainers). Samples were processed and stored underwater to minimize the potential for contamination of samples by air. Isotope ratios were measured using a gas chromatograph interfaced to the isotope ratio mass spectrometer and equipped with a custom sample entry system.
Measuring urease activity in aquatic environmental samples
Authors: Solomon C. M. , Alexander J. A. , Glibert P. M.
Published: April 2011

The current published method for measuring urease activity in phytoplankton involves measuring the hydrolysis of urea into ammonium. The method was previously optimized for studies of phytoplankton cultures, not for natural assemblages of phytoplankton. We tested several steps of the method using water samples from two distinct sites to optimize the urease assay method for field studies. We found interference of NH4+ from extraction and assay reagents in the current published protocol, leading to inconsistencies in rates of urease activity. We recommend a reduction in the concentration or removal of two of these reagents. We also found a biomass effect and recommend collecting smaller sample volumes in field studies. These improvements lead to values that may be more reflective of rates of urease activity in situ, but unfortunately more variable due to the low volumes used.
The use of the Laser Optical Plankton Counter to measure zooplankton size, abundance, and biomass in small freshwater lakes
Authors: Finlay Kerri , Beisner Beatrix E. , Barnett Allain J.D.
Published: April 2011

The Optical Plankton Counter (OPC) has been used in a variety of environments since its introduction over decade ago, but its use in freshwater lakes has been limited by high densities of zooplankton and detritus. The newer Laser Optical Plankton Counter (LOPC) has several modifications from its predecessor, and the goal of this study was to examine whether it could be used to measure average size (µm equivalent spherical diameter, ESD), abundance (particles L−1), and biomass (µg dry weight L−1) of zooplankton in samples from 18 lakes in the Eastern Townships region of Quebec, Canada. The LOPC slightly overestimated the size of copepods, and consistently underestimated Daphnia by approximately 25% ESD. Densities and biomass of net samples were very similar between the LOPC lab version and traditional microscope analyses suggesting that the LOPC can be reliably used to process preserved net samples. When the LOPC was towed in situ vertically in Lake Memphremagog, QC, Canada, estimated zooplankton abundances were ten times net sample values from the same water column, but similar abundances were found between the LOPC and pumped zooplankton samples at 2 m depth. These results indicate that the LOPC may be well suited for analyses of zooplankton abundance and biomass in productive freshwater lakes.
Fractionation of sediment phosphorus revisited: II. Changes in phosphorus fractions during sampling and storing in the presence or absence of oxygen
Authors: Lukkari Kaarina , Leivuori Mirja , Hartikainen Helinä
Published: April 2011

The purpose of this study was to evaluate the sensitivity of a phosphorus (P) fractionation procedure on sampling practices and other sources of error in the characterization of the chemical status of P in noncalcareous sediments rich in humic compounds and iron (Fe). We investigated the effects of nitrogen gas (N2) shielding on the stability of various P fractions during sampling and various periods of sample storage on both oxic and reduced sediments. In addition, we studied storage‐induced changes in preserved or unpreserved extracts from different fractionation steps. Sampling and storage conditions were critical factors in P fractionation studies. During sampling, sample storage, and extraction, the N2 atmosphere (atm) protected samples from oxidation and consequent changes in P forms, especially in the redox‐sensitive form. Long‐term storage without N2‐shielding caused the most drastic changes in oxic sediment, whereas the reduced sediment protected with N2 experienced only minor changes. Extracts preserved with acid can be stored for at least 1 week without significant changes. The extraction results of P and other elements obtained with both oxic and reduced sediment samples supported the biogeochemical basis of the fractionation procedure, demonstrated by the behavior of Fe and Fe‐bound P in sediment originating from and treated in different oxygen (O2) conditions. Despite a few shortcomings, with careful laboratory work and avoidance of sample oxidation during sampling and storage, the fractionation procedure and working practices used seem to provide reliable results and valuable information on the chemical character of sediment P.
Miniaturized photometrical methods for the rapid analysis of phosphate, ammonium, ferrous iron, and sulfate in pore water of freshwater sediments
Authors: Laskov Christine , Herzog Christiane , Lewandowski Jörg , Hupfer Michael
Published: April 2011

Pore water analysis is a challenge for routine analysis methods, because of the small sample volume available and large sample numbers required for a high spatial resolution. To overcome the restrictions of established methods, this study presents a miniaturized photometrical method for the rapid analysis of phosphate, ammonium, ferrous iron, and sulfate in pore water of lake sediments. The method can cope with large sample sets (> 1000) and minimizes the sample volume to about 250 µL. Standard photometric methods were modified for the use of microtiter plates (microphotometry), which allow the simultaneous determination of up to 100 samples by a microtiter plate reader. The advantage of this analytical technique is the minimal sample consumption, which enables new approaches for pore water sampling and analysis on a microscale level. In combination with a 2‐dimensional dialysis sampler, it is now possible to obtain spatial patterns of pore water concentrations (SRP, NH4+, Fe2+, SO42−) with a high vertical and lateral resolution (9 mm). This approach shows the common 1‐dimensional view of pore water profiles to be insufficient. Furthermore, the application examples yield new insights on lateral heterogeneity as well as nutrient mobilization and redox processes associated with the formation of microzones around biogenic structures, such as roots or macrofaunal burrows.
Measurement of acid polysaccharides in marine and freshwater samples using alcian blue
Authors: Thornton Daniel C.O. , Fejes Elizabeth M. , DiMarco Steven F. , Clancy Kristen M.
Published: April 2011

Extracellular polymeric substances (EPS), including transparent exopolymer particles (TEP), play an important role in ocean biogeochemistry. This paper describes a simple method for measuring acid polysaccharides (APS), which are the major components of TEP and other EPS. APS were stained and precipitated with alcian blue, the precipitate was retained on a 0.2 µm pore size filter and the absorbance of the filtrate was measured at 610 nm using a spectrophotometer. The color of the filtrate was inversely proportional to the amount of APS in the sample. This relationship was linear and was calibrated using gum xanthan or alginic acid as a standard. Salts interfered with the assay; therefore samples from marine environments were dialysed (1000 Da molecular weight cut‐off [MWCO]) before addition of alcian blue. The assay was applied to whole water samples to a give a total concentration of APS (particulate plus dissolved) in freshwater ponds, and cultures of marine protists and seawater from the continental shelf of the northern Gulf of Mexico. The assay was effective in measuring dissolved extracellular APS after removal of particulates by filtration, although in marine samples APS molecules smaller than the MWCO of the dialysis tubing (1000 Da) were not measured. The new method has potential in studies on the biogeochemistry of particulate and dissolved APS, including TEP and its precursors.
On the determination of mass transfer in a concentration boundary layer
Authors: Nishihara Gregory N. , Ackerman Josef D.
Published: April 2011

The mass transfer of scalar quantities (e.g., O2 and nutrients) in aquatic environments is an important and complex process involving diffusion and advection. In a flowing environment, concentration boundary layers (CBL) occur above the surfaces of organisms when they are a sink or source of scalars. In this study, we used an O2 microsensor to profile the O2 concentrations in the CBL above photosynthesizing freshwater macrophyte (Vallisneria americana) leaves that were oriented parallel to the flow in a recirculating flow chamber at 0.5 and 3.3 cm s−1. Measured O2 profiles were nonlinear indicating the effect of higher order processes near the surface. O2 flux (Jobs) was estimated from these profiles by two nonlinear techniques, hyperbolic tangent and logarithmic models, and the commonly applied linear model. An integrated measurement of O2 flux (Jint) for each leaf was also measured independently in a stirred chamber. Whereas Jobs determined from the hyperbolic tangent (0.42 ± 0.04 [mean SE] µmol m−2 s−1) and linear (0.31 ± 0.04 µmol m−2 s−1) models overestimated and underestimated Jint (0.37 ± 0.05 µmol m−2 s−1), respectively, and were not velocity dependant, the hyperbolic tangent model provided the best fit (r2 = 0.88) compared with the linear model (r2 = 0.77). In addition, the slope of the regression against Jint (1.08 ± 0.06) was closest to 1.00 (i.e., a “perfect” fit). The logarithmic model varied with velocity and overestimated Jobs (0.98 ± 0.22 µmol m−2 s−1 at 0.005 m s−1 and 0.90 ± 0.18 µmol m−2 s−1 at 0.033 m s−1). These results were confirmed in an analysis of 21 published O2 concentration profiles measured next to sediments, microbial biofilms, planktonic algae, and epilithic algae. We would, therefore, recommend the hyperbolic tangent model to estimate mass transfer in a CBL.
An assessment of the measurement of phytoplankton respiration rates from dark 14C incubations
Authors: Williams Peter J. le B. , Lefèvre Dominique
Published: April 2011

Marra and Barber (2004) have proposed a simple procedure for calculating phytoplankton respiration from measurements of the loss of 14C from the particulate fraction during dark post‐incubations. We identify the necessary assumptions implicit in their approach, the primary ones being: (1) the respiration rates in the light must be the same as those in the dark, (2) the specific radioactivity (14C/12C) of the respiratory CO2 released in the dark must be known or assumed to be the same as the seawater carbonate, and (3) only phytoplankton respiration gives rise to the change in the 14C content of the particulate fraction in the dark. In most cases, with a combination of theory and observations, we have been able to make a first order quantitative assessment of the error associated with these assumptions and their consequences. When P/R ratios are ≥3, we conclude that uncertainties deriving from the necessary assumption that specific activity of the CO2 produced is the same as that of the labeled seawater bicarbonate, give rise to underestimates of respiration in the region of 5%–20%. The errors due to loss of 14C from the particulate fraction, other than phytoplankton respiration, will give overestimates as high as 20–40%. At P/R ratios >3, the non‐photosynthetic assimilation of CO2 will give insignificant errors. The above generalizations will not hold when photosynthetic rates are low both in absolute terms and in relation to respiration.