bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent Major Declines in Zooplankton Populations in the Inshore Region of Lake Michigan: Probable Causes and Implications
Authors: Evans Marlene S.
Published: October 2008

Summer Zooplankton communities in the inshore region of southeastern Lake Michigan were dominated by small species during the 1970s, suggesting that size-selective fish predation pressures were intense. Abundances of alewife (Alosa pseudoharengus), the dominant planktivore in the 1970s, declined in recent years, especially over 1982–84. Despite decreased alewife predation, small zooplankton taxa continued to predominate. Moreover, zooplankton standing stocks declined 10-fold during 1982–84, suggesting that predatory pressures had intensified. Concurrent with the alewife population decrease was a major increase in yellow perch (Perca flavescens) abundances. As a probable consequence of intense predation pressures exerted by abundant yellow perch, zooplankton standing stocks were severely reduced. Yellow perch populations may have been adversely affected by food limitation, especially in summer 1984 when zooplankton standing stocks were only 3% of their average level over 1975–81.
Individual Parameter Perturbation and Error Analysis of Fish Bioenergetics Models
Authors: Bartell S. M. , Breck J. E. , Gardner R. H. , Brenkert A. L
Published: October 2008

We quantified the sensitivity of predicted rates of growth and consumption to parameter variation for models of yellow perch (Perca flavescens), largemouth bass (Micropterus salmoides), and alewife (Alosa pseudoharengus). We used statistical analyses of the results of Monte Carlo simulations to rank parameter importance. The order of parameter importance was model specific, although the results emphasized the need for accurate estimation of the realized fraction of maximum consumption rate (P) and allometric parameters for consumption (a1, b1) and respiration (a2, b2). Excretion and egestion parameters contributed little to prediction errors. The Monte Carlo methods were used to examine the relative importance of parameter variation and diet composition, an external forcing function, on forecasts of alewife growth. If standard deviations of model parameters were known within 2% of their expected values, uncertainty in diet composition could contribute as much as 47% of the variance in predicted alewife weight. When standard deviations of model parameters are realistically defined, diet uncertainty contributed less than 10% of the variance in predicted weight.
Effect of Aroclor 1254 and Mirex on Estradiol-lnduced Vitellogenin Production in Juvenile Rainbow Trout (Salmo gairdneri)
Authors: Chen Thomas T. , Reid P. C. , Beneden R. Van , Sonstegard R. A.
Published: October 2008

A rapid sensitive assay for vitellogenin using rocket immunoelectrophoresis was developed in juvenile rainbow trout (Salmo gairdneri) induced with 17β-estradiol. The assay detected vitellogenin serum levels as low as 0.05 mg/mL. Significant reduction of vitellogenin levels were detected in rainbow trout fed for 6 mo on diets contaminated with Aroclor 1254, Mirex, or a mixture of Aroclor 1254 and Mirex.
Growth Decline in Subyearling Brook Trout (Salvelinus fontinalis) after Emergence of Rainbow Trout (Salmo gairdneri)
Authors: Rose G. A.
Published: October 2008

In a tributary of Lake Superior, brook trout (Salvelinus fontinalis) subyearlings, after emergence in April, initially gained length at 0.51 mm/d and weight at a specific growth rate per day (G) of 0.058. After the emergence of larval rainbow trout (Salmo gairdneri) in June, however, length increments of brook trout declined to 0.05 mm/d and G was reduced to 0.005. During August, brook trout growth rebounded somewhat (0.12 mm/d; G = 0.008). Rainbow trout subyearlings, by contrast, grew at relatively constant rates of 0.42 mm/d and G of 0.040, from emergence until September. By late August, mean weights of brook and rainbow trout, 2026 and 2282 mg, respectively, did not differ significantly. Stream positions occupied by brook trout, characterized by flows of less than 20 cm/s and depths of less than 40 cm, did not change over the first summer. During June and July, stream positions of rainbow trout subyearlings coincided with those of brook trout. During August, however, rainbow trout moved to faster waters (>20 cm/s). The taxonomic composition of the diets of the two species did not differ. Mean width of food items consumed was linearly correlated with the total length of the fish (r = 0.97). The range of sizes of items eaten by the two species overlapped considerably by mid-June. For brook trout, mean food size increased, and amount consumed decreased, after the emergence of rainbow trout larvae. Growth reduction during the first summer, an outcome of interspecific competition for food and space, may result in increased overwintering mortality of fish at high latitudes, and be a mechanism by which brook trout are excluded by rainbow trout.
Size-Limited Predation, Winterkill, and the Organization of Umbra–Perca Fish Assemblages
Authors: Tonn William M. , Paszkowski Cynthia A.
Published: October 2008

We compared population densities and size structures of central mudminnows (Umbra limi) occurring with and without yellow perch (Perca flavescens) in six small lakes in northern Wisconsin over a 6-yr period. Our observations suggested that a size-dependent predator–prey interaction was a major mechanism organizing these assemblages. Densities of mudminnows cooccurring with perch averaged 12% of populations in mudminnow-only lakes. Large mudminnows (≥76 mm total length) predominated in populations with perch whereas smaller fish predominated in single-species assemblages. Following severe winterkills of adult perch in two lakes, mudminnow densities increased significantly due to high survival and recruitment of yearlings. Increases in small mudminnows lasted only a year: densities and size distributions returned to prewinterkill patterns when perch that had survived winterkill attained lengths >13 cm. To examine the role of size-limited predation, we performed an experiment in 2000-L tanks, varying the initial size distributions of mudminnows and perch and measuring size-specific survival among mudminnows. Predation in the experimental populations was greatest when large perch (121–180 mm) were with populations of predominantly small mudminnows (<76 mm); smaller perch (114–132 mm) were significantly less successful as predators whereas large mudminnows were significantly less vulnerable to predation by even large perch. Despite this interaction, central mudminnows coexist at low densities with yellow perch; possible factors permitting coexistence are fish sizes and spatial and structural refuges.
Modification de la bioaccumulation du sélénium chez Mytilus edulis en présence du mercure organique et inorganique
Authors: Pelletier Emilien
Published: October 2008

Studies of the simultaneous bioaccumulation of selenium and mercury in the blue mussel, Mytilis edulis, in the presence of TiO2 as carrier have shown that there is an interaction between the two elements. We measured the bioaccumulation rates of dissolved selenite (Na2SeO3) and adsorbed organic selenium (C8H7O2Se)2 and determined the impact of the presence of mercury (HgCl2 and [(CH3Hg)3O]OH) in the environment. Mussels measuring 3.6 ± 0.2 cm were distributed in nine contamination tanks with continuously circulating seawater and were exposed to organic or inorganic selenium at a concentration of 50 μg Se∙L−1 for periods of 15–50 d. Some of the tanks were simultaneously exposed to high concentrations of organic and inorganic mercury (3.0 and 30 μg Hg∙L−1, respectively). When mercury was not present, the mussels accumulated the inorganic selenium at a slow rate (0.12 ng Se∙g−1∙d−1), but did not accumulate the organic selenium. When inorganic mercury was added to the water at 30 μg Hg∙L−1, the accumulation rate of inorganic selenium doubled (0.24 ng Se∙g−1d−1), while it tripled (0.40 ng Se∙g−1d−1) when methyl mercury was added at 3.0 μg Hg∙L−1. Even the adsorbed organic selenium seemed to become bioavailable in the presence of methyl mercury, and was accumulated at a rate of 0.15 ng Se∙g−1d−1. However, the phenomenon is not reciprocal, that is, the presence of selenium, no matter what its concentration or chemical nature, had no effect on the accumulation rate of mercury. No toxic effects were observed where selenium was administered alone, but the toxic effects of mercury were observed in all mussels exposed to it. Selenium showed none of the adverse effects previously observed in other animal species.
Aluminum Speciation in Some Synthetic Systems: Comparison of the Fast-Oxine, pH 5.0 Extraction and Dialysis Methods
Authors: Lalande Hélène , Hendershot William H.
Published: October 2008

A procedure for the fractionation of aqueous aluminum was evaluated on synthetic systems using 8-hydroxyquinoline (oxine) at pH 5.0 or 8.3 and reaction times of 15 s or 60 min. For comparison of the speciation of the most reactive forms of Al, dialysis tubing with a molecular weight cutoff of 1000 was used. In the hydroxide and fluoride systems the fast-oxine, pH 5.0 method clearly distinguishes between different forms of Al. In systems containing citrate and oxalate, low molecular weight organic complexing agent, the fast-oxine method produced a clearer distinction between inorganic and organically complexed Al than did the dialysis method. In contrast, the Al species in systems containing fulvic acid and leaf litter leachate were much more clearly differentiated by the dialysis method. The fast-oxine, pH 5.0 reaction appears to extract a fraction of the organically complexed Al; this supports the hypothesis that natural organic complexes have a wide range of bond strengths to metal ions.
Importance of Picoplankton in Lake Superior
Authors: Fahnenstiel Gary L. , Sicko-Goad Linda , Scavia Donald , Stoermer Eugene F.
Published: October 2008

In Lake Superior, approximately 50% of total primary production is attributable to phytoplankton that pass through a 3-μm screen. The <3-μm size class is dominated by eukaryotic flagellates, nonmotile eukaryotic cells (1 μm), and chroococcoid cyanobacteria. Approximately 20% of total primary production is attributable to orange autofluorescent chroococcoid cyanobacteria (mean size = 0.7 μm) as determined by size fractionation and track autoradiography. These small prokaryotes exhibited abundances of 42 000 and 56 000 cells∙ml−1, maximum photosynthetic rates of 7 and 6 fg∙cell−1∙h−1, and growth rates of 1.5 and 0.8∙d−1 in the epilimnion and hypolimnion, respectively. A significant portion of this picoplankton (<1 μm) production may be consumed by heterotrophic protozoans in a "microbial loop."
Sports Angler Preferences for Alternative Regulatory Methods
Authors: Renyard T. S. , Hilborn Ray
Published: October 2008

Successful implementation of fisheries regulations is difficult when user groups strongly oppose the regulations. We show that some types of sports fishing regulations (seasonal closure, daily bag limits) are not generally acceptable to British Columbia salmon sports anglers and that preference for other regulations depends upon the frequency of fishing. Infrequent anglers prefer low annual bag limits, while frequent anglers prefer larger size limits and gear restrictions.
Image Analysis Techniques for the Study of Fish School Structure from Acoustic Survey Data
Authors: Reid D. G. , Simmonds E. J.
Published: October 2008

A new image analysis based processing system is described for acoustic fisheries data. In a series of a simple steps the system can identify schools and display their positions on a screen. Modifications to the identification process can be entered interactively by the operator. The system provides a wide range of parameters associated with each school, e.g., height, width, depth, shape, density, that can be entered into a database. Applications of this type of system for improving the accuracy of acoustic stock assessment, studying fish distribution patterns, and elucidating fish schooling behaviour are discussed.
Inhibition of Chorion Expansion and Preservation of Fertility in Goldfish (Carassius auratus) Eggs by Protease Inhibitors
Authors: Hsu Sheau-Yu , Goetz Frederick William
Published: October 2008

The in vitro effects of protease inhibitors on chorion expansion and the fertility of goldfish (Carassius auratus) eggs were investigated. Expansion of the chorion in ovulated eggs was blocked by the serine protease inhibitors benzamidine and soybean trypsin inhibitor when they were held in a goldfish Ringer solution. Eggs in which chorion expansion was inhibited retained their fertility for 30 min when held in this solution. In contrast, ovulated eggs lost their fertility in freshwater even in the presence of a protease inhibitor. The results suggest that chorion expansion and loss of fertility in water-activated goldfish eggs may involve proteolysis which was blocked by benzamidine and soybean trypsin inhibitor. Moreover, the blockage of chorion expansion may be pivotal to the preservation of fertility in eggs held in Ringer's solution with soybean trypsin inhibitor. The development of this solution provides a means to temporarily hold ovulated goldfish eggs in a viable state outside the female and will permit further studies on fertilization in this species.
Effects of Experimental Manipulations of Light and Phosphorus Supply on Competition among Picoplankton and Nanoplankton in an Oligotrophic Lake
Authors: Wehr John D.
Published: October 2008

Phytoplankton communities of clear, oligotrophic lakes are often dominated by small cells, especially the cyanobacterium Synechococcus. Experiments in Rye Lake (New York) directly examined effects of light and phosphorus limitation on the growth of small phytoplankters. Factorial experiments compared growth of phytoplankton collected from 1 and 15 m; microcosms were incubated at both depths and treated with a single P pulse (± 2 μM KH2PO4). During stratification, picoplankton (0.2–2 μm; ≈Synechococcus spp.) predominated, but surface nanoplankton (especially Cyclotella stelligera and Chlamydomonas gloeocapsa) were stimulated to equivalent biomass levels following the P pulse. No significant P effect was observed at 15 m. Picoplankton biomass was similar in surface and deepwater communities and independent of P treatment. Depletion of [Formula: see text] was greatest in surface-incubated controls. After turnover, phytoplankton biomass in both size fractions was unaffected by P but decreased when transplanted from 1 to 15 m (−30 to −70%) and increased in transplants from 15 to 1 m (+ 55 to + 140%). Results suggest that (1) Synechococcus is a superior competitor only under low-light, low-P conditions, (2) multiple resources interact to affect community size structure, and (3) resultant size shifts significantly alter ecosystem nutrient dynamics.
Element Concentrations in Chironomids and Their Abundance in the Littoral Zone of Acidified Lakes in Northwestern Ontario
Authors: St. Louiss Vincent L.
Published: October 2008

I studied species diversity of the chironomid community, abundance of emerging adults, and accumulation of metals and elements in chironomids in the shallow littoral zone of experimentally acidified and unmanipulated reference lakes at the Experimental Lakes Area in northwestern Ontario. Orthocladiinae were significantly more abundant in acid lakes than in reference lakes, while the Chironominae were less numerous. The lower abundance of Chironominae resulted from fewer chironomids in the Tribe Tanytarsini. Chironomini were more common in acid lakes than in the reference lakes. Biomass of emerging chironomids either increased significantly following acidification or was not different from that of reference lakes. Concentrations of Al, Ca, Mn, and Zn were on average higher in chironomids from a number of the acid lakes than in chironomids from reference lakes. Calcium concentrations in chironomids from the most acid lake were significantly lower, however, suggesting that at low pH levels, Ca may be difficult to sequester. Increased accumulation of certain metals in chironomids, coupled with increased biomass of emerging chironomids as well as low levels of Ca, makes chironomids a potentially abundant but poor-quality food source for organisms that rely on them as prey.
Sites of Methyl Mercury Production in Remote Canadian Shield
Authors: Ramlal P. S. , Kelly C. A. , Rudd J. W. M. , Furutani A.
Published: October 2008

Methylation and demethylation of mercury were studied in sediments and surface waters of several remote lakes on the Canadian Shield. Radiochemical assays of mercury methylating activity, which peaked during summer, were 20–40 times faster in epilimnetic than in hypolimnetic sediments. Demethylation rates were usually highest during winter and in hypolimnetic sediments. Epilimnetic sediments were capable of producing methyl mercury 20–40 times faster than hypolimnetic sediments sampled at the same time, with methylating activity peaking during the warm summer months. Because of the opposite pattern of methylating and demethylating activity and because epilimnetic sediments often constitute most of the surface area of these lakes, most of the net methylation (M/D) occurred in the epilimnion of the lakes during summer. Mercury methylation rates were not related to average sediment mercury concentrations, or directly to rates of microbial activity (decomposition) in sediments. It appeared that increasing temperature was an important controlling factor that stimulated methylation but retarded demethylation. Specific methylation rates, M/D, and the measured concentration of methyl mercury in the surface waters of the lakes all peaked during midsummer, suggesting that the radiochemical assays used reflected changes in the relative activities of natural methylating and demethylating microorganisms.
Mercury Concentrations in Fish Related to Size of Remote Canadian Shield Lakes
Authors: Bodaly R. A. , Rudd J. W. M. , Fudge R. J. P. , Kelly C. A.
Published: October 2008

Mercury concentrations in planktivorous, omnivorous, and piscivorous fishes were inversely related to lake size in six lakes in northwestern Ontario. The lakes were remote from direct anthropogenic influences and ranged in surface area from 89 to 35 000 ha. Fish mercury concentrations were not related to ratios of drainage basin area to lake size, to ratios of epilimnetic area to lake size, to lake alkalinity, or to the concentration of mercury in lake sediments. Rates of mercury methylation (M) were positively dependent on water temperature whereas rates of methyl mercury demethylation (D) were inversely related to temperature. Thus, M/D was strongly temperature dependent. Mercury concentrations in four fish species were significantly positively correlated with mean epilimnetic water temperatures (r2's ranged from 0.66 to 0.88). This suggested that higher water temperatures in smaller lakes during the open-water season influenced M/D ratios and were the cause of higher fish mercury levels. No lake size related variation was observed in the mercury concentrations in benthivorous fishes. Our hypothesis that epilimnetic temperature affects mercury concentrations in fish deserves further attention, given the possible effects of climate warming on mercury contamination of fishery resources.
Proton Transport and Chloride Cells in the Gill of Rainbow Trout (Oncorhynchus mykiss)
Authors: Justesen Nils Petter Berg , Dall-Larsen Torbjørn , Klungsøyr Leiv
Published: October 2008

Particulate preparations from freshwater rainbow trout (Oncorhynchus mykiss) gill homogenates contain an active magnesium ion activated ATPase that transports protons into the vesicles. Oligomycin at a concentration of 20 μg∙mL−1had little effect on the proton transport, which was completely inhibited by N-ethylmaleimide. This inhibition was partly counteracted by dithiothreitol. Proton transport in freshwater trout gill submitochondrial particles was completely inhibited by oligomycin. When freshwater trout were kept for 40 min in water equilibrated with air containing 5% carbon dioxide, their gill lamellar epithelium contained many cells densely covered with erect microvilli. After changing to water bubbled with room air, the cells rapidly lost their microvilli. Control fish that were killed immediately after removal from the storage tank also had microvilli, but less erect and fewer in number. Labelled latex microspheres and dextran were used as markers for external medium uptake into gill epithelial cells. The fish were pretreated by bubbling the water by air containing 5% carbon dioxide, and the uptake took place when the water was bubbled with room air.
Relationship between Growth and Total Nucleic Acids in Juvenile Pink Salmon, Oncorhynchus gorbuscha, Fed Crude Oil Contaminated Food
Authors: Wang Shiao Y. , Lum Judith L. , Carls Mark G. , Rice Stanley D.
Published: October 2008

Total nucleic acids of juvenile pink salmon, Oncorhynchus gorbuscha, fed crude oil contaminated food were analyzed to determine if nucleic acid measurements can be used to evaluate growth of fish collected at oil spill sites. In general, the nucleic acid concentration (micrograms per milligram dry weight) of salmon fry fed food contaminated with either 0.37 or 2.78 mg crude oil/g food was not significantly affected. However, RNA concentration of fry fed food contaminated with 34.83 mg/g was reduced whereas DNA concentration increased. Results over 8 wk indicate decreased protein synthesis and cell content but maintenance of cell integrity in these fish. Growth was inversely related to the level of crude oil contamination in the food. The significant correlations between measured growth and RNA/DNA ratios and RNA contents (micrograms RNA per millimetre fork length) suggest that nucleic acid measurements can be used to compare growth of fish collected from the field.
Sediment Resuspension, Redeposition, and Focusing in a Small Dimictic Reservoir
Authors: James William F. , Barko John W.
Published: October 2008

Rates of seston (dry mass) sedimentation, estimated from sediment traps (ST rates) and sediment cores (SC rates), were determined at four water depths to examine seasonal and annual sedimentation patterns in Eau Galle Reservoir, Wisconsin (USA). Annual ST rates overestimated annual SC rates at water depths [Formula: see text], suggesting that sediment resuspension and redeposition in relatively shallow regions of the reservoir caused the overestimate. In contrast, annual ST and SC rates were similar at depths > 4 m, suggesting minimal sediment resuspension and redeposition in deeper regions of the reservoir. Using variations in daily ST rates estimated during the autumn overturn of 1987, we developed a conceptual framework for estimating sediment resuspension, redeposition, and focusing. Resuspension of shallow sediments during this particular period accounted for over 50% of the annual ST rate at depths [Formula: see text]. At the same time, focusing of resuspended shallow sediments to deeper regions accounted for about 20% of the annual ST rate at depths > 4 m. Our results indicate that during autumn overturn in this reservoir, peaks in sedimentation in the deep, profundal region, estimated from sediment traps, may reflect sediment focused from shallow regions rather than sediment resuspended from the profundal region.
On the Statistical Distribution of Salmon in the Sea: Application of the Negative Binomial Distribution, and the Influence of Sampling Effort
Authors: Welch David W. , Ishida Yukimasa
Published: October 2008

We examined the sampling statistics of Pacific salmon (Oncorhynchus spp.) caught in a series of experimental gillnet sets on the high seas and demonstrate how the reliability of the catch statistics varies with the amount of sampling effort. Our analysis indicates that the replicate catches, which were made under essentially identical conditions, are adequately described by the negative binomial distribution. We also extend the utility of this distribution for describing catch statistics by showing that (1) the shape parameter of the distribution can be directly interpreted as the number of degrees of freedom (df) associated with each observation of catch and (2) the df are related to the amount of sampling effort used and the size of the biological aggregation being encountered by the gear. For salmon caught on the high seas, approximately 1 df is obtained per 15 m of gill net used. Identification of the statistical model describing the uncertainty in high-seas gillnet catches should help in the design of better high seas surveys and in the analysis of historical data bases. As an example, we show how the statistical certainty associated with estimates of salmon density changes with the amount of sampling effort applied.
Effects of Water Velocity, Group Size, and Prey Availability on the Stream-Drift Capture Efficiency of Blacknose Dace, Rhinicthys atratulus
Authors: Tyler Jeffrey A.
Published: October 2008

In laboratory flow-tank experiments, I determined the effects of water velocity, group size, and prey arrival rate on the proportion of drifting prey a group of blacknose dace, Rhinicthys atratulus, captured. Water velocity, group size, and the interaction between the two accounted for significant proportions of the variance found in the stream-drift capture efficiency of the fish. Neither prey arrival rate nor any of the interactions which included prey arrival rate explained a significant proportion of the variance in the capture data. I present a regression relating water velocity and group size to the proportion of drift items fish capture that should be valuable for future studies offish habitat selection. Further analysis of the regression found an optimal water velocity for drift-feeding blacknose dace at between 24 and 27 cm∙s−1. Because of the significant interaction between water velocity and group size, the advantage of foraging in sites with optimal water velocity decreased as the number of intraspecific competitors increased.
Microhabitat Segregation of the Threatened Spotted Darter (Etheostoma maculatum) and Closely Related Orangefin Darter (E. bellum)
Authors: Kessler Richard K. , Thorp James H.
Published: October 2008

We examined differences in microhabitat use in sympatric populations of the closely related spotted darter (Etheostoma maculatum) and orangefin darter (E. bellum) (subgenus Nothonotus). Sample plots and underwater observations were employed to assess patterns of microhabitat use by both species. Quantitative sampling using a prepositioned electrofishing sampler demonstrated that species segregated by microhabitats. Etheostoma maculatum occupied areas of greater depth and larger, more diverse substrate sizes than E. bellum in July and October of 1991. Underwater observations also revealed species-specific differences in substrate use. Etheostoma maculatum was observed mostly under rocks whereas E. bellum was more general in substrate use. The narrow range of microhabitat use by E. maculatum may contribute to its status as a threatened species in Kentucky. During July 1991, an unusually high discharge month that year, males of both species occupied microhabitats of significantly higher velocities and larger substrate sizes than females. Our data suggest that opportunities for coexistence between these closely related darters are enhanced by microhabitat partitioning which is linked to behavioral and morphological differences.
Chehalis River Disease: A Unique Gill Disease of Salmonids
Authors: Newbound G. C. , Speare D. J. , Hammell K. L. , Kent M. L. , Ostland V. E. , Traxler G. S.
Published: October 2008

Epidemic mortalities of chinook salmon alevins (Oncorhynchus tshawytscha) have occurred annually at a freshwater hatchery at the Chehalis River, British Columbia, Canada, since 1982. Previous work has identified branchial epithelial hyperplasia as the predominant pathological change. Our initial work lead us to test the hypothesis that Chehalis River disease (CRD) was actually a novel form of bacterial gill disease (BGD). Histological and ultrastructural observations indicated that CRD-affected gills harboured a bacterial biofilm apparently complexed with particulate iron prior to and during clinical CRD. In one instance, extracellular viruslike particles were observed. Large numbers of a mixed bacterial population were recovered from diseased gills. Flavobacterium sp. and Pseudomonas fluorescens were considered the predominant isolates from the 1990–91 outbreak. However, indirect immunofluorescence of gills with anti-Flavobacterium branchophila serum failed to detect antigenically similar bacteria on the gills of CRD-affected fish. Chemotherapeutic treatment of both naturally and experimentally infected fish was successful, thereby confirming the infectious nature of the disease. We conclude that CRD is a form of BGD, but the significance of the branchial viruslike particles and the presence of particulate iron has not yet been established.
Experimental Acidification of Little Rock Lake, Wisconsin: Chemical and Biological Changes over the pH Range 6.1 to 4.7
Authors: Brezonik P. L. , Eaton J. G. , Frost T. M. , Garrison P. J. , Kratz T. K. , Mach C. E. , McCormick J. H. , Perry J. A. , Rose W. A. , Sampson C. J. , Shelley B. C. L. , Swenson W. A. , Webster K. E.
Published: October 2008

The two basins of this seepage lake were separated by a vinyl curtain in August 1984 after a year of background studies, and acidification of one basin with H2SO4began at ice-out in 1985. Chemical and biological responses measured during successive 2-yr periods at pH ~5.6, 5.1, and 4.7 verified some but not all impacts predicted at the outset. Changes in major, minor, and trace ions generally agreed with predictions. Internal alkalinity generation (IAG) increased at lower pH, and sulfate reduction eliminated ~50% of added H2SO4. Sediment cation exchange was important in IAG and acidified surface sediments, possibly diminishing the lake's ability to counteract further H+inputs. Mass loss of oak leaves was reduced at pH 5.1 (birch leaves at pH 4.7). Population parameters were more sensitive than community measures for plankton. Species composition changed at each pH, especially at pH 4.7. Many changes in zoopiankton and benthos were indirect responses to an algal mat that developed at lower pH or to food web interactions; these were not predicted accurately. Sensitivity of major fishes to lower pH was Ambloplites rupestris > Micropterus salmoides > Pomoxis nigromaculatus > Perca flavescens. Fish production was reduced at pH's above those resulting in population decreases.
Gas exchange and growth of bald cypress seedlings from selected U.S. Gulf Coast populations: responses to elevated salinities
Authors: Pezeshki S.R. , Delaune R.D. , Choi H.S.
Published: October 2008

Bald cypress (Taxodiumdistichum (L.) Rich.) seedlings from two sources in Louisiana were tested for a possible difference in salt tolerance. The study was conducted in rhizotrons under controlled environmental-conditions. Seedlings were subjected to a control (no flood or salt) and three combinations of flooding salinity: flooding only, flooding plus 68 mol•m−3 salt (4 ppt), and flooding plus 136 mol•m−3 salt (8 ppt). Both populations survived the flooding and salinity treatments for the duration of the study. However, gas exchange and net biomass production were reduced in both populations as salinity of floodwater increased from 0 to 136 mol•m−3. The gas exchange and biomass data indicated that plants from the freshwater source had higher growth rates than the brackish plants. This superiority was also maintained under all the treatments except the highest salinity treatment. Significantly greater net photosynthetic capacity per unit area of leaf was found for the freshwater population than for the brackish population in 68 mol•m−3 salt. In addition, greater root porosity, height growth, and biomass production (shoot, root) were found for the freshwater population than for the brackish population under different treatments. The data indicate that there is a potential for population differentiation in bald cypress, as shown primarily by differences in growth traits. However, the data do not support the hypothesis that bald cypress plants from the brackish source have a capacity to survive and grow better in saltwater than plants from the freshwater source. In fact, combined flooding and salinity treatments resulted in significant reductions in net photosynthesis as compared with the control in both sources.
Measuring the efficacy of adjacency constraint structure in forest planning models
Authors: Murray Alan T. , Church Richard L.
Published: October 2008

This paper examines various structural representations of adjacency conditions in forest planning problems. It will be shown that alternative representations can rival traditional approaches, which is counter to much of the mathematical modeling and formulation literature. Analysis was conducted on a number of forest planning problems in order to draw some general conclusions on adjacency constraint representations. This is the first time that these structures have been compared in a comprehensive way. This paper provides insights into solution performance using different constraint structures and will help further the development of improved methodologies for analyzing environmental problems that must incorporate increased spatial detail.
Growth and solute adjustment of calli of Populus clones cultured on nutrient medium containing polyethylene glycol
Authors: Tschaplinski T.J. , Gebre G.M. , Dahl J.E. , Roberts G.T. , Tuskan G.A.
Published: October 2008

To determine whether in vitro assays can be used as a surrogate for whole plants in the assessment of drought tolerance, six clones in a pedigree consisting of black cottonwood (Populustrichocarpa Torr. & Gray, ♂) and eastern cottonwood (Populusdeltoides Bartr., ♀) and four hybrid progeny were regenerated in tissue culture and subjected to 0–20% polyethylene glycol (PEG) mol. wt. 8000 in the nutrient medium, providing osmotic potentials that ranged from –0.40 to –1.29 MPa. Drought tolerance was assessed by callus growth and solute accumulation under various stress conditions. Among the cultures grown in the light (16-h photoperiod), clones with the highest relative growth rate of callus dry weight after 18 d in the nutrient medium without PEG included hybrids 246 ♂, 242 ♀, and the eastern cottonwood ♀ parent; the same clones that tended to be the most drought tolerant in previous whole-plant studies. However, there were few clonal differences in relative growth rate across PEG concentrations or among light or dark environments, and any differences were not related to solute accumulation. Polyethylene glycol (20%) provided a severe osmotic stress that dehydrated callus cultures, thereby suppressing relative growth rate on a fresh-weight basis, but not on a dry-weight basis. Inorganic cations and free amino acids constituted the bulk of the solutes in calli, whereas concentrations of soluble carbohydrates were low. Therefore, results obtained from callus cultures growing under artificially induced drought regimes did not parallel those obtained from water stress studies on whole plants.
Nitrogen induced potassium deficiency in white spruce (Piceaglauca) and Engelmann spruce (Piceaengelmannii) seedlings
Authors: Driessche R. Van Den , Ponsford D.
Published: October 2008

White spruce (Piceaglauca (Moench) Voss) and Engelmann spruce (Piceaengelmannii Parry ex Engelm.) seedlings grown for 2 or more years in sandy loam nursery soils in British Columbia often show yellow and necrotic shoot-tip symptoms. Chemical analysis of a white spruce and a white × Engelmann hybrid spruce provenance showed that the symptoms were associated with low needle K concentrations. After nursery growth was complete, growth tests showed that seedlings with symptoms took longer to flush and had 43% less shoot extension than normal green seedlings. To see why K fertilizer alone did not always cure the symptoms, 1.5-year-old Engelmann spruce seedlings were transplanted and grown for a further 1.5 years in a 4 × 3 × 3 factorial experiment (K level × N source × N level). Nitrogen fertilization increased growth and symptom occurrence, with sources resulting in more symptoms in the order (NH4)2SO4 < NH4NO3 < Ca(NO3)2. Potassium fertilization decreased symptoms, although not completely, but had no effect on growth. Shoot-tip NH4+ was positively correlated with symptoms, while higher levels of soil and shoot-tip K, as well as soil and shoot-tip Mg, were associated with reduction in symptoms. It was concluded that heavy N fertilization created requirements for K, and probably Mg, above the tissue concentrations normally regarded as adequate, and that K fertilization did not always eliminate symptoms because of a Mg requirement.
An individual tree diameter increment model for white spruce in Alberta
Authors: Huang Shongming , Titus Stephen J.
Published: October 2008

Based on a data set from 164 permanent sample plots, an age-independent individual tree diameter increment model is presented for white spruce (Piceaglauca (Moench) Voss) grown in the boreal mixed-species stands in Alberta. The model is age independent in that it does not explicitly require tree or stand age as input variables. Periodic diameter increment is modelled as a function of tree diameter at breast height, total tree height, relative competitiveness of the tree in the stand, species composition, stand density, and site productivity. Because data from permanent sample plots are considered time series and cross sectional, diagnostic techniques were applied to identify the model's error structure. Appropriate fit based on the identified error structure was accomplished using weighted nonlinear least squares with a first-order autoregressive process. Results show that (1) all model parameters are significant at α = 0.05 level, and (2) the plot of studentized residuals against predicted diameter increment shows no consistent underestimate or overestimate for diameter increment. The model was also tested on an independent data set representing the population on which it is to be used. Results show that the average prediction biases are not significant at α = 0.05 level, indicating that the model appropriately describes the data and performs well when predictions are made.
Benzoic acid, salicylic acid, and the role of black galls on aspen in protection against decay
Authors: Pausler M. Gabrielle , Ayer William A. , Hiratsuka Yasuyuki
Published: October 2008

Trembling aspen (Populustremuloides Michx.) bearing certain types of black galls have a lower incidence of Phellinustremulae (Bond.) Bond. & Boriss. heartwood rot than do nongall-bearing trees. Extraction of finely ground black gall tissue with ethyl acetate and separation of the acidic components of the extract led to the isolation of benzoic acid, trans-cinnamic acid, p-hydroxybenzoic acid, p-hydroxycinnamic acid, naringenin, 7′-methyl-3-hydroxynaringen, aromadendrin, and taxifolin. Bioassays revealed that among these compounds, only benzoic acid showed significant activity against P. tremulae. An analytical procedure was developed to measure the concentration of benzoic acid in various types of aspen tissue. Tissue from the black galls showed a high concentration of benzoic acid, and tissue from gall-bearing trees contained significantly more benzoic acid than healthy nongalled trees. However, the amount of benzoic acid present in the gall-bearing trees may not be sufficient to prevent Phellinus decay. It is suggested that perhaps the benzoic acid serves as a precursor of salicylic acid, a signal molecule in systemic acquired resistance of plants.
Chronoséquence après feu de la diversité de mammifères et d'oiseaux au nord de la forêt boréale québécoise
Authors: Crête Michel , Crête Michel , Drolet Bruno , Huot Jean , Fortin Marie-Josée , Fortin Marie-Josée , Doucet G.J.
Published: October 2008

Diversity of passerine birds and mammals was estimated in well-drained areas located at proximity of the hydroelectric reservoir La Grande-3, where natural fire regime still prevails in the absence of forest exploitation. Forest stands were divided up into four post-fire stages: (i) recent burns (4 years old), (ii) shrubs (25 years old), (iii) young forests (50 years old), and (iv) mature forests (≥71 years old). Richness and species diversity were highest in middle stages, in shrubs and young forests. The degree of opening seems to have affected more the composition of bird communities than stand age. Some bird species, typical of shrub stands, in particular white-crowned sparrow (Zonotrichialeucophrys Forster), Lincoln's sparrow (Melospizalincolnii Audubon), and alder flycatcher (Empidonaxalnorum Brewster), appeared after the falling of dead trees, ≈15 years after fire, and disappeared progressively as forests matured. Deer mice (Peromyscusmaniculatus Wagner), moose (Alcesalces L.), and black bears (Ursusamericanus Pallas) were more common at the beginning of succession, whereas northern red-backed voles (Clethrionomysgapperi Vigors) and caribou (Rangifertarandus L.) were typical of late stages. Mammal presence was mostly associated to their feeding requirements. Fire creates a mosaic of forest stands through periodic killing of trees in the north of the boreal forest, which contributes to maintain regional wildlife diversity; its suppression would reduce biodiversity.
Modélisation du mouvement du prix du bois à pâte issu de la forêt privée québécoise entre 1943 et 1990
Authors: Nadeau Solange , Bouthillier Luc
Published: October 2008

In Quebec the rightness of prices paid to small woodlot owners for their pulpwood has been a subject of controversy since the late 1940's. Our research examined the impact of some economical, political, and sociological factors applied to the price system pertaining to the nonindustrial private forests between 1943 and 1990. To do so, we have built a regression model explaining 81% of price movement during that period. The study shows how interfering laws have affected the market. It also demonstrates the information effect resulting in price stability. Marketing boards appear to enhance woodlot owners' behavior as rational economic actors. Finally our study emphasizes a complementarity between crown lands and privately owned forests preventing a more efficient production from woodlot owners.
Mortality of balsam fir and black spruce advance growth 3 years after clear-cutting
Authors: Ruel Jean-Claude , Doucet René , Boily Jocelyn
Published: October 2008

The effects of balsam fir (Abiesbalsamea (L.) Mill.) and black spruce (Piceamariana (Mill.) B.S.P.) seedling attributes on survival were measured on four cutovers regenerated to black spruce and three regenerated to balsam fir. In each of these, about 240 stems were permanently identified shortly after logging and their main characteristics were noted. Survival was assessed after 1 and 3 years. First-year mortality reached 24% for balsam fir and and 21% for black spruce. It varied with height and seedling quality. Mortality during the second and third year after harvesting was less important and was more evenly distributed between the different height classes. When all height classes were combined, the logistic regression calculated for total balsam fir mortality was able to correctly classify the observations in 74% of the cases by using three variables: prerelease height growth, lean angle, and a wound index. For black spruce, seven variables were needed to correctly classify 78% of the observations. These were: height, prerelease height growth, live crown ratio, lean angle, distance to the straightening point, and two wound indices. Separate logistic regressions were calculated for stems smaller or taller than 30 cm. These regressions performed considerably better for the taller height class for both species. For balsam fir, lean angle and one or another wound index still remained in relation with survival. For black spruce, prerelease height growth and lean angle remained in relation with survival. Distance to the straightening point was only retained for stems below 30 cm while live crown ratio and the two wound indices were retained for stems over 30 cm. These results suggest that an evaluation of seedling quality using measures of previous suppression and logging damage should be introduced in regeneration surveys to better predict the evolution of a cutover after harvesting.
SIMULTANEOUS MEASUREMENT OF TWO DIFFERENT TARGETS BY MEANS OF VACUUM AND IN-AIR PIXE
Authors: SERA K. , SASAKI T. , ITOH J. , SAITOH Y. , FUTATSUGAWA S.
Published: October 2008

A simultaneous measuring system of two different targets by in-vacuum and in-air PIXE has been developed in order to improve efficiency of analyses in the limited machine time. The proton beam passes through a thin target in vacuum and it allows us to perform in-vacuum PIXE, and the beam is further transported to the in-air PIXE system for analyzing another target. The beam intensity for in-air PIXE while performing in-vacuum PIXE is 1.5 nA, which is almost sufficient. The effect of slight changes in the beam transport parameters on the background X-rays for both in-vacuum and in-air PIXE has been found to be negligible. As a result, it is confirmed that accuracy and sensitivity of analysis for many kinds of sample, such as various samples in earth, environmental sciences and in bio-medicine, are almost unchanged for the both systems, and a four-detector-simultaneous measuring system has been completed. It is expected that the system will work miracle for solving the problem of deficient machine time in our laboratory.
APPLICATION OF ION EXCHANGE PAPER TO PRECONCENTRATION OF CHROMIUM (III) AND CHROMIUM (VI) IN WATER FOR PIXE ANALYSIS
Authors: THOMYASIRIGUL SUREERAT , FUKUDA HITOSHI , HASEGAWA JUN , OGURI YOSHIYUKI , RATANATAMSKUL CHAVALIT
Published: October 2008

The most important species of chromium (VI) formed in water are anions such as CrO 42-, whereas chromium (III) is mainly present in the form of cationic species such as Cr ( OH )2+. Pure water and tap water samples were artificially contaminated with mixture of chromium (VI) and chromium (III) standard solutions. Sequential filtration through commercially available Whatman P81 cellulose phosphate paper and Whatman DE81 DEAE cellulose paper was employed for separation and preconcentration of chromium (III) and chromium (VI) in these water samples, respectively. The PIXE measurements of these filter paper samples were performed using 2-MeV proton beams delivered by a tandem pelletron accelerator at Research Laboratory for Nuclear Reactors, Tokyo Tech. The beam current and the measuring time for each sample were 1 nA and 10 minutes, respectively. Instrumental detection limits were 60 ng for chromium (VI) and 120 ng for chromium (III). Detectable range for chromium (VI) and chromium (III) in water were ≧ 10 ppb and ≧ 50 ppb, respectively. For chromium (VI), the detectable range was considerably lower than the maximum allowed concentration of 50 ppb for chromium (VI) in both the drinking water standards and the environmental quality standards in many countries.
STANDARD-FREE METHOD FOR HAIR SAMPLES IN IN-AIR PIXE
Authors: SERA K. , TERASAKI K. , ITOH J. , SAITOH Y. , SAKURAI S.
Published: October 2008

Standard-free method for untreated hair samples in in-air PIXE has been developed. It is confirmed that the method gives us good sensitivity and accuracy within several minutes' measurement if more than twenty hairs are attached onto the target. Even in the case where the number of hairs is less than eight, which is regular for usual in-vacuum PIXE, 10-15 minutes measurement is found to be sufficient to achieve almost satisfactory sensitivity and accuracy for elements from Cl to Pb . As the present method allows us to carry out analyses without labor in target preparation, it is expected to be quite helpful in the studies on human exposure to toxic elements. Its availability will more and more increase when the method is combined with the method of simultaneous measurement of in-vacuum and in-air PIXE we have just developed.