bluuebunny/crossref_metadata_2025 huggingface dataset:
Perceptions of a mental health questionnaire: the ethics of using population-based controls
Authors: Surkan P J , Steineck G , Kreicbergs U
Published: June 2008

Mental health surveys are used extensively in epidemiological research worldwide. The ethical questions that arise regarding their risk of causing psychological distress or other potential harm have not been studied in the general population. We have investigated how study participants serving as controls in a population-based study perceived an anonymous postal questionnaire focusing on mental health and wellbeing. Parents were contacted from the Swedish Census Bureau as part of a larger follow-up study on palliative care conducted in 2001. Eligible parents had a child of the same gender, year of birth and were from the same counties in Sweden as parents who had lost a child to cancer.

Five percent reported being negatively affected. The principle negative effect on participants was that self-reflection reminded them of their difficulties. Of the 418 respondents, 52% reported that they were positively affected by study participation and 95% perceived the inquiry as valuable. These findings support the use of population-based controls in future research.
A classification and analysis of crown form in green ash (Fraxinus pennsylvanica)
Authors: Remphrey W. R. , Davidson C. G. , Blouw M. J.
Published: July 2008

Forty-five boulevard green ash (Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern.), both male and female trees, were selected and numerous morphometric measurements were obtained. Multivariate and univariate techniques applied to the data suggested three crown shape classes based on the pattern of crown diameter changes. The crown shape classes were identified as broad and rounded (group C) to tall and conical (group A), with an intermediate category (group B). Although tree age was not significantly different, group C trees tended to be larger with larger crown areas and basal main-stem diameters compared with groups A and B, which were not different. A visual rating analysis of the woody frame revealed that group A trees tended to have an excurrent form, whereas group C trees were predominately decurrent. When comparing sexes, it was found that male trees were larger, with larger crown areas than females, and they had a greater ratio of crown area to basal stem diameter. The crowns of male trees were generally branchier, with more foliage per unit crown volume than females. It appears that, in terms of growth and form, male trees are probably better suited for use as boulevard trees than female trees. Differences among groups and between sexes are discussed in relation to factors like apical control and reproductive sinks.
Étude de l'archégone de Sphagnum palustre. I. Le gamète femelle et la fécondation
Authors: Fabre M. C.
Published: July 2008

Female gametogenesis and fertilization of Sphagnum palustre were compared with data on different species of Mnium (Bryatae) and on Fossombronia angulosa (Marchantiatae). The general organization of the archegonium is identical with that observed in other bryophytes. The progamete appears as an odd-shaped 23 μm long cell. Numerous organelles are responsible for the relatively high electronic density. The progamete divides into two cells, the larger being the egg. Different stages of the maturation process of the female gamete are described. The one major difference found is in the origin of the mucopolysaccharides surrounding the female gamete in the archegonium. A stage corresponding to the contact of the two nuclei just prior to fusion was observed in the fertilization process.
Structure and reproduction of Sphaeroplea fragilis sp.nov., a new member of the Sphaeropleaceae (Chlorophyceae) from California
Authors: Buchheim Mark A. , Hoffman Larry R.
Published: July 2008

A new species of Sphaeroplea is described from material collected near Lemoncove, California. Sphaeroplea fragilis sp.nov. possesses a combination of features that clearly support its status as a distinct member of the Sphaeropleaceae. These features include the production of vegetative filaments that fragment easily, the presence of numerous and relatively long cytoplasmic plugs (4 – 400 μm), precocious sexual development, the production of short antheridia (21 – 141 μm), a highly variable ornamentation of the oospore wall, and the occasional production of cirri, which are curled appendages on the oospore wall.
Character inheritance and polymorphism in a wild oat (Avena fatua) population
Authors: Darmency H. , Aujas C.
Published: July 2008

A population of wild oats (Avena fatua L.) in a cultivated field was sampled once or twice a year between 1979 and 1983. Plants differing in seed morphology, seed avenin pattern, leaf esterase pattern, and vernalization requirements were crossed to study the inheritance of these traits (13 loci). The polymorphism of the population for each of these characters and 11 others was investigated as well as the frequency of each type of plant (phenotype). Forty-seven phenotypes were observed over the 5 years, but only five were consistently present in all samples. They represented 78% on average of the population. The observed increase of a phenotype correlatively to the decrease of another one is discussed as a function of cultural practices.
Scanning electron microscopy examination of soybean testa development
Authors: Baker Daniel M. , Minor Harry C. , Cumbie Billy G.
Published: July 2008

Seeds of soybean (Glycine max (L.) Merr.) were harvested from greenhouse-grown plants and fractures of the seed coat were examined with a scanning electron microscope. The seed coat was well differentiated from the outer integument when the seed had reached approximately 30% maximum seed size. At this time, the osteosclereids began to separate, becoming fully detached along their radial walls by 50% maximum seed size. Macrosclereid secondary wall development occurred during growth of the seed from 50 to 100% maximum seed size. Near R6 (100% maximum seed size) the endothelium began differentiation from the integumentary tapetum (inner integument) and was fully differentiated by physiological maturity (R7). From R7 to harvest maturity (R8) the seed lost moisture content and decreased in size. The parenchyma of the seed coat collapsed in response to this dehydration.
An Analysis of the Ability to Detect Reductions in Year-class Strength of the Hudson River White Perch (Morone americana) Population
Authors: Winkle W. Van , Vaughan D. S. , Barnthouse L. W. , Kirk B. L.
Published: June 2008

Impingement rates for young-of-the-year white perch (Morone americana) in the Hudson River were analyzed to address two questions: (1) assuming a specified number of years of additional data, what is the minimum fractional reduction in mean year-class strength that could be detected, and (2) assuming a specified fractional reduction in mean year-class strength, how many additional years of impingement data would be required to detect the reduction. Our results indicate that the variability in the baseline data is so great that 10 more years of data are not adequate for detecting even substantial (>50%) reductions in mean year-class strength and that more than 50 years of data would be required to detect an actual 50% reduction in mean year-class strength, given a Type II error of 50%. Our methodology offers a generic tool for establishing bounds on reductions in fish stocks and for estimating the number of additional years of data required to detect such reductions.Key words: fractional reduction, impingement, power plant, statistical power, Type I and Type II errors, white perch, year-class strength
Complementarity in the Use of Food and Thermal Habitat by Lake Michigan Fishes
Authors: Crowder Larry B. , Magnuson John J. , Brandt Stephen B.
Published: June 2008

The potential for ecological segregation of Lake Michigan fishes was examined by comparing diets and thermal habitat use of common species. Samples were collected by bottom trawling (N = 68) off Grand Haven, Michigan, September 7–13, 1977. Five common species exhibited complementarity in the use of food and thermal habitat resources. During the day, adult alewife (Alosa pseudoharengus), and rainbow smelt (Osmerus mordax) had similar diets but occupied somewhat different thermal habitats. Young-of-the-year (YOY) alewives segregated from adult alewife and rainbow smelt on both habitat and food. Spottail shiner (Notropis hudsonius), YOY alewives, and yellow perch (Perca flavescens) used similar thermal habitats but fed on different prey. Trout-perch (Percopsis osmiscomaycus) tended to segregate from the others based on both food and thermal habitat but may experience diffuse competition. Adults of the three native species consume entirely different prey than exotic alewife and rainbow smelt. The native species which declined during the invasion of alewife and rainbow smelt were those with apparently similar habitat and food requirements to the exotics. These data suggest that competition is important in maintaining the structure of the Lake Michigan fish community.Key words: competition, fishes, food, habitat, Lake Michigan, predation, temperature
A General Approach to the Culture of Planktonic Rotifers
Authors: Stemberger Richard S.
Published: June 2008

A general method for establishing cultures of planktonic rotifers from natural waters is described. Algal isolates are tested for their suitability as food for rotifers collected from the same source and season. Rotifer clones displaying the highest reproductive rates under the given culture conditions are selected for the final culture system. This procedure yielded indefinite cultures for the eulimnetic species, Asplanchna priodonta, A. herricki, Polyarthra major, and Synchaeta pectinata, and appears to have a good probability of success when the diet of a species is unknown. Algal isolates from the same source as the rotifers produced better results than algae obtained from commercial sources. Cryptomonad species produced the most consistent positive responses in growth and reproduction of rotifers tested.Key words: rotifers, zooplankton culture, Asplanchna, Polyarthra, Synchaeta, Cryptomonas
Estimated Preseason Abundance in the California Dungeness Crab (Cancer magister) Fisheries
Authors: Methot Jr. Richard D. , Botsford Louis W.
Published: June 2008

Annual preseason abundance for the central and northern California Dungeness crab (Cancer magister) fisheries is estimated from the decline in catch per unit of effort (CPUE) within each fishing season. The results support the common assumption that a large fraction of the available, legal size, male crabs are harvested each year; however, we noted regular changes in this fraction and also that it is rarely as high as previously assumed. In central California, annual exploitation rate was 92% during 1951–56 and declined to 72% following the collapse of the fishery. In northern California the annual exploitation rate varies with the 10-yr cycle of catch: 69% during the last few high catch years of each cycle, 84% in the first low catch year, and 54% during remaining low catch years and the first high catch year. The second high catch years are exceptions to a high exploitation rate. CPUE was saturated (i.e. did not decline) throughout the 1957 and 1977 fishing seasons. The large size of male crabs in the third and fourth high catch years also indicates high escapement in the second high catch years. Individual year-classes apparently may dominate the fishery for several years. This indicates that the time series of population abundance and recruitment is not as smoothly cyclic as the catch record.Key words: dungeness crab, Cancer magister, abundance, recruitment, catch per unit of effort
Seasonal Variation in the Chemical Composition and Condition Indices of Pacific Oyster, Crassostrea gigas, Grown in Trays or on the Sea Bed
Authors: Whyte J. N. C. , Englar J. R.
Published: June 2008

Chemical composition and condition indices of tray and bottom-cultured Pacific oyster, Crassostrea gigas, were measured and compared over a 13-mo period. Tray oysters were less dense than bottom oysters as a result of increased porosity of shells. Dry meat condition indices were slightly higher in oysters grown in trays. Chloride and iodide levels peaked in early spring. Minor seasonal deviations occurred from the mean 61.0% polymeric matter, 31.5% hydrophilic matter of low molecular weight, and 7.5% lipid matter in both groups of oysters. Nonprotein to protein nitrogen ratio in tray and bottom oysters averaged 0.37 and 0.35, respectively, throughout the season. A procedure was developed to assess glycogen in situ in polymeric material fractionated from meat. Glycogen averaged 79.5 and 79.0% of the total glucose in tray and bottom oysters, respectively; the remainder consisted of the homologous series of α(1 → 4)-linked D-glucose oligomers. Degree of polymerization of oligosaccharides in tray and bottom oysters averaged 2.93 and 2.91, respectively. Dry meat condition indices correlated predominantly with protein condition indices, only secondarily with glycogen condition indices and insignificantly with the remaining constituent condition indices of tray and bottom oysters.Key words: Crassostrea gigas, tray and bottom cultures, chemical composition, nitrogen, carbohydrates, halides, density, condition indices, seasonal variations
Horizontal Exchange on Central Georges Bank
Authors: Loder John W. , Wright Daniel G. , Garrett Christopher , Juszko Barbara-Ann
Published: June 2008

An axisymmetric model of the evolution of temperature over central Georges Bank in spring, summer, and early fall is used to estimate bounds on the horizontal dispersion coefficient, KH, consistent with the observed development of a "hot spot" in this region. We find that KH is in the range of 150–380 m2∙s−1, in agreement with estimates based on drogue dispersion (EG&G 1979). The effect of such a dispersion rate on passive scalars is considered for a variety of initial distributions. Although, in the absence of air–sea transfer, any initial salinity difference across the central portion of the Bank would be essentially eliminated in a few weeks, local precipitation appears to be sufficient to maintain the observed distribution. Our results indicate that maintenance of primary production at 2 g C∙m−2∙d−1 over the central portion of the Bank requires that greater than 50% of the nitrogen demand be supplied by local regeneration, assuming the Redfield ratio to be appropriate. Because exchange with off-the-Bank waters is slowest for the very center of the Bank, the supply of new nitrogen to this area should be particularly low. On the other hand, fish larvae in this area may benefit from a relatively long residence time.Key words: horizontal exchange, Georges Bank, heat budget, nitrogen budget, residence time
Structuring of a Predator Population Through Temperature-Mediated Effects on Prey Availability
Authors: Adams S. Marshall , McLean R. B. , Huffman M. M.
Published: June 2008

Temperature can control the structure of a predator population by regulating the abundance and size availability of prey. Relatively small differences in winter temperatures between years can have a major influence on largemouth bass (Micropterus salmoides) population structure because of the threshold relationship between temperature and the lower lethal limits of shad. The relationship between prey availability and predator growth and mortality was established through field measurements of consumed energy. Growth and consumption of largemouth bass in Watts Bar Reservoir, Tennessee, was lower in 1979 than in 1980 as a result of lower winter water temperature in 1979, which reduced the abundance and availability of adequate-sized prey. Depending on the severity of the winter, bass that do not attain 25 ± 5 cm by the end of their first growing season do not survive to annulus I formation because of the unavailability of appropriate-sized prey in the spring and the inability of small bass to store sufficient energy reserves. Selective mortality favoring survival of larger individuals in an age-class is operating in the Watts Bar largemouth bass population. This has significant implications for predator growth in ecosystems that experience large seasonal fluctuations in prey availability.Key words: predator population structure, prey availability, reservoir temperature, energy consumption, growth, largemouth bass, selective mortality, shad
Nutrient Distributions and Their Relationships to Water Masses in Baffin Bay
Authors: Coote A. R. , Jones E. P.
Published: June 2008

We report measurements of phosphate, nitrate, and silicate concentrations in Baffin Bay and relate them to water masses identified by salinity and temperature. Our results illustrate the remarkable homogeneity of the water structure throughout Baffin Bay and show that nutrient concentrations can be used to label water masses in the Baffin Bay deep layer with similar resolution to that provided by salinity and temperature.Key words: phosphates, nitrates, silicates, Baffin Bay, water masses, nutrient concentrations
Phytoplankton Productivity Changes in a Small, Double-Basin Lake in Response to Termination of Experimental Fertilization
Authors: Shearer J. A. , Fee E. J. , DeBruyn E. R. , DeClercq D. R.
Published: June 2008

One basin of a small, double-basin lake was fertilized with carbon, nitrogen, and phosphorus for eight years, and then fertilization was stopped. The other basin was fertilized simultaneously with equivalent amounts of carbon and nitrogen only. Phytoplankton primary production was monitored using an incubator–numerical model technique. Production increased dramatically in the basin receiving artificial additions of C, N, and P. The increase was particularly large in the epilimnion where Cyanophyte blooms occurred during each year of fertilization and production rates averaged 2 to 10 times higher than in nearby, unfertilized reference lakes. Phosphorus, not nitrogen or carbon, was the critical nutrient. The productivity of the other basin also increased, but to a lesser degree and no Cyanophyte blooms were observed in this basin. When all fertilization was terminated, production in both basins immediately decreased. No more surface blooms were observed in either basin. Within 3 yr, the production had dropped to levels typical of reference lakes.
Whole-Lake Metal Radiotracer Movement in Fertilized Lake Basins
Authors: Hesslein Raymond H.
Published: June 2008

Seven radiotracers: 75Se, 203Hg, 85Sr, 134Cs, 59Fe, 65Zn, and 60Co were added to the separated basins of Lake 226, Experimental Lakes Area, northwestern Ontario. The basins, L226N and L226S were part of an ongoing eutrophication experiment in which C, N, and P were being added to L226N and C and N to L226S. The radiotracers moved to the sediments by sorption to settling particles and by being directly absorbed. The loss rates ranged from 3–8%∙d−1. Areal distribution in the sediments was largely governed by the percent sorbed to particles. Both basins exhibited seasonal anoxic hypolimnia in which redissolution of 59Fe, 60Co, and 203Hg was great, of 75Se, 85Sr, and 65Zn only minimal, and of 134Cs negligible. The overall behavior of each of the isotopes was nearly identical in the two basins, partly due to interbasin mixing. A least squares fit of the affinity for particles and loss rates to a whole-lake model yielded a settling velocity of 0.18 m∙d−1 and a benthic boundary layer of 370 μm thickness.
Phytoplankton Primary Production and Light Attenuation Responses to the Experimental Acidification of a Small Canadian Shield Lake
Authors: Shearer J. A. , Fee E. J. , DeBruyn E. R. , DeClercq D. R.
Published: June 2008

Phytoplankton primary production and light attenuation were monitored over a 10-yr period in Lake 223, a small, softwater, shield, lake. After 2 yr with no treatment, the lake was treated for 8 yr with sulfuric acid to decrease the epilimnetic pH from about 6.7 to 5.0. Primary production, integrated over time and depth, varied considerably during the 2 pre-treatment years. However, it increased steadily during the first 6 yr of treatment, with a total increase of more than 250%. This production increase was coincident with a decrease in epilimnetic light attenuation. After the 6th year of treatment, the production of the lake decreased although the pH level was held relatively constant during this period. Nearby control lakes tended to show a similar, though less distinct, pattern during this 10-yr period. Thus, it is difficult to separate the effects of acidification from long-term natural variation. However, there was no apparent reduction in community phytoplankton production as a consequence of the acidification and the hypothesis that acidification causes oligotrophication was not supported.
Vertical Distribution of Zooplankton in an Experimentally Acidified Lake Containing a Metalimnetic Phytoplankton Peak
Authors: Kettle W. D. , Moffett M. F. , deNoyelles Jr. F.
Published: June 2008

A large biomass of phytoplankton occurred as a narrow band in the metalimnion of a small Canadian Shield lake which had been undergoing experimental acidification. This community represented the maximum concentration of algal biomass in the lake and was composed of small phytoplankton species. The diurnal distribution of crustacean zooplankton was determined in relation to this potential food source. Cyclopoid nauplii, Cyclops bicuspidatus thomasi, and Daphnia catawba remained diurnally associated with the peak while other species were uniformly distributed throughout the water column. Those species which remained diurnally associated with the peak were exposed to the greatest food concentration in the lake and were also exposed to lower acid conditions than those in the upper waters. A deep-dwelling phytoplankton community may offer a refuge for some zooplankton species in acid lakes by providing a large food supply under less acidic conditions. The importance of sampling acid lakes through the entire water column is supported by these observations.
Calcium and Trace Metal Composition of Crayfish (Orconectes virilis) in Relation to Experimental Lake Acidification
Authors: France Robert L.
Published: June 2008

Subjective estimates indicate that the carapaces of crayfish from experimentally acidified Lake 223 (pH 5.4–5.6) in the Experimental Lakes Area are becoming less rigid. Decreased carapace rigidity was inversely correlated with carapace dry weight and Ca++content. Orconectes virilis from L223 have 25–35% less Ca++in their exoskeletons (mean % dry wt ± SE = 13.90 ± 0.54) than do those from reference lakes (19.82 ± 0.33, 20.34 ± 0.63, and 22.18 ± 0.51). Lake 223 crayfish have accumulated higher tissue concentrations of both Mn (L223 value of 240 μg∙g−1dry wt compared to a mean ± SE for reference populations of 48 ± 11 μg∙g−1dry wt) and Hg(L223 value of 0.52 μg∙g−1dry wt compared to reference mean of 0.26 ± 0.05 μg∙g−1dry wt). Mn content of carapaces in crayfish from acidified L223 were also elevated threefold over background levels for the ELA region.
Responses of Fish Populations in Lake 223 to 8 Years of Experimental Acidification
Authors: Mills K. H. , Chalanchuk S. M. , Mohr L. C. , Davies I. J.
Published: June 2008

Lake 223 in the Experimental Lakes Area, northwestern Ontario, was experimentally acidified with sulfuric acid from 1976 (initial average pH 6.49) to 1981 (average pH 5.02), and then maintained at pH 5.02 to 5.13 from 1981 to 1983. Lake trout (Salvelinus namaycush), white sucker (Catostomus commersoni), fathead minnow (Pimephales promelas), and slimy sculpin (Cottus cognatus) were abundant at the onset of acidification. A decline in the abundance of fathead minnow began in 1979 (pH 5.64), and was followed first by a rapid increase in number of pearl dace (Semotilus margarita) in 1980 (pH 5.59) and then a rapid decrease in 1982 (pH 5.09). The abundance of slimy sculpin decreased rapidly in 1979. Abundances of lake trout and white sucker increased during the early years of acidification, but declined following consecutive recruitment failures starting in 1980 for trout and in 1981 for white suckers. By 1982 recruitment had ceased for all Lake 223 fishes. Survival of lake trout [Formula: see text] age 1 decreased in 1982 and 1983, but no other changes in survival of fish [Formula: see text] age 1 were detected for lake trout or white sucker. By spring 1983 many lake trout were emaciated due to losses of the lake trout food organisms. No changes in growth of lake trout and white suckers occurred during the initial years of acidification, but growth of lake trout slowed in 1982 and growth of white sucker increased in 1979.
Photoinhibition of Respiration in Epilithic Periphyton
Authors: Graham R. W. , Turner M. A.
Published: June 2008

To determine whether respiration in the light was equal to respiration in the dark we examined epilithic periphyton from a lake acidified experimentally with sulfuric acid. Because of the low concentrations of dissolved inorganic carbon, we could use both 12C and 14C uptake techniques. Using the 14C technique we could correct for residual photosynthesis in samples treated with the photosynthetic inhibitor DCMU (3-(3,4-dichlorophenyl)-1,1-dsmethyiurea). DCMU did not alter rates of dark respiration. However, respiration of DCMU-treated samples in the light was less than in the dark (P < 0.01). This photoinhibition of respiration was about 40% of dark control values. If we had calculated gross photosynthesis for the specific conditions of this experiment, but assumed incorrectly that light and dark respiration were equal, we would have overestimated gross photosynthesis by about 30%. Thus, if the ratio of respiration to photosynthesis is high, researchers will have to evaluate the effect of light on respiration to better estimate gross photosynthesis. The technique we describe, of monitoring both 12C and 14C flux in DCMU-treated samples in the light, will provide an underestimate of respiration in the light.
Perturbations in Zooplankton Communities in a Continuously Flowing Impoundment System Incubated in situ
Authors: Holoka M. H. , Lawrence S. G.
Published: June 2008

An apparatus which draws lake water, either filtered or unaltered, at a preestablished rate through four 40.75 L vessels incubated in situ is described. The system provides facilities for the synchronous addition of experimental liquids such as toxicants. All components are readily transportable. The system is self-powered for periods up to one month depending on the rate of flow chosen. This apparatus provides for the isolation of the zooplankton community from other compartments in the lake, incubation in natural conditions, experimental periods of from 1 to 30 d, maintenance of chosen concentrations of added materials continuously or non-continuously as appropriate, and entry of food organisms with concomitant dilution of wastes and metabolites.The responses of selected zooplankton species or of zooplankton communities to impoundment, manipulation of predator or prey organisms and the addition of nutrient or toxic materials can be assessed as they occur in the naturally varying conditions of a lake environment while the population is being held as a separate and defined part of the whole-lake ecosystem.Methods for the construction and use of the apparatus, and for collection of samples are described. Methods for enumerating organisms in several sizes of subsamples are assessed. Data generated in several experiments are analyzed using standard statistical methods and percent similarity indices.
Alkalinity Generation and the Fate of Sulfur in Lake Sediments
Authors: Anderson Robert F. , Schiff Sherry L.
Published: June 2008

Recent studies of major ion budgets of lakes have demonstrated the occurence of within-lake alkalinity generation, or acid consumption, that may represent a significant source of buffering against acid precipitation. Consumption of sulfate is associated with a major portion of alkalinity generation. Sources of alkalinity, and the capacities of lakes to neutralize sulfuric acid, corresponding to each of the probable fates of sulfur have not been discussed explicitly in earlier papers. This note was written to clarify these points.
Annual Supply of 238U, 234U, 230Th, 226Ra, 210Pb, 210Po, and 232Th to Lake 239 (Experimental Lakes Area, Ontario) from Terrestrial and Atmospheric Sources
Authors: Brunskill G. J. , Wilkinson P.
Published: June 2008

The activities of 238U, 234U, 230Th, 226Ra, 210Pb, 210Po, and 232Th were measured in seasonal samples of stream runoff water, suspended and bedload sediments, and bulk precipitation. These nuclides were also determined in stream drainage area soils and bedrock. From these measurements and hydrological data, an estimate of the annual supply of these nuclides to Lake 239 at the Experimental Lakes Area (ELA) was made. Because of low concentrations of major ions, suspended sediments, and low pH, many common stream transport mechanisms for these nuclides are not available, and we propose that dissolved organic carbon is important in this respect. The annual flux (per unit stream drainage area) of these nuclides to the lake is similar to fluxes calculated for larger rivers of the world. Uranium-234 is transported preferentially to 238U at activity ratios of 1–1.3. Radium-226 is carried in solution in proportion to Ca++. The major supply of 210Pb to the lake is from atmospheric fallout on the lake surface area. There are insufficient 222Rn or 210Pb deficits in the soil profiles to balance the measured excess 210Pb in surface soils and lake sediments. Partition coefficients for these nuclides were calculated from data on stream suspended sediments and stream water; U and Ra coefficients were ≈ 104, and Th, 210Pb, and 210Po coefficients were 104 to 105.
Determining Sediment Accumulation and Mixing Rates Using 210Pb, 137Cs, and Other Tracers: Problems Due to Postdepositional Mobility or Coring Artifacts
Authors: Anderson Robert F. , Schiff Sherry L. , Hesslein Raymond H.
Published: June 2008

Sediment profiles of 137Cs in 12 lakes and of radionuclides (60Co, 134Cs, 226Ra) added experimentally to four lakes at the Experimental Lakes Area, northwestern Ontario, were inconsistent with sediment chronologies derived from 210Pb distributions. Peaks in the 37Cs profiles were sometimes shallower than the depth corresponding to the 1963 fallout maximum (based on 210Pb chronology) and sometimes 137Cs peaks were not observed at all. Expected peaks in the profiles of experimentally added nuclides were similarly absent in three of four lakes. The absence of these peaks at depths corresponding to their time of maximum input to the lakes probably resulted from the initial uptake of the nuclides by littoral sediments followed by the winnowing over periods of several years of nuclide-tagged fine particles to the deeper parts of the basins where the cores were collected. Sediment focussing is manifested by 210Pb sediment inventories at the coring sites greatly exceeding inventories that can be supported by atmospheric deposition of 210Pb in this area.137Cs and the experimentally added nuclides were found much deeper in the cores than the depths corresponding to the time of their initial inputs to the lakes based on 210Pb chronologies. Diffusion of the nuclides in the pore waters could explain some of their downward penetration. However, in some cases, the profiles could only be fit if the effective diffusion coefficient increased with depth. This situation might reflect mixing of these high porosity sediments during core collection or extrusion.Distributions of 137Cs and of the experimentally added nuclides do not provide valid chronologies which can be used to date other features recorded in the sediments of these lakes. Although unsupported 210Pb profiles in these lakes provided excellent fits to classical steady-state sediment accumulation models, 210Pb profiles too may have been affected by sediment mixing or core disturbance. Further studies are necessary to test the reliability of 210Pb-based sediment chronologies in high porosity sediments such as those studied at ELA.
Methods and Feasibility of Using Aluminum-26 as a Biological Tracer in low pH Waters
Authors: Playle Richard C.
Published: June 2008

The fate of aluminum accumulated by fish can be studied using 26Al as a tracer, but the present cost of 26Al will keep experiments to a small scale and replication to a minimum. The methods developed for liquid scintillation counting of 26Al uptake will be most useful with exposures to low Al concentrations, where changes in Al concentration cannot be measured using other methods. Preliminary results showed that the gills and whole bodies of redbelly dace (Chrosomus eos Cope) accumulated more Al, when exposed to 480 μg∙L−1 Al at pH 5.1, than dace exposed to 200 μg∙L−1 Al at the same pH.
Application of Removal Sampling to Estimate the Density of Ringed Seals (Phoca hispida) in Barrow Strait, Northwest Territories
Authors: Hammill M. O. , Smith T. G.
Published: June 2008

The density of ringed seals (Phoca hispida) in 2 to 4 km2 study plots was determined using a combination of removal sampling to determine density of seal holes and estimates of hole to seal ratios. A dog survey technique was adapted to removal sampling, where seal holes located under the snow by the dogs during surveys of fixed effort were marked and treated as removals from the population. Computer simulation indicates that estimates of seal hole density are within 10% of the true population size if for each plot there are [Formula: see text] searches, sampling intensity is [Formula: see text], the coefficient of variation of the estimate is [Formula: see text], and the probability of detecting a seal hole is [Formula: see text]. The quality of survey results was affected by the number of dogs used to survey each plot, plot size, and surface topography. Densities of seal holes varied from 4.8 to 7.9 holes∙km−2. Eight seals had an average hole to seal ratio of 3.4. Seal densities ranged from 1.4 to 2.3 seals∙km−2, and may be much higher if pup production is included.
Changes in Species Interactions of the Lake Superior Fisheries System After the Control of Sea Lamprey as Indicated by Time Series Models
Authors: Stone Jeff N. , Cohen Yosef
Published: June 2008

Interspecific and intraspecific interactions of fish species in the Canadian commercial fisheries changed following the control of sea lamprey (Petromyzon marinus). These changes were detected by a multivariate time series (MVTS) analysis of monthly time series of catch-per-unit-effort for lake trout (Salvelinus namaycush), lake whitefish (Coregonus clupeaformis), lake herring (C. artedii), chubs (Coregonus spp.), walleye (Stizostedion vitreum), and yellow perch (Perca flavescens). The identified MVTS models reflected known trophic relationships among fish species and indicated that significant intraspecific interactions were more numerous than interspecific interactions. Lake trout interactions with other species appear to have changed due to stocking and diet change. Single species time series models confirmed the lag structure of the MVTS models and were useful for forecasting abundance.
Dynamics of Age and Size Composition in a Population Subject to Size-Selective Mortality: Effects of Phenotypic Variability in Growth
Authors: Parma Ana M. , Deriso Richard B.
Published: June 2008

A stochastic model for the dynamics of age and size distributions in a population subject to size-selective mortality is derived. Growth variability results from both environmental disturbances and intrinsic differences in the expected asymptotic length of the individuals. The selective harvest of larger fish results in a selective removal of intrinsically faster-growing individuals. Estimation trials indicate that sources of growth variability are difficult to identify from standard catch information. The implications of this uncertainty in a yield per recruit analysis are explored, using parameter estimates of Pacific halibut (Hippoglossus stenolepis). At moderate fishing levels yield per recruit increased with the amount of intrinsic variability, but the trend reversed at higher fishing rates. Fishing mortality for maximum expected yield per recruit decreased when the contribution of intrinsic differences to growth variability was larger. Mean spawning biomass was relatively insensitive to the level of phenotypic variability when the population was under moderate-to-heavy exploitation. A standard assumption of yield per recruit analysis, namely, that age-specific selectivities and catch weights are constant, independent of the fishing mortality rate, may result in biassed estimates of mean spawning biomass per recruit, and serious overestimation of optimal fishing levels.
Patterns in the Submerged Macrophyte Biomass of Lakes and the Importance of the Scale of Analysis in the Interpretation
Authors: Duarte Carlos M. , Kalff Jacob
Published: June 2008

The relative contributions of lake characteristics (i.e. alkalinity, chlorophyll A concentration, total phosphorus concentration, conductivity, and morphometry) and site characteristics (i.e. depth, littoral slope, exposure to waves, and underwater light levels) to the variability in submerged biomass were examined in 25 Canadian and American lakes. Lake-average submerged biomass is a function of water alkalinity and the lake-average littoral slope whereas site-specific biomass is a function of both site and lake characteristics. Plant biomass decreased with increasing slope and wave exposure and increased with increasing alkalinity and light levels. However, these relationships are complex because submerged biomass is also influenced by threshold phenomena (e.g. critical littoral slopes and transparency-dependent critical depths) that set limits to macrophyte colonization and because the relative contributions of the most relevant environmental factors studied (i.e. littoral slope, exposure, water transparency, and alkalinity) are depth dependent. By demonstrating the importance of lake-average and site-specific scales of variation and the existence of noncontinuous (e.g. threshold) regulation mechanisms the findings provide a new conceptual framework for the study of the relationship between submerged macrophytes, and their associated biota as well as their environment.
Relative Importance of Phosphorus Supply to Phytoplankton Production: Fish Excretion versus External Loading
Authors: Brabrand Åge , Faafeng Bjørn Andreas , Moritz Nilssen Jens Petter
Published: June 2008

In laboratory tanks with bream (Abramis brama), perch (Perca fluviatilis), and roach (Rutilus rutilus) concentrations of phosphorus and nitrogen increased with time. Phosphorus was mainly released as soluble molybdate-reactive phosphorus (SRP); nitrogen almost exclusively as ammonium. The release increased with the species' tendency to forage on littoral sediments and with a smaller fish size. Bioassays with the test algae Selenastrum capricornutum showed that released phosphorus was readily available to algal growth. The total supply of phosphorus to the epilimnion of Lake Gjersjøen was calculated from the external supply from the tributaries and the estimated phosphorus release from total roach biomass. From May to October 1980 phosphorus release from the roach population contributed about the same order of magnitude as the total phosphorus loading from the watershed. During the period with the most serious phosphorus depletion to the phytoplankton (July, August, and September), the phosphorus supply from fish was about double that of the external phosphorus supply, confirming the important role of sediment-feeding fish populations in the eutrophication processes of lakes.
Vertical Migration in Daphnia galeata mendotae (Brooks): Demographic Responses to Changes in Planktivore Abundance
Authors: Stirling D. G. , McQueen D. J. , Johannes M. R. S.
Published: June 2008

We tested the hypothesis that changes in vertical migration patterns in Daphnia galeata mendotae were correlated with changes in planktivore numbers. A 4-yr data set from Lake St. George showed that during 1982, when planktivores numbered approximately 2500∙ha−1, adult D. galeata mendotae were found in the epilimnion at both midday and midnight. During 1984 and 1985, when planktivores were almost an order of magnitude more abundant, adult D. galeata mendotae were detected in the epilimnion only at night, and the amplitude of migration increased by a factor of two. Changes in diel population densities were associated with these interannual differences in vertical migration patterns. These results suggest that between-year differences in vertical migration patterns were strongly associated with changes in planktivore density which may have influenced the selective value of increased hypolimnetic residence time.
Whole-Lake and Nearshore Water Chemistry In Bowland Lake Before and After Treatment with CaCO3
Authors: Molot Lewis A. , Dillon Peter J. , Booth Gillian M.
Published: June 2008

After neutralization of Bowland Lake, a clear oligotrophic acidified lake, with CaCO3in August 1983, the whole-lake pH and alkalinity increased from 4.9 and −6 μeq∙L−1to 6.7 and 89 μeq∙L−1, respectively. Total whole-lake Al decreased gradually from 130 to 30 μg∙L−1, Mn decreased from 80 to 28 μg∙L−1and the lake became less transparent as dissolved organic carbon (DOC) increased and Secchi depth decreased. Metals other than Al and Mn remained low and did not respond to neutralization. Between August 1983 and March 1986, about 40% of the added alkalinity of Bowland Lake was lost. Decreases of whole-lake pH following snowmelt occurred prior to but not after neutralization. Neutralization of lake water did not prevent acidic melt water from forming a distinctive acidic zone < 1 m thick beneath the ice. The melt layer was more acidic than lake water, it was colder and therefore less dense, it usually contained higher Al, and it was dilute with lower conductivity and Ca. intra-site variation was probably due to variable volumes of melt water received. A snowmelt model based on daily air temperature and precipitation predicted intermittent recharge of groundwater reservoirs during snowmelt. However, runoff was continually observed nearshore under ice suggesting that groundwater reservoirs continued to discharge after recharge ended or that the residence time of melt waters in the littoral zone was relatively long.
Effects of Neutralization and Early Reacidification on Filamentous Algae and Macrophytes in Bowland Lake
Authors: Jackson Michael B. , Vandermeer Elizabeth M. , Lester Nigel , Booth Jacqueline A. , Molot Lewis , Gray Isobelle M.
Published: June 2008

Within one year of neutralizing Bowland Lake (pH 4.8–5.5 increased to 6.3–6.7), previously extensive growths of filamentous algae et (Mougeotia and Zygogonium, > 10 and 100% shoreline coverage, respectively) were essentially eliminated (< 1% shoreline coverage). Reacidification in the second year (pH 5.7–6.7) was accompanied by increased submerged epilithic and epiphytic growths of predominantly Zygogonium, often to preliming coverage. As found in other studies, pH [Formula: see text] appears to represent a threshold relative to the predominance of certain filamentous algae in softwater lakes. The short time between the change in acidity and the disappearance and reappearance of the filamentous algae suggests that they may be important biological indicators or predictors of acidification and its reversal. The changes in pH and alkalinity following neutralization did not substantially affect the macrophyte community in Bowland Lake. Macrophytes were restricted primarily to littoral areas less than 3 m in depth, despite excellent water transparency both before (SD = 8.0 m, 1982) and after neutralization (SD = 4.5 m, 1985). Two uncommon species observed prior to neutralization (Eleocharis parvula and E. acicularis) were not observed afterwards, while two new and uncommon species (Nitella sp. and Brasenea schreberi) were.
Changes in the Zoobenthos Community of Acidified Bowland Lake after Whole-Lake Neutralization and Lake Trout (Salvelinus namaycush) Reintroduction
Authors: Keller W. , Molot Lewis A. , Griffiths Ronald W. , Yan N. D.
Published: June 2008

The zoobenthos of Bowland Lake is described prior to, and for 2 yr after, neutralization of the lake from pH 4.9 to > 6.0 and reintroduction of lake trout (Salvelinus namaycush). Observed changes in the total abundance, biomass, and size structure of shallow and profundal zoobenthos assemblages were attributable to changes in the fish community, not to improvements in water quality. A shift toward increased importance of oligochaetes, more representative of nonacidic conditions, occurred. However, many common, acid-sensitive taxa of zoobenthos which were absent prior to neutralization had not appeared within 2 yr after treatment, indicating insufficient time for recolonization.
Survival, Growth, and Reproduction of Lake Trout (Salvelinus namaycush) and Yellow Perch (Perca flavescens) after Neutralization of an Acidic Lake Near Sudbury Ontario
Authors: Gunn J. M. , Hamilton J. G. , Booth G. M. , Wren C. D. , Beggs G. L. , Rietveld H. J. , Munro J. R.
Published: June 2008

Bowland Lake, an acidified lake (pH 4.8–5.2), was treated with calcite (CaCO3) in 1983. Neutralization allowed for successful reproduction by reintroduced lake trout (Salvelinus namaycush). Mortality of lake trout embryos and juveniles in field toxicity tests decreased from 52–99% preneutralization to 0–30% postneutralization. The resident yellow perch (Perca flavescens) appeared unaffected by the chemical treatment. Both inter- and intra-specific competition were evident in the growth and body condition of perch and stocked lake trout in the years after neutralization. Springtime acid episodes continued to occur in the nearshore areas after the lake was neutralized, but no adverse effects on fish species were detected.
Change in the Known Ocean Distribution of Japanese Chum Salmon, Oncorhynchus keta, in Relation to the Progress of Stock Enhancement
Authors: Ogura Miki , Ito Soto-o
Published: June 2008

New information on the ocean distribution of maturing Japanese chum salmon, Oncorhynchus keta, based on offshore tagging experiments conducted from 1956 to 1991 is summarized. Of 138 039 chum released in the North Pacific Ocean and its adjacent seas, 663 fish were recovered along the Japanese coast in the year of tagging and up to March of the next year. The distribution area of maturing Japanese chum indicated by these tag recoveries extended much further south and west than shown in previous studies. The central and western North Pacific Ocean now form important parts of the range. We conclude that extensive stock enhancement of chum in Japan is associated with enlargement of the known distribution area of maturing Japanese chum in the North Pacific Ocean.
Metabolic Costs and Physiological Consequences of Acclimation to Aluminum in Juvenile Rainbow Trout (Oncorhynchus mykiss). 2: Gill Morphology, Swimming Performance, and Aerobic Scope
Authors: Wilson Rod W. , Bergman Harold L. , Wood Chris M.
Published: June 2008

Juvenile rainbow trout (Oncorhynchus mykiss, 5–13 g) were chronically exposed to sublethal Al (38 μg∙L−1) in acidified soft water (Na+ = 85, Ca2+ = 28 μEq∙L−1, pH 5.2–5.4) for 36 d. Acclimation (increased resistance to challenge with 162 μg Al∙L−1Al at pH 5.2) occurred after 5 d and was associated with a fourfold increase in gill mucous cell density and reduction in apparent lamellar surface area; initially elevated blood–water diffusion distances returned to normal after 34 d, but the reduction in apparent surface area persisted. Chronic exposure to acid alone (pH 5.2, same water chemistry) caused no morphometric changes but resulted in persistent impairment of Ucrit(critical aerobic swimming speed) by about 10%. This was due to increased oxygen requirements at subcritical swimming speeds (loading stress) and was alleviated when trout were swum at pH 6.5 (zero Al) on day 36. In trout preexposed to sublethal Al, Ucritwas chronically impaired by approximately 16% due to loading stresses and reduction in the maximum rate of oxygen uptake, Mo2max(limiting stress); Ucritand Mo2maxremained depressed even when fish were swum at pH 6.5 (zero Al). Reduced gill area compromises the aerobic scope for activity but may be an unavoidable cost of acclimation to Al.