bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature influences the population structure of nitrite‐oxidizing bacteria in activated sludge
Authors: Alawi M. , Off S. , Kaya M. , Spieck E.
Published: April 2009

Activated sludge from the municipal waste water treatment plant in Hamburg was seeded with mineral nitrite medium and incubated at 10°C, 17°C and 28°C. Dominant lithoautotrophic nitrite‐oxidizing bacteria have been identified by electron microscopy, denaturing and temperature gradient gel electrophoresis and PCR with genus‐specific primer pairs. The results have revealed the existence of three different genera of nitrite‐oxidizing bacteria, namely Nitrospira, Nitrobacter and a novel cold‐adapted nitrite oxidizer. As shown by electron microscopy members of the novel genus coexisted in activated sludge together with Nitrospira. A temperature‐dependent shift in the population structure was demonstrated by cultivation‐based approaches. The novel nitrite oxidizer was enriched at temperatures of 10°C and 17°C. Representatives of Nitrospira were able to grow in a broad temperature range between 10°C and 28°C and members of Nitrobacter were enriched during incubations at 17°C and 28°C. By subsequent 16S rDNA sequencing, the cold‐adapted nitrite oxidizer was shown to be closely related to the betaproteobacterium ‘Candidatus Nitrotoga arctica’. These findings demonstrated that the population structure of nitrite‐oxidizing bacteria in activated sludge is more complex than previously thought and responds strongly to long‐term temperature changes.
Validation of the Sysmex XT‐2000iV hematology system for dogs, cats, and horses. II. Differential leukocyte counts
Authors: Lilliehöök Inger , Tvedten Harold
Published: April 2009

Background: The Sysmex XT‐2000iV is a laser‐based, flow cytometric hematology system that stains nucleic acids in leukocytes with a fluorescent dye. A 4‐part differential is obtained using side fluorescence light and laser side scatter.

Objective: The purpose of this study was to validate the Sysmex XT‐2000iV for determining differential leukocyte counts in blood from ill dogs, cats, and horses.

Methods: Blood samples from diseased animals (133 dogs, 65 cats, and 73 horses) were analyzed with the Sysmex XT‐2000iV (Auto‐diff) and the CELL‐DYN 3500. Manual differentials were obtained by counting 100 leukocytes in Wright‐stained blood smears.

Results: Leukocyte populations in the Sysmex DIFF scattergram were usually well separated in equine samples, but were not as well separated in canine and feline samples. Correlation among the Sysmex XT‐2000iV, CELL‐DYN 3500, and manual counts was excellent for neutrophil counts (r ≥.97) and good for lymphocyte counts (r ≥.87) for all three species. Systematic differences between the 3 methods were seen for lymphocyte and monocyte counts. The Sysmex reported incomplete differential counts on 18% of feline, 13% of canine, and 3% of equine samples, often when a marked left shift (>10% bands) and/or toxic neutrophils were present. Eosinophils were readily identified in cytograms from all 3 species. Neither the Sysmex nor the CELL‐DYN detected basophils in the 7 dogs and 5 cats with basophilia.

Conclusions: The Sysmex XT‐2000iV automated differential leukocyte count performed well with most samples from diseased dogs, cats, and horses. Basophils were not detected. Immature neutrophils or prominent toxic changes often induced errors in samples from cats and dogs.
Cytologic interpretation of canine cerebrospinal fluid samples with low total nucleated cell concentration, with and without blood contamination
Authors: Doyle Clare , Solano‐Gallego Laia
Published: April 2009

Background:Cerebrospinal fluid (CSF) is potentially altered by iatrogenic blood contamination at the time of sampling due to the addition of blood‐associated leukocytes and protein.

Objectives:The objective of this study was to assess whether protein concentration, neutrophil percentage, and the presence of activated macrophages, reactive lymphocytes, or eosinophils in CSF samples with low total nucleated cell concentration (TNCC) are affected by blood contamination or associated with central nervous system (CNS) disease.

Methods:Case records from the Royal Veterinary College Diagnostic Laboratory were searched retrospectively for dogs with CSF having ≤5 TNCC/μL. TNCC, RBC, and protein concentrations; neutrophil percentage; and the presence of activated macrophages, reactive lymphocytes, and eosinophils were recorded. Results of magnetic resonance imaging (MRI) also were recorded as a marker of CNS disease.

Results:Of 906 cases evaluated, 106 (12%) had blood contamination (>500 RBCs/μL) in CSF. Protein concentration and neutrophil percentage were significantly higher and the presence of eosinophils was more likely in blood contaminated vs noncontaminated samples. Non‐blood‐contaminated samples with activated macrophages or reactive lymphocytes had higher protein concentrations and neutrophil percentages, and those with activated macrophages were more likely to have a positive finding on MRI.

Conclusions:Protein concentration, neutrophil percentage, and the presence of eosinophils are significantly affected by blood contamination in canine CSF having low TNCC. Activated macrophages and reactive lymphocytes are not affected by blood contamination, however, and may be useful in identifying dogs with CNS abnormalities.
Adipokines: a review of biological and analytical principles and an update in dogs, cats, and horses
Authors: Radin M. Judith , Sharkey Leslie C. , Holycross Bethany J.
Published: April 2009

Abstract:In addition to its role as an energy storage depot, adipose tissue is now recognized as a complex endocrine organ. Adipose tissue releases a variety of factors, termed adipokines, that regulate energy metabolism, cardiovascular function, reproductive status, and immune function. Some of the better‐studied adipokines include leptin, adiponectin, and components of the renin‐angiotensin system such as angiotensinogen. The function of more recently discovered adipokines such as resistin are under intense scrutiny. Abnormal production or regulation of adipokines occurs in obese individuals and is implicated in the development of a variety of associated co‐morbidities including metabolic syndrome, type 2 diabetes, atherosclerosis, heart disease, and cancer in people, although evaluation in domestic species is just beginning. Adipokines are now being examined as potential biomarkers for risk assessment for development of complications related to obesity. This article summarizes the function and regulation of some better‐characterized adipokines. It also reviews the current information on the characterization of adipokines in some domestic species in which rates of obesity and obesity‐related disorders are increasing, such as the dog, cat, and horse.
Evaluation of platelet function in dogs with cardiac disease using the PFA‐100 platelet function analyzer
Authors: Clancey Noel , Burton Shelley , Horney Barbara , MacKenzie Allan , Nicastro Andrea , Côté Etienne
Published: April 2009

Background:Cardiac disease has the potential to alter platelet function in dogs. Evaluation of platelet function using the PFA‐100 analyzer in dogs of multiple breeds and with a broad range of cardiac conditions would help clarify the effect of cardiac disease on platelets.

Objectives:The objective of this study was to assess differences in closure time (CT) in dogs with cardiac disease associated with murmurs, when compared with that of healthy dogs.

Methods:Thirty‐nine dogs with cardiac murmurs and turbulent blood flow as determined echocardiographically were included in the study. The dogs represented 23 different breeds. Dogs with murmurs were further divided into those with atrioventricular valvular insufficiency (n=23) and subaortic stenosis (n=9). Fifty‐eight clinically healthy dogs were used as controls. CTs were determined in duplicate on a PFA‐100 analyzer using collagen/ADP cartridges.

Results:Compared with CTs in the control group (mean±SD, 57.6±5.9 seconds; median, 56.5 seconds; reference interval, 48.0–77.0 seconds), dogs with valvular insufficiency (mean±SD, 81.9±26.3 seconds; median, 78.0 seconds; range, 52.5–187 seconds), subaortic stenosis (71.4±16.5 seconds; median, 66.0 seconds; range, 51.5–95.0 seconds), and all dogs with murmurs combined (79.6±24.1 seconds; median, 74.0 seconds; range, 48.0–187 seconds) had significantly prolonged CTs (P<.01).

Conclusions:The PFA‐100 analyzer is useful in detecting platelet function defects in dogs with cardiac murmurs, most notably those caused by mitral and/or tricuspid valvular insufficiency or subaortic stenosis. The form of turbulent blood flow does not appear to be an important factor in platelet hypofunction in these forms of cardiac disease.
Charging and structure of zwitterionic supported bilayer lipid membranes studied by streaming current measurements, fluorescence microscopy, and attenuated total reflection Fourier transform infrared spectroscopy
Authors: Zimmermann Ralf , Küttner David , Renner Lars , Kaufmann Martin , Zitzmann Jan , Müller Martin , Werner Carsten
Published: April 2009

The authors report on the characterization of the charge formation at supported bilayer lipid membranes (sBLMs) prepared from the zwitterionic lipid 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine on planar silicon dioxide substrates. The charging of the sBLMs was studied in KCl solutions of different ionic strengths between 0.1 and 10 mM by streaming current measurements. In addition, attenuated total reflection Fourier transform infrared spectroscopy and fluorescence microscopy were applied to determine the lipid concentration in the membrane and to study the influence of the harsh conditions (pH 9-2, shear forces) during the electrokinetic measurements on the membrane stability and the lipid diffusion coefficient. The sBLMs were found to be extremely stable. Isoelectric points of about 4 revealed that unsymmetrical adsorption of hydroxide and hydronium ions determined the charging of the outer leaflet of the membrane in the investigated pH range. The diffusion coefficients were found to be rather independent on the ionic strength at neutral and alkaline pH. However, significantly decreased lipid diffusion at pH<4 indicated a charge-induced transition of the fluidic bilayer into a gel/ordered-phase bilayer.
Zeta potential of motile spores of the green alga Ulva linza and the influence of electrostatic interactions on spore settlement and adhesion strength
Authors: Rosenhahn Axel , Finlay John A. , Pettit Michala E. , Ward Andy , Wirges Werner , Gerhard Reimund , Callow Maureen E. , Grunze Michael , Callow James A.
Published: April 2009

The zeta potential of the motile spores of the green alga (seaweed) Ulva linza was quantified by video microscopy in combination with optical tweezers and determined to be −19.3±1.1 mV. The electrostatic component involved in the settlement and adhesion of spores was studied using electret surfaces consisting of PTFE and bearing different net charges. As the surface chemistry remains the same for differently charged surfaces, the experimental results isolate the influence of surface charge and thus electrostatic interactions. Ulva spores were demonstrated to have a reduced tendency to settle on negatively charged surfaces and when they did settle the adhesion strength of settled spores was lower than with neutral or positively charged surfaces. These observations can be ascribed to electrostatic interactions.
Abnormal salt effects on a cation/anion reaction. An interpretation based on the analysis of the components of the experimental rate constant
Authors: Sánchez Francisco , Perez-Tejeda Pilar , Jimenez Rafael , Villa Isaac
Published: April 2009

Salt effects (NaNO3) on the kinetics of the reactions [Fe(CN)6]3– + [Ru(NH3)5(pyz)]2+ = [Fe(CN)6]4– + [Ru(NH3)5(pyz)]3+ (pyz = pyrazine) were studied through T-jump measurements. An abnormal (positive) salt effect on the forward reaction was observed and a normal (negative) effect on the reverse one. These facts imply an asymmetric behavior of anion/cation reactions depending on the charge sign of the oxidant and reductant. The results can be rationalized by using the Marcus–Hush treatment for electron-transfer reactions after decomposition of the experimental rate constants into their components.
Temperature and Lobster, Homarus americanus, Yield Relationships
Authors: Campbell A. , Noakes D. J. , Elner R. W.
Published: April 2009

Commercial landings of American lobster (Homarus americanus) have increased dramatically in many areas along the east coast of Canada since the late 1970's. Average annual sea surface temperatures (SST) were analysed to test if lobster landings were related to changes in the marine environment. Time series models were fitted to lobster landings and SST data from Maine (USA), Halifax County (Nova Scotia), and Charlotte County (New Brunswick). Including temperature in the models improved forecasting ability for lobster catches for Maine and Halifax but not Charlotte. In Maine, lobster landings in year t were related to SST in year t. In Halifax, however, landings were related to SST in the previous 4 yr but not by SST of the current year. Lower fishing effort levels for Halifax compared with Maine probably extended the yield from strong year-classes through a number of years. We surmise that an increase in sea temperature near Halifax during the early 1980's increased the survival and growth rates of lobster juveniles. This provided a strong pulse of recruits to the fishery throughout coastal Nova Scotia during the mid- to late 1980's. Similar increases in temperature and landings were not observed for Maine and Charlotte.
Effects of Salinity on Growth, Metabolism, and Ion Regulation in Juvenile Rainbow and Steelhead Trout (Oncorhynchus mykiss) and Fall Chinook Salmon (Oncorhynchus tshawytscha)
Authors: Morgan John D. , Iwama George K.
Published: April 2009

Rainbow and steelhead trout (Oncorhynchus mykiss) and fall chinook salmon (Oncorhynchus tshawytscha) fry were acclimated to a range of salinities to test the hypothesis that the energy requirements for ion regulation would be minimal at an isotonic water salinity (8–10 ppt). Survival, growth, metabolic rate, plasma Na+ and Cl− concentrations, and seawater adaptability were measured for 5–12 wk, depending on the species. Growth of all three species was highest in fresh water and declined with increasing salinity. Metabolic rates increased with salinity and were inversely correlated with growth rates. Isotonic salinity, therefore, did not offer significant metabolic or growth advantages to rainbow, steelhead, and chinook fry. While plasma Na+ and Cl− concentrations varied among groups, chinook fry tended to better maintain ionic homeostasis at higher salinities than the trout. Acclimation to the various dilute salinities did not influence the seawater adaptability of juvenile steelhead trout or chinook salmon. Our results indicate that optimal salinities for growth and metabolic rates were influenced by species and life history stage. The metabolic rate data suggested that the energetic cost of ionic regulation increased with salinity, but attempts to quantify this cost were probably affected by other metabolic processes which responded to changes in salinity.
Size-Dependent Spatial Distribution of Hake (Merluccius capensis and Merluccius paradoxus) in Namibian Waters
Authors: Gordoa Ana , Duarte Carlos M.
Published: April 2009

Data on hake (Merluccius capensis and Merluccius paradoxus) abundance along the Namibian coast showed both species to have strongly aggregated spatial distributions. In addition, average fish size increased with depth, suggesting that the formation of hake aggregation is based on size-dependent shoaling behaviour. Hake spacing was size dependent with areal fish density and biomass being scaled to the −5 and −2 power, respectively, of fish length. The equations describing the size dependence of the areal fish density were log density (fish∙m−2) = 5.06-4.91 log size (cm) for M. capensis and log density (fish∙m−2) = 5.28-4.74 log size (cm) for (M. paradoxus). The maximum areal densities, presumably corresponding to those within the shoals, exceeded those described by the equations above by 20- and 13-fold for M. capensis and M. paradoxus, respectively. The size dependence of hake spacing implies that fishing pressure targeting aggregates of small hake (i.e. shallow shoals) should have a disproportionate effect on fish mortality and recruitment compared with similar fishing pressure targeting aggregates of larger hake (i.e. deep shoals).
Genetic Variation and Fitness: A Test in a Naturalized Population of Brook Trout (Salvelinus fontinalis)
Authors: Liskauskas Arunas P. , Ferguson Moira M.
Published: April 2009

The relationship between enzyme heterozygosity and several components of fitness (size and survival) was examined in a naturalized population of brook trout (Salvelinus fontinalis) from Algonquin Provincial Park, Ontario. Significant differences in allele frequency and the number of heterozygous loci per individual were found among five age classes spanning most of the life history stages of brook trout in this population. A young of the year (YOY) cohort sampled after a period of high natural mortality had significantly greater numbers of heterozygous loci per individual than YOY sampled shortly after emergence from redd sites. A positive association between heterozygosity and size was only found in YOY sampled in June and not in the other age classes in which sexual maturity was not a complicating factor. The association between heterozygosity and size was affected by the onset of sexual maturity. Significant negative regressions between multilocus or single locus heterozygosity and size were found in mature males whereas heterozygosity was positively associated with size in females. These dissimilarities may be the result of differences in growth rates prior to sexual maturation and differential allocation of energy towards gametic and somatic tissue.
Selecting Loci for Genetic Stock Identification Using Maximum Likelihood, and the Connection with Curvature Methods
Authors: Millar R. B.
Published: April 2009

Maximum likelihood theory is used to predict the precision of genetic stock identification composition estimators — prior to collection of the mixed fishery sample. It is shown how this allows the researcher to plan the genetic stock identification study, through specification of sample size and choice of genetic data to assay, so as to maximize estimator precision. The curvature methodology used in Gomulkiewicz et al. (1990. Can. J. Fish. Aquat. Sci. 47: 611–619) is shown to be closely related to the maximum likelihood approach. In that study, interpretation of results is complicated by the use of an overparametrized curvature measure. Here it is shown that when applied to an appropriately parametrized likelihood function the curvature methodology reproduces the maximum likelihood theory.
Systematics and Distributions of Dolly Varden (Salvelinus malma) and Bull Trout (Salvelinus confluentus) in North America
Authors: Haas Gordon R. , McPhail J. D.
Published: April 2009

Dolly Varden char in North America separate into two species: Dolly Varden (Salvelinus malma (Walbaum)) and bull trout (Salvelinus confluentus (Suckley)). Principal component analyses reveal two distinct morphotypes, and a linear discriminant function is derived (based on three field measureable variables) for their consistent classification. No single character can always distinguish both species, although branchiostegal ray number often will. The morphology of the two species remains relatively constant across their large ranges. The two species occur in strict sympatry in several areas with no evidence of interbreeding. The two species also exist parapatrically or syntopically and appear to exhibit broad scale competitive exclusion in these situations. Dolly Varden are distributed largely along the coast and range further north, while bull trout are mostly interior and range further south. Laboratory crosses demonstrate that the morphology of both species remain distinctive when they are reared under similar conditions and that their artificial hybrids are morphologically intermediate. No such natural hybrids were conclusively found, and there is no evidence of introgression.
Morphological Basis of the Pectoral Fin Flutter of Embryonic Atlantic Salmon (Salmo salar)
Authors: Peterson R. H. , Power J. , Martin-Robichaud D. J.
Published: April 2009

The pectoral fin of embryonic Atlantic salmon (Salmo salar) flutters rhythmically through most of the early development, probably to promote water currents near embryonic respiratory surfaces. A descriptive mechanical model of the anatomical basis of the fin movements involves four components. The basal coraco-scapular complex serves as a fulcrum for fin movements. The actinost forms a thin vane, which is alternately abducted and adducted by two opposing muscle groups originating on the coraco-scapular cartilage and inserting distally on the actinost. The last component, the fin membrane, moves as a result of travelling waves passing distad as a result of flexion of the actinost — a "whiplash" type of motion. The first five spinal nerves may be involved in generation of the rhythmic flutter.
Modeling of Recruitment Patterns in Pacific Cod (Gadus macrocephalus) in Hecate Strait, British Columbia
Authors: Tyler A. V. , Crawford W. R.
Published: April 2009

We combined published recruitment hypotheses into a single modeling framework and explored the relative contributions of the hypothesis factors to recruitment variation in Pacific cod (Gadus macrocephalus). Our five hypotheses were (1) recruitment decreased with increasing transport during the larval period; (2) recruitment was related to percentage hatching success as a dome-shaped curve with a peak between 4.0 and 5.0 °C; (3) recruitment was positively related to abundance of age-0 juvenile Pacific herring (Clupea harengus pallasi) hatched in the same year as the cod; (4) recruitment was positively related to abundance of age-0 and age-1 herring in the year prior to spawning; and (5) a dome-shaped curve related recruitment to adult stock size. We used new records for temperature, and a new index of advection based on measures of current in Hecate Strait. For fitting a response surface with age-3 cod recruitment as the independent variable, we used a 20-yr data series of variables from 1962 to 1981 inclusive and reserved data for the years 1982–85 for a prediction test. Only hypotheses 1 and 5 were supported by both the response surface fit and prediction tests. The stock–recruitment curve can be fitted only when the transport curve is fitted simultaneously.
Use of Zooplankton to Assess the Movement and Distribution of Alewife (Alosa pseudoharengus) in South-Central Lake Ontario in Spring
Authors: O'Gorman Robert , Mills Edward L. , DeGisi Joe
Published: April 2009

Data from assessments of fish and zooplankton conducted during April and May–June 1986–88 in south-central Lake Ontario were examined for evidence that zooplankton size structure can be used to follow the movement of alewife (Alosa pseudoharengus). The spring influx of alewife into nearshore waters was linked with water temperature and coincided with a decline in the mean length of crustacean zooplankton and the virtual disappearance of zooplankters [Formula: see text]. Alewife moving inshore to spawn fed heavily on the largest zooplankters, negating the possibility that changes in zooplankton size were wholly a response to seasonal recruitment as waters warm and the composition shifts to Bosmina. Offshore, there was usually no significant (P < 0.05) change in mean lengths of zooplankton in the upper water column between April and May–june, and zooplankters [Formula: see text] always remained abundant, suggesting that few alewife were there from April through mid-june. We conclude that in large freshwater lakes where a planktivore is abundant, yet spatially concentrated, changes in size of crustacean zooplankton can facilitate understanding of the fish's movement and distribution.
Stable Isotopes of Sulfur, Carbon, and Nitrogen as Indicators of Trophic Level and Fish Migration in the Lower Mackenzie River Basin, Canada
Authors: Hesslein R. H. , Capel M. J. , Fox D. E. , Hallard K. A.
Published: April 2009

Stable isotopes of sulfur, carbon, and nitrogen were used to investigate the incorporation of nutrients into food chains (fish, invertebrates, and plants) and the influence of migration on the nutritional origins of fish in two freshwater systems in the Mackenzie Delta region. Sulfur isotope analyses of fish muscle showed that broad whitefish (Coregonus nasus) in Travaillant Lake and lake whitefish (Coregonus clupeaformis) in the Kukjuktuk Creek system were migrant populations which had grown mostly on sources outside the local food base. A marine food source was indicated for the lake whitefish, while no specific source was determined for the broad whitefish. The δ15N clearly defined the trophic levels in the local food chains in both systems. Fish were in three levels in Travaillant Lake. Amphipods were in a level below the lowest fish and sediments and macrophytes were in the lowest level. The Kukjuktuk Creek fish were in two levels above a level including macrophytes, amphipods, and zooplankton. The δ13C varied widely even within single fish species local to Travaillant Lake. The δ13C did not differentiate migrants from local fish. Plants of both the C3 and C4 photosynthetic pathway were indicated by carbon isotopes.
A Critical Look at the Idea of Terminal Molt in Male Snow Crab (Chionoecetes opilio)
Authors: Dawe Earl G. , Taylor David M. , Hoenig John M. , Warren William G. , Ennis Gerald P. , Hooper Robert G. , Donaldson William E. , Paul A. J. , Paul Judy M.
Published: April 2009

Whether or not male snow crab (Chionoecetes opilio) undergo a terminal molt when they develop large chelae is reviewed. Evidence supporting terminal molt includes laboratory studies in which large-clawed animals failed to molt and field studies which failed to find large-clawed males with mouth parts indicating imminent molting. Both studies were poorly documented. The field studies were largely conducted during inappropriate seasons and molt status based on a questionable mouth part stage. There is also an unsubstantiated claim that large-clawed animals fail to form limb buds for limb regeneration during the next molt and an inconclusive study of the degeneration of the Y-organ. We present new data against terminal molt including capture of large-clawed males with internal carapaces indicating impending molts, capture of two large-clawed animals with mouth parts indicating active premolting, recovery of two tagged large-clawed animals which molted while at liberty, and that the largest small-clawed animals usually are not large enough to account (through growth in a single molt) for the largest of the large-clawed animals. Also, one large-clawed male reportedly molted in captivity. We conclude that the existence of a terminal molt in male snow crab is not proven.
Interactions with the Benthos Alter Pelagic Food Web Structure in Coastal Waters
Authors: Sullivan Barbara K. , Doering Peter H. , Oviatt Candace A. , Keller Aimee A. , Frithsen Jeffrey B.
Published: April 2009

Results from studies in experimental enclosures containing both water column and benthic communities show that the benthos has an important effect on the structure and productivity of pelagic food webs whether the system is nutrient enriched or nutrient limited. Research over a 10-yr period in 13-m3 mesocosms showed that changes in the pelagic food web were correlated with different sediment communities and with the presence or absence of a benthos. The abundance of copepods was inversely correlated with numbers of macrofauna. At both low and high nutrient levels, systems without benthos had greatly enhanced numbers of carnivorous holozooplankton including ctenophores, medusans, chaetognaths, and fish. Our observations indicate that the presence of the benthos shortens the pelagic food web.and inhibits the response of pelagic fauna to nutrient enrichment in well-mixed coastal waters. The strength of benthic–pelagic coupling, which is controlled by the amount of turbulence in the water column, may be more important to food web structure than the rate of nutrient supply and could determine which subsystem responds to eutrophication.
Epiphyton Biomass is Related to Lake Trophic Status, Depth, and Macrophyte Architecture
Authors: Lalonde Sophie , Downing John A.
Published: April 2009

The relationship between epiphyton biomass and water column total phosphorus concentration (TP) was studied in macrophyte beds in 11 lakes covering a wide range of trophic status (TP = 5.8–72.8 μg∙L−1). Phosphorus concentration was a poor predictor of epiphyton biomass when considered alone. Our data do not agree with previous studies that found that epiphyton biomass increased continuously with TP. Instead, we found a very weak, nonlinear relationship between TP and epiphyton biomass, where epiphyton biomass increased up to TP≈39 μg∙L−1, and decreased at higher TP. Season and sampling depth accounted for significantly more variation in epiphyton biomass than did TP. Epiphyton biomass increased with depth in oligotrophic lakes but decreased with depth in eutrophic lakes. Seven common species of macrophytes of differing architecture developed significantly different epiphyton biomass. Macrophytes with flexible, ribbon-like leaves supported lower epiphyton biomass than species of broad-leaved or whorled architecture. The effect of host type on epiphyton algae biomass was not, however, as great as the influence of environmental variables.
Swimming Speed and Swimming Metabolism of Atlantic Cod (Gadus morhua) in Relation to Available Food: A Laboratory Study
Authors: Björnsson Björn
Published: April 2009

A laboratory study was performed on how young Atlantic cod (Gadus morhua) regulate their swimming speed according to available food. A circular tank 15 m in diameter was divided into six sectors, each containing two cod ranging in length from 29 to 42 cm. Live fish 5 cm long on average were used as prey. For the first 48 d food intake was changed every 1 or 2 wk equally for all six groups. During the last 31 d each group received different amounts of food. The mean swimming speed was highest (0.6 bl/s) when food intake was about half the maximum intake and lowest (0.2 bl/s) when food was unlimited or not available. Swimming metabolism was related to food intake in a similar way, but with a larger difference between the most active (50 mg O2∙kg−1∙h−1) and the least active group (10 mg O2∙kg−1∙h−1). Maximum sustained swimming metabolism was estimated to be about 0.6 times the standard metabolism. The estimated energetic cost of swimming as a percentage of energy obtained from the food decreased with food intake from 24% at maintenance ration to 2% at maximum food intake. On a log–log plot swimming speed decreased linearly with time after encounter of prey.
Changes in Behaviour of Atlantic Halibut (Hippoglossus hippoglossus) and Turbot (Scophthalmus maximus) Yolk-Sac Larvae Induced by Bacterial Infections
Authors: Skiftesvik Anne Berit , Bergh Øivind
Published: April 2009

Eggs of Atlantic halibut (Hippoglossus hippoglossus) and turbot (Scophthalmus maximus) were exposed to Flexibacter ovolyticus and pathogenic Vibrio sp. strains prior to, and during hatching. Activity, buoyancy and mortality of the yolk sac larvae were monitored from hatching until time of first feeding. The halibut larvae showed reduced activity and increased mortality in response to the challenge of bacteria, compared to uninfected control groups. In addition, the infected halibut larvae showed increased specific density compared to the uninfected larvae. These responses were not found for turbot. However, turbot larvae infected with Vibrio anguillarum had lower activity than larvae infected with F. ovolyticus. The reduced activity of halibut larvae occurred 1–2 weeks prior to the increased mortality, allowing infections to be detected at an early stage. The results suggest that the behaviour of fish larvae is influenced by bacterial infection.
Biochemical Indicators of Oxidative Stress in Fish from Polluted Littoral Areas
Authors: Rodríguez-Ariza A. , Peinado J. , Pueyo C. , López-Barea J.
Published: April 2009

Several biochemical parameters have been analyzed in the livers offish from south Atlantic Spanish littoral areas exhibiting different pollution levels. Mugil sp. (grey mullet) from the Huelva Estuary contained higher concentrations of metals, such as Fe and Cu, than those from a reference area (Cádiz Bay). Similarly, sediments from Huelva showed high concentrations of polyaromatic hydrocarbons, polychlorinated biphenyls, and pesticides. The contaminated animals were subjected to oxidative stress, as indicated by their oxidized glutathione redox status, but showed low malondialdehyde and lipohydroperoxide levels. A battery of antioxidant enzymes increased simultaneously in contaminated fishes, including glutathione peroxidase, superoxide dismutase, catalase, glucose-6-P dehydrogenase, and glutathione reductase. These data suggest that contaminated fish were well protected from oxidative stress. Highly significant increases were also observed in cytochrome P-450-associated ethoxyresorufin-O-deethylase activity, and soluble and membrane-bound glutathione-S-transferase, in response to the high levels of organic xenobiotics. We propose that antioxidant enzymes and glutathione-S-transferase might be useful tools for the biomonitoring of environmental pollution.
Influence of Calcium Concentrations on Cadmium Uptake by the Freshwater Mussel Ellptio complanata
Authors: Wang Y. , Evans R. D.
Published: April 2009

The effect of calcium ions on the uptake of cadmium by the freshwater mussel Ellptio complanata was studied in controlled laboratory experiments. Radioactive 45Ca and 109Cd were used as tracers. The experiments were designed to minimize geochemical differences between treatments so that the physiological interactions of the two ions could be studied. Uptake of Cd was correlated with concentration of Cd in the experimental tanks. However, the concentrations of Ca also had a strong impact on uptake rates. When uptake of Cd was expressed as a function of the molar ratio of Cd to Ca, greater than 96% of the variation could be explained.
Biology of the Pacific Pomfret (Brama japonica) in the North Pacific Ocean
Authors: Pearcy William G. , Fisher Joseph P. , Yoklavich Mary M.
Published: April 2009

Abundances of Pacific pomfret (Brama japonica), an epipelagic fish of the North Pacific Ocean, were estimated from gillnet catches during the summers of 1978–1989. Two size modes were common: small pomfret <1 yr old, and large fish ages 1–6. Large and small fish moved northward as temperatures increased, but large fish migrated farther north, often into the cool, low-salinity waters of the Central Subarctic Pacific. Lengths of small fish were positively correlated with latitude and negatively correlated with summer surface temperature. Interannual variations in the latitude of catches correlated with surface temperatures. Large catches were made in the eastern Gulf of Alaska (51–55°N) but modes of small pomfret were absent here, and large fish were rare at these latitudes farther to the west. Pomfret grow rapidly during their first two years of life. They are pectoral fin swimmers that swim continuously. They prey largely on gonatid squids in the region of the Subarctic Current in the Gulf of Alaska during summer. No evidence was found for aggregations on a scale ≤1 km. Differences in the incidence of tapeworm, spawning seasons, and size distributions suggest the possibility of discrete populations in the North Pacific Ocean.
Natural Hybridization between Arctic Char (Salvelinus alpinus) and Lake Trout (S. namaycush) in the Canadian Arctic
Authors: Wilson Chris C. , Hebert Paul D.N.
Published: April 2009

Natural interspecific hybrids between lake trout (Salvelinus namaycush) and Arctic char (S. alpinus) ranged in frequency from 1.8 to 6.8% in four of eleven lakes containing both species on the northern Melville Peninsula, N.W.T., and were also detected at several other sites across the Canadian Arctic. Hybrids were heterozygous for each of seven diagnostic allozyme loci between S. alpinus and S. namaycush, and were morphologically intermediate between the parental species. Restriction endonuclease analysis of mitochondrial DNA revealed that all but one of the hybrids had S. namaycush as their maternal parent. Resampling of two lakes where hybrids were detected revealed low levels of bidirectional nuclear introgression between the two species and limited transfer of S. namaycush mtDNA into S. alpinus.
Size Spectra of Benthic Communities in Laurentian Streams
Authors: Cattaneo Antonella
Published: April 2009

The size spectra of benthic invertebrates in streams appear to differ from those reported in planktonic systems, but could reflect the narrow taxonomic scope of previous studies. When algae, protozoans, and invertebrates growing on rocks in three Laurentian streams (Québec) were grouped in logarithmically increasing size classes, patterns in the distribution of biomass were consistent over sites and dates, despite large differences in taxonomic composition. Peaks and troughs were observed in the size spectra, but the biomass of the various size classes usually lay within an order of magnitude of the mean of all classes. The slopes of the normalized size spectra were always shallower than −1 (median = −0.91) indicating a slight biomass increase in the larger size classes. Strongly peaked spectra previously observed for stream invertebrates were smoothed by the inclusion of algae and protozoans. Comparison with size spectra described for benthic and pianktonic communities in lakes and oceans, showed remarkable similarities among habitats. These findings suggest that roughly similar biomass in logarithmic size classes is a general community pattern not restricted to the peculiarities of plankton communities. A size-based approach could be useful to simplify the description of complex stream communities.
Copper and Cadmium Binding to Fish Gills: Estimates of Metal–Gill Stability Constants and Modelling of Metal Accumulation
Authors: Playle Richard C. , Dixon D. George , Burnison Kent
Published: April 2009

Fathead minnows (Pimephales promelas) were exposed to 17 μg Cu∙L−1or 6 μg Cd∙L−1in synthetic soft water in the presence of competing ligands. Measured gill metal concentrations correlated with free metal ion concentrations, not with total metal. Langmuir isotherms were used to calculate conditional metal–gill equilibrium constants and the number of binding sites for each metal. Log KCu-gillwas estimated to be 7.4 and the number of Cu binding sites on a set of gills (70 mg, wet weight) was ~2 × 10−10mol (~30 nmol∙g wet weight−1). Log KCd-gillwas ~8.6, and the number of Cd binding sites on minnow gills was ~2 × 10−10mol (~2 nmol∙g wet weight−1). Stability constants for H+and Ca interactions at metal–gill binding sites and for metal interactions with dissolved organic carbon (DOC) were estimated using these metal–gill constants. All stability constants were entered into the MSNEQL+aquatic chemistry program, to predict metal accumulation on fish gills using metal, DOC, and Ca concentrations, and water pH. Calculated metal accumulation on gills correlated well with measured gill metal concentrations and with LC50values. Our approach of inserting biological data into an aquatic chemistry program is useful for modelling and predicting metal accumulation on gills and therefore toxicity to fish.
Pelagic Food Web Structure in Acidic Adirondack Mountain, New York, Lakes of Varying Humic Content
Authors: Havens Karl E.
Published: April 2009

Pelagic food web models were constructed for 28 acidic (pH < 5.0) Adirondack Mountain lakes, and multiple regression analyses were done to quantify relationships between abiotic variables (DOC, monomeric Al, total P, and H+ concentrations and lake area) and three food web attributes (number of species, number of links, and links per species) Regression models contained log DOC and H+ as significant predictors of food web structure. The models explained over 35% of the variation in species, links and links per species; most of the variation was explained by log DOC. Species, links and links per species increased as DOC increased from <2 to roughly 4 mg∙L−1. At higher DOC levels, the food web attributes reached plateaus at 35 species, 120 links, and 4 links per species. The results support the view that in acidic lakes, DOC ameliorates the toxic effects of Al, so that above a saturating DOC level of approximately 4 mg∙L−1, Al-sensitive biota can exist in acid waters. Hence, food webs of high DOC acid lakes are larger and more complex than their low DOC counterparts.
Toxic Metals in Pilot Whales (Globicephala melaena) from Standings in 1986 and 1990 on Cape Cod, Massachusetts
Authors: Meador J. P. , Varanasi U. , Robisch P. A. , Chan S-L
Published: April 2009

Concentrations of As, Cd, Cu, Hg, Pb, and Se were measured in 17 adult and 8 fetal pilot whales (Globicephala melaena). Total Hg and Se both occurred in very high concentrations in liver and kidney and in liver were significantly correlated with animal length (and each other) which indicates bioaccumulation over time. Methyl mercury, as a percentage of total Hg, varied inversely with total Hg indicating demethylation was occurring; a one-to-one molar association of Hg and Se was found which is believed to provide protection against Hg toxicity. Arsenic concentrations were relatively low, but Cd concentrations were consistently very high in adult kidney. Lead in adult liver was also correlated with animal length indicating long term bioaccumulation. All non-essential elements were found in critical fetal tissues which indicates maternal transfer occurred. Cadmium in fetal kidney was over 30 times higher than either brain or liver, indicating early differential accumulation and supporting maternal transfer. Matched pairs of mother and fetus liver indicated no correlation of elements, which may due to the temporal nature of bioaccumulation and the immobility of some elements. These results were compared to other mammalian studies to evaluate the toxicological implications of observed tissue concentrations.
Composition and Sedimentation of Aquatic Pigments Associated with Deep Plankton in Lakes
Authors: Hurley James P. , Garrison Paul J.
Published: April 2009

High Performance Liquid Chromatography (HPLC) pigment techniques were applied to study planktonic pigment composition and sedimentation in four Wisconsin (USA) lakes. In each lake, deep blooms of phytoplankton overlaid phototrophic sulfur bacteria in the region of the oxic-anoxic interface. Chlorophyll a and bacteriochtorophyll (a, d, and e) were observed as indicators of phytoplankton and phototrophic sulfur bacteria, respectively. Major taxonomic classes of phytoplankton were further resolved based on carotenoid signatures. In contrast to three oligo-mesotrophic Wisconsin lakes in which deep phytoplankton were comprised of dinoflagellates (indicated by the carotenoids peridinin, diadinoxanthin), cryptophytes (alloxanthin), and chrysophytes (fucoxanthin), the deep phytoplankton community in mesotrophic Mirror Lake was dominated by blue-green algae (oscillaxanthin, myxoxanthophyll, zeaxanthin, and echinenone). Deep planktonic production strongly influenced sedimentation of algal pigments and obscured the relationship between apparent water quality and sedimentary pigment deposition.
Recruitment Distributions Revisited
Authors: Fogarty Michael J.
Published: April 2009

Recruitment variability is a striking feature of the dynamics of many marine fish populations. Shelton (1992. Can J. Fish. Aquat. Sci. 49: 1754–1761) suggested that consideration of the survival probabilities of individuals or groups of individuals is the most appropriate strategy for modeling recruitment variability. A fundamental distinction can be made between environmental and demographic stochasticity. Here, environmental stochasticity refers to time-dependent variation in vital rates caused by environmental fluctuations. Demographic stochasticity is due to chance variation in the integer number of births and deaths in a population with time-invariant vital rates. The underlying basis for the simulations conducted by Shelton is consistent with the concept of demographic stochasticity. For large effective cohort size, these results converge to the deterministic case. Shelton's basic approach can be formalized using well-known results for a pure-death stochastic process. This derivation clarifies the importance of discrete processes for this class of models. Models of demographic stochasticity may be most useful for certain elasmobranch and marine mammal populations, while those incorporating environmental stochasticity may be more appropriate for many marine teleost and invertebrate populations. The critical distinction is between time-varying and time-invariant processes.
On Recruitment and Distribution of Atlantic Cod (Gadus morhua) off Newfoundland
Authors: deYoung B. , Rose G. A.
Published: April 2009

The Atlantic cod (Gadus morhua) populations located off Labrador and Northeastern Newfoundland (NAFO areas 2G–3L) have recently declined to the lowest levels of abundance on record. These "northern" cod have historically comprised several geographically recognizable populations with independent migratory life cycles on the shelf from the Grand Banks to Labrador. A reappraisal of past and recent work suggests that fundamental changes have taken place in the population dynamics of these cod during the past several decades. We focus on two key elements: distribution and recruitment. Distributions have become more southerly and recruitment failures prevail. We argue that these features are related and that northerly spawning and warm ocean conditions are prerequisites for strong recruitment. Cold ocean temperatures are associated with southerly distributions and poor recruitment. We propose the "right site" hypothesis, that egg and larval retention and survival are spatially dependent and that in cold years, spawning tends to occur at southerly locations where larval retention will be poor. We make several testable predictions: regeneration of the northern populations will occur slowly at time scales of decades, regeneration of southern populations will occur more quickly given warming conditions, and the 1991–93 year classes will be poor because of southerly distributions.
Inventaire préliminaire d'acariens (Acari : Hydryphantidae et Arrenuridae) ectoparasites de moustiques (Diptera : Culicidae) du lac Boivin, Granby, Québec
Authors: Leprince D. J.
Published: April 2009

In 1977, more than 11 000 mosquitoes were collected at Boivin Lake, Granby, and examined for ectoparasitic water mites. Mosquitoes of the genera Aedes, Anopheles, Culex, and Mansonia were parasitized by water mites of the families Hydryphantidae and (or) Arrenuridae. There are 11 new host records presented in this paper. Mosquitoes were found parasitized by two different species of mites on six occasions.
A redescription of Aporchis continuus McCauley and Pratt 1960 (Trematoda: Echinostomatidae) with new host and geographic records
Authors: Hoberg Eric P.
Published: April 2009

Aporchis continuus McCauley and Pratt 1960, (Trematoda: Echinostomatidae) is redescribed. It is reported for the first time from the glaucous-winged gull, Larus glaucescens Naumann, and the black-legged kittiwake, Rissa tridactyla pollicaris Ridgway, in the Gulf of Alaska.