bluuebunny/crossref_metadata_2025 huggingface dataset:
Body Size and Feeding Ecology as Alternatives to Taxonomy for the Study of Limnetic Zooplankton Community Structure
Authors: Sprules W. Gary , Holtby L. Blair
Published: April 2011

Three different characterizations of limnetic zooplankton communities from lakes of the Bruce Peninsula, Ontario are compared with respect to their usefulness in limnological studies: a conventional taxonomic one, one based on the body size and feeding ecology of the organisms, and one based on image analysis of the particle size spectrum. In comparison with the taxonomic characterization, the ecological and image analysis characterizations reflect zooplankton community features which are more closely related to the efficiency and nature of energy flow through pelagic ecosystems. Furthermore, it is demonstrated that these features have stronger statistical relations to morphometric and hydrological properties of lakes. The ecological and image analyses are thus not only more useful in studies seeking to make predictions about lake function from lake type but actually require less time, money and expertise in the acquisition of zooplankton data. In comparisons of zooplankton communities from the disparate faunal regions of the Bruce Peninsula, Ontario and southeast Asia, particularly Sri Lanka, more useful functional insights emerge from a body size-feeding ecology characterization than from a taxonomically based one. Key words: community structure, image analysis, Bruce Peninsula, tropical zooplankton, zoogeography, multivariate analysis
Differential CO2 and O2 Benthic Community Metabolism in a Soft-Water Lake
Authors: Rich P. H.
Published: April 2011

CO2 accumulation is greater than O2 removal in the hypolimnion of Dunham Pond (zmax = 4.5 m) during the summer, and in the whole lake during winter stratification. During much of stratification no free oxygen and less than 1% surface light exist below 2.5 m. Despite low light and on-going accumulation of CO2 during stratification, CO2 uptake is found in situ in sediment surface incubations at 3.5 m. The CO2 uptake is associated with an epipelic mat of blue-green algae apparently undergoing anaerobic photosynthesis. Thus, anaerobic photosynthesis and anaerobic respiration appear to be going on simultaneously in the hypolimnion. Respiratory quotients are conventionally thought of as a characteristic of metabolism imparted by the nature of the biochemical substrate being oxidized by an organism. Respiratory quotients of mixed communities of aerobes and anaerobes depend more upon the nature of the oxidizing agent being reduced. The degree to which a community RQ is greater than expected (about 0.85) describes the amount of metabolism for which oxygen is not (yet) the terminal electron acceptor. Excess oxidation of carbon creates ambient reducing power potentially available for bacterial (anaerobic) photosynthesis and chemolithotrophy. Key words: lake, respiratory quotient, oxygen deficit, carbon cycle, benthic respiration, eddy diffusion, heat budget, soft-water, detritus, ecosystem energetics
Recovery and Concentration of Infectious Pancreatic Necrosis (IPN) Virus in Water
Authors: Grinnell Brian , Leong J. C.
Published: April 2011

Infectious pancreatic necrosis (IPN) virus was concentrated from water by a polymer two-phase method using polyethylene glycol and dextran sulfate. A concentration of over 100-fold was attained. By this method as little as one infectious virus particle per litre of water can be detected. Key words: infectious pancreatic necrosis virus, virus concentration, diplornavirus, salmonids, polyethylene glycol
Zooplankton Population Dynamics and Diaptomus Production in Waldsea Lake, a Saline Meromictic Lake in Saskatchewan
Authors: Swift Michael C. , Hammer U. Theodore
Published: April 2011

Zooplankton population dynamics were monitored in meromictic saline Waldsea Lake, Saskatchewan, during 1974–75. The dominant zooplankton species were Diaptomus connexus, Brachionus plicatilis, Hexarthra fennica, and Daphnia similis. Diaptomus had a 1-yr life cycle. Overwintered late-stage copepodites molted into adults in May and June and were followed by sequential peaks in numbers of eggs, nauplii, and copepodites. The estimated annual production of this species was 0.6 g dry weight∙m−2 or 0.3 g C∙m−2. About 4% of the annual planktonic primary production would be required to support Diaptomus if it is 10% efficient. The standing crop of Brachionus and Hexarthra was highest in the spring and declined thereafter; Hexarthra was more abundant than Brachionus. The standing crop of Daphnia was much lower than that of either rotifer and showed a spring and fall peak in abundance. Differences in vertical distribution were present among the zooplankton species but no real vertical migrations were observed. Key words: Diaptomus connexus, zooplankton, population dynamics, production, saline meromictic lake
Comparison of Fisheries Control Systems That Utilize Catch and Effort Data
Authors: Hilborn Ray
Published: April 2011

The relative merits of various methods for estimating the parameters of the Schaefer model from catch and effort data and of controlling the fishery are compared by simulation techniques. Estimation procedures compared are the linear and nonlinear methods for the discretized Schaefer model and Schnute's method for the continuous form of the Schaefer model. The control systems compared are feedback effort limitation, quota control for fixed escapement policies, and application of equilibrium effort. It is found that all estimation systems frequently fail to provide reasonable estimates of the Schaefer model and will produce poor catches, especially when managing long-lived, low productivity species. These estimation problems are most severe when the catch and effort data series begins after the stock has been heavily exploited. The failure of the estimation systems is primarily due to insufficient contrasts in the two independent variables of the multiple regression used for estimation, effort and catch per effort. The need for alternative policies that will explore the effort, catch per effort space is discussed. Application of the equilibrium effort may frequently be preferred to a fixed escapement policy; average catch may not be reduced, and variability in catch is much lower. Quota regulation is dangerous when the stock is heavily exploited and the biological parameters of the stock uncertain; at other times the quota method produces results comparable with effort limitation. Key words: Schaefer model, feedback control, catch and effort, fisheries regulation, adaptive control
Statistical Comparisons of Several Growth Curves of the von Bertalanffy Type
Authors: Misra R. K.
Published: April 2011

A computer program in Fortran was developed for 1BM/370 (i) to fit a growth curve of the von Bertalanffy type to each of several samples (a sample comprises several age-groups, with one or more observations in a group) and then, (ii) to compare statistically the fitted curves and their individual parameters. In fitting the curve to a sample (i) age-groups need not he equally spaced, (ii) group frequencies need not be equal, (iii) within-group variances need not be equal, and (iv) individual observations need not have equal weights. Additional features of the program are described. An example is provided.Key words: computer program, von Bertalanffy growth, growth comparisons
Size–Maturity Relationships and Related Observations in Newfoundland Populations of the Lobster (Homarus americanus)
Authors: Ennis G. P.
Published: April 2011

Female maturity ogives for five Newfoundland populations of the lobster (Homarus americanus) gave 50% maturities ranging from 71- to 76-mm carapace length. Sizes at which distinct inflections (indicating onset of maturity) and asymptotes (indicating 100% mature) are present in the abdomen width/carapace length ratio vs. carapace length relationships coincide with the smallest ovigerous and largest immature specimens, respectively, observed in those particular samples. Inflection in the crusher claw weight/whole weight ratio vs. carapace length relationships (used in this paper to indicate onset of maturity in males) occurred at larger sizes than inflections in the abdomen width/carapace length ratios of females.The percentage of nonovigerous females that spawn in a given year generally increases with increasing size. The highest percentage of nonovigerous females tagged with sphyrion tags prior to the spawning season that were ovigerous when recaptured 10–12 mo later was 83.8%. The percentage of ovigerous females with new shells (i.e. molted and spawned in same year) varied between areas and years and ranged from 0 to 38.5% of the total number of ovigerous females in fall samples. The percentage of ovigerous females in samples also varied between areas and years and ranged from 2.6 to 30.4% of the total number of females greater than the size at 50% maturity. In general a greater percentage of females was ovigerous at sizes between the size at 50% maturity and 80 mm (largest subcommercial size) than at commercial sizes.In a sample of nonovigerous females, the size range at which 50% were fertilized (76–80 mm) coincided closely with the size at 50% maturity (75 mm) for the area.At subcommercial sizes (< 81 mm) the sexes were approximately equally represented in fall trap-caught samples but females heavily outnumbered males in diver-caught samples taken over the same period. At commercial sizes, however, males heavily outnumbered females in the trap-caught samples while in diver-caught samples the sexes were equally represented.Key words: lobster (Homarus americanus), maturity ogives, maturity indices, percent ovigerous, sex ratios
Isolation of Myxosoma cerebralis (Whirling Disease) Spores from Infected Fish by use of a Physical Separation Technique
Authors: Kozel Thomas R. , Lott Marley , Taylor Robert
Published: April 2011

Immiscible, liquid, two-phase systems are produced when aqueous solutions of dextran and of polyethylene glycol are mixed above certain concentrations. This phase system was used to isolate Myxosoma cerebralis spores from infected fish tissue. Myxosoma cerebralis partitioned into the polyethylene-glycol-rich upper phase, whereas the tissue debris partitioned into the dextran-rich lower phase. Myxosoma cerebralis spores partitioned into the upper phase, regardless of the electrostatic potential in the phase system, indicating that isolation of M. cerebralis was unrelated to surface charge, which suggests that relative to fish tissue, the surface of the spore is highly hydrophobic. The technique is useful for detection of small numbers of spores from populations of infected fish; however, the greatest value of the technique is the isolation of spores for biochemical and immunologic studies that are unmodified by the relatively harsh techniques usually used.Key words: Myxosoma cerebralis spores, Myxosoma spore isolation techniques, polymer aqueous two-phase systems
Parr–Smolt Transformation of Yearling Atlantic Salmon (Salmo salar) at Several Rearing Temperatures
Authors: Johnston C. E. , Saunders R. L.
Published: April 2011

Six different rearing conditions were used to study the effect of temperature on seasonal changes in growth, condition factor, body silvering, body moisture and lipid content, salinity tolerance, and gill Na–K-ATPase activities of laboratory and pond-reared yearling Atlantic salmon (Salmo salar). Growth during the winter was greatest at the highest rearing temperature (16 °C) whereas those under simulated natural conditions grew slowest. Increasing temperatures in the spring stimulated growth more than constant temperature. Based on increased salinity tolerance, elevated ATPase activity, and growth in salt water, smolt development proceeded at all temperatures up to 16 °C. More smolts were produced in the high thermal regimes resulting in the best growth and the largest proportion of fish reaching smolt size. Unlike some Pacific salmonids, Atlantic salmon develop smolt status at temperatures as high as 16 °C. Yearling smolts can be produced at elevated temperatures and the use of thermal effluents for this purpose is promising.Key words: smoltification, smolt criteria, salinity tolerance, ATPase activity, rearing temperatures, elevated thermal regimes, thermal effluent, Salmo salar
Rainbow Trout (Salmo gairdneri) and Cutthroat Trout (S. clarki) Interactions in Coastal British Columbia Lakes
Authors: Nilsson Nils-Arvid , Northcote Thomas G.
Published: April 2011

Food, size, and growth of 17 allopatric and 10 sympatric lake populations of rainbow trout (Salmo gairdneri) and cutthroat trout (S. clarki) were compared as well as their aggressive behavior during feeding in experimental tanks. In allopatry, rainbow trout fed extensively on benthic, midwater, and surface prey. Allopatric cutthroat utilized mostly midwater prey but in contrast with rainbow trout also fish (Cottus, Gasterosteus) when available. In sympatry, rainbow trout exploited mainly limnetic surface and midwater prey whereas cutthroat trout utilized more littoral prey and were much more piscivorous in feeding. Allopatric rainbow attained a greater average and maximum size (length, weight) than allopatric cutthroat whereas in sympatric populations cutthroat were clearly larger than rainbow. Growth (size at specific ages) usually was higher for rainbow compared with cutthroat trout in allopatric populations but just the reverse in sympatric populations. When held as matched pairs in aquaria, rainbow consistently were more aggressive than cutthroat trout and displayed different patterns of threat as well as means of prey capture. Differences in feeding and growth in sympatry may result from interactive segregation, the more pronounced aggressiveness of rainbow promoting higher growth in cutthroat trout.Key words: rainbow trout, cutthroat trout, feeding, growth, habitat, aggressive behavior, feeding behavior, interactive segregation
Interspecific Associations in a Woodland Stream
Authors: Reice Seth R.
Published: April 2011

Patterns of association of benthic macroinvertebrates were examined within a riffle of New Hope Creek, North Carolina, USA. The 16 most common species were tested for cooccurrences. Chi-square contingency tests on simultaneous presence and absence of two species at a time were performed. The strength of the association and its direction were determined for significantly associated species pairs using the V statistic. The patterns of association among 120 species pairs are presented for each of three mineral substrate types (cobbles, pebbles, and gravel) and leaf packs (5 g of Cornus florida leaves) attached to them. These data were collected over a 3-mo period.The results show that significant interspecific association on a given substrate was found for 18.3% or less of the species pairs. The species which strongly associated on one substrate type differed from those associating on another substrate. The presence or absence of leaf packs on a mineral substrate patch, which did not affect most species densities, did affect the cooccurrence patterns among species. The presence of leaf packs reduced the number of significantly associated species pairs on all substrates. In all cases in mineral substrates, negative associations were rare. The proportion of negative associations approximated what one would predict by chance alone. This suggests that competition may not be an important factor in stream communities.This work presents a different approach to the analysis of lotic communities. It suggests several hypotheses about community structure in streams. It reaffirms that substratum type is a major governing factor in stream community structure and dynamics.Key words: benthic macroinvertebrates, community organization, competition, interspecific association, leaf pack, patchiness, predation, stream, substrate
Piscivority by Stocked Brown Trout (Salmo trutta) and Its Impact on the Nongame Fish Community of Bottom Creek, Virginia
Authors: Garman Greg C. , Nielsen Larry A.
Published: April 2011

The magnitude of fish consumption by brown trout (Salmo trutta) was assessed by experimentally stocking large (> 280 mm) and small (< 280 mm) brown trout in separate sections of a Virginia stream. Large brown trout ate five species of fish consistently during the May–November, 1979, experimental period; by November, every trout stomach examined contained fish remains. Small trout rarely ate fish. Effects of fish consumption were apparent in trout growth and in abundance of prey species. Large trout grew 9.4% in length and 21.3% in weight, whereas small trout grew 4.5% in length and 4.7% in weight. Abundance of the major prey species, torrent sucker (Moxostoma rhothoecum), decreased between April and October in the stream section containing large trout, but remained constant in a comparable reference section; estimates of total consumption of torrent suckers by brown trout accounted for a large portion of the decrease in abundance. Predation on torrent suckers was selective for smaller individuals. The field experiment indicates that stocking large-sized brown trout may enhance growth and survival of brown trout, but that standing crops of nongame species are likely to decline.Key words: brown trout, nongame fishes, predation, stocking strategy, stream ecology
Effect of Growth Rate and Size of Fish on Rate of Intoxication by Waterfoorne Lead
Authors: Hodson Peter V. , Dixon D. George , Spry Douglas J. , Whittle D. M. , Sprague John B.
Published: April 2011

Three experiments were undertaken to test the null hypotheses that increasing fish size and growth rate do not increase the rate of intoxication of fish by lead. The first experiment demonstrated that there were no significant correlations between weight of fish and either whole-body or blood lead concentrations in feral lake trout (Salvelinus namaycush). The whole-body lead concentration of rainbow smelt (Osmerus mordax) was, however, negatively correlated to wet weight.During the second experiment, an 8-d laboratory exposure of rainbow trout (Salmo gairdneri) to 100 μg/L of total waterborne lead caused a greater uptake of lead by opercular bone in small fish than in larger fish. No relationship was apparent between fish weight and uptake of lead by blood.Chronic exposure of juvenile rainbow trout to lead results in the development of black tails, a symptom of neurotoxicity. The final experiment related the incidence and prevalence of black tails to size and growth rate (ration level) of juvenile rainbow trout chronically exposed to 543 μg/L of total waterborne lead starting with the sac-fry stage. At weights below a common threshold size of 1.5–2.5 g, no black tails occurred; above this threshold the incidence of black tails was a function of growth rate, i.e. the rate at which fish reached the threshold size. The prevalence of black tails was always less in slowly growing fish.These experiments demonstrated that the rate of intoxication by lead, as indicated by uptake rates into tissues and the incidence and prevalence of a symptom of neurotoxicity, did not increase with fish size, but rather with growth rate.Key words: fish, toxicity, lead, fish size, growth rate, neurotoxicity, uptake
Otoliths of Chinook Salmon (Oncorhynchus tshawytscha): Daily Growth Increments and Factors Influencing Their Production
Authors: Neilson John D. , Geen Glen H.
Published: April 2011

The effects of photoperiod, feeding frequency, and water temperature on formation of otolith daily growth increments in juvenile chinook salmon (Oncorhynchus tshawytscha) were examined. Feeding frequency influenced both increment number and width, whereas photoperiod and temperature affected only increment width. Fish fed once/24 h produced one increment every 24 h on average, while fish fed 4 times/24 h produced more than one increment every 24 h. Wider increments were produced in fish exposed to warmer water (11 °C) or 24 h of darkness. The ratio of otolith size to fish size remained constant throughout and between the photoperiod, temperature, and feeding frequency experiments, regardless of the number or width of increments produced. Although otolith growth is isometric with respect to increase in fish length under these experimental regimes, otolith microstructure will differ in fish of the same size reared under different environmental conditions. An understanding of factors affecting otolith increment production is required before increment number and width can be used to assess growth rates.Key words: otolith, daily, growth increments, chinook salmon
A Model for Predicting Pacific Herring (Clupea harengus pallasi) Spawn Density from Diver Observations
Authors: Schweigert J. F. , Fournier D.
Published: April 2011

A series of mathematical models were examined to predict the density of Pacific herring (Clupea harengus pallasi) spawn in 1-m2 quadrats from diver observations of the dominant vegetation substrate, the number of layers of eggs on the vegetation, and the density of the vegetation in the quadrat (percent cover). The most appropriate model was chosen statistically and used to make predictions for comparison with egg counts. Outliers were identified and if a plausible biological interpretation was found, these were deleted from the data series. The model provides an efficient and precise means for estimating herring spawn density from diver observations and could be incorporated into a sampling survey design for estimating spawn abundance for stock assessment.Key words: mathematical model, Pacific herring, Clupea harengus pallasi; spawn density, stock assessment
Le Panache du Saguenay
Authors: Lebel J. , Pelletier E. , Bergeron M. , Belzile N. , Marquis G.
Published: April 2011

The large difference between the alkalinity of the fresh waters of the St. Lawrence River (1.475 mmol∙kg−1) and the Saguenay River (0.134 mmol∙kg−1) was used to locate the region on the St. Lawrence estuary which is under the influence of the Saguenay River. This method has the advantage over classical measurements such as salinity and temperature that it is independent of the upwelling of deep water in this region. Data was obtained in the St. Lawrence estuary near the mouth of the Saguenay fjord using a network of 33 stations at slack low tide and 23 stations at slack high tide. The results show that, at low tide, Saguenay water forms a plume which extends more than 10 km from the mouth of the fjord into the estuary. At high tide the plume is restricted to the surface layer as the Saguenay waters are pushed back into the fjord.
Behavior of Crayfish in Water Currents: Hydrodynamics of Eight Species with Reference to Their Distribution Patterns in Southern Ontario
Authors: Maude Stephen H. , Williams D. Dudley
Published: April 2011

When exposed to increases in current speed in a laboratory stream tank, crayfish altered their body posture to counteract the effects of drag, thus enabling them to maintain station at higher current speeds. Using a beam-type drag balance, direct drag measurements were made on live adults of eight Ontario crayfish species over a range of current speeds. The species were then ranked according to their relative streamlining efficiencies as indexed by these drag measurement data. The station-holding abilities of the species were compared by determining the mean slip speed of each species on a roughened Plexiglas substrate. There were significant differences in slip speed, the species falling into three groups. The first contained only Cambarus robustus, which had a mean slip speed of 49.7 cm∙s−1. The fast-water species, Orconectes rusticus, C. bartoni, and O. propinquus, all had mean slip speeds between 30 and 40 cm∙s−1. The remaining species, O. obscurus, O. virilis, C. fodiens, and O. immunis had mean slip speeds of less than 30 cm∙s−1. The crayfish species' substrate texture preferences were also tested. Cambarus bartoni was the only species which preferred a gravel to a mud substrate. Orconectes obscurus, O. virilis, C. fodiens, and O. immunis all preferred a mud substrate. We suggest that the superior streamlining capabilities of C. bartoni and O. rusticus may help to explain the occurrence of these species in fast-flowing rivers, as well as the latter's rapid and widespread expansion in Ontario since its introduction. On the basis of relative station-holding abilities, O. rusticus should continue to be more successful at expanding its range in southern Ontario via lotic waterways than the other introduced species, O. obscurus.Key words: crayfish, drag, station-holding ability, streamlining, drag coefficient, hydrodynamics, posture, slip speed, substrate, distribution
Relationship Between Body-Lead Concentration of Mysis relicta and Sediment-Lead Concentration in Kootenay Lake, B.C.
Authors: Evans R. D. , Lasenby D. C.
Published: April 2011

The potentially important mechanism of biological mobilization of lead from lake sediments was investigated. Lead concentrations of the crustacean Mysis relicta from Kootenay Lake, determined using atomic absorption spectrophotometry, were compared to published lead sediment concentrations from the same sites. There is a strong correlation between sediment-lead concentration and Mysis-lead concentration. This correlation may indicate that Mysis can accumulate lead from the sediment and return it to the open water.Key words: Mysis relicta, lead, heavy metal contamination, contaminated sediments.
Effect of Increased Dietary Fiber on the Growth of Rainbow Trout (Salmo gairdneri)
Authors: Hilton J. W. , Atkinson J. L. , Slinger S. J.
Published: April 2011

Juvenile rainbow trout (Salmo gairdneri) reared for 12 wk on different levels of dietary fiber showed a significant growth depression at levels of 10 and 20% alpha-floc (α-cellulose). The trout adapted to increased dietary fiber by increasing feed consumption, gastric evacuation time, and possibly by increasing the stomach volume and/or distensibility. The dry matter digestion coefficients of the diets declined as the fiber level increased, indicating that the digestibility of α-cellulose was not significantly different from zero. No effect of increased dietary fiber (alpha-floc) was detected on the liver glycogen levels, liver–body weight ratios, hemoglobin, hematocrit, plasma glucose, and plasma protein levels or the kidney, liver, and carcass levels of copper, iron, and zinc. We conclude that dietary fiber levels for rainbow trout should be less than 10% of the diet.Key words: rainbow trout, dietary fiber, maximum fiber level, fiber digestibility
Potentiated Sulfonamide Therapy of Enteric Redmouth Disease
Authors: Bullock G. L. , Maestrone G. , Starliper C. , Schill B.
Published: April 2011

Effective control of enteric redmouth disease was obtained during artificial infection of rainbow trout (Salmo gairdneri) and in natural outbreaks in rainbow trout and chinook salmon (Oncorhynchus tshawytscha) with a potentiated sulfonamide, Ro5-O037, a combination of five parts sulfadimethoxine and one part ormetoprim. Treatment was given at the rate of 50 mg/kg of fish for 5 d.Key words: potentiated sulfonamide, enteric redmouth, therapy, salmonids
The Effect of Parameter Uncertainties in an Age–Length Relationship upon Estimating the Age Composition of Catches
Authors: Majkowski J. , Hampton J.
Published: April 2011

A simple, but frequently applied, procedure for decomposing fish length frequencies into age-classes is considered. This decomposition consists of converting fish lengths into ages using an age–length relationship. A method for assessing the effect of parameter uncertainties in this relationship upon estimates of the age composition of catches is presented. It is assumed that the parameter uncertainties can be described by probability distributions. Our aim is to determine probability distributions of age composition estimates resulting from these uncertainties. This is done using a stochastic sensitivity analysis technique involving Monte Carlo simulations and/or a first-order theory if such a theory is valid in the case under consideration. The method is illustrated by its application to data from the southern bluefin tuna (Thunnus maccoyii) fishery. It is found that simulated (Monte Carlo) catch estimates for age-classes 3 (fish at age 2–3 yr) to 13 (fish at age 12–13 yr) are normally distributed. The coefficients of variation of these estimates are less than 12%. Simulated catch estimates for age-classes 1, 2, and 14–20 deviate considerably from normality and their ranges bounded by the 2.5 and 97.5 percentiles are extremely wide; they include values different by up to 810% from the best deterministic catch estimates.Key words: catch, age composition, uncertainties, sensitivity analysis, Monte Carlo simulations, southern bluefin tuna
Evidence of Acidification of Some Nova Scotian Rivers and Its Impact on Atlantic Salmon, Salmo solar
Authors: Watt W. D. , Scott C. D. , White W. J.
Published: April 2011

River pH's in Nova Scotia are closely related to geology, and seasonal pH variation is well correlated with river discharge rates. In the geologically sensitive areas (granite and metamorphic rocks), river pH's have fallen significantly over the past 27 yr at an apparent average rate of 0.017 pH units/year. Concomitant with this decrease are a decline in [Formula: see text] concentrations and increases in Al+++ and [Formula: see text]. On average, 73% of the increase in acid is attributable to increased [Formula: see text]. Changes in Na+, K+, Ca++, and Mg++ concentrations were not significant. In rivers presently at mean annual pH's < 4.7, the Atlantic salmon (Salmo salar) runs have disappeared and are presumed extinct. Rivers in the pH range 4.7–5.0 show a decline in salmon angling returns of 2.8%/yr, beginning about 1954, and low densities of juvenile salmon. Rivers presently of pH > 5.0 generally have normal juvenile densities and show no significant trend in angling returns.
Silicon Contamination in Diatom Nutrient Enrichment Experiments
Authors: Tarapchak Stephen J. , Slavens David R. , Quigley Michael A. , Tarapchak Judith S.
Published: April 2011

Large amounts of biologically available silicon (Si) were released into solution from the walls of Pyrex glass reagent bottles and Erlenmeyer flasks during nutrient bioassay experiments using Lake Michigan water. Photosynthetic rates in short-term (4–7 h) incubations and diatom growth rates and maximum yields in long-term incubations (~7 d) were affected by these extraneous Si supplies. The results of conventional nutrient enrichment bioassays performed in low-Si environments can be seriously biased unless Si contamination from glass incubation containers is avoided.
Lipid Quantification of Freshwater Invertebrates: Method Modification for Microquantitation
Authors: Herbes Stephen E. , Allen Carol P.
Published: April 2011

To facilitate determination of lipid content of freshwater invertebrates for bioaccumulation studies, the chloroform–methanol extraction procedure of Bligh and Dyer was modified for microquantitation. Following extraction, lipids were quantified by use of a micro-balance. Recoveries of representative neutral and polar lipids averaged 88.3% with a mean coefficient of variation of 8.6%. Tests with freshwater benthic and pelagic invertebrates demonstrated the applicability of the procedure to samples as small as several milligrams wet weight with a mean coefficient of variation of 11.6%.
Size of Flocs Suspended in Delaware Bay
Authors: Gibbs Ronald J. , Konwar Lohit , Terchunian Aram
Published: April 2011

This study extended from the Delaware River down the Delaware Bay into the upper Delaware Bay. The suspended material concentration in the lower Delaware River and upper Delaware Bay was determined by filtration, and the size and nature of flocs were determined by optical microscope. The principal turbidity maximum, at a salinity of 1‰ was composed of the largest flocs (up to 130 μm diameter), and sizes found in the water column decreased progressively down the Bay. This maximum was probably related to the formation of flocs. A second turbidity maximum, not related to floc formation or resuspension, may have occurred at a salinity of 5‰.Key words: flocs, turbidity maximum, Delaware Bay
Les flux de sels nutritifs dans l'estuaire de la Seine (France); rôle et importance du bouchon vaseux au cours du mélange estuarien
Authors: Guillaud Jean-François
Published: April 2011

Dissolved nutrient loadings from the Seine River as it enters the Seine Estuary were examined for the period 1976–79; these are directly related to river flow, except for more constant phosphate loading. Mean annual inputs of dissolved inorganic nutrients attain 37 600 t/yr for silica, 10 300 t/yr for phosphorus and 66 000 t/yr for nitrogen. Nutrients samples were also collected along the estuary during March 1978 and March and September 1979; results show that in the estuary the dissolved nutrients are generally mixed in a conservative way; a few exceptions can be noticed — addition of silicate to the bottom water during high river flow periods and production of ammonia and nitrites during the summer months. Results also indicate that particulate phosphorus and particulate organic nitrogen can be trapped within the area of the turbidity maximum but this process affects only a small fraction of the total inputs of nutrients from the river. Finally it is suggested that high turbidity levels and rapid flushing time are two significant factors limiting the primary production and the removal of dissolved nutrients within the estuary.
Stable Carbon Isotope Studies on the Pecks Cove Mudflat Ecosystem in the Cumberland Basin, Bay of Fundy
Authors: Schwinghamer Peter , Tan Francis C. , Gordon Jr. Donald C.
Published: April 2011

Ratios of stable carbon isotopes (δ 13C) have been measured in components of an intertidal mudflat ecosystem located near the head of the Bay of Fundy. Special attention was given to the isolation and analysis of carbon source materials including phytoplankton, benthic algae, marsh grass (Spartina alterniflora), size-fractionated detritus, and "mineral" sediment. Bulk sediment and suspended matter were also analyzed. For most of the year the two major primary producers, Spartina and benthic diatoms (dominated by Gyrosigma spp.), had similar δ 13C values (−13 to −14‰). Some Spartina detritus, presumably "fresh" material, also had similar δ 13C values. It was therefore imposible to estimate the relative importance of carbon from these sources to the nutrition of consumer organisms. Zooplankton, benthic-feeding fish, and benthic fauna had δ 13C values mostly in the range of −12 to −15‰, suggesting that live Spartina, "fresh" detritus, and benthic diatoms could be major carbon sources. Phytoplankton and other isotopically light carbon sources including "aged" detritus, bulk and "mineral" sediment, do not appear to be major carbon sources for mudflat organisms. We found Spartina detritus to be abundant both in sediments and suspended matter outside the salt marshes, but the δ 13C values of most of the detritus were much lighter (−17 to −20‰) than those of live Spartina. The mechanism of this isotopic alteration is not known and we were not able to demonstrate it clearly in laboratory experiments. Although the δ 13C method has helped to assess the relative importance of some isotopically distinct carbon sources, we were unable to detect any 13C enrichment in various trophic levels of mudflat organisms and benthic-feeding fish.Key words: stable carbon isotope ratio, detritus, decomposition, mudflat ecosystem, Pecks Cove, Bay of Fundy
Sediment Mobility in the Severn Estuary and its Influence upon the Distribution of Shorebirds
Authors: Ferns Peter N.
Published: April 2011

In December 1979, superficial muddy sediments were eroded from considerable areas of the intertidal zone of the southern shores of the Severn Estuary during a period of prolonged westerly gales. Shorebird numbers at the affected sites showed an immediate decline as a result of the depletion of their mud-dwelling invertebrate food resources, and there was a corresponding increase in the numbers of birds along the northern shores of the estuary where no such erosion had occurred. Detailed monthly counts of 14 species of shorebirds in the Severn Estuary during 1971/72 to 1975/76 were therefore examined to determine if any of the previously unexplained anomalies in their distribution coincided with weather conditions likely to have given rise to similar losses of intertidal sediment. Although the 5 yr in question were relatively calm compared with the 1960s, there were five individual months during which the mean hourly windspeeds exceeded 13 m∙s−1 on more than 25 occasions. During these periods, the average deviations in the numbers of Shelduck, Grey Plover, Dunlin, Curlew, and Redshank from those predicted by a log-linear model taking seasonal, annual, and regional trends into account, were particularly large. Furthermore, the sites which were involved in each case were those that were directly exposed to the prevailing winds during the windiest periods of the month in question. High winds, by propagating waves that mobilize fine sediments in the intertidal zone, are thus implicated as a significant factor influencing the distribution of some shorebirds.Key words: Severn Estuary, sediment mobility, shorebird distribution, wading birds, local migration
Development of an Ecosystem Model of a Turbid Estuary
Authors: Joint I. R.
Published: April 2011

This paper describes the development of those aspects of the whole ecosystem model, GEMBASE, which are most influenced by water turbidity. Mean values of surface turbidity, determined for a coarse grid of the Bristol Channel, were found to be highly correlated with tidal range and log10 14-d mean river flow. Parameters derived from multiple regressions of these variables were used to obtain realistic simulations of surface turbidity for an 8-yr period from 1972 to 1980; simulated extinction depths derived from turbidity simulations were also realistic. Results of GEMBASE are discussed for phytoplankton and suspension feeding benthos, the two components of the ecosystem most affected by suspended solids concentrations. Simulations of phytoplankton biomass were obtained which compared well with field data. However, results for suspension feeding benthos were less good and showed slight increases in biomass from year to year which have not been found in the Bristol Channel; possible reasons for this are discussed.Key words: Bristol Channel, ecosystem modeling, turbidity, extinction depth, phytoplankton, suspension feeding macrofauna
Input of Pelagic Tar into the Northwest Atlantic from the Gulf Loop Current: Chemical Characterization and its Relationship to Weathered IXTOC-I Oil
Authors: Vleet E. S. Van , Sackett W. M. , Weber Jr. F. F. , Reinhardt S. B.
Published: April 2011

Pelagic tar concentrations have been measured for samples collected monthly in the eastern Gulf of Mexico over a one year period. Analyses of the pelagic tar included gravimetric, isotopic (δ13C) and molecular (gas chromatographic) characterization of the total, aliphatic, and aromatic fractions. The concentrations of pelagic tar ranged from 0 to 26.5 mg∙m−2 of toluene extractable material, with an average of 1.60 mg∙m−2 in the offshore neuston tows and 0.05 mg∙m−2 in neuston tows taken on the west Florida continental shelf. Oblique tows to 100 m depth averaged 0.01 mg∙m−2. δ13CPDB values for the total tar in each tow averaged −27.2‰ with the aliphatic fractions averaging −27.5‰ and the aromatic fractions averaging −27.0‰. Approximately 40% of the tar samples showed a bimodal n-alkane distribution characteristic of crude oil sludge. Based upon an average annual Loop Current discharge of 28 × 106 m3∙s−1 through the Florida Straits, it is estimated that approximately 7000 t of pelagic tar are discharged annually from the Gulf of Mexico into the North Atlantic. Approximately half of this may be brought into the Gulf from the Caribbean via the Loop Current, while the remainder appears to originate in the Gulf of Mexico. Possible origins of the floating tar include input from the Caribbean Sea through the Yucatan Strait, production and transportation operations in the Gulf of Mexico, Mississippi River discharge, subsurface oil seeps, and major accidental discharges. Large amounts of oil from the IXTOC-I well blowout do not appear to have impinged on coastal waters of Florida.
Annual Input of Petroleum Hydrocarbons to the Coastal Environment via Urban Runoff
Authors: Hoffman Eva J. , Mills Gary L. , Latimer James S. , Quinn James G.
Published: April 2011

To compile an oil pollution budget for Narragansett Bay, Rhode Island, urban runoff samples were collected at four storm drains each serving a different land use. Three to six storm events with different rainfall amounts were monitored at each drain, and the samples were analyzed for petroleum hydrocarbons using glass capillary gas chromatography. The hydrocarbon (HC) load for each storm (mass HC/area) varied systematically with total rainfall, and the storm event load–rainfall relationship was different for each land use. Using rainfall records, the load for each storm was calculated and then summed to predict an annual input rate of hydrocarbons to receiving waters in terms of mass HC/area for each land use. Industrial and interstate highway land gave the highest loads followed by commercial and residential land, respectively. Finally, an estimate of the total hydrocarbon annual input to Narragansett Bay via urban runoff was compiled using land use data from cities and towns in the drainage basin.
Natural Weathering of Oil in Marine Sediments: Tissue Contamination and Growth of the Littleneck Clam. Protothaca staminea
Authors: Anderson J. W. , Riley R. G. , Kiesser S. L. , Thomas B. L. , Fellingham G. W.
Published: April 2011

Three groups (90 per group) of small (<30 mm) littleneck clams, Protothaca staminea, were placed in the intertidal environment of Sequim Bay, Washington for 1 yr to measure the effects of oiled sediment on growth and tissue contamination. Detailed glass capillary gas chromatographic analyses of initial and final sediment samples and tissues were used to describe the fate of specific oil components in the sediment, with depth, and the uptake by the clams. Concentrations of oil in sediments receiving a top layer (3 cm) of highly contaminated sediment reached background levels after 1 yr, while sediment mixed to depth (10 cm) with oil still contained measurable contamination at the 5–10 cm depth. The pattern of specific hydrocarbon loss is in agreement with results of spill studies, molecular weight relationships, and biodegradation data. The ratios of tissue concentrations to final sediment concentrations for phenanthrenes, alkylnaphthalenes, and dibenzothiophenes were all between 0.16 and 0.18. This suggests that the sulfur-containing compounds were not preferentially retained in tissues. Statistical analyses of 31–48 individually measured and marked clams (per group) showed that growth in oil-treated sediment was significantly (P < 0.001) slower than in clean sediment. In addition, oil mixed into sediment (10 cm) produced greater tissue contamination and more reduction in growth (P < 0.01) than a layer (3 cm) of oiled sediment.
Hepatic Microsomal Monooxygenase Activity and the Biotransformation of Hydrocarbons in Deep Benthic Fish from the Western North Atlantic
Authors: Stegeman John J.
Published: April 2011

Microsomal electron transfer components cytochrome P-450, cytochrome b5, NADPH-cytochrome c (P-450) reductase activity and NADH-cytochrome c (b5) reductase activity were present in hepatic microsomes from several species of deep-sea fishes sampled between 1400 and 3200 m deep in the North Atlantic. The specific content of cytochrome P-450 varied among the species but was within the range observed for shallow-water fishes. The specific content was the highest in the deepest sampled species, Coryphaenoides armatus (0.25 nmol/mg microsomal protein). Hepatic microsomes from this species also exhibited little or no putative cytochrome P-420 whose presence suggested some degradation of cytochrome P-450 in the other species. Ethoxyresorufin O-deethylase and benzo[a]pyrene hydroxylase activities were high in several species, particularly Coryphaenoides armatus. Strong inhibition of benzo[a]pyrene hydroxylase activity by α-naphthoflavone was demonstrated in some species. The data suggest that some hepatic cytochrome P-450 in Coryphaenoides armatus (and possibly Coryphaenoides leptolepis and Bathysaurus mollis) but not in Coryphaenoides rupestris or Antimora rostrata may have been induced by environmental chemicals in the deep sea. As in other teleost fishes, Coryphaenoides hepatic microsomes metabolized benzo[a]pyrene in vitro with a high specificity for the benzo-ring, suggesting the capacity to form mutagenic derivatives of some hydrocarbons efficiently.
The Distribution of Selected Trace Metals in United Kingdom Shelf Waters and the North Atlantic
Authors: Jones P. G. W. , Jefferies D. F.
Published: April 2011

The distribution of dissolved and suspended particulate Cd, Cu, Mn, Ni, and Zn was surveyed in the water of the North Atlantic and adjacent European shelf seas. The exercise was conducted by the Lowestoft Fisheries Laboratory and was part of a broad program coordinated by the International Council for the Exploration of the Sea (ICES) Working Groups concerned with pollution baseline and monitoring studies. The distribution of dissolved metals was enriched in coastal waters up to an order of magnitude compared with the offshore shelf seas. Both anthropogenic and natural sources of metal were considered in relation to the elevated inshore values. The suspended particulate phase of trace metals present in coastal and shelf waters was often a significant proportion (between 5 and 70%) of the total metal present. Oceanic values of dissolved metal were comparable with concentrations measured in offshore shelf seas. Deep vertical profiles of trace metals resembled the distribution of nutrient salts, thus indicating biological mobilization. The validity of all data was discussed in relation to current sampling and analytical techniques. The degree of sampling and analytical sophistication employed must relate to the basic requirements of the exercise.
Remobilization of Metals from Polluted Marine Sediments
Authors: Hunt Carlton D. , Smith Deborah L.
Published: April 2011

The transition metals Cu, Pb, Fe, Mn, and Cd were examined to estimate short- and long-term release rates from highly contaminated sediments and to compare this release with present metal flux into an ecosystem. The concentration of Cu and Pb increased in the water column over contaminated marine sediments when these sediments were isolated from metal and organic carbon sources and held in large (13 m3) marine microcosms. During the summer and early fall, Cu concentrations increased by a factor of 3 relative to the concentration in microcosms containing slightly polluted and uncontaminated sediments. Mass balance calculations indicate that 840 and 21 μmol∙m−2∙yr−1 Cu and Pb, respectively, were mobilized and exported from the microcosms with highly contaminated sediments, while less-contaminated sediments lost 120 μmol Cu∙m−2∙yr−1. Iron and Mn were not exported from the microcosms. In the absence of high sedimentation rates and high bioturbation rates, the diffusive loss of Cu and Pb may be sufficient to return the upper 1 cm of sediment to background levels in 44 and 400 yr, respectively. This remobilization is a small percentage of current inputs to Narragansett Bay.