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1

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Improved Piezometer Construction and Sampling Techniques to Determine Pore Water Chemistry in Aquitards (1999)

Wassenaar, Leonard I. ; Hendry, M. Jim

Oxford, UK : Blackwell Publishing Ltd

Ground water 37 (1999), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: Due to extremely slow water recovery rates in aquitards and high contamination potential from sealing materials, installation of piezometers in aquitards for geochemical studies requires specialized construction and careful sampling techniques. Few methods have been demonstrated for obtaining representative ground water samples for geochemical parameters from piezometers in aquitards. Here we implement and evaluate an aquitard piezometer installation and ground water chemistry sampling strategy and show that the use of an inert gas pocket in piezometer construction can be used to delay seal contamination for at least three years and avoid oxygenation and disturbance of downhole redox conditions. Major ion analyses did not change appreciably through the standing water columns in the aquitard piezometers over time; however, reliable measurements of typically unstable geochemical parameters (dissolved oxygen, pH, and oxidation-reduction potential) were best obtained using downhole, in situ instrumentation, provided there was at least 2 to 10 m of standing water in the piezometer.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.1999.tb01143.x

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A stable carbon and nitrogen isotope study of lake food webs in Canada’s Boreal Plain (2001)

Beaudoin, Catherine P. ; Prepas, Ellie E. ; Tonn, William M. ; [et al.]

Oxford UK : Blackwell Science Ltd

Freshwater biology 46 (2001), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Stable carbon and nitrogen isotope and fish stomach content analyses were used to investigate food webs in five relatively undisturbed lakes on the Boreal Plain of Canada. Stable isotope analysis was also used to determine the importance of external and internal carbon sources.2. Overlap in the carbon and nitrogen signatures of primary producers made it difficult to determine unambiguously the feeding habits of many invertebrates. However, isotope analysis suggested that external carbon inputs were detectable in the aquatic food chains of the one lake with a short water residence time («1 year). In the other four lakes, with water residence times ≥1 year, autochthonous carbon was the only detectable carbon source in the food webs.3. Food webs in these lakes spanned a range of four to five trophic levels. Both invertebrates and fish appeared to eat a variety of food, often feeding at more than one trophic level.4. With the exception of one lake (SPH20), top predators in these lakes, northern pike (Esox lucius) and fathead minnows (Pimephales promelas), occupied similar trophic positions despite large differences in body size and trophic morphology. In SPH20, where there were two additional fish species, pike occupied a higher trophic position. However, all the top predators in each lake appeared to be omnivores and generalists.5. The prevalence of omnivory and the apparent generalist feeding habits of fish in these lakes suggest that organisms are flexible in their feeding habits and that these food webs will be resilient to disturbance.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00688.x

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Stable Isotopes (δ18O, δ2H) of Pore Waters in Clay-Rich Aquitards: A Comparison and Evaluation of Measurement Techniques (2001)

Kelln, Chris J. ; Wassenaar, Leonard I. ; Hendry, M. Jim

Oxford, UK : Blackwell Publishing Ltd

Ground water monitoring & remediation 21 (2001), S. 0

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ISSN: 1745-6592

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: Pore water collected from piezometers installed in a thick clay-rich till were used to compare and evaluate four techniques for obtaining δD and δ18O values in these media. The techniques included mechanical squeezing, centrifugation, azeotropic distillation, and a direct soil-water equilibration technique. Direct CO2-core equilibration yielded sufficiently accurate and reproducible δ18O results of pore water in clay-rich tills. In addition, this method eliminated the need for labor-intensive complete extraction of water from the geologic media. Mechanical squeezing and centrifugation produced results similar to direct equilibration. However, both of these methods exhibited a greater degree of variability and were laborious and more time consuming. Small differences in δ18O values between piezometer water and equilibrated, squeezed, and centhfuged samples suggested that each method collected different fractions of the clay-water reservoir. Although these subtle differences were not conclusive, they did suggest the presence of weakly bound water and highlighted the difference between these three techniques for determining the stable isotopic composition of pore water in clay-rich aquitards. Azeotropic distillation produced a high level of discrepancy in δD andδ18O results compared to the other methods. Incomplete extraction was considered the most probable cause of this error. The results of this study suggested that direct equilibration is the best method for determining detailed δD and δ18O values of pore water in clay-rich aquitards.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6592.2001.tb00306.x

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4

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Linking breeding and wintering grounds of neotropical migrant songbirds using stable hydrogen isotopic analysis of feathers (1996)

Hobson, K. A. ; Wassenaar, Leonard I.

Springer

Oecologia 109 (1996), S. 142-148

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ISSN: 1432-1939

Keywords: Key words Deuterium ; Neotropical migrant ; Stable isotopes ; Songbird feathers ; Diet

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Recent studies have shown that stable hydrogen isotope ratios (δD) in the tissues of animals often correlate with δD of local precipitation. Here we examined the relationship between δD in feathers and growing season precipitation for neotropical migrant songbirds breeding over a continent-wide isotopic gradient. δD values were determined on feathers of 140 individuals of 6 species of wild insectivorous forest songbirds (Setophaga ruticilla, Empidonax minimus, Vermivora peregrinus, Catharus ustulatus, Seiurus aurocapillus, Hylocichla mustelina) taken from 14 breeding locations across North America. The δD of feathers was strongly correlated with the δD of growing season precipitation at breeding sites across North America. As feather hydrogen is metabolically inert after growth, this relationship was then used to assess the breeding origins of wintering migrants. Deuterium values of feathers from 64 individuals representing 5 species of migrants (Helmitheros vermivorus, Wilsonia citrina, Hylocichla mustelina, Dumetella carolinensis, Seirus aurocapillus) at a wintering site in Guatemala were consistent with those predicted from the known breeding ranges of these species. This study demonstrates hydrogen isotopes may become a powerful tool for linking breeding and wintering grounds of neotropical migrant songbirds, as well as other migratory species moving between isotopically distinct regions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004420050068

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5

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Individual specialization and trophic adaptability of northern pike (Esox lucius): an isotope and dietary analysis (1999)

Beaudoin, Catherine P. ; Tonn, William M. ; Prepas, Ellie E. ; [et al.]

Springer

Oecologia 120 (1999), S. 386-396

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ISSN: 1432-1939

Keywords: Key wordsEsox lucius ; Individual variation ; Stable isotope analysis ; Stomach content analysis ; Trophic adaptability

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Northern pike (Esox lucius) are often considered to be specialist piscivores, but under some circumstances will continue to eat invertebrates as adults. To examine effects of fish assemblage composition on the trophic ecology of pike, we combined stable isotope analysis (SIA) of carbon and nitrogen and stomach content analysis (SCA) on pike from five lakes in northern Alberta, three of which contain only pike (“pike-only”) and two that also contain yellow perch (Perca flavescens) or white sucker (Catostomus commersoni) (“pike-other”). Fish were more important as prey and empty stomachs, which often characterize piscivores, were significantly more frequent in pike-other than in pike-only lakes. However, even though invertebrates were more important for pike in pike-only lakes, SIA and SCA indicated that invertebrates were also an important component of pike diets in pike-other lakes. SIA and SCA also revealed considerable intrapopulation variation in trophic ecology, with individuals in some populations differing by as much as two trophic levels. Comparisons of stomach contents and isotope signatures of the same fish suggested that within these variable populations, specialization on invertebrates or fish was a long-term trait of some individuals. SIA indicated that trophic position increased and diets shifted to a greater importance of littoral prey as pike grew in pike-only lakes, but not in lakes with other fish present. Trophic adaptability in northern pike is expressed at both the population level, where the trophic ecology is sensitive to differences in prey regimes, and at the organismal level, in the form of intrapopulation variation and individual specialization.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004420050871

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6

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Stable isotopes (δD and δ13C) are geographic indicators of natal origins of monarch butterflies in eastern North America (1999)

Hobson, Keith A. ; Wassenaar, Leonard I. ; Taylor, Orley R.

Springer

Oecologia 120 (1999), S. 397-404

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ISSN: 1432-1939

Keywords: Key words Monarch butterfly ; Migration ; Natal origins ; Isotopic gradients

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Wing membranes of laboratory and field-reared monarch butterflies (Danaus plexippus) were analyzed for their stable-hydrogen (δD) and carbon (δ13C) isotope ratios to determine whether this technique could be used to identify their natal origins. We hypothesized that the hydrogen isotopic composition of monarch butterfly wing keratin would reflect the hydrogen isotope patterns of rainfall in areas of natal origin where wings were formed. Monarchs were reared in the laboratory on milkweed plants (Asclepias sp.) grown with water of known deuterium content, and, with the assistance of volunteers, on native milkweeds throughout eastern North America. The results show that the stable hydrogen isotopic composition of monarch butterflies is highly correlated with the isotopic composition of the milkweed host plants, which in turn corresponds closely with the long-term geographic patterns of deuterium in rainfall. Stable-carbon isotope values in milkweed host plants were similarly correlated with those values in monarch butterflies and showed a general pattern of enrichment along a southwest to northeast gradient bisecting the Great Lakes. These findings indicate that natal origins of migratory and wintering monarchs in Mexico can be inferred from the combined δD and δ13C isotopic signatures in their wings. This relationship establishes that analysis of hydrogen and carbon isotopes can be used to answer questions concerning the biology of migratory monarch butterflies and provides a new approach to tracking similar migratory movements of other organisms.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004420050872

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