Leah I. Bendell-Young

The structure of the manganese oxide on the sheath of the bacterium Leptothrix discophora : An XAFS study

Abstract In natural waters, manganese oxides (MnOx) are important in mediating the bioavailability of trace metals such as Ni, Cu, Zn, Cd, and Pb, as these metals readily adsorb to the MnOx surface. Manganese from a variety of anthropogenic sources usually enters the aquatic environment in dissolved form as Mn2+. It is subsequently oxidized under oxic and neutral (pH = 6-7) conditions. Often this oxidation is catalyzed by bacteria, such as Leptothrix discophora, as part of their natural metabolic process. Mn K-edge X-ray Absorption Fine Structure Spectroscopy (XAFS) was used to investigate the local structure of manganese oxide on the sheath produced by the bacterium Leptothrix discophora SP-6. The features observed in the near edge region of the Mn K-edge spectrum indicate the presence of three oxidation states of manganese: Mn2+, Mn3+, and Mn4+. Fitting the experimental XAFS data identifies the bacterial MnOx as being composed of single-layer microcrystals with layers similar to those occurring in Na-birnessite. Some MnO6 octahedra might lie outside the layer plane, sharing corners with those in the layer plane. X-ray diffraction results for the same samples are consistent with the single-layer structure.

SEASONAL TRENDS IN POPULATION DENSITY, DISTRIBUTION, AND MOVEMENT OF AMERICAN DIPPERS WITHIN A WATERSHED OF SOUTHWESTERN BRITISH COLUMBIA, CANADA

Abstract American Dippers concentrate on low-elevation streams during fall and winter in many parts of their range; however the breeding origin relative to the wintering location is poorly understood. Our objectives were to identify seasonal changes in the density and distribution of American Dippers, to classify the migratory behavior of the local population, and to determine the origin of winter migrants within a coastal watershed of British Columbia, Canada. During 1999–2002, we color banded 522 dippers and radio-tagged 14 in the Chilliwack River watershed. Using mark-resighting techniques, we identified peak densities on the main river during early November (9.8 ± 1.4 [SE] birds per stream km), which was nearly 5 times higher than in early July (2.1 ± 0.3 birds per stream km). The watersheds total population size, estimated from November surveys, was 429 ± 64 [SE] dippers in 1999, 682 ± 79 in 2000, 697 ± 123 in 2001, and 550 ± 72 in 2002. The majority (79– 90%) of the dipper population seasonally migrated, primarily moving from the main river in fall and winter to the higher-elevation tributaries in spring. The remaining dippers (10– 16%) remained resident on the main river year-round. Migrants showed a high degree of winter site fidelity with 67% returning to the same site on the Chilliwack River for 2 or more years. Given the populations defined structure and predictable seasonal movements, this study has implications for applying American Dipper populations as indicators of water and habitat quality in North American watersheds. Tendencias Estacionales en Densidad Poblacional, Distribución y Movimiento de Cinclus mexicanus en una Cuenca del Sudoeste de la Columbia Británica, Canadá Resumen. Cinclus mexicanus se concentra en ríos ubicados a baja elevación en muchas partes de su rango durante el otoño y el invierno; sin embargo, se conoce poco sobre la relación entre el sitio originario de reproducción y la localización durante el invierno. Nuestros objetivos fueron identificar los cambios estacionales en la densidad y la distribución de C. mexicanus, clasificar el comportamiento migratorio de la población local y determinar el origen de los migrantes invernales en una cuenca costera de la Columbia Británica, Canadá. Entre 1999 y 2002 anillamos con bandas de color 522 individuos de C. mexicanus y seguimos con radio-telemetría 14 individuos en la cuenca del Río Chilliwack. Usando técnicas de marcado y re-avistamiento, identificamos densidades pico en el río principal durante principios de noviembre (9.8 ± 1.4 [EE] aves por km de río), lo que fue casi 5 veces más alto que a principios de julio (2.1 ± 0.3 aves por km de río). El tamaño total de la población de la cuenca, estimado a partir de los censos de noviembre, fue 429 ± 64 [EE] aves en 1999, 682 ± 79 en 2000, 697 ± 123 en 2001 y 550 ± 72 en 2002. La mayoría (79–90%) de la población de C. mexicanus migró estacionalmente, moviéndose principalmente desde el río principal en el otoño y el invierno a los tributarios de mayor elevación en la primavera. Los individuos restantes (10–16%) permanecieron como residentes en el río principal durante todo el año. Los migrantes mostraron un alto grado de fidelidad a los sitios de invierno, con un 67% de los individuos retornando al mismo sitio en el Río Chilliwack por 2 años o más. Dada la estructura definida de la población y los movimientos estacionales predecibles, este estudio señala que las poblaciones de C. mexicanus pueden ser usadas como indicadores de la calidad del agua y del hábitat en las cuencas de América del Norte.

Impact of oil-sands based wetlands on the growth of mallard (Anas platyrhynchos) ducklings.

Identifying the potential effects of industrially formed wetlands on waterfowl populations is important for assessing the suitability of such wetlands in industrial reclamation strategies. Mallard ducklings were held in situ on two industrially formed wetlands and one reference wetland in northern Alberta, Canada. Duckling mass and skeletal size were measured at regular intervals over 33 d, and blood was collected to investigate the analysis of plasma metabolites (triglyceride and glycerol) as an indicator of physiological condition. In repeated-measures analysis of variance (ANOVA), multivariate ANOVA, and subsequent multiple-comparisons tests, body mass and skeletal size were significantly lower in ducklings maintained on the industrial wetland after 2, 5, 9, and 13 d of exposure. In this situation, plasma metabolite analysis did not provide additional information on mass-independent condition. We conclude that if the observed differences in growth and size translate into a decreased survival of juvenile waterfowl inhabiting these wetlands, then populations of these birds in the area could be negatively affected. We emphasize the importance of field-based ecological research in toxicological studies of wildlife.

Peatland Interstitial Water Chemistry in Relation to that of Surface Pools along a Peatland Mineral Gradient

The elemental (including silica (Si), calcium (Ca), magnesium (Mg), manganese (Mn) and iron (Fe)) and nutrient composition of peatland surface pools and concentrations of Ca, Mg, Mn, and Fein peat interstitial waters and surface peat concentrations of oxides of Mn and Fe were determined for 15 peatlands sampled along a mineral gradient. Surface pool concentrations of Si wereca. ten fold less in surface pools of mineral-poor peatlands thanin the mineral rich, supporting the use of this element as an indicator of minerotrophic influence in peatlands. Principle component analysis of surface pool water chemistry parametersdifferentiated mineral-poor and moderately-poor peatlands frommineral-rich peatlands based on the concentrations of Ca, Mgand alkalinity of pools. Several lines of evidence indicated that peatland interstitial waters were important contributors to peatland alkalinity and included; (1) maximum interstitial water concentrations of Ca and Mg correlating with overlying surface pool alkalinity, (2) a negative correlation between interstitial water Ca:Mg ratios and surface pool concentrationsof Si and (3) Ca:Mg ratios of moderately-poor to mineral-poorpeatland interstitial waters approaching the Ca:Mg ratio of rainwater rather than those of bedrock. Interstitial water concentrations of dissolved Mn and Fe correlated with amountsof reducible Fe and Mn (oxides of Fe and Mn) recovered from thepeat/water interface indicating that groundwater inputs areimportant sources of these two elements to fens. As a consequence, for peatlands that are not truly ombrotrophic,groundwater inputs of Mn and Fe may interfere with interpretingpeat metal profiles thought to be due to anthropogenic inputs alone.

Metal concentrations in chrionomids in relation to peatland geochemistry

Concentrations of Zn, Cu, Al, Fe, and Mn were determined in Chironomidae (Diptera) larvae sampled from three sites within eight peatlands, located in south-central Ontario, Canada. The eight peatlands displayed a range in pH and alkalinity and were classified abiotically (i.e., chemically, hydrologically) and biotically (i.e., dominant vegetation present) as mineral-poor, moderately poor, or as mineral-rich fen. Surface peats of mineral-poor fens were distinct from those of moderately poor and mineral-rich fens; mineral-poor fens contained higher concentrations of organic matter with low concentrations of easily reducible Mn vs. the moderately poor and mineral rich fens. A one-way nested ANOVA indicated that chironomid metal concentrations were peatland dependent (P<0.05). To determine if differences in chironomid metal concentrations among the peatlands could be related to peat geochemistry, an R2 MAX procedure using peat geochemistry as the independent variable and chironomid metal concentrations as the dependent variable was applied. Peat geochemistry was defined as concentrations of peat organic matter, reducible Fe (Fe oxides), reducible Mn (Mn oxides) and easily reducible metal (where metal = Zn, Cu, Al, Mn and Fe), and reducible metal and organically bound metal. Chironomids from mineralrich peatlands, i.e., peatlands low in organic matter with high concentrations of reducible Mn and Fe or easily extractable metal contained greater concentrations of Zn, Mn, and Fe vs. chironomids sampled from mineral poor peatlands, i.e., peatlands with high concentrations of peat organic matter and low concentrations of reducible Mn or easily extractable metal. In contrast, Cu concentrations were greatest in larvae sampled from mineral-poor vs. mineral-rich peatlands. Aluminum larvae concentrations were independent of peat geochemistry. We suggest that bioavailability of metals such as Zn, Fe, and Mn will be greater to invertebrates inhabiting mineral rich vs. mineral poor fens, whereas greater chironomid Cu concentrations will be found in chironomids sampled from mineral poor fens. Differences in metal availability to invertebrates among peatland types has important implications when comparing the impact of contaminant transfer to higher trophic levels among different types of peatlands.

Uptake of 109Cd from sediments by the bivalves Macoma balthica and Protothaca staminea

Abstract This study (1) compared the relative importance of suspended particulate matter (SPM) and deposited sediment (DS) as a source of cadmium exposure to two sediment ingesting bivalves, and (2) determined the importance of feeding behaviour on cadmium uptake from SPM and DS by comparing metal uptake from ingested sediments by a facultative and an obligate filter-feeder. Two types of sediment, deposited (DS) and suspended (SPM) sediments were sampled from the Fraser River Estuary and geochemically characterized with respect to amounts of easily reducible manganese and reducible iron (manganese and iron oxides respectively), organic matter, and amounts of cadmium associated with each of the three components. Sediments were radiolabeled with 109 Cd, with the labelled sediments then fed to Macoma balthica and Protothaca staminea , a facultative filter-feeder and an obligate filter-feeder respectively. Amounts of radiotracer accumulated by the bivalves from the two types of sediment over an 8-day period were then assessed. The geochemistry of DS was distinct from that of SPM with DS containing almost half the concentrations of oxides of manganese and iron as compared to SPM. Natural cadmium was recovered primarily from the easily reducible (associated with oxides of manganese) followed by the reducible (associated with oxides of iron) sediment component, for both SPM and DS. In contrast, 109 Cd was recovered from the reducible fraction, followed by the easily reducible fraction from the two types of sediment. No natural cadmium or 109 Cd was recovered from the organic component of either sediment. For both bivalves, uptake of 109 Cd from sediment as compared to water accounted for ca. 80% of accumulated radiotracer. Uptake of 109 Cd from DS was significantly greater than from SPM, most notably for P. staminea . For M. balthica , the amount of accumulated 109 Cd was best explained by the degree of isotope desorption from DS. In contrast, 109 Cd accumulation by P. staminea was best described by its feeding behaviour. Metal accumulation by sediment-ingesting organisms is not simply related to sediment metal concentrations but will also depend on the strength of association of the metal within the sediment (for facultative feeders), and the feeding behaviour of the bivalve. 109 Cd partitioning in DS and SPM did not parallel the field partitioning of cadmium which precluded our objective of assessing the relative importance of SPM and DS as a source of cadmium to facultative filter-feeders. To elucidate the role of complex sediment geochemistry in influencing metal availability to sediment ingesting organisms, further study is needed on ways to either label or spike natural complex sediments such that the speciation achieved under laboratory conditions is that which is observed in the field.

Base cation composition of pore water, peat and pool water of fifteen Ontario peatlands: Implications for peatland acidification

Base cation (Ca, Mg, Na, K) concentrations in surface waters, pore waters and surface peats were determined along a mineral-poor to mineral-rich fen gradient for 15 south-central Ontario peatlands. Surface waters of the peatlands ranged in pH and alkalinity from 4.5 to 6.3 and 0 to 181μeqL−1, respectively. Both surface water and pore water Ca and Mg concentrations followed the expected decrease along the mineral-rich to poor-fen gradient. Surface water concentrations of Ca and Mg were significantly lower in the mineral-poor versus the moderately-poor and mineral-rich fens (P<0.05, ANOVA). Pore water concentrations of base cations were 3–5 fold less in mineral-poor vs. mineral-rich fens. In contrast to surface and pore waters, peat base cation concentrations did not decrease along the mineral-rich to mineral-poor fen gradient. Surface peat base cation concentrations were also independent of pore water cation concentrations, and local bedrock geology. Relative concentrations of base cations in surface peats of all peatlands were best described by the exchangeable cation capacity of the surrounding soils.

Contrasting the geochemistry of oxic sediments across ecosystems: a synthesis

Abstract The geochemistry of oxic sediments was contrasted across a range of Canadian aquatic ecosystems; 7 freshwater lakes, (3 circumneutral and 4 acidic), 15 peatlands (5 mineral-rich, 5 moderately-poor and 5 mineral-poor), 9 wetlands (3 oligosaline, 3 mesosaline and 3 euryhaline), an estuary (deposited and suspended sediments) and an intertidal region. Sediments were characterized by a simultaneous extraction that separated sediments into easily reducible (ER) metal (oxyhydroxides of Mn and easily reducible amorphous oxyhydroxides of Fe) and reducible (R) metal (more crystalline forms of oxyhydroxides of Fe), organic matter, and, the concentrations and partitioning of Zn, Cu and Cd associated with these 3 sediment components. Ecosystems were distinct with respect to ER Fe and organic matter [canonical variate analysis (CVA)] with 53% of among system variation in geochemistry attributed to these 2 components. Sediments of peatlands and wetlands contained greater amounts of organic matter whereas sediments of lakes, intertidal and estuarine deposited and suspended sediments were characterized by greater amounts of ER Fe. A further 21% of among system variation could be ascribed to organically bound Fe that was greater in acidic lakes and mineral-rich peatlands as compared to other systems. Concentration and partitioning of Cd within sediments was regionally dependent with 41% of among system variation (CVA) attributed to differences in ER Cd and R Cd. Cadmium from peatlands and lakes located in Ontario was recovered from all 3 sediment components whereas sediment from wetlands, the estuary and the intertidal regions of British Columbia (BC) contained no organically bound Cd with amounts recovered occurring mostly as ER Cd. Lakes and peatlands located in Ontario contained 3–5-fold total Cd as compared to ecosystems located in BC. A further 21% of among ecosystem variation was attributed to Zn partitioning. Zinc in peatland and wetland sediments occurred as R Zn as compared to lake and estuarine deposited sediments where Zn was recovered both as ER and R Zn. Total Zn was also 3–5-fold greater in sediments of systems in Ontario as compared to those sampled in BC. Concentration and partitioning of Cu was similar across all systems with Cu recovered from the organic component of sediment. The geochemistry of surficial oxic sediments with respect to ER Mn, R Fe and organic matter and the geochemical associations among these sediment components is ecosystem and region dependent. For assessing impacts of metals on sediment dwelling biota the geochemical characteristics of the system under study should first be defined.

Copper, zinc, and cadmium concentrations in Peromyscus maniculatus sampled near an abandoned copper mine

Concentrations of zinc, copper, and cadmium were determined in soil and liver, kidney, bone and stomach contents of deer mice (Peromyscus maniculatus) from two sites near an abandoned mine and one control site, on Vancouver Island, British Columbia, Canada. Soil concentrations of copper were significantly elevated at the mine and off site vs the reference site. In contrast, there was no difference in soil cadmium and zinc concentrations between the mine and reference site. Concentrations of copper, cadmium and zinc in livers of mice from the mine site were significantly elevated relative to the reference and off site locations. Cadmium kidney concentrations tended to be greater in mice from the mine versus the off site and reference site. No differences in bone cadmium, copper and zinc and, kidney copper and zinc concentrations were noted among mice from the three locations. Diet of mice from mine and off sites contained significantly greater copper concentrations than the reference population; no differences in cadmium or zinc diet concentrations in mice from the three sites were noted. Comparison of ratios of metal concentrations in diet:soil and concentrations in liver:soil suggest that for zinc and copper, soil and diet are of equal importance as a source of metal contamination to these mice. In contrast, cadmium diet:soil and cadmium liver:soil ratios were much greater than one indicative of bioconcentration of cadmium from soil to diet and from soil to liver. For assessing routes of metal exposure, in this case for deer mice inhabiting an abandoned mine site, for copper and zinc, soil will most likely be indicative of exposure conditions. In contrast, concentrations of cadmium in diet will be more representative of amounts that the animal is potentially ingesting. Of further importance is that relative to reference sites, mice inhabiting an abandoned copper mine site have significantly elevated tissue levels of copper. This is turn will provide a route of metal exposure to canivorous birds such as owls and hawks. The toxicological significance of this exposure to birds of prey has yet to be assessed adequately.

Cost of selective feeding by the blue mussel (Mytilus trossulus) as measured by respiration and ammonia excretion rates.

The metabolic cost as measured by respiration and ammonia excretion rates associated with a selective as compared to a non-selective feeding behaviour was determined for the blue mussel, Mytilus trossulus. Mussels were challenged with four environmentally relevant seston matrices of different quality and quantity, which were known to evoke either a sorting response (i.e., selective feeding) where organic-rich particles were selected over inorganic particles as compared to no sorting (i.e., non-selective) where either inorganic or organic particles were ingested by the bivalve. Seston matrices were prepared by mixing known quantities of silt and algae such that the following extent of feeding responses would occur; no pre-sorting of ingested material, (1) no algae+50 mg silt l(-1), (2) 150x10(6) cells l(-1) of algae+no silt, and, where pre-sorting of ingested material occurred, (3) 20x10(6) cells l(-1) of algae and 20 mg l(-1) of silt, and (4) 150x10(6) cells l(-1) of algae and 50 mg l (1) of silt. A control, which represented basal metabolism consisting of mussels exposed only to filtered seawater (0.45 &mgr;m), was included for a total of five treatments. Mussel respiration and ammonia excretion rates were independent of whether mussels were pre-sorting or not sorting ingested material. Of the four matrices, only rates determined for conditions of maximum seston quality and quantity where pre-sorting of the seston occurred were significantly different from control mussels (p<0.05, ANOVA). Estimates of net energy used for feeding, where net energy is total energy intake (food) minus energy expenditure (energy lost through respiration and excreta as measured by ammonia excretion rates), indicated that feeding, whether selective or non-selective required only 0.92% of net energy intake. Hence, mussels appear to be highly adapted to a dynamic food environment with negligible costs associated with the feeding process, even when significant pre-selection of organic-rich particles occurs.