The possibility of manipulating calcium (Ca2+) and potassium (K+) levels in seeds of Brassica rapa by altering parent plant nutrition and investigating the potential for increased salinity tolerance during germination, given that considerable amounts of literature imply that greater amounts of available exogenous Ca2+ and K+ can ameliorate the effects of salinity on both whole plant growth and germination, was evaluated. The investigation consisted of four growth trials. Two preliminary growth trials suggested that seed ion manipulation was possible without affecting the overall growth and vigour of the plant. After developing suitable high and low Ca2+ and K+ nutrient solutions for growth, a trial was carried out in a growth room and greenhouse, with various substrates and the seed of a certain size category was collected for subsequent ion and salinity tolerance analysis. Seed Ca2+ and K+ was significantly affected by growth substrate and nutrient solution and data showed that a significant negative regression relationship existed between seed Ca2+, K+ and Ca2+ + K+ levels and salinity tolerance. Further experimentation using hydroponic culture attempted to remove any possible effects of substrate and also to compare size categories of seed with a view to elucidating localisation of Ca2+ and K+. Seed Ca2+ was found to be significantly altered by nutrient solution in the two different sizes tested and higher Ca2+ nutrient solution was found to increase salinity tolerance in daughter seed. One significant negative regression correlation between salinity tolerance and seed K+ concentration existed in smaller seed, but disregarding seed size in a regression analysis of seed ion content and salinity tolerance, a significant negative relationship existed between seed Ca2+, K+ and Ca2++ K+. The results, especially in terms of Ca2+ nutrition, contradict much previous research that suggests increased salinity tolerance at germination can arise with the increased presence of Ca2+ and/or K+. Salinity tolerance was greater in seeds of larger size across all nutritional treatments and the smaller size range exhibited increased Ca2+ and K+ per μg seed. Ca2+ concentration in smaller seeds with greater surface area:volume ratios provided a clue to the potential localisation of Ca2+. Cross sectional staining showed that a greater proportion of seed Ca2+ may reside in the coat. This was confirmed by analysis which showed an approximate 50% split of total extractable seed Ca2+, regardless of size, between coat and embryo within a seed; the majority of which, per μg, resides in the coat. Further work looked at the relative solubility of the Ca2+ and K+ in these tissues and whole seed to look at the potential bioavailability of Ca2+ during germination from various parts of the seed. Most water soluble Ca2+ exists in the embryo and most insoluble Ca2+ exists in the coat, but coat Ca2+ was found to be ionically exchangeable and therefore bioavailable. K+ appeared mostly water soluble in embryo and coat. In line with previous whole plant research in this species, most Ca2+ is readily water soluble or ionically exchangeable in form and the possible negative effects of how increasing bioavailable Ca2+ may reduce salinity tolerance was discussed.

In Libya salinization of land and ground water is a key problem. A. saligna is one species that offers potential for growth under these conditions. Experiments were undertaken to accelerate the germination of Acacia seeds, and various pre-treatment methods were assayed. Boiling water treatment, mechanical scarification and acid improved germination and germination rate. Sowing A. saligna seeds at 30 mm depth gave greatest seedling growth from large and medium seeds whereas 20 mm was more suitable for small seeds. This study aimed to improve the establishment of Acacia saligna irrigated with saline water, plants were grown for seven weeks under greenhouse or field conditions in (Libya) either sand or soil salinized with varying applications of NaCl. Irrigation with NaCl significantly decreased plant survival and growth and concentration of Ca, Na, K, Fe and P ions in plants with 0.5 M or 1.0 M NaCl. The experiments were repeated using a naturally occurring soil amendment called ‘Zander’. Seeds of A. saligna were grown for seven weeks in both greenhouse and field trials as before but with the addition of Zander and NaCl. Zander improved plant survival and growth with salinity and increased the elements in plants (Ca, Na, K, Fe and P). Field experiments were conducted to assess the effects of saline irrigation with 1.0 M NaCl and extra water added to 0% or 10% Zander on survival and growth, consequently, seedling growth significantly decreased with increase in soil salinity. Survival and growth increased with increase in extra water. The additional irrigation water caused an increase in the uptake of Ca++ and increased the Ca++/Na+ and K+/Na+ ratio. Zander did not appear to reduce net uptake of Na+ and its transport to shoot tissues. Mg++, P, K+ and Ca++ content significantly decreased in plants in response to salinity. Possible mechanisms to avoid Na+ toxicity in A. saligna in response to salinity included increasing the supply of Ca++. Extra Ca++ applied into the medium with and without salt increased survival and growth even in the absence of Zander. Calcium increased uptake of Ca++ and increased Ca++/Na+ and K+/Na+ ratio.

Two accessions of tepary (phaseolus acutifolius Gray var. latifolius) and navy (P. vulgaris L. 'Fleetwood') beans were studied for salt tolerance at several• developmental stages. Genotypes were germinated at 0.0 through -2.5 MPa NaCl at 25°C and 35°C for nine days. Tepary accessions had higher germination percentages and rates than navy for ≤ - 2.0 MPa at 250C and ≤ - 1.5 MPa at 35°C. Fresh weights of root plus hypocotyl decreased severely with the first increment of NaCl (-0.5 MPa) for all genotypes. Fresh weight of navy was reduced more at 35°C than at 25°C. Genotypes were stressed in vermiculite-filled trays with 0.0 through -1.5 MPa NaCl for 14 days. Final growth stage and rates of emergence were reduced at salinities ~ -0.6 MPa NaCl, and were higher in tepary than navy at -1.2 MPa. Tepary beans tended to maintain higher water and osmotic potentials, and at -0.9 MPa had less reduction in leaf area than navy beans. Fresh weights, dry weights and root:shoot ratios declined in all genotypes with increasing salinities. Plants grown hydroponically were stressed with -0.10, -0.25, and -0.50 MPa NaCl during either vegetative or reproductive stages. Navy had equal or greater fresh and dry weights of leaf, stem, and pods at -0.10 MPa, but tepary beans had equal or greater weights at the highest salinity relative to navy. Tepary had the greatest pod weight with -0.50 MPa NaCl applied during the reproductive stage. Carbon exchange rates (CER) were lower in navy than one or both tepary beans at some sampling times. Tepary beans tended to have higher leaf water and osmotic potentials than did navy. Transpiration and stomatal resistance values were similar in all genotypes, while leaf temperatures were different in white tepary versus navy. Tepary beans yielded higher than navy when grown in low and high salinity fields. Transpiration rates, leaf water and osmotic potentials, and CERs were similar or higher, while stomatal resistance and leaf temperatures were similar or lower in tepary than in navy. Plant height and stand count also were measured. Tepary was more salt tolerant than navy, exhibiting greater tolerance to NaCl at every growth stage.

Shoot and root fresh and dry weight, shoot length, leaf area, leaf area index and relative growth rate of 14 day old tepary bean (Phaseolus acutifolis Gray) and navy bean (Phaseolus vulgaris L.) seedlings were reduced following treatment with NaCl solution exhibiting osmotic potential of either -0.25, 0.50, and -0.75 MPa. Salinity reduced the growth of navy bean more than tepary bean. The physiological basis of the adaptive response of tepary bean seedlings to salt stress was explored by determining the water and osmotic potentials, relative water content, free amino acid and sugar concentrations, distribution and levels of inorganic ions within the seedlings and ATPase activity of the root plasma membrane. Salinity led to an osmotic adjustment in the leaves and the proximal part of the root of tepary bean. Turgor remained almost constant whereas osmotic and water potential and relative water content declined following the salt treatments. The osmotic adjustment of the leaves and proximal part of the roots was -1.7 MPa and -1.2 MPa, respectively, in seedlings treated with -0.75 MPa NaCl solution. Free amino acids and sugars increased under salinity stress in both species but they increased more in the tepary bean. Glucose was the most abundant free sugar. The nonstructural carbon solutes contributed -0.15 MPa to the seedling's osmotic adjustment whereas Na, Cl, K and Ca ion levels contributed -0.85 MPa. However, the levels of these solutes were not large enough to account for the total osmotic adjustment observed in the salt treated seedlings. This study shows that tepary bean has specific strategies to overcome the impact of salinity through osmotic adjustment and exclusion of Na and Cl ions from the stems and leaves by retaining these ions in the proximal part of root and stem base. (Abstract shortened with permission of author.)

Tissue culture and radicle excision techniques were employed to evaluate salt tolerance in alfalfa (Medicago sativa L.). Plant suspension cultures of either seedling root or shoot origin were studied in media with or without supplemental NaCl (3.54 g liter⁻¹). In most cases, the growth rates of root-derived cultures were stimulated by this low level of supplemental NaCl while most shoot-derived cultures were not stimulated by NaCl. Excised radicles of three populations of alfalfa which possessed widely differing ranges of germination salt tolerance were screened in four salts (NaCl, KCl, Na₂SO₄, and K₂SO₄) at six varying concentrations. As was observed in the tissue culture experiments, low levels of NaCl (7.09 g liter⁻¹) stimulated radicle elongation of all populations as compared to the elongation levels of the control solutions (no supplemental salts). In general, for NaCl, the population that posessed the highest degree of germination salt tolerance (Az-St 1982) also displayed the greatest rates of radicle elongation especially in the highest salt concentrations. Additionally, this population along with the moderately germination salt tolerant population (Az-ST 1979) maintained higher rates of elongation in KCl, K₂SO₄ and Na₂SO₄ than did the control germplasm which has little germination salt tolerance (Mesa Sirsa Control). Examinations of each individual population in all four salts simultaneously, indicated that the sulfate salts reduced radicle elongation to a greater extent than did the chloride salts. Evaluation of both osmotic effects and specific ion effects showed that the specific ion effects attributed to the anions were more detrimental to radicle elongation than were the osmotic effects.

A study of the Salt River Indian Reservation in central Arizona evaluated pre-development hydrologic conditions with an emphasis on simulating ground-water flow conditions within the reservation, where data was scarce before extensive aquifer pumping began in 1940 in adjoining portions of the East Salt River Valley. Water-resource development began in the valley with the completion of the Tempe Canal in 1871. Additional canals and irrigated agriculture spread quickly in areas along the Salt River, which has a mean annual flow of about 1.25 million acre-feet. Pre-development ground-water flow was horizontal and steady-state. The simulation indicated that the available water-level data, though corrupted in areas adjacent to the river, more properly described the virgin system than flow estimates. Sensitivity analyses indicated that simulated heads on the reservation were sensitive to all processes except evapotranspiration. Recharge through the riverbed, evapotranspiration, and subsurface outflow were all co-dependent.

Chan Yee-kwan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 108-131). / Abstracts in English and Chinese. / Thesis Committee --- p.i / Abstract --- p.ii / Acknowledgments --- p.v / General Abbreviations --- p.vii / Abbreviation for Chemicals --- p.x / Table of Contents --- p.xi / List of Figures --- p.xiv / List of Tables --- p.xv / Chapter 1. --- Literature Review / Chapter 1.1 --- Salinity as a global problem --- p.1 / Chapter 1.2 --- Salinity and agriculture --- p.2 / Chapter 1.3 --- Plant adaptation to salinity --- p.4 / Chapter 1.3.1 --- Salt secretion --- p.6 / Chapter 1.3.2 --- Ion transport --- p.8 / Chapter 1.3.2.1 --- Role of H+-ATPase in salt tolerance --- p.8 / Chapter 1.3.2.2 --- Potassium and sodium uptake --- p.13 / Chapter 1.3.2.3 --- Sodium efflux --- p.15 / Chapter 1.3.3 --- Osmotic adjustment --- p.20 / Chapter 1.3.3.1 --- Accumulation of mannitol --- p.21 / Chapter 1.3.3.2 --- Accumulation of proline --- p.23 / Chapter 1.3.3.3 --- Accumulation of glycinebetaine --- p.23 / Chapter 2. --- Materials and Methods / Chapter 2.1 --- Plant materials and growth conditions --- p.26 / Chapter 2.1.1 --- Surface sterilization of Arabidopsis seeds --- p.26 / Chapter 2.1.2 --- Determination of sub-lethal inhibitory doses of sodium --- p.27 / Chapter 2.1.3 --- Growth conditions of Arabidopsis seeds for total RNA extraction --- p.27 / Chapter 2.1.4 --- NaCl dosage tests --- p.28 / Chapter 2.1.5 --- Expression kinetic tests --- p.28 / Chapter 2.2 --- Isolation of total RNAs --- p.28 / Chapter 2.3 --- Isolation of genes differentially expressed in NaCl concentration by RAP-PCR --- p.30 / Chapter 2.3.1 --- RNA fingerprinting by RAP-PCR --- p.30 / Chapter 2.3.2 --- PCR reamplificatin of RAP products --- p.31 / Chapter 2.3.3 --- Cloning of differentially expressed genes --- p.33 / Chapter 2.3.3.1 --- Ligation of inserts into pCR-Script vector and transformation --- p.33 / Chapter 2.3.3.2 --- Ligation of inserts into pBluescript II KS (+) T-vector and transformation --- p.36 / Chapter 2.3.3.3 --- Screening of recombinant plasmids --- p.37 / Chapter 2.4 --- Sequencing of differentially expressed genes --- p.39 / Chapter 2.4.1 --- DNA cycle sequencing --- p.39 / Chapter 2.5 --- Northern blot hybridization of NaCl inducible genes --- p.40 / Chapter 2.5.1 --- RNA fractionation by formaldehyde gel electrophoresis --- p.40 / Chapter 2.5.2 --- Northern blotting --- p.41 / Chapter 2.5.3 --- Preparation of single-stranded DIG-labeled PCR probes --- p.41 / Chapter 2.5.3.1 --- Isolation of Total RNA --- p.41 / Chapter 2.5.3.2 --- Primer design --- p.42 / Chapter 2.5.3.3 --- PCR amplification of single-stranded DIG PCR probes --- p.43 / Chapter 2.5.4 --- Hybridization --- p.45 / Chapter 2.5.5 --- Stringency washes --- p.46 / Chapter 2.5.6 --- Chemiluminescent detection --- p.46 / Chapter 3. --- Results / Chapter 3.1 --- Determination of sub-lethal inhibitory doses of sodium --- p.48 / Chapter 3.2 --- Isolation of total RNA from A. thaliana treated with sodium chloride --- p.48 / Chapter 3.3 --- Isolation of genes differentially expressed in sodium concentration by RNA arbitrarily primed polymerase chain reaction RAP-PCR --- p.52 / Chapter 3.3.1 --- Differential cDNA fragments identified by RAP-PCR --- p.52 / Chapter 3.3.2 --- PCR reamplification of RAP products --- p.52 / Chapter 3.3.3 --- Cloning of selected RAP-fragments --- p.62 / Chapter 3.4 --- Nucleotide sequence analysis of selected RAP PCR clones --- p.65 / Chapter 3.5 --- Expression pattern analysis of salt inducible genes by northern blot hybridization --- p.75 / Chapter 3.5.1 --- Preparation of single-stranded digoxigenin (DIG)-labeled probes --- p.75 / Chapter 3.5.2 --- Dosage response of NaCl inducible genes --- p.79 / Chapter 3.5.3 --- Expression kinetics of NaCl inducible genes --- p.80 / Chapter 4. --- Discussion / Chapter 4.1 --- Isolation of RAP-PCR targets --- p.93 / Chapter 4.2 --- Expression of NaCl inducible P450 genes --- p.94 / Chapter 4.2.1 --- Cytochrome P450 CYP73A5 --- p.97 / Chapter 4.2.2 --- Cytochrome P450 CYP83A1 --- p.98 / Chapter 4.3 --- NaCl induction gene related to post-transcriptional activities --- p.99 / Chapter 4.3.1 --- Glycine-rich RNA binding protein (BAC F3F19) --- p.100 / Chapter 4.3.2 --- Chloroplast signal recognition particle (54CP) --- p.103 / Chapter 4.4 --- Conclusion --- p.106 / References --- p.108

Programa Institucional de CapacitaÃao Docente e TÃcnica / CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O presente trabalho traz um levantamento dos termos usados por indivÃduos que desenvolvem atividades relacionadas à IndÃstria do sal e tem como proposta a elaboraÃÃo de um glossÃrio dos termos desse domÃnio. A pesquisa foi desenvolvida nas localidades de MossorÃ, Areia Branca e Grossos, municÃpios que fazem parte da regiÃo salineira do Rio Grande do Norte. Portanto, o nosso objeto de estudo sÃo os termos da indÃstria e da cultura do sal, tanto na modalidade escrita, como tambÃm na modalidade oral, levando em consideraÃÃo a possibilidade da variaÃÃo terminolÃgica. O trabalho consta, primeiramente, do levantamento histÃrico e institucional da indÃstria do Sal, bem como de todo o processo de sua produÃÃo. Neste trabalho, sÃo apresentadas as diferentes ciÃncias do LÃxico e seus respectivos enfoques teÃricos, mas a Ãnfase maior à dada nas orientaÃÃes teÃrico-metodolÃgicas da Socioterminologia, pois esta à a abordagem adotada por nÃs neste trabalho. Depois, sÃo expostos os procedimentos metodolÃgicos para a realizaÃÃo da pesquisa socioterminolÃgica, procedimentos estes distribuÃdos em duas etapas que sÃo a metodologia da pesquisa de campo e a metodologia da organizaÃÃo do glossÃrio. Logo em seguida, vem o GlossÃrio da Terminologia do Sal (o GLOSSAL), composto de 325 termos organizados alfabeticamente, com um Ãndice remissivo sistemÃtico, distribuÃdo em quatro campos conceituais, a saber: fabricaÃÃo, beneficiamento, comercializaÃÃo e utilizaÃÃo e consumo. O levantamento desse corpus se justifica, pelo que conhecemos, principalmente, pela ausÃncia de trabalhos escritos de organizaÃÃo e sistematizaÃÃo de glossÃrios tÃcnico-especializados sobre a Ãrea em foco, nos municÃpios pesquisados. AlÃm disso, esta obra se justifica tambÃm por possibilitar a divulgaÃÃo de um produto terminogrÃfico destinado, nÃo sà aos especialistas da Ãrea em questÃo e aos das CiÃncias do LÃxico e pesquisadores afins, como tambÃm ao grande pÃblico e aos interessados em aprofundar seus estudos na terminologia do sal. / The research hereafter presents a study on words used by individuals that work with activities related to salt industry and has the proposal of elaborating a glossary on the terms in that domain. The investigation has been developed in locations such as MossorÃ, Areia Branca and Grossos, cities that make part of Rio Grande do Norte salty region. Our work aims at studying industry terms and salty culture, in written and oral modality, considering the possibility of terminological variation. The work consists, primarily, of a salty industry historical institutional investigation as well as of the entire production process. In this work, different lexical sciences are introduced and their respective theoretical approaches, but the main emphasis is put on Socioterminology theory and its methodological guidelines, considering its importance for this research. After that, the methodological procedures for the socioterminological research are exposed and distributed in two phases: field research and glossary organizational methodology. In sequence, the Glossary of Salty Terminology (GLOSSAL) is presented, composed of 325 terms alphabetically organized, with a systematical remissive index, distributed in four conceptual fields: manufacturing, beneficiatement, trading, utilization and consumption. This corpus investigation is justified by the absence of written works organized and systemized in the salty technological area in the specified cities. This work also contributes to provide the divulgation of a terminographical product destined, not only to specialists in the area and to Lexical Science researchers, but to the public interested in improving their knowledge in salty terminology.

The low-lying topographic nature of salt marshes makes plants in these communities particularly vulnerable to increased salinity and inundation exposure associated with sea level rise. Both increased salinity and inundation have been cited as major causes of reduced plant performance and survival in marsh and areas fringing marsh. In addition to limitations imposed by physical stress, interspecific interactions have also been shown to mediate the performance and survival of salt marsh and salt marsh fringing species. The Stress Gradient Hypothesis (SGH) postulates that species interactions shift from competitive to facilitative as stress levels increase and predicts that (a) the frequency and intensity of facilitative interactions increase as conditions become more stressful for plants and (b) the strength of competitive interactions increases as abiotic stress levels diminish. The SGH has been rigorously tested to examine how both the frequency and intensity of species interactions change under varying physical stress levels. Studies conducted in salt marsh systems have shown facilitation to be as strong of a driving force as competition in influencing plant performance and survival and have shown that while competition appears to be the pervasive force in the less physically stressful terrestrial zones fringing salt marshes, facilitation influences the performance and survival of species in harsher marsh areas. Under conditions of sea level rise, it remains unclear if the nature of interspecific interactions would shift as stress levels change. This research endeavors to examine the interplay between abiotic stresses and biotic interactions under conditions of increased salinity and inundation exposure. The first study presented here investigated the effects of increased inundation and soil salinity associated with sea level rise on four salt marsh fringing species, and assesses how competition and facilitation impact survival of salt marsh fringing plant survival under these changing conditions. All plant species experienced reduced growth and photosynthetic inhibition below their current distributional positions, both in the presence and absence of neighboring above ground vegetation. The findings also signal a potential shift in the nature of interspecific interactions from competition to facilitation to neutral as plants begin to experience increased salt and inundation exposure. The second study aimed to disentangle the effects of increased soil salinity and increased soil moisture on four salt marsh fringing species, and to examine the effects of plant neighbors. The results showed that fringe plants exposed to increased inundation experienced a two-fold reduction in performance and survival over 750 g pure salt addition, suggesting that inundation may be a more important limiting factor than salinity with rising sea levels. Landward transplants at the forest-fringe margin exposed to lower soil salinity and decreased inundation exhibited a three-fold increase in performance and survival when compared to controls. Neighbor manipulation studies, which consisted of trimming neighboring vegetation to ground level, again suggested that interspecific interactions in salt marsh fringing species may shift from competitive to facilitative with climate-induced sea level rise. Overall, our findings suggest that salt marsh fringing species may not be able to tolerate changing conditions associated with sea level rise and their survival may hinge on their ability to migrate towards higher elevations. The final experiment tested the Stress Gradient Hypothesis and investigated the relative importance of facilitation and competition in a salt marsh system under varying stress levels. This study also ascertained whether salt or inundation exposure is the primary influence on salt marsh plant performance and survival. As in previous studies, our findings suggest that many salt marsh plants don't require, but merely tolerate harsher abiotic conditions. The results showed that plants at higher elevations were depressed by strong competitive pressure from neighboring fringe species while plants at lower elevations benefited from the presence of neighbors. Collectively, the results of these studies indicate that species interactions are an integral driver of plant distribution in salt marsh communities. Furthermore, our findings indicate that changing stress levels may not always result in a shift in the nature of interspecific interactions. These studies have endeavored to show that the interplay between competition and facilitation interacts with physical processes to determine the growth and performance of both fringe and marsh plant species. The paucity of studies examining the roles of species interactions and changing abiotic stress levels on multiple salt marsh and salt marsh fringing species warrants the need for additional research. The responses of salt marsh and salt marsh fringing species to sea level rise can not only serve as very valuable and sensitive indictors of climate change, but will also aid in predicting the future location of the marsh-fringe-forest ecotone, which is predicted to shift inland as sea levels continue to rise.

Concentrations of selenium (Se), manganese (Mn), zinc (Zn), cadmium (Cd), lead (Pb) and arsenic (As) were measured in the water column, sediment and biota, in conjunction with selected physicochemical data, from representative wetland types at a mining site within Salt Lake County, Utah, USA. The selected field sites included Oolitic Pond (lentic) and Lee Creek (lotic), which are moderately contaminated brackish, alkaline aquatic wetlands managed by a copper mining industry. These fishless wetlands are located in a geographic region that poses risk to migratory shorebird populations from dietary Se. A spatial sampling study demonstrated the extent of variation in total Se concentration within the wetlands. With the exception of the sediment compartment, Se concentration did not differ significantly along the 2-mile length of Lee Creek or within the Pond. The differences in sediment total Se concentrations between the Creek East and West segments characterize lower Lee Creek as having two segments distinguished by unique processes that influence the sediment Se accumulation profiles. Se accumulation trends were observed temporally over 3-years (2000 to 2002) and over two seasons (spring and autumn). Total Se body burden in benthic invertebrates was more clearly associated with sediment/detritus Se concentrations than with surface water concentrations. Three invertebrate groups dominated the aquatic invertebrates assemblage in the lotic and lentic benthos; primary consumers (Chironomidae, Diptera), generalist feeders (Hemiptera) and predators (Odonata). The chironomid larvae accumulated 1.3 to 39 times the trace metal concentrations of the Hemiptera or odonate taxa, independent of trace metal type (essential or non-essential) or wetland occupation. Organism-specific factors, such as habitat selection and preferential feeding habits, were proposed to influence benthic invertebrate accumulation profiles by modifying trace metal exposure. Mixed diets, trophic omnivory and the complexity of wetland biogeochemistry limit the power of stable nitrogen fractionation signatures to define benthic food web relationships. Wetland site-specific processes impacted Se accumulating efficiency, with trace metal concentrations from 4 to 7 times greater within the lentic benthic system than the lotic. The fractionation of the natural abundant stable carbon isotopes revealed the importance of sedimentary and detrital organic carbon as dietary sources for the benthic food web. Sediment organic content was not significantly associated with sediment, or invertebrate, Se accumulation profiles. Ecological risk assessments based on sound understanding of metal chemistry and the interactions between the sediment matrix and benthic organisms are necessary to provide tools for environmental management. / Graduation date: 2005