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An in-depth field study of the Delacroix Island producing field illustrates the evolution of the east-trending Delacroix Island Fault during the last 13 My. Well log correlations and 3-D seismic interpretation of 22 subsurface bio-stratigraphic horizons across the fault reveal variable stratigraphic thicknesses and displacement. Wells, with well log curve data as shallow as 31 m (100 ft) below the surface, were used to calculate interval thicknesses, expansion indices, sediment accumulation rates, burial history and magnitudes of displacement. Through these analyses, a correlation was found between the positioning of ancient Miocene depocenters over Delacroix Island and a period of increased fault activity. Historic satellite imagery (last 34 yrs) of the field depicts a lineation on the modern marsh surface coincident with the upward projected fault plane. Continuous wetland loss on the downthrown side of the fault trace suggests that recent and continued fault movement may be contributing to marsh submergence.

Rivers all around the world have become increasingly polluted with heavy metals, largely due to industrialization and urbanization. Organisms exposed to high concentrations of heavy metals have shown evidence of biotoxicity and physical deformities. With biomagnification in mind, the possibility that this contamination may soon directly affect humans is a real concern, and policies in manufacturing industries worldwide may have to be reformed. In this study, we measured the concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and lead (Pb) in the Hatillo River and compared these values to those measured in the Tarcoles River, a highly polluted river, and Terciopelo Creek, a relatively clean river. The results showed that the Hatillo River had significantly lower levels of most detected heavy metals than both the Tarcoles and Terciopelo. Overall, sediments in all rivers showed high levels of heavy metal content--especially in chromium, copper, nickel, and lead--which could build up and affect organisms over a long period of time.

<p dir="ltr">Cropland expansion and intensification negatively impact water quality in downstream waterways through increased nutrient loading in the form of agricultural runoff and the loss of natural features that support water storage and nutrient removal. Nowhere is this more evident than the Corn Belt region of the United States where intensive row crop production generates high crop yields but also disproportionately high nutrient export to the Mississippi River. Depressional wetlands were a defining feature of this landscape prior to agricultural land development and are known to retain high levels of nutrients. Thus, protection, restoration, and creation of these wetlands is an increasingly important part of nutrient mitigation strategies in this landscape. Anoxic soils inherent to these wetlands provide the necessary oxidation-reduction (redox) conditions for nitrogen removal via denitrification, but also promote the production of greenhouse gasses including carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Denitrification is a key water quality function via conversion of nitrate to N₂ that can also yield high fluxes of N₂O when incomplete. The key environmental factors that govern efficiency of this process and relative differences in nitrogen removal efficiency among wetland types are not well constrained. To address this gap, denitrification rates, greenhouse gas benthic production rates, greenhouse gas emission rates, and environmental conditions were measured in a series of wetland mesocosms with distinct plant species (reed canary grass, rice cutgrass, arrowhead, and an unplanted control) during peak biomass and plant senescence. My results revealed a denitrification stimulation effect from nitrate pulsing that differed significantly by plant type and that responses varied by stage of plant growth. Specifically, I found that labile carbon components resulting from root exudates, decomposition of plant residues and soil organic matter also positively influence denitrification. Additionally, I found that benthic production of CH₄ and CO₂ varies by plant type, as does surface flux for CO₂. Aerenchyma tissue was identified as a controlling factor in greenhouse gas emissions in the mesocosms, and a determining factor in the relationship between benthic production and system flux of greenhouse gasses. My work shows the importance of plant selection to improve design and management practices in agricultural wetlands.</p>

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