Ballona Wetlands Research
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Merck/AAAS Research Associates have presented the results of their research at the following conferences:
Southern California Conference for Undergraduate Research
Occidental College, Los Angeles, California, November 18, 2006 (Patrick Carter, Wesley Citti, Theresa Nguyen, Charisse Sy)
California State University at Los Angeles, November 17, 2008 (Wesley Citti, James Holmquist, Jeffrey McGowan, Anh Nguyen, Charisse Sy, Jaclyn Torres)
Southern California Society of Environmental Toxicology and Chemistry Conference
Lake Arrowhead, California, April 9-10, 2007 (Patrick Carter)
National Conference for Undergraduate Research
Dominican University of California, San Rafael, April 12-14, 2007 (James Holmquist)
West Coast Biological Sciences Undergraduate Research Conference
Loyola Marymount University, Los Angeles, California, April 28, 2007 (Patrick Carter, James Holmquist, Wesley Citti, Theresa Nguyen, Charisse Sy)
SACNAS National Conference
Kansas City, Missouri, October 11-14, 2007 (Jaclyn Torres)
LMU Interdisciplinary Student Research Symposium
Loyola Marymount University, Los Angeles, California, October 26, 2007 (Arthur Blikian, Wesley Citti, James Holmquist, Jeffrey McGowan, Anh Nguyen, Charisse Sy, Jaclyn Torres)
Current Student Abstracts
Developing Salicornia virginica as a Bio-monitor for Heavy Metals in the Ballona Wetlands
James R. Holmquist (Mentors: Dr. Philippa Drennan and Dr. James Landry)
The coastal Ballona wetlands are a part of the highly urbanized Los Angeles watershed. Studies performed on the water quality of the channel feeding the wetlands have shown high levels of heavy metals. The widely distributed halophyte Salicornia virginica (commonly known as pickle weed) was used to establish trends in heavy metal pollution for Ballona wetlands. It is hypothesized that S. virginica in a contaminated wetland will take up heavy metals along with the salts. Plant tips and soil samples, 85 for each, were collected from 16 sites throughout the Ballona wetlands. Five plant tips were taken from the Sunset Beach Back Bay for comparison. The methods used were oven drying to establish wet and dry weights for water content, flame photometry to determine sodium and potassium levels in the tissues, and atomic absorption spectroscopy for zinc (flame analysis) and cadmium (graphite furnace) levels. The amount of each metal in the plants was correlated with the amount of metal in the soil. Correlations were positive and significant for cadmium and zinc. With S. virginica established as a reliable bio-monitor, areas of constant elevated cadmium and zinc pollution were identified.
Biomagnification of Wetland Contaminants in Garden Spiders
Jaclyn Torres and Charisse Sy (Mentors: Dr. James Landry, Dr. Jeremy McCallum, and Dr. Martin Ramirez)
The purpose of this study was to examine spatial heterogeneity in the heavy metal accumulation in garden spiders, Argiope trifasciata, and to assess the impact of heavy metal loads on spider fitness. During October 2006, adult females were collected from three sites at the Ballona Wetlands, a highly degraded urban wetland in Los Angeles. Spiders were measured (carapace width, mm) and weighed (mg) prior to analysis with atomic absorption spectroscopy to yield whole-body metal concentrations (Cd, Cr, Cu, Pb, Zn). Spider excretia was analyzed via HPLC. Size and weight values were natural logarithm transformed and the procedures of Jakob et al. (1996) were used to generate the residual index (RI, the residuals of body mass on body size), a non-destructive measure of body condition, for each spider. ANOVA tests were used to assess spatial heterogeneity in whole-body metal concentrations among the three sites. Of the five metals, cadmium and chromium were homogeneous among sites, whereas copper, lead, and zinc varied significantly by site with different patterns in each case. Regression analysis for each metal using various groupings of the samples showed significantly negative relationships between dry metal concentrations and spider bodily parameters in four cases (Cd: size, weight; Cd, Cu: residual index). Further analyses must be completed on the HPLC excretia samples. As major invertebrate predators, spiders may bioaccumulate materials from the bodies of their prey. Our results are consistent with such a possibility and suggest that web-building spiders residing in polluted areas may be compromised in terms of fitness.
Freely Dissolved Concentrations of Selected PCBs, PAHs, and Chlorinated Pesticides in Ballona Wetland and Creek
Anh P. Nguyen (Mentor: Dr. Rachel G. Adams)
The Ballona Wetlands are designated as an ecological preserve with environmental assessment and restoration currently underway. The Ballona Creek Estuary is a contaminated body of water for which the Total Maximum Daily Loads (TMDLs) for several hydrophobic organic contaminants (HOCs) have already been established. However, traditional methods for dissolved chemical measurements (e.g., liquid-liquid extraction) are difficult to use for HOCs at the current TMDL-regulated levels. In this study, passive samplers (polyethylene devices, PEDs) were deployed in the wetlands in June ’07 to measure the dissolved concentrations of selected TMDL-regulated contaminants: polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and chlorinated pesticides. These newly-developed passive samplers allow for the measurement of contaminants at trace levels. The PEDs were deployed in metal paint buckets fastened to stakes in the wetland channels. These buckets ensured that the PEDs were submerged and sampling water throughout the experiment. The PEDs were deployed at four locations in the wetland and at one location in the Creek for 14 days. Blank PEDs were used to correct for any contamination during deployment and recovery. Upon recovery, the PEDs were cleaned and extracted. The extracts were analyzed using a gas chromatograph-mass spectrometer (GC-MS). The dissolved chemical concentrations will be calculated using water equilibrium partitioning coefficients and corrected for cases in which equilibrium is not reached. The measurements will allow scientists and regulators to assess the current HOC levels in the Wetland and Estuary so that these HOCs may be evaluated with respect to the current TMDLs.
Survey of Microorganisms in the Ballona Wetlands
Arthur Blikian (Mentors: Dr. Gary Kuleck and Dr. John Dorsey)
The objective of the research was to establish a method to be able to identify ecological samples of microbes through Automated Ribosomal Intergenic Spacer Analysis. Initial experimentation involved instituting a method of operation to be able to identify a specific genetic fingerprint for each clade or species. This was done through repeated isolation of bacteria via plating to obtain one colony which then underwent PCR to amplify the 16S, ITS, and a part of the 23S region. The PCR product then underwent gel electrophoresis and a series of bands were obtained. Alongside this experiment Vitek analysis was performed on the isolates to establish a correlation between the bands and the species. In most cases a 95% or higher confidence was attributed to the identification of the bacteria. Through repeated testing and a gradient PCR (to ensure actuality of bands) unique “fingerprints” were obtained for various microbes. These “fingerprints”, based on initial testing, seem to be species specific. These findings allow the continuation of the research unto uncultured ecological samples. A method of filtration needed to be established prior to PCR so that only bacteria were being identified. This involved a two step vacuum filtration using durapore and a/e glass filters to obtained workable samples. These samples were then either frozen for later experimentation or DNA was extracted and then amplified by PCR for electrophoresis. A series of bands is the target at which point the bands will be integrated into a library which will be expanded upon. All water samples are from the Ballona wetlands.
Identifying Soil Bacteria and Biochemical Pathways in the Ballona Wetlands for the Bioremediation of Organic Pollutants
Wesley T. Citti and Jeffrey D. McGowan (Mentors: Dr. Kam Dahlquist and Dr. Carl Urbinati)
The Ballona Wetlands in Los Angeles County are contaminated with organic pollutants including polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), and single-ring aromatics (e.g. toluene) from urban run-off. Initially, to determine whether biochemical pathways exist in the wetlands to degrade toluene we attempted to enrich bacteria from the soil that could metabolize toluene. We obtained a single, pure environmental isolate from media with citrate as a sole carbon source but not from media with toluene as a sole carbon source. Genomic DNA was isolated from the environmental strain and a variable region of the 16S rRNA gene was subcloned. DNA sequencing identified the environmental isolate as Pseudomonas putida F1. Pseudomonas species, including Pseudomonas putida F1, are known to degrade toluene. Currently we are attempting to clone the todC1 gene which encodes one subunit of toluene dioxygenase, the first enzyme in the toluene degradation pathway from the isolated Pseudomonas putida F1. In order to assess the diversity of soil bacteria in the wetlands we isolated genomic DNA from soil samples, amplified a variable region of the 16S rRNA gene and constructed sub-genomic libraries. To date, 51 clones from one library have been sequenced and identified by BLAST database searching. Thus far, the most abundant bacterial species identified is Pseudomonas putida F1; other species identified include Actinobacteria and Sphingomonas spp. Additionally, we are using Length Hetereogeneity-PCR (LH-PCR) to assess diversity in the soil samples. LH-PCR results will be compared to results from direct sequencing of 16S rDNA sub-genomic library clones.
This award program is funded by The Merck Institute for Science Education and administered by the American Association for the Advancement of Science.
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Last modified: 2/1/2008
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