August 17, 2012
In our last week interning here on Catalina Island, I started to realize that soon I would have to go back to Los Angeles and begin the school year. While I’m extremely excited to be surrounded by people I haven’t seen for almost three months now, I have to say that I’m definitely going to miss the sheer amount of space and endless beauty that this place provides.
This week, I have been working extensively with Professor Ginsburg’s Environmental Studies 320a course, working as the student’s teaching assistant. We have been working in the lab each day this week, testing for different nutrients in the water column of Big Fisherman’s Cove.
On Monday, students collected water samples from the cove using a Niskin bottle. To compare data at different depths, the students collected water at 2, 4, 6, 8, and 10 meters. From this, they looked at dissolved oxygen content, as well as ammonia and iron levels.
For the analysis of ammonia and iron, we used a serial dilution of two different standard solutions. Using an acid base reaction with the standards, we created a color change reaction, which we then used a spectrophotometer to measure the specific absorbance of each solution at different wavelengths. With our samples, we added the same reagents and catalysts that we added to the various dilutions of the standard solution, and measured the absorbance of the samples as well.
Standard solution, catalyst, and reagent for the ammonia analysis. Photo by Justin Bogda
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Top: standard solution assay for ammonia analysis. Bottom: seawater samples from 2, 4, 6, 8, and 10 meters in Big Fisherman’s Cove. Solutions are in cuvettes, ready to be analyzed by the spectrophotometer. Photo by Justin Bogda
Sample in spectrophotometer before analysis. Photo by Justin Bogda
Receiving a standard curve from our standards, each at a different concentration covering the ranges that we expected to see in our samples, we were able to make a curve correlating the concentrations with absorbance, and compare our samples to that curve to determine what the specific concentrations of our samples were.
The first day that the class tried the assay for ammonia, results were less than ideal. I performed the assay as well, and struggled to make a standard curve from which I could get meaningful data. The following day, I tried to perform the assay again, this time using more precise instruments such as volumetric flasks to perform the dilutions, and I obtained much better results. Ammonia levels were in the range, between .5 and 4 µM, that we expected. Iron, for which we tested today, was seen in concentrations between .5 and 2 µM, a bit less than the 10 µM concentration that we expected.
Measuring nutrients such as ammonia in the water provides a baseline measurement that, according to our records, has not been done in some time. If concentrations were greater than we expected, it would be an indication of pollution from the land, as natural levels ammonia from excretions from organisms should be negligible. It is helpful to measure indicators of water health, especially in a protected area like Big Fisherman’s Cove, so that if there were potential threats to it such as sewage runoff, we could detect it.
When I look back on this summer, I feel a definite sense of accomplishment. While a great deal of the work we did this summer was immediately beneficial to my practical skills and knowledge, I feel even better that my fellow interns and I set up projects and potential research that can be built at the Wrigley campus by the Environmental Studies department and other collaborators. I will be coming back throughout the fall to continue with the restoration project and seeding, so while I leave Catalina nostalgic, I’ll get to continue work here soon.
August 7, 2012
This past Thursday we finally were able to take the soil samples from our plots on the Deer Valley Trail to USC’s University Park campus and start testing them. This marked the first step in collecting real data from our plots that will go toward our experiment.
Our experiment looks at the effects of invasive plant species on soil health and quality. To measure the overall health of the soil, we need to get accurate reads on the nitrogen, total carbon, and organic carbon in the soil. As stated before, upon removal of invasives from the plots, we hope to see a decrease in nitrogen level. When the health of the soil increases with declining invasives, and with the eventual return of native plants, we hope to see the carbon content in the soil increase.
Before we trekked back to the mainland to analyze our samples, we decided to take more samples to use comparatively with the samples from our plots. To see what a more “healthy” soil profile should look like, we took two samples from beneath two different native plants, Toyon (Heteromeles arbutifolia) and sagebrush (Artemisia californica). Along with these samples, we also samples from each of the three potential sites for our restoration project, to get an idea of soil health in these areas.
Using a geology lab on campus with the help of our professor Dr. Lisa Collins, we weighed approximately 10 mg from each soil sample, and packaged them accordingly to be analyzed by an elemental analysis. To weigh 10 mg, it required a great deal of precision, and quite a few practice runs between the four of us to not spill at all and to keep the samples neat and organized. Soon enough, we were able to measure out the samples so that they could be analyzed.
Above: Intern Judy Fong carefully measures out 10 mg of a soil sample. Photo by Justin Bogda.
The elemental analysis uses standard curves to interpret how much of a substance is in a sample. For total carbon, the 10 mg samples, packaged in small, flexible tin cups, are burned at 900 °C, and reduced to carbon monoxide. This then runs through a mass spectrometer that detects the amount of carbon monoxide released, and this value is compared to a standard curve to detect the amount of carbon in the soil. Similarly, nitrogen gas is read by the mass spectrometer and compared to a standard curve. In order to measure the organic carbon in the soil, we had to measure separately another 10 mg from each sample, and instead put them in small silver cups. In order to just measure organic carbon, rather than total carbon, a small amount of hydrochloric acid is added to the cups. By doing this, calcium carbonate, the main component of the inorganic carbon in the sample, is released from the sample, and only the organic carbon is left.
Above: Soil samples after they have been measure, ready to be analyzed by the elemental analysis. Photo by Justin Bogda.
Within the next week, our first sample results should be complete, and we can finally begin collecting quantitative data for our project.
August 5, 2012
One of our main projects for this internship is establishing native plant restoration sites within previously disturbed soil along the Deer Valley trail adjacent to USC’s Wrigley Institute for Environmental Studies. The first site is along a disturbed slope where fennel (Foeniculum vulgare) was removed manually last year and has begun to re-sprout. The second site was degraded due to soil collection for maintenance purposes; thus, both the area of removal and the connecting path traveled by trucks and bulldozers is where we plan on working. We hope these sites will provide data for native plants’ effects on the area through soil nutrients and overall growth, as well as what restoration methods have the highest rates of survivorship. Along an interpretive trail, the sites will provide educational opportunities for students, residents, and other visitors on restoration efforts.
We are working towards installing restoration plots that will provide data on what methods increase rates of survivorship. Periodically, we will test the soil for nitrogen and carbon content; thus, creating a baseline for how native plants contribute to nutrient pools in a disturbed area. We hope that the results from this project will possibly provide an alternative to carbon emission cap and trade. Instead of a market-based solution for businesses to offset their carbon emissions, we theorize that by investing in restoration efforts, businesses will contribute to the improvement of disturbed ecosystems while also promoting sustainability.
With the guidance of Peter Dixon, Senior Technician for the Catalina Island Conservancy Native Plant Nursery, we have formulized not only a restoration plan, but also an experimental design within it. Prior to any restorative work, we will test the soil to quantify its quality.We will compare various plant mixtures of seeded and potted plants, perennials and annuals. Fortunately, the location of the restoration site is within an area of relatively high native plant diversity. During a recent site survey, Dixon identified over 20 native plant species present, and we are working towards identifying several more native grasses. From these preexisting plants, we plan to collect seed, process it, and replant within the restoration site. Furthermore, we will be looking at the varying successes of planting annuals, climax species such as Lemonade Berry (Rhus integrifolia) and Toyon (Heteromeles arbutifolia), and coastal sage shrub species. In order to ensure the success of the site, we will use erosion mats to prevent soil erosion, and fencing to prevent deer and bison predation.
In terms of timing, seeding will occur in August, while all potted plants and shrubs will be planted just before fall to maximize the amount of rainfall available. In addition, our plant plots will be watered monthly during initial plant establishment. However, we will include control plots to observe the success of plants that are not manually watered. The four of us will continue to work on these restoration sites throughout the fall and early winter. The fall and spring ENST 320A classes may also take soil samples for the field component of the course. Next summer’s USC interns will continue expanding on the restoration sites and assume basic maintenance.
Editor’s note: The ENST Catalina Island Internship at USC Dornsife is offered as part of a summer internship program offered to undergraduate students in the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island. Students investigate important environmental issues such as ecological restoration, protected-area planning and assessment, and invasive species management. During the course of the internship, students will work closely with USC faculty and staff scientists from the Catalina Island Conservancy to support ongoing conservation and management programs being implemented on the island. Instructors for the course include David Ginsburg, Assistant Professor of Environmental Studies, Lisa Collins, Lecturer in Environmental Studies, and Tony Summers, Invasive Plant Program Supervisor from the Catalina Island Conservancy.