Interactions between lakes and their surrounding landscapes
Sonii Kollie - Retention Ponds as a Sink for Particulate Carbon and Nutrients. Mentors: Dr. Mike Vanni, Zoology and Dr. Bill Renwick, Geography.
Industrial process and industrialization are emitting an enormous amount of greenhouse gases into the atmosphere. Carbon (C) dioxide and methane, two carbon compounds, make up more than 70% of greenhouse gases. A C trading system is seen as a way to reduce emissions of greenhouse gases, and mitigate global warming. For this trading system to work the C budget must be accurately quantified, and to do this all of the sources and sinks of carbon must be studied. In the past it was thought that freshwater ecosystems played a negligible role in the C cycle. A study by Dean and Gorham (1998) estimated that freshwater ecosystems burial of organic carbon (OC) exceeds that of the Oceanic ecosystems. The OC sequestered at the bottom of freshwater ecosystems may be available for industries when a C trading system is implemented. For this research the percent, as well as the burial rates, of Nitrogen (N), Phosphorus (P) and OC was quantified in three freshwater reservoirs in the Four Mile Creek Watershed in Southwestern Ohio. The average particulate N was 0.26% (dry weight), ranging from 0.18%-0.37% in three ponds. The average particulate P was 0.051% , ranging from 0.048% - 0.055%. The average particulate OC was 1.88 %, ranging from 1.87%- 1.89%, our findings are very similar to the Dean and Gorham estimate of 2% made in 1998. The OC burial rate averaged 247 (g.m-2.yr-1), ranging from 209- 292, this is much lower than the 400 estimated by Dean and Gorham in 1998. It should be noted that there has been improved land management practices in recent years, such as conservation tillage, and this may account for why our findings are lower than the 1998 estimates. These results show that freshwater ecosystems do play a significant role in the C cycle, it also showed that land management practices should be considered when studying C sequestration in freshwater systems.
Kimberly Mace - Effects of Atrazine and Food Concentration on Male Production in Daphnia parvula. Mentor: Dr. Maria Gonzalez, Zoology.
Daphnia parvula, a common species of zooplankton, are the dominant crustaceans in Acton Lake (located in Ohio). Daphnia reproduce by cyclic parthenogenesis; typically relying on asexual reproduction, but if the environment becomes stressful, they resort to sexual reproduction. Because sexual reproduction produces resting eggs which typically don't hatch until the following season, population growth rates may decrease. Previous research on another species of Daphnia (D. pulicaria) showed atrazine caused production of excess males without a corresponding increase in sexual egg production (Dodson et al., 1998). This was hypothesized to further decrease population growth rate.
We hypothesized that male production would be impacted by the addition of atrazine. We predicted that male production would increase in the presence of atrazine (though no impact on ephippial production), and that population growth rate would be reduced with the addition of atrazine. We also predicted that the effect of atrazine would be the greatest in low food cultures because Daphnia invest more heavily in sexual reproduction under stressful conditions.
Resting eggs of Daphnia parvula were collected from Acton Lake in Ohio. They were separated into 17 separate clonal lines and raised through 3 generations before the study began. The F3 neonates were then divided into one of 4 treatments (with 3 replicates each): high food/no atrazine, high food with atrazine, low food/no atrazine, and low food with atrazine.
The addition of atrazine was not found to significantly impact the production of males in a Daphnia population. Also, population growth rate was not affected by atrazine, nor was there an amplified effect of atrazine in low food cultures. These results suggest that Daphnia parvula as a species are resistant to atrazine, or the population we studied was conditioned to it already (Acton Lake is often subjected to atrazine leaching from the nearby farmland). The overall population growth rate was also not affected by atrazine, indicating that perhaps it is not an environmental stressor on Daphnia parvula. The fact that none of our initial hypotheses or predictions were supported by the data open up exciting new areas to study.
Michael MacMillan - UV Radiation Toxicity and Fluoranthene Photoinduced Toxicity to Daphnia magna in Ohio Reservoirs. Mentors Dr. Jim Oris and Dr. Craig Williamson, Zoology.
The direct UV toxicity and photoinduced toxicity of fluoranthene to Daphnia magna was studied in single-treatment evaluations in a laboratory system under simulated sunlight (UV-A = 20 ± 4 W/m2, UV-B = 3 ± 0.4 W/m2) in water from 3 Ohio reservoirs. Five concentrations of fluoranthene (100, 400, 800, 1600, and 5000 ng/L) were achieved. Preliminary results show a relationship among UV toxicicty, fluoranthene photoinduced toxicity and the light attenuation coefficient (Kd), suspended solids (SS), dissolved organic carbon (DOC) and the percent agriculture of the watersheds. Regression analysis revealed that median lethal times (LT50) were directly related to Kd, SS concentration and percent agriculture and inversely related to fluoranthene water concentration. These findings demonstrate that site specific environmental parameters that affect UV penetration can determine the rates of mortality due to direct UV toxicity and photoinduced toxicity.
