| Advisor : | JAMES NIEH | ||
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| Abstract Title : | Effects of a bee pathogen, Nosema spp, and a Relatively New Systemic Pesticide, Flupyradifurone, on Honey Bees (Apis mellifera L.) | ||
| Abstract : | The European Honey Bee (Apis mellifera) is a key pollinator for many native plants and agricultural crops. Bees have great importance in preserving the botanical ecology of many ecosystems along with the economic value behind agricultural production. It has been shown that honey bee health can be affected by the use of agricultural pesticides. A relatively new systemic pesticide flupyradifurone (Sivanto) was registered for use in the USA in 2015, and was described as safe for bees. However, the risk it potentially poses to honey bees in combination with other environmental stressors such as pathogens has not been investigated yet. Therefore, we tested the combined effects of flupyradifurone and a common bee pathogen, Nosema ceranae, on honey bees. N. ceranae is a common microsporidian and bee gut parasite that affects adult honey bees and causes Nosemosis, a condition often leading to negative effects on a honey bee’s survival, coordination, and behavior. In our study, bees were infected with sublethal doses of Nosema within 24 hours of their emergence, and were then exposed orally to field-realistic concentrations of flupyradifurone in their daily food consumption, simulating the bees’ exposure to flupyradifurone in their environment. We measured bee survival, daily food consumption, abnormal behavior frequency and Nosema spore load per bee. Preliminary results showed that flupyradifurone and Nosema individually reduced bee survival, yet there appears to be no combined effect between Nosema and flupyradifurone. ADDITIONAL PRESENTERS: Zhouran Ding, Jingshao Zhang. | ||
| Advisor : | JAMES NIEH | ||
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| Abstract Title : | The Effects of Sivanto on Honeybees Sucrose Response Threshold and Learning | ||
| Abstract : | This experiment was aimed at determining the effects of the pesticide Sivanto, produced by Bayer, on honeybee sucrose response threshold and learning. Bees are the natural pollinators of the world, and without them producing crops would be extremely difficult. By testing the effect on their sucrose response threshold, we could determine whether Sivanto changes the bees’ response to sucrose. This is important as a bee’s sensitivity to the “sweetness” of flowers influences whether or not the bee will collect nectar and pollinate those flowers. Additionally, we also tested whether or not Sivanto inhibits the bees’ ability to associate certain rewards with an odour. Initially we treated bees with either a negative control, or Sivanto condition, and their sucrose response was tested with various concentrations of sucrose ranging from .01-30M. When field realistic doses of Sivanto showed no significant effect on sucrose response threshold, the effect on learning was tested. We ran both acute and chronic trials, field realistic doses of Sivanto were used in both, and we conducted an additional acute condition with LD50 Sivanto to act as a positive control. The LD50 condition showed an increased mortality rate in bees, as expected. We then classically conditioned bees with a sucrose reward associated with an odour (Geraniol or Linalool). We conducted six acquisition trials in ten minute intervals to train the bees to associate the odour with a reward. Retention of learning was then tested, an hour after the last acquisition trial. Trials with both acute and chronic exposure were conducted for learning as well. We found no significant effect of Sivanto on honey bee sucrose response threshold or on learning, therefore in the next phase of this experiment we will be investigating the possible synergistic effects of Sivanto and Nosema (a common microsporidian honey bee pathogen) on honeybee learning. ADDITIONAL PRESENTERS: Annie Vo, Amanda Calimlim. | ||
| Advisor : | DR. JON SHURIN | ||
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| Abstract Title : | Zooplankton community structure across an elevational gradient in Yosemite National Park | ||
| Abstract : | Climate change is increasing temperatures across the globe, and even small changes in temperature have significant impacts on ecosystems. Characterizing changes in food webs along natural climate gradients allows us to quantify their sensitivity to temperature. To better understand the effects of climate change on food webs in California, I analyze zooplankton samples from lakes in Yosemite National Park for changes in biomass, size structure, and species composition along an elevational gradient. My research will determine variation among species and communities in relation to changes in temperature. | ||
| Advisor : | ERIC ALLEN | ||
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| Abstract Title : | Molecular methods for exploring diet and microbial ecology within the vast, unknown, twilight world of mid-water fish. | ||
| Abstract : | Mesopelagic fish make up a majority of the biomass of plankton-feeding fish, and are in turn an important part of the trophic layer as prey items for larger fish. Many mid-water species are diel migrators, escaping predation in deeper waters during the day, coming up to feed at night. These diel migrations are an important part of the carbon cycle, bringing carbon down from the surface and depositing it in the deeper waters. Despite their economic relevance and ecological importance, relatively few studies have investigated the biology of mesopelagic fish species. Mid-water fish are notoriously difficult to study, they are fragile when captured and cannot be studied in their environment. In order to address some of these limitations, work has been done on developing molecular methods to determine the microbial communities and diet items within mesopelagic fish. Samples of Sternoptychidae and Myctophidae were collected in a mid-water trawl. Representative samples of these fish were dissected, intestines removed, and DNA extracted for PCR amplification and sequencing. The 16S rRNA marker gene was used to determine and compare intestinal microbial communities between Myctophidae and Sternoptychidae. Additionally, work was done on establishing a reliable method of amplifying the CO1 marker gene for Illumina sequencing so that multiple diet items of midwater fishes might be sequenced and identified through ongoing barcoding projects/databases. The CO1 marker gene is a mitochondrial gene that due to a high rate of mutation is used to identify animals to species. For both the 16S and the CO1, methods developed required additional design of specialized host-specific primers to block host amplification while allowing non-target DNA to amplify. These host-specific primers have been extremely effective at blocking host DNA. In the next few months, a full sequencing run will be done in order to analyze the full communities, both microbial and prey, within these fish. | ||
| Advisor : | JENNIFER SMITH | ||
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| Abstract Title : | Photobiological responses of a common coral to natural gradients of light and inorganic nutrient availability in the Southern Line Islands, Kiribati | ||
| Abstract : | Nutrient over-enrichment from human based sources, coupled with declines in herbivore populations, has been implicated in the decline of coral reefs globally. However, few studies have examined how natural nutrient enrichment impacts corals in situ. Even fewer studies have been able to examine these factors on reefs free from additional threats (e.g. overfishing). The Southern Line Islands, Kiribati span a natural gradient of nutrient availability and contain some of the most pristine reefs in the world. We utilized this gradient to examine how the photobiology of a common plating coral, Montipora aequituberculata, responds to natural patterns of nutrient availability. Specifically, we asked if nutrient enrichment affects the relationship between light availability (i.e. depth), concentration of photosynthetic pigments, and density of the coral’s symbiotic algae (Symbiodinium spp.). Five coral colonies were sampled from 5-30 m every 5 m at Flint, Millennium, and Malden Islands, which span a range of ambient nitrate concentrations from 0.5-4.7 µmol. We used Symbiodinium to quantify chlorophyll-a concentration and symbiont density per coral, as well as the cell-specific chlorophyll-a concentrations. We found no significant of pigment concentrations or symbiont density with depth. Though both of these metrics had significantly larger magnitudes on Malden, which has the highest nitrate concentration. Interestingly, chlorophyll concentrations of individual Symbiodinium were similar at Millennium and Malden despite a 5-fold increase of nitrate availability on Malden. Our results indicate that nutrient enrichment does not alter patterns of coral photobiology with depth and that, in the absence of additional stressors, nutrient enrichment likely enhances the primary productivity of reef-building corals. | ||
| Advisor : | ELSA CLELAND | ||
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| Abstract Title : | Using the Tea Bag Index to Study Decomposition Within a Nutrient Addition Experiment | ||
| Abstract : | Decomposition of plant material is a fundamental ecosystem process, critical for nutrient cycling, and represents one such process that may be affected by anthropogenic sources of nutrient addition. Nutrient enrichment of ecosystems worldwide has profound impacts on a variety of ecosystem processes. In this experiment, we used the standardized methods of the Tea Bag index to understand how decomposition might be influenced by different nutrient additions. Commercially available bags of green and rooibos tea were buried in Elliott Chaparral Reserve (San Diego, CA) for 3 months. Different plots received nitrogen, potassium, and phosphorus nutrient additions, in all combinations. Mass loss of tea was calculated after the 3 month incubation period. We found that the green tea lost 1.73 times as much mass as the rooibos tea (p<0.001). The higher mass loss for green tea compared to rooibos tea could be based on the chemical composition of the tea. Green tea has lower C:-N ratios and a greater fraction of labile litter, which is likely more easily decomposed by soil microbial communities. The different nutrient treatments did not significantly affect mass loss. Water availability may have played a role in the lack of significant results regarding nutrient addition treatments. We confirmed that labile litter is more easily decomposed, but our results suggest that decomposition processes are not limited by nitrogen, potassium, and phosphorus in this context. The Tea Bag Index’s global scale enables researchers to build a more comprehensive understanding of soil decomposition, which has significant effects on nutrient cycling and other ecosystem services. | ||