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- Creator:
- Pollak, Tania Nurith
- Description:
- Ischnura gemina, the San Francisco forktail damselfly (Family Coenagriortidae) is endemic to the San Francisco Bay area, and is identified by the International Union for Conservation of Nature as a vulnerable species. Research from the late 1970s through the 1990s indicates a decline in the species’ populations. This study completes a comprehensive survey for I. gemina, and the closely related species I. denticollis, to determine the status of both species in areas previously surveyed. The study also seeks to determine the extent that various habitat variables, such as water chemistry and vegetation structure, predict the presence of I. gemina. Data from this study show a dramatic decline in populations of I. gemina since the 1980s and 1990s. In addition, results from this study indicate that I. gemina persists in sites with cooler temperatures and lower salinity than do other ischnuran or coenagrionid species. Finally, this study considers past research related to species conservation in light of climate change, and assesses the long-term viability of I. gemina under climate change. Of key interest is the tolerance for I. gemina under increasing temperatures and sea level rise. The goal for this research is to provide information on the current status of I. gemina and recommendations for its long-term conservation.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Travis, Nicole Mayu
- Description:
- As a highly urbanized ecosystem, the San Francisco Estuary (SFE) has many wastewater treatment facilities discharging large volumes of high nutrient effluent into the estuary. Phytoplankton primary production can be depressed in the presence of ammonium-rich effluent, and ammonium tolerant phytoplankton species can become successful. The direct response of phytoplankton metabolic processes to anthropogenic nitrogen may play a key role in bottom-up structuring phytoplankton species composition and abundance in the lower Sacramento River, CA.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Fisher, Alison Christine
- Description:
- The giant green sea anemone (Anthopleura xanthogrammica) inhabits the rocky intertidal zone in California and Oregon. Two photosynthetic algal symbionts, zooxanthellae and zoochlorellae, make these anemones important primary producers in the intertidal zone. This study investigated the effects of changes in temperature and pH on anemones and their symbionts over a natural environmental gradient along the coast of California and Oregon. Zoochlorellae responded negatively to warmer temperatures and positively to more acidic conditions, while zooxanthellae responded positively to warmer temperatures and lower pH. Temperature and pH did not significantly affect chlorophyll a concentrations or anemone protein biomass. Depending on the magnitude of future changes in ocean temperatures and acidity, changes in the ranges of the two types of symbionts and increased densities of sea anemones in the rocky intertidal could be expected to occur.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Green, Kristen Marie
- Description:
- Movements of 23 sub-adult and 10 juvenile black rockfish (Sebastes melanops) implanted with acoustic transmitters were monitored during 16 months in Carmel Bay, California. Most tagged sub-adult black rockfish (14 fish) were resident to the study area (>75% time). The remaining 9 sub-adult black rockfish had low residency (<35% time). All tagged juvenile black rockfish vacated the study area within 3 months of release. When tagged fish were in the study area, mean activity space was < 0.4 km2. From October to May, sub-adult black rockfish during daytime moved to deeper waters offshore, returning at night. In the summer, diurnal movements of sub-adult black rockfish decreased, perhaps due to locally abundant food resources associated with seasonal upwelling. The black rockfish is currently managed with other nearshore, residential rockfishes, yet the complex movement patterns of black rockfish described in this study should be considered in a species-specific management plan.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Meyers, Morgan Teal
- Description:
- Four species of phytoplankton (Rhodomonas salina, Skeletonema marinoi, Prorocentrum micans, Isochrysis galbana) were grown under present-day low (400ppm pCOi, pH~8.1) and predicted-future high (lOOOppm pCOi, pH~7.8) ocean acidification conditions using nitrate-limited semi-continuous batch cultures. For four days, female Acartia tonsa copepods were fed a phytoplankton mixture from either the low or high pCC>2 treatment cultures. Phytoplankton fatty acid profiles were analyzed to assess changes in cellular essential fatty acid (EFA) content. Copepod egg production (EP), hatching success (HS), and egg viability (EV) were analyzed to assess differences in copepod reproductive success. Phytoplankton cultured under high pCC>2 contained less EFAs compared to phytoplankton cultured under low pCC>2. Female copepods fed high pCC>2 phytoplankton had lower EP, HS, and EV compared to females fed low pCC>2 phytoplankton. This laboratory study demonstrates that ocean acidification changes the nutritional quality of primary producers, which affects the potential reproductive success of fundamental primary consumers.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Ingman, Kaytlin Brooke
- Description:
- In the California Current System, baleen whales are used as a proxy for ecosystem health because they have been widely studied as a top predator. Oceanographic variability in the California Current System is dominated by three basin scale climate patterns, the Pacific Decadal Oscillation, the North Pacific Gyre Oscillation, and the Southern Oscillation which influence sea surface temperature, productivity, and upwelling. Humpback (Megaptera novaeangliae), blue (Balaenoptera musculus), and gray (Eschrichtius robustus) whales have been documented altering both timing of migration and switching prey when there are shifts in climate patterns. I hypothesized that both basin-scale climate and local oceanographic conditions would influence annual whale sightings and timing of arrival, peak, departure, and residency in central California. Using twenty-five years of weekly whale counts collected from Southeast Farallon Island, I developed two sets of regression models to test which environmental variables drive whale sightings and timings. I then developed a set of predictive models to determine if differences in sightings and timings could be predicted. I also compared sightings and timing to annual entanglement rates. There have been increased sightings in all species through time and variations are most commonly driven by sea surface temperature. Differences in timings are most influenced by El Nino events. Humpback entanglements are driven by whale arrival to central California, while, number of sightings drive gray whale entanglement rates. These models, and the continuation of long term monitoring, can be used to hopefully reduce the number of entanglements in central California.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Ceja, Alma Yesenia
- Description:
- Climate induced shifts in population distributions are widely documented around the globe as a means of animals behaviorally responding to their physiological tolerance limits. The rocky intertidal shore is known for its highly thermally variable environment within small elevational gradients, driving its exploitation in global warming research. I created an individual-based simulation to test a rule-based size-dependent species distribution model of a well understood population of Petrolisthes cinctipes crabs inhabiting the rocky intertidal shore of Fort Ross State Historic Park, California, which was then implemented to forecast the future distribution under the effects of warming. The model predicts the population will respond by shifting their distribution lower in the intertidal zone. This local distribution shift could result in significant ecosystem-wide community alterations. The generated simulation could be applied to similar systems of less tractable organisms responding to biotic and abiotic variables.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Barry, Shannon Noelle
- Description:
- Batoids exhibit unique body plans, with derived fin morphologies such as the anteriorly expanded pectoral fins that fuse to the head, or distally extended anterior pelvic fin lobes used for a modified swimming technique utilized by skates (Rajidea). The little skate (Leucoraja erinacea), exhibits both of these unique fin morphologies. These fin modifications are not present in a typical shark body plan, and little is known regarding the mechanisms underlying their development. A recent study identified a novel apical ectodermal ridge (AER) associated with the development of the anterior pectoral fin in the little skate, but the role of the posterior FIoxA genes was not featured during skate fin development. We present the first evidence for FIoxA expression (HoxA 11 and HoxA 13) in novel AER domains associated with the development of these novel fin morphologies in a representative batoid, L. erinacea. We found HoxA 13 expression associated with the recently described novel AER in the anterior pectoral fin, and HoxA 11 expression in a novel AER domain in the anterior pelvic fin that we describe here. Further, we found that HoxA 11 expression is associated with the developing fin rays in paired fins. Finally, we found evidence for the “distal phase” FIoxA expression in the developing claspers, suggesting a more complex Hox code than previously described during specification of these modified fin domains.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Lam, Emily Kathryn
- Description:
- Small-scale shifts in species distributions are expected to occur under future climate for many species. These shifts can have consequences as they alter population dynamics, and it is important to understand when and why they occur. The intertidal porcelain crab Petrolisthes cinctipes currently experiences temperatures that can reach near-lethal levels at low tide. However, the thermal thresholds that trigger migration to cooler microhabitats and the extent to which crabs move in response to temperature remain unknown. We tested for effects of body size and reproductive state on escape temperature (T e s c ) . In addition, we tested for the relationship between T eSc and the temperature of peak action potential firing frequency in nerve fibers. We found that both size and reproductive state influence behavioral sensitivity to temperature. Small crabs tolerate significantly higher temperatures before they move to cool refuges (a higher T eSc ) compared to large crabs. In addition, non-gravid crabs have significantly higher T eSc than gravid females. Tesc is positively correlated with peak neural performance of spontaneous action potentials. The vulnerability of marine organisms to global change is predicated by their ability to utilize and integrate physiological and behavioral strategies as a response to temperature, in order to maximize survival and reproductive fitness; understanding these strategies will allow predictions of species distributions under warming.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology
- Creator:
- Kalmbach, Andrew James
- Description:
- The Amazon River Plume (ARP) is a productive region of the Atlantic Ocean where riverine nutrients drive particulate productivity. A portion of the carbon produced by phytoplankton is released as dissolved organic carbon (DOC); this research investigated the effects of the ARP on the extracellular release (ER) of DOC. Particulate production (PP) and ER were measured during two cruises to the region, and were contrasted with salinity, dissolved nitrogen, and phytoplankton taxa and size. Chlorophyll normalized PP and ER were unaffected by size, and assemblages dominated by Trichodesmium sp. released a greater percentage of fixed carbon as DOC than sites mainly composed of diatoms. Salinity and total dissolved nitrogen (TDN) did not affect ER, but phytoplankton released a larger fraction of their total productivity at low TDN and high salinity. Particulate production correlated with total dissolved nitrogen, there was no effect of dissolved inorganic nitrogen on PP or ER, suggesting that the phytoplankton utilize the organic nitrogen pool in lieu of ammonium and nitrate.
- Resource Type:
- Thesis
- Campus Tesim:
- San Francisco
- Department:
- Biology