The Hemigrapsus oregonensis population at Coquille Point in the Yaquina Bay Estuary on the Central Oregon Coast was studied from April, 1972 through May, 1973. The population was found to be vertically stratified from the 1 ft level to the 5 ft level. Population densities were found to be most dense in the upper regions. Greatest population density (about 20 crab/m²) was found to be in the 3-4 ft interval above MLLW (0.0 ft level). The population sex ratio was biased in favor of the females (53.3%) and did not vary appreciably during the year. The reproductive season, as determined by the percentage of berried females, was from February through May with a peak (32.8%) during March. Brooding females were found every month during the study, indicating a continuous, low level egg production throughout the year. A model for estimating potential egg production is given. The minimum carapace width of brooding females was found to be 0.86 cm. Biomass values were determined from carapace width measurements. A conversion equation is given. Biomass values generally increased as tidal height increased. The average biomass value for the area was 8.47 g/m². The average dry weight per crab decreased as tidal height increased, The average dry weight per crab at each tidal height (about 0.5 g) did not significantly increase during the study, suggesting a stable population. The average monthly production showed an over-all negative rate of -1.23 g/m² per month. No significant differences were found between tidal heights. The net production rate at each tidal height could not be shown to be different from a zero net production rate, again suggesting a stable population. Monthly distributional patterns indicated an high degree of population mobility. Crabs tested for locomotory activity patterns in the laboratory showed rhythms influenced by both the light regime and the tidal regime. Weak endogenous displays were found for a light component with increased activity during dark periods. Greatest activity generally occurred during dark-high tide periods. It is suggested that the locomotory activity patterns of H. oregonensis are influenced by both a tidal cycle and a light cycle. Under constant experimental conditions, the endogenous rhythmicity decayed within 3-9 tidal cycles and resulted in more or less continuous random movements. Only about 50% of the tested crabs, however, displayed an endogenous locomotory rhythm. / Graduation date: 1974

Graduation date: 1938

In the upper estuary of Yaquina Bay, Oregon, there is an annual population explosion of Acartia tonsa, (Dana) a calanoid copepod, during the months of July, August and September, followed by a rapid decline to virtual extinction in November. The restricted estuarine distribution affords an excellent opportunity to study the factors governing the population dynamics of A. tonsa without the disadvantage of potential mixing with other populations on different schedules of development. Field densities of A. tonsa during the 1972 summer were determined by twice weekly sampling with Clarke-Bumpus plankton samplers. In addition, explanation of the production of A. tonsa in the field was attempted by measuring the rates of egg production and development in the laboratory under temperature (21°C) and salinity (25‰) conditions comparable to those in the upper estuary. Daily egg production was found to be 30.5 eggs*day⁻¹*female⁻¹. The median rate of development from egg to adult required 11.5-11.6 days at 21°C in conditions of either laboratory cultured or wild food organisms. Mortality rates were substantial during the experiments as only 20-30% of the original populations survived to adulthood. The cause of mortality is not known but may relate to the molting process. In the field, six successive generations of A. tonsa were observed during the population explosion. The mean generation time ranged from 16 days in August to 19 days in October. A maximum density of 16,800 adults*m⁻³ in late August was followed by a crash to 2,100 adults*m⁻³ 10 days later. Predation and over exploitation of food resources are two possible causes of the crash. However temperature appears to be the major factor for the subsequent decline and disappearance of A. tonsa in the fall. This thesis presents the first results of ongoing research into the population dynamics of A. tonsa. / Graduation date: 1974

Large-volume (20-liter) bioassays were carried out in order to assess the effects of major nutrients and micro-nutrients on natural phytoplankton populations in water collected from a site close to the mouth of Yaquina Bay, Oregon. Seven long-term experiments were conducted during the years 1975-1976. A stripping technique employing activated carbon was used to reduce the trace metal and dissolved organic load of a portion of the water. Various combinations of major nutrients (nitrate, phosphate, and silicate) and micro-nutrients (trace metals and vitamins) were added to both the carbon-stripped and the non-carbon-stripped water in order to assess the effects of various nutrient substances on the growth rate, biomass yield, and species composition of the phytoplankton populations which developed from small natural inocula. The major nutrients and the micro-nutrients appear to have fundamentally different effects on the species composition and population growth characteristics of the phytoplankton. The micro-nutrients had marked systematic effects on the species composition of the phytoplankton populations which developed in the experimental vessels, while the major nutrients had minimal effects on species composition. The micro-nutrients appeared essential for the achievement of maximal population growth rates and minimal lags, while the major nutrients had no effect on growth rates or lags. Both the major nutrients and micro-nutrients had significant effects on the final biomass yields. There were seasonal variations in the control of final biomass yields by major nutrients and micro-nutrients. / Graduation date: 1977

A simplified autoradiographic method for estimating species-specific phytoplankton production rates in mixed natural communities was evaluated in the laboratory and employed in the field. Laboratory experiments were designed to test the reliability and variability of the simplified method. Assays of ¹⁴C uptake by liquid scintillation spectrometry were used to evaluate assays by autoradiographic silver grain counts. Linear relationships between the two assays were found for varying activities within a species. With corrections for radiation geometry and self-absorption, a linear relationship was obtained for species from 400 to 50,000 μm³ in cell volume. The coefficient of variation for microscopic grain counting at densities from 10 to 70 grains per 100 μm² was 4% of the mean. Counts of replicate autoradiographs from individual incubations yielded coefficients of variation of 7 and 14% for grain densities of 11 and 30 per 100 μm², respectively. The frequency distribution of grains deposited over different cells of a species with varying photosynthetic activities is indicative of the physiological state of the alga. Samples from five depths at one station in Yaquina Bay, Oregon were incubated in situ with ¹⁴C, daily from 2 April to 7 May 1974. Phytoplankton biomass during the spring bloom reached 7106 μm³ cell volume l⁻¹ and integral production reached 172 mgC m⁻² hr⁻¹. Total community carbon uptake increased with biomass during the study but species-specific uptake decreased as ambient nitrate + nitrite levels decreased. Species-specific production rates were estimated for 22 consecutive days: 16 April to 7 May 1974. Three taxa, Chaetoceros debilis Cleve, Thalassiosira decipiens (Grun.) Jorg., and unidentified flagellates were responsible for over 65% of the community biomass and over 85% of the primary production after 20 April 1974, Carbon-specific uptake rates were calculated for 20 species. Maximum carbon-specific uptake rates (expressed as the percent of the estimated cell carbon content assimilated per hour) for six abundant diatom species ranged from 111 to 158%, but average activity over the study period for 20 species was much lower. Carbon-specific uptake rates (% cell C hr⁻¹) averaged over all samples for the three dominant taxa were: Chaetoceros debilis, 22%; Thalassiosira decipiens, 21%; and flagellates, 54%. Flagellates were always two to three times more productive than the dominant diatoms on a carbon specific basis. Photosynthesis:biomass ratios (P/B) of the three dominant taxa decreased proportionately during the study The percent of total biomass and percent of total carbon uptake contributed by the three dominant taxa were proportional over the period studied. Average daily carbon-specific uptake rates demonstrate that Thalassiosira decipiens succeeded Chaetoceros debilis due to a change in their relative production rates. / Graduation date: 1977

Sediment was fertilized with f/2 algal growth medium in situ and in the laboratory daily for one week. Sampling strategy incorporated two intertidal heights and two sites. Experiments were done in August and January. No significant changes in chlorophyll a or diatom community structure were observed after ten days of growth in either the field or the laboratory experiments. Laboratory experiments also showed slightly increased gross primary production (p<.10) and increased oxygen uptake (p<.01) associated with nutrient enrichment. Unlike planktonic diatoms, sediment-associated diatoms in Yaquina Bay show no nutrient limitation. Thus other factors probably control diatom growth in these sediments such as light intensity, photoperiod, intertidal height, sediment stability and organic content, and animal consumption. / Graduation date: 1982

This research sought to identify the reasons physicians attributed for practicing in Oregon, the reasons for relocating out of Oregon, and the reasons for failures in recruiting physicians to Oregon. A random sample survey of 494 Oregon physicians identified the presence of economic and non-economic factors related to the recruitment and retention of physicians in Oregon. The research indicated that non-economic factors are overwhelmingly selected by physicians as reasons for locating their practices in Oregon, while economic factors are strongly selected as reasons for relocating out of Oregon, and as reasons for candidates not accepting positions. The data and research design do not provide the information needed to explain these divergent findings. The non-economic factor of Oregon lifestyle would appear to be a substantial recruitment asset as 93% of respondents selected "Oregon lifestyle" as an influential reason for locating their practice in Oregon. 86% of influential reasons to locate a practice in Oregon were non-economic factors. Economic factors were identified in 16% of respondents who reported planning to relocate out of Oregon within five years. The OHSU (2002) Workforce Assessment obtained a figure of 4% for this variable. This suggests future recruitment needs may be larger than anticipated. Physicians commonly contend with recruitment activities as 80% of respondents reported attempting to recruit physicians in the last five years. Of respondents reporting recruitment attempts, 69% reported at least one recruitment failure. Most of these failures were due to economic factors. While non-economic factors dominated the findings for reasons to locate in Oregon, economic factors dominated the findings for reasons to relocate and for recruitment failures. A full range of economic factors such as salary, reimbursement, liability premium costs, Oregon's economy were considered influential. Non-economic factors including lifestyle, collegiality, and family living in Oregon were influential factors identified in this survey. Much of recruitment theory is 'low-level', which appears as the ordinary organizing constructs for recruitment practices. As recruitment is largely an applied endeavor, recruitment theory is little developed and examined and is fertile ground for development and testing. / Graduation date: 2005

The sea as a dynamic conducting medium interacts continually with the earth' s magnetic field. The physical principles underlying this interaction are reviewed. These results are applied to the particular problem of towed electrodes at the sea surface. Data using this method are then shown to be sensitive to stability oscillations especially in lower latitudes. Finally, some features of the water velocity around the Panama Basin are investigated from towed electrode measurements. / Graduation date: 1970

Graduation date: 1980

During the summer and fall of 1982, personnel from the Geophysics Group in the School of Oceanography at Oregon State University conducted an aeromagnetic survey in the northern Oregon Cascades to assess geothermal potential and study the thermal evolution of the Cascade volcanic arc. Total field and low-pass filtered magnetic anomaly maps obtained from the survey data show high amplitude positive and negative anomalies associated with volcanic cones and shallow source bodies along the axis of the High Cascades. Spectral analysis of the aeromagnetic data yielded source depths and depths-to-the-bottom of the magnetic sources. The magnetic source bottom, in the northern Oregon Cascades, is interpreted as the depth to the Curie-point isotherm. The northern Oregon study area shows shallow Curie-point isotherm depths of 5 to 9 km below sea level (BSL) beneath the axis of the High Cascades from the southern boundary (44°N latitude) to near Mt. Wilson (45°N latitude). A smaller region of shallow Curie-point depths of 6 to 9 km BSL lies west of Mt. Wilson (45°N latitude, 122°W longitude). The shallow Curie-point isotherm suggests the emplacement of relatively recent intrusive bodies in the upper crust beneath the axis of the High Cascades and west of Mt. Wilson. A major northeast trending structure observed in magnetic and residual gravity anomalies near Mt. Wilson, is the northernmost. extent of shallow Curie-point depths and high geothermal gradients mapped in the northern Oregon Cascades. This northeast trending structure appears to mark a division between high intrusive activity in localized areas south of Mt. Wilson and intrusive activity confined beneath the major cones north of Mt. Wilson. / Graduation date: 1986