The biological transformation of dinitrogen gas (N2) into combined forms(termed N2 fixation) by certain genera of oceanic cyanobacteria represents the largest incoming flux of nitrogen to the global ocean. As such, biological nitrogen fixation
plays a significant role in the regulation of oceanic productivity and the export of
carbon and...
Three-dimensional ecosystem response to wind forcing on the continental shelf off Oregon is studied using a five-component nitrogen-based ecosystem model coupled to a high-resolution circulation model. We investigate, in particular, the influence of timedependent winds and alongshore variations in shelf topography for summer 2001 during the time period of the...
Summertime wind stress along the coast of the northwestern United States typically exhibits intraseasonal oscillations (ISOs) with periods from ≈15 to 40 days, as well as fluctuations on the 2- to 6-day “weather-band” and 1-day diurnal time scales. Coastal upwelling of cool, nutrient-rich water is driven by extended periods of...
We report the development of a numerical model simulating vertical movement of the
cyanobacterium Trichodesmium spp. Given a range of physiological parameters derived from the literature,
resultant model solutions allow us to explore the ecological significance of vertical migration
by Trichodesmium colonies in a stratified oligotrophic oceanic system such as...
Three-component (NPZ), four-component (NPZD), and five-component (NNPZD) nitrogen-based ecosystem models are compared. The fixed points of the zerodimensional systems, with no spatial variation except light attenuation by water, are determined. A linear-stability analysis shows that unstable steady solutions exist for all three models. Time-periodic solutions are found in these regions....
We conducted laboratory experiments to assess the bioelemental plasticity of cultures of Trichodesmium
IMS101 under phosphorus (P)-replete, P-restricted, and light-limited conditions. The results reveal a high degree
of stoichiometric flexibility. Specifically, Trichodesmium IMS101 is capable of growth with carbon (C) : nitrogen
(N) : P ratios of C₅₈₅±₅₆ : N₉₀±₁₀...
The behavior of three ecosystem models is analyzed for upwelling off the Oregon coast as a function of the number of model components. The first ecosystem model includes dissolved inorganic nitrogen-phytoplankton-zooplankton (NPZ), the second (NPZD) adds detritus, and the third (NNPZD) splits the nutrients into nitrate and ammonium. The models...
We hypothesize that the extraordinary maneuverability and efficiency of bats in flight are in part due to the compliant nature of their wing structures. We utilize the parameters of bat bones measured by biologists to create a biologically inspired model of a flapping system consisting of a rotating hub actuator...
Normal faults characterizing extensional provinces may terminate along-strike at regions of zero extension, at zones of transform faults, or at triple junctions. Termination of the Basin and Range extensional province in southeastern Oregon is thought to occur by right-lateral transform motion distributed across the Brothers Fault zone (BFZ) in central...
Thermohaline interleaving is an important mechanism for laterally fluxing salt, heat, and nutrients between oceanic water masses. Interleaving is driven by a release of potential energy resulting from the vastly differing diffusivities of heat and salt in seawater. The flows are composed of stacked intrusions that flux more buoyant and...