Deep mixing events in the ocean’s surface layer act as physical drivers of carbon export by detraining dissolved and particulate organic matter, including surface phytoplankton communities, to depth. Once removed from the sunlit surface ocean environment, phytoplankton accumulation rates are dependent on the relative contributions of loss processes, such as...
Iron (Fe) is an important limiting nutrient that can affect the rate of ocean primary production because it is required by phytoplankton as an enzymatic cofactor in photosynthesis, nitrogen fixation, and other essential metabolic functions. Most Fe reaches the surface of the open ocean via atmospheric dust deposition, which is...
We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes prognostic tracers for the stable nitrogen isotopes, ¹⁴N and ¹⁵N, in the nitrate (NO₃ˉ), phytoplankton, zooplankton, and detritus variables of the marine...
In ecological restoration, species that are sown to increase the native plant
diversity range in establishment ability. Some species readily establish, while others
rarely do. This study set out to investigate some of the potential processes influencing
species establishment, as well as the traits that are associated with the success...
Secondary metabolites (SMs) play an integral role in the life history of most fungal species. Fungal metabolomic studies provide insights into how fungi perform certain ecological functions, how they compete and interact with other organisms, and the breadth of fungal chemodiversity. Fungal SMs have also been utilized for a variety...
Photosynthetic energy allocation strategies were investigated in the marine diatom, Thalassiosira pseudonana, grown under a wide range of light limitation. Steady-state, continuous cultures were established at three light-limited growth rates. Simultaneous measurements of photosynthetic activity were made that targeted different points in photosynthetic energy flow from gross to net photosynthesis....
The Fukushima Daiichi nuclear disaster of 2011 made it apparent that releases of fission products to marine environments is a very real possibility. Additional data on the movement of material through marine environments can be used by radioecology personnel to assist with both ecosystem protection as well as environmental cleanup...
Few studies have examined the partitioning of organic matter in upwelling systems,
despite the fact that these systems play a key role in carbon and nitrogen budgets in the
ocean. We examined the production and partitioning of phytoplankton-derived organic
matter in deck incubations off Oregon during the upwelling season. During...
The demand for the development of sustainable energy is an all time high as we burn through limited fossil fuel reserves and as environmental concerns rise every year. Renewable energy sources such as wind and solar power have limitations due to inconsistent power supply that cannot meet the regular needs...
The grand plan of carbon neutralization and COP26 in Glasgow require a quick shift of energy sources from conventional fossil fuel to a more renewable substitute such as wind, or solar energy. However, the intermittency of those renewable energy sources does not meet the demand of the energy, which requires...
Microscopic organisms inhabit virtually every niche on this planet, where they perform functions vital to all life on earth. Accordingly, humans host a complex community of microorganisms (i.e. the gut microbiome) that inhabit the gastrointestinal tract and modulate host physiology. Insight into the specific mechanisms through which gut microbes influence...
The Southern Ocean plays an important role in the ocean’s uptake of heat and carbon yet the processes controlling this uptake are not well understood. To date, more than 100 biogeochemical profiling floats that measure water column pH, oxygen, nitrate, fluorescence, and backscattering at 10-day intervals have been deployed throughout...
In this dissertation, I present the results from three studies: (1) a phylogeny of Tenebrionoidea (Coleoptera) inferred from a seven-gene dataset derived from PCR and Sanger sequencing; (2) a phylogeny of Tenebrionidae, the largest family in Tenebrionoidea, inferred from a four-gene dataset also derived from PCR and Sanger sequencing; (3)...
Ocean Acidification (OA) has emerged as a major threat to marine ecosystems, particularly regarding calcifying organisms. A growing body of literature describing laboratory investigations into pH stress indicates broadly deleterious effects for calcifiers, but responses vary greatly across taxa and can be influenced by variations in other environmental characteristics. Scaling...
Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's disease, a chronic inflammatory bowel disease that affects ruminant populations worldwide. The characteristic stages of the disease make diagnosis difficult, resulting in silent transmission among animals in a herd for years before proper detection of the infection. The extensive...
In situ optical measurements of spectral absorption and beam attenuation provide information on the fine scale horizontal and vertical variations in phytoplankton pigments and other measures of phytoplankton photophysiology and ecology in coastal waters. Phytoplankton pigment ratios from discrete sample analyses with High Performance Liquid Chromatography were compared to in...
Marine bacterioplankton play an important role in global elemental cycles because they return carbon dioxide and nutrients to the biosphere as they reduce organic matter. Furthermore, marine bacterioplankton are not uniformly active, and subpopulations of the in situ community may be more or less active at any given time. Defining...
Ecosystems are facing increasing threats from human related activities, such as overfishing, pollution, habitat destruction, species invasions, and diseases, among others. While oceanic islands provide natural laboratories to understand ecological and evolutionary process, they are also particularly vulnerable to these impacts, given their usual isolation from the mainland and the...
Oceanic crust covers nearly 70% of the Earth's surface, of which, the upper,
sediment layer is estimated to harbor substantial microbial biomass. Marine crust;
however, extends several kilometers beyond this surficial layer, and includes the
basalt and gabbro layers. In particular, the basalt layer has high permeabilities which
allows for...
Modern upwelling conditions and corresponding oceanographic properties are investigated and reconstructed for the Late Quaternary. The oceanographic conditions considered influence diatom ecology and the record of fossil diatom frustules in the sediments.
Diatoms from modern sediments are evaluated as paleoceanographic proxies and transfer functions (TFs) are calibrated using the Imbrie...
Pseudomonas aeruginosa is a ubiquitous environmental microbe, opportunistic pathogen, and a highly social organism. P. aeruginosa utilizes a wide array of cooperative behaviors to adapt to the environmental conditions around it. These behaviors include quorum sensing (QS), a form a cell-to-cell signaling that coordinates the expression of secreted products in...
Plant-parasitic nematodes cause more than US $100 billion in annual agriculture loss worldwide. Thorough knowledge of their genetic diversity, and interactions with endosymbionts and environment have the potential to provide valuable insights into the basic biology of these animals, and assist future efforts aimed at management of these plant parasites....
Marine bacteria play vital roles in every niche of the ocean, from small-scale symbioses to large-scale productivity and the regulation of Earth’s climate. Recent advances in molecular tools now allow us to probe the genetic potential of entire microbial communities. The next step is linking these diverse communities to the...
The influence of mesoscale ocean eddies on near-surface ocean temperature, surface stress and phytoplankton communities is investigated by collocating numerous satellite measurements along with vertical profiles of oceanic temperature and salinity to the interiors of eddies identified and tracked in altimetric sea surface height maps.
The surface currents associated with...
Experiments were designed to answer key questions about diatom-derived organic matter cycling (i.e., production and degradation) in coastal systems. Dissolved organic matter (DOM) production was examined in axenic batch cultures of five diatom species. Dissolved organic carbon (DOC) release rates varied between species, but were significantly higher for all species...
Previous observations of light levels and phytoplankton abundances along the Oregon coast demonstrated that phytoplankton attenuated light sufficiently to potentially limit the growth of intertidal macrophytes and therefore structure local intertidal communities. Inspired by this observation, in spring 2004, I initiated a study to quantify the direct and indirect benthic...