The distribution of barite (BaSO₄) in marine sediments has long been studied as a proxy for paleoproductivity. While pure barite is known to be a stable mineral in oxic sediments, it is also known that variations in the Sr/Ba ratio influence its solubility and liability during early diagenesis. To extract...
The North Pacific subtropical gyre (NPSG), once considered to be a biological desert due to low primary production (PP) and its associated variability, has been found more productive and variable than previously thought. The environmental conditions controlling this relatively high PP variability are yet to be elucidated, despite important implications...
Biological di-nitrogen (N₂) fixation is a key process in open-ocean ecosystems, where the new nitrogen (N) provided by marine diazotrophs can support a large fraction of primary productivity and carbon (C) drawdown. Recent laboratory studies have shown that elevated pCO₂ enhances the rate of N₂ fixation by select laboratory isolates...
Under conditions of fixed N-limitation, as with most oligotrophic systems, the process of biological N₂ fixation (diazotrophy) is favored, provided the necessary trace elements and vitamins are sufficient. Despite the well understood contributions of N₂
fixation in oligotrophic regions, the nutritional and ecological controls of marine diazotrophs have not been...
Foundation species are important components of ecosystems because they provide habitat and ameliorate stressful conditions for residents. This thesis considers the role of surfgrasses (Phyllospadix spp.) as dynamic foundation species on the coast of Oregon in two studies. Chapter 2, which presents an observational survey of two Phyllospadix congeners, investigates...
Understanding and modeling microbial responses and feedbacks to climate change is hampered by a lack of a framework in the pelagic environment by which to link local mechanism to large scale patterns. Where terrestrial ecology draws from landscape theory and practice to address issues of scale, the pelagic seascape concept...
Many trace elements (e.g., Zn, Cd, Mo) are essential phytoplankton micronutrients, making them crucial to the marine ecosystem and ultimately the carbon cycle. Because of this association trace metals are also utilized in paleoceanographic studies (e.g., Mo, Cd). However, not much is known about what controls the cycling of these...
The influence of the physical environment on organisms has long been a subject of ecological research. But, the complex drivers of environmental variation, and the multiple scales at which this can occur, make studying this topic a difficult challenge. In rocky intertidal habitats, oceanographic- and climate-scale variability influence benthic communities...
The increase in modern atmospheric CO₂ concentration (360 ppm) from
pre-industrial levels (280 ppm) raises concern over the impact of anthropogenic
carbon dioxide input on atmospheric chemistry. For this reason, it is important to
understand the natural fluctuations of atmospheric carbon dioxide in the past. The
Vostok ice core record...