Growing human population in coastal areas within the last century has intensified the level of underwater sound pollution globally and consequently its impact on marine habitats. The increased complexity in the ambient underwater soundscape of the urbanized shoreline is due to the convoluted use of nearshore and coastal waters for marine related activities such as recreational and commercial boating, shoreline roads, and industrial and residential development. These uses impose stress on the ecological quality of nearshore habitats for Pacific Northwest fish during transit through urbanized waters. This study examined the characteristics of ambient sound sourced from traffic on the I-5 Bridge in Seattle, Washington near Portage Bay on February 12th, 2015. The soundscape was investigated through passive acoustic measurements of ambient underwater sound at varying distances from the bridge using two built hydrophones utilizing piezo elements and three professional grade hydrophones, in effort to prototype the built hydrophones and ensure quality data collection. The propagation and attenuation of sound from the I-5 Bridge characterized the potential for this point source of sound pollution to impact fish during transit. The variation in the acoustic spectrum at multiple distances from the bridge identified the spatial extent of preferential attenuation of frequencies and intensity of sound as a contributor to noise pollution. Fish utilize the canals connecting the Puget Sound to Lake Union and Lake Washington, where bridge noise pollution could be affecting their behavior during migration.

Plastic pollution in the ocean is a global issue that continues to grow as manufacturing and consumption of plastic products increases. Both macro- and micro-plastics are often difficult to discern visually, the latter requiring a microscope, which makes scientific quantification and identification challenging. The full range of plastic’s impacts on/to the marine environment is not completely understood, particularly in New Zealand waters where there is a lack of research on the subject. During the six-week Sea Education Association S-256 research voyage around New Zealand’s North and South Islands, 44 surface water samples were taken to measure microplastic (0.02 – 0.33mm particles) concentrations and 34 neuston net tows were conducted to collect macroplastics (0.33 – 5mm particles). Overall, plastic concentrations in New Zealand waters varied in density and polymer type. However, when compared to major gyre systems such as the North Atlantic and North Pacific, macroplastic and microplastic concentrations in this region were considerably lower. Macroplastics were limited in quantity. 29 total were found along the cruise track, primarily polyethylene and polypropylene polymers; these plastic types come from single-use packaged goods and fishing gear. Microplastic densities were greatest in regions where strong currents converge, suggesting that surface ocean plastic particles are transported by circulation processes. 2,923 microplastic particles were observed, the majority of which were filaments likely indicative of fishing gear. This marine debris may be attributed to relatively high fishing efforts in portions of the New Zealand Exclusive Economic Zone.

Non-traditional isotopes have become increasingly important as tracers for geological and environmental processes on earth. Recently, renewed attention has been direct towards potassium (K) isotopes given the abundance of K in the earth and the potential for significant mass-dependent fractionation between ⁴¹K and ³⁹K. There is little existing research on K isotopes primarily due to analytical difficulties, however recent technological developments have made precise analysis possible. Seawater has the potential to be an excellent geostandard for K isotope geochemistry because of predicted ⁴¹K/³⁹K homogeneity through the water column, and its wide accessibility around the globe. A total of forty-seven, 30 mL samples were collected in July 2015 aboard the R/V Thomas G. Thompson on the VISIONS 2015 Expedition to Axial Seamount on the Juan de Fuca Ridge. Samples were collected from CTD (Conductivity Temperature Depth) casts as well as niskin bottles operated by the Remotely Operated Platform for Ocean Science (ROPOS). Seawater profile samples were taken at several locations from 7 m down to 2890 m. Evaluating the K isotopic composition at each depth and geographic location will determine if the K isotope composition of seawater is homogeneous and therefore if seawater may be useful as a future geostandard. If K behaves similarly to other non-traditional isotope systems, ³⁹K will preferentially be released into the hydrosphere during weathering, leaving the residual rock enriched in ⁴¹K. This behavior will be useful in constraining the process of granite weathering, and its effect on the K budget in the hydrosphere. In chemical oceanography, there is thought to be a missing sink for K, and it is theorized that clay formation, crustal fractures, or both may remove K from seawater. Determining the feasibility of seawater as a geostandard for K isotopes will further facilitate new research in these and other geochemical topics.

For the past twenty years, scientists have attempted to learn more about the effects of pollution on coral species. However, identifying coral species in today's scientific community is more of an art than a science. For the last five years, researchers have been attempting to address this problem by comparing the skeletal structures of different coral species. Coral calcification is distinctive because it involves the formation of rapid aragonite super saturation. Aragonite is a very unusual form of calcium carbonate. It is much less thermodynamically stable than the primary form of calcium carbonate--calcite. There are two lines of thought as to why aragonite is preferentially precipitated in coral skeletons. One, the proteins secreted by the polyps within the coral create microenvironments that promote aragonite precipitation. Two, the magnesium from the surrounding ocean water interacts with the proteins in such a way that aragonite becomes the more energetically favorable precipitate. Our research examined the proteins and water involved in these calcification sites and compared them among species of coral collected from the Mo’orea Islands using Thermo Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Energy Dispersive X-Ray Spectroscopy (EDS) and Fourier Transform Infrared Spectroscopy (FT-IR). In short, we wanted to compare the magnesium, water content, and protein content/functional groups between species in the hope of finding species or site-specific trends. Our results confirmed the correlation between magnesium and protein, and discovered that the way in which corals create their exoskeleton is highly evolutionarily conserved.

Fronts are dynamic regions in the ocean where contrasting water masses meet, characterized by rapid currents, sharp density gradients and high productivity. What drives the phytoplankton community structure in these regions is still not well understood, but it has been hypothesized that fronts could act as either a barrier or a blender. However, few observations exist to test this hypothesis. The Kuroshio Front off the coast of Japan, extending eastward into the North Pacific Ocean, is an important western boundary current front, known to be important for fisheries. During a cruise in October of 2009, fine-scale sampling was conducted, and diatom and dinoflagellate phytoplankton taxa were identified to the species level by microscopy. Concurrent measurements such as salinity, temperature and chlorophyll were also taken to relate the physical and biological characteristics of the sample region. My analysis has revealed that distinct water masses found in the frontal zone have significantly different phytoplankton diversity indices. Conversely, I found that the most frequently observed and most abundant species in these water masses were remarkably similar. Major differences between the water masses were driven by the diversity of rare species. I show the importance of rarity in driving diversity and highlight the disconnect between the physically distinct water masses observed and the structurally similar phytoplankton community. My results reflect the importance of lateral mixing, mingling species from distinct source regions along the front. Rare species most likely represent the least competitive constituents of those original source populations. This research suggests phytoplankton may mix into new water masses diferent than their initial environment even if the water masses themselves remain physically distinct.

Marine microbes drive virtually every major biogeochemical cycle in the ocean. These microbial communities consist of two major groups: primary producers, called phytoplankton, that use energy from sunlight to transform carbon dioxide into organic matter, and consumers, like heterotrophic bacteria, that degrade about half of phytoplankton-derived organic carbon. Recently, it has been recognized that certain phytoplankton and heterotrophic bacteria form intimate relationships with one another and exchange specialized metabolites. This project has focused on characterizing such relationships between phytoplankton and bacteria, particularly between diatoms (a type of phytoplankton) and bacteria that enhance or deter diatom growth. These bacterial-diatom interactions impact rates of carbon fixation and nutrient flux in the ocean, and this project aims to better characterize the types and specificity of these interactions using laboratory cultures. To observe the effects of bacteria on diatoms, laboratory studies were conducted in which diatoms were exposed to individual bacterial strains in order to examine the specific effects of each strain on each diatom. In subsequent experiments, diatoms were exposed to multiple bacterial strains simultaneously in order to examine the impacts of multi-bacteria consortia and to create a more realistic model of the environment in which diatoms are exposed to many different types of bacteria.

Anthropogenic emissions are projected to double atmospheric concentrations of CO₂ by the end of the century, increasing ocean acidification and fundamentally changing the marine environment. Since diatoms are responsible for ~40% of marine primary production, it is important to understand their response to variations in CO₂ concentration and how they regulate their carbon assimilation. In previous work, we identified gene clusters with differential expression under elevated CO₂ in the model diatom Thalassiosira pseudonana. One cluster of genes that was down-regulated under elevated CO₂ encodes putative carbon concentrating mechanism (CCM) proteins, which participate in control of carbon assimilation. These genes share an upstream cis-regulatory motif involved in the regulation of CCM genes in Phaeodactylum tricornutum, a distantly related diatom that uses cyclic AMP (cAMP) as the second messenger. To test whether cAMP plays a similar role in CO₂-responsive gene regulation in T. pseudonana, we grew T. pseudonana under high and low CO₂ conditions and sampled cultures prior to or following exposure to 3-isobutyl-1-methylxanthine (IBMX), which raises intracellular cAMP concentrations. We have sequenced RNA from these samples and determined differential expression of genes between treatments. Contrary to our predictions, we find that most genes in the CCM sub-cluster are significantly up-regulated following IBMX treatment under high CO₂. We also identify a number of other gene clusters that are highly responsive to the IBMX treatment, suggesting other cellular processes under cAMP control. We are supporting this research with targeted metabolomics to look for changes in the ratio of cAMP:AMP and other key compounds between treatments. This research will facilitate mechanistic insights into diatom responses to changing ocean environments, and improve our understanding of the evolution of carbon concentrating mechanisms in this group of globally significant phytoplankton.