Zooplankton are vital to the marine food web, supplying nutrients and energy from primary producers to secondary consumers. During Diel Vertical Migration (DVM), zooplankton travel between depth and the surface during day and night to capitalize on food and avoid predation. This study investigated diel differences in zooplankton community composition at two locations, one exposed and one protected, in the San Juan Channel, WA over four days in September 2023. Zooplankton were collected using net tows from surface waters at both sites during day and night times. Samples were analyzed using a stereoscope and different taxonomic groups were counted. Copepods were the most abundant zooplankton taxa at both locations, with mean abundances up to 1000 individuals per cubic meter. At the exposed site, there was a significantly higher (p<0.05) abundance of zooplankton at night versus during the day. The exposed site had significantly higher diversity than the protected site at night (p<0.05). At both locations, species richness was significantly higher (p<0.05) at night compared to day. The exposed location also had significantly higher richness (p<0.05) compared to the protected location during the day. Our results indicate that zooplankton abundance and diversity in surface waters of the San Juan Channel are controlled by DVM, and differences in locations perhaps due to exposure to different flow regimes. This study reinforces the flexibility of zooplankton community composition and emphasizes the importance of understanding factors that influence changes in the base of the marine food web.

Previous studies have found that jellyfish benefit from warming temperatures and eutrophication, resulting in large jellyfish blooms worldwide. However, the impact of warming ocean temperatures on the cross jellyfish, Mitrocoma cellularia, which are common in the Pacific Northwest, has been relatively unexplored. This study tests the hypothesis that warmer water temperatures would increase M. cellularia growth. A total of 36 individuals were collected from the UW Friday Harbor Laboratories Dock, San Juan Island in September 2023. They were observed in individual jars without water flow, and equally distributed across four separate temperature-controlled baths at 13°C, 16°C, 18°C, and 20°C. Over the 96-hour exposure period, they were fed excess live zooplankton collected before each feeding and had daily water replacements. Surface area was measured with ImageJ, mortality, and overall condition after the acclimation period (initial), day two (mid), and day four (final). A growth rate polynomial regression characterized the final measurements of normal condition jellyfish with a maximum closest to 16°C, resulting in an R2 =0.24 and p-value <0.05. At 20°C, shriveling and mortality increased. While 20°C decreased M. cellularia growth, our results support previous studies that jellyfish are resilient to impacts of climate change within the range of near-future prediction for the Pacific Northwest. Further investigations of the adaptability of M. cellularia to changing temperatures is necessary to understand the future outcomes of their ecology. Examination of this species can inform the state of a jellyfish ecosystem’s adaptability to climate change, which will allow further studies to create solutions to combat changing environments for ocean habitats.

The world’s oceans are witnessing a surge in plastic pollution, a consequence of human activities and the growing urbanization of coastal regions. Urban estuaries are complex habitats that are especially good at trapping sediment, carbon, and pollutants, such as plastics. However, our understanding of the extant of plastic accumulation within estuarine sediments remains limited. I determined the first quantification of the total amount of microplastics (>5 mm) in Puget Sound, WA – a heavily urbanized estuary – and identified deposition hotspots related to current hydrodynamics. To measure plastic concentrations, I collected both shoreline and shipboard sediment samples and density extracted microplastics using an NaI solution. Extracted plastics were counted, sized, and categorized under a microscope. To complement these plastic analyses, energy of the environment was determined using both grain size analysis and extraction of current velocities from LiveOcean, a hydrodynamic model of Puget Sound. I found that plastic concentrations are the highest near land-water interfaces, which are correlated with human population. The dominant source of microplastics came from fibers shed from clothing, giving a well-sorted particle size distribution. Furthermore, using the plastic concentration data I developed a predictive model of plastic distribution that relies on Puget Sound currents and could be adapted for other estuarine systems. Providing a comprehensive analysis of the sources and sinks of microplastics in main basin Puget Sound that can be used to inform preventative management on the negative impacts of urban waste.

Marine ecosystems are currently experiencing changes at unprecedented rates. Implementing camera technologies to visually monitor vulnerable marine ecosystems is becoming increasingly common. Images and video can capture a variety of biological indicators of ecosystem health including species abundances, ecological interactions, and individual health and behavior which can be challenging to assess in other ways. As massive amounts of high-quality photographic data are accumulating, the tools to analyze them are often not readily available to scientists. Therefore, collected images may not be analyzed at the timescales required for scientists to assess and respond to these rapid ecological changes. To address this, we have developed a series of machine learning models that can analyze this surplus of image and video data into meaningful insights for researchers. We built the Subaquatic Ecosystem Analysis and Population Estimation Network (SEAPEN) by meticulously labeling millions of images from oceanographic datasets using a model-assisted labeling protocol. Our original models began with human annotated models, but as accuracy and precision progressed, we were able to rapidly iterate and expand SEAPEN’s capabilities. The processed images are then put through our custom training framework and are run until they output trained TensorFlow and TFLite models. These models are then sent through a series of statistical tests and further quantized until they reach our high set of QA/QC standards. SEAPEN has been tested using a variety of image data from Ocean Observatories Initiative to accurately classify organisms at deep sea ecosystems. SEAPEN is also capable of assessing coral bleaching rates, estimating fisheries stock population size, and quantifying the presence of marine debris. By utilizing large amounts of previously unused public oceanographic data, SEAPEN helps put the tools necessary to process old and new ocean data quickly into scientists’ hands.

Marine sediments are a critical carbon reservoir, locking both inorganic and organic carbon in sediments for thousands to millions of years. This carbon is released in part through the production of methane at methane seeps, places where methane gas is emitted from the seafloor. In this study, I characterized source differences and quantified the amount of inorganic and organic carbon stored in Puget Sound sediments at a methane seep site. A multicorer collected sediment samples at two sites: one at the Alki Point methane vent field and a control site within the Main Basin of Puget Sound. The sediment cores were subsampled in 2 cm sections downcore and stored for later analysis. Analyses included physical parameters (grain size, percent loss on ignition (% LOI), and 210Pb sediment dating) and geochemical parameters (Total Organic Carbon (TOC), Total Carbon (TC), del 13C TOC, del 13C TC). Both sites were silt-dominated (Alki = 37 microns, Control = 30 microns), with a well-mixed layer 15 cm thick. Organic content (% LOI) was high at both sites (Alki = 7.5%, Control = 6.9%). Likewise, TOC and TC showed trends of increased organic material at the methane seep site. Isotope data indicate that methane-influenced sites have lighter del 13C. Given the amount of carbon they store and the potential for these reservoirs to be disturbed by bottom trawling, deep sea mining, and other invasive human activities, understanding how carbon is cycled through marine sediments is critical for preserving these reservoirs and adequately factoring their role in the carbon cycle into global climate models.

Protists are single-celled eukaryotic plankton that are abundant and diverse in the surface ocean. Many of these protist species are motile often through the use of flagella or cilia. The gene expression of protists is closely synchronized with the daily cycle of light (diel), particularly through the activity of photosynthesis-related genes. However, there has been little investigation of which motility-related genes are expressed in open-ocean protists, among which species, and whether motility-related gene expression is also coupled with the diel cycle. This study aims to investigate the hypotheses that motility-related genes are highly expressed in protist communities, particularly among mixotrophs, and that their expression is synchronized with daytime light. To investigate motility-related gene expression of open-ocean protists throughout the diel cycle, triplicate eukaryotic metatranscriptomes, within the 0.2 – 100 μm size fraction, were collected from 15-m depth approximately every four hours for three days at 158 °W, 41.6 °N, located in the North Pacific Ocean. We annotated protein families (Pfams) present in the metatranscriptomes with Gene Ontology (GO) terms. Pfams were selected based on GO terms related to motility, such as flagella, motility, and cilia. This approach resulted in the examination of the expressions of 21 motility-related Pfams.

In this study I examined the spatial distribution and concentration of various xenobiotic contaminants in the waters of the equatorial Pacific near American Samoa. Using state-of-the-art mass spectral techniques, I determined if pollutant loads increase near urban environments, as well as how individual manmade contaminants present spatially. I collected water samples in the region around American Samoa, then extracted pollutant chemicals from the sample via solid phase extraction using hydrophilic-lipophilic balance (HLB) cartridges and performed analysis of chemical concentrations using gas chromatography-mass spectrometry (GC-MS). This was followed by a detailed spatial comparison of the chemical pollutants. Industrial anthropogenic pollutants such as benzyl butyl phthalate and n-Tridecane were confidently found near the airport and fuel depot in American Samoa. Spatially, compound abundance was generally found to decrease moving away from urban environments. Assessing the spatial distribution of xenobiotic pollutants in relation to urban environments can help improve current understanding of how much manmade pollution is entering and persisting in the ocean, which can endanger ecosystems and human health.

Zooplankton are important primary consumers in the marine food web and lead an important role in carbon cycling in the open ocean. Understanding what influences zooplankton community composition can help us understand the impacts of climate change on this delicate relationship. Current research shows that zooplankton communities change based on currents and chemical cues, but there is a lack of data about the community structure of zooplankton in the Western Equatorial Pacific, specifically between 5°S and 5°N along 167°W. Data was collected from 28 December 2023, through 10 January 2024, on the R/V Thomas G. Thompson near American Samoa. A closing zooplankton net with 200μm mesh was used for net tows from 200m to surface at stations between 5°S and 5°N along the 167°W longitudinal line. Net tows were processed by counting and identifying zooplankton groups from subsamples and data was converted to abundance utilizing standard equations in RStudio. Zooplankton abundance increased from 5°S to the equator and decreased after the equator to 5°N. Species diversity (Shannon-Weiner) was lowest at the equator and highest at 5°N and 1°S. Calanoid copepods had the highest abundance over all sites, and north of the equator, calanoid copepods and gelatinous zooplankton (larvaceans) dominated most of the species composition. There were no significant relationships between species community composition and temperature, salinity, nutrients, or currents. With many processes occurring with zooplankton in the open ocean, it may be that multiple variables are impacting the resulting diversity and abundance relationships. Additionally, data was collected during the 2023 – 2024 Strong El Niño, which could have impacted the abundances and species presence due to higher water temperature and stronger currents. Monitoring zooplankton composition over time is vital for monitoring the health of our oceans as it has implications for global fisheries and carbon cycling.

Ocean salinity, a measure of salt concentration in seawater, is a key variable influencing water density and controls important processes like mixing and stratification. In dynamic coastal systems like Puget Sound, temporal and spatial salinity variability can present a challenge for making high resolution salinity measurements that can characterize these patterns. Salinity is typically measured using widely used conductivity cells, but they can be costly, provide spatially limited observations and can have technical limitations including drift and biofouling. This project therefore developed and validated a cost-efficient buoyancy-driven profiling float for the indirect determination of salinity for use in these dynamic coastal areas. The float is built from stock hardware and electronics, and 3D printed components. The float measures in-situ temperature and pressure through electronic sensors and determines water density at a given depth by achieving neutral buoyancy (e.g., float density equals water density). Neutral buoyancy is achieved by using a stepper motor to precisely move a piston to displace up to 6% of the float’s volume in water. Salinity is then calculated using the TEOS-10 equation of state using these three known parameters. This approach could enable the large-scale production of floats to obtain high-resolution data to better quantify patterns and change in dynamic coastal systems.

The paradigm for manganese (Mn) cycling in the marine environment has shifted over the past two decades to include not only the +IV and +II oxidation states. It is now recognized that dissolved Mn(III) can also exist when stabilized by organic ligands. Mn is critical for sustaining life and influences the cycling of many other bioactive elements. Because of this, further research is needed for understanding how Mn cycles in the environment, both between physical and chemical phases. My project aimed to look at how Mn cycles between dissolved and particulate phases and its three environmentally relevant oxidation states along the salinity gradient of the Mississippi River delta and what role organic ligands play in mediating Mn transformations. I hypothesized that the salinity gradient would influence the availability of organic ligands, which would promote the oxidation of dissolved Mn(II) and particulate Mn oxides (MnOx), making the cycling of Mn during estuarine mixing more complex than previously understood. To test this, I collected water from the Mississippi River and the Gulf of Mexico to conduct a mixing experiment to model the salinity gradient. UV-Vis spectrophotometry was used to analyze particulate and dissolved Mn speciation as well as the characteristics of the organic matter present. Inductively coupled plasma-mass spectrometry was used in analyzing dissolved Mn and Mn flocculants. Preliminary results show increases of dissolved Mn during mixing, and potential loss of particulate MnOx. Combined, these suggest redox cycling of Mn during estuarine mixing impacts its solubility and ultimately transport to the Gulf of Mexico. This region experiences heavy nutrient loading that leads to seasonal hypoxia. Understanding the cycling and solubility of Mn is imperative because it has broader implications for redox processes and element cycling in the Northern Gulf of Mexico, especially during hypoxic events.

Marine cyanobacteria have developed many genetic defenses in response to viral infection. Similar defense genes have been found in diverse groups of cyanobacteria, suggesting different modes of evolution for defense genes. Berube et. al (2018) identified novel cyanobacterial clusters of orthologous genes (CyCOGs), families of genes with similar genetic sequences. However many of these CyCOGs remain uncharacterized. The goal of my study was to characterize an uncharacterized CyCOG called 60001830, which is expressed in the marine cyanobacteria Prochlorococcus and Synechococcus, and when expressed is correlated with the genes of viruses that infect cyanobacteria (cyanophages). This suggests CyCOG 60001830 has an adaptive response to the presence of cyanophages, which would make it a family of defense genes. Using phylogenetic analysis, I resolved the evolutionary history of CyCOG 60001830 by comparing it to the evolutionary history of a key gene in host genomes. I compared the phylogeny of CyCOG 60001830 to the phylogeny of RecA, a highly conserved and essential gene present in all Prochlorococcus and Synechococcus species because of its key role in DNA repair and/or maintenance. CyCOG 60001830 does not share the same evolutionary pattern as RecA, which suggests that it does not follow a pattern of vertical gene transfer but rather horizontal gene transfer, genes being exchanged between neighboring bacteria. Viral defense genes evolve rapidly in an evolutionary arms race between bacteria and phages, so CyCOG 60001830’s evolutionary pattern makes sense as horizontal gene transfer operates faster than vertical gene transfer.

Nutrients and CO₂ are important oceanographic variables, as they provide information which can be used to understand phytoplankton abundance and processes such as the oceanic carbon cycle. Therefore, as climate change impacts ocean systems, it is increasingly important to measure how nutrient and CO₂ concentrations in the ocean change over time and space. This study measured pCO₂ (which takes into account temperature, total CO₂, salinity, and alkalinity of the water), nitrate, phosphate and silicate concentrations in the western equatorial Pacific (5S-5N along 167W) in January 2024. Over space, pCO₂ and nutrients were analyzed for correlation with physical processes, primarily upwelling, using sea surface temperature (SST) and mixed layer depth. To determine the relationship of pCO₂ and nutrient concentrations to the biomass of microorganisms, correlations with fluorescence and beam transmission were also analyzed over space. Over time, pCO₂ was compared to atmospheric CO₂ and El Nino Southern Oscillation (ENSO) state to determine correlations between temporal pCO₂ trends and atmospheric phenomena. pCO₂ surface concentrations in the western equatorial pacific were found to have increased from 1983 to 2024 at an average rate of 2.02 +/- 0.034 ppm/yr and had a positive correlation with increasing average atmospheric CO₂ (R = 0.71, p-value < 0001). Spatially, surface pCO₂ and the macronutrients nitrate, phosphate, and silicate in the upper 200 m showed similar patterns from 5S to 5N along 167W. The concentrations of nitrate and phosphate had a significant negative correlation to mixed layer depth (R = -0.4, p-value < 0.001) and nutrients and pCO₂ had a significant negative correlation to sea surface temperature (p-value < 0.001). They peaked from 0-2N due to upwelling and exhibited smaller secondary peaks around 3S and 3N, likely due to mixing caused by north and south subsurface countercurrents. These results reinforce the importance of physical oceanic and atmospheric processes as a control for nutrient and inorganic carbon cycles in the western equatorial Pacific.

Marine heterotrophic bacteria play a pivotal role in microbial community dynamics. This study aims to understand interactions within the microbial community of the oligotrophic (nutrient-poor) equatorial Pacific, specifically investigating how heterotrophic bacteria respond to the growth of autotrophic picophytoplankton. This experiment attempts to provide a more faithful representation of in-situ conditions, overcoming previous difficulties in capturing the dynamic behavior of microbial communities in the field. A novel methodology utilizing continuous chemostats with natural communities in the field accomplishes this objective. Three growth chambers were employed, two as chemostat systems and one in batch culture mode. All three growth chambers contained the natural microbial community that passed through a 3 µm pore-size filter. Chemostat systems continuously received 0.2 µm-filtered seawater (without microbes) while an equivalent volume was removed from the growth chamber simultaneously. Dissolved inorganic nutrients required by autotrophs – silicate, phosphate, and nitrate – were added to one of the chemostat’s 0.2 µm filtered media reservoir. This methodology was compared to a traditional batch culture, where nutrients were added to the growth chamber once, at time-zero. Cultures followed a 16-hour on/8-hour off light/dark cycle using LEDs, simulating the equatorial Pacific day/night cycle. Community responses were measured by continuous optical density measurements (OD), with endpoint subsamples analyzed for microbial abundance and DNA content using flow cytometry. Distinct day/night responses were observed in all cases, with the nutrient-enriched chemostat showing the most pronounced response. Overall, the results provide new insight into the linkages between marine autotrophic and heterotrophic microbes, while demonstrating an effective new methodology for examining microbial community responses to added nutrients. Thus, this study not only advances our understanding of microbial community dynamics in the oligotrophic equatorial Pacific but also introduces a novel experimental method that can be applied across a diversity of marine and aquatic environments.

Net primary productivity (NPP) is a major component of the carbon cycle. NPP is defined as the amount of carbon biomass produced by primary producers over a given period of time and area. The NPP exceeds 100 billion tons of carbon per year on Earth and half of it comes from the ocean through phytoplankton. The equatorial Pacific ocean is the largest tropical ocean on Earth and subsequently the largest oceanic source of CO2 to the atmosphere. Despite its importance, NPP in the west equatorial Pacific is poorly characterized due to the lack of data. Previous research suggests that strong upwelling is associated with increased nutrient concentration in the euphotic zone leading to an increase in primary productivity. However, the western equatorial Pacific is known for weaker upwellings compared to the eastern and central equatorial Pacific.This study was conducted aboard the R/V Thomas G. Thompson from December 28, 2023, to January 12, 2024, with the goal of identifying and quantifying the critical variables that have a substantial impact on NPP in the region including temperature, chlorophyll, dissolved nutrients, and current speed. NPP was measured using in-situ oxygen incubations, and was compared to NPP calculated from satellite data, which tend to typically overestimated or underestimated NPP in the region. Results of this study provide important information for refining satellite models to comprehend CO2 emissions into the atmosphere.

Protozoa are a diverse field of organisms that impact trophic transfer in marine ecosystems, constituting an important link between producers and higher trophic levels. In this study, I focused on determining how protozoan grazing rates differ in nutrient-rich and poor ecosystems. I used a CTD rosette to collect six seawater samples along the equatorial transect of five degrees south to five degrees north at stations: 5°S,2°S, 1°S, 0°, 1°N, 4°N, and 5°N. These samples were filtered to 10 microns and divided into isolated incubation cultures with 0, 25, and 90 percent dilution of 0.2 micron filtered seawater. Change in Chlorophyll was used to infer the phytoplankton growth rate across the dilution factors. Using a linear model of growth rate by dilution factor, a grazing rate was determined for each sample. Nutrients from the water samples were measured for nitrate, phosphate, and silicate concentrations. A series of linear regression analyses of the protozoan grazing rates by in situ nutrient concentrations were then done to determine the correlation between parameters. The growth rates of phytoplankton ranged from -5.2e-4 day-1 to 3.2e-2 day-1. Ambient nitrate, silicate, and phosphate concentrations reached 2.25 mM, 2.18 mM, and 0.46 mM respectively. Surface temperatures reached 30.46 centigrade, and the grazing rate exhibited a decreasing trend with higher temperatures, eventually reaching zero at 30.3 degrees. As eutrophication events become increasingly common due to climate change and anthropogenic pollution, it is important to determine how protozoan communities respond to changes in dissolved nutrients.

El Niño is an atmospheric-oceanic phenomenon characterized by the periodic warming of the sea surface in the eastern equatorial Pacific. Profiling data from Argo floats in the eastern equatorial Pacific is used for this research. An Argo float is an underwater profiling technology that can record and transmit real-time data of various ocean parameters at different depths. This technology supports the analysis of temperature, salinity anomalies, and other nutrients. In addition, a numerical model will be developed to simulate the progression of El Niño and evaluate its regional oceanic impacts. With both observational data and modeling output, this research aims to enhance the understanding of the dynamics of El Niño-induced impacts on oceanic parameters at a broader global scale. Based on the current data, I have discovered a clear variation in temperature and salinity according to the annual average. The El Niño Southern Oscillation (ENSO) indicator also suggests that the 2023-2024 El Niño is very strong and still in its development phase.
 

Oxygen deficient zones (ODZs) are large, naturally-occurring regions of the world's oceans where dissolved oxygen concentrations drop to low levels—less than 10 nM. These regions are important to the biogeochemical cycling of carbon, nitrogen, methane, and sulfur and are expected to expand as ocean temperatures rise due to anthropogenic climate change. Located above and below the anoxic ODZ core are oxyclines where dissolved oxygen concentrations change rapidly with depth. The deep oxycline extends into the deep ocean supporting an understudied microbial community adapted to these low-oxygen conditions. In this study, I examine a metagenomic library previously generated from a water sample collected at 1000 meters on the RR1804 POMZ cruise to determine both the diversity and genetic potential of microbes in the deep oxycline. I found that three groups of prokaryotes dominate in the deep oxycline: the cosmopolitan alphaproteobacteria, Pelagibacter ubique (20%); the uncultured candidate phylum SAR324 (16%); and archaea of the phylum Thaumarchaea (12%). I generated metagenome-assembled genomes (MAGs) from this sample to determine the genetic potential of this microbial assemblage. By examining these MAGs, I expect to find genes encoding for processes such as low-oxygen stress responses, alternate terminal electron acceptors, and carbon-fixation pathways. By better understanding the contributions of the deep oxycline microbial community to biogeochemical cycles, we can more accurately predict how nutrients will be consumed and regenerated in ODZs as they expand.

The SAR11 clade are composed of one of the most abundant groups of marine bacteria, composing up to a quarter of planktonic cells in marine environments. These bacteria play important roles in marine biogeochemical cycles. Because they are challenging to culture in the laboratory, they remain understudied, with few publicly available complete genomes. Most of what is known about the genetic diversity of this group comes from metagenome-assembled genomes, which do not capture the full genetic diversity within the group. Our project aims to use non-traditional methods to culture SAR11 isolates from the marine environment and use them for whole genome sequencing. We hypothesize that this work will reveal unidentified genetic diversity within the SAR11 group. This research will yield insight to the genetic and phylogenetic diversity of SAR11 bacteria through the examination of whole genome sequences, and will support future research on this globally important group of bacteria by greatly expanding the number of publicly available complete SAR11 genomes.

Phytoplankton play a pivotal role in marine ecosystems by providing essential nutrients and energy to heterotrophic microorganisms through the release of low molecular weight (LMW) metabolites into the dissolved organic matter (DOM) pool. Ectoine, a compatible solute primarily sourced from bacteria, acts as a safeguard against osmotic stress. In this study, we investigate the intricate interaction between phytoplankton and bacteria consumers by comparing the growth dynamics of two diatom species, Thalassiosira pseudonana and Thalassiosira oceanica, in the presence of ectoine. Cultures of T. pseudonana and T. oceanica were cultivated under axenic, controlled conditions, and their growth was monitored using measurements of relative fluorescence units, cell enumeration techniques, and metabolomics analysis. Our hypothesis suggests that samples with ectoine will exhibit higher metabolite abundance and growth rates compared to those without. Through a comparative analysis between cultures supplemented with ectoine and those without, this research endeavors to shed light on producer-consumer interactions within controlled laboratory settings, offering valuable insights in the complex microbial dynamics prevalent in oceanic environments.

The estuarine dynamics of Puget Sound, (Washington, USA) are complex, with high spatial and temporal variability, influenced by factors that control the circulation and mixing of offshore and estuarine waters. However, determining these mixing impacts on a smaller scale can be difficult. Colvos Passage, a distinctive and understudied passageway of Puget Sound, is unlike other channels because surface currents remain consistent in direction regardless of the tides. Here, we investigate mixing in Colvos Passage as water flows into the main basin of Puget Sound during different tidal cycles using Seagliders. We conducted repeat surveys using Seaglider CTD data and fixed position CTD casts at different tidal cycles throughout the winter of 2023-2024. We measured temperature, salinity, and density from Seaglider transects to track the body of water as it exits Colvos Passage into the main basin and provide insight into the complexity of estuarine mixing and circulation. Preliminary results suggest that the body of water in Colvos Passage is well mixed throughout the progression of the tidal cycle facilitating the tracking of this water mass into the main basin. This study is the first from the University of Washington’s new Student Seaglider Center (SSC), a student-run laboratory where students gain valuable experience in testing, deployment, piloting, and scientific planning of refurbished Seagliders. The SSC continues to build on this study to understand circulation in Puget Sound which can support local forecasting and effective pollution mitigation strategies.

Marine microbial communities produce and cycle organic matter in the ocean. Some of this organic matter is in the form of metabolites, small, organic biomolecules that are present both inside of microbial cells and dissolved in seawater. Studying metabolite dynamics provides insights into the fate of a significant portion of marine primary production as well as microbial community interactions that influence short and long term carbon storage in the ocean. Here I analyzed both dissolved (extracellular) and particulate (intracellular) metabolites from the 2019 Gradients 3 (G3) research cruise that were collected along a latitudinal transect. Sampling stations spanned the North Pacific Subtropical Gyre, an area with low nutrients and primary productivity, to the North Pacific Subpolar Gyre, an area with higher nutrients and primary productivity. I extracted particulate metabolites using a modified Bligh and Dyer extraction and dissolved metabolites using cation-exchange solid phase extraction. I acquired metabolite data using liquid chromatography mass spectrometry and processed the data using Skyline software. In both dissolved and particulate samples, metabolite pools were dominated by compatible solutes, compounds organisms use for handling osmotic stress, as well as amino acids. Metabolite abundances in both phases largely increased traveling northwards along the transect, reflecting increases in productivity, microbial biomass, and nutrients. However, certain metabolite concentrations did not follow this trend, suggesting that differences in microbial community composition or physiology may play an important role in regulating the synthesis of these compounds. These results show how varying environmental conditions affect the composition of organic matter produced by marine microbial communities. This information can be used in to predict how marine primary producers will store and use carbon in a future changed ocean.

Located in the Southern Pacific Ocean, American Samoa was formed nearly 400 thousand years ago due to hotspot volcanism. As these eruptions occur, ash and volcanic rock fragments settle and leave behind texture, roughness, and clast sizes that are identifiable using mapping techniques such as backscatter analysis. The 2024 Oceanography Senior Thesis cruise aboard the R/V Thomas G. Thompson, produced bathymetric and backscatter maps utilizing the Multibeam Kongsberg EA302 to identify the boundary of such deposits and the thickness of sediment that has been deposited on it, indicating relative age and formation of volcanic features on the seafloor. This study focused on the islands Ofu-Olosega and Ta’u, and we located several intact and exploded cinder cone. Sediment cores were collected to quantify the grain size of the basalt that erupted violently out of these hot spots. We hypothesized that the grain size would correlate with distance from the caldera, with larger clasts sinking closer to the eruption site, and fine sediment carried farther. This was found true, but there were also large grain sizes radiating away from the initial cinder cone site, indicating the presence of other eruptions on the seabed. Multiple landslides were documented on the southern and northeastern slopes of Olosega Island. These landslides display key features such as steep amphitheater headwalls, blocky ridges, and hummock aprons. The landslides were classified as either slumps or debris avalanches based on these characteristics and compared to other volcanic hotspot landslides within the Pacific region. We hypothesized failure deposits would be identifiable in the seabed up to 30 km away from the caldera, and found them to be graphically obvious for about 21 km.

Vertical velocities are a fundamental component of ocean flow and are vital to characterizing global circulation. However, vertical velocities are small compared to horizontal velocities and are thus difficult to measure. Previous studies attempting to estimate them ignore the impacts of topography, mesoscale eddies, internal waves, and spatial variability. Novel estimates from the Argo float array allow for direct estimates of vertical velocities. This project will focus on comparing these new Argo estimates with vertical velocity observations from moorings in the Southern Ocean. The Southern Ocean is an important site of vertical volume transport for mass ocean circulation with global implications, particularly the Antarctic Circumpolar Current which dynamically links many of these interactions. We expect vertical velocity characterized by moorings to maintain coherency with Argo float estimates. Differences may occur, however, due to mismatches in spatial resolution between Argo-based estimates and mooring-based estimates, which rely on mass conservation across larger scales. In comparing novel Argo datasets to known mooring values, we gain a more complete understanding of vertical velocities in the Southern Ocean which have direct implications for data assimilation in models and parameterization of energy pathways.