Gray Franey
Biology & Chemistry major, Oregon State University
CEOAS mentors: Kristen Buck and Ilana Farrell
Alive or Dead: Diatoms as a Source of Electroactive Organic Ligands in the Southern Ocean
As an essential micronutrient to phytoplankton, iron plays a large role in carbon cycling, but is found in trace amounts in the ocean due to its low solubility. Iron is the primary limiting nutrient in the Southern Ocean. The presence of iron-binding organic ligands (Lelec) in seawater determines its solubility, but it is unknown where these ligands come from. Here, we compare the effects of alive vs dead diatom presence on iron solubility. Ice samples, where there are more living diatoms present, and porewater and overlying water samples, where there are more decaying diatoms present, were collected from stations in the Southern Ocean, on the Amundsen Sea continental shelf. Data was analyzed via adsorptive cathodic stripping voltammetry, then compared to existing surface water data from the same location. This showed the highest total Lelec concentration and iron-bound Lelec concentration in overlying water and porewater, and the highest excess, not iron-bound Lelec concentration, in surface water and sea ice. These results were compared to surface water data from off the Oregon coast, which mirrored the results from Southern Ocean surface water and ice. Chlorophyll data from the same cruise showed a correlation between high phytoplankton biomass and high total Lelec. This supports the idea that both alive and dead diatoms produce Lelec, but the presence of alive diatoms prevents binding to iron. It also suggests Lelec is important to stabilizing iron.
Matthew Goh
Physics major, Amherst College
CEOAS mentors: Greg Wilson and Andone Lavery
Ultrasound Phased Array Flow Imaging for Nearshore and Sediment Applications
Sonar is one of the few field-successful methods of measuring nearshore sediment flux rates. Current instruments are capable of determining sediment concentration and velocity of a single vertical profile. While these devices can resolve vertical and time dependence at turbulent scales, they cannot currently capture horizontal gradients, which are hypothesized to have important implications for wave driven sediment transport. Previous research has shown potential promise towards implementing phased array acoustics into nearshore studies, which can acquire data over a spatially extended region with multibeam imaging. Existing phased array medical ultrasound technology offers an accessible way of implementing such a system, capable of imaging a large spatial region with high resolution and at frequencies relevant to flow-sediment imaging. Here, we demonstrate an application of this technology, utilizing pulse coherent Doppler techniques with a phased array transducer to measure radial velocity and backscatter amplitude with 1.5 by 2.5 mm spatial resolution and 40 Hz temporal resolution. Experiments are shown measuring sediment velocity and concentration in a sediment-laden, turbulent jet, which suggest the feasibility of using medical ultrasound technology in the field to image nearshore processes.
Paige Heinemenn
Climate Science major, Oregon State University
CEOAS mentor: Andrea Jenney
Investigating Tropical Radiative Anomalies During Unforced Dansgaard-Oeschger Events in CCSM4 Simulations
Abrupt warming periods during the last Ice Age have been linked to changes in the distribution of heat within the Atlantic Ocean. In CCSM4 simulations, warm interstadial periods are accompanied by enhanced outgoing top-of-atmosphere (TOA) radiative anomalies in both the northern high latitudes and the tropics. The tropical anomalies have distinct physical causes, but their contribution to the Earth’s interstadial energy balance have received less attention than the North Atlantic response. Climate model output from CCSM4 was analyzed using maps and zonal-mean graphs of TOA radiative fluxes, cloud properties, temperature, precipitation, and water vapor. The equatorial radiative anomaly is associated with cloud changes, whereas the southern hemisphere tropical anomaly is associated primarily with changes in water vapor and temperature. In Equatorial Africa, increases in low- and middle-level cloud fraction enhance reflected shortwave radiation, while over the mid-Atlantic, decreases in higher-level cloud fraction increase outgoing longwave radiation. In the southern hemisphere tropics, increased temperature accounts for approximately two-thirds of the clear-sky outgoing longwave radiation anomaly near 15°S, with decreased water vapor accounting for the remainder. These results demonstrate that similar radiative anomalies can arise from different atmospheric processes and highlight the importance of clouds and water vapor in understanding abrupt climate variability.
Elise Heppell
Physics and Math major, St. Lawrence University
CEOAS mentors: Jesse Cusack and Vanessa Hawkins
Calving-induced wave generation and energetics at a marine-terminating Alaskan glacier
Sea level rise is accelerating and threatens about one billion people who live near the coast, but climate projections of future sea levels are uncertain. Glacial mass loss is responsible for a majority of sea level rise to date, but observations that clarify near-glacier processes are difficult to obtain in the challenging environment. One such source of error is submarine melting at marine-terminating glaciers. Internal waves, a recently observed ocean process at marine-terminating glaciers, may influence submarine melting. Internal waves can be generated from turbulent subglacial discharge plumes, as well as submarine or subaerial calving events, but little research has been done on whether the characteristics of internal waves vary based on source. An algorithm was constructed to analyze near-glacier velocity and pressure data in the fjord, select potential calving events based on standard deviation of pressure, and filter velocity data for signals of internal and surface waves. We found that these events are often associated with internal waves of 5-10 minute periods, surface waves of 37.5 second periods and increases in kinetic energy for each wave type. We were unable to observe a clear difference between submarine and subaerial calving events due to a small sample of confirmed calving types. Since potential melt effect via calving-induced internal waves is only beginning to be recognized, more work should be done to a) identify calving events from data signatures, and b) understand how and whether different types of calving events impact internal waves.
Kendra Moses
Zoology major, Oregon State University
CRITFC mentor: Rosie Gradoville
CEOAS mentors: Maria Kavanaugh and Kelly George
Comparing Community Composition of Phytoplankton and Tidal Cycles in the Columbia River Estuary
Tidal mixing affects estuarine water properties and may influence phytoplankton communities that support copepods and juvenile salmon. We compared phytoplankton community composition during high- and low-tide conditions at Point Adams and Tongue Point in the Columbia River Estuary near Astoria, Oregon. Water samples collected in June 2026 were analyzed using an Imaging FlowCytobot (IFCB), and plankton images were reviewed and annotated in the Tiamat data platform. Diatoms were common across samples, including Asteroplanus, Bacillaria, Leptocylindrus, Skeletonema, Thalassiosira, Guinardia, and Rhizosolenia. Ciliates, dinoflagellates, and zooplankton material were also observed. The Point Adams high-tide surface sample showed the greatest apparent diversity of plankton groups, while other samples were dominated by diatoms and ciliates. These preliminary results suggest that tidal stage may influence phytoplankton community composition in the Columbia River Estuary. Expanded quantitative IFCB monitoring could clarify how these communities vary through time and contribute to salmon-supporting food webs.
Emily Olivares
Mathematics major, California State University, Stanislaus
CEOAS mentors: Lorenzo Ciannelli and Juan Gutierrez Bravo
The Oceanographic Spring Transition of the Northern California Current and its Influence on Local Larval Decapod Assemblages
The distribution and survival of planktonic decapod larvae are strongly influenced by oceanographic conditions along the Oregon Coast, particularly during the seasonal spring transition. These environmental conditions affect larval transport, and recruitment of Oregon’s major economically important fisheries, such as Pink Shrimp and Dungeness Crab. This study examined how the 2026 spring transition along the Newport Hydrographic Line structured the distribution of zooplankton biovolume and larval decapod and fish abundance. Larval samples were collected during five day-night surveys conducted between March and June. An environmental baseline was developed for this season, including sea surface temperature (SST) and chlorophyll. Results show a spring transition around April 5, as seen by cross-shelf SST variability increasing from 11-13°C during cruises 1-3 (March-April) to 11-15°C for cruises 4-5 (May-June) after the onset of the spring transition. CTD density profiles after the onset of the spring transition showed a similar trend, with isopycnals compressing near the surface, indicating strengthening near surface stratification from cruise 1 through 5. Chlorophyll concentrations rose from < 2(mg m^-3 in March to > 6(mg m^-3) by May and June, remaining shoreward of the 200m isobath. Zooplankton biovolume increased in upper water column regions (0-50m) and remained high in nearshore waters throughout the cruises. Higher biovolumes were recorded at night, particularly in the warm surface waters of stations offshore of NH10. These results highlight the physico-biological interactions of upwelling systems that structure the seasonal timing vertical distribution, and nearshore concentration of zooplankton biovolume and larval abundance along the Oregon Coast.
Sydney Smith
Environmental Science major, Oregon State University
CEOAS mentors: Lorenzo Ciannelli and Juan Gutierrez Bravo
Three-dimensional distributions of larval Decapoda across the continental shelf of the Northern California Current during the spring
Decapods are a highly abundant taxonomic group with limited description of their life histories. Several species of larval decapods in the Northern California Current time their spawning with the spring transition and onset of upwelling favorable winds, which bring cold, salty, and nutrient-rich water nearshore. Successful fisheries recruitment is dependent on these oceanographic conditions, determining cohort strength and possible management strategies. Given the knowledge gap of larval decapod distributions and life history in the Northern California Current, we aim to characterize changes of larval Decapoda across the spring transition (~March - June). Two surveys along the Newport Hydrographic line from March were assessed; the decapod samples were counted, identified, and analyzed. A total of 9,168 larvae were identified. Mean decapod larval abundance was 0.94 larvae/m^3, varying from 1.89 (NH3, 0-25 m) to 0.05 (NH35, 0-100m). Most abundant species were Neotrypaea spp., Cancer spp. Zoea, Porcellanidae spp., P. jordani, and Paguridae spp.. Cancer spp. Zoea were found to engage in reverse diel migration during cruise 1, exhibiting a statistically significant difference between night and day weighted depths (p=0.01). No other species had a statistically significant difference in their night and day weighted depths. These results highlight the spatial variability in species distribution, emphasizing the role of coastal upwelling fronts in cross-shelf distribution, and diel vertical migration. These novel findings provide a sketch of the larval dynamics of ecologically and economically important species.
Michael X. Whitefoot
Computer Science major, Central Washington University
CRITFC mentor: Rosie Gradoville
CEOAS mentors: Maria Kavanaugh and Kelly George
Comparing Columbia River Discharge and Surface-Water Conditions at Tongue Point in 2021 and 2026
The Columbia River Estuary is an important transition habitat for juvenile salmon. This study compared Columbia River discharge with daily mean surface-water temperature and salinity at Tongue Point, a Columbia River Inter-Tribal Fish Commission (CRITFC) – Coastal Margin Observation Prediction (CMOP) program monitoring station in the lower estuary, during 2021 and the available 2026 observation period. Juvenile PIT-tag observations at Bonneville Dam provided migration-timing context. Numerical comparisons were limited to the shared January 5–August 1 period. Average discharge was higher and peaked earlier in 2026, while mean temperature and salinity were similar between years. Juvenile observations were concentrated from April through June and peaked in May.