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As climate change and carbon dioxide (CO2) emissions continue to alter oceans, it is critical to understand how marine life will respond. Atmospheric CO2 dissolves into ocean water, beginning a series of chemical reactions that lower pH and deplete free carbonate ions—this phenomenon is called ocean acidification (OA). Marine phytoplankton impact ocean chemistry by performing photosynthesis and cycling carbon. They also form the base of marine food webs and are thus implicated in fishery productivity and human food security. As part of the National Oceanic and Atmospheric Administration's Ocean Acidification Program, this research aimed to document the progression of OA and its effects on marine life. The project combined data analysis, remote sensing, and laboratory experiments to understand phytoplankton community change. Data from scientific cruises in 2018 and 2022 were compared to investigate inter-annual variability in phytoplankton distribution, size, and efficiency. These cruises measured chemical and biological indicators, including pH, temperature, and pigments associated with particular plankton taxa. Water samples collected at various depths were imaged to gather phytoplankton cell counts. The findings demonstrate a clear pH gradient along the East Coast, with northern waters being significantly more acidic than southern waters. This difference is primarily driven by increased precipitation, land characteristics, and ocean current dynamics. Biological community structure and the photosynthetic efficiency of the phytoplankton sampled along the coast varied with latitude and time, demonstrating that continued climate change and intensifying acidification will affect phytoplankton distribution and consumption of CO2, with reverberations throughout the ocean and climate systems at large. 

Volcanic eruptions deposit Fe-bearing volcanic ash in the ocean, thereby increasing biological productivity. The increased organic matter in areas of high biological productivity uses up oxygen as this organic matter decays and sinks through the water column. Past living beings, like foraminifera, ate organic matter that was carbon-rich and sometimes had metals absorbed into their carbon, creating coatings inside and outside their shells. These coatings can tell us about how biological productivity was affected before, during, and after the volcanic eruption. The studied cores are from the northwest Pacific Ocean and are close to geologically young volcanoes that are not well understood. The two cores that we focused on were VM28-309 and VM36-15 both taken by the Vema research ship. We studied the relationship between ash deposition and biological productivity by looking at all the ash layers in both cores. We found that in most of the ash layers, there were black or dark-colored foraminifera with coatings inside and outside the shells that were often carbon-rich and sometimes metal-rich. We attribute this coating to the increase of organic matter in surface waters when there was deposition of large amounts of volcanic ash. We also found high concentrations of Barium metal in VM28-309. Barium (Ba) is a biological marker because most or all Ba originates from the organic matter contained in sediments. We found that ash layers containing the finest materials (<38 micrometers in size) had the highest Ba content. For accurate results, we must sample above and below ash layers and select more sediment cores in the area. Also, Barium corrections must be done using data on biogenic silica contents. Loss on ignition (LOI) data will give us an estimate of the total organic carbon in each sample- allowing a second direct assessment of the increase in biological productivity produced by the deposition of volcanic ash. 

Known as a bio-limiting metal, high abundances of iron in sea water can amplify biological productivity. The growth of diatoms and other photosynthetic organisms increases, providing more food for grazing organisms like foraminifera. The net result is more organic matter in surface waters and ultimately in surface sediments. Existing satellite data show increases in ocean chlorophyll in areas affected by volcanic eruptions. We infer from this that iron derived from volcanic ash does increase biological productivity. However, the relative increase in productivity is unknown. We examined 3 sediment cores from the Equatorial Western Pacific to analyze the relationship between volcanic ash and biological productivity: RC14-44, RC14-66, and RC14-67. All contain black or dark-colored foraminifera within ash layers and white-shelled foraminifera outside ash layers. We attribute the dark material outside and inside the foraminifera to organic carbon and metals. In our cores, some foraminifera are covered in iron sulfide (FeS), which could be pyrite, and contain large amounts of carbon as well as high abundances of aluminum and silicon. We examined barium concentrations to gain further knowledge of biological productivity at specific core depths as barium is a marker for primary productivity. We found that barium levels within ash layers increased at least ten-fold. Within ash layers, we also noticed that the ashes with higher amounts of fine silt and clay sized material have the greatest increase in barium content, perhaps related to explosion size. This pattern of increases in Ba, metals and organic carbon within ash layers compared to surrounding sediments shows that volcanic ash deposition increases marine productivity. For future research, measuring markers for biological productivity like biogenic silica content and loss on ignition (LOI) within and outside ash layers would further clarify the relationship between volcanic ash deposition and biological productivity. 

Rapid environmental changes are predicted to impact shellfish abundance and their commercial value. The Eastern Oyster, Crassostrea virginica, a key foundation species with high environmental and commercial value has dramatically declined due to climate and anthropogenic impacts over the last century. Our current understanding of oyster vulnerability mostly stems from laboratory-based experiments but lacks studies in natural systems. Here, we investigated how shell production and composition of C. virginica are affected by natural salinity gradients under different temperature regimes. We studied variations in oyster shell shape, production, structure, composition, and organic matrix content in oysters from a temperate, Hudson River (NY), and subtropical, Galveston Bay (TX), estuary. parameters such as weight, area, density, chalk production, and organic matrix to see how the shells varied based on salinity and temperature. Our findings showed that Eastern oysters produced shells with higher chalk content under calcification-limiting environments (i.e., low temperature and low salinity). In comparison, shells with lower chalk content were produced in high predation environments (i.e., high temperatures and salinity). Temperate oyster's shell structure preferentially favored chemical protection against dissolution while subtropical oysters preferentially favored mechanical protection against predation. Oyster’s shell showed a strong capacity for protective responses under calcification- and predation-controlled environments. 

Earth’s oceans serve as a large atmospheric reservoir where carbon dioxide is absorbed and stored. In modern years, fossil fuel emissions have caused a large influx of CO₂ into the atmosphere and thus it is being absorbed into the oceans causing ocean acidification. This phenomenon has vast negative impacts, especially on the most abundant organism in the ocean– phytoplankton. Using data from a cruise in 2018, a prominent pH gradient has been mapped along the East Coast of the U.S, with Northeastern waters being more acidic. It is the purpose of this research to investigate how certain phytoplankton species are responding to this pH gradient and changes in their nutrient supplies. Four different species of phytoplankton were chosen from the Long Island Sound, and are currently being tested in varying concentrations of CO₂ (280 ppm, 400 ppm, and 800 ppm) – to mimic the pre industrial, modern, and future CO₂ levels of the Atlantic ocean. With the preliminary results of this experiment, it’s evident that the Diatom taxa is performing best overall, and specifically well in the 280 ppm, because of their unique carbon concentrating mechanisms that allow them to outcompete other phytoplankton in low pCO₂ waters. Future research will include monitoring this ongoing CO₂ experiment as well as testing other species of phytoplankton. It’s imperative to understand how these phytoplankton will react to changes in their environments as harmful algal blooms are becoming more common with climate change. 

The El Niño Southern Oscillation (ENSO) is a climate variation that occurs in the Eastern Equatorial Pacific (EEP) ocean, which influences the position of the thermocline today. The ENSO cycle is split into three states: a normal state, an El Niño state, and a La Niña state. Each one is marked by different sea surface temperatures (SST). Under normal conditions, the trade winds push warm water westward, away from the coast of South America. This allows cool water to upwell the east and creates a zonal SST gradient. Every few years, the trade winds slow, preventing the flow of warm water. This increases the SST in the EEP and produces an El Niño. The winds can also strengthen and move more warm water westward. The heightened zonal SST gradient forms a La Niña. This project investigates past conditions in the EEP by reconstructing the mean position of the thermocline: a layer in the ocean where temperature rapidly changes with depth. In the modern ocean, the thermocline is shallower in the east, where SSTs are cool, and deeper in the west, where SSTs are warm. The more uniform SST gradient during an El Niño event flattens the zonal slope thermocline; the stronger gradient during a La Niña steepens it. The temperature proxy used to determine past thermocline positions is the isotopic composition of oxygen in foraminifera (δ18O). Foraminiferal δ18O increases with depth in the water column, as temperature decreases and density increases. Two species with contrasting depth-habitats were analyzed; Globigerinoides ruber, which lives near the surface above the thermocline, and Neogloboquadrina dutertrei, which lives in the lower thermocline. When the thermocline shifts, it changes their difference in δ18O. A smaller difference indicates a deeper thermocline and an El Niño-like state; a greater difference indicates a shallower thermocline and a La Niña-like state. The forams were collected from two deep-sea sediment cores. The first was Ocean Drilling Program (ODP) Leg 202 Site 1239 (0.67˚S, 82.08˚W, 1414 m) drilled in the east near the coast of Ecuador. The second was ODP Leg 138 Site 849 (0.10˚S, 110.31˚W, 3858 m) toward the west. Rather than identifying specific ENSO events, this method provides insight into the position of the thermocline and therefore the mean state of the EEP during the Holocene and last glacial period. 

The Navajo Nation is the largest Native American reservation in the United States and is located on the Colorado Plateau. Uranium (U) and Arsenic (As) are two predominantly geogenic contaminants found on the Colorado Plateau. These contaminants leech into groundwater aquifers through anthropogenic activities, but little information is known about the natural distribution of these contaminants. Heavy uranium and coal mining have caused elevated levels of U and As to infiltrate groundwater, however there is little research on the natural distribution of these elements in the regional bedrock and the extent to which they exist as exposure pathways in water, air, and soil. We used a robotic X-ray Fluorescence (XRF) machine, Minalyzer CS, to scan over 850 meters of cores that were collected in Petrified Forest National Park (PFNP) and generated a whole-rock geochemical profile with respect to depth and show the areas in the cores that have elevated levels of Uranium and Arsenic. We also sampled for Inductively Coupled Plasma Mass Spectrometry (ICPMS) to calibrate the concentrations of elements from our XRF scans. In conjunction with X-ray Diffraction (XRD) analysis to quantify mineralogy and Computed Tomography (CT) to quantify porosity/permeability, we are in the process of developing models for the integrated geologic history of the region and the processes responsible for the concentration and mobilization of these elements in bedrock. An understanding of these processes is essential for differentiating the exposure risk between geogenic and anthropogenic sources of U and As. 

Antarctic sea ice modeling has become essential due to the exacerbating effects of climate change on the region, with the aim of utilizing present and past data to predict the future. However, a setback lies in the grand scale of the data needed to make these predictions best, spanning both spatial and temporal axes. As a result, dimension reduction is necessary to capture the most important patterns of variability – a pre-processing step for future predictions. The utilization of Machine Learning tools, such as autoencoders, has been investigated as an alternative to linear dimension reduction methods, such as EOFs. Input data includes satellite observed gridded data in the Antarctic region from 1979 to 2022. Different versions of the autoencoder model are investigated, with varying components in its architecture, including activation function (linear and ReLU), bottleneck units (compressed dimensions), and added layers. It is found that the seven-layered and five-layered ReLU models outperform other configurations across all bottleneck units, including when compared with EOFs. These models also contain a higher explained variance ratio: at 11 compressed dimensions, the seven-layered autoencoder can capture 18.7% more variance than the 11 EOF modes explain. The ReLU activation function also allows the model to detect nonlinear patterns, providing an additional benefit to the improved RMSE and variance ratio. The findings demonstrate that the autoencoder model serves as a worthy alternative to EOFs, likely extracting more predictable variance in the sea ice field. The result is crucial for understanding sea ice spatiotemporal variability and its predictability in the Antarctic. 

Geological evidence of the terrane boundary between the Nagssugtoquidian orogeny and the North Atlantic Craton is present in exposed rocks on both the east and west coasts of Greenland. The subglacial continuation of this boundary must be inferred from geophysical data across the Greenland ice sheet. Several possible locations have been suggested, based on combinations of regional grids of gravity and magnetic anomalies. We use high-resolution, flight-line profiles of gravity and magnetics data from Operation Ice Bridge (OIB) to investigate both the location and the nature of the boundary. Using Geosoft we modeled the density and susceptibility contrasts associated with previously proposed locations of the terrane boundary (Dawes, 2009 and Henricksen et al., 2009), and found evidence for several additional boundaries with significant contrasts in geophysical properties. We present a series of 2D profile models and map the most significant boundaries to reveal a more complex image of the subglacial geology beneath the Greenland ice sheet. 

The northern E-W boundary of the Caribbean Plate is primarily left lateral and has evolved through the Cenozoic from transtensive to transpressive. The southern branch of this boundary, the Enriquillo-Plantain Garden Fault (EPGF), traverses southern Haiti through the Jamaica Passage to Jamaica. Damaging earthquakes occurred in Haiti in 1751, 1770, 2010 and 2021, and in Jamaica in 1692 and 1907, yet the Jamaica Passage segment has little known seismicity with no large historic events. The EPGF in the Passage follows a 2-3 km deep trough that is less oblique to the plate motion, and was imaged previously by the 2012 HAITI-SIS seismic cruise. We present the results of an NSF-funded RAPID cruise carried out in January 2022 to the Jamaica Passage, that investigated the EPGF with a hi-res multichannel seismic system collecting >650 km of data and 47 sediment cores. We observe prominent scarps along the EPGF consistent with large seismogenic displacements, and discovered widely distributed event deposits in the cores (McHugh et al. abstract). Imaged Neogene shortening structures verge southward, and are consistent with reactivation under compression. Shortening decreases from east to west. The Matley (eastern) and Navassa (central) sub-basins feature imbricate thrusting along their northern flanks, and the Morant (western) sub-basin features open folding flanked by unfolded sediments in its central part. At the depths imaged by our data, the strain is mostly partitioned: The EPGF is sub-vertical with no consistent vertical offsets, thus accounting for only sinistral motion sub-parallel to the fault, while shortening is directed across the basins. Structures point to two distinct stress components: a regional one that drives transpression, and a spatially variable one close to the EPGF, possibly in response to minor bends along this fault. Extensional and contractional structures are superimposed at distinct times on the north flank of the EPGF, as expected of a fault that translates relative to the causative fault bends. This is an important feature related to the major fault bend west of the Morant Basin, marking the transition between the Passage and the Jamaica segment of the EPGF. The results will help us better understand the tectonics of the region and its earthquake history, and to assess the hazard for future events.