Rivers are key contributors to the oceans’ trace metal budget, supplying micronutrients to phytoplankton and driving coastal geochemistry. Trace metals have natural sources, but can act as conservative pollutants if leached from anthropogenic activities, bioaccumulating up trophic levels and affecting marine ecosystems. In the Gulf of Maine, riverine trace metal inputs are widely understudied. In this study, three rivers that empty into the Gulf of Maine– the Sheepscot, the Kennebec, and the Damariscotta– were analyzed to determine differences in chemical lability and potential anthropogenic input of contamination-prone trace metals. Dissolved, total particulate, and labile particulate concentrations of iron, lead, aluminum, and copper were measured using an ICP-MS with standard digestion methods. Higher concentrations of particulate and dissolved copper were found in the Sheepscot compared to assumed crustal abundance, suggesting different input methods or differences in cycling processes between rivers. Particulate lead was found have a labile fractionation of 49.61% to 74.74% compared to copper and aluminum’s 1-8%. Labile particulate lead concentrations covaried with labile particulate iron along the Sheepscot with a linear relationship (R2=0.993). Overall, the Damariscotta contained higher concentrations of labile lead, iron, and copper than the Sheepscot. These concentrations decreased at a more rapid rate than those of the Sheepscot as salinity increased. All three rivers showed decreasing concentrations of dissolved iron as salinity increased, with the Kennebec and Damariscotta showing evidence of estuarine removal of dissolved iron due to flocculation of iron colloids. This study addresses a key knowledge gap on trace metal composition and potential contamination in rivers of the Gulf of Maine.

RELATED ABSTRACTS

• Past Temperature Reconstructions at Lake Malawi During the Past 75,000 years, Kendall, Magnus, UMass Amherst, Poster Session 4, 2:15 PM - 3:00 PM, 163, C4
• Effects of Soil Physiochemical Properties on Lead and Cadmium Uptake by Ocimum Basilicum, Markelz, Hannah McNulty, UMass Amherst, Poster Session 6, 4:15 PM - 5:00 PM, 165, D15
• Tracing Anthropogenic Nutrient Inputs with Coral-Bound Nitrogen Isotopes Across the Belize Mesoamerican Barrier Reef System, Cruickshank, Emily Marie, UMass Boston, Poster Session 3, 1:15 PM - 2:00 PM, Auditorium, A42
• Polymer-Directed Enzyme Prodrug Therapy in Triple Negative Breast Cancer, Levitan, Ryan Matthew, UMass Amherst, Poster Session 1, 10:30 AM - 11:15 AM, Concourse, B13
• Investigating the Role of lbp-3 in Mediating the Immune Response of C. elegans, Flanagan, John, Bridgewater State University, Poster Session 2, 11:30 AM - 12:15 PM, 163, C28

The Belize Mesoamerican Barrier Reef System (MBRS) is a 1,200-km-long network of coral reefs in the western Caribbean Sea. In recent years, this reef system has been exposed to anthropogenic nutrient runoff from fertilizer use and fossil fuel combustion. Anthropogenic pollution is expected to promote eutrophication, degrading coral reef ecosystems in the MBRS by reducing coral growth. However, the spatial pattern of anthropogenic pollution and its relative importance compared to natural nutrient cycling within coral reef ecosystems has not been established in the MBRS. Here, we reconstruct nutrient inputs to the MBRS using measurements of the nitrogen isotopic composition (δ¹⁵N) of skeletal-bound organic nitrogen in the massive starlet coral Siderastrea siderea, a widespread reef-building coral in the Caribbean. We expect to track anthropogenic nutrient inputs through an elevated δ¹⁵N of food consumed by corals in eutrophied reefs. The δ¹⁵N of S. siderea corals will additionally be compared across nearshore, forereef, and backreef locations as well as latitudinal transects along the length of the Belize MBRS. 

Salt marshes are vertically zonated ecosystems in which tidal elevation dictates sediment and vegetation distribution across the marsh platform. As marshes grow, environmental markers are preserved in the marsh’s sediments and peat, allowing for the reconstruction of paleoelevation and past relative sea-level (RSL) change. While the use of microfossils is the most well-established proxy, this study evaluates the potential use of elemental geochemistry and physical sediment properties to serve as additional proxies for paleo-elevation reconstruction through the establishment of a modern analog. To examine these relationships, surface samples and their elevations were collected at the Cousins River Salt Marsh in Freeport, Maine. Each sample was analyzed for organic content using loss on ignition, bulk density, and X-ray fluorescence to determine its elemental composition. Statistical analysis was performed using Partitioning Around Medoids (PAM) clustering in R-Studio to group samples based on their properties and elevation on the marsh, with an Adjusted Rand Index (ARI) used to evaluate how well these clusters matched known tidal elevation zones. Analyses revealed that bromine and organic content were positively correlated, with higher elevation zones containing increasingly greater concentrations. In contrast, silicon and bulk density were positively correlated with each other, but exhibited increasingly higher concentrations at lower elevations. These correlations indicate that elemental geochemistry and physical sediment properties can reflect tidal inundation gradients across the Cousins River Salt Marsh, establishing a modern relationship that can be used in future studies to infer paleo-elevation and RSL change from marsh sediment cores at this site.

Estuaries and salt marshes provide many benefits to those who rely on them, including wildlife habitat, improved water quality, recreation, and coastal protection. These subtidal ecosystems and their functions are at risk due to accelerated sea level rise, and current projections state that 78% of coastal wetlands globally may become completely submerged by 2100 if they cannot grow vertically with sea level rise. Sediment accumulation is critical for vertical accretion and thus salt marsh resilience. Recent studies highlight the importance of high-energy events for increasing sediment availability and mud organic matter (OM) for its contribution to vertical accretion, but we don’t know the origin of the OM in estuarine sediments in the Northeastern U.S. Carbon and nitrogen stable isotopes in OM can be used to trace the source of sediment, and are particularly useful for differentiating between terrestrial and marine OM. This study applies carbon and nitrogen stable isotopic analysis to eight sediment cores from the lower Connecticut River, CT, lower East River, CT, and Boston Harbor, MA, to determine sediment sources to these estuaries over time. This study will further inform our understanding of the exchange of OM between fluvial and marine sources to estuaries, as well as the delivery of OM from salt marshes to estuaries. We hypothesize that allochthonous marine OM will have the greatest contribution to estuarine sediments throughout time. These processes are key for predicting the resilience of estuaries and salt marshes in the Northeastern U.S. amid accelerating sea level rise.

Microfossils found in sediments from the Ross Sea continental shelf, Antarctica, provide details about Earth’s climate history and can help determine the extent of Antarctic Ice Sheet variability through time. We look at the Pliocene Epoch (5.33-2.56 Ma), a notably warm interval in Antarctica’s past that can serve as an analogue for our near-future climate. The West Antarctic Ice Sheet’s (WAIS) prominent variability due to ocean changes makes this region useful for understanding Earth’s climate evolution. Analyzing Pliocene marine microfossils from the Ross Sea allows us to add to Antarctica’s microfossil profile and interpret Antarctic glacial history. The sediment studied is from International Ocean Discovery Program Expedition 374 Site U1522. Microfossils such as diatoms, radiolarians, and foraminifera are found in various abundance throughout the cores. Sediment samples were processed and scanned at the >63-micron size fraction. Microfossils and materials including coal and glauconite were identified and counted in each sample. Counts inform us of oceanic trends in the Ross Sea through the Pliocene. Preliminary results of this study show that the early Pliocene had abundant radiolarians and few foraminifera which may suggest the dissolution of carbonate. A foraminifera peak, including planktic specimens at ~281 m may correlate with a warm water peak recognized at Site U1523 on the shelf edge at ~3.7 Ma. Additional peaks in components may indicate erosion and winnowing and the occurrence of Ross Sea Unconformity 2 at ~273 m. Further analysis of Site U1522 is necessary to understand the response of the WAIS to ocean changes.

Earth’s climate is rapidly changing. Available instrumental climate records are short – most only go back to around ~1900 AD, although in some places there are older records. To put the natural climate variability into context, we need longer records than the current instrumental record. Understanding the natural range of variability over different timescales is therefore critical to grasping what the future has in store. It is particularly uncertain in tropical Africa where observations are limited.

Past conditions can be determined from organic compounds (biomarkers) preserved in lake sediment, which provide important information on past climates.  This study examines a long sedimentary record collected from Lake Malawi in tropical East Africa in 2005. Core MAL05-2A was collected from the northern basin of the lake and spans the past 75,000 years, which captures a period of stark temperature change. Particularly abundant in this core are branched glycerol dialkyl glycerol tetraether lipids (brGDGTs), which are a group of biomarkers produced by bacteria. The number of methyl groups in different brGDGTs is controlled by temperature and by examining changes in the distributions of brGDGTs, past temperatures can be reconstructed. In addition, the temperature index TEX86, which is based on isoprenoid GDGTs (iGDGTs) produced by archaea, is another technique for reconstructing past temperature.

This study generates a new temperature reconstruction spanning the last 75,000 years by analyzing both brGDGTs and iGDGTs. By looking at past temperatures in East Africa, one can better understand how climate change will impact this region in the future.

RELATED ABSTRACTS

• How Heat Stress Impacts Seed Shape Gene Expression in Oryza sativa, Fawcett, Jayna, UMass Boston, Poster Session 3, 1:15 PM - 2:00 PM, Auditorium, A35
• Using Isotopic Analysis to Assess Estuarine Sediment Dynamics and Composition in the Northeastern United States, Rexroad, Caralyn Grace, UMass Amherst, Poster Session 4, 2:15 PM - 3:00 PM, 163, C2
• Differences in Distributions & Lability of Contamination-Prone Trace Metals in the Kennebec, Sheepscot, & Damariscotta Rivers, Brown, Bella, UMass Boston, Poster Session 3, 1:15 PM - 2:00 PM, Auditorium, A41
• Polymer-Directed Enzyme Prodrug Therapy in Triple Negative Breast Cancer, Levitan, Ryan Matthew, UMass Amherst, Poster Session 1, 10:30 AM - 11:15 AM, Concourse, B13
• Investigating the Role of lbp-3 in Mediating the Immune Response of C. elegans, Flanagan, John, Bridgewater State University, Poster Session 2, 11:30 AM - 12:15 PM, 163, C28

The geology of Western Massachusetts involves a complex sequence of tectonostratigraphic units associated with Ordovician island-arc/microcontinent accretions along the Laurentian margin. In the town of Chester, Massachusetts, layers of garnet-rich pelitic schist near the Rowe-Moretown boundary provide an opportunity to examine the mechanisms, conditions, and timing of the events related to the assembly, and later deformation, of the Northern Appalachian Orogen. In this study, we perform analysis of polished thin sections taken from three sample locations containing abundant garnet. We performed structural analysis of outcrops in the field, followed by hand-sample description. Billets were cut parallel to both strike and lineation directions, from which the best samples were chosen for thin section preparation. Remnants of an earlier foliation perpendicular to the current foliation, as well as layered and sigmoidal oxide and quartz inclusion trails in garnet were identified using a petrographic microscope. Compositional maps at multiple scales were made on the electron microprobe to locate datable phases and to identify locations for quantitative traverses. Xenotime is present, but no monazite was found in these samples. Ongoing work includes geothermobarometry and forward modeling to constrain the changing metamorphic conditions in the area. Then, xenotime U-Pb geochronology will be used to place temporal constraints on the metamorphism of these rock units. We aim to provide clarification of the tectonic history and deformation involved in the emplacement of the Rowe-Moretown units. This will contribute to a broader understanding of the Taconic orogeny in Western Massachusetts and Appalachian orogenesis of New England.

RELATED ABSTRACTS

• Analysis of Surface Sediment Geochemistry and Properties to Infer Elevation Zones in the Cousins River Salt Marsh, Maine, Roche, Jerard William, UMass Amherst, Poster Session 4, 2:15 PM - 3:00 PM, 163, C1
• Homolingual Language Ideology: Implications for Classroom Second Language Education, Stilphen-Wildes, Timothy A., UMass Amherst, Poster Session 6, 4:15 PM - 5:00 PM, Auditorium, A30

RELATED ABSTRACTS

• Foliar Microplastics Deposition: An Urban-Rural Comparison, Carlson, Lotus, UMass Amherst, Poster Session 6, 4:15 PM - 5:00 PM, Auditorium, A58
• Snowpack Accumulation and Melt Dynamics in Southcentral Alaska, and Their Influence on Streamflow, Olland, Gabriel Béla, UMass Amherst, Poster Session 6, 4:15 PM - 5:00 PM, Auditorium, A71

As a high-latitude state, Alaska’s streamflow and watershed dynamics are strongly influenced by snowpack accumulation and melt. Understanding these regimes and the factors impacting them, as well as their associated impact on streamflow**,** is crucial to water resource management and hazard mitigation. Streamflow generation mechanisms in this region remain poorly understood and constrained. While both streamflow data and snowpack data are publicly available and widely used, they are frequently analyzed independently of one another rather than as two related variables. We retrieve SNOTEL data from the Natural Resources Conservation Service and streamflow data from USGS stream gauges for the analysis. Using these data, we aim to describe the primary mechanisms that drive snowpack accumulation and melt in the region and to understand how snow dynamics have been evolving in response to climate change. Datasets are compiled to show and compare statistics such as peak SWE, peak SWE DOY, melt onset, melt duration, and total melt-season discharge at daily and interannual scales. Across the region, snow timing statistics appear to be trending downward. Although there are few SNOTEL sites within USGS streamflow gauge watersheds, snowpack appears to contribute similarly to streamflow across watersheds. High-snow years increase streamflow by approximately 0.5–0.6 standard deviations relative to low-snow years, which has important implications for water availability, energy generation, and fish habitat and migration. Better understanding the hydrologic response of the region to climate change will contribute to more precise modeling and better informed research and management.

Snowmelt-dominated headwater streams play an important role in the global carbon cycle. Snowmelt provides large subsurface flushing events, mobilizing CO₂ that eventually degasses in streams. However, the amount of CO₂ entering headwater streams is difficult to predict and may depend on watershed carbon source limitations versus water transport controls. To understand the role of precipitation and water transport in watershed-scale stream CO₂ emissions, we investigated hydrometeorological and geochemical datasets in the East River Basin (ERB) in the Rocky Mountains of Colorado over interannual scales. We used SNOTEL and PRISM precipitation to differentiate precipitation on snow versus bare ground. Additionally, the Lawrence Berkeley National Laboratory (LBNL) open-source dataset was used to compile stream discharge and geochemical data across 11 sites in the ERB during water years 2014 - 2021. Cumulative water year precipitation during snow‑cover periods produced a stronger relationship with discharge at 10 of the 11 sites. We modeled in-stream CO₂ concentrations (pCO₂) from available geochemical data and air-water gas exchange velocity for CO₂ (k_CO2) to calculate CO₂ fluxes (F_CO2) from these sites. Overall, the relationship between pCO₂, k_CO2, and F_CO2 was compared with the precipitation and discharge data to investigate relationships across spatiotemporal scales. Our results demonstrate how robust geochemical datasets can be used to help relate snowmelt to stream CO₂ degassing, which must be better characterized as climate and hydrology in watersheds change.

Streams are a consistent source of carbon dioxide to the atmosphere, with some estimates placing emissions at over 5.5 petagrams per year. Yet, there is significant uncertainty in quantitative estimates of contributions to stream carbon from sources such as groundwater. This study aims to assess groundwater contributions to stream carbon from a localized perspective by examining carbon dioxide fluxes from headwater streams at Harvard Forest in Petersham, Massachusetts. I hypothesize that CO2 values from groundwater will be much higher than those at the surface; with this in mind, I also expect groundwater carbon contributions to correlate with stream emissions.

To quantify carbon emissions, we measured CO2 and critical chemical variables, including cation and anion concentrations, pH, temperature, and dissolved oxygen throughout Fall 2025. We tracked these variables along a stream reach and groundwater wells adjacent to the stream sites to develop a spatial map of CO2 flux across sites upstream and downstream of the Harvard Forest waters. Additionally, we calculated carbon fluxes using a model that incorporates pCO2 values alongside gas transfer velocities (kCO2). Finally, we created a Piper diagram of the ionic composition of the streams, which we use to estimate quantitative groundwater input rates. 

A spatial representation of carbon flux is critical for understanding the physical and chemical processes that shape local gas transfer and the impact of groundwater discharge on the carbon budget. These results provide insights into the mechanisms governing stream carbon fluxes at the local scale and contribute to a better understanding of watershed-level carbon budgets.