Rivers transport large amounts of organic carbon, trace metals, and nutrients from land to coastal oceans. At the land-sea interface, elemental fluxes and transformations are influenced by processes occurring in rivers, wetlands, and estuaries. Increasing anthropogenic pressure, such as land-use change and increasing frequency of extreme events (e.g., hurricanes, fires), are altering the sources and quality of organic carbon and nutrients exported to coastal ecosystems. Maintaining the integrity of coastal aquatic systems is critical because they provide essential ecosystem services. Effectively adapting to meet these challenges requires us to understand the biogeochemical linkages of carbon and nutrient cycles to ecosystem processes and microbial activity, and how they are altered by human activities. This session aims to bring together scientists from all fields of biogeochemistry, covering ecosystems at different latitudes and spatio-temporal scales. We welcome contributions that address carbon and nutrient fluxes across the land-ocean continuum, biogeochemical transformations in rivers, coastal wetlands and estuaries, as well as the fate of terrestrial carbon in marine environments. We also encourage submissions that explain mechanisms underlying observed patterns in the distribution or transformation of sedimentary, particulate, and dissolved organic matter, their relationship to CO2 outgassing or uptake, and microbial community composition across aquatic gradients. In addition, we are interested in approaches to quantify the response of coastal aquatic systems to environmental stressors to guide conservation and restoration efforts.
Lead Organizer: Michael Seidel, University of Oldenburg (m.seidel@uni-oldenburg.de)
Co-organizers:
Sairah Malkin, University of Maryland (smalkin@umces.edu)
Patricia M. Medeiros, University of Georgia (medeiros@uga.edu)
Sasha Wagner, Rensselaer Polytechnic Institute (wagnes3@rpi.edu)
Nicholas D. Ward, Pacific Northwest National Laboratory (nicholas.ward@pnnl.gov)
Presentations
06:00 PM
Implementing high-frequency nitrate quantification in water quality monitoring in the Chandeleur Sound of Pontchartrain Basin, Louisiana, USA (9235)
Primary Presenter: Emily Piwowarski, University of Louisiana at Lafayette (emily.piwowarski@louisiana.edu)
The Louisiana coast is a model for regional climate change effects, due to frequent severe weather, increasing freshwater inundation, and elevated sea surface temperatures. Other anthropogenic pressures in southeastern coastal Louisiana are constituted by proximity to the New Orleans metropolitan area, Lake Pontchartrain and Mississippi River outflow, and heavy uses for Gulf industries. The TriOS OPUS, an in situ optical nitrate (N-NO3) sensor, was deployed in July 2024 to Chandeleur Sound, a shallow estuary in Pontchartrain Basin, Louisiana near the Biloxi Wildlife Management Area. The deployment site represents a relevant study area for monitoring nutrient dynamics in an estuarine ecosystem under a changing climate and anthropogenic forcings. The TriOS OPUS has been deployed with a YSI Exo3 sonde from July 2024 to present. The OPUS measures concentrations of nitrate, total suspended solids, and a nonspecific indicator for dissolved organic matter, SAC254, every 15 minutes. The Exo3 sonde measures chlorophyll-a, dissolved oxygen, temperature, salinity, and turbidity. Discrete reference nutrient samples are collected monthly. This presentation will highlight the effects of ephemeral storm events captured by high-frequency nitrate quantification which are missed by traditional, discrete sampling. Storm-driven disturbances will be compared with pre-storm conditions to characterize short-term water quality response. Nitrate stimulation events will be discussed in context of event drivers, biological response (via chlorophyll-a), and trends in other water quality parameters.
06:00 PM
MONITORING WATER QUALITY AND PHARMACEUTICALS AND PERSONAL CARE PRODUCTS (PPCPS) IN THE QUINNIPIAC RIVER, CONNECTICUT, USA (9750)
Primary Presenter: Joanna Kinsey, Quinnipiac University (joanna.kinsey@quinnipiac.edu)
The Quinnipiac River in Connecticut, USA traverses through urban, forested, and estuarine areas before emptying into Long Island Sound. In addition to the variety of surrounding land-uses, the river also receives wastewater effluent from multiple water treatment plants, which introduce pharmaceuticals and personal care products (PPCPs). To evaluate the contribution of land-use and effluent input on the river, water samples were collected at seven locations including above and below three water treatment plants between Meriden, CT and New Haven, CT. Summer and winter seasonality was compared by sampling five times in June-August and three times in November-January, in both 2023-2024 and 2024-2025. At each location, in situ pH, conductivity, and temperature were measured, along with absorbance and fluorescence of dissolved organic matter (DOM), dissolved organic carbon (DOC), nitrate and nitrite concentrations, and fecal coliform bacteria counts. The presence of PPCPs was determined by passing 300-600 mL of water through solid phase extraction (SPE) cartridges and analyzing the eluent by gas chromatograph-mass spectrometer (GC-MS). The results showed measurable amounts of several prescription medications, as well as fertilizers, hydrocarbons, and precursors to plastics. Winter 2023-2024 showed elevated DOC concentrations and coliform counts, but slightly lower DOM fluorescence compared to summer 2023-2024 samples.
06:00 PM
Nutrient Dynamics in the Lower Cape Fear River and Estuary: Assessing the Impact of Agricultural Inputs and Storm Events on Water Quality (8757)
Primary Presenter: Emily McGee, University of North Carolina Wilmington (eam1536@uncw.edu)
The Lower Cape Fear River and Estuary is located in coastal North Carolina. This area is influenced by both natural processes and human activities, making it an important site for studying nutrient patterns and water quality. This study examines inorganic and organic nutrient concentrations in the Lower Cape Fear River and Estuary in coastal North Carolina. Water samples were collected monthly from eight main sites, with additional seasonal sampling at other locations to capture nutrient variations. Samples were collected from upstream freshwater areas to downstream coastal waters, between October 2020 and September 2024. Additional samples were taken after major storm events to assess how storms influence nutrient input and transport. The primary objective is to identify sources of nutrients to the study area and their potential impacts on water quality as they move from upstream of the river out into the Atlantic Ocean. We measured dissolved inorganic and organic nitrogen (DIN, DON) and phosphorus (DIP, DOP). Preliminary data indicates that upstream sites, particularly those near agricultural areas exhibit elevated concentrations of nutrients, while sites downstream showed lower levels of nutrients. The results are likely due to the influence of the coastal ocean as it mixes with the nutrient-rich water coming downstream to form brackish water in the estuary. This study helps us understand how nutrients behave in our river and estuary system while providing insight into the broader impact on our coastal waters.
06:00 PM
LONG- AND SHORT-TERM PATTERNS IN MICROBIAL EXTRACELLULAR ENZYME ACTIVITY ALONG THE MISSISSIPPI GULF COAST (8835)
Primary Presenter: Jacqueline Pavlovsky, University of Mississippi (jpavlovs@go.olemiss.edu)
Marine microorganisms play critical roles in biogeochemical cycling, largely through the activity of extracellular enzymes. While the involvement of these enzymes in organic matter degradation is well-known, how microbial enzyme activity fluctuates over different timescales is uncertain. Using artificial substrates, day-to-day, week-to-week, and month-to-month variation in the activity of phosphatase and beta-glucosidase was examined in seawater at five shoreline sites along the Mississippi Gulf Coast, and related to variability in water temperature, pH, dissolved oxygen, and salinity. Enzyme activity varied over each timescale, with phosphatase showing greater variability at scales of day-to-day and week-to-week, while beta-glucosidase showed greater variability from month-to-month. Phosphatase varied across sites over the week-to-week and month-to-month timescales, while beta-glucosidase varied by site during the day-to-day, week-to-week, and month-to-month timescales. Phosphatase activity over day-to-day and week-to-week timescales was correlated with patterns in salinity and conductivity, whereas beta-glucosidase activity was correlated with pH over day-to-day scales and with conductivity, salinity, and pH over week-to-week. Neither enzyme was correlated with environmental factors over month-to-month timescales. These findings show how short- and long-term variability can influence enzymatic activity of the nearshore marine microbial community that could lead to impacts on biogeochemical cycling in coastal waters of the Gulf of Mexico.
06:00 PM
THREE YEARS OF HIGH-RESOLUTION OBSERVATIONS FROM AN ARCTIC ESTUARY NEAR KOTZEBUE, ALASKA (9474)
Primary Presenter: Eilidh MacLeod, Columbia University Lamont Doherty Earth Observatory (ejm2242@columbia.edu)
The Arctic is warming faster than the rest of the planet, resulting in dramatic changes to freshwater flows, sea ice extent and duration, and nutrient availability to support primary production. These changes are, in turn, altering the food web, which threatens subsistence food systems and cultural integrity in Indigenous Arctic communities, largely though emergent threats such as Harmful Algal Blooms (HABs). Kotzebue, Alaska (Qikiqtaġruk) is one such community that relies on marine food sources, so understanding these changes there is critical. As part of a community-led sampling project, we deployed a moored YSI EXO-2 sonde at the entrance to Kobuk Lake in the summers of 2022, 2023, and 2024. The sonde measured temperature, salinity, oxygen, turbidity, dissolved organic matter, chlorophyll and phycocyanin fluorescence every 10 minutes. Across the three seasons, we documented several distinct salinity spikes, up to 27 ppt, in the surface waters of Kobuk Lake. Analysis of temperature, dissolved organic matter, and other water characteristics showed that the spikes were consistent with water originating in the Chukchi Sea. Analysis of wind speed and direction obtained from the nearby PAOT weather station showed no direct correlation between wind speed or direction and salinity, though high-speed winds (>10 knots) were found to precede all spikes. A Sentinel-3 satellite time series for the same location is being developed to compare with the in-situ mooring data. We will present our analysis of the mooring data and the larger scale changes observed in the satellite data.
06:00 PM
Spatial and Temporal Progression of Phytoplankton-derived Organic Carbon in the Amundsen Sea Polynya, West Antarctica (9009)
Primary Presenter: Giovanna Utsumi, University of Georgia (giovanna.azariasutsumi@uga.edu)
The Amundsen Sea Polynya (ASP) is one of the largest and most productive polynyas in coastal Antarctica, acting as a sink of atmospheric CO2. Changes in water circulation are causing rapid thinning of ice shelves and basal melting, which could potentially influence primary production and the carbon cycle in this region. Here, we investigated particulate (POC) and dissolved organic carbon (DOC) distribution using bulk concentrations and δ13C-POC to better understand organic carbon (OC) dynamics in the ASP ecosystem. Depth-profile samples (2 m – 732 m) were collected across the polynya (from near to off shelf), and repeatedly at same station after 20 and 30 days during the austral summer of 2022. Our initial results showed that POC and DOC concentrations were generally higher at surface and subsurface waters (235 μg L-1 and 64.2 μM, respectively) compared to deeper depths (32.5 μg L-1 and 44.1 μM, respectively). Surface δ13C-POC values measured in the polynya (-28.1‰) were more enriched than at deeper depths (-29.3‰), but more depleted than at oceanic stations (-27.8‰), likely due to algal blooms. Over time, depth-profile samples revealed a slight increase in OC concentrations (POC: 20.2 to 44.8 μg L-1 and DOC: 42.0 to 46.0 μM) and an enriched δ13C-POC signature (from -26.6 to -23.8‰), suggesting changes in OC cycling, presumably due to bacterial responses associated with bloom progression and sediment resuspension. Our findings provide new insights into OC dynamics in the ASP, helping us better understand the contributions of coastal polynyas to the global carbon cycle.
06:00 PM
Coastal plankton response to fire-ash leachate shaped by pre-existing in situ conditions (8774)
Primary Presenter: Nicholas Baetge, Oregon State University (nicholasbaetge@gmail.com)
Climate-driven warming is projected to increase the magnitude and severity of wildfires, as well as the frequency of severe wildfires, in many regions around the world. Wildfire ash deposition can be a source of essential new nutrients for phytoplankton in the ocean, but ash can have variable nutrient content and can carry heavy metal and organic matter toxins that inhibit microbial growth. Here we quantitatively describe short-term physiological and ecological responses of coastal surface ocean microbial groups to the compounds leached from fire-ash, collected from the 2017 Thomas Fire in California and produced in the lab from coastal Oregon foliage. We find that the microbial impacts of fire-ash leachate may depend less on its composition and more on the pre-existing in situ conditions and microbial community. Dissolved organic matter (DOM) from fire-ash leachate could stimulate bacterial production, but its bioavailability to bacteria was observed to decrease in high biomass conditions. Additionally, zooplankton grazing rates decreased more than phytoplankton division rates in response to fire-ash leachate, both in low and high biomass conditions. This led to increased phytoplankton accumulation rates, which could set the stage for large-scale blooms.
SS14P - Biogeochemical Connections and Ecosystem Adaptation Across the Land-Ocean Continuum
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A