Coastal and shelf ecosystems are the most productive regions of the world’s oceans. Broad, shallow shelf ecosystems like those in the west Atlantic basin also interact with ocean boundary currents, creating conditions that play important roles in biogeochemical cycles. Here we seek to “take the pulse” of shelf systems in the context of shifting boundary currents with predicted environmental change, which requires a baseline understanding of current status and concerted efforts across multiple disciplines. This session welcomes research on coast-to-boundary current processes encompassing physical, chemical, biological, and biogeochemical studies of cross-shelf systems, particularly in areas that intersect western boundary currents (e.g., Gulf Stream, Kuroshio, East Australia, Brazil). We seek to showcase research from process studies, time-series, computational modeling, or other ecosystem assessments that address questions aimed at understanding the function within any region across this coast to boundary current continuum at all levels of ecological organization, from genes to ecosystems. Interdisciplinary studies that integrate multiple ecosystem processes are particularly encouraged. Our goal for this session is to bring together the community of scientists across the globe focused on these comprehensive regional studies to combine efforts and enhance collaborative and comparative opportunities across our datasets.
Lead Organizer: Christian Briseño-Avena, University of North Carolina Wilmington (brisenoavenac@uncw.edu)
Co-organizers:
Matthew McLean, University of North Carolina Wilmington (mcleanm@uncw.edu)
Winifred Johnson, University of North Carolina Wilmington (johnsonwm@uncw.edu)
Bradley Tolar, University of North Carolina Wilmington (tolarb@uncw.edu)
Presentations
06:00 PM
INVESTIGATING THE EFFECT OF CHANGING SEASON AND SALINITY ON THE ABUNDANCE AND DISTRIBUTION OF AMMONIA- OXIDIZING ARCHAEA AROUND TOPSAIL ISLAND, NC (9310)
Primary Presenter: Madisyn Morrison, University of North Carolina Wilmington (mazzycmorrison@gmail.com)
Ammonia-oxidizing Archaea (AOA) are some of the most prevalent organisms on our planet. As their name suggests, AOA convert ammonia to nitrite completing the first step in nitrification and contributing to the marine nitrogen cycle. Despite their global distribution, AOA have not often been found at high abundance in shallow, coastal ecosystems, including along the US Atlantic coast. However, previous research showed that AOA abundance increases dramatically each summer within coastal Georgia waters, and AOA diversity also appears to increase with low-moderate salinity shifts. To investigate these dynamics, we have collected samples since September 2023 around Topsail Island, NC, capturing a salinity gradient from the Atlantic Ocean to the Intercoastal Waterway. As other work in our lab suggests summer AOA ‘blooms’ appear throughout the NC coast, we hypothesized similar trends for Topsail Island. Here, we determined AOA abundance via quantitative PCR (qPCR) alongside nutrient concentrations (ammonia, nitrite, nitrate), and will characterize AOA diversity across the salinity gradient using functional gene sequencing. At Topsail Island, we found a slight increase in AOA abundance in summer, though this varies by sample site. However, there is a significant correlation between AOA 16S rRNA gene abundance and salinity, indicating that tidal stage and season play an important role. Given the predicted changes along the NC coast (including sea level rise and Gulf Stream shifts) it is critical to establish seasonal monitoring for key biogeochemical processes.
06:00 PM
INFLUENCE OF DISTINCT WATER MASSES ON ORGANIC CARBON CONSUMPTION ACROSS THE SOUTHERN EAST CHINA SEA SHELF ECOSYSTEM (8736)
Primary Presenter: Chung-Chi Chen, National Taiwan Normal University (ccchen@ntnu.edu.tw)
The southern East China Sea (ECS) is characterized by four distinct water masses: coastal water, Taiwan warm current water, upwelling water, and Kuroshio water. These water masses vary in their biogeochemical properties, significantly influencing the region's nutrient dynamics and planktonic processes. Nitrate concentrations were found to be highest in coastal water, followed by upwelled water, Taiwan warm current water, and lowest in Kuroshio water. Distribution patterns of chlorophyll a (Chl a) and particulate organic carbon (POC) closely reflected this nitrate gradient, with the highest levels in coastal water and the lowest in Kuroshio water. Plankton community respiration (CR), which reflects organic carbon consumption, exhibited similar patterns, showing the highest rates in coastal water, intermediate levels in upwelled and Taiwan warm current waters, and the lowest rates in Kuroshio water. A multiple linear regression analysis between plankton CR, POC, and bacterial production was conducted to further investigate the relationships driving carbon cycling in these water masses. The results suggest that coastal and upwelling regions of the southern ECS play a critical role in organic carbon consumption, likely driven by nutrient availability, with implications for carbon flux and ecosystem function across this dynamic shelf region.
06:00 PM
Atmospheric Drivers of Subseasonal Variability in North Atlantic Phytoplankton Phenologies (9205)
Primary Presenter: Shaun Eisner, University of Maryland at College Park (seisner1@umd.edu)
Atmospheric forcing is known to drive annual cycles of phytoplankton dynamics in both the open oceans and the continental margins. Much attention has been paid to the role of subseasonal (10-30 day) variability in atmospheric forcing on the initiation of spring phytoplankton blooms in the North Atlantic, indicating that subseasonal changes in net surface heating may contribute to a restratification of the upper mixed layer and thus initating a spring bloom. However, the effects of subseasonal forcings on late summer and early fall phytoplankton dynamics have yet to be explored in the same detail. A 1/12 deg. coupled physics-sea ice-biogeochemistry Northwest Atlantic regional model is used to explore the late summer dynamics of phytoplankton biomass and Nitrogen inventory in the Grand Banks of Newfoundland. During the control run, a series of biomass accumulation events in July-August 2015 were identified and associated with a passing storm event which included elevated surface wind stress and net surface cooling. Sensitivity experiments were then conducted in which the subseasonal component (<30 days) of wind stress, surface air temperature, and surface humidity were removed from the forcing to assess their individual roles on the biomass accumulation events. The removal of subseasonal wind stress was associated with a 21% decrease in peak total Nitrogen, while the peak phytoplankton biomass only saw a 2% decrease, indicating that subseasonal surface wind stress alone could not account for the rapid increase in nutrient inventory and phytoplankton biomass that was observed.
06:00 PM
BENTHOPELAGIC ZOOPLANKTON DIEL VERTICAL MIGRATION PATTERNS USING A TWO-DECADE NEAR-CONTINUOUS RECORD OF ACOUSTIC DOPPLER PROFILER IN THE ONSLOW BAY SHELF, NC (9293)
Primary Presenter: Matt Bues, University of North Carolina at Wilmington (mb8003@uncw.edu)
Demersal zooplankton bridge benthic and pelagic ecosystems during their daily (diel) vertical migrations (DVM). Typically, zooplankton emerge from the benthos into the water column at night and return to the seafloor during daytime. This movement is difficult to study because it requires continuous sampling over extended periods of time. The movement of planktonic particles can be inferred using seafloor mounted acoustic doppler current profilers (ADCP). UNCW’s Coastal Ocean Research and Monitoring program has an ADCP at 27m depth recording at a 1m vertical and 30-minute temporal resolution. Using acoustic target strengths, we can track the vertical movement of particles since recording started in April 2000 to date. Using this dataset, we asked the question of whether DVM patterns changed seasonally along with trends of planktonic production typical of Onslow Bay. As expected, DVM signals followed the typical pattern: up at night and at depth during daylight. However, what this dataset revealed was that this pattern shifts in time. The timing at which demersal plankton returned to the benthos became progressively later in the day, from earlier in productive months to later in the less productive months. We found that this dataset can be used to further explore bentho-pelagic coupling and how this phenomenon may affect biologic oceanographic processes. Long-term climatology of these diel shifts can help understand trophic dynamics from mesozooplankton to ichthyoplankton temporal and spatial patterns in shallow productive shelves such as those impacted by the Gulf Stream.
06:00 PM
Marine carbon dynamics in a coral reef ecosystem of Southern Taiwan (8863)
Primary Presenter: Pei-Jie Meng, National Dong Hwa University (pjmeng@gms.ndhu.edu.tw)
The ocean is the planet’s largest carbon reservoir and plays a crucial role in regulating atmospheric CO2 levels, especially in the face of climate change. In coral reef ecosystems, understanding the carbonate system is critical for predicting and mitigating the impact of ocean acidification on these vulnerable marine ecosystems, especially as atmospheric CO2 concentrations continue to rise. This study measured pCO2 over space and time in Nanwan Bay, a coral reef ecosystem in southern Taiwan, to identify factors that influence its variation. The results showed that mean surface water pCO2 values varied seasonally, with values of 393.7 (±10.8), 406.3 (±16.1), 399.2 (±18.6), and 366.9 (±14.5) μatm in spring, summer, fall, and winter, respectively. These seasonal mean differences (ΔpCO2) relative to atmospheric pCO2 were -2.3 (±10.8), 14.3 (±16.1), 7.2 (±18.6), and -29.1 (±14.5) µatm, respectively. These findings suggest that the Nanwan Bay is a highly dynamic coral reef ecosystem, exhibiting both spatial and seasonal variability in carbon exchange. The carbonate system parameters of the surface water in this high-biodiversity, sub-tropical marine ecosystem was influenced not only by seasonal temperature variation but also by vertical mixing, intermittent upwelling, and biological effects.
SS36P - Coast-to-boundary current systems and the ecological, biogeochemical, and physical processes within
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A