Natural, episodic processes such as eddies, fronts, upwelling, storms, hurricanes, as well as irregular anthropogenic-driven oil spills or pollutant release are common disturbances in marine and limnetic ecosystems. These processes occur at fine-scale temporal and/or spatial resolution and thus are not currently resolved in modern Earth System Models that are used to project future climate scenarios. Many of these processes are becoming more frequent and are intensifying under ongoing climate change, so it is increasingly important to understand their effects. These events disproportionately impact aquatic systems by providing anomalous “pulses” of nutrients or an altered physical environment that microbial communities respond to. However, the impact of such pulses on microbial communities is difficult to capture and synthesize because of variable characteristics of the physical disturbance, rapid changes to biogeochemistry, and potentially unknown pre-existing local environmental conditions. In this session, we invite submissions that quantitatively link episodic or irregular fine-scale forcings with geochemical changes and the microbial response (bacteria, archaea, and/or eukaryotes) within marine and limnetic ecosystems. We highly encourage submissions that use observational surveys of microbial communities (e.g., ‘omics, flow cytometry, and microscopy) to perform a detailed assessment of the biological response to pulsed physical disturbances. Of particular interest are examinations of the duration of the microbial response to the disturbance, the variability of the response to a particular type of disturbance, a comparison of the response between different types of disturbances, or links between changes within the microbial community to changes in ecosystem level processes.
Lead Organizer: Melissa Brock, University of California - San Diego (mlbrock@uci.edu)
Co-organizers:
Alexandra Jones-Kellett, Massachusetts Institute of Technology (jonesae@mit.edu)
Christopher Olivares, University of California - Irvine (chris.olivares@uci.edu)
Presentations
06:00 PM
THE EFFECTS OF EXTREME HYDROLOGIC DISTURBANCE EVENTS ON PHYTOPLANKTON COMMUNITY DYNAMICS IN SHALLOW DYSTROPHIC LAKES (8814)
Primary Presenter: Rachel Cray, University of Vermont (rcray@uvm.edu)
Phytoplankton act as ecosystem sentinels in lakes where community structure, biomass, and primary production are rapidly affected by disturbance events. Over July 10-11th during both 2023 and 2024 the Northeast U.S. experienced high intensity precipitation events leading to catastrophic flooding and extensive ecosystem change across the region. Here we assess the effects of precipitation rate and quantity on phytoplankton community dynamics in two dystrophic, shallow lakes over two years. We integrated discrete bi-weekly sampling with high frequency temperature and dissolved oxygen measurements in two Vermont climate-sentinel lakes. We characterized water chemistry and phytoplankton community structure during the ice-free periods of 2023 and 2024. Both lakes are shallow with minimal watershed development and no artificial water-level fluctuations. They differ in annual mixing regimes (dimictic and polymictic, respectively) and amount of precipitation during the two flood events. In both lakes phytoplankton biomass decreased with increased volume of precipitation within 30 days. Biomass of mixotrophic taxa, however, either increased or remained stable following extreme hydrological events across both sites. Our results suggest that slow growing, complex, colonial mixotrophs may be more resistant or resilient to extreme hydrologic disturbance events than obligate autotrophs in small dystrophic lakes. These findings have important implications for biogeochemical processing in these systems as the frequency and intensity of extreme events increases with climate change.
06:00 PM
THE INFLUENCE OF PHYSICAL PROCESSES ON PHYTOPLANKTON COMMUNITY STRUCTURE IN THE GALAPAGOS ARCHIPELAGO (9402)
Primary Presenter: Margarita Lankford, University of North Carolina at Chapel Hill (mlankford@unc.edu)
Phytoplankton are responsible for half of the total oxygen production, and are a key contributor to sequestering carbon dioxide from the atmosphere. Different groups of phytoplankton (diatoms, dinoflagellates, green algae, cyanobacteria) compete for the same growth-limiting resources - light and nutrients - but each group of primary producers employs a set of unique strategies, which allows diverse communities to co-exist in time and space. Physical processes and local topography of the Galápagos Archipelago play an important role in shaping plankton community composition by establishing unique nutrient delivery regimes favoring specific phytoplankton functional traits. The spatiotemporal scales of these regimes vary from intermittent localized nutrient bursts lasting a few days in the island wake areas to consistent high concentrations of nutrients sustained over several months over tens of kilometers in the Equatorial Undercurrent upwelling zone. To achieve deeper understanding of the bottom-up controls on primary productivity, we will integrate observations from a vertical profiling platform, along with experimental measurements from multiple groups of phytoplankton cultures recently isolated from areas associated with upwelling, island wakes and internal tides into a modeling framework to characterize the biological response to different nutrient delivery modes. Establishing the link between physical processes and biological response will enhance our understanding of the resilience of the Galápagos Archipelago marine ecosystem in the face of climate change.
06:00 PM
SPATIOTEMPORAL VARIATION IN MICROBIAL ACTIVITY IN INTERMITTENT STREAMS IN THE SOUTHEASTERN UNITED STATES (9545)
Primary Presenter: Andrielle Larissa Kemajou Tchamba, University of Mississippi (akemajou@go.olemiss.edu)
Microbial processes in streams fluctuate with changes in nutrient availability, organic matter, temperature, hydrology, and land use. To investigate drivers of microbial processes in intermittent streams, we studied the ability of streambed microbial communities to metabolize organic material in streams in three different geological regions in Alabama. Leaf litter and sediment were collected from Pendergrass, Burks Creek, and Shambley Creek over six seasons (March 2022 to January 2024). We measured the activity of microbial enzymes involved in organic carbon degradation (β-glucosidase, phenol oxidase, peroxidase) and organic phosphorus (phosphatase) and nitrogen (N-acetylglucosaminidase) mineralization. Microbial enzyme activity was significantly greater in leaf litter than sediment across all streams and seasons, with rates ranging from 4.6-24.2 μmol/h/g and 0.04-1.1 μmol/h/g, respectively. Stream, season, and sample type influenced phenol oxidase and peroxidase activity, with phenol oxidase activity greatest in Burks Creek’s leaf litter and peroxidase activity greatest in Shambley Creek sediment. Activities of β-glucosidase and N-acetylglucosaminidase peaked in summer and were lowest in spring, with Burks Creek showing the lowest activity. Water availability and season affected enzyme activity in Shambley and Burks Creek sediment. Enzyme activity in sediment varied more between streams than that of leaf litter, irrespective of season. This highlights the complexity of microbial functioning and the factors driving these processes in intermittent streams.
06:00 PM
INCREASING THE DETECTION OF VIBRIO SPP. IN A TROPICAL ESTUARINE ENVIRONMENT VIA ENRICHMENT DEPENDENT HIGH THROUGHPUT SEQUENCING AND QPCR METHODS (9249)
Primary Presenter: Mara Cuebas Irizarry, Environmental Protection Agency (cuebasirizarry.mara@epa.gov)
Identification of potential pathogens that pose human health risk in recreational waters is necessary to provide in-depth water quality assessments. Despite the advances in NGS techniques, limited information can be obtained for pathogen detection due to low concentrations in the environment. Here, we show a workflow for detection of Vibrio species in a tropical environment: San Juan Bay Estuary (SJBE) in Puerto Rico. SJBE is actively utilized for recreational purposes and frequently experiences flooding of areas with compromised sanitary sewage infrastructure. Water samples were collected from 2021-2023 from 16 sites across the estuary. To increase the detection of species in low abundance, samples from 2023 were enriched using peptone broth for 24 hours at 37°C and a parallel unenriched sample for further comparison in 16S amplicon sequencing. High throughput 16S rRNA amplicon sequencing from the enriched samples revealed the presence of 9 species of Vibrio. qPCR analysis of the unenriched samples indicated that Vibrio cholerae ranged from 2 to 27 gene copies/ml in highly urbanized areas impacted by constant breaches in the sanitary system. 16S rRNA amplicon sequencing of unenriched samples is expected to reveal less detection of Vibrio spp and the detection of pathogenic Vibrio via PCR is underway. This workflow allows us to increase potential pathogen detection, specifically for Vibrio spp. in this estuary system. Quantification and identification methods are helpful to develop mitigation strategies to reduce contamination and decrease public health risk.
SS09P - Microbial responses to pulse disturbances in aquatic environments
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A