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
02:30 PM
Coastal microbial community response to Hurricanes Helene and Milton (9733)
Tutorial/Invited: Invited
Primary Presenter: Margaret Mars Brisbin, University of South Florida (mmarsbrisbin@usf.edu)
The increasing frequency and severity of landfalling tropical cyclones pose significant risks to communities, economies, and ecosystems worldwide. In 2024, hurricanes Helene and Milton wreaked havoc on Florida's coastal regions, particularly around Tampa Bay, causing extensive damage and reshaping nearshore ecosystems. Following the storms, satellite observations indicated an emerging coastal phytoplankton bloom, prompting the rapid organization of a research cruise to evaluate the plankton community and identify factors driving bloom development. Using high-throughput autonomous imaging microscopy (PlanktoScope), we found a dense diatom bloom within and immediately adjacent to Tampa Bay. However, as we moved offshore, diatoms gradually declined, giving way to the harmful algal bloom (HAB) dinoflagellate Karenia brevis, which was replaced by small flagellates further offshore. We collected surface and near-bottom seawater and sequentially filtered samples for size-fractionated community nucleic acid analysis, while separate aliquots were preserved for flow cytometry to enumerate bacterial cells. RNA sequencing will reveal active micro- and nano-eukaryotic community structure and investment, and provide insight into particle-associated and free-living bacterial communities linked to distinct phytoplankton populations. Our results will highlight the impacts of major hurricanes on coastal microbial ecology and reveal potential downstream effects on ecosystem processes, including altered carbon cycling or increased pathogenicity.
02:45 PM
PHYTOPLANKTON RESPONSES TO TROPICAL CYCLONE EVENTS: INSIGHTS FROM DISCRETE AND CONTINUOUS WATER QUALITY MONITORING IN LOUISIANA ESTUARIES (9481)
Primary Presenter: Beth Stauffer, University of Louisiana at Lafayette (beth.stauffer@louisiana.edu)
The effects of tropical cyclones on phytoplankton biomass and community structure in the coastal ocean vary with storm characteristics (i.e., wind v. runoff) and with prior conditions of the ecosystem (i.e., stratified v. well-mixed water column). A recent meta-analysis suggests that phytoplankton are sensitive to rainfall delivered to coastal ecosystems and show tradeoffs between resistance and resilience to these pulse disturbance events. Since 2019, monthly sampling data has been collected at 2 nearshore estuarine sites along the south-central Louisiana coast for water quality, phytoplankton biomass, and community composition. Since 2022, data has been collected from 5 estuarine sites via continuous sondes measuring abiotic variables (including nitrate at 1 site) and biomass of total phytoplankton (as chlorophyll-a) and freshwater cyanobacteria (as phycocyanin) every 15 minutes. Eleven named tropical cyclone systems have impacted the Louisiana coast since 2019, while additional flood (2019), unnamed storm (2024), and drought (2023) events also occurred. In 2024, Hurricane Francine made landfall in Terrebonne Parish. In the 1-2 days around landfall, a site 120 miles west showed a substantial, but temporary, increase in biomass. Conversely, a site 160 miles east showed little change during the storm, but biomass increased one week after landfall as falling salinity indicated runoff. Insights from individual pulse disturbances on phytoplankton dynamics, along with aggregated responses to disturbance characteristics, will be further discussed in this presentation.
03:00 PM
EFFECTS OF STORM SURGES ON SALT MARSH MICROBIAL COMMUNITIES (9192)
Primary Presenter: Mike Smykala, Carl von Ossietzky Universität Oldenburg (mike.jan.smykala@uni-oldenburg.de)
Microbial communities in salt marshes play a central role in nutrient cycling, primary production, and the resilience of the ecosystem. The present study examines the impact of storm surges on microbial community dynamics. The research was conducted on experimental islands in the back-barrier tidal flats of Spiekeroog, Germany, constructed in 2014 with different height levels corresponding to salt marsh zones (pioneer, lower, and upper). Samples were obtained from islands initially devoid of vegetation and from that were transplanted with lower salt marsh sediments and plants. Sampling was conducted in prior to the storm season (September 2022), immediately after (March 2023) and following a recovery time of five months (August 2023). Aiming at assessing microbial resistance, and recovery, we analyzed 16S prokaryotic DNA, 18S eukaryotic DNA, pigment composition, prokaryotic abundance, and extracellular polymeric substances. Results show differences in terms of resistance and recovery success in algae and bacterial biomass between the initially bare and transplanted islands. The lower the elevation the less resistant was the microbial community in terms of biomass, in addition the transplanted islands always showed a higher resistance than initially bare islands. The storm surges caused community composition to change in dependence to elevation and initial vegetation. The present study offers insights into the microbial dynamics of the Wadden Sea, elucidating their response to large-scale disturbances and enhancing our comprehension of coastal ecosystems.
03:15 PM
INFLUENCES OF PRECIPITATION-DRIVEN NITROGEN INPUTS ON PHYTOPLANKTON AND MICROBIAL ASSEMBLAGES IN URBAN ESTUARIES (9570)
Primary Presenter: Dianne Greenfield, City University of New York (secretary@aslo.org)
Urban estuaries, such as those surrounding New York City (NYC), tend to be chronically enriched by anthropogenic nitrogen (N) inputs from wastewater, runoff, atmospheric deposition, and other sources. In the NYC region, much wastewater comes from combined sewer overflow (CSO) systems which directly discharge to adjacent rivers and embayments causing ecosystem impairments such as algal blooms and hypoxia. Despite significant advancements toward quantifying and managing NY/Connecticut (CT) N-loadings, the spatio-temporal dynamics of associated phytoplankton and bacterial communities remain understudied. This is complicated by acute ‘pulse’ inputs from storm-induced CSO events that deliver bacterial, nutrient, and pollutant contamination to rivers such as the Hudson River Estuary (HRE) and Newtown Creek (NC), as well as estuaries such as Long Island Sound (LIS). As climate change is predicted to increase storm frequency and intensity, elucidating linkages between precipitation, N-inputs, and both microbial and biogeochemical responses is critical for enhancing coastal ecosystem resilience. Through manager, stakeholder and collaborator partnerships, we have been conducting multi-year surveys of LIS physical water quality, ecological (bacteria, phytoplankton), and biogeochemical (nutrients) features. We recently expanded measurements to include the HRE and NC, both Superfund sites that are heavily used by surrounding communities for recreation. Here we quantify how episodic rainfall influences the NYC urban microbiome in relation to proximity to CSO outfalls.
03:30 PM
Metagenomic and metatranscriptomic insights into the metabolic capabilities of sediment microbial communities in oligotrophic Lake Superior (9503)
Primary Presenter: Chan Lan Chun, University of Minnesota Duluth (chun0157@d.umn.edu)
Sediment microbes drive many core ecosystem functions and influence the fate of contaminants in freshwater ecosystems. Despite their importance, the interactions within these diverse assemblages remain underexplored, especially in oligotrophic lakes such as the Laurentian Great Lake Superior. As part of the Great Lakes Sediment Surveillance Program, we examined the abundance, diversity, and metabolic pathways of microbial communities in surface sediments of oligotrophic Lake Superior. Using metagenomic and metatranscriptomic approaches, we identified patterns and mechanisms of carbon, nitrogen, and sulfur cycling across the lake’s sediments. Our results show that Lake Superior sediments harbor aerobic, catalase- and oxidase-positive genera including nitrifiers, ammonia oxidizers, sulfur oxidizers, and methanotrophs. These findings align with the predominance of aerobic chemoheterotrophic, methylotrophic, and methanotrophic metabolisms that would be expected considering the sediment’s electron-accepting conditions. While abundances for different metabolic pathways did not significantly differ across offshore sediments, photosynthetic and oxidative phosphorylation genes were expressed in sediments collected near river mouths, which also exhibited unique community structures compared to offshore sediments. This study improves our understanding of metabolic capabilities of sediment microbial communities in low-nutrient lakes, serving as baseline information for assessing how microbially driven biogeochemical processes respond to anthropogenic stressors in Lake Superior and potentially across the Laurentian Great Lakes.
03:45 PM
Evaluating the Impacts of Nutrient Enrichment and Connectivity on Freshwater Bacterioplankton Community Composition (9698)
Primary Presenter: Akhil Kholwadwala, McGill University (akhil.kholwadwala@mail.mcgill.ca)
It is increasingly important to understand the response of freshwater ecosystems to fertilizers given their widespread usage and the propensity for these fertilizers to runoff into rivers and lakes. At the foundation of these freshwater ecosystems are bacterioplankton which play important roles as primary producers and in recycling organic matter and nutrients back into the ecosystem. To investigate the impacts of nutrient enrichment on freshwater bacterioplankton communities, we treated freshwater mesocosms–supplied with freshwater and native planktonic communities from a nearby lake–with different concentrations of nutrients (KH2PO4, K2HPO4, KNO3). We likewise tested the simultaneous impacts of connectivity/dispersal which, through the steady reintroduction of unaffected communities, is thought to have potentially remediating effects. We found that nutrient enrichment, even at its lowest levels, strongly structures the native bacterioplankton community. We further found that nutrient enrichment significantly lowers the alpha-diversity of bacterioplankton communities irrespective of the level of connectivity from an unenriched source. Taken together, our results demonstrate that nutrient enrichment significantly impacts freshwater bacterioplankton communities with enrichment favoring nutrient-tolerant taxa such as cyanobacteria. Furthermore, our results ultimately put into question the ability of connectivity and dispersal to counteract the effects of nutrient enrichment and other stressors.
SS09B - Microbial responses to pulse disturbances in aquatic environments
Description
Time: 2:30 PM
Date: 30/3/2025
Room: W205CD