Cyanobacterial Harmful algal blooms (cHABs) continue to be reported with increasing frequency in freshwater systems globally. cHABs are a perennial issue in many eutrophic areas but occur across nutrient and temperature gradients and in many relatively unimpacted lakes. These recent changes in the distribution and severity of cHAB events challenges widely-used models that rely upon nutrient loads and autecological preferences of individual species to explain blooms. Relationships between cyanobacterial species and environmental drivers are complicated by the inherent genomic and metabolic flexibility of cyanobacteria, as well as marked taxonomic ambiguity within the division, and further confounded by environmental stochasticity, anthropogenic disturbance, and interactions with non-cyanobacterial algae and other microbes. Many of the systems that are experiencing increasing cyanobacterial dominance and associated cHAB events are not warm, eutrophic, or otherwise impacted in an absolute sense. However, many are undergoing rapid change as a result of climate change, watershed modifications, and non-indigenous species. This session will gather research and encourage discussion around blooms in unexpected places, cyanobacterial bloom formers as opportunistic species, increasing cyanobacterial relative abundance in low biomass systems, and the microbial and algal community ecology of cHABs.
Lead Organizer: Mary Anne Evans, U S Geological Survey (maevans@usgs.gov)
Co-organizers:
Elena Lichtman, Carnegie Institution for Science (elitchman@carnegiescience.edu)
Rebecca Gorney, USGS – New York Water Science Center (rgorney@usgs.gov)
Presentations
09:00 AM
CYANOBACTERIAL BLOOMS IN AN OLIGOTROPHIC LAKE: MANIFESTATION OF NOT-SO-VISIBLE MULTI-DECADAL ECOSYSTEM CHANGES (7795)
Primary Presenter: Kiyoko Yokota, State University of New York at Oneonta (kiyoko.yokota@oneonta.edu)
Freshwater cyanobacterial blooms are often associated with eutrophy and high water temperature, but lakes that are considered oligotrophic by all three major indices (chlorophyll a, total phosphorus, and Secchi depth) have been affected by recurrent cyanobacterial blooms, including when the water temperature is < 15°C. Otsego Lake, NY, USA experienced recurrent blooms of toxigenic Microcystis aeruginosa for the first time in the summer of 2022, which took the local community by surprise while the lake had continuously been invaded by a variety of non-indigenous aquatic species. The effort to control further introductions had not been fully supported financially or in terms of lake user compliance. The most serious example is the serial invasions by zebra (2007) and quagga (2018) mussels, both of which quickly colonized the entire 16 km2 lake. The altered food web structure and biogeochemical cycling as well as the unbalanced in-lake nitrogen to phosphorus (N:P) stoichiometry after successful P load reduction appear to be the main drivers that may be amplifying the effects of climate warming, reduced ice cover, and altered precipitation patterns. The Otsego Lake community is working towards a Nine Element Plan, a comprehensive lake and watershed management plan that includes both watershed and in-lake modeling, which will enable data-driven decisions for watershed management.
09:15 AM
Revisiting the drivers of eutrophication and cyanobacteria blooms in Lake Champlain’s Northeast Arm (8399)
Primary Presenter: Peter Isles, Vermont Agency of Natural Resources (peter.isles@vermont.gov)
Lake Champlain has been the focus of extensive research and investment in recent decades, as the states and provinces within the catchment have attempted to protect and improve water quality in the lake. In much of the lake, phosphorus concentrations remain stable. A notable exception is the large “Inland Sea” basin in the lake’s Northeast Arm, where phosphorus concentrations are significantly increasing and there are indications that there may be a regime shift occurring in the magnitude of seasonal internal loading. Using more than 30 years of consistent monitoring data coupled with several catchment and lake modeling approaches, we investigate lake water quality in the context of changing internal loads, spatially variable influence of external nutrient loads from several tributaries, and physical changes to the lake thermal structure resulting from climate patterns. Finally, we address the extent to which internal loading in the Inland Sea may contribute to chronic, severe cyanobacteria blooms in an adjacent shallow, eutrophic bay.
09:30 AM
CYANOBACTERIA HARMFUL ALGAL BLOOMS IN LOW-NUTRIENT NEW YORK LAKES: COMBINED APPROACHES TO ADDRESS AN EPHEMERAL PHENOMENON (7698)
Primary Presenter: Rebecca Gorney, USGS (rgorney@usgs.gov)
In response to increases in cyanobacterial harmful algal blooms (cyanoHABs) in lakes with relatively low nutrient concentrations, the US Geological Survey (USGS) has developed research projects in two areas of New York State (NY). In the Finger Lakes region, USGS conducted a pilot study in collaboration with the state Department of Environmental Conservation to assess traditional and innovative monitoring approaches. The goals were to inform future monitoring strategies and increase the understanding of factors related to the formation and proliferation of cyanoHABs. Monitoring methods included data collection platforms in open water, nearshore mapping surveys, passive samplers, multi-channel fluorescence sensors, imaging flow cytometry, and hyperspectral imagery analysis. USGS research projects being implemented within the Adirondack Park region are using water- and sediment-based methods appropriate to the challenges of capturing episodic cyanoHABs. These include measurement of cyanotoxin synthetase genes and paleolimnological approaches to investigate historical patterns. Results indicate that cyanoHAB detection in low nutrient systems is challenging. However, several lines of evidence converged to help inform observed patterns at the lake surface and within the water column within both regions. For example, two Finger Lake projects indicated the role of the thermocline in cyanotoxin dispersion through the water column. Findings across our NY-focused studies provide tools for managers and lake users to understand drivers and patterns of cyanoHABs in low nutrient systems.
09:45 AM
Vertical distribution and migration of Cyanobacteria and cyanotoxins across diel to seasonal timescales in Lake Mendota (8011)
Primary Presenter: Riley Hale, University of California, San Diego (haleriley@gmail.com)
Cyanobacteria, commonly known as “blue-green algae,” are a phylum of bacteria that produce toxic or otherwise bioactive peptides that can affect the brain, liver, and skin of humans and animals. Rapid growth of Cyanobacteria in water bodies—known as “blooms”—affect the health and recreation of many nutrient-rich lakes, including Lake Mendota (Madison, WI). Freshwater Cyanobacteria are known to grow and migrate throughout the water column to access varying light and nutrient conditions, but perceptions of blooms are often limited to lake surface observations. Many previous studies lack investigation of potential vertical heterogeneity of both Cyanobacteria and the cyanotoxins they produce, posing a challenge to water quality managers and health officials assessing the extent of toxic threat from cyanotoxins in freshwater lakes. In this study, we assess the vertical distribution and migration of Cyanobacteria and cyanotoxins in Lake Mendota on both a diel and seasonal time scale throughout the cyanobacterial growth season (May-Nov) 2021. To assess diel vertical migrations of the cyanobacterial community, we designed and constructed an in situ automated phycocyanin fluorescence water column profiler. We observed consistent yet taxonomically distinct diel migrations of Cyanobacteria throughout the epilimnion, as well as unique patterns in vertical distribution of cyanobacterial taxa across the growth season, observed via 16S rRNA gene amplicon sequencing. We also analyzed the concentration of 19 cyanotoxins using high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) from weekly depth-discrete samples and across two 24-hour diel studies. We observed high seasonality of epilimnion cyanotoxins and high variability in concentration between layers of the stratified lake. This study provides insights into potential coupled strategies for light avoidance, nutrient access, and toxin production throughout the water column. The combination of vertical measurements across time scales of hours to seasons provides a detailed characterization of the distribution and migration of cyanobacterial taxa and cyanotoxins throughout the water column.
10:00 AM
Making the watershed connection: the influence of cyanobacteria, sediment, and nutrient loading and hydrology on cyanobacterial bloom initiation in the nearshore environment (7779)
Primary Presenter: Carrie Givens, U.S. Geological Survey (cgivens@usgs.gov)
Nearshore algal blooms appearing along the southern coastline of the western arm of Lake Superior ranging from Duluth Harbor to the Apostle Islands appear to coincide with large storm events that flush sediment and nutrients from the watershed into the nearshore. The concept of “fluvial seeding” has been hypothesized, but the limited available data have not always agreed on the influence of riverine cyanobacteria on open lake algal bloom initiation. Using cultivation and genomics, our work assessed fluvial flow of cyanobacteria with nutrient and sediment loading from the Siskiwit and Bois Brule tributaries to the Lake Superior nearshore. Water and sediment samples were collected and added to selective cyanobacteria media. Additionally, DNA from environmental samples and cultivations were sent for Bacteria 16S rRNA amplicon sequencing to characterize and compare the cyanobacteria community along the tributary to nearshore continuum. Quantitative PCR targeting Cyanobacteria 16S rRNA was analyzed to determine cyanobacteria relative abundance in relation to sediment and nutrient loading. Viable cyanobacteria cells were cultivated from tributary samples and genomically similar signatures of Cyanobium, Pseudanabaena, and Nostocaceae species were detected from tributary environmental samples and cultivations. Additional data are needed to understand whether cyanobacteria seeding originates in the tributaries themselves, whether fluvial flow is simply transporting these cells to the nearshore from upstream, or if there are multiple sources seeding the nearshore.
10:15 AM
Multi-omics approach to identify a microbial biomarker for Planktothrix-dominated cyanobacterial harmful algal blooms in freshwater lakes (8432)
Primary Presenter: Dae-Wook Kang, University of Toledo (daewook.kang@utoledo.edu)
The global frequency and duration of cyanobacterial blooms are increasing, posing threats to drinking water supplies, disrupting recreational activities, and disturbing ecosystems. Planktothrix, a filamentous cyanobacterium, is responsible for blooms worldwide and produces toxic secondary metabolites. Water parameters such as temperature, pH, turbidity, and nitrogen and phosphorus concentrations have been reported to influence Planktothrix blooms. However, there is still a lack of in-depth understanding regarding key microbial players of bloom dynamics and their symbiotic and competitive interactions within Planktothrix-dominated bloom. Therefore, we conducted biweekly surveillance over a three-year period in Grand Lake St. Marys in Ohio, USA, a freshwater lake with historical dominance of Planktothrix. We analyzed physicochemical parameters, toxins, and the fungal and bacterial microbiome using amplicon sequencing, along with functional analysis using shotgun metagenomics. The integrated analysis of the multi-omics data revealed a potential interaction among nitrogen-related bacteria, methane-producing archaea, and algicidal fungi/bacteria, with carbon- and nitrogen-associated metabolic capability serving as connecting factors. In addition, Rhodobacter, a purple non-sulfur bacterium, emerged as a candidate biomarker to predict Planktothrix-dominated blooms, showing a consistent negative association with Planktothrix as well as with the toxin-producing mcyE gene abundance. Further studies to validate functional interactions across microbial players are warranted.
SS39A - cHABs as a Response to Ecosystem Disturbance
Description
Time: 9:00 AM
Date: 7/6/2024
Room: Lecture Hall