Microbial metabolisms drive many important biogeochemical processes in all aquatic ecosystems. In turn, microbial activity depends on the availability of nutrients like carbon, nitrogen, or phosphorus, which can also profoundly affect microbial community assembly. Recent technological advances in microbial and biogeochemical techniques have provided novel insights into the coupling between microbial activity and geochemistry, but it remains challenging to predict the effects of present and future environmental changes. Sequencing approaches such as metagenomics have opened the “black box” of environmental microbiology, using the presence of key genes to predict the metabolism of novel microbes. However, a disconnect still exists between connecting in situ geochemical measurements, such as nutrient cycling rates and fluxes, with the genetic potential of resident microbial communities.
This session highlights advances in linking aquatic geochemistry and microbiology. Any work related to microbial processes and biogeochemistry is welcome; methods from both fields need not be included in each presentation, as long as data has relevance to both microbes and biogeochemistry. For instance, studies of biogeochemical rate measurements or models are welcome, provided they are focused on microbially-driven processes, and as are studies solely on microbial ecology but focused on microbes with biogeochemical relevance. Studies may include field sampling, method development, computational analysis, and/or modeling. Biogeochemical focus may include any cycles and processes, including “traditional” cycles as well as other aquatic contaminants such as antimicrobial resistance genes, pharmaceuticals, PFAS, and others. We welcome submissions studying any aquatic ecosystem, whether freshwater, brackish, or marine, and including benthic and/or water column data. Studies including microbial data may use broad community-level data or targeted experiments with specific populations or species. We take a broad definition of “microbe” and welcome studies of archaea, bacteria, eukaryotic microbes, and viruses. In individual presentations or in the session as a whole, we strive to bring together interdisciplinary work using a variety of approaches to explore the intersection of aquatic microbial ecology and biogeochemistry and integrate knowledge from disparate fields and a wide range of ecosystems.
Lead Organizer: Julian Damashek, Hamilton College (jdamashe@hamilton.edu)
Co-organizers:
Benjamin Kramer, University of Minnesota Duluth (bjkramer@umn.edu)
Cody Sheik, University of Minnesota Duluth (cssheik@d.umn.edu)
Annika Mosier, University of Colorado Denver (annika.mosier@ucdenver.edu)
Presentations
05:30 PM
IRON-DEPENDENT AMMONIA OXIDATION IN DEVIL’S BATHTUB, A FERRUGINOUS MEROMICTIC LAKE. (7927)
Primary Presenter: Bethany Mangioni, Niagara University (bethanyrose203@gmail.com)
Meromictic lakes are permanently stratified with anoxic monimolimnia. Our study site, Devil’s Bathtub (DBT) in Rochester, NY, is a ferruginous meromictic lake with high concentrations of iron and nitrogen compounds in the monimolimnion. In contrast to the thermodynamic expectations, nitrate and nitrite exceed the ammonia concentrations. This suggests that ammonia oxidation to nitrate or nitrite is occurring, but the source is unexplained. Due to lack of oxygen in the monimolimnion, ammonia oxidation would require a different electron acceptor, which based on the redox state and availability could be Fe(III). Ferric iron is regenerated at the surface and sinks to the bottom which then could fuel the ammonia oxidation. We hypothesize that iron-dependent ammonia oxidation is responsible for the observed geochemical profiles and meromixis, either through feammox, an energy metabolism coupling these reactions, or by separate taxa carrying out iron-reduction and ammonia oxidation. To determine which taxa may be responsible, we extracted DNA from the water column for 16S rRNA gene sequencing to characterize the microbial community. We found the presence of Pirelullaceae, known ammonia oxidizers, and Geobacter, an iron reducer. Our next step will be to use RT-qPCR to assess expression of marker genes for iron reduction and ammonia oxidation. This relatively understudied redox pair may contribute to the biogenic meromixis of DBT and give us insight to a better understanding of iron-nitrogen interactions in eutrophic conditions.
05:30 PM
Metagenomics-informed community structure of photoautotrophs in meromictic Green Lake (7932)
Primary Presenter: William Edwards, Niagara University (wje@niagara.edu)
Green Lake is an euxinic, meromictic lake producing unique sulfur and carbon cycling. Its bacterial community includes sulfur oxidizers, photosynthetic green and purple sulfur bacteria, and cyanobacteria capable of both oxygenic and anoxygenic photosynthesis, previously described using 16S rDNA sequencing in the context of its geochemistry. Here, we couple community 18S and 16S rDNA and geochemistry with concurrent metagenomics and 16S rRNA sequencing. The mixolimnion prokaryotic phototrophs were a mix cyanobacteria, primarily Synechococcus, transitioning to Chlorobium and Chromatium below the chemocline with increasing sulfide concentrations. Other anoxygenic photosynthetic capable cyanobacterial taxa included Phormidium, Leptolyngbya, and Oscillatoria. Eukaryotic phototrophs included gymnodinian dinoflagellates, restricted to the surface, and cryptomonads throughout the mixolimnion. Many cryptomonad taxa have demonstrated sulfide tolerance and migration into sulfide rich layers in other lakes, which may explain the disparate distribution. The Synechococcus assembled genome included sqr genes which enable sulfide detoxification and anoxygenic photosynthesis. The Synechococcus persisted below the increase in sulfide, but decreased abruptly, corresponding to changes in cyanobacterial phage abundance. Green Lake photosynthesis was dominated by sulfide tolerant eukaryotes and cyanobacteria, and sulfide mediated anoxygenic photosynthesis, further detailing our understanding of sulfur and carbon cycling in euxinic, meromictic lakes.
05:30 PM
Mapping microdiversity structure of deep water-adapted Chloroflexi across the Laurentian Great Lakes (8164)
Primary Presenter: Jessica Hart, University of Chicago (hartjl@uchicago.edu)
A globally abundant and poorly understood deep-water inhabitant of pelagic freshwater systems is Anaerolineae lineage CL500-11, an uncultivated bacterium in the Chloroflexi phylum. Around the world, CL500-11 comprises 10-30% of the bacterial community in the hypolimnia of deep oxic lakes, including the Laurentian Great Lakes (LGL). Here we use metagenome-assembled genomes (MAGs) to quantify and map the microdiversity structure of CL500-11 across the physiochemically heterogeneous LGL. In contrast to abundant marine surface water taxa like SAR11 and Prochlorococcus, where distinctive ecotypes are thought to support numerical dominance across environments, our CL500-11 MAGs share >99.4% average nucleotide identity, representing an extremely low diversity population throughout the LGL system. The most divergent MAGs come from Lake Erie, which is unique in nutrient load, volume, residence time, and surrounding land use among the otherwise oligotrophic LGL. This work suggests limited CL500-11 subpopulation structure even across long distances and strong environmental gradients, and it indicates the potential for deep water habitats to host unique ecological and evolutionary strategies that remain underexplored.
05:30 PM
Comparison of carbon metabolism dynamics between Lake Michigan coastal and offshore bacterial communities as assessed through metatranscriptomics (8388)
Primary Presenter: Adit Chaudhary, Rush University (adit.chaudhary89@gmail.com)
Despite their small share of Earth’s surface, freshwater ecosystems contribute significantly to regional and global carbon budgets. Bacterial communities in these ecosystems play a fundamental role in the biogeochemistry and food web dynamics. In this study, we characterized the spatiotemporal patterns in bacterial dissolved organic carbon (DOC) metabolism in Lake Michigan, one of the largest lakes in the world. Using metatranscriptomics, we investigated bacterial community gene expression across a nearshore-to-offshore transect in the lake during spring and summer seasons in 2017-2018. Comparison of transcript abundance for gene families between nearshore and offshore bacterioplankton highlighted differential expression for several genes between the two regions. Notably, genes involved in the uptake and metabolism of various DOC substrates such as amino acids and sugars were over-expressed in the offshore bacterial communities as compared to nearshore. A more detailed analysis of all the transporter genes expressed for DOC substrates revealed similar trends – a higher overall expression of DOC transporter genes in the offshore versus nearshore. These results imply that the offshore bacterial communities in Lake Michigan are more carbon limited than in nearshore and are likely spending more metabolic energy in acquiring various DOC substrates. Overall, this study provides molecular ecology-based evidence of the current oligotrophic conditions in offshore Lake Michigan, and identifies the DOC compounds that contribute to carbon flux in this valuable freshwater resource.
05:30 PM
GLOBAL DISTRIBUTIONS OF FRESHWATER AMMONIA-OXIDIZING ARCHAEA BASED ON ANALYSIS OF THOUSANDS OF METAGENOMES (8350)
Primary Presenter: Reilan Garczynski, Hamilton College (rgarczyn@hamilton.edu)
Reilan Garczynski Julian Damashek The high abundance of ammonia-oxidizing archaea (AOA) in oligotrophic marine waters and soils, along with physiological data from cultivated strains, suggests many thrive in low-nutrient environments, yet studies in freshwaters have found abundant and diverse AOA in both low- and high-nutrient waters. To determine global ecological patterns of freshwater AOA, we competitively mapped >100 billion sequences from >1,900 lake, river, and stream water metagenomes to a genome database of all Nitrososphaeria (formerly “Thaumarchaeota”) genomes in GTDB. We then summarized the relative abundance of Nitrososphaeria genera and metagenomic operational taxonomic units (mOTUs, consisting of genomes with ≥95% average nucleotide identity). Overall, metagenomes from tropical systems and deep lakes consistently had the highest relative AOA abundance. There were distinct groups of metagenomes with highly abundant and low-diversity communities of Nitrosotenuis, Nitrosotalea, or Nitrosoarchaeum. For example, many equatorial waters had large AOA communities composed almost entirely by Nitrosotenuis, often dominated by a single mOTU related to MAGs from the Amazon River. However, many other environments had far greater archaeal diversity, including a mix of genera commonly found in acidophilic, terrestrial, and marine environments. This study demonstrates the power of large meta-analyses to help identify the global ecology of specific microbial lineages.
05:30 PM
DETERMINING NITROGEN INPUTS TO THE MOHAWK RIVER AND ITS WATERSHED BY SYNTHESIZING BIOGEOCHEMISTRY, FECAL SOURCE TRACKING, AND GEOSPATIAL ANALYSIS (8158)
Primary Presenter: Lilianna Gross, Hamilton College (Liliannaxg3@gmail.com)
The Mohawk River (Teionontatátie) flows along the Erie Canal through upstate New York and is the largest tributary to the Hudson. Given the widespread use of the river and its tributaries for drinking water, sanitation, and recreation, it is critical to understand the drivers of water quality throughout the Mohawk watershed, which is predominantly forested or agricultural but also includes significant urban inputs. Our focus is on nitrogen (N), an understudied aspect of Mohawk River water quality that has effects on productivity, eutrophication, and toxic algal blooms. Data from the river, tributaries, and nearby lakes indicate high N throughout much of this watershed, with elevated nitrate in waters draining agricultural land and higher levels of ammonium and urea near urban sources. To further quantify nutrient sources, we synthesized nutrient data with qPCR-based human and cattle fecal source tracking, as well as geospatial data on land use/land cover. Unlike nearby lake sites, the majority of river and stream samples had nitrogen to phosphorus (N:P) ratios above the Redfield ratio, indicating a more thorough analysis of nutrient limitation is warranted. Microbial sequence data shows numerous stretches of the Mohawk River and tributary creeks contain significant communities of cyanobacteria, including many families with known toxic species. These data suggest numerous N sources are sustaining elevated N concentrations in the Mohawk River and allow us to pinpoint sources of specific N compounds, linking water quality to surrounding land use.
05:30 PM
NITROGEN FIXATION AND TOXIN PRODUCTION IN APHANIZOMENON FLOS-AQUAE UNDER VARIABLE N:P:FE STOICHIOMETRY (7790)
Primary Presenter: Sara Coppellotti, Baylor University (sara_coppellotti1@baylor.edu)
Current research indicates that free nitrate and iron concentrations in waterbodies impact nitrogen fixation as well as cyanotoxin production in cyanobacteria species. The purpose of this experiment was to analyze the effects of nitrogen addition through stoichiometric relationships with respect to iron and phosphorus levels in Aphanizomenon flos-aquae PCC 7905[TH1] . Because Aphanizomenon flos-aquae is a diazotrophic species, we hypothesized that we would observe a tradeoff in which the samples grown in low nitrogen conditions would decrease in toxin production[TH2] and increase in nitrogen fixation. We tested this hypothesis with a laboratory experiment where we manipulated N:P treatments of 1, 5, 10, 20, and 50 at low iron and high iron concentrations. Gene expression encoding for both toxin production and nitrogen fixation were measured using qPCR following a 28-day experiment and subsequent 48-hr modification. Preliminary data indicated that N fixation may have offset N deficiency and elevated biomass in low N treatments. We will show data on the biomass, stoichiometry, and gene expression rates from our final sample analysis.
05:30 PM
Spatial-temporal variations of the groundwater chemistry and microbiology as resulted from the operation of groundwater heat pump system – a field heat injection test (8232)
Primary Presenter: Charis Wong, Institut national de la recherche scientifique (charis.wong@inrs.ca)
Groundwater heat pump systems (GWHP) are a promising green technology for cooling buildings. Their use is often challenging as the operation can cause disturbances to aquifer biodiversity and groundwater chemistry. Pumping can cause draw-in of dissolved oxygen in anoxic aquifers, homogenising natural depth gradient of different chemical and microbiological compositions. The resulting reactions can subsequently lead to system failure due to clogging from microbially mediated iron precipitation. Therefore, it is important to understand how the groundwater chemistry and microbiology evolve both spatially and temporally throughout the system. Field heat injection tests (HIT) were conducted to simulate its operational processes. Hierarchical clustering and principal component analyses identified different water types (chloride- or bicarbonate-water) resulted from natural processes and anthropogenic perturbations (i.e salinity, mineral dissolution, redox process). PERMANOVA revealed that microbial community composition was primarily explained by sampling depths, followed by the test phases (i.e. during HIT, recovery). Preliminary results suggested that community assembly processes corresponded well to processes caused by the HIT; where homogeneous dispersal and homogenesous selection were dominating processes under immediate perturbations, while relative fraction of heterogeneous selection increased during recovery. Further investigations of these results will provide insights in developing optimum operational regime to minimise environmental impact to the aquifer ecosystem.
05:30 PM
LEGACY EFFECTS OF PLANT COMMUNITY STRUCTURE ARE MANIFESTED IN MICROBIAL BIOFILM DEVELOPMENT WITH CONSEQUENCES FOR ECOSYSTEM CO2 FLUXES (8033)
Primary Presenter: Allison Rober, Ball State University (arrober@bsu.edu)
In this study, we evaluated how shifts in the vegetation community associated with long-term changes in water-table position influence aquatic biofilm development and carbon dioxide (CO2) flux. We quantified seasonal variation in biofilm composition and CO2 fluxes in response to lowered and raised water-table position (relative to a control) during years with varying levels of background dissolved organic carbon (DOC). We then used nutrient diffusing substrates to evaluate cause-effect relationships between changes in plant subsidies and biofilm composition among water-table treatments. We found that background concentration of DOC determined whether plant subsidies promoted net autotrophy or heterotrophy which had consequences for net CO2 flux. In conditions where background DOC was ≤ 40 mg L-1, plant subsidies promoted autotrophic biofilm development. When background DOC concentration was ≥ 50 mg L-1, plant subsidies promoted heterotrophic biofilm development. Conditions that favored autotrophic biofilm development resulted in net CO2 uptake among all water-table treatments, whereas the site was a net source of CO2 to the atmosphere in conditions that supported greater heterotrophy. Our finding suggest that drainage history interacts with changes in dominant plant functional groups to alter biofilm composition, which has significant consequences for ecosystem CO2 fluxes.
05:30 PM
EXPLORING PATTERNS OF EFFLUENT PROCESSING ACROSS SEQUENTIAL BASINS IN A RESTORED TREATMENT WETLAND (8291)
Primary Presenter: Paola Ayala-Borda, University of Lethbridge (p.ayalaborda@gmail.com)
Treatment wetlands play an important role in filtering, processing, and remediation of waste waters. Wastewater effluents are complex mixtures of many chemicals and the capacity for wetlands to remediate different organic and inorganic pollutants vary widely with environmental conditions (e.g., water retention time, redox potential, and microbial community structure and metabolism). These factors make it difficult to generalize about chemical shifts in water masses transiting through wetland habitats. Here, we explore whether chemical shifts in effluent follow predictable patterns through a multi-basin, treatment wetland in southwestern Canada. Based on known shifts in oxygen content through the wetland complex (anoxia at the effluent inflow, oxygen saturation and supersaturation in downstream habitat) we will explore whether the chemical shifts in effluent and associated biogeochemical processing follows predictable patterns based on this apparent redox gradient. These findings will provide insight into the functioning of wetlands used for effluent remediation, and the implication for ecosystem services that we obtain from these important ecosystems.
SS03P - Uncovering Links Between Aquatic Geochemistry and Microbial Communities, from Genomes to Nutrient Cycles
Description
Time: 5:30 PM
Date: 6/6/2024
Room: Madison Ballroom D