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1. Genomic signatures of Lake Erie bacteria suggest interaction in the Microcystis phycosphere

   https://doi.org/10.1371/journal.pone.0257017  

   Hoke, Alexa K. ; Reynoso, Guadalupe ; Smith, Morgan R. ; Gardner, Malia I. ; Lockwood, Dominique J. ; Gilbert, Naomi E. ; Wilhelm, Steven W. ; Becker, Isabella R. ; Brennan, Grant J. ; Crider, Katherine E. ; et al ( September 2021 , PLOS ONE)

   Humbert, Jean-François (Ed.)

   Microbial interactions in harmful algal bloom (HAB) communities have been examined in marine systems, but are poorly studied in fresh waters. To investigate HAB-microbe interactions, we isolated bacteria with close associations to bloom-forming cyanobacteria, Microcystis spp., during a 2017 bloom in the western basin of Lake Erie. The genomes of five isolates ( Exiguobacterium sp. JMULE1, Enterobacter sp. JMULE2, Deinococcus sp. JMULE3, Paenibacillus sp. JMULE4, and Acidovorax sp. JMULE5.) were sequenced on a PacBio Sequel system. These genomes ranged in size from 3.1 Mbp ( Exiguobacterium sp. JMULE1) to 5.7 Mbp ( Enterobacter sp. JMULE2). The genomes were analyzed for genes relating to critical metabolic functions, including nitrogen reduction and carbon utilization. All five of the sequenced genomes contained genes that could be used in potential signaling and nutrient exchange between the bacteria and cyanobacteria such as Microcystis . Gene expression signatures of algal-derived carbon utilization for two isolates were identified in Microcystis blooms in Lake Erie and Lake Tai ( Taihu ) at low levels, suggesting these organisms are active and may have a functional role during Microcystis blooms in aggregates, but were largely missing from whole water samples. These findings build on the growing evidence that the bacterial microbiome associated with bloom-forming algae have the functional potential to contribute to nutrient exchange within bloom communities and interact with important bloom formers like Microcystis . 

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2. Microbial communities of the Laurentian Great Lakes reflect connectivity and local biogeochemistry

   https://doi.org/10.1111/1462-2920.14862  

   Paver, Sara F. ; Newton, Ryan J. ; Coleman, Maureen L. ( December 2019 , Environmental Microbiology)

   The Laurentian Great Lakes are a vast, interconnected freshwater system spanning strong physicochemical gradients, thus constituting a powerful natural laboratory for addressing fundamental questions about microbial ecology and evolution. We present a comparative analysis of pelagic microbial communities across all five Laurentian Great Lakes, focusing on Bacterial and Archaeal picoplankton characterized via 16S rRNA amplicon sequencing. We collected samples throughout the water column from the major basins of each lake in spring and summer over 2 years. Two oligotypes, classified as LD12 (Alphaproteobacteria) and acI‐B1 (Actinobacteria), were among the most abundant in every sample. At the same time, microbial communities showed distinct patterns with depth during summer stratification. Deep hypolimnion samples were frequently dominated by aChloroflexioligotype that reached up to 19% relative abundance. Stratified surface communities differed between the colder, less productive upper lakes (Superior, Michigan, Huron) and warmer, more productive lower lakes (Erie, Ontario), in part due to anActinobacteriaoligotype (acI‐C2) that averaged 7.7% of sequences in the lower lakes but <0.2% in the upper lakes. Together, our findings suggest that both hydrologic connectivity and local selective pressures shape microbial communities in the Great Lakes and establish a framework for future investigations.

    

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3. A 420‐Year Perspective on Winter Lake Erie Levels

   https://doi.org/10.1029/2022GL099911  

   Wiles, G. C. ; Devereux, K. ; Gaglioti, B. V. ; D’Arrigo, R. D. ( January 2023 , Geophysical Research Letters)

   Here, we present a 420‐year‐long winter lake level reconstruction for Lake Erie based primarily on temperature‐sensitive tree‐ring chronologies from Alaska, Oregon, and California. This well‐verified model explains more than 51% of the variance in winter lake levels over a 131‐year calibration period (1860–1990) and shows strong decadal fluctuations related to changes in sea surface temperatures in the North Pacific and the North Atlantic, which alternate in terms of their relative influence. Decadal variability is superimposed on a persistent secular lake level rise that began in the mid‐1900s coinciding with a growing influence of the Atlantic sector. In the context of the last 420 years, the instrumental period experienced extreme lake levels, with the lowest over the entire record during the Dustbowl and the highest in 2020. Fluctuations in Lake Erie water levels are primarily determined by climate, and their variability greatly impacts the region's infrastructure and ecosystems.

    

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4. Intra‐Annual and Interannual Dynamics of Evaporation Over Western Lake Erie

   https://doi.org/10.1029/2020EA001091  

   Shao, Changliang ; Chen, Jiquan ; Chu, Housen ; Stepien, Carol A. ; Ouyang, Zutao ( November 2020 , Earth and Space Science)

   Evaporation (E) is a critical component of the water and energy budget in lake systems yet is challenging to quantify directly and continuously. We examined the magnitude and changes ofEand its drivers over Lake Erie—the shallowest and most southern lake of the Laurentian Great Lakes. We deployed two eddy‐covariance tower sites in the western Lake Erie Basin—one located nearshore (CB) and one offshore (LI)—from September 2011 through May 2016. MonthlyEvaried from 5 to 120 mm, with maximumEoccurring in August–October. The annualEwas 635 ± 42 (±SD) mm at CB and 604 ± 32 mm at LI. Mean winter (October–March)Ewas 189 ± 61 mm at CB and 178 ± 25 mm at LI, accounting for 29.8% and 29.4% of annualE. Mean dailyEwas 1.8 mm during the coldest month (January) and 7.4 mm in the warmest month (July). MonthlyEexhibited a strong positive linear relationship to the product of wind speed and vapor pressure deficit. Pronounced seasonal patterns in surface energy fluxes were observed with a 2‐month lag inEfromR_n, due to the lake's heat storage. This lag was shorter than reports regarding other Great Lakes. Difference inEbetween the offshore and nearshore sites reflected within‐lake spatial heterogeneity, likely attributable to climatic and bathymetric differences between them. These findings suggest that predictive models need to consider lake‐specific heat storage and spatial heterogeneity in order to accurately simulate lakeEand its seasonal dynamics.

    

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5. Sulfolipid substitution ratios of Microcystis aeruginosa and planktonic communities as an indicator of phosphorus limitation in Lake Erie

   https://doi.org/10.1002/lno.12333  

   Martin, Robbie M. ; Denney, Maddie K. ; Pound, Helena L. ; Chaffin, Justin D. ; Bullerjahn, George S. ; McKay, R. Michael L. ; Zastepa, Arthur ; Jones, Katarina A. ; Castro, Hector F. ; Campagna, Shawn R. ; et al ( March 2023 , Limnology and Oceanography)

   Phosphorus (P) availability frequently limits primary production in lakes, influences the physiology of phytoplankton, shapes community structure, and can stimulate or constrain the formation of cyanobacterial blooms. Given the importance of P, numerous methods are available to assess P stress in phytoplankton communities. Marine phytoplankton are known to substitute sulfolipids for phospholipids in response to P limitation. We asked whether sulfolipid substitution might serve as an additional indicator of P stress in freshwater phytoplankton communities. The question was addressed using cultures ofMicrocystis aeruginosa, Lake Erie microcosms, and surveys of lipid profiles in Lake Erie during aMicrocystisspp. bloom. Peak area response ratios of the intact polar lipids sulfoquinovosyldiacylglycerol (SQDG) to phosphatidylglycerol (PG) were used as the metric of lipid substitution. In cultures ofM. aeruginosaNIES‐843, the SQDG : PG ratio increased from ~ 0.9 to ~ 3.3 with decreasing P concentration. In P‐limited communities, the SQDG : PG ratio increased from ~ 6 to ~ 11 after 48 h in microcosm controls, while P amendments reduced the ratio to ~ 3. In Lake Erie surveys, the SQDG : PG ratio ranged from ~ 0.4 to ~ 7.4 and was negatively correlated (Pearsonr = −0.62) with total dissolved P. The SQDG : PG ratio was not correlated with concentrations of chlorophylla, soluble reactive P, or N : P molar ratios. These results demonstrated thatM. aeruginosaandMicrocystis‐dominated communities remodel lipid profiles in response to P scarcity, providing a potential short‐term, time‐integrated biomarker of nutrient history and P stress in fresh waters.

    

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