10.1021/acs.est.5b03931.s001
Matthew
J. Harke
Matthew
J.
Harke
Timothy W. Davis
Timothy W.
Davis
Susan B. Watson
Susan B.
Watson
Christopher J. Gobler
Christopher J.
Gobler
Nutrient-Controlled
Niche Differentiation of Western
Lake Erie Cyanobacterial Populations Revealed via Metatranscriptomic
Surveys
American Chemical Society
2016
Lake Erie
drinking water supplies
cyanobacterial populations
microcystin synthetase genes
cyanobacterial communities
cyanobacterial blooms
Western Lake Erie Cyanobacterial Populations Revealed
mcn gene sets
nitrogen fixation gene
abundance
Anabaena
Microcysti
2016-01-19 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Nutrient_Controlled_Niche_Differentiation_of_Western_Lake_Erie_Cyanobacterial_Populations_Revealed_via_Metatranscriptomic_Surveys/2057856
Although toxic cyanobacterial blooms
in western Lake Erie threaten
drinking water supplies and are promoted by nutrient loading, the
precise nutrient regime that selects specific cyanobacteria populations
is poorly understood. Here, we assess shifts in cyanobacterial abundances
and global gene-expression patterns in response to natural and manipulated
gradients in nitrogen and phosphorus to identify gene pathways that
facilitate dominance by different cyanobacteria. Gradients in soluble
reactive phosphorus shaped cyanobacterial communities and elicited
the largest transcriptomic responses. Under high-P conditions (closest
to the mouth of the Maumee River), Anabaena and Planktothrix were the dominant
cyanobacterial populations, and experimental P and ammonium enrichment
promoted nitrogen fixation gene (<i>nifH</i>) expression
in Anabaena. For Microcystis, experimental additions of P up-regulated genes involved in phage
defense, genomic rearrangement, and nitrogen acquisition but led to
lower abundances. Within offshore, low-P regions of the western basin
of Lake Erie, Microcystis up-regulated
genes associated with P scavenging (<i>pstSCAB</i>, <i>phoX</i>) and dominated cyanobacterial communities. Experimental
additions of ammonium and urea did not alter Microcystis abundances but did up-regulate protease inhibitors (<i>aer</i> and <i>mcn</i> gene sets) and microcystin synthetase genes
(<i>mcy</i>), with urea enrichment yielding significant
increases in microcystin concentrations. Our findings suggest that
management plans that reduce P loads alone may not significantly reduce
the risk of cyanobacterial blooms in western Lake Erie but rather
may promote a shift among cyanobacterial populations (Microcystis, Anabaena, and Planktothrix) toward a greater
dominance by toxic strains of Microcystis.