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Iron and iron‐binding ligands as cofactors that limit cyanobacterial biomass across a lake trophic gradient
Author(s) -
Sorichetti Ryan J.,
Creed Irena F.,
Trick Charles G.
Publication year - 2016
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/fwb.12689
Subject(s) - eutrophication , trophic level , biomass (ecology) , trophic state index , nutrient , environmental chemistry , ecology , cyanobacteria , phosphorus , phytoplankton , biology , environmental science , chemistry , genetics , organic chemistry , bacteria
SummaryThe frequency and intensity of cyanobacterial blooms (cyanoblooms) is increasing globally. While cyanoblooms in eutrophic (nutrient‐rich) freshwater lakes are expected to persist and worsen with climate change projections, many of the ‘new’ cyanobloom reports pertain to oligotrophic (nutrient‐poor) freshwater lakes with no prior history of cyanobloom occurrence. Iron ( F e) is required in nearly all pathways of cyanobacterial macronutrient use, although its precise role in regulating cyanobacterial biomass across a lake trophic gradient is not fully understood. In all lakes sampled representing a gradient in trophic status from oligotrophic to hypereutrophic (2.2–561.2 μg L −1 total phosphorus), the relative cyanobacterial biomass was highest at low predicted Fe bioavailability in eutrophic A lberta lakes (<1.0 × 10 −22 mol L −1 ) and low F e concentration in oligotrophic O ntario L akes (<3.2 μg L −1 ). Fe‐binding organic ligands were measured within this range of low bioavailable F e. Concentrations of ligands with reactive hydroxamate moieties were positively correlated to cyanobacterial biomass in lakes with low F e bioavailability and supply, suggesting a possible cellular origin (i.e. siderophores) mediated by low F e. These findings suggest that F e serves as a possible cofactor that maintains cyanobacterial biomass across a lake trophic gradient and that cyanobacteria invoke a similar F e‐scavenging system to overcome F e limitation in lakes of all trophic states.