The effects of temperature and nutrients on the growth and dynamics of toxic and non-toxic strains of Microcystis during cyanobacteria blooms
In temperate latitudes, toxic cyanobacteria blooms often occur in eutrophied ecosystems during warm months. Many common bloom-forming cyanobacteria have toxic and non-toxic strains which co-occur and are visually indistinguishable but can be quantified molecularly. Toxic Microcystis cells possess a...
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Published in | Harmful algae Vol. 8; no. 5; pp. 715 - 725 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Kidlington
Elsevier B.V
01.06.2009
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | In temperate latitudes, toxic cyanobacteria blooms often occur in eutrophied ecosystems during warm months. Many common bloom-forming cyanobacteria have toxic and non-toxic strains which co-occur and are visually indistinguishable but can be quantified molecularly. Toxic
Microcystis cells possess a suite of microcystin synthesis genes (
mcyA–
mcyJ), while non-toxic strains do not. For this study, we assessed the temporal dynamics of toxic and non-toxic strains of
Microcystis by quantifying the microcystin synthetase gene (
mcyD) and the small subunit ribosomal RNA gene, 16S (an indicator of total
Microcystis), from samples collected from four lakes across the Northeast US over a two-year period. Nutrient concentrations and water quality were measured and experiments were conducted which examined the effects of elevated levels of temperatures (+4
°C), nitrogen, and phosphorus on the growth rates of toxic and non-toxic strains of
Microcystis. During the study, toxic
Microcystis cells comprised between 12% and 100% of the total
Microcystis population in Lake Ronkonkoma, NY, and between 0.01% and 6% in three other systems. In all lakes, molecular quantification of toxic (
mcyD-possessing)
Microcystis was a better predictor of
in situ microcystin levels than total cyanobacteria, total
Microcystis, chlorophyll
a, or other factors, being significantly correlated with the toxin in every lake studied. Experimentally enhanced temperatures yielded significantly increased growth rates of toxic
Microcystis in 83% of experiments conducted, but did so for non-toxic
Microcystis in only 33% of experiments, suggesting that elevated temperatures yield more toxic
Microcystis cells and/or cells with more
mcyD copies per cell, with either scenario potentially yielding more toxic blooms. Furthermore, concurrent increases in temperature and P concentrations yielded the highest growth rates of toxic
Microcystis cells in most experiments suggesting that future eutrophication and climatic warming may additively promote the growth of toxic, rather than non-toxic, populations of
Microcystis, leading to blooms with higher microcystin content. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1568-9883 1878-1470 |
DOI: | 10.1016/j.hal.2009.02.004 |