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Simulated heat waves promote the growth but suppress the N2 fixation rates of Dolichospermum spp. and cyanobacterial communities in temperate lakes.
- Source :
-
Ecological Indicators . Mar2023, Vol. 147, pN.PAG-N.PAG. 1p. - Publication Year :
- 2023
-
Abstract
- [Display omitted] • Subtropical Dolichospermum were better adapted to heat waves than subpolar isolates. • Nitrogen loading significantly increased cyanobacterial growth rates. • Heat waves significantly increases cyanobacterial growth rates. • Rising temperatures representing heat waves significantly suppress N 2 fixation. • Heat wave induced suppression of diazotrophy could exacerbate N limitation in lakes. The intensity and duration of heat waves are expected to increase this century, occurrences considered favorable for harmful, bloom-forming freshwater cyanobacteria. Dinitrogen (N 2) fixation is a major component of nitrogen cycling in freshwater systems, yet little is known with respect to how diazotrophic (N 2 fixing) cyanobacteria respond to heat waves. Here, we quantified the effects of elevated temperature and fixed N enrichment on the growth and N 2 fixation rates of Dolichospermum isolates from differing latitudes and cyanobacterial communities in four lakes across New York state, USA, during the summer and early fall. In culture experiments, temperatures ≥ 26℃ significantly reduced maximum growth rates of the sub-polar Dolichospermum strains from Finland relative to those grown at 20 − 25℃, while a strain of Dolichospermum isolated from subtropical Australia grew significantly faster at 20 − 30℃ compared to cooler temperatures. All strains, however, exhibited significantly lower N 2 fixation rates at higher temperatures (29 − 30℃) relative to lower temperatures (13-26℃). During ecosystem-based experiments with cyanobacterial communities comprised of Nostocales and other diazotrophic cyanobacteria, short-term (3–4 day) exposures to elevated temperatures mimicking heat waves (+3-6℃; 27-31℃) and/or N (NH 4 +) enrichment caused a significant increase in cyanobacterial net growth rates but also caused a significant decline in N 2 fixation rates. Collectively, results indicate that while heat waves and fixed N loading can promote cyanobacterial communities, they also suppress diazotrophy, which is generally regarded as a significant component of nitrogen cycling in eutrophic freshwater systems. Such reductions in N 2 fixation would promote or intensify N limitation of primary production in lakes during the summer, an outcome that would be exacerbated under future warming scenarios. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 1470160X
- Volume :
- 147
- Database :
- Academic Search Index
- Journal :
- Ecological Indicators
- Publication Type :
- Academic Journal
- Accession number :
- 162027659
- Full Text :
- https://doi.org/10.1016/j.ecolind.2023.109983