Laboratory of Ecology and Physiology of Phytoplankton, Department of Plant Biology, University of Rio de Janeiro State, Rua São Francisco Xavier, 524 - PHLC Sala 511a, Rio de Janeiro, 20550-900, Brazil.
Federal Institute of Rio de Janeiro, Avenida Washington Luís, Pendotiba, Niterói, Rio de Janeiro, 24310-000, Brazil.
Microb Ecol. 2020 Jan;79(1):1-11. doi: 10.1007/s00248-019-01384-w. Epub 2019 May 20.
Temperature increase may influence competition among phytoplankton species, potentially intensifying cyanobacteria blooms that can be favored by direct and indirect effects of temperature. In this study, we aimed to clarify how cyanobacteria can be favored by the direct effects of increased temperature compared to diatoms and chlorophytes. Strains of the most representative species of a eutrophic coastal lagoon (Microcystis aeruginosa, Planktothrix agardhii, Desmodesmus communis, and Cyclotella meneghiniana) were used to test the hypothesis that cyanobacteria would be favored by the direct effect of temperature increase. First, we evaluated the effect of temperature increase on growth in monocultures (batch and chemostats) at 25 and 30 °C and after in mixed cultures (chemostats). In batch monocultures, the cyanobacteria showed higher growth rates in 30 °C than in 25 °C. However, in continuous culture experiments (chemostats), growth rates of M. aeruginosa and P. agardhii were not affected by temperature, but the strains showed higher biovolume in steady-state with the temperature increase. In continuous mixed cultures, M. aeruginosa was always dominant and C. meneghiniana was excluded, regardless of temperature tested. D. communis was able to coexist with lower biomass. This study shows that rising temperatures can be detrimental to diatoms, even for a tropical strain. Although some studies indicate that the dominance of cyanobacteria in warmer climates may be due to the indirect effect of warming that will promote physical conditions in the environment more favorable to cyanobacteria, the outcomes of mixed cultures demonstrate that the direct effect of temperature can also favor the dominance of cyanobacteria.
温度升高可能会影响浮游植物物种间的竞争，从而加剧蓝藻水华，这种水华可能受到温度的直接和间接影响。在这项研究中，我们旨在阐明与硅藻和绿藻相比，蓝藻如何受到温度升高的直接影响而变得更具优势。本研究采用富营养化沿海泻湖最具代表性物种的菌株（铜绿微囊藻、束丝藻、普通小球藻和梅尼小环藻）来验证温度升高的直接影响有利于蓝藻的假说。首先，我们评估了在 25 和 30°C 的单培养（批式和恒化器）和混合培养（恒化器）中温度升高对生长的影响。在批式单培养中，蓝藻在 30°C 下的生长速率高于 25°C。然而，在连续培养实验（恒化器）中，铜绿微囊藻和束丝藻的生长速率不受温度影响，但随着温度升高，它们的生物量在稳定状态下更高。在连续混合培养中，铜绿微囊藻始终占主导地位，梅尼小环藻被排除，无论测试的温度如何。普通小球藻能够以较低的生物量共存。本研究表明，温度升高对硅藻，甚至是热带菌株都是有害的。尽管一些研究表明，在温暖气候下蓝藻占优势可能是由于变暖的间接影响会促进环境中更有利于蓝藻的物理条件，但混合培养的结果表明，温度的直接影响也有利于蓝藻的优势地位。
