title: Response of microalgae to elevated CO2 and temperature: impact of climate change on freshwater ecosystems.
abstract: To estimate the combined effects of elevated CO2 and temperature on microalgae, three typical and worldwide freshwater species, the green alga Scenedesmus acuminatus, the diatom Cyclotella meneghiniana, and the cyanobacterium Microcystis aeruginosa, as well as mixes of these three species were continuously cultured in controlled environment chambers with CO2 at 390 and 1000 ppm and temperatures of 20, 25, and 30 °C. CO2 and temperature significantly affected the production of microalgae. The cell productivity increased under elevated CO2 and temperature. Although the green alga dominated in the mixed culture within all CO2 and temperature conditions, rising temperature and CO2 intensified the competition of the cyanobacterium with other microalgae. CO2 affected the extracellular polymeric substances (EPS) characteristics of the green alga and the cyanobacterium. Elevated CO2 induced the generation of humic substances in the EPS fractions of the green alga, the cyanobacterium, and the mixed culture. The extracellular carbohydrates of the diatom and the extracellular proteins of the cyanobacterium increased with elevated CO2 and temperature, while the extracellular carbohydrates and proteins of the green alga and the mixes increased under elevated CO2 and temperature. There were synergistic effects of CO2 and temperature on the productivity and the EPS of microalgae. Climate change related CO2 and temperature increases will promote autochthonous organic carbon production in aquatic ecosystems and facilitate the proliferation of cyanobacteria, which potentially changes the carbon cycling and undermines the functioning of ecosystems.
authors.affiliation: School of Urban Construction and Environmental Engineering, Chongqing University, Shabei Road 83, Chongqing, 400044, People's Republic of China.|Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Aoba Aramaki 6-6-06, Sendai, 980-8579, Japan.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: School of Environment, Nanjing Normal University, Wenyuan Road 1, Xianlin University District, Nanjing, 210023, People's Republic of China. lixuweixiao@hotmail.com.|Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Aoba Aramaki 6-6-06, Sendai, 980-8579, Japan. lixuweixiao@hotmail.com.
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Aoba Aramaki 6-6-06, Sendai, 980-8579, Japan.
authors.forename: Megumu
authors.initials: M
authors.lastname: Fujibayashi
authors.affiliation: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Aoba Aramaki 6-6-06, Sendai, 980-8579, Japan.
authors.forename: Qigui
authors.initials: Q
authors.lastname: Niu
authors.affiliation: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Aoba Aramaki 6-6-06, Sendai, 980-8579, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Tanaka
authors.affiliation: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Aoba Aramaki 6-6-06, Sendai, 980-8579, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Nishimura
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001704:Biopolymers / Q000378:metabolism; D050260:Carbohydrate Metabolism / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology*; D057231:Climate Change; D017377:Diatoms / Q000187:drug effects* / Q000378:metabolism; D017753:Ecosystem; D005618:Fresh Water; D006812:Humic Substances; D058086:Microalgae / Q000187:drug effects* / Q000378:metabolism; D046931:Microcystis / Q000187:drug effects* / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D044444:Scenedesmus / Q000187:drug effects* / Q000378:metabolism; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D006812:Humic Substances; D010940:Plant Proteins; D002245:Carbon Dioxide
keywords: Algae; Aquatic ecology; Carbon dioxide; Climate change; Cyanobacterium; Drinking water; Organic matter