title: What drives the distribution of the bloom-forming cyanobacteria Planktothrix agardhii and Cylindrospermopsis raciborskii?
abstract: The cyanobacteria Planktothrix agardhii and Cylindrospermopsis raciborskii are bloom-forming species common in eutrophic freshwaters. These filamentous species share certain physiological traits which imply that they might flourish under similar environmental conditions. We compared the distribution of the two species in a large database (940 samples) covering different climatic regions and the Northern and Southern hemispheres, and carried out laboratory experiments to compare their morphological and physiological responses. The environmental ranges of the two species overlapped with respect to temperature, light and total phosphorus (TP); however, they responded differently to environmental gradients; C. raciborskii biovolume changed gradually while P. agardhii shifted sharply from being highly dominated to a rare component of the phytoplankton. As expected, P. agardhii dominates the phytoplankton with high TP and low light availability conditions. Contrary to predictions, C. raciborskii succeeded in all climates and at temperatures as low as 11 °C. Cylindrospermopsis raciborskii had higher phenotypic plasticity than P. agardhii in terms of pigments, individual size and growth rates. We conclude that the phenotypic plasticity of C. raciborskii could explain its ongoing expansion to temperate latitudes and suggest its future predominance under predicted climate-change scenarios.
authors.affiliation: Grupo de Ecología y Fisiología de Fitoplancton, Sección Limnología, Instituto de Ecología y Ciencias Ambientales, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay. sbon@fcien.edu.uy
authors.forename: Sylvia
authors.initials: S
authors.lastname: Bonilla
authors.forename: Luis
authors.initials: L
authors.lastname: Aubriot
authors.forename: Maria Carolina S
authors.initials: MC
authors.lastname: Soares
authors.forename: Mauricio
authors.initials: M
authors.lastname: González-Piana
authors.forename: Amelia
authors.initials: A
authors.lastname: Fabre
authors.forename: Vera L M
authors.initials: VL
authors.lastname: Huszar
authors.forename: Miquel
authors.initials: M
authors.lastname: Lürling
authors.forename: Dermot
authors.initials: D
authors.lastname: Antoniades
authors.forename: Judit
authors.initials: J
authors.lastname: Padisák
authors.forename: Carla
authors.initials: C
authors.lastname: Kruk
mesh_terms: D002980:Climate; D000458:Cyanobacteria / Q000254:growth & development* / Q000502:physiology; D046891:Cylindrospermopsis / Q000254:growth & development / Q000502:physiology; D004777:Environment; D005068:Eutrophication; D005618:Fresh Water / Q000382:microbiology*; D010839:Phytoplankton / Q000254:growth & development / Q000502:physiology; D013696:Temperature