title: Phytoplankton responses to temperature increases are constrained by abiotic conditions and community composition.
abstract: Effects of temperature changes on phytoplankton communities seem to be highly context-specific, but few studies have analyzed whether this context specificity depends on differences in the abiotic conditions or in species composition between studies. We present an experiment that allows disentangling the contribution of abiotic and biotic differences in shaping the response to two aspects of temperature change: permanent increase of mean temperature versus pulse disturbance in form of a heat wave. We used natural communities from six different sites of a floodplain system as well as artificially mixed communities from laboratory cultures and grew both, artificial and natural communities, in water from the six different floodplain lakes (sites). All 12 contexts (2 communities × 6 sites) were first exposed to three different temperature levels (12, 18, 24 °C, respectively) and afterward to temperature pulses (4 °C increase for 7 h day(-1)). Temperature-dependent changes in biomass and community composition depended on the initial composition of phytoplankton communities. Abiotic conditions had a major effect on biomass of phytoplankton communities exposed to different temperature conditions, however, the effect of biotic and abiotic conditions together was even more pronounced. Additionally, phytoplankton community responses to pulse temperature effects depended on the warming history. By disentangling abiotic and biotic effects, our study shows that temperature-dependent effects on phytoplankton communities depend on both, biotic and abiotic constraints.
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Schleusenstrasse 1, 26382, Wilhelmshaven, Germany. Striebel@limnology.eu.|Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Max Emanuel-Strasse 17, 1180, Vienna, Austria. Striebel@limnology.eu.
authors.forename: Maren
authors.initials: M
authors.lastname: Striebel
authors.affiliation: WasserCluster Lunz, Dr. Carl Kupelwieser Promenade 5, 3293, Lunz am See, Austria.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Schabhüttl
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Schleusenstrasse 1, 26382, Wilhelmshaven, Germany.
authors.forename: Dorothee
authors.initials: D
authors.lastname: Hodapp
authors.affiliation: Department of Organismic Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020, Salzburg, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Hingsamer
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Schleusenstrasse 1, 26382, Wilhelmshaven, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Hillebrand
mesh_terms: D018533:Biomass; D060106:Lakes; D010839:Phytoplankton; D013696:Temperature
keywords: Disturbance; Diversity; Nutrients; Origin effects; Phytoplankton