Changes in Stoichiometry, Cellular RNA, and Alkaline Phosphatase Activity ofChlamydomonasin Response to Temperature and Nutrients.
Phytoplankton may respond both to elevated temperatures and reduced nutrients by changing their cellular stoichiometry and cell sizes. Since increased temperatures often cause increased thermal stratification and reduced vertical flux of nutrients into the mixed zone, it is difficult to disentangle these drivers in nature. In this study, we used a factorial design with high and low levels of phosphorus (P) and high and low temperature to assess responses in cellular stoichiometry, levels of RNA, and alkaline phosphatase activity (APA) in the chlorophyteChlamydomonas reinhardtii.Growth rate, C:P, C:N, N:P, RNA, and APA all responded primarily to P treatment, but except for N:P and APA, also temperature contributed significantly. For RNA, the contribution from temperature was particularly strong with higher cellular levels of RNA at low temperatures, suggesting a compensatory allocation to ribosomes to maintain protein synthesis and growth. These experiments suggest that although P-limitation is the major determinant of growth rate and cellular stoichiometry, there are pronounced effects of temperature also via interaction with P. At the ecosystem level, nutrients and temperature will thus interact, but temperatures would likely exert a stronger impact on these phytoplankton traits indirectly via its force on stratification regimes and vertical nutrient fluxes.
Aquatic Ecology and Toxicology, Department of Biosciences, University of Oslo Oslo, Norway.
Dag O
DO
Hessen
Aquatic Ecology and Toxicology, Department of Biosciences, University of Oslo Oslo, Norway.
Ola T
OT
Hafslund
Aquatic Ecology and Toxicology, Department of Biosciences, University of Oslo Oslo, Norway.
Tom
T
Andersen
Aquatic Ecology and Toxicology, Department of Biosciences, University of Oslo Oslo, Norway.
Catharina
C
Broch
Aquatic Ecology and Toxicology, Department of Biosciences, University of Oslo Oslo, Norway.
Nita K
NK
Shala
Aquatic Ecology and Toxicology, Department of Biosciences, University of Oslo Oslo, Norway.
Marcin W
MW
Wojewodzic
RNA; alkaline phosphatase; cell size; growth; phosphorus; phytoplankton; stoichiometry; temperature