title: Interaction Effects of Light, Temperature and Nutrient Limitations (N, P and Si) on Growth, Stoichiometry and Photosynthetic Parameters of the Cold-Water Diatom Chaetoceros wighamii.
abstract: Light (20-450 μmol photons m(-2) s(-1)), temperature (3-11 °C) and inorganic nutrient composition (nutrient replete and N, P and Si limitation) were manipulated to study their combined influence on growth, stoichiometry (C:N:P:Chl a) and primary production of the cold water diatom Chaetoceros wighamii. During exponential growth, the maximum growth rate (~0.8 d(-1)) was observed at high temperature and light; at 3 °C the growth rate was ~30% lower under similar light conditions. The interaction effect of light and temperature were clearly visible from growth and cellular stoichiometry. The average C:N:P molar ratio was 80:13:1 during exponential growth, but the range, due to different light acclimation, was widest at the lowest temperature, reaching very low C:P (~50) and N:P ratios (~8) at low light and temperature. The C:Chl a ratio had also a wider range at the lowest temperature during exponential growth, ranging 16-48 (weight ratio) at 3 °C compared with 17-33 at 11 °C. During exponential growth, there was no clear trend in the Chl a normalized, initial slope (α*) of the photosynthesis-irradiance (PE) curve, but the maximum photosynthetic production (P(m)) was highest for cultures acclimated to the highest light and temperature. During the stationary growth phase, the stoichiometric relationship depended on the limiting nutrient, but with generally increasing C:N:P ratio. The average photosynthetic quotient (PQ) during exponential growth was 1.26 but decreased to <1 under nutrient and light limitation, probably due to photorespiration. The results clearly demonstrate that there are interaction effects between light, temperature and nutrient limitation, and the data suggests greater variability of key parameters at low temperature. Understanding these dynamics will be important for improving models of aquatic primary production and biogeochemical cycles in a warming climate.
authors.affiliation: Finnish Environment Institute, Marine Research Centre, PO Box 140, Helsinki, Finland; Tvärminne Zoological Station, University of Helsinki, J.A. Palménin tie 260, Hanko, Finland.
authors.forename: Kristian
authors.initials: K
authors.lastname: Spilling
authors.affiliation: Finnish Environment Institute, Marine Research Centre, PO Box 140, Helsinki, Finland.
authors.forename: Pasi
authors.initials: P
authors.lastname: Ylöstalo
authors.affiliation: Finnish Environment Institute, Marine Research Centre, PO Box 140, Helsinki, Finland; Plymouth Marine Laboratory, Plymouth, United Kingdom.
authors.forename: Stefan
authors.initials: S
authors.lastname: Simis
authors.affiliation: Finnish Environment Institute, Marine Research Centre, PO Box 140, Helsinki, Finland.
authors.forename: Jukka
authors.initials: J
authors.lastname: Seppälä
mesh_terms: D000064:Acclimatization; D002244:Carbon / Q000172:deficiency / Q000494:pharmacology; D002734:Chlorophyll / Q000819:agonists / Q000096:biosynthesis; D000077194:Chlorophyll A; D003080:Cold Temperature; D017377:Diatoms / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D008027:Light; D009584:Nitrogen / Q000172:deficiency / Q000494:pharmacology*; D010758:Phosphorus / Q000172:deficiency / Q000494:pharmacology*; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects*; D012825:Silicon / Q000172:deficiency / Q000494:pharmacology*
chemical_list: D002734:Chlorophyll; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen; D000077194:Chlorophyll A; D012825:Silicon