Effect of temperature on diatom volume, growth rate, and carbon and nitrogen content: Reconsidering some paradigms

We examined the response of diatoms to naturally experienced temperatures and tested these hypotheses: (1) diatoms follow the rule that organism size decreases with increasing temperature; (2) diatom growth rate follows a Q(10)-like response; (3) diatom carbon (C) and nitrogen (N) content per unit volume (V) decrease with increasing size, and changes in temperature affect this relationship and (4) diatom C:V s is the same as that of other phytoplankton. We also present, as predictive equations, relationships between (1) growth rate, temperature, and size; (2) C content and V: and (3) N content and V. Eight diatoms and two flagellates were acclimated for approximately five generations and grown for approximately five more generations at five temperatures (9-25 degreesC) on a 14:10 light: dark cycle at similar to 50 mu mol photons m(-2) s(-1). Growth rate, cell V, and C and N content per cell were measured relationships between these parameters and temperature were determined. For five diatoms and both flagellates, cell V decreased with increasing temperature; cells decrease by similar to4% of their mean V per degreesC. Growth rate appeared to increase linearly with temperature in all cases. The literature suggests that a linear response is the rule, not the exception. Temperature did not significantly affect C or N per V of diatom species. When all diatoms were considered. both C and N per V decreased with increasing cell sized our data support the argument that diatoms differ from other protists in this respect, but the difference is less pronounced than stated in previous reports.