Publication Date:
2020-03-26
Description:
Cell division of the coccolithophore Emiliania huxleyi and other phytoplankton typically becomes entrained
to diel light/dark cycles under laboratory conditions, with division occurring primarily during dark phases and
production occurring during light phases. Under these conditions, increases in cell and biomass concentrations
deviate from exponential functions on time scales 〈 24 h. These deviations lead to significant diel variations in
common measurements of phytoplankton physiology such as cellular quotas of particulate organic and inorganic
carbon (POC, PIC) and their production rates. Being time-dependent, only the temporal mean of the various
values during the day are comparable between experiments. Deviations from exponential growth
furthermore imply that increases in cell and biomass concentrations cannot be expressed by the daily growth
rate μ_{24 h} (typically determined from daily increments in cell concentrations). Consequently, conventional calculations
of production as the product of a cellular quota (e.g., POC quota) and μ_{24 h} are mathematically incorrect.
To account for this, we here describe short-term changes in cell and biomass concentrations of fastdividing,
dilute-batch cultures of E. huxleyi grown under a diel light/dark cycle using linear regression. Based on
the derived models, we present calculations for daily means of cellular quotas and production rates. Conventional
(time-specific) measurements of cellular quotas and production differ from daily means by up to 65% in
our example and, under some circumstances, cause false “effects” of treatments. Intending to reduce errors in
ecophysiological studies, we recommend determining daily means—mathematically or by adjusting the experimental
setup or sampling times appropriately.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
Permalink