TY  - JOUR
A1  - Spijkerman, Elly
A1  - Lukas, Marcus
A1  - Wacker, Alexander
T1  - Ecophysiological strategies for growth under varying light and organic carbon supply in two species of green microalgae differing in their motility
JF  - Phytochemistry : an international journal of plant biochemistry
N2  - Mixing events in stratified lakes result in microalgae being exposed to varying conditions in light and organic carbon concentrations. Stratified lakes consist of an upper illuminated strata and a lower, darker strata where organic carbon accumulates. Therefore, in this contribution we explore the importance of dissolved organic carbon for growth under various light intensities by measuring some ecophysiological adaptations in two green microalgae. We compared the non-motile Chlorella vulgaris with the flagellated Chlamydomonas acidophila under auto-, mixo-, and heterotrophic growth conditions. In both algae the maximum photosynthetic and growth rates were highest under mixotrophy, and both algae appeared inhibited in their phosphorus acquisition under heterotrophy. Heterotrophic conditions provoked the largest differences as C. vulgaris produced chlorophyll a in darkness and grew as well as in autotrophic conditions, whereas Chl. acidophila bleached and could not grow heterotrophically. Although the fatty acid composition of both phytoplankton species differed, both species reacted in a similar way to changes in their growth conditions, mainly by a decrease of C18:3n-3 and an increase of C18:1n-9 from auto- to heterotrophic conditions. The two contrasting responses within the group of green microalgae suggest that dissolved organic carbon has a high deterministic potential to explain the survival and behaviour of green algae in the deeper strata of lakes.
KW  - Chlamydomonas acidophila
KW  - Chlorella vulgaris
KW  - Chlorophyceae
KW  - Ecophysiology on freshwater phytoplankton
KW  - Glucose
KW  - Mixotrophy
KW  - Osmotrophy
KW  - Heterotrophy
KW  - Photosynthesis
KW  - Fatty acids
Y1  - 2017
U6  - https://doi.org/10.1016/j.phytochem.2017.08.018
SN  - 0031-9422
SN  - 1873-3700
VL  - 144
SP  - 43
EP  - 51
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Massie, Thomas Michael
A1  - Ryabov, Alexei
A1  - Blasius, Bernd
A1  - Weithoff, Guntram
A1  - Gaedke, Ursula
T1  - Complex transient dynamics of stage-structured populations in response to environmental changes
JF  - The American naturalist : a bi-monthly journal devoted to the advancement and correlation of the biological sciences
N2  - Stage structures of populations can have a profound influence on their dynamics. However, not much is known about the transient dynamics that follow a disturbance in such systems. Here we combined chemostat experiments with dynamical modeling to study the response of the phytoplankton species Chlorella vulgaris to press perturbations. From an initially stable steady state, we altered either the concentration or dilution rate of a growth-limiting resource. This disturbance induced a complex transient response-characterized by the possible onset of oscillations-before population numbers relaxed to a new steady state. Thus, cell numbers could initially change in the opposite direction of the long-term change. We present quantitative indexes to characterize the transients and to show that the dynamic response is dependent on the degree of synchronization among life stages, which itself depends on the state of the population before perturbation. That is, we show how identical future steady states can be approached via different transients depending on the initial population structure. Our experimental results are supported by a size-structured model that accounts for interplay between cell-cycle and population-level processes and that includes resource-dependent variability in cell size. Our results should be relevant to other populations with a stage structure including organisms of higher order.
KW  - chemostat experiments
KW  - Chlorella vulgaris
KW  - environmental changes
KW  - population dynamics
KW  - stage structure
KW  - transient dynamics
Y1  - 2013
U6  - https://doi.org/10.1086/670590
SN  - 0003-0147
SN  - 1537-5323
VL  - 182
IS  - 1
SP  - 103
EP  - 119
PB  - Univ. of Chicago Press
CY  - Chicago
ER  -