Data from: The effect of elevated CO2 on growth and competition in experimental phytoplankton communities

We report an experiment designed to identify the effect of elevated CO2 on
species of phytoplankton in a simple laboratory system. Major taxa of
phytoplankton differ in their ability to take up CO2, which might lead to
predictable changes in the growth rate of species and thereby shifts in
the composition of phytoplankton communities in response to rising CO2.
Six species of phytoplankton belonging to three major taxa (cyanobacteria,
diatoms and chlorophytes) were cultured in atmospheres whose CO2
concentration was gradually increased from ambient levels to 1000 parts
per million over about 100 generations and then maintained for a further
200 generations at elevated CO2. The experimental design allowed us to
trace a predictive sequence, from physiological features to the growth
response of species to elevated CO2 in pure culture, from the growth
response in pure culture to competitive ability in pairwise mixtures and
from pairwise competitive ability to shifts in the relative abundance of
species in the full community of all six species. CO2 altered the dynamics
of growth in a fashion consistent with known differences among major taxa
in their ability to take up and use CO2. This pure-culture response was
partly successful in predicting the outcome of competition in pairwise
mixtures, especially the enhanced competitive ability of chlorophytes
relative to cyanobacteria, although generally statistical support was
weak. The competitive response in pairwise mixtures was a good predictor
of changes in competitive ability in the full community. Hence, there is a
potential for forging a logical chain of inferences for predicting how
phytoplankton communities will respond to elevated CO2. Clearly further
extensive experiments will be required to validate this approach in the
greater complexity found in diverse communities and environments of
natural systems.