Conclusions
As extreme events caused by climate change are increasing in frequency
and duration, it is important to develop a mechanistic understanding of
how ecosystems respond to temperature changes. Here we use a trait- and
size-structured model to study the effect of seasonal heatwaves on
plankton organisms. In the model, the plankton functional diversity is
represented by the traits of cell/body size, energy uptake (auto-, mixo-
and heterotrophy) for protists, and the life cycle of copepods with two
feeding modes (active, passive). The model showed that heatwave effects
on biomass, diversity, and community composition are present not only
during the heatwave but for up to six years after the temperature
perturbation. Autumn and summer heatwaves have the most profound
anomalies and longest-lasting effects, followed by winter and spring
heatwaves. Our results indicate that temperature can alter the dominance
of size groups, but temperature alone cannot lead to fundamental changes
in the community size structure and more environmental factors need to
be taken into consideration. In our study, we found a variety of
population and community alterations during the heatwave and different
recovery times to the pre-heatwave state. Two factors drive those
results: the heatwave temperature anomaly compared to the mean seasonal
temperature fluctuation and plankton functional diversity. Communities
have longer recovery times when experiencing seasonal heatwaves with
temperature anomalies outside the pre-heatwave seasonal temperature
fluctuation. Including functional diversity is crucial for exploring
ecosystem changes as protists, active, and passive copepod feeders have
dissimilar responses to the heatwaves, as well as recovery periods. Our
model provides a mechanistic framework with ecological realism, flexible
enough to scale up and down in complexity and test hypotheses for future
studies.