Marine and freshwater planktonic ciliates differ in their thermal performance

Predicting the performance of aquatic organisms in a future warmer climate
depends critically on understanding how current temperature regimes affect
the organisms’ growth rates. Using a meta-analysis for published
experimental data, we calculated the activation energy (Ea) to
parameterize the thermal sensitivity of marine and freshwater ciliates,
major players in marine and freshwater food webs. We hypothesized that
their growth rates increase with temperature but that ciliates dwelling in
the immense, thermally stable ocean are closely adapted to their ambient
temperature and have lower Ea than ciliates living in smaller, thermally
more variable freshwater environments. The Ea was in the range known from
other taxa but significantly lower for marine ciliates (0.390 ± 0.105 eV)
than for freshwater ciliates (0.633 ± 0.060 eV), supporting our
hypothesis. Accordingly, models aiming to predict the ciliate response to
increasing water temperature should apply the environment-specific
activation energies provided in this study.