Data from: Investigating the effects of thermal variability and heatwaves on pond zooplankton communities and physiological traits

To understand the impacts of climate change, we must understand the
consequences of multiple and interacting timescales of temperature change.
While much is known about rising mean temperatures, less is understood
about the influence of projected thermal variability and extreme events
like heatwaves on biological communities. This study investigates the
interaction of short-term (experimental) and long-term (historic) thermal
variability with heatwaves on zooplankton communities and physiological
traits. We performed a fully factorial mesocosm experiment with three
factors: (1) historic thermal variation (four source ponds with similar
average temperature but different daily thermal ranges including 3.7°C,
5.9°C, 9.1°C, and 10.7°C); (2) experimental thermal variation (insulated
and non-insulated tanks); and (3) a 4-day heatwave treatment (+3.5°C)
halfway through the experiment. We sampled the zooplankton community
throughout the experiment and assayed the upper thermal limit (CTmax) and
metabolic rate of Daphnia
dentifera and Leptodiaptomus
signicauda immediately before and after the heatwave. Zooplankton
community composition responded minimally to thermal variability and the
heatwave. For both species, CTmax response to the heatwave varied by
experimental thermal variability, increasing in individuals from
low-variability tanks and decreasing in individuals from high-variability
tanks. Metabolic rate did not vary significantly by any of the treatments.
D. dentifera and L. signicauda's upper thermal
limit seems to be unaffected by their historic thermal history, while
their CTmax response to a heatwave seems to rely only on their short-term
thermal variability history. Metabolic rate, on the other hand, is
unaffected by thermal history or heatwaves of this magnitude. In spite of
the physiological responses at the individual level, zooplankton community
structure seems to be buffered and overall unaffected by heatwaves and
thermal variability at this magnitude. Our experiment provides new insight
on the effects of thermal variability at both short- and long-term scales
combined with an acute heatwave to understand the effects of a changing
climate in a more realistic manner. The data supports that individuals
from recently thermally stable backgrounds may be better equipped to
positively respond physiologically to heatwaves and zooplankton community
structure in this system could be unaffected by warming at this magnitude.