Data from: Warming enhances sedimentation and decomposition of organic carbon in shallow macrophyte-dominated systems with zero net effect on carbon burial

Temperatures have been rising throughout recent decades and are predicted
to rise further in the coming century. Global warming affects carbon
cycling in freshwater ecosystems, which both emit and bury substantial
amounts of carbon on a global scale. Currently, most studies focus on the
effect of warming on overall carbon emissions from freshwater ecosystems,
while net effects on carbon budgets may strongly depend on burial in
sediments. Here, we tested whether year‐round warming increases the
production, sedimentation, or decomposition of particulate organic carbon
and eventually alters the carbon burial in a typical shallow freshwater
system. We performed an indoor experiment in eight mesocosms dominated by
the common submerged aquatic plant Myriophyllum spicatum testing two
temperature treatments: a temperate seasonal temperature control and a
warmed (+4°C) treatment (n = 4). During a full experimental year, the
carbon stock in plant biomass, dissolved organic carbon in the water
column, sedimented organic matter, and decomposition of plant detritus
were measured. Our results showed that year‐round warming nearly doubled
the final carbon stock in plant biomass from 6.9 ± 1.1 g C in the control
treatment to 12.8 ± 0.6 g C (mean ± SE), mainly due to a prolonged growing
season in autumn. DOC concentrations did not differ between the
treatments, but organic carbon sedimentation increased by 60% from 96 ±
9.6 to 152 ± 16 g C m−2 year−1 (mean ± SE) from control to warm
treatments. Enhanced decomposition of plant detritus in the warm
treatment, however, compensated for the increased sedimentation. As a
result, net carbon burial was 40 ± 5.7 g C m−2 year−1 in both temperature
treatments when fluxes were combined into a carbon budget model. These
results indicate that warming can increase the turnover of organic carbon
in shallow macrophyte‐dominated systems, while not necessarily affecting
net carbon burial on a system scale.