Data from: An affordable and reliable assessment of aquatic decomposition: tailoring the Tea Bag Index to surface waters

Litter decomposition is a vital part of the global carbon cycle as it
determines not only the amount of carbon to be sequestered, but also how
fast carbon re-enters the cycle. Freshwater systems play an active role in
the carbon cycle as it receives, and decomposes, terrestrial litter
material alongside decomposing aquatic plant litter. Decomposition of
organic matter in the aquatic environment is directly controlled by water
temperature and nutrient availability, which are continuously affected by
global change. We adapted the Tea Bag Index (TBI), a highly standardized
methodology for determining soil decomposition, for lakes by incorporating
a leaching factor. By placing Lipton pyramid tea bags in the aquatic
environment for 3 hours, we quantified the period of intense leaching
which usually takes place prior to litter (tea) decomposition. Standard
TBI methodology was followed after this step to determine how fast
decomposition takes place (decomposition rate, k1) and how much of the
material cannot be broken down and is thus sequestered (stabilization
factor, S). A Citizen Science project was organized to test the aquatic
TBI in 40 European lakes located in four climate zones, ranging from
oligotrophic to hypereutrophic systems. We expected that warmer and/or
eutrophic lakes would have a higher decomposition rate and a more
efficient microbial community resulting in less tea material to be
sequestered. The overall high decomposition rates (k1) found confirm the
active role lakes play in the global carbon cycle. Across climate regions
the lakes in the warmer temperate zone displayed a higher decomposition
rate (k1) compared to the colder lakes in the continental and polar zones.
Across trophic states, decomposition rates were higher in eutrophic lakes
compared to oligotrophic lakes. Additionally, the eutrophic lakes showed a
higher stabilization (S), thus a less efficient microbial community,
compared to the oligotrophic lakes, although the variation within this
group was high. Our results clearly show that the TBI can be used to
adequately assess the decomposition process in aquatic systems. Using
“alien standard litter” such as tea provides a powerful way to compare
decomposition across climates, trophic states and ecosystems. By providing
standardized protocols, a website, as well as face to face meetings, we
also showed that collecting scientifically relevant data can go hand in
hand with increasing scientific and environmental literacy in
participants. Gathering process-based information about lake ecosystems
gives managers the best tools to anticipate and react to future global
change. Furthermore, combining this process-based information with citizen
science, thus outreach, is in complete agreement with the Water Framework
Directive goals as set in 2010.