Leaf litter processing is one major pathway of the global organic carbon cycle. During this process, a variety of small reactive organic compounds are released and transported to the aquatic environment, and
may directly impact aquatic organisms as natural xenobiotics. We hypothesize that different forest stockings produce different leachate qualities, which in turn, stress the aquatic communities and, eventually,
separate sensitive from tolerant species. Particularly, leachates from coniferous trees are suspected to
have strongly adverse impacts on sensitive species. We exposed individuals of a clone of the model
organism, Moina macrocopa, to comparable concentrations (approximately 2 mM) of litter leachates of
Norway spruce, Picea abies, Colorado blue spruce, Picea pungens, black poplar, Populus nigra, and sessile
oak, Quercus petraea. The animals were fed ad libitum. The following life trait variables were recorded:
growth, lifespan, and lifetime offspring. To identify, whether or not exposure to litter leachates provokes
an internal oxidative stress in the exposed animals we measured the superoxide anion radical scavenging
capacity via photoluminescence. Except of P. abies, exposure to the leachates reduced this antioxidant
capacity by approximately 50%. Leachate exposures, except that of Quercus, increased body size and
extended lifespan; furthermore, particularly the leachates of both Picea species significantly increased
the offspring numbers. This unexpected behavior of exposed Moina may be based on food supplements
(e.g., high carbohydrate contents) in the leachates or on yet to be identified regulatory pathways of
energy allocation. Overall, our results suggest that the potentially adverse effects of litter leachates can
be overruled by either bacterial-growth supporting fractions in the leachates or an internal compensation
mechanism in the Moina individuals.