Data from: Stoichiometric imbalances between detritus and detritivores are related to shifts in ecosystem functioning

How are resource consumption and growth rates of litter-consuming
detritivores affected by imbalances between consumer and litter C:N:P
ratios? To address this question, we offered leaf litter as food to three
aquatic detritivore species, which represent a gradient of increasing body
N:P ratios: a crustacean, a caddisfly and a stonefly. The detritivores
were placed in microcosms and submerged in a natural stream. Four
contrasting leaf species were offered, both singly and in two-species
mixtures, to obtain different levels of stoichiometric imbalance between
the resources and their consumers. The results suggest that detritivore
growth was constrained by N rather than C or P, even though 1) the N:P
ratios of the consumers’ body tissue was relatively low and 2) microbial
leaf conditioning during the experiment reduced the N:P imbalance between
detritivores and leaf litter. This surprisingly consistent N limitation
may be a consequence of cumulative N-demand arising from the production of
N-rich chitin in the exoskeletons of all three consumer species, which is
lost during regular moults, in addition to N-demand for silk production by
the caddisfly. These N requirements are not commonly quantified in
stoichiometric analyses of arthropod consumers. There was no evidence for
compensatory feeding, but when offered mixed-species litter varying in
C:N:P ratios, detritivores consumed more of the litter species showing the
highest N:P and lowest C:N ratio, accelerating the mass loss of the
preferred leaf species in the litter mixture. These results show that
imbalances in consumer–resource stoichiometry can have contrasting effects
on coupled processes, highlighting a challenge in developing a mechanistic
understanding of the role of stoichiometry in regulating ecosystem
processes such as leaf litter decomposition.