Data from: Long-term stoichiometry and fates highlight animal egestion as nutrient repackaging, not recycling, in aquatic ecosystems

1. Animal defecation, or egestion, is a pronounced transformation of
organic matter in many ecosystems. However, because egesta have been
presumed recalcitrant and low-nutrient, their significance and variability
as an animal nutrient flux in aquatic settings - especially relative to
mineralization via excretion - are poorly known. 2. We compared carbon
(C), nitrogen (N), and phosphorus (P) dynamics over short- to long-term
(up to 107 days) microbial decomposition of egesta from the aquatic
shredders Allocapnia spp., Lirceus spp., and Tipula spp. fed low- or
high-P content Platanus occidentalis litter to investigate roles of egesta
in aquatic nutrient dynamics. 3. Tipula produced N- and P-deplete egesta
of higher N:P compared to Lirceus and Allocapnia, and high-P diets
increased egesta P content compared to low-P diets. Despite measurable C
losses to decomposition, these differences in nutrient content persisted
through decomposition, showing diet and species control both immediate and
long-term properties of egested particles. 4. Egesta switched between
uptake and release of dissolved phosphorus and ammonium during
decomposition, and exhibited consistent net N uptake as nitrate-nitrite.
Across species and diets, lower N:P egesta tended to exhibit greater
uptake of dissolved inorganic N, suggesting P enrichment of egesta drove
stronger dissolved N demand by decomposer microbes. 5. Shredder egesta
exhibit stable nutrient contents long-term and, counter to assumptions
that they are negligible or minor net sources, can be strong, extended
sinks of dissolved inorganic nutrients. Future studies should consider
contrasts between animal nutrient fluxes as excretion, which facilitates
nutrient recycling via mineralization, versus egestion, which slows
nutrient recycling via organic nutrient repackaging and can create sinks
of dissolved nutrients.